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Sample records for volcanic conduit processes

  1. Stability of volcanic conduits: insights from magma ascent modelling and possible consequences on eruptive dynamics

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    Aravena, Alvaro; de'Michieli Vitturi, Mattia; Cioni, Raffaello; Neri, Augusto

    2017-04-01

    Geological evidences of changes in volcanic conduit geometry (i.e. erosive processes) are common in the volcanic record, as revealed by the occurrence of lithic fragments in most pyroclastic deposits. However, the controlling factors of conduit enlargement mechanisms are still partially unclear, as well as the influence of conduit geometry in the eruptive dynamics. Despite physical models have been systematically used for studying volcanic conduits, their mechanical stability has been poorly addressed. In order to study the mechanical stability of volcanic conduits during explosive eruptions, we present a 1D steady-state model which considers the main processes experimented by ascending magmas, such as crystallization, drag forces, fragmentation, outgassing and degassing; and the application of the Mogi-Coulomb collapse criterion, using a set of constitutive equations for studying typical cases of rhyolitic and trachytic explosive volcanism. From our results emerge that conduit stability is mainly controlled by magma rheology and conduit dimensions. Indeed, in order to be stable, feeding conduits of rhyolitic eruptions need larger radii respect to their trachytic counterparts, which is manifested in the higher eruption rates usually observed in rhyolitic explosive eruptions, as confirmed by a small compilation of global data. Additionally, for both magma compositions, we estimated a minimum magma flux for developing stable conduits (˜3ṡ106 kg/s for trachytic magmas and ˜8ṡ107 kg/s for rhyolitic magmas), which is consistent with the unsteady character commonly observed in low-mass flux events (e.g. sub-Plinian eruptions), which would be produced by episodic collapse events of the volcanic conduit, opposite to the mainly stationary high-mass flux events (e.g. Plinian eruptions), characterized by stable conduits. For a given magma composition, a minimum radius for reaching stable conditions can be computed, as a function of inlet overpressure and water content

  2. Oxidation of shallow conduit magma: Insight from μ-XANES analysis on volcanic ash particle

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    Miwa, T.; Ishibashi, H.; Iguchi, M.

    2014-12-01

    Redox state of magma is important to understand dynamics of volcanic eruptions because magma properties such as composition of degassed volatiles, stability field of minerals, and rheology of magma depend on redox state. To evaluate redox state of magma, Fe3+/ΣFe ratio [= Fe3+/( Fe3++ Fe2+)] of volcanic glass has been measured non-destructively by Fe-K edge μ-XANES (micro X-ray Absorption Near Edge Structure) spectroscopy (e.g., Cottrell and Kelly, 2011). We performed textural, compositional, and Fe-K edge μ-XANES analyses on volcanic ash to infer oxidation process of magma at shallow conduit during eruption at Bromo Volcano, Indonesia. The volcanic ash particles were collected in 24th March 2011 by real-time sampling from ongoing activity. The activity was characterized by strombolian eruption showing magma head ascended to near the ground surface. The ash sample contains two type of volcanic glasses named as Brown and Black glasses (BrG and BlG), based on their color. Textual analysis shows microlite crystallinities are same in the two type of glasses, ranging from 0 to 3 vol.%. EPMA analyses show that all of the glasses have almost identical andesitic composition with SiO2 = 60 wt.%. In contrast, Fe-K edge μ-XANES spectra with the analytical method by Ishibashi et al. (in prep) demonstrate that BrG (Fe3+/ΣFe = 0.20-0.26) is more oxidized than BlG (Fe3+/ΣFe = 0.32-0.60). From combination of the glass composition, the measured Fe3+/ΣFe ratio and 1060 degree C of temperature (Kress and Carmichael, 1991), the oxygen fugacities are estimated to be NNO and NNO+4 for BrG and BlG, respectively. The volcanic glasses preserve syn-eruptive physicochemical conditions by rapid quenching due to their small size ranging from 125 to 250 μm. Our results demonstrate that BrG and BlG magmas are textually and chemically identical but their redox conditions are different at the eruption. The oxidation of magma can be caused by following two processes; 1) diffusive transport

  3. Evidence for the development of permeability anisotropy in lava domes and volcanic conduits

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    Farquharson, Jamie I.; Heap, Michael J.; Lavallée, Yan; Varley, Nick R.; Baud, Patrick

    2016-09-01

    The ease at which exsolving volatiles can migrate though magma and outgas influences the explosivity of a volcanic eruption. Volcanic rocks often contain discrete discontinuities, providing snapshots of strain localisation processes that occur during magma ascent and extrusion. Whether these features comprise pathways for or barriers to fluid flow is thus of relevance for volcanic eruption and gas emission modelling. We report here on nine discontinuity-bearing andesite blocks collected from Volcán de Colima, Mexico. We present a systematic porosity and permeability study of fifty cores obtained from the blocks collected, and interpret the genetic processes of the discontinuities through detailed microstructural examination. Bands in pumiceous blocks were inferred to be relicts of inhomogeneous bubble expansion which, despite significantly increasing porosity, do not markedly affect permeability. Other discontinuities in our blocks are interpreted to be shear strain-induced flow banding, cavitation porosity, and/or variably healed fractures. In each of these cases, an increase in permeability (up to around three orders of magnitude) was measured relative to the host material. A final sample contained a band of lower porosity than the host rock, characterised by variably infilled pores. In this case, the band was an order of magnitude less permeable than the host rock, highlighting the complex interplay between dilatant and densifying processes in magma. We therefore present evidence for significant permeability anisotropy within the conduit and/or dome of a volcanic system. We suggest that the abundance and distribution of strain localisation features will influence the escape or entrapment of volatiles and therefore the evolution of pore pressure within active volcanic systems. Using a simple upscaling model, we illustrate the relative importance of permeable structures over different lengthscales. Strain localisation processes resulting in permeability

  4. Inferring conduit process from population studies of cinder cone craters

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    Bemis, Karen G.

    2014-05-01

    One of the most observable aspects of magma conduits is of course their exit to the Earth's surface: the volcanic crater. The craters resulting from small mostly-monogenetic volcanic eruptions vary in considerable in size and shape, even after accounting for variation in size. Presumably, these variations tell us something about the state of the conduit at least in the ending stages of eruption. But what? This work explores the statistical properties of crater populations in Guatemala and elsewhere and speculates on the conduit processes that may explain the complex behavior. Crater depths are strongly correlated with cone slopes even when normalized by cone diameter, which suggests the importance of the impact of the volatile content (which may influence slope through fragmentation and the resulting grain size) and the duration of eruption (which may influence whether the cone is built to its maximum slope) despite erosion acting to reduce observed crater depths (cone slopes are known to decrease with erosion but cone diameters increase).

  5. A Linearized Model for Wave Propagation through Coupled Volcanic Conduit-crack Systems Filled with Multiphase Magma

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    Liang, C.; Dunham, E. M.; OReilly, O. J.; Karlstrom, L.

    2015-12-01

    Both the oscillation of magma in volcanic conduits and resonance of fluid-filled cracks (dikes and sills) are appealing explanations for very long period signals recorded at many active volcanoes. While these processes have been studied in isolation, real volcanic systems involve interconnected networks of conduits and cracks. The overall objective of our work is to develop a model of wave propagation and ultimately eruptive fluid dynamics through this coupled system. Here, we present a linearized model for wave propagation through a conduit with multiple cracks branching off of it. The fluid is compressible and viscous, and is comprised of a mixture of liquid melt and gas bubbles. Nonequilibrium bubble growth and resorption (BGR) is quantified by introducing a time scale for mass exchange between phases, following the treatment in Karlstrom and Dunham (2015). We start by deriving the dispersion relation for crack waves travelling along the multiphase-magma-filled crack embedded in an elastic solid. Dissipation arises from magma viscosity, nonequilibrium BGR, and radiation of seismic waves into the solid. We next introduce coupling conditions between the conduit and crack, expressing conservation of mass and the balance of forces across the junction. Waves in the conduit, like those in the crack, are influenced by nonequilibrium BGR, but the deformability of the surrounding solid is far less important than for cracks. Solution of the coupled system of equations provides the evolution of pressure and fluid velocity within the conduit-crack system. The system has various resonant modes that are sensitive to fluid properties and to the geometry of the conduit and cracks. Numerical modeling of seismic waves in the solid allows us to generate synthetic seismograms.

  6. Volcanic conduit migration over a basement landslide at Mount Etna (Italy).

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    Nicolosi, I; Caracciolo, F D'Ajello; Branca, S; Ventura, G; Chiappini, M

    2014-06-13

    The flanks of volcanoes may slide in response to the loading of the edifice on a weak basement, magma push, and/or to tectonic stress. However, examples of stratovolcanoes emplaced on active landslides are lacking and the possible effects on the volcano dynamics unknown. Here, we use aeromagnetic data to construct a three-dimensional model of the clay-rich basement of Etna volcano (Italy). We provide evidence for a large stratovolcano growing on a pre-existing basement landslide and show that the eastern Etna flank, which slides toward the sea irrespective of volcanic activity, moves coherently with the underlying landslide. The filling of the landslide depression by lava flows through time allows the formation of a stiffness barrier, which is responsible for the long-term migration of the magma pathways from the coast to the present-day Etna summit. These unexpected results provide a new interpretation clue on the causes of the volcanic instability processes and of the mechanisms of deflection and migration of volcanic conduits.

  7. Modeling magma flow in volcanic conduit with non-equilibrium crystallization

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    Yulia, Tsvetkova

    2010-05-01

    Modeling magma flow in volcanic conduit including with non -equilibrium crystallization There is a set of models of magma flow in volcanic conduits which predicts oscillations in magma discharge during extrusion of lava domes. These models neglect heating of surrounding rocks and use 1D approximation of the flow in the conduit. Here magma flow is investigated with an account of heat exchange between surrounding rocks and magma and different dependences viscosity on temperature and crystal concentration. Stick-slip conditions were applied at the wall. The flow is assumed to be quasi-static and quasi 1D. Only vertical component of velocity vector is present, thus, we do not consider horizontal momentum balance. At the top of the conduit the pressure is assumed to be fixed, chamber pressure changes according with magma influx and outflux. First set of simulation was made for the viscosity that depends on cross-section average crystal concentration and parabolic velocity profile. In earlier models that account for crystal growth kinetics the temperature was allowed to change only due to the release of latent heat of crystallization. Heat transfer leads to cooling of the outer parts of the conduit leading to high crystal contents and high magma viscosities. Changes in viscosity result in changes in discharge rate. For the non-isothermal case there is no motion during most part of the cycle and a portion of magma solidifies at the top of the conduit forming a plug. During repose period chamber pressure is growing due to influx of fresh magma, and magma discharge rate starts to increase. Influx of hot magma into the conduit leads to decrease in friction resulting in a jump in discharge rate that lead to depressurization of magma chamber. Discharge rate decreases and magma solidifies again. For isothermal model with the same parameters discharge rate monotonically tends to the value of Qin. Simulation reveal that crystal content changes significantly across the conduit

  8. Modelling shear bands in a volcanic conduit: Implications for over-pressures and extrusion-rates

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    Hale, Alina J.; Mühlhaus, Hans-B.

    2007-11-01

    Shear bands in a volcanic conduit are modelled for crystal-rich magma flow using simplified conditions to capture the fundamental behaviour of a natural system. Our simulations begin with magma crystallinity in equilibrium with an applied pressure field and isothermal conditions. The viscosity of the magma is derived using existing empirical equations and is dependent upon temperature, water content and crystallinity. From these initial conduit conditions we utilize the Finite Element Method, using axi-symmetric coordinates, to simulate shear bands via shear localisation. We use the von Mises visco-plasticity model with constant magma shear strength for a first look into the effects of plasticity. The extent of shear bands in the conduit is explored with a numerical model parameterized with values appropriate for Soufrière Hills Volcano, Montserrat, although the model is generic in nature. Our model simulates shallow (up to approximately 700 m) shear bands that occur within the upper conduit and probably govern the lava extrusion style due to shear boundaries. We also model the change in the over-pressure field within the conduit for flow with and without shear bands. The pressure change can be as large as several MPa at shallow depths in the conduit, which generates a maximum change in the pressure gradient of 10's of kPa/m. The formation of shear bands could therefore provide an alternative or additional mechanism for the inflation/deflation of the volcano flanks as measured by tilt-metres. Shear bands are found to have a significant effect upon the magma ascent rate due to shear-induced flow reducing conduit friction and altering the over-pressure in the upper conduit. Since we do not model frictional controlled slip, only plastic flow, our model calculates the minimum change in extrusion rate due to shear bands. However, extrusion rates can almost double due to the formation of shear bands, which may help suppress volatile loss. Due to the paucity of data and

  9. A robotic approach to mapping post-eruptive volcanic fissure conduits

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    Parcheta, Carolyn E.; Pavlov, Catherine A.; Wiltsie, Nicholas; Carpenter, Kalind C.; Nash, Jeremy; Parness, Aaron; Mitchell, Karl L.

    2016-06-01

    VolcanoBot was developed to map volcanic vents and their underlying conduit systems, which are rarely preserved and generally inaccessible to human exploration. It uses a PrimeSense Carmine 1.09 sensor for mapping and carries an IR temperature sensor, analog distance sensor, and an inertial measurement unit (IMU) inside a protective shell. The first field test succeeded in collecting valuable scientific data but revealed several needed improvements, including more rugged cable connections and mechanical couplers, increased ground clearance, and higher-torque motors for uphill mobility. The second field test significantly improved on all of these aspects but it traded electrical ruggedness for reduced data collection speed. Data collected by the VolcanoBots, while intermittent, yield the first insights into the cm-scale geometry of volcanic fissures at depths of up to 25 m. VolcanoBot was deployed at the 1969 Mauna Ulu fissure system on Kīlauea volcano in Hawai'i. It collected first-of-its-kind data from inside the fissure system. We hypothesized that 1) fissure sinuosity should decrease with depth, 2) irregularity should be persistent with depth, 3) any blockages in the conduit should occur at the narrowest points, and 4) the fissure should narrow with depth until it is too narrow for VolcanoBot to pass or is plugged with solidified lava. Our field campaigns did not span enough lateral or vertical area to test sinuosity. The preliminary data indicate that 1) there were many irregularities along fissures at depth, 2) blockages occurred, but not at obviously narrow locations, and 3) the conduit width remained a consistent 0.4-0.5 m for most of the upper 10 m that we analyzed.

  10. A tool for computing time-dependent permeability reduction of fractured volcanic conduit margins.

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    Farquharson, Jamie; Wadsworth, Fabian; Heap, Michael; Baud, Patrick

    2016-04-01

    Laterally-oriented fractures within volcanic conduit margins are thought to play an important role in tempering eruption explosivity by allowing magmatic volatiles to outgas. The permeability of a fractured conduit margin - the equivalent permeability - can be modelled as the sum of permeability contributions of the edifice host rock and the fracture(s) within it. We present here a flexible MATLAB® tool which computes the time-dependent equivalent permeability of a volcanic conduit margin containing ash-filled fractures. The tool is designed so that the end-user can define a wide range of input parameters to yield equivalent permeability estimates for their application. The time-dependence of the equivalent permeability is incorporated by considering permeability decrease as a function of porosity loss in the ash-filled fractures due to viscous sintering (after Russell and Quane, 2005), which is in turn dependent on the depth and temperature of each fracture and the crystal-content of the magma (all user-defined variables). The initial viscosity of the granular material filling the fracture is dependent on the water content (Hess and Dingwell, 1996), which is computed assuming equilibrium depth-dependent water content (Liu et al., 2005). Crystallinity is subsequently accounted for by employing the particle-suspension rheological model of Mueller et al. (2010). The user then defines the number of fractures, their widths, and their depths, and the lengthscale of interest (e.g. the length of the conduit). Using these data, the combined influence of transient fractures on the equivalent permeability of the conduit margin is then calculated by adapting a parallel-plate flow model (developed by Baud et al., 2012 for porous sandstones), for host rock permeabilities from 10-11 to 10-22 m2. The calculated values of porosity and equivalent permeability with time for each host rock permeability is then output in text and worksheet file formats. We introduce two dimensionless

  11. Short-term spasmodic switching of volcanic tremor source activation in a conduit of the 2011 Kirishima eruption

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    Matsumoto, S.; Shimizu, H.; Matsushima, T.; Uehira, K.; Yamashita, Y.; Nakamoto, M.; Miyazaki, M.; Chikura, H.

    2012-04-01

    Volcanic tremors are seismic indicators providing clues for magma behavior, which is related to volcanic eruptions and activity. Detection of spatial and temporal variations of volcanic tremors is important for understanding the mechanism of volcanic eruptions. However, temporal variations of tremor activity in short-term than a minute have not been previously detected by seismological observations around volcanoes. Here, we show that volcanic tremor sources were activated at the top of the conduit (i.e. the crater) and at its lower end by analyzing seismograms from a dense seismic array during the 2011 Kirishima eruption. We observed spasmodic switching in the seismic ray direction during a volcanic tremor sequence. Such fine volcanic tremor structure suggests an interaction between tremor sources located in both deep and shallow depths. Our result suggests that seismic array observations can monitor the magma behavior and contribute to the evaluation of the activity's transition.

  12. The effect of shear on permeability in a volcanic conduit: a case study at Unzen volcano, Japan

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    Ashworth, James; Lavallée, Yan; Wallace, Paul; Lamur, Anthony; Kendrick, Jackie; Miwa, Takahiro

    2016-04-01

    The efficiency of outgassing at volcanoes is a function of permeability, and exerts a major influence on the type of eruptive behaviour exhibited. Understanding how shear affects the permeability profile across volcanic conduits is therefore a key part of understanding volcanic processes and the associated hazards. During the final months of the 1990-1995 eruption of Unzen volcano in southern Japan, extrusion of a dacite spine followed a period of endogenous dome growth. Many of the resulting formations are relatively accessible, allowing for the study of a variety of associated deformation phenomena. One of these formations, a ~6 m wide block, is a section of the extruded spine, that forms the basis for this study on shallow conduit processes. It displays a textural gradation from highly sheared rock to rock with negligible deformation, and is bounded at the high shear end by an agglutinated block of gouge that is thought to represent the conduit margin. A multi-faceted approach was taken to investigate the variation of permeability across the spine and its implications for processes occurring within the conduit. The permeability was measured at several points along the exposed surface of the spine transect using a field permeameter. Sample blocks from four of these locations were collected and tested in the lab using a hydrostatic pressure vessel water-flow permeameter and categorized as: gouge; highest shear; moderate shear; negligible shear. Each block was tested in three orthogonal axes: one perpendicular to observed shear; and two in the plane of shear. For each of these rocks, permeability and porosity measurements were made at a wide range of effective pressures (5 to 100 MPa), using a controlled upstream/downstream pore pressure gradient of 0.5 MPa (at an average pore pressure of 1.25 MPa). Thin sections of each sample were also taken prepared and analysed to describe the primary microstructures controlling the permeability of the rock. Textural analysis

  13. Formation of obsidian pyroclasts by sintering of ash particles in the volcanic conduit

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    Gardner, James E.; Llewellin, Edward W.; Watkins, James M.; Befus, Kenneth S.

    2017-02-01

    The ranges in intensity and style of volcanic eruptions, from highly explosive Plinian eruptions to quiescent lava extrusions, depend on the style and efficiency of gas loss from ascending magma. Obsidian pyroclasts - small, glassy pieces of quenched magma found in some volcanic tephra beds - may preserve valuable information about magma degassing in their vesicle textures and volatile contents. Accurate interpretation of their textures and volatiles, however, requires understanding the mechanism of formation of the pyroclasts. Obsidian pyroclasts from the ca. 1325-1350 C.E. North Mono eruption of Mono Craters (CA, USA) were analyzed and found to have H2O and CO2 contents indicating that they were formed at pressures in the approximate range of 3-40 MPa. Many also contain domains with differing vesicle textures, separated by boundaries containing xenocrystic material, indicating that they are composed of smaller fragments that have sutured together. More than half of the pyroclasts analyzed contained small (∼10 μm), highly distorted vesicles, with multi-cuspate morphology, interpreted as the remnants of interstitial gas trapped amongst sintered fragments of melt/glass. Rounded vesicles are also common and are interpreted to result from surface tension-driven relaxation of the distorted vesicles. Calculated timescales of sintering and relaxation are consistent with timescales for pyroclast formation indicated by H2O re-equilibration within the heterogeneous pyroclasts. This sintering model for the origin of obsidian pyroclasts is further supported by the observation that spherical vesicles are found mainly in H2O-rich pyroclasts, and distorted vesicles mainly in H2O-poor pyroclasts. We conclude that obsidian pyroclasts generated during the North Mono eruption were formed by cycles of fragmentation, sintering/suturing, and relaxation, over a very wide range of depths within the conduit; we find no evidence to support pumice (foam) collapse as the formation

  14. Open system degassing, bubble rise and flow dynamics within volcanic conduits- an experimental approach

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    Pioli, L.; Azzopardi, B. J.; Bonadonna, C.; Marchetti, E.; Ripepe, M.

    2009-12-01

    Open conduit basaltic volcanoes are characterized by frequent eruptions, usually consisting in mild Strombolian and Hawaiian explosions, alternating years to months of quiescence periods, with degassing activity from the central conduit. Recent improvements of thermal, video, radar and acoustic monitoring techniques have provided new powerful tools for the study of degassing processes and made available geophysical and geochemical datasets for many central volcanoes, such as Stromboli, Etna (Italy), Kilauea (Hawaii), Villarrica (Chile). These studies revealed that degassing is an unsteady, often pulsatory process, characterized by fluctuations in both intensity and composition of the emitted gases. Unambiguous interpretation of monitoring data of surface activity in terms of conduit dynamics and flow processes is, however, not possible, due to partial knowledge of the physical processes controlling the dynamics of two-phase flows in magmas. We performed a series of experiments to gain further insights on the dynamics of the gas-bubble rise in magmas within a cylindrical conduit, their ability to segregate and coalesce and the effect of these processes on the degassing dynamics. The experiments consisted in generating fluxes at variable intensities of air through stagnant water or glucose syrup in a bubble column apparatus 6.5 m high and with a diameter of 24 cm diameter. Glucose syrup and water are Newtonian liquids with viscosity ranging from 2.4 to 204.0 Pa*s and from 1.7 to 0.2 10 -3 Pa*s respectively, depending on temperature. Air was inserted at the base of the column through a variable number (1 to 25) of 5mm-diameter nozzles reaching surficial gas velocities of up to 0.5 m/s. The activity of the bubble column was monitored through temperature, pressure, void fraction and acoustic measurements and filmed by a high-speed camera with maximum resolution of 800x600 pixels. Pressure fluctuations, vesicularity and acoustic signal were then analyzed and correlated

  15. Shallow conduit processes during the ad 1158 explosive eruption of Hekla volcano, Iceland

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    Janebo, Maria H.; Houghton, Bruce F.; Thordarson, Thorvaldur; Larsen, Gudrun

    2016-10-01

    Hekla is one of the most frequently active felsic volcanic systems in the world, with several known pre-historic large Plinian eruptions and 18 historical subplinian to small Plinian eruptions. A common view is that Plinian eruptions of Hekla are relatively short lived and purely explosive events. In detail, these events exhibit subtle differences in terms of deposit characteristics, reflecting significant differences in eruption behaviour. Of the 18 historical eruptions, two had bulk magma compositions with >66 wt% SiO2: a Plinian eruption in ad 1104 and a smaller, less well characterised, but atypical subplinian eruption in ad 1158. The ad 1158 eruption was a relatively sustained, dry (magmatic) eruption with a more powerful opening phase followed by a lower intensity, waning phase accompanied by minor destabilisation and collapse of the conduit walls. We examine here the dynamics of the ad 1158 eruption, focussing on the role of shallow conduit processes in modulating eruption dynamics. Vesicularity data constrain the relative influence of bubble nucleation, growth, and coalescence. The juvenile pyroclasts are composed of two types of microvesicular pumice (white and grey) with contrasting vesicle number density, vesicle-size distribution, and phenocryst and microlite contents. Textural analysis shows that these pumices reflect heterogeneity developed pre- to syn-eruptively in the conduit and that entrainment of longer resident magma by faster ascending magma permitted magma of contrasting maturity to be fragmented simultaneously. In this regard, the mixed melt of the ad 1158 eruption contrasts with the compositionally homogeneous melt phase of the more powerful ad 1104 Plinian event, which was typified by more uniform conduit and eruption dynamics accompanying higher average ascent rates.

  16. Shallow conduit processes during the 1158 AD explosive eruption of Hekla volcano, Iceland

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    Janebo, Maria; Houghton, Bruce; Thordarson, Thor; Larsen, Gudrun

    2015-04-01

    Hekla is one of the most frequently active silicic volcanic systems in the world, with multiple pre-historic large Plinian eruptions and 18 historical subplinian-Plinian eruptions. The common view is that the Plinian phases of the largest Hekla eruptions are all relatively homogeneous in style. Of the historical eruptions, only two were silicic: a Plinian eruption in 1104 and a smaller, less well characterized, eruption in 1158. We examine the dynamics of the 1158 eruption in detail with focus on the modulating role of shallow conduit processes. Grain size analysis, componentry, and density were used to characterize gradual and abrupt changes during the course of the eruption and quantitative vesicularity analysis was used to constrain the influence of bubble nucleation and coalescence. The 1158 eruption was a relatively steady, dry eruption with a more powerful opening phase followed by a lower intensity, waning phase accompanied by destabilization and collapse of the conduit walls. The juvenile pyroclasts are comprised of three types of microvesicular ragged pumice: white, grey, and banded. The abundance of grey pumice decreases as the eruption reaches maximum intensity, and then increases again during the waning phase of the eruption. The white pumices are more vesicular than the grey pumice, and the banded pumices have vesicularities that span predictably the range of the two end-members. The macroscopic differences between the white and grey pumice are accompanied by differences on a microscopic scale, most notably in a decrease in vesicle number density (VND) and a broadening of the vesicle size distribution, as well as increased crystal content. VND values of 0.5 to 1 E+6 mm-3 are similar to those recorded for the more powerful and sustained Plinian phases of the Novarupta 1912 and Taupo 181 eruptions in our laboratory. The 1158 pumice clasts display complex textures with adjacent domains of contrasting texture, alluding to complex nucleation, growth and

  17. Modeling the closure of volcanic conduits with an application to Mount Vesuvius

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    Quareni, Francesca; Mulargia, Francesco

    1993-03-01

    The eruptive activity of a volcano is controlled by the opening and closure of conduits through which magma ascends to the surface. We develop a model to study the deformation of a cylindrical conduit surrounded by a viscoelastic cylindrical region in an infinite, elastic, homogeneous space. The viscoelastic behavior of the zone around the conduit is due to heat conduction from the hot magma, which raises the temperature beyond the brittle-ductile transition point. The effect of a tectonic regional stress which favors (compressive) or acts against (tensile) conduit closure is taken into account. Conduit closure is found to be ruled essentially by the extension of the viscoelastic region and by the ratio between its rigidity and the rigidity of the surrounding elastic medium, while tectonic stress is much less important. The model is applied to the last eruptive cycle of Mount Vesuvius. We find that an open conduit condition has been possible from 1631 to 1944, while the quiescence from 1944 on implies a closed conduit state.

  18. Experimental analysis of bubble-driven magma motion in a volcanic conduit and how it affects lava lake sustainability

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    Pansino, S. G.; Calder, E. S.; Menand, T.

    2013-12-01

    The effect of bubble ascent dynamics on magma motion within a conduit has not previously been well studied. Investigation of bubble dynamics is undertaken using an analogue model for magma convection in a volcanic conduit, representing the upper-most section where large bubbles or gas slugs can be present. In the experiments, bubbles rise through an initially stagnant medium in a cylindrical tube and the resulting liquid descent velocity (liquid flux) is measured. The effects of gas flux and liquid viscosity on liquid flux are determined. It is shown that liquid flux depends on gas flux and on the two-phase flow regime. The induced liquid flux is an order of magnitude higher when the two-phase flow regime is turbulent rather than laminar. For each flow regime, scaling analysis is used to describe how the liquid flux changes with gas flux (using experimentally-derived data). The liquid flux is roughly 15% of the gas flux in the turbulent regime and 1% of the gas flux in the laminar regime. These models are then applied to field and remote sensing data from selected volcanoes to determine how the magma flux estimation changes with consideration of bubble dynamics. Bubble-driven liquid motions can have a significant effect on magma convection in low-viscosity systems (less than 103 Pa*s), affecting the shallowest hundreds to tens of meters of magma in the conduit. In higher-viscosity magmas, these effects are more suppressed, causing laminar flow proportions of magma flux. Keywords: magma convection, lava lakes, bubble-driven convection, persistent volcanism, gas dynamics, two-phase flow, degassing

  19. Nonequilibrium flow in volcanic conduits and application to the eruptions of Mt. St. Helens on May 18, 1980, and Vesuvius in AD 79

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    Dobran, Flavio

    1992-02-01

    A steady-state, one-dimensional, and nonhomogeneous two-phase flow model was developed for the prediction of local flow properties in volcanic conduits. The model incorporates the effects of relative velocity between the phases and for the variable magma viscosity. The resulting set of nonlinear differential equations was solved by a stiff numerical solver and the results were verified with the results of basaltic fissure eruptions obtained by a homogeneous two-phase flow model, before applying the model to the eruptions of Mt. St. Helens and Vesuvius volcanoes. This verification, and a study of the sensitivity of several modeling parameters, proved effective in establishing the confidence in the predicted nonequilibrium results of flow distribution in the conduits when the mass flow rate is critical or maximum. The application of the model to the plinian eruptions of Mt. St. Helens on May 18, 1980, and Vesuvius in AD 79, demonstrates the sensitivity of the magma discharge rate and distributions of pressure, volumetric fraction, and velocities of phases, on the hydrous magma viscosity feeding the volcanic conduits. Larger magma viscosities produce smaller mass discharge rates (or greater conduit diameters), smaller exit pressures, larger disequilibrium between the phases, and larger difference between the local lithostatic and fluid pressures in the conduit. This large pressure difference occurs when magma fragments and may cause a rupture of the conduit wall rocks, producing a closure of the conduit and cessation of the volcanic eruption, or water pouring into the conduit from underground aquifers leading to phreatomagmatic explosions. The motion of the magma fragmentation zone along a conduit during an eruption can be caused by the varying viscosity of magma feeding the volcanic conduit and may cause intermittent phreatomagmatic explosions during the plinian phases as different underground aquifers are activated at different depths. The variation of magma

  20. Dome/Conduit inflation-deflation at Volcan de Fuego, Colima: evidence from seismic and geodetic data

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    Arciniega-Ceballos, A.; Cabral-Cano, E.; Castaneda, E.; Salazar-Tlaczani, L.; DeMets, C.; Marquez-Azua, B.

    2013-12-01

    Volcan de Fuego is a strato-volcano (3860 m high) in Colima Mexico, which has been presenting high explosive activity from small to large explosive events, occasionally accompanied by pyroclastic flows, periodic dome growth and destructive phases, intense fumarole activity and degassing, during the last decade. Since June 2011 a broadband seismic and geodetic network has been operating at radial distances ranging between 1.5 and 4 km from the crater. Five stations are equipped with a Nanometrics 120 s Trillium seismometer and Trimble NetR9 GPS receiver, from which three of them include a MiniDOAS gas detection system. During the period of study eruptive activity of Volcan de Fuego has been dominated by dome growth, degassing and occasional large explosions. These events are associated with the partial dome destruction and frequent ash emissions. Preliminary analyses of two-year continuous records of broadband seismic and geodesy data have revealed dome/conduit inflation-deflation phases related to conspicuous VLP tremor in the 1-20 s period band. VLP tremor has been detected in several periods since 2011 in all stations of the network. VLP tremor may be spasmodic or a persistent signal that fluctuates both in amplitude and time. Since in volcanic areas microseismicity may cover a period range of 5 to 20 s, we analyze and characterize the noise levels considering the relative amplitude with respect to the average amplitude of microseismic noise at each station. We evaluate temporal and frequency variations of volcanic activity with respect the microseismic levels. Our results indicate that the energy of the wave field in the 1-20 s period band is dominated by volcanic activity, especially in cases associated with large eruptive events. The presence of VLP tremor correlates well with inflation-deflation phases observed in the GPS time series, with total vertical displacements of 20-40 mm. This behavior is most evident in the COPN, COPE and COLW stations, which are

  1. Manufacture of porous biodegradable polymer conduits by an extrusion process for guided tissue regeneration

    Science.gov (United States)

    Widmer, M. S.; Gupta, P. K.; Lu, L.; Meszlenyi, R. K.; Evans, G. R.; Brandt, K.; Savel, T.; Gurlek, A.; Patrick, C. W. Jr; Mikos, A. G.; McIntire, L. V. (Principal Investigator)

    1998-01-01

    We have fabricated porous, biodegradable tubular conduits for guided tissue regeneration using a combined solvent casting and extrusion technique. The biodegradable polymers used in this study were poly(DL-lactic-co-glycolic acid) (PLGA) and poly(L-lactic acid) (PLLA). A polymer/salt composite was first prepared by a solvent casting process. After drying, the composite was extruded to form a tubular construct. The salt particles in the construct were then leached out leaving a conduit with an open-pore structure. PLGA was studied as a model polymer to analyze the effects of salt weight fraction, salt particle size, and processing temperature on porosity and pore size of the extruded conduits. The porosity and pore size were found to increase with increasing salt weight fraction. Increasing the salt particle size increased the pore diameter but did not affect the porosity. High extrusion temperatures decreased the pore diameter without altering the porosity. Greater decrease in molecular weight was observed for conduits manufactured at higher temperatures. The mechanical properties of both PLGA and PLLA conduits were tested after degradation in vitro for up to 8 weeks. The modulus and failure strength of PLLA conduits were approximately 10 times higher than those of PLGA conduits. Failure strain was similar for both conduits. After degradation for 8 weeks, the molecular weights of the PLGA and PLLA conduits decreased to 38% and 43% of the initial values, respectively. However, both conduits maintained their shape and did not collapse. The PLGA also remained amorphous throughout the time course, while the crystallinity of PLLA increased from 5.2% to 11.5%. The potential of seeding the conduits with cells for transplantation or with biodegradable polymer microparticles for drug delivery was also tested with dyed microspheres. These porous tubular structures hold great promise for the regeneration of tissues which require tubular scaffolds such as peripheral nerve

  2. Structure Of Conduits Of The Acidic Volcanism And Related Deposits In The Paraná-Etendeka Magmatic Province, São Marcos Region, South Brazil

    Science.gov (United States)

    Guimarães, L. F.; De Campos, C. P.; Lima, E. F. D.; Janasi, V. A.

    2015-12-01

    Voluminous acidic volcanics from the Paraná-Etendeka Magmatic Province crop out in the southern part of Brazil. The conduits responsible for the feeding of this intermediate/acid volcanism are preserved and well exposed in the São Marcos region (Lima et al. 2012; Geologia USP 12:49-64). Conduits are aligned along a NW-SE trend and have thicknesses up to 1 km. These structures are often characterized by mixing between dacitic and rhyodacitic magmas, with intercalation between two major zones: 1) reddish or grayish vitrophiricdacite/rhyodacite, sub-divided in massive or vesiculated; 2) reddish or grayish vitrophiric fragmented dacite/rhyodacite composed of bubble-rich angular to rounded blocks. Such fragments commonly deform coeval to the flow. A third zone dominated by filaments depicts a chaotic stretching-and-folding process from the mixture of the acid magmas. We used classical field measurements of flow structures and recognized main flow directions in these feeder-dikes. They follow two preferential directions: NW, ranging from N272° to N 355°, and NE, varying from N20° to N85°. These directions are indicative of a transtensive fissural system, which seems to be related to conjugated fractures. Evidence of an important fragmentation process in the conduits point towards the presence of related products in this region, thus rheomorphic deposits such as those observed elsewhere (e.g. Uruguay and Namibia) are expected to occur. Possible vestiges of these deposits could be represented by restricted outcrops of lens-shaped and banded hipohyaline, occasionally bubble-rich, dacites. The presence of continuous pseudotachylitic levels, tightly folded bands with horizontal axial planes together with local deformed bubble-rich pumice-like lens could be indicative of remelting and rheomorphism of previous vulcanoclastic material. Coulees and compound (lobed) dacitic lava flows, reaching up to 5-8 meters length, occur as the uppermost deposits and correspond to the

  3. A multidisciplinary study on the crustal nature of volcanic conduits and magma reservoirs

    Science.gov (United States)

    Flinders, Ashton F.

    Volcanic settings vary widely not only in their eruptive style and products, but in the manner magma travels from deep sources to individual eruptive centers. Imaging these pathways, and their associated crustal reservoirs, provides unique and unprecedented views into these environments. Imaging techniques are varied with the strength of the technique often based on data availability. As such, we focus on two methods---gravity and seismic---in two different settings, each with its own unique volcanic environments, crustal structures, and associated data resources. The first, the Hawaiian Islands, are the most geologically studied hot-spot islands in the world, yet the only large-scale compilation of marine and land gravity data is more than 45 years old. We present a new chain-wide gravity compilation allowing us to locate current and former volcanic centers, major rift zones, a previously suggested volcano, and show that volcanoes along the chain are composed of a small proportion of intrusive material (sourced melt to the surface. We image two zones of reduced velocity, one of which correlates with a proposed extensive zone of mid-crustal partial melt which likely supplies evolved magmas to the surrounding volcanoes and vents, including Mounts St. Helens and Adams.

  4. Study on the air flow field of the drawing conduit in the spunbonding process

    Directory of Open Access Journals (Sweden)

    Wu Li-Li

    2015-01-01

    Full Text Available The air flow field of the drawing conduit in the spunbonding process has a great effect on the polymer drawing, the filament diameter and orientation. A numerical simulation of the process is carried out, and the results are compared with the experimental data, showing good accuracy of the numerical prediction. This research lays an important foundation for the optimal design of the drawing conduit in the spunbonding process.

  5. Modeling of the thermal state of Mount Vesuvius from 1631 A.D. to present and the role of CO2 degassing on the volcanic conduit closure after the 1944 A.D. eruption

    Science.gov (United States)

    Quareni, Francesca; Moretti, Roberto; Piochi, Monica; Chiodini, Giovanni

    2007-03-01

    The last eruptive event at Mount Vesuvius occurred in 1944 A.D., ending a cycle of continuous eruptive activity started with the sub-Plinian event of 1631 A.D. The aim of this research is (1) to model the thermal evolution of the volcanic system from 1631 A.D. up to the present and (2) to investigate the possible process leading the volcano to the current state of quiescence. A finite element software is employed to solve the time-dependent energy equation and obtain the thermal field in the volcanic edifice and the surrounding medium. Volcanological, petrological, and geophysical constraints are used to define the crustal structure beneath the volcanic edifice, the magma supply system active since 1631 A.D., and the physico-chemical conditions of magma. Thermodynamic properties of magma and wall rocks have been evaluated from well-established thermo-chemical compilations and data from the literature. It is shown that heat transfer due to magma degassing is required in addition to the heat conduction in order to obtain transient depth-temperature fields consistent with geochemical observations, high crustal magnetization, and rigid behavior of the shallow crust as indicated by geophysical data. Surface data of carbon dioxide soil flux coming out from the Mount Vesuvius crater are taken to constrain such an additional heat flux. The agreement between modeled and measured temperatures at the crater since 1944 A.D. proves the consistency of the model. It is concluded that the present state of quiescence of Mount Vesuvius is mostly a consequence of the absence of magma supply from the deep reservoir into the shallower system. This allows the cooling of residual magma left within the volcanic conduit and the transition from continuous eruptive activity to the condition of conduit obstruction. In this scenario, the hydrothermal system may have developed subsequent to the cooling of the magma within the conduit. Our findings are a direct consequence of the high

  6. Application of a new multiphase multicomponent volcanic conduit model with magma degassing and crystallization to Stromboli volcano.

    Science.gov (United States)

    La Spina, Giuseppe; Burton, Mike; de'Michieli Vitturi, Mattia

    2014-05-01

    Volcanoes exhibit a wide range of eruption styles, from relatively slow effusive eruptions, generating lava flows and lava domes, to explosive eruptions, in which very large volumes of fragmented magma and volcanic gas are ejected high into the atmosphere. During an eruption, much information regarding the magma ascent dynamics can be gathered: melt and exsolved gas composition, crystal content, mass flow rate and ballistic velocities, to name just a few. Due to the lack of direct observations of the conduit itself, mathematical models for magma ascent provide invaluable tools for a better comprehension of the system. The complexity of the multiphase multicomponent gas-magma-solid system is reflected in the corresponding mathematical model; a set of non-linear hyperbolic partial differential and constitutive equations, which describe the physical system, has to be formulated and solved. The standard approach to derive governing equations for two-phase flow is based on averaging procedures, which leads to a system of governing equations in the form of mass, momentum and energy balance laws for each phase coupled with algebraic and differential source terms which represent phase interactions. For this work, we used the model presented by de' Michieli Vitturi et al. (EGU General Assembly Conference Abstracts, 2013), where a different approach based on the theory of thermodynamically compatible systems has been adopted to write the governing multiphase equations for two-phase compressible flow (with two velocities and two pressures) in the form of a conservative hyperbolic system of partial differential equations, coupled with non-differential source terms. Here, in order to better describe the multicomponent nature of the system, we extended the model adding several transport equations to the system for different crystal components and different gas species, and implementing appropriate equations of state. The constitutive equations of the model are chosen to

  7. Inverse Dipolar Magnetic Anomaly Over the Volcanic Cone Linked to Reverse Polarity Magnetizations in Lavas and Tuffs - Implications for the Conduit System

    Science.gov (United States)

    Fucugauchi, J. U.; Perez-Cruz, L. L.; Trigo-Huesca, A.

    2012-12-01

    A combined magnetics and paleomagnetic study of Toluquilla monogenetic volcano and associated lavas and tuffs from Valsequillo basin in Central Mexico provides evidence on a magnetic link between lavas, ash tuffs and the underground volcanic conduit system. Paleomagnetic analyses show that lavas and ash tuffs carry reverse polarity magnetizations, which correlate with the inversely polarized dipolar magnetic anomaly over the volcano. The magnetizations in the lava and tuff show similar southward declinations and upward inclinations, supporting petrological inferences that the tuff was emplaced while still hot and indicating a temporal correlation for lava and tuff emplacement. Conduit geometry is one of the important controlling factors in eruptive dynamics of basaltic volcanoes. However volcanic conduits are often not, or only partly, exposed. Modeling of the dipolar anomaly gives a reverse polarity source magnetization associated with a vertical prismatic body with southward declination and upward inclination, which correlates with the reverse polarity magnetizations in the lava and tuff. The study documents a direct correlation of the paleomagnetic records with the underground magmatic conduit system of the monogenetic volcano. Time scale for cooling of the volcanic plumbing system involves a longer period than the one for the tuff and lava, suggesting that magnetization for the source of dipolar anomaly may represent a long time average as compared to the spot readings in the lava and tuff. The reverse polarity magnetizations in lava and tuff and in the underground source body for the magnetic anomaly are interpreted in terms of eruptive activity of Toluquilla volcano at about 1.3 Ma during the Matuyama reverse polarity C1r.2r chron.

  8. Numerical investigation of temporal changes in volcanic deformation caused by a gas slug ascent in the conduit

    Science.gov (United States)

    Kawaguchi, Ryohei; Nishimura, Takeshi

    2015-09-01

    Strombolian type eruptions are considered to be generated by a sudden release of a large gas slug that migrates upward in the conduit filled with a low viscous basaltic magma. We examine volcano deformations caused by such a gas slug to understand the Strombolian eruption mechanism from geodetic observation data. We model spatio-temporal pressure changes in the conduit by using a gas slug ascent model presented by James et al. (2008). As a gas slug ascends in the conduit, its volume expands because of depressurization. Hence, the magma head lifts up in the conduit and the upper part of the conduit wall is stressed. In the conduit, magma pressure increases with depth according to the bulk density of magma: the gas slug part with a low density is characterized by a small pressure gradient, while the other parts, consisting of melt, are characterized by a large pressure gradient. We numerically calculate volcano deformations caused by the spatio-temporal changes of magma pressure predicted from the basic equations representing gas slug locations in the conduit. Simulation results show that the radial and vertical displacements and tilt changes indicate volcano deformations that represent the inflation originating from the stress increase at the upper part of conduit. As the gas slug reaches the shallow part of conduit, the rate of inflation observed in the radial displacement decreases, the vertical displacement starts to move downward, and the tilt turns to show down toward the crater. These deflation signals are caused by a moving deflation source in the conduit that is formed beneath the gas slug. Since these predicted features are not observed in the tilt records associated with explosions at Stromboli volcano (Genco and Ripepe, 2010), it is necessary to modify the gas slug ascent model or to introduce other mechanisms to better understand the magma dynamics of Strombolian eruption.

  9. The evolution of periodic seismicity, waveform similarity, and conduit processes during unrest episodes at Tungurahua volcano, Ecuador, in 2015

    Science.gov (United States)

    Bell, Andrew; Hernandez, Stephen; Gaunt, Elizabeth; Mothes, Patricia; Hidalgo, Silvana; Ruiz, Mario

    2016-04-01

    Tungurahua is a large andesitic stratovolcano located in the Andes of Ecuador. The current eruptive phase at Tungurahua began in 1999, and has been characterised by episodes of vulcanian and strombolian activity, interspersed by periods of relative quiescence. Despite showing only modest eruptive activity in 2015, seismic data revealed a pronounced change in the behaviour of the magma-conduit system compared to the preceding 15 years of activity. The change is most notable in the periodicity of interevent-times of volcanic earthquakes. Previous seismicity at Tungurahua is characterised by interevent-time periodicities typical of a Poisson process, or modestly clustered, with slightly elevated (anti-clustered) periodicities observed only rarely during vulcanian episodes. However, activity in 2015 saw a series of unrest episodes characterised by highly-periodic interevent-times, and including several notable episodes of 'drumbeat' earthquakes. Here we report seismic and associated geophysical signals recorded at Tungurahua in 2015 by the monitoring network of the Instituto Geofisico of Ecuador, their relation to conduit processes, and implications for the origins of unrest and likely future activity. Although the nature of the low-frequency seismic signals change both within and between unrest episodes, the underlying periodicity is more consistent and gradually evolving. Waveform similarity is high within phases, resulting from the repeated activation of persistent sources, but low between different episodes, suggesting the emergence of new sources and locations. The strength of periodicity is correlated with the average waveform similarity for all unrest episodes, with the relatively low waveform similarities observed for the highly periodic drumbeat earthquakes in April due to contamination from coexisting continuous tremor. Eruptive activity consisted of a few minor explosions and ash emission events. Notably, a short-lived episode of Strombolian activity in

  10. Anatomy of a deep crustal volcanic conduit system; The Reinfjord Ultramafic Complex, Seiland Igneous Province, Northern Norway

    Science.gov (United States)

    Grant, Thomas B.; Larsen, Rune B.; Anker-Rasch, Lars; Grannes, Kim Rune; Iljina, Markku; McEnroe, Suzanne; Nikolaisen, Even; Schanche, Mona; Øen, Endre

    2016-05-01

    The Reinfjord Ultramafic Complex, Seiland Igneous Province represents a lower crustal magma chamber (25-30 km depth) that likely records a deep conduit system for mantle derived melts ascending through the continental crust. It consists of cumulates of dunite, wehrlite, olivine clinopyroxene as well as subordinate lherzolite and websterites, intruded into gabbro-norite and metasediment gneisses. Field, petrographic and geochemical data show that the intrusion developed through fractional crystallization and interactions between new batches of magma and partially solidified cumulates. This resulted in a 'reverse fractionation sequence' whereby cumulates became progressively more MgO and olivine rich with time. Contamination by partial melting of the gabbro-norite is evident in the marginal zones, but is limited in the central parts of the intrusion. Interrupted crystallization sequences of olivine → olivine + clinopyroxene and the absence of significant amounts of more evolved melts, suggests that large volumes of melt passed through the system to shallower levels in the crust leaving behind the cumulate sequences observed at Reinfjord. Therefore, the Reinfjord Ultramafic Complex represents a deep crustal conduit system, through which mantle derived melts passed. The parent melts are likely to have formed from partial melting of mantle with residual garnet and clinopyroxene.

  11. Volcanic glasses, their origins and alteration processes

    Science.gov (United States)

    Friedman, I.; Long, W.

    1984-01-01

    Natural glass can be formed by volcanic processes, lightning (fulgarites) burning coal, and by meteorite impact. By far the most common process is volcanic - basically the glass is rapidly chilled molten rock. All natural glasses are thermodynamically unstable and tend to alter chemically or to crystallize. The rate of these processes is determined by the chemical composition of the magma. The hot and fluid basaltic melts have a structure that allows for rapid crystal growth, and seldom forms glass selvages greater than a few centimeters thick, even when the melt is rapidly cooled by extrusion in the deep sea. In contrast the cooler and very viscous rhyolitic magmas can yield bodies of glass that are tens of meters thick. These highly polymerized magmas have a high silica content - often 71-77% SiO2. Their high viscosity inhibits diffusive crystal growth. Basalt glass in sea water forms an alteration zone called palagonite whose thickness increases linearly with time. The rate of diffusion of water into rhyolitic glass, which follows the relationship - thickness = k (time) 1 2, has been determined as a function of the glass composition and temperature. Increased SiO2 increases the rate, whereas increased CaO, MgO and H2O decrease the rate. The activation energy of water diffusion varies from about 19 to 22 kcal/mol. for the glasses studied. The diffusion of alkali out of rhyolite glass occurs simultaneously with water diffusion into the glass. The rate of devitrification of rhyolitic glass is a function of the glass viscosity, which in turn is a function of water content and temperature. Although all of the aforementioned processes tend to destroy natural glasses, the slow rates of these processes, particularly for rhyolitic glass, has allowed samples of glass to persist for 60 million years. ?? 1984.

  12. Quantitative volcanic susceptibility analysis of Lanzarote and Chinijo Islands based on kernel density estimation via a linear diffusion process

    Science.gov (United States)

    Galindo, I.; Romero, M. C.; Sánchez, N.; Morales, J. M.

    2016-01-01

    Risk management stakeholders in high-populated volcanic islands should be provided with the latest high-quality volcanic information. We present here the first volcanic susceptibility map of Lanzarote and Chinijo Islands and their submarine flanks based on updated chronostratigraphical and volcano structural data, as well as on the geomorphological analysis of the bathymetric data of the submarine flanks. The role of the structural elements in the volcanic susceptibility analysis has been reviewed: vents have been considered since they indicate where previous eruptions took place; eruptive fissures provide information about the stress field as they are the superficial expression of the dyke conduit; eroded dykes have been discarded since they are single non-feeder dykes intruded in deep parts of Miocene-Pliocene volcanic edifices; main faults have been taken into account only in those cases where they could modified the superficial movement of magma. The application of kernel density estimation via a linear diffusion process for the volcanic susceptibility assessment has been applied successfully to Lanzarote and could be applied to other fissure volcanic fields worldwide since the results provide information about the probable area where an eruption could take place but also about the main direction of the probable volcanic fissures. PMID:27265878

  13. Quantitative volcanic susceptibility analysis of Lanzarote and Chinijo Islands based on kernel density estimation via a linear diffusion process

    Science.gov (United States)

    Galindo, I.; Romero, M. C.; Sánchez, N.; Morales, J. M.

    2016-06-01

    Risk management stakeholders in high-populated volcanic islands should be provided with the latest high-quality volcanic information. We present here the first volcanic susceptibility map of Lanzarote and Chinijo Islands and their submarine flanks based on updated chronostratigraphical and volcano structural data, as well as on the geomorphological analysis of the bathymetric data of the submarine flanks. The role of the structural elements in the volcanic susceptibility analysis has been reviewed: vents have been considered since they indicate where previous eruptions took place; eruptive fissures provide information about the stress field as they are the superficial expression of the dyke conduit; eroded dykes have been discarded since they are single non-feeder dykes intruded in deep parts of Miocene-Pliocene volcanic edifices; main faults have been taken into account only in those cases where they could modified the superficial movement of magma. The application of kernel density estimation via a linear diffusion process for the volcanic susceptibility assessment has been applied successfully to Lanzarote and could be applied to other fissure volcanic fields worldwide since the results provide information about the probable area where an eruption could take place but also about the main direction of the probable volcanic fissures.

  14. Quantitative volcanic susceptibility analysis of Lanzarote and Chinijo Islands based on kernel density estimation via a linear diffusion process.

    Science.gov (United States)

    Galindo, I; Romero, M C; Sánchez, N; Morales, J M

    2016-06-06

    Risk management stakeholders in high-populated volcanic islands should be provided with the latest high-quality volcanic information. We present here the first volcanic susceptibility map of Lanzarote and Chinijo Islands and their submarine flanks based on updated chronostratigraphical and volcano structural data, as well as on the geomorphological analysis of the bathymetric data of the submarine flanks. The role of the structural elements in the volcanic susceptibility analysis has been reviewed: vents have been considered since they indicate where previous eruptions took place; eruptive fissures provide information about the stress field as they are the superficial expression of the dyke conduit; eroded dykes have been discarded since they are single non-feeder dykes intruded in deep parts of Miocene-Pliocene volcanic edifices; main faults have been taken into account only in those cases where they could modified the superficial movement of magma. The application of kernel density estimation via a linear diffusion process for the volcanic susceptibility assessment has been applied successfully to Lanzarote and could be applied to other fissure volcanic fields worldwide since the results provide information about the probable area where an eruption could take place but also about the main direction of the probable volcanic fissures.

  15. Catastrophic volcanic collapse: relation to hydrothermal processes.

    Science.gov (United States)

    López, D L; Williams, S N

    1993-06-18

    Catastrophic volcanic collapse, without precursory magmatic activity, is characteristic of many volcanic disasters. The extent and locations of hydrothermal discharges at Nevado del Ruiz volcano, Colombia, suggest that at many volcanoes collapse may result from the interactions between hydrothermal fluids and the volcanic edifice. Rock dissolution and hydrothermal mineral alteration, combined with physical triggers such as earth-quakes, can produce volcanic collapse. Hot spring water compositions, residence times, and flow paths through faults were used to model potential collapse at Ruiz. Caldera dimensions, deposits, and alteration mineral volumes are consistent with parameters observed at other volcanoes.

  16. Gravimetric control of active volcanic processes

    Science.gov (United States)

    Saltogianni, Vasso; Stiros, Stathis

    2017-04-01

    Volcanic activity includes phases of magma chamber inflation and deflation, produced by movement of magma and/or hydrothermal processes. Such effects usually leave their imprint as deformation of the ground surfaces which can be recorded by GNSS and other methods, on one hand, and on the other hand they can be modeled as elastic deformation processes, with deformation produced by volcanic masses of finite dimensions such as spheres, ellipsoids and parallelograms. Such volumes are modeled on the basis of inversion (non-linear, numerical solution) of systems of equations relating the unknown dimensions and location of magma sources with observations, currently mostly GNSS and INSAR data. Inversion techniques depend on the misfit between model predictions and observations, but because systems of equations are highly non-linear, and because adopted models for the geometry of magma sources is simple, non-unique solutions can be derived, constrained by local extrema. Assessment of derived magma models can be provided by independent observations and models, such as micro-seismicity distribution and changes in geophysical parameters. In the simplest case magmatic intrusions can be modeled as spheres with diameters of at least a few tens of meters at a depth of a few kilometers; hence they are expected to have a gravimetric signature in permanent recording stations on the ground surface, while larger intrusions may also have an imprint in sensors in orbit around the earth or along precisely defined air paths. Identification of such gravimetric signals and separation of the "true" signal from the measurement and ambient noise requires fine forward modeling of the wider areas based on realistic simulation of the ambient gravimetric field, and then modeling of its possible distortion because of magmatic anomalies. Such results are useful to remove ambiguities in inverse modeling of ground deformation, and also to detect magmatic anomalies offshore.

  17. Volcanic risk metrics at Mt Ruapehu, New Zealand: some background to a probabilistic eruption forecasting scheme and a cost/benefit analysis at an open conduit volcano

    Science.gov (United States)

    Jolly, Gill; Sandri, Laura; Lindsay, Jan; Scott, Brad; Sherburn, Steve; Jolly, Art; Fournier, Nico; Keys, Harry; Marzocchi, Warner

    2010-05-01

    The Bayesian Event Tree for Eruption Forecasting software (BET_EF) is a probabilistic model based on an event tree scheme that was created specifically to compute long- and short-term probabilities of different outcomes (volcanic unrest, magmatic unrest, eruption, vent location and eruption size) at long-time dormant and routinely monitored volcanoes. It is based on the assumption that upward movements of magma in a closed conduit volcano will produce detectable changes in the monitored parameters at the surface. In this perspective, the goal of BET_EF is to compute probabilities by merging information from geology, models, past data and present monitoring measurements, through a Bayesian inferential method. In the present study, we attempt to apply BET_EF to Mt Ruapehu, a very active and well-monitored volcano exhibiting the typical features of open conduit volcanoes. In such conditions, current monitoring at the surface is not necessarily able to detect short term changes at depth that may occur only seconds to minutes before an eruption. This results in so-called "blue sky eruptions" of Mt Ruapehu (for example in September 2007), that are volcanic eruptions apparently not preceded by any presently detectable signal in the current monitoring. A further complication at Mt Ruapehu arises from the well-developed hydrothermal system and the permanent crater lake sitting on top of the magmatic conduit. Both the hydrothermal system and crater lake may act to mask or change monitoring signals (if present) that magma produces deeper in the edifice. Notwithstanding these potential drawbacks, we think that an attempt to apply BET_EF at Ruapehu is worthwhile, for several reasons. First, with the exception of a few "blue sky" events, monitoring data at Mt Ruapehu can be helpful in forecasting major events, especially if a large amount of magma is intruded into the edifice and becomes available for phreatomagmatic or magmatic eruptions, as for example in 1995-96. Secondly, in

  18. Volcanic processes on early-forming asteroids.

    Science.gov (United States)

    Wilson, L.; Keil, K.

    2011-12-01

    A variety of meteorite groups represent samples of asteroids that formed while 26Al was still the dominant heat source in Solar System materials. These bodies differentiated to varying degrees beyond the temperature of FeNi-FeS melting, with sufficient silicate melting to allow metal core formation. The silicate melts segregated upward from the interiors to suffer various fates: intrusion at shallow levels, eruption onto the surface, or ejection into space in explosive eruptions in which the eruption speed exceeded the escape speed. These three styles of plutonic/volcanic activity were not mutually exclusive; their relative importance was a function of asteroid size and composition, with the major compositional factor being the total available volatile inventory. Much research has been concerned with whether silicate melts were extracted from the mantle during the period of mantle heating or while the mantle was cooling after reaching its peak temperature and degree of partial melting (a "magma ocean" stage). Traditionally, the relevant arguments have been based on the petrology and geochemistry of the meteorites sampling these bodies. Instead, we focus on the fluid dynamic aspects of eruption and intrusion processes and show how these impose additional limitations on various aspects of the igneous activity. For example, 40% melting of bodies the size of 4 Vesta (~250 km radius) and the Ureilite Parent Body (UPB, ~100 km radius) over the course of a 0.5 Ma heating period represent melt volume production rates of ~350 and 20 cubic meters per second, respectively, in each of what we demonstrate should have been ~4 volcanic provinces on each body. All differentiated asteroids must of necessity have had a surface layer ~10 km thick at sub-solidus temperatures controlled by conductive cooling. To erupt magma at the surface (or intrude magma at very shallow depth) through such a crust would have required the propagation of dikes within which the combination of dike width

  19. The evidences of progressive pressurization of volcanic conduit as driving forces of unrest phenomena analyzed via modelling of multiplatform geodetic measurements: Fernandina (GALAPAGOS) and Maunaloa (HAWAII) case studies

    Science.gov (United States)

    Pepe, Susi; Castaldo, Raffaele; Casu, Francesco; D'Auria, Luca; De Luca, Claudio; De Novellis, Vincenzo; Solaro, Giuseppe; Tizzani, Pietro

    2017-04-01

    We investigated the source of the ground deformation pattern affecting the Mauna Loa (Hawaii) and Fernandina (Galapagos) volcanoes by jointly exploiting different dataset collected by both GPS and multiplatform and multiorbit SAR sensors. We exploited the advanced Differential SAR Interferometry (DInSAR) techniques to analyze unrest episode in two different geodynamics context. Our main goal is the understanding of the relationship among the spatio-temporal evolution of the ground deformation field and the temporal volumetric variation of the detected geodetic source during the uplift phenomena. We highlight the huge opportunity in understanding volcano unrest phenomena offered by the joint use of remote sensing data and inversion procedures: this prospect is particularly relevant for the analysis of uplift events, when other geophysical measurements are not available. For Mauna Loa (Hawaii) and Fernandina (Galapagos) volcanoes, the performed statistic analysis support the source pipe-like as the more suitable geometry to explain the unrest phenomena in which magmatic masses intrude in volcanic conduits. In particular, the deformation time series achieved at MounaLoa volcano are achieved by 23 GPS permanent stations of the Hawaii surveillance network, processed by Nevada Geodetic Laboratory, 7 SAR dataset acquired from ascending and descending orbits, with different look angles and along different tracks, by the C-Band Envisat satellite along the 2003 - 2010 time period for a total of 189 SAR imagery. Moreover, we exploited 2 dataset collected from ascending and descending passes by the X-Band Cosmo Sky-Med constellation during the 2012 - 2015 time span . These SAR datasets have been processed through the advanced DInSAR technique referred to as P-SBAS (De Luca et al., 2016), which allows us to retrieve the Line of Sight (LOS) projection of the surface deformation and analyze its temporal evolution by generating displacement time series. Starting this data

  20. Subterranean fragmentation of magma during conduit initiation and evolution in the shallow plumbing system of the small-volume Jagged Rocks volcanoes (Hopi Buttes Volcanic Field, Arizona, USA)

    Science.gov (United States)

    Re, Giuseppe; White, James D. L.; Muirhead, James D.; Ort, Michael H.

    2016-08-01

    Monogenetic volcanoes have limited magma supply and lack long-lived sustained magma plumbing systems. They erupt once, often from multiple vents and sometimes over several years, and are rarely or never re-activated. Eruptive behavior is very sensitive to physical processes (e.g., volatile exsolution, magma-water interaction) occurring in the later stages of magma ascent at shallow crustal depths (flowing through dikes fragmented and conduits were formed. We have identified three main types of fragmental deposits, (1) buds (which emerge from dikes), (2) pyroclastic massifs, and (3) diatremes; these represent three different styles and intensities of shallow-depth magma fragmentation. They may develop successively and at different sites during the evolution of a monogenetic volcano. The deposits consist of a mixture of pyroclasts with varying degrees of welding and country-rock debris in various proportions. Pyroclasts are commonly welded together, but also reveal in places features consistent with phreatomagmatism, such as blocky shapes, dense groundmasses, and composite clasts (loaded and cored). The extent of fragmentation and the formation of subterranean open space controlled the nature of the particles and the architecture and geometry of these conduit structures and their deposits.

  1. Volcanic eruptions observed with infrasound

    Science.gov (United States)

    Johnson, Jeffrey B.; Aster, Richard C.; Kyle, Philip R.

    2004-07-01

    Infrasonic airwaves produced by active volcanoes provide valuable insight into the eruption dynamics. Because the infrasonic pressure field may be directly associated with the flux rate of gas released at a volcanic vent, infrasound also enhances the efficacy of volcanic hazard monitoring and continuous studies of conduit processes. Here we present new results from Erebus, Fuego, and Villarrica volcanoes highlighting uses of infrasound for constraining quantitative eruption parameters, such as eruption duration, source mechanism, and explosive gas flux.

  2. Volcanic jet noise: infrasonic source processes and atmospheric propagation

    Science.gov (United States)

    Matoza, R. S.; Fee, D.; Ogden, D. E.

    2011-12-01

    Volcanic eruption columns are complex flows consisting of (possibly supersonic) injections of ash-gas mixtures into the atmosphere. A volcanic eruption column can be modeled as a lower momentum-driven jet (the gas-thrust region), which transitions with altitude into a thermally buoyant plume. Matoza et al. [2009] proposed that broadband infrasonic signals recorded during this type of volcanic activity represent a low-frequency form of jet noise. Jet noise is produced at higher acoustic frequencies by smaller-scale man-made jet flows (e.g., turbulent jet flow from jet engines and rockets). Jet noise generation processes could operate at larger spatial scales and produce infrasonic frequencies in the lower gas-thrust portion of the eruption column. Jet-noise-like infrasonic signals have been observed at ranges of tens to thousands of kilometers from sustained volcanic explosions at Mount St. Helens, WA; Tungurahua, Ecuador; Redoubt, AK; and Sarychev Peak, Kuril Islands. Over such distances, the atmosphere cannot be considered homogeneous. Long-range infrasound propagation takes place primarily in waveguides formed by vertical gradients in temperature and horizontal winds, and exhibits strong spatiotemporal variability. The timing and location of volcanic explosions can be estimated from remote infrasonic data and could be used with ash cloud dispersion forecasts for hazard mitigation. Source studies of infrasonic volcanic jet noise, coupled with infrasound propagation modeling, hold promise for being able to constrain more detailed eruption jet parameters with remote, ground-based geophysical data. Here we present recent work on the generation and propagation of volcanic jet noise. Matoza, R. S., D. Fee, M. A. Garcés, J. M. Seiner, P. A. Ramón, and M. A. H. Hedlin (2009), Infrasonic jet noise from volcanic eruptions, Geophys. Res. Lett., 36, L08303, doi:10.1029/2008GL036486.

  3. Database for volcanic processes and geology of Augustine Volcano, Alaska

    Science.gov (United States)

    McIntire, Jacqueline; Ramsey, David W.; Thoms, Evan; Waitt, Richard B.; Beget, James E.

    2012-01-01

    Augustine Island (volcano) in lower Cook Inlet, Alaska, has erupted repeatedly in late-Holocene and historical times. Eruptions typically beget high-energy volcanic processes. Most notable are bouldery debris avalanches containing immense angular clasts shed from summit domes. Coarse deposits of these avalanches form much of Augustine's lower flanks. This geologic map at 1:25,000 scale depicts these deposits, these processes.

  4. Submarine silicic volcanism: Processes and products

    Digital Repository Service at National Institute of Oceanography (India)

    Kalangutkar, N.G.; Iyer, S.D.

    of producing a natural Icelandic granite from an evolved Kilauea-type basalt under low ƒo2, P fluid=1 to 2 kb, and P H2 O

    processes. TiO 2 is relatively low in melts generated by anatexis of gabbros which have initial low TiO 2 contents due to their depleted nature of typical cumulate formed in the oceanic crust, whereas TiO 2...

  5. Mass movement processes associated with volcanic structures in Mexico City

    Directory of Open Access Journals (Sweden)

    Víctor Carlos Valerio

    2012-11-01

    Full Text Available Mexico City, one of the most populated areas of the world, has been affected by various hazards of natural origin, such as subsidence and cracking of the soil, seismicity, floods and mass movement processes (MMPs. Owing to the lack of space on the plain, in recent years urban growth has been concentrated particularly on the slopes of the surrounding mountain ranges, and this has significantly modified the dynamics of the relief as well as the hydrogeological conditions. The specific character of natural susceptibility to mass movements is strongly dependent on the geological–structural and morphological characteristics of the volcanic bodies that form the mountainous relief. This natural susceptibility, combined with the characteristics of vulnerability of the society, creates risk conditions that can generate severe consequences for the population and the economy. Hence, based on an inventory of mass movement processes comprising 95 data points, the present study aimed to achieve a zoning of the areas susceptible to these processes, as well as to characterize the mechanisms of instability in the volcanic structures that form the relief of the area in question. The results of this work clearly show the role of the lithology, the mode of emplacement and the morpho–structural characteristics of the volcanic structures, in the types of mass movement processes. In addition, it identifies the diverse activities of anthropogenic origin that favour slope instability in the zone: deforestation and burning of rubbish, felling of timber on the slopes for building infrastructure and dwellings, leakages of water, vibrations of vehicles, rotating machinery and the use of explosives in mining works, overloading the heads of the slopes, disturbance of the geohydrological regime, generation of rubbish tips, terracing of the slopes for cultivation, inadequate building regulations, and the use of counterproductive or ineffectual stabilization measures.

  6. Revealing magma degassing below closed-conduit active volcanoes: Geochemical features of volcanic rocks versus fumarolic fluids at Vulcano (Aeolian Islands, Italy)

    Science.gov (United States)

    Mandarano, Michela; Paonita, Antonio; Martelli, Mauro; Viccaro, Marco; Nicotra, Eugenio; Millar, Ian L.

    2016-04-01

    The elemental and isotopic compositions of noble gases (He, Ne, and Ar) in olivine- and clinopyroxene-hosted fluid inclusions have been measured for rocks at various degrees of evolution and belonging to high-K calcalkaline-shoshonitic and shoshonitic-potassic series in order to cover the entire volcanological history of Vulcano Island (Italy). The major- and trace-element concentrations and the Sr- and Pb-isotope compositions for whole rocks were integrated with data obtained from the fluid inclusions. 3He/4He in fluid inclusions is within the range of 3.30 and 5.94 R/Ra, being lower than the theoretical value for the deep magmatic source expected for Vulcano Island (6.0-6.2 R/Ra). 3He/4He of the magmatic source is almost constant throughout the volcanic history of Vulcano. Integration of the He- and Sr-isotope systematics leads to the conclusion that a decrease in the He-isotope ratio of the rocks is mainly due to the assimilation of 10-25% of a crustal component similar to the Calabrian basement. 3He/4He shows a negative correlation with Sr isotopes except for the last-erupted Vulcanello latites (Punta del Roveto), which have anomalously high He isotope ratios. This anomaly has been attributed to a flushing process by fluids coming from the deepest reservoirs, since an input of deep magmatic volatiles with high 3He/4He values increases the He-isotope ratio without changing 87Sr/86Sr. A comparison of the He-isotope ratios between fluid inclusions and fumarolic gases shows that only the basalts of La Sommata and the latites of Vulcanello have comparable values. Taking into account that the latites of Vulcanello relate to one of the most-recent eruptions at Vulcano (in the 17th century), we infer that the most probable magma which actually feeds the fumarolic emissions is a latitic body that ponded at about 3-3.5 km of depth and is flushed by fluids coming from a deeper and basic magma.

  7. Revealing the magmas degassing below closed-conduit active volcanoes: noble gases in volcanic rocks versus fumarolic fluids at Vulcano (Aeolian Islands, Italy)

    Science.gov (United States)

    Mandarano, Michela; Paonita, Antonio; Martelli, Mauro; Viccaro, Marco; Nicotra, Eugenio; Millar, Ian L.

    2016-04-01

    With the aim to constrain the nature of magma currently feeding the fumarolic field of Vulcano, we measured the elemental and isotopic compositions of noble gases (He, Ne, and Ar) in olivine- and clinopyroxene-hosted fluid inclusions in high-K calcalcaline-shoshonitic and shoshonitic-potassic series so as to cover the entire volcanological history of Vulcano Island (Italy). The major and trace-element concentrations and the Sr- and Pb-isotope compositions for whole rocks were integrated with data obtained from the fluid inclusions. 3He/4He in fluid inclusions is within the range of 3.30 and 5.94 R/Ra, being lower than the value for the deep magmatic source expected for Vulcano Island (6.0-6.2 R/Ra). 3He/4He of the magmatic source is almost constant throughout the volcanic record of Vulcano. Integration of the He- and Sr-isotope systematics leads to the conclusion that a decrease in the He-isotope ratio of the rocks is mainly due to the assimilation of 10-25% of a crustal component similar to the Calabrian basement. 3He/4He shows a negative correlation with Sr isotopes except for the last-emitted Vulcanello latites (Punta del Roveto), which have high He- and Sr-isotope ratios. This anomaly has been attributed to a flushing process by fluids coming from the deepest reservoirs. Indeed, an input of deep magmatic volatiles with high 3He/4He values increases the He-isotope ratio without changing 87Sr/86Sr. A comparison of the He isotope ratios between fluid inclusions and fumarolic gases showed that only the basalts of La Sommata and the latites of Vulcanello have comparable values. Taking into account that the latites of Vulcanello relate to one of the most-recent eruptions at Vulcano (in the 17th century), we infer that that the most probable magma which actually feeds the fumarolic emissions is a latitic body ponding at about 3-3.5 km of depth and flushed by fluids coming from a deeper and basic magma.

  8. Volcanic Alert System (VAS) developed during the (2011-2013) El Hierro (Canary Islands) volcanic process

    Science.gov (United States)

    Ortiz, Ramon; Berrocoso, Manuel; Marrero, Jose Manuel; Fernandez-Ros, Alberto; Prates, Gonçalo; De la Cruz-Reyna, Servando; Garcia, Alicia

    2014-05-01

    In volcanic areas with long repose periods (as El Hierro), recently installed monitoring networks offer no instrumental record of past eruptions nor experience in handling a volcanic crisis. Both conditions, uncertainty and inexperience, contribute to make the communication of hazard more difficult. In fact, in the initial phases of the unrest at El Hierro, the perception of volcanic risk was somewhat distorted, as even relatively low volcanic hazards caused a high political impact. The need of a Volcanic Alert System became then evident. In general, the Volcanic Alert System is comprised of the monitoring network, the software tools for the analysis of the observables, the management of the Volcanic Activity Level, and the assessment of the threat. The Volcanic Alert System presented here places special emphasis on phenomena associated to moderate eruptions, as well as on volcano-tectonic earthquakes and landslides, which in some cases, as in El Hierro, may be more destructive than an eruption itself. As part of the Volcanic Alert System, we introduce here the Volcanic Activity Level which continuously applies a routine analysis of monitoring data (particularly seismic and deformation data) to detect data trend changes or monitoring network failures. The data trend changes are quantified according to the Failure Forecast Method (FFM). When data changes and/or malfunctions are detected, by an automated watchdog, warnings are automatically issued to the Monitoring Scientific Team. Changes in the data patterns are then translated by the Monitoring Scientific Team into a simple Volcanic Activity Level, that is easy to use and understand by the scientists and technicians in charge for the technical management of the unrest. The main feature of the Volcanic Activity Level is its objectivity, as it does not depend on expert opinions, which are left to the Scientific Committee, and its capabilities for early detection of precursors. As a consequence of the El Hierro

  9. Advanced processing of airborne FDEM data for improved imaging of groundwater conduits and sea water layering near Tulum, Mexico

    Science.gov (United States)

    Schiller, Arnulf; Schattauer, Ingrid; Supper, Robert; Motschka, Klaus; Alonso Merediz, Gonzalo; Lopez Tamayo, Alejandro

    2017-04-01

    The study presented herein is part of a series of international research cooperations, started in the year 2006 and still ongoing, which have the general objective to develop and test new approaches of data acquisition and modelling methods for studying a complex ground/seawater regime and its interaction. The study area is located at the Yucatan Peninsula, Mexico, and comprises the northern most part of the Sian Ka'an biosphere reserve, a coastal wetland of international recognition, as well as the town of Tulum and part of the worlds second largest barrier reef. In the subsurface, and below the city, the whole area is nerved by a complex network of underwater caves. The upper most fresh water layer of the karstic aquifer actually represents the only significant fresh water resource in the region. In principle, karst aquifers are characterized by the presence of two distinct flow domains: the limestone matrix and the karst conduits. A flow model of karst aquifers requires detailed, spatially distributed information on the characteristics of the two domains. Electromagnetic methods determining the distribution of the electrical resistivity within the subsurface can provide such information. To explore the applicability of airborne electromagnetics, several airborne surveys in the area were conducted in 2007, 2008, and 2015 by the Geological Survey of Austria, covering an area of some 300 square kilometres in total. Above the reef, data has been acquired along distinct flight lines. Adapted and new processing techniques retrieved increased resolution of apparent electrical resistivity anomalies. These can be interpreted as vast complex conduit network inland partially confirmed by explored cave systems. Consequentely, a 3d-model of the network as well as complex halocline table and further aquifer structures have been derived. Furthermore, advanced processing of offshore lines delivered improved resolution of seawater layering primarily due to variation in

  10. Welding of pyroclastic conduit infill: A mechanism for cyclical explosive eruptions

    Science.gov (United States)

    Kolzenburg, S.; Russell, J. K.

    2014-07-01

    Vulcanian-style eruptions are small- to moderate-sized, singular to cyclical events commonly having volcanic explosivity indices of 1-3. They produce pyroclastic flows, disperse tephra over considerable areas, and can occur as precursors to larger (e.g., Plinian) eruptions. The fallout deposits of the 2360 B.P. eruption of Mount Meager, BC, Canada, contain bread-crusted blocks of welded breccia as accessory lithics. They display a range of compaction/welding intensity and provide a remarkable opportunity to constrain the nature and timescales of mechanical processes operating within explosive volcanic conduits during repose periods between eruptive cycles. We address the deformation and porosity/permeability reduction within natural pyroclastic deposits infilling volcanic conduits. We measure the porosity, permeability, and ultrasonic wave velocities for a suite of samples and quantify the strain recorded by pumice clasts. We explore the correlations between the physical properties and deformation fabric. Based on these correlations, we reconstruct the deformation history within the conduit, model the permeability reduction timescales, and outline the implications for the repressurization of the volcanic conduit. Our results highlight a profound directionality in the measured physical properties of these samples related to the deformation-induced fabric. Gas permeability varies drastically with increasing strain and decreasing porosity along the compaction direction of the fabric but varies little along the elongation direction of the fabric. The deformation fabric records a combination of compaction within the conduit and postcompaction stretching associated with subsequent eruption. Model timescales of these processes are in good agreement with repose periods of cyclic vulcanian eruptions.

  11. The Icelandic volcanic aeolian environment: Processes and impacts - A review

    Science.gov (United States)

    Arnalds, Olafur; Dagsson-Waldhauserova, Pavla; Olafsson, Haraldur

    2016-03-01

    Iceland has the largest area of volcaniclastic sandy desert on Earth or 22,000 km2. The sand has been mostly produced by glacio-fluvial processes, leaving behind fine-grained unstable sediments which are later re-distributed by repeated aeolian events. Volcanic eruptions add to this pool of unstable sediments, often from subglacial eruptions. Icelandic desert surfaces are divided into sand fields, sandy lavas and sandy lag gravel, each with separate aeolian surface characteristics such as threshold velocities. Storms are frequent due to Iceland's location on the North Atlantic Storm track. Dry winds occur on the leeward sides of mountains and glaciers, in spite of the high moisture content of the Atlantic cyclones. Surface winds often move hundreds to more than 1000 kg m-1 per annum, and more than 10,000 kg m-1 have been measured in a single storm. Desertification occurs when aeolian processes push sand fronts and have thus destroyed many previously fully vegetated ecosystems since the time of the settlement of Iceland in the late ninth century. There are about 135 dust events per annum, ranging from minor storms to >300,000 t of dust emitted in single storms. Dust production is on the order of 30-40 million tons annually, some traveling over 1000 km and deposited on land and sea. Dust deposited on deserts tends to be re-suspended during subsequent storms. High PM10 concentrations occur during major dust storms. They are more frequent in the wake of volcanic eruptions, such as after the Eyjafjallajökull 2010 eruption. Airborne dust affects human health, with negative effects enhanced by the tubular morphology of the grains, and the basaltic composition with its high metal content. Dust deposition on snow and glaciers intensifies melting. Moreover, the dust production probably also influences atmospheric conditions and parameters that affect climate change.

  12. Volcanic alert system (VAS) developed during the 2011-2014 El Hierro (Canary Islands) volcanic process

    Science.gov (United States)

    García, Alicia; Berrocoso, Manuel; Marrero, José M.; Fernández-Ros, Alberto; Prates, Gonçalo; De la Cruz-Reyna, Servando; Ortiz, Ramón

    2014-06-01

    The 2011 volcanic unrest at El Hierro Island illustrated the need for a Volcanic Alert System (VAS) specifically designed for the management of volcanic crises developing after long repose periods. The VAS comprises the monitoring network, the software tools for analysis of the monitoring parameters, the Volcanic Activity Level (VAL) management, and the assessment of hazard. The VAS presented here focuses on phenomena related to moderate eruptions, and on potentially destructive volcano-tectonic earthquakes and landslides. We introduce a set of new data analysis tools, aimed to detect data trend changes, as well as spurious signals related to instrumental failure. When data-trend changes and/or malfunctions are detected, a watchdog is triggered, issuing a watch-out warning (WOW) to the Monitoring Scientific Team (MST). The changes in data patterns are then translated by the MST into a VAL that is easy to use and understand by scientists, technicians, and decision-makers. Although the VAS was designed specifically for the unrest episodes at El Hierro, the methodologies may prove useful at other volcanic systems.

  13. Volcanic edifice weakening via decarbonation: A self-limiting process?

    Science.gov (United States)

    Mollo, Silvio; Heap, Michael J.; Iezzi, Gianluca; Hess, Kai-Uwe; Scarlato, Piergiorgio; Dingwell, Donald B.

    2012-08-01

    The inherent instability of volcanic edifices, and their resultant propensity for catastrophic collapse, is a constant source of volcanic risk. Structural instability of volcanic edifices may be amplified by the presence of carbonate rocks in the sub-volcanic strata, due to the debilitating response of carbonates to thermally-induced alteration. Nonetheless, decarbonation reactions (the primary weakening mechanism), may stall when the system becomes buffered by rising levels of a reaction product, carbon dioxide. Such thermodynamic stalling might be inferred to serve to circumvent the weakness of volcanic structures. However, the present study shows that, even when decarbonation is halted, rock physical properties continue to degrade due to thermal microcracking. Furthermore, as a result, the pathways for the escape of carbon dioxide are numerous within a volcanic edifice. Therefore, in the case of an edifice with a sub-volcanic sedimentary basement, the generation of carbon dioxide via decarbonation is unlikely to hinder its impact on instability, and thus potentially devastating flank collapse.

  14. Cryovolcanic Conduit Evolution and Eruption on Icy Satellites

    Science.gov (United States)

    Mitchell, K. L.

    2014-12-01

    In silicate volcanism, such as on Earth or Io, eruptions typically result from fracture formation caused by interaction of tectonic stresses with inflating, pressurized magma sources, leading to transport of melt through an evolving conduit. On icy satellites the paradigm may be similar, resulting from some combination of tidal stresses and expansion of freezing water within, or near the base of, an ice shell. Such a fracture will result in eruption if mass continuity can be established, with buoyancy aided by exsolution and expansion of dissolved volatiles. After onset, conduit shape evolves due to: (1) shear-stresses or frictional erosional; (2) wallrock "bursting" due to massive wall stresses; (3) wall melting or condensation of particles due to heat transfer; or (4) changes in applied stresses. Preliminary thermodynamic and fluid mechanical analysis suggests some initial cooling during ascent resulting from exsolution and expansion of volatiles, thermally buffered by freezing, Conduit contraction may occur, and so evolution towards a deep, gas-filled plume chamber is difficult to accommodate without evoking a co-incidental process. Conduit flaring occurs near the surface where velocities are greatest, enhancing erosion. Here, viscous dissipative heating exceeds adiabatic cooling, and so some boiling (a few wt%) may occur. In contrast with silicate volcanism, decompression to below the triple point will occur within conduit, vent or jet, resulting in rapid freezing and boiling of the remaining water at a 6.8:1 ratio. Subsequent isentropic or adiabatic expansion within erupting jets may result in a few percent net of condensation or sublimation. These effects combined lead to ~4:1-7:1 solid:vapor ratios in the jet for most eruption conditions. These figures are consistent with the ~6:1 inferred in Enceladus' jets, supporting the hypothesis that the Enceladus plume draws from a subsurface body of liquids through a conduit. Similar results are anticipated if

  15. Gas slug ascent through rheologically stratified conduits

    Science.gov (United States)

    Capponi, Antonio; James, Mike R.; Lane, Steve J.

    2016-04-01

    Textural and petrological evidence has indicated the presence of viscous, degassed magma layers at the top of the conduit at Stromboli. This layer acts as a plug through which gas slugs burst and it is thought to have a role in controlling the eruptive dynamics. Here, we present the results of laboratory experiments which detail the range of slug flow configurations that can develop in a rheologically stratified conduit. A gas slug can burst (1) after being fully accommodated within the plug volume, (2) whilst its base is still in the underlying low-viscosity liquid or (3) within a low-viscosity layer dynamically emplaced above the plug during the slug ascent. We illustrate the relevance of the same flow configurations at volcanic-scale through a new experimentally-validated 1D model and 3D computational fluid dynamic simulations. Applied to Stromboli, our results show that gas volume, plug thickness, plug viscosity and conduit radius control the transition between each configuration; in contrast, the configuration distribution seems insensitive to the viscosity of magma beneath the plug, which acts mainly to deliver the slug into the plug. Each identified flow configuration encompasses a variety of processes including dynamic narrowing and widening of the conduit, generation of instabilities along the falling liquid film, transient blockages of the slug path and slug break-up. All these complexities, in turn, lead to variations in the slug overpressure, mirrored by changes in infrasonic signatures which are also associated to different eruptive styles. Acoustic amplitudes are strongly dependent on the flow configuration in which the slugs burst, with both acoustic peak amplitudes and waveform shapes reflecting different burst dynamics. When compared to infrasonic signals from Stromboli, the similarity between real signals and laboratory waveforms suggests that the burst of a slug through a plug may represent a viable first-order mechanism for the generation of

  16. The tropospheric processing of acidic gases and hydrogen sulphide in volcanic gas plumes as inferred from field and model investigations

    Directory of Open Access Journals (Sweden)

    A. Aiuppa

    2007-01-01

    Full Text Available Improving the constraints on the atmospheric fate and depletion rates of acidic compounds persistently emitted by non-erupting (quiescent volcanoes is important for quantitatively predicting the environmental impact of volcanic gas plumes. Here, we present new experimental data coupled with modelling studies to investigate the chemical processing of acidic volcanogenic species during tropospheric dispersion. Diffusive tube samplers were deployed at Mount Etna, a very active open-conduit basaltic volcano in eastern Sicily, and Vulcano Island, a closed-conduit quiescent volcano in the Aeolian Islands (northern Sicily. Sulphur dioxide (SO2, hydrogen sulphide (H2S, hydrogen chloride (HCl and hydrogen fluoride (HF concentrations in the volcanic plumes (typically several minutes to a few hours old were repeatedly determined at distances from the summit vents ranging from 0.1 to ~10 km, and under different environmental conditions. At both volcanoes, acidic gas concentrations were found to decrease exponentially with distance from the summit vents (e.g., SO2 decreases from ~10 000 μg/m3at 0.1 km from Etna's vents down to ~7 μg/m3 at ~10 km distance, reflecting the atmospheric dilution of the plume within the acid gas-free background troposphere. Conversely, SO2/HCl, SO2/HF, and SO2/H2S ratios in the plume showed no systematic changes with plume aging, and fit source compositions within analytical error. Assuming that SO2 losses by reaction are small during short-range atmospheric transport within quiescent (ash-free volcanic plumes, our observations suggest that, for these short transport distances, atmospheric reactions for H2S and halogens are also negligible. The one-dimensional model MISTRA was used to simulate quantitatively the evolution of halogen and sulphur compounds in the plume of Mt. Etna. Model predictions support the hypothesis of minor HCl chemical processing during plume transport, at least in cloud-free conditions. Larger

  17. Crustal deformation and magmatic processes at Laguna del Maule volcanic field (Chile): Geodetic measurements and numerical models

    Science.gov (United States)

    Le Mével, Hélène

    The Laguna del Maule (LdM) volcanic field in Chile is an exceptional example of postglacial rhyolitic volcanism in the Southern Volcanic Zone of the Andes. Since 2007, LdM has experienced an unrest episode characterized by high rates of deformation measured by interferometric analysis of synthetic aperture radar (SAR) images acquired between 2007 and 2016, and data from the Global Positioning System (GPS) recorded since 2012 at five stations. The inflating region includes most of the 16--km-by--14--km ring of rhyolitic domes and coulees. The fastest-moving GPS station (MAU2) has a velocity vector of [[special character omited]72 +/- 4, 19 +/- 1, 194 +/- 3] mm/yr between 2012 and 2016 for the eastward, northward, and upward components, respectively. First, we model the InSAR observations assuming a rectangular dislocation in a half space with uniform elastic properties. The best time function for modeling the InSAR data set is a double exponential model with rates increasing from 2007 through 2010 and decreasing slowly since 2011. Modeling of historical uplift at Yellowstone, Long Valley, and Three Sisters volcanic fields suggests a common temporal evolution of vertical displacement rates. We hypothesize that magma intruding into an existing silicic magma reservoir is driving the surface deformation and present a new dynamic model to describe this process. A Newtonian fluid characterized by its viscosity, density, and pressure flows through a vertical conduit, intruding into a reservoir embedded in an elastic domain and leading to time-dependent surface deformation. Using a grid-search optimization, we minimize the misfit to the InSAR displacement data by varying the three parameters governing the analytical solution: the characteristic timescale tauP for magma propagation, the injection pressure, and the inflection time when the acceleration switches from positive to negative. For a spheroid with semi-major axis a = 6200 m, semi-minor axis c = 100 m, located at a

  18. A model of bubble growth leading to xylem conduit embolism.

    Science.gov (United States)

    Hölttä, T; Vesala, T; Nikinmaa, E

    2007-11-01

    The dynamics of a gas bubble inside a water conduit after a cavitation event was modeled. A distinction was made between a typical angiosperm conduit with a homogeneous pit membrane and a typical gymnosperm conduit with a torus-margo pit membrane structure. For conduits with torus-margo type pits pit membrane deflection was also modeled and pit aspiration, the displacement of the pit membrane to the low pressure side of the pit chamber, was found to be possible while the emboli was still small. Concurrent with pit aspiration, the high resistance to water flow out of the conduit through the cell walls or aspirated pits will make the embolism process slow. In case of no pit aspiration and always for conduits with homogeneous pit membranes, embolism growth is more rapid but still much slower than bubble growth in bulk water under similar water tension. The time needed for the embolism to fill a whole conduit was found to be dependent on pit and cell wall conductance, conduit radius, xylem water tension, pressure rise in adjacent conduits due to water freed from the embolising conduit, and the rigidity and structure of the pits in the case of margo-torus type pit membrane. The water pressure in the conduit hosting the bubble was found to occur almost immediately after bubble induction inside a conduit, creating a sudden tension release in the conduit, which can be detected by acoustic and ultra-acoustic monitoring of xylem cavitation.

  19. Gas slug ascent through changes in conduit diameter: Laboratory insights into a volcano-seismic source process in low-viscosity magmas

    Science.gov (United States)

    James, M.R.; Lane, S.J.; Chouet, B.A.

    2006-01-01

    Seismic signals generated during the flow and degassing of low-viscosity magmas include long-period (LP) and very-long-period (VLP) events, whose sources are often attributed to dynamic fluid processes within the conduit. We present the results of laboratory experiments designed to investigate whether the passage of a gas slug through regions of changing conduit diameter could act as a suitable source mechanism. A vertical, liquid-filled glass tube featuring a concentric diameter change was used to provide canonical insights into potentially deep or shallow seismic sources. As gas slugs ascend the tube, we observe systematic pressure changes varying with slug size, liquid depth, tube diameter, and liquid viscosity. Gas slugs undergoing an abrupt flow pattern change upon entering a section of significantly increased tube diameter induce a transient pressure decrease in and above the flare and an associated pressure increase below it, which stimulates acoustic and inertial resonant oscillations. When the liquid flow is not dominantly controlled by viscosity, net vertical forces on the apparatus are also detected. The net force is a function of the magnitude of the pressure transients generated and the tube geometry, which dictates where, and hence when, the traveling pressure pulses can couple into the tube. In contrast to interpretations of related volcano-seismic data, where a single downward force is assumed to result from an upward acceleration of the center of mass in the conduit, our experiments suggest that significant downward forces can result from the rapid deceleration of relatively small volumes of downward-moving liquid. Copyright 2006 by the American Geophysical Union.

  20. Gastric conduit perforation.

    Science.gov (United States)

    Patil, Nilesh; Kaushal, Arvind; Jain, Amit; Saluja, Sundeep Singh; Mishra, Pramod Kumar

    2014-08-16

    As patients with carcinoma of the esophagus live longer, complications associated with the use of a gastric conduit are increasing. Ulcers form in the gastric conduit in 6.6% to 19.4% of patients. There are a few reports of perforation of a gastric conduit in the English literature. Almost all of these were associated with serious complications. We report a patient who developed a tension pneumothorax consequent to spontaneous perforation of an ulcer in the gastric conduit 7 years after the index surgery in a patient with carcinoma of the gastroesophageal junction. He responded well to conservative management. Complications related to a gastric conduit can be because of multiple factors. Periodic endoscopic surveillance of gastric conduits should be considered as these are at a higher risk of ulcer formation than a normal stomach. Long term treatment with proton pump inhibitors may decrease complications. There are no guidelines for the treatment of a perforated gastric conduit ulcer and the management should be individualized.

  1. Volcanic Processes and Geology of Augustine Volcano, Alaska

    Science.gov (United States)

    Waitt, Richard B.; Beget, James E.

    2009-01-01

    Augustine Island (volcano) in lower Cook Inlet, Alaska, has erupted repeatedly in late-Holocene and historical times. Eruptions typically beget high-energy volcanic processes. Most notable are bouldery debris avalanches containing immense angular clasts shed from summit domes. Coarse deposits of these avalanches form much of Augustine's lower flanks. A new geologic map at 1:25,000 scale depicts these deposits, these processes. We correlate deposits by tephra layers calibrated by many radiocarbon dates. Augustine Volcano began erupting on the flank of a small island of Jurassic clastic-sedimentary rock before the late Wisconsin glaciation (late Pleistocene). The oldest known effusions ranged from olivine basalt explosively propelled by steam, to highly explosive magmatic eruptions of dacite or rhyodacite shed as pumice flows. Late Wisconsin piedmont glaciers issuing from the mountainous western mainland surrounded the island while dacitic eruptive debris swept down the south volcano flank. Evidence is scant for eruptions between the late Wisconsin and about 2,200 yr B.P. On a few south-flank inliers, thick stratigraphically low pumiceous pyroclastic-flow and fall deposits probably represent this period from which we have no radiocarbon dates on Augustine Island. Eruptions between about 5,350 and 2,200 yr B.P. we know with certainty by distal tephras. On Shuyak Island 100 km southeast of Augustine, two distal fall ashes of Augustinian chemical provenance (microprobe analysis of glass) date respectively between about 5,330 and 5,020 yr B.P. and between about 3,620 and 3,360 yr B.P. An Augustine ash along Kamishak Creek 70 km southwest of Augustine dates between about 3,850 and 3,660 yr B.P. A probably Augustinian ash lying within peat near Homer dates to about 2,275 yr B.P. From before 2,200 yr B.P. to the present, Augustine eruptive products abundantly mantle the island. During this period, numerous coarse debris avalanches swept beyond Augustine's coast, most

  2. The grain-size distribution of pyroclasts: Primary fragmentation, conduit sorting or abrasion?

    Science.gov (United States)

    Kueppers, U.; Schauroth, J.; Taddeucci, J.

    2013-12-01

    Explosive volcanic eruptions expel a mixture of pyroclasts and lithics. Pyroclasts, fragments of the juvenile magma, record the state of the magma at fragmentation in terms of porosity and crystallinity. The grain size distribution of pyroclasts is generally considered to be a direct consequence of the conditions at magma fragmentation that is mainly driven by gas overpressure in bubbles, high shear rates, contact with external water or a combination of these factors. Stress exerted by any of these processes will lead to brittle fragmentation by overcoming the magma's relaxation timescale. As a consequence, most pyroclasts exhibit angular shapes. Upon magma fragmentation, the gas pyroclast mixture is accelerated upwards and eventually ejected from the vent. The total grain size distribution deposited is a function of fragmentation conditions and transport related sorting. Porous pyroclasts are very susceptible to abrasion by particle-particle or particle-conduit wall interaction. Accordingly, pyroclastic fall deposits with angular clasts should proof a low particle abrasion upon contact to other surfaces. In an attempt to constrain the degree of particle interaction during conduit flow, monomodal batches of washed pyroclasts have been accelerated upwards by rapid decompression and subsequently investigated for their grain size distribution. In our set-up, we used a vertical cylindrical tube without surface roughness as conduit. We varied grain size (0.125-0.25; 0.5-1; 1-2 mm), porosity (0; 10; 30 %), gas-particle ratio (10 and 40%), conduit length (10 and 28 cm) and conduit diameter (2.5 and 6 cm). All ejected particles were collected after settling at the base of a 3.3 m high tank and sieved at one sieve size below starting size (half-Φ). Grain size reduction showed a positive correlation with starting grain size, porosity and overpressure at the vent. Although milling in a volcanic conduit may take place, porous pyroclasts are very likely to be a primary product

  3. Catastrophic volcanism

    Science.gov (United States)

    Lipman, Peter W.

    1988-01-01

    Since primitive times, catastrophes due to volcanic activity have been vivid in the mind of man, who knew that his activities in many parts of the world were threatened by lava flows, mudflows, and ash falls. Within the present century, increasingly complex interactions between volcanism and the environment, on scales not previously experienced historically, have been detected or suspected from geologic observations. These include enormous hot pyroclastic flows associated with collapse at source calderas and fed by eruption columns that reached the stratosphere, relations between huge flood basalt eruptions at hotspots and the rifting of continents, devastating laterally-directed volcanic blasts and pyroclastic surges, great volcanic-generated tsunamis, climate modification from volcanic release of ash and sulfur aerosols into the upper atmosphere, modification of ocean circulation by volcanic constructs and attendent climatic implications, global pulsations in intensity of volcanic activity, and perhaps triggering of some intense terrestrial volcanism by planetary impacts. Complex feedback between volcanic activity and additional seemingly unrelated terrestrial processes likely remains unrecognized. Only recently has it become possible to begin to evaluate the degree to which such large-scale volcanic processes may have been important in triggering or modulating the tempo of faunal extinctions and other evolutionary events. In this overview, such processes are examined from the viewpoint of a field volcanologist, rather than as a previous participant in controversies concerning the interrelations between extinctions, impacts, and volcanism.

  4. Huygens Crater: Insights into Noachian Volcanism, Stratigraphy, and Aqueous Processes

    Science.gov (United States)

    Ackiss, S. E.; Wray, J. J.; Seelos, K. D.; Niles, P. B.

    2015-01-01

    Huygens crater is a well preserved peak ring structure on Mars centered at 13.5 deg S, 55.5 deg E in the Noachian highlands between Terras Tyrrhena and Sabaea near the NW rim of Hellas basin. With a diameter of approximately 470 km, it uplifted and exhumed pre-Noachian crustal materials from depths greater than 25 km, penetrating below the thick, ubiquitous layer of Hellas ejecta. In addition, Huygens served as a basin for subsequent aqueous activity, including erosion/deposition by fluvial valley networks and subsurface alteration that is now exposed by smaller impacts. Younger mafic-bearing plains that partially cover the basin floor and surrounding intercrater areas were likely emplaced by later volcanism.

  5. GRID based Thermal Images Processing for volcanic activity monitoring

    Science.gov (United States)

    Mangiagli, S.; Coco, S.; Drago, L.; Laudani, A.,; Lodato, L.; Pollicino, G.; Torrisi, O.

    2009-04-01

    Since 2001, the Catania Section of the National Institute of Geophysics and Volcanology (INGV) has been running the video stations recording the volcanic activity of Mount Etna, Stromboli and the Fossa Crater of Vulcano island. The video signals of 11 video cameras (seven operating in the visible band and four in infrared) are sent in real time to INGV Control Centre where they are visualized on monitors and archived on a dedicated NAS storage. The video surveillance of the Sicilian volcanoes, situated near to densely populated areas, helps the volcanologists providing the Civil Protection authorities with updates in real time on the on-going volcanic activity. In particular, five video cameras are operating on Mt. Etna and they record the volcano from the south and east sides 24 hours a day. During emergencies, mobile video stations may also be used to better film the most important phases of the activity. Single shots are published on the Catania Section intranet and internet websites. On June 2006 a A 40 thermal camera was installed in Vulcano La Fossa Crater. The location was in the internal and opposite crater flank (S1), 400 m distant from the fumarole field. The first two-year of data on temperature distribution frequency were recorded with this new methodology of acquisition, and automatically elaborated by software at INGV Catania Section. In fact a dedicated software developed in IDL, denominated Volcano Thermo Analysis (VTA), was appositely developed in order to extract a set of important features, able to characterize with a good approssimation the volcanic activity. In particular the program first load and opportunely convert the thermal images, then according to the Region Of Interest (ROI) and the temperature ranges defined by the user provide to automatic spatial and statistic analysis. In addition the VTA is able to analysis all the temporal series of images available in order to achieve the time-event analysis and the dynamic of the volcanic

  6. Magma chamber processes in central volcanic systems of Iceland

    DEFF Research Database (Denmark)

    Þórarinsson, Sigurjón Böðvar; Tegner, Christian

    2009-01-01

    New field work and petrological investigations of the largest gabbro outcrop in Iceland, the Hvalnesfjall gabbro of the 6-7 Ma Austurhorn intrusive complex, have established a stratigraphic sequence exceeding 800 m composed of at least 8 macrorhythmic units. The bases of the macrorhythmic units......3 of clinopyroxene and magnetite indicative of magma replenishment. Some macrorhythmic units show mineral trends indicative of up-section fractional crystallisation over up to 100 m, whereas others show little variation. Two populations of plagioclase crystals (large, An-rich and small, less An...... olivine basalts from Iceland that had undergone about 20% crystallisation of olivine, plagioclase and clinopyroxene and that the macrorhythmic units formed from thin magma layers not exceeding 200-300 m. Such a "mushy" magma chamber is akin to volcanic plumbing systems in settings of high magma supply...

  7. Understanding the initiation and development of explosive Plinian eruptions: the conduit processes, eruption dynamics and dispersal processes of the ignimbrite and caldera-forming Lower Pumice 1 (184 ka) and Lower Pumice 2 (172 ka) eruptions, Santorini Caldera, Greece

    OpenAIRE

    Simmons, Jack Michael

    2017-01-01

    In this thesis, the internal stratigraphy, facies, and facies architecture of the rhyodacitic 184 ka Lower Pumice 1 (LP1) and 172 ka Lower Pumice 2 (LP2) eruption sequences, erupted from Santorini Caldera, Greece, are reassessed as the basis for understanding the initiation and development of caldera-forming Plinian eruptions, including the changing conditions of the magmatic system, the conduit and eruption processes, the transition between eruption phases and ultimately the evolution of the...

  8. Volcanic rock properties control sector collapse events

    Science.gov (United States)

    Hughes, Amy; Kendrick, Jackie; Lavallée, Yan; Hornby, Adrian; Di Toro, Giulio

    2017-04-01

    Volcanoes constructed by superimposed layers of varying volcanic materials are inherently unstable structures. The heterogeneity of weak and strong layers consisting of ash, tephra and lavas, each with varying coherencies, porosities, crystallinities, glass content and ultimately, strength, can promote volcanic flank and sector collapses. These volcanoes often exist in areas with complex regional tectonics adding to instability caused by heterogeneity, flank overburden, magma movement and emplacement in addition to hydrothermal alteration and anomalous geothermal gradients. Recent studies conducted on the faulting properties of volcanic rocks at variable slip rates show the rate-weakening dependence of the friction coefficients (up to 90% reduction)[1], caused by a wide range of factors such as the generation of gouge and frictional melt lubrication [2]. Experimental data from experiments conducted on volcanic products suggests that frictional melt occurs at slip rates similar to those of plug flow in volcanic conduits [1] and the bases of mass material movements such as debris avalanches from volcanic flanks [3]. In volcanic rock, the generation of frictional heat may prompt the remobilisation of interstitial glass below melting temperatures due to passing of the glass transition temperature at ˜650-750 ˚C [4]. In addition, the crushing of pores in high porosity samples can lead to increased comminution and strain localisation along slip surfaces. Here we present the results of friction tests on both high density, glass rich samples from Santaguito (Guatemala) and synthetic glass samples with varying porosities (0-25%) to better understand frictional properties underlying volcanic collapse events. 1. Kendrick, J.E., et al., Extreme frictional processes in the volcanic conduit of Mount St. Helens (USA) during the 2004-2008 eruption. J. Structural Geology, 2012. 2. Di Toro, G., et al., Fault lubrication during earthquakes. Nature, 2011. 471(7339): p. 494-498. 3

  9. Deducing the magma chamber processes of middle Eocene volcanics, Sivas and Tokat regions; NE Turkey: Insights from clinopyroxene chemistry

    Science.gov (United States)

    Göçmengil, Gönenç; Karacık, Zekiye; Genç, Ş. Can; Prelevic, Dejan

    2016-04-01

    Middle Eocene Tokat and Sivas volcanic successions occur within the İzmir-Ankara-Erzincan suture zone. Different models are suggested for the development of the middle Eocene volcanism such as post-collisional, delamination and slab-breakoff models as well as the arc magmatism. In both areas, volcanic units cover all the basement units with a regional disconformity and comprise lavas spanning a compositional range from mainly basalt-basaltic andesite to a lesser amount trachyte. Here, we report mineral chemistry of different basaltic lavas through transect from northern continent (Tokat region, Pontides) to southern continent (Sivas region, Kırşehir block) to deduce the characteristics of the magma chamber processes which are active during the middle Eocene. Basaltic lavas include olivine bearing basalts (Ol-basalt: ± olivine + clinopyroxene + plagioclase); amphibole bearing basaltic andesite (Amp-basaltic andesite: amphibole + clinopyroxene + plagioclase ± biotite) and pyroxene bearing basaltic andesite (Px-basaltic andesite: clinopyroxene + plagioclase). Microlitic, glomeroporphyric and pilotaxitic texture are common. Clinopyroxene phenocrystals (macro ≥ 750 μm and micro ≤300 μm) are common in all three lava series which are investigated by transecting core to rim compositional profiles. They are generally augite and diopside; euhedral to subhedral in shape with oscillatory, normal and reverse zoning patterns. Also, all clinopyroxene phenocrystals are marked by moderately high Mg# (for Ol-basalt: 67-91; avg. 80; Amp-basaltic andesite: 76-83, avg: 80; Px -basaltic andesite 68-95, avg: 81). In Ol-basalt, clinopyroxene phenocrystals show normal zonation (high Mg# cores and low Mg# rims). In Amp-basaltic andesite, clinopyroxenes are generally homogenous in composition with minor variation of Mg# towards the rims. On the contrary, in Px-basaltic andesite, clinopyroxene macro phenocrystals show reverse zonation with the core with low Mg# and the rims with

  10. Friction in volcanic environments

    Science.gov (United States)

    Kendrick, Jackie E.; Lavallée, Yan

    2016-04-01

    Volcanic landscapes are amongst the most dynamic on Earth and, as such, are particularly susceptible to failure and frictional processes. In rocks, damage accumulation is frequently accompanied by the release of seismic energy, which has been shown to accelerate in the approach to failure on both a field and laboratory scale. The point at which failure occurs is highly dependent upon strain-rate, which also dictates the slip-zone properties that pertain beyond failure, in scenarios such as sector collapse and pyroclastic flows as well as the ascent of viscous magma. High-velocity rotary shear (HVR) experiments have provided new opportunities to overcome the grand challenge of understanding faulting processes during volcanic phenomena. Work on granular ash material demonstrates that at ambient temperatures, ash gouge behaves according to Byerlee's rule at low slip velocities, but is slip-weakening, becoming increasingly lubricating as slip ensues. In absence of ash along a slip plane, rock-rock friction induces cataclasis and heating which, if sufficient, may induce melting (producing pseudotachylyte) and importantly, vesiculation. 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 shear-thinning behaviour and viscoelasticity of frictional melts yield a tendency for extremely unstable slip, and occurrence of frictional melt fragmentation. This velocity-dependence acts as an important feedback mechanism on the slip plane, in addition to the bulk composition, mineralogy and glass content of the magma, that all influence frictional behaviour. During sector collapse events and in pyroclastic density currents it is the frictional properties of the rocks and ash that, in-part, control the run-out distance and associated risk. In addition, friction plays an important role in the eruption of viscous magmas: In the conduit, the rheology of magma is integral

  11. Carbothermal reduction process of silica formed from shirasu volcanic ash using solar furnace

    Directory of Open Access Journals (Sweden)

    Hatakeyama Keisuke

    2016-01-01

    Full Text Available Metallurgical grade silicon was formed using Shirasu volcanic ash as starting material with solar furnace. The solar furnace was composed of two parts: Fresnel lens and reacting furnace. The reacting furnace was composed of a cylindrical vacuum chamber and quartz glass plate functioning to guide the concentrated sunlight into the furnace, and was placed at the focal point of the Fresnel lens. The sample was made from a mixture of silica formed from Shirasu volcanic ash and carbon, and placed in the carbon crucible inside the reacting furnace. The sample was irradiated for 3 hours, and the furnace was left until it cooled down to room temperature. After the cooling process, the sample was mixed and placed in the carbon crucible, and it was irradiated and cooled with the same processes again. After the experiment, the sample was evaluated by X-ray diffraction and the production of silicon was confirmed.

  12. Quantitative studies of volcanic processes on Mars using data from the Mars Global Surveyor

    Science.gov (United States)

    Bishop, Louise Jane

    Volcanic processes on Mars were investigated using topographic profiles derived with the help of IDL software from data collected by the Mars Orbiter Laser Altimeter (MOLA) on the Mars Global Surveyor Mission (MGS) in 1997-2001 and images obtained by the MGS Mars Orbiter Camera (MOC) and by the earlier Viking mission. Thickness and slope values for lava flows at both Elysium Mons and Alba Patera made it possible to compute flow emplacement times and effusion rates using the flow growth model proposed by C. R. J. Kilburn and R. M. C Lopes in 1990. Geological mapping of the Elysium volcanic region showed that Elysium Mons was emplaced as a result of a single shift in vent position on top of an older volcanic edifice, here termed the Ancient Volcanic Edifice (AVE). This implies that there have been substantial variations in both position and time for the magma supply. Calculations suggest that the flows at Alba Patera were emplaced more quickly than those at Elysium Mons, possibly owing to differences in fissure width and lava composition. There is evidence for both aa and pahoehoe on the summit areas of Elysium Mons and Alba Patera. The presence of aa is consistent with the view that long lava flows on Mars are emplaced quickly. Pahoehoe flows imply slow emplacement, and their inferred presence on Mars provides support for the theory that long terrestrial lavas are often emplaced as sheets of inflated pahoehoe. MOC image analysis indicated that late-stage explosive activity has occurred at several Martian volcanoes where it was previously undetected, contrary to the prevalent view that Martian volcanism evolves from explosive to effusive activity. To resolve the many ambiguities inherent in morphological data and imagery the need remains for ground truthing by experienced observers and detailed geochemical analyses in situ or by means of a sample return mission

  13. Domes and Flows: Do Temporal Trends in Dacitic Magma Chemistry and Rheological Behavior at Santiaguito, Guatemala, Reflect Magma Chamber or Conduit Processes?

    Science.gov (United States)

    Avard, G.; Whittington, A.; Rose, W.; Matias, O.; Cornejo, J.

    2006-12-01

    Santiaguito is a dacitic dome complex growing in the crater left by the 1902 plinian eruption of the stratovolcano Santa Maria, in Guatemala. The domes began growing in 1922 and are still active, with frequent small ash and steam eruptions, and semi-continous extrusion of crystal-rich dacitic lava both as spines on the domes (endogenous growth) and slow-moving block-lava "stealth" flows (exogenous growth). All four vents have produced both domes and flows, and at times multiple vents have been active. Between 1999 and 2004, one flow reached a length of 4 km. New flows emerged from the same vent in 2004 and 2005-2006 (ongoing). Flow morphology is controlled by rheology, which in turn depends on lava composition, crystal content, and volatile content. Samples of flows erupted from 1987 to the present share many features, including a phenocryst population dominated by complexly zoned plagioclase, a micro-crystalline plagioclase-rich rhyolitic groundmass, and a complete absence of hydrous phases. Small amphibole crystals with thick oxide rims are found only in samples more than 30 years old. Bulk-rock chemical analyses confirm a decrease in magma SiO2 content, from 63.5 - 66 wt.% before 1980, to 61 - 63 wt.% today. It has been suggested that this decreasing SiO2 content reflects the tapping of deeper and hotter magma; the lack of amphibole indicates that it must also be drier. From these preliminary results, we infer that magma chemistry is probably dictated by long time-scale changes in the magma chamber, while eruptive style is probably controlled by phenocryst content, matrix volatile content and microlite growth, which owe more to ascent dynamics and conduit processes than the parental magma. The lack of a direct correlation between bulk magma chemistry and extrusive style may also apply to other dacitic volcanoes such as Mount Saint Helens, suggesting that they also have the potential to produce kilometer-long flows if changes occur to the conduit system.

  14. The textural record of conduit and syn-eruptive degassing preserved in ballistic bombs from cyclic Vulcanian explosions of Galeras volcano, Colombia

    Science.gov (United States)

    Bain, A. A.

    2015-12-01

    Volcanic bombs preserve textural data that record conduit conditions as well as syn-eruptive processes that acted upon a parcel of magma following decompression. Specifically, these pyroclasts may record several episodes of crystal and bubble growth, as well as bubble coalescence and collapse. Furthermore, bombs retrieved from sequential eruptions provide valuable insight into the unobservable evolution of a volcanic conduit over time. We present results from a morphological and textural study of vesicle size distributions in ballistic bombs from six Vulcanian eruptions from the 2004-2012 period of activity of Galeras volcano, Colombia. These violent eruptions cyclically destroyed and ejected a stalled, degassed and crystal-rich plug and a limited amount of underlying magma. They were followed by resumption of the slow rise of magma in the shallow conduit, accompanied by redevelopment of a plug and the perpetuation of a hazardous cycle. We find that bombs from these eruptions fall into three morphological classes including dense bombs, breadcrusted bombs and vesicular bombs based on the existence or absence of a primary quenched rind and comparison of the interior and exterior vesicularities. We study vesicle populations using image analysis of SEM images followed by stereological conversion to reconstruct the degassing history of each pyroclast. The results of this study will be used to produce a quantitative model of the evolution of porosity, permeability and degassing in the upper conduit of Galeras volcano during the 2004-2012 eruptive episode.

  15. Linking magma reservoir processes to the frequency and magnitude of volcanic eruptions

    Science.gov (United States)

    Sheldrake, Tom; Caricchi, Luca

    2016-04-01

    The frequency of volcanic eruptions is fundamentally related to processes controlling the accumulation of eruptible magma at depth and the pressurisation of the magmatic reservoir. Here we present a combined statistical-empirical approach to link the frequency and magnitude of volcanic eruptions observed in different arcs to important parameters controlling the growth of subvolcanic reservoirs of eruptible magma. Such understanding is important for two reasons; firstly it presents an insight into how and why the frequency of eruptions varies between different groups of volcanoes; and secondly, it provides constraints for models that are used to interpret geochemical and geophysical data. To perform the analysis we further develop an analytical model that uses a Monte Carlo sampling approach to simulate the accumulation and eruption of magmatic reservoirs (Caricchi et al., 2014). By inverting the geological record of volcanic eruptions we can solve the Monte Carlo model to quantify parameters such as magma input and frequency of magma injection. Our results indicate systematic variation in the frequency of eruptions of various magnitudes between exchangeable groups of volcanoes, which can be related to variations of parameters such as average magma fluxes and thickness of the crust. Caricchi, L., C. Annen, J. Blundy, G. Simpson, and V. Pinel, 2014, Nature Geoscience, v. 7, no. 2, p. 126-130, doi:10.1038/ngeo2041.

  16. The record of magma chamber processes in plagioclase phenocrysts at Thera Volcano, Aegean Volcanic Arc, Greece

    Science.gov (United States)

    Stamatelopoulou-Seymour, Karen; Vlassopoulos, Dimitrios; Pearce, Thomas H.; Rice, Craig

    1990-01-01

    Lavas and pyroclastic rocks throughout the volcanic stratigraphy of the Tertiary-Quaternary volcanic complex of Thera in the Aegean island arc display inhomogenous plagioclase populations and phenocryst resorption textures, interpreted as indicative of magma mixing. Plagioclase zoning characteristics studied by Nomarski and laser interferometry techniques establish three main categories of plagioclase: (i) inherited plagioclase (nucleated in endmember prior to initial mixing event) (ii) in situ plagioclase (nucleated in mixed or hybrid magma) and (iii) xenocrystic plagioclase. Nomarski contrast images and linearized compositional zoning profiles reveal striking differences between calcic and sodic plagioclases, depending on the composition of the lava in which they are hosted. These differences reflect the contrasting effects of changes in physical-chemical parameters in basic vis-a-vis more acidic melts during magma mixing and/or influx of new magma into the subvolcanic magma chamber, as well as the influence of magma chamber dynamics on plagioclase equilibration. Variations in bulk major and trace element abundances of Thera volcanic products reflect the dominant overprint of crystal fractionation, but decoupling between major and trace element fractionation models and variations in incompatible trace element distributions are all indicative of magma mixing processes, consistent with compositional and textural zoning in plagioclases.

  17. MIGRATION OF SEISMIC AND VOLCANIC ACTIVITY AS DISPLAY OF WAVE GEODYNAMIC PROCESS

    Directory of Open Access Journals (Sweden)

    Alexander V. Vikulin

    2015-09-01

    Full Text Available Publications about the earthquake foci migration have been reviewed. An important result of such studies is establishment of wave nature of seismic activity migration that is manifested by two types of rotational waves; such waves are responsible for interaction between earthquakes foci and propagate with different velocities. Waves determining long-range interaction of earthquake foci are classified as Type 1; their limiting velocities range from 1 to 10 cm/s. Waves determining short-range interaction of foreshocks and aftershocks of individual earthquakes are classified as Type 2; their velocities range from 1 to 10 km/s. According to the classification described in [Bykov, 2005], these two types of migration waves correspond to slow and fast tectonic waves. The most complete data on earthquakes (for a period over 4.1 million of years and volcanic eruptions (for 12 thousand years of the planet are consolidated in a unified systematic format and analyzed by methods developed by the authors. For the Pacific margin, Alpine-Himalayan belt and the Mid-Atlantic Ridge, which are the three most active zones of the Earth, new patterns of spatial and temporal distribution of seismic and volcanic activity are revealed; they correspond to Type 1 of rotational waves. The wave nature of the migration of seismic and volcanic activity is confirmed. A new approach to solving problems of geodynamics is proposed with application of the data on migration of seismic and volcanic activity, which are consolidated in this study, in combination with data on velocities of movement of tectonic plate boundaries. This approach is based on the concept of integration of seismic, volcanic and tectonic processes that develop in the block geomedium and interact with each other through rotating waves with a symmetric stress tensor. The data obtained in this study give grounds to suggest that a geodynamic value, that is mechanically analogous to an impulse

  18. Deposition or not? The fate of volcanic ash after aggregation processes

    Science.gov (United States)

    Mueller, Sebastian B.; Kueppers, Ulrich; Wadsworth, Fabian B.; Ayris, Paul M.; Casas, Ana S.; Cimarelli, Corrado; Ametsbichler, Jonathan; Delmelle, Pierre; Taddeucci, Jacopo; Jacob, Michael; Dingwell, Donald B.

    2017-04-01

    a highly hygroscopic salt) in de-ionized water yielded comparable results without observable aggregation. In case of successful aggregation, concentration of salts has been found to be in the range of published values. We conclude that non-hygroscopic salt crystal precipitation from an aqueous liquid interacting with the glass phase in volcanic ash is a very efficient way to produce cohesive ash aggregates that can survive external forces acting during transport and sedimentation. Our parameterization of ash aggregation processes shall now be implemented in ash plume dispersal modelling for improved and more accurate ash distribution forecasting in the event of explosive volcanic eruptions.

  19. Experiments on gas-ash separation processes in volcanic umbrella plumes

    Science.gov (United States)

    Holasek, Rick E.; Woods, Andrew W.; Self, Stephen

    1996-03-01

    We present a series of analogue laboratory experiments which simulate the separation of ash and gas and the formation of secondary intrusions from finite volcanic umbrella plumes. We examined the lateral spreading of mixtures of freshwater and particles released into a laboratory tank containing a uniformly stratified aqueous solution. For times smaller than the sedimentation time of particles through the intrusion, the current remains coherent and intrudes laterally. As some of the particles settle into the underlying ambient fluid, a layer of particle-depleted fluid develops below the upper surface of the current and the density of the residual fluid is reduced. Over longer times, the intrusion ceases to be coherent, with small fingers of relatively buoyant, particle-depleted fluid rising from the upper part of the intrusion into the overlying fluid. Meanwhile, the lateral motion of the injected solution induces a return flow in the ambient fluid which sweeps some of the particles sedimenting from the lower surface of the intrusion inwards. As a result, relatively dense particle-laden fluid collects below the intrusion and then sinks into the underlying fluid. Eventually this fluid reaches a new neutral buoyancy height, where it intrudes to form a second laterally spreading current below the original intrusion. The process then repeats to form further weaker intrusions below. These results of the separation of the ash and volcanic gas in an umbrella plume are consistent with field observations at Sakurajima volcano where positively charged plumes, thought to consist of volcanic gas, have been observed above negatively charged plumes of ash. This work also suggests that volcanic aerosols may form up to a kilometer above the original injection height of the ash. In a strong wind shear, this could result in very different trajectories of the ash and gas and so be important for evaluating the impact of ash plumes on both aviation safety and volcanic aerosol formation

  20. Water Flow in Karst Aquifer Considering Dynamically Variable Saturation Conduit

    Science.gov (United States)

    Tan, Chaoqun; Hu, Bill X.

    2017-04-01

    The karst system is generally conceptualized as dual-porosity system, which is characterized by low conductivity and high storage continuum matrix and high conductivity and quick flow conduit networks. And so far, a common numerical model for simulating flow in karst aquifer is MODFLOW2005-CFP, which is released by USGS in 2008. However, the steady-state approach for conduit flow in CFP is physically impractical when simulating very dynamic hydraulics with variable saturation conduit. So, we adopt the method proposed by Reimann et al. (2011) to improve current model, in which Saint-Venant equations are used to model the flow in conduit. Considering the actual background that the conduit is very big and varies along flow path and the Dirichlet boundary varies with rainfall in our study area in Southwest China, we further investigate the influence of conduit diameter and outflow boundary on numerical model. And we also analyze the hydraulic process in multi-precipitation events. We find that the numerical model here corresponds well with CFP for saturated conduit, and it could depict the interaction between matrix and conduit during very dynamic hydraulics pretty well compare with CFP.

  1. Engineering Bi-Layer Nanofibrous Conduits for Peripheral Nerve Regeneration

    Science.gov (United States)

    Zhu, Yiqian; Wang, Aijun; Patel, Shyam; Kurpinski, Kyle; Diao, Edward; Bao, Xuan; Kwong, George; Young, William L.

    2011-01-01

    Trauma injuries often cause peripheral nerve damage and disability. A goal in neural tissue engineering is to develop synthetic nerve conduits for peripheral nerve regeneration having therapeutic efficacy comparable to that of autografts. Nanofibrous conduits with aligned nanofibers have been shown to promote nerve regeneration, but current fabrication methods rely on rolling a fibrous sheet into the shape of a conduit, which results in a graft with inconsistent size and a discontinuous joint or seam. In addition, the long-term effects of nanofibrous nerve conduits, in comparison with autografts, are still unknown. Here we developed a novel one-step electrospinning process and, for the first time, fabricated a seamless bi-layer nanofibrous nerve conduit: the luminal layer having longitudinally aligned nanofibers to promote nerve regeneration, and the outer layer having randomly organized nanofibers for mechanical support. Long-term in vivo studies demonstrated that bi-layer aligned nanofibrous nerve conduits were superior to random nanofibrous conduits and had comparable therapeutic effects to autografts for nerve regeneration. In summary, we showed that the engineered nanostructure had a significant impact on neural tissue regeneration in situ. The results from this study will also lead to the scalable fabrication of engineered nanofibrous nerve conduits with designed nanostructure. This technology platform can be combined with drug delivery and cell therapies for tissue engineering. PMID:21501089

  2. The Variable Scale Evacuation Model (VSEM: a new tool for simulating massive evacuation processes during volcanic crises

    Directory of Open Access Journals (Sweden)

    J. M. Marrero

    2010-04-01

    Full Text Available Volcanic eruptions are among the most awesome and powerful displays of nature's force, constituting a major natural hazard for society (a single eruption can claim thousands of lives in an instant. Consequently, assessment and management of volcanic risk have become critically important goals of modern volcanology. Over recent years, numerous tools have been developed to evaluate volcanic risk and support volcanic crisis management: probabilistic analysis of future eruptions, hazard and risk maps, event trees, etc. However, there has been little improvement in the tools that may help Civil Defense officials to prepare Emergency Plans. Here we present a new tool for simulating massive evacuation processes during volcanic crisis: the Variable Scale Evacuation Model (VSEM. The main objective of the VSEM software is to optimize the evacuation process of Emergency Plans during volcanic crisis. For this, the VSEM allows the simulation of an evacuation considering different strategies depending on diverse impact scenarios. VSEM is able to calculate the required time for the complete evacuation taking into account diverse evacuation scenarios (number and type of population, infrastructure, road network, etc. and to detect high-risk or "blackspots" of the road network. The program is versatile and can work at different scales, thus being capable of simulating the evacuation of small villages as well as huge cities.

  3. Tracking dynamics of magma migration in open-conduit systems

    Science.gov (United States)

    Valade, Sébastien; Lacanna, Giorgio; Coppola, Diego; Laiolo, Marco; Pistolesi, Marco; Donne, Dario Delle; Genco, Riccardo; Marchetti, Emanuele; Ulivieri, Giacomo; Allocca, Carmine; Cigolini, Corrado; Nishimura, Takeshi; Poggi, Pasquale; Ripepe, Maurizio

    2016-11-01

    Open-conduit volcanic systems are typically characterized by unsealed volcanic conduits feeding permanent or quasi-permanent volcanic activity. This persistent activity limits our ability to read changes in the monitored parameters, making the assessment of possible eruptive crises more difficult. We show how an integrated approach to monitoring can solve this problem, opening a new way to data interpretation. The increasing rate of explosive transients, tremor amplitude, thermal emissions of ejected tephra, and rise of the very-long-period (VLP) seismic source towards the surface are interpreted as indicating an upward migration of the magma column in response to an increased magma input rate. During the 2014 flank eruption of Stromboli, this magma input preceded the effusive eruption by several months. When the new lateral effusive vent opened on the Sciara del Fuoco slope, the effusion was accompanied by a large ground deflation, a deepening of the VLP seismic source, and the cessation of summit explosive activity. Such observations suggest the drainage of a superficial magma reservoir confined between the crater terrace and the effusive vent. We show how this model successfully reproduces the measured rate of effusion, the observed rate of ground deflation, and the deepening of the VLP seismic source. This study also demonstrates the ability of the geophysical network to detect superficial magma recharge within an open-conduit system and to track magma drainage during the effusive crisis, with a great impact on hazard assessment.

  4. Frictional melting dynamics in the upper conduit: A chemical answer to a complex physical question

    Science.gov (United States)

    Henton De Angelis, S.; Lavallee, Y.; Kendrick, J. E.; Hornby, A.; von Aulock, F. W.; Clesham, S.; Hirose, T.; Perugini, D.

    2013-12-01

    During volcanic eruptions the generation of frictional heat along the walls of the shallow conduit leads to melting of the rocks along the slip interface. Frictional melting has previously been described as a process out of thermodynamic equilibrium, but upon slip and mingling of the melt batches, homogeneity can be achieved, and may have an h important rheological control on the dynamics of slip. To test melt homogenization in the frictional melt zones of volcanic conduits we performed constant-rate slip experiments under controlled stress conditions using a high-velocity rotary shear apparatus. Volcanic dome samples from three different volcanoes (Volcán De Colima, Soufrière Hills Volcano and Santiaguito Volcano) were investigated. Each sample was subjected to a stress of 1 MPa and slip rate of 1 m/s. For each sample set 5 experiments were conducted: 1) experiment stopped at the onset of melting; 2) experiment stopped on the formation of a full melt layer; 3) experiment stopped after 5m of slip at steady state conditions; 4) experiment stopped after 10m of slip at steady state conditions; 5) experiment stopped after 15m of slip at steady state conditions. We analyzed the resulting proto-melt zones using micron sized X-ray spectroscopy in the high-brightness synchrotron beamline I18 (at Diamond Light Source UK). Particular focus was given to the concentration variance analysis of Rare Earth Elements as their mobilities can be used to precisely quantify the degree and timescale of homogenisation involved during frictional melting. This study refines our understanding of the chemical process of melting and mixing which carry important consequences for the rheological control on the physical dynamics of slip.

  5. Interplay between tectonic and volcanic processes along the East Pacific Rise, 16°N

    Science.gov (United States)

    Le Saout, M.; Thibaud, R.; Gente, P.

    2015-12-01

    The East-Pacific Rise (EPR) is a fast spreading ridge. Between 15°22'N and 16°15'N the spreading rate is 87 mm/year. This segment is the most inflated of the EPR due to its interaction with the Mathematician hotspot. The French PARISUB ("Panache Ridge Submersible") cruise in 2010 acquired high-resolution geophysical data using the Autonomous Underwater Vehicle (AUV) Aster-X and the manned submersible Nautile (Ifremer). The goal was to investigate in detail the magmatic and tectonic processes at the intersection between the hotspot and the ridge. We investigate tectonic and volcanic processes using high-resolution data along the 16°N segment of the EPR. Near bottom bathymetric data (1 meter grid spacing) are improved by photos, videos and human observations from submersible survey. Data are used : 1/ to characterize in detail tectonic feature (faults and fissures) geometries (e.g., dip and vertical throw), 2/ to distinguish between different lava flows (pillow, lobate and sheet flows) and to locate lava sources defined in particular by flow front orientations and lava channels. In a context of an unusual spreading segment under influence of a hot spot, these data allow us to evaluate how small-scale volcanic and tectonic processes near ASTs, interact for nucleation and evolution of faulting patterns, and affect tectonic stain evaluation. The distinction between eruptive and non-eruptive tectonic features allows to estimate the distribution of tectonic feature affected by magnetic overprinting. We propose two origins for nucleation and evolution of faults around the AST, and define relations between faults, lava flows and seismic layer 2A.

  6. The sensitivity of conduit flow models to basic input parameters: there is no need for magma trolls!

    Science.gov (United States)

    Thomas, M. E.; Neuberg, J. W.

    2012-04-01

    this magnitude resulting from small alterations in the basic governing parameters does this render any changes in individual conduit processes of secondary importance? As important as the melt viscosity is to any conduit flow model, it is a meaningless parameter unless there is a conduit through which to flow. The shape and size of a volcanic conduit are even less well constrained than magma's temperature and water content, but have an equally important role to play. Rudimentary changes such as simply increasing or decreasing the radius of a perfectly cylindrical conduit can have large effects, and when coupled with the range of magma viscosities that may be flowing through them can completely change interpretations. Although we present results specifically concerning the variables of magma temperature and water content and the radius of a cylindrical conduit, this is just the start, by systematically identifying the effect each parameter has on the conduit flow models it will be possible to identify which areas are most requiring of future attention.

  7. Seafloor doming driven by degassing processes unveils sprouting volcanism in coastal areas

    Science.gov (United States)

    Passaro, Salvatore; Tamburrino, Stella; Vallefuoco, Mattia; Tassi, Franco; Vaselli, Orlando; Giannini, Luciano; Chiodini, Giovanni; Caliro, Stefano; Sacchi, Marco; Rizzo, Andrea Luca; Ventura, Guido

    2016-03-01

    We report evidences of active seabed doming and gas discharge few kilometers offshore from the Naples harbor (Italy). Pockmarks, mounds, and craters characterize the seabed. These morphologies represent the top of shallow crustal structures including pagodas, faults and folds affecting the present-day seabed. They record upraise, pressurization, and release of He and CO2 from mantle melts and decarbonation reactions of crustal rocks. These gases are likely similar to those that feed the hydrothermal systems of the Ischia, Campi Flegrei and Somma-Vesuvius active volcanoes, suggesting the occurrence of a mantle source variously mixed to crustal fluids beneath the Gulf of Naples. The seafloor swelling and breaching by gas upraising and pressurization processes require overpressures in the order of 2-3 MPa. Seabed doming, faulting, and gas discharge are manifestations of non-volcanic unrests potentially preluding submarine eruptions and/or hydrothermal explosions.

  8. The role of lithospheric processes on the development of linear volcanic ridges in the Azores

    Science.gov (United States)

    Neves, M. C.; Miranda, J. M.; Luis, J. F.

    2013-11-01

    Linear volcanic ridges (LVRs) are widespread along the Azores plateau and are often used as a tectonic marker of the surface stress field. Nevertheless, the mechanisms that drive the emplacement and development of these structures are not well established and they have been attributed to the plateau diffuse deformation, off-rift extension or the result of the interaction between a hotspot and the brittle lithosphere. This study hypothesizes that linear volcanic ridges are the result of magma emplacement into pre-existing damaged lithosphere, using a 3D finite-element representation of the brittle lithosphere and underlying ductile mantle, and assuming that the deformation is driven by plate boundary forces applied at the edges, as describe by global plate kinematic models. The brittle layer is described by an elastoplastic rheology with progressive damage, where fractures are assumed to be analogous to localized shear bands. The ductile mantle underneath is modeled as a viscoelastic layer that exerts a shear drag at the base of the brittle layer. The modeling shows that lithospheric processes alone can justify the spatial distribution of linear volcanic ridges, and even the development of the Faial Ridge. The factors controlling the fracturing pattern are the plate geometry and velocity boundary conditions, the shearing introduced at the East Azores Fracture Zone/Gloria fault limit and the interaction between the viscous mantle and the spatially varying brittle plate thickness. Along the Terceira Rift the predicted fractures match the orientation of the LVRs in the second (~ N135°-N140°) and third (N150° to N-S) sectors and provide an explanation for the arcuate shape of the rift itself. The brittle plate thickness variations are crucial for the development of the more recent LVRs, which are predicted to occur along the Faial Ridge. In the best fit model the top mantle viscosity is 1 × 1022 Pa s at 5-15 km depth, and the present-day fracture network takes ~ 3

  9. Energy transport processes in a brittle ductile intrusive model of the Taupo Volcanic Zone, New Zealand

    Science.gov (United States)

    Weir, Graham J.

    1998-08-01

    The implications of the findings of recent GPS and micro-seismic studies in the Taupo Volcanic Zone (TVZ), New Zealand, on models of processes transporting mass, heat and chemicals are discussed. It is argued that in addition to the well established process of groundwater convection extracting heat and chemicals by interacting with magmatic intrusives under the TVZ, that two other processes may be important. Firstly, the existence of a ductile layer with very low permeability between about 8 to 15 km depth will produce a region of `enhanced conduction' in which very high conductive fluxes of energy arise from a temperature distribution which varies exponentially with depth. Secondly, water may transport up through the ductile layer, as a result of extensional processes in the ductile region. If extension is occurring at about 8 mm/yr, then geothermal heat transfer in the TVZ of about 4200 MW is made up from about 1200 MW from the cooling of intrusives in the brittle region in the upper 8 km; of about an additional 1900 MW of conducted heat entering the brittle region from the ductile region; and about an additional 1100 MW from water transport through the ductile region. Provided this water flow has a chloride concentration similar to that emitted from nearby volcanoes, then the total chloride transport from the TVZ is about 3.5 kg/s, as suggested by average enthalpy to chloride ratios in the TVZ of about 1.2 MJ/g. The present high heat and mass transport processes in the TVZ are assumed to result from the passive filling of volume created from extensional processes under the TVZ, plus conductive and/or convective heating processes below 15 km depth.

  10. Different deformation patterns using GPS in the volcanic process of El Hierro (Canary Island) 2011-2013

    Science.gov (United States)

    García-Cañada, Laura; José García-Arias, María; Pereda de Pablo, Jorge; Lamolda, Héctor; López, Carmen

    2014-05-01

    Ground deformation is one of the most important parameter in volcano monitoring. The detected deformations in volcanic areas can be precursors of a volcanic activity and contribute with useful information to study the evolution of an unrest, eruption or any volcanic process. GPS is the most common technique used to measure volcano deformations. It can be used to detect slow displacement rates or much larger and faster deformations associated with any volcanic process. In volcanoes the deformation is expected to be a mixed of nature; during periods of quiescence it will be slow or not present, while increased activity slow displacement rates can be detected or much larger and faster deformations can be measure due to magma intrusion, for example in the hours to days prior a eruption beginning. In response to the anomalous seismicity detected at El Hierro in July 2011, the Instituto Geográfico Nacional (IGN) improved its volcano monitoring network in the island with continuous GPS that had been used to measure the ground deformation associated with the precursory unrest since summer 2011, submarine eruption (October 2011-March 2012) and the following unrest periods (2012-2013). The continuous GPS time series, together with other techniques, had been used to evaluate the activity and to detect changes in the process. We investigate changes in the direction and module of the deformation obtained by GPS and they show different patterns in every unrest period, very close to the seismicity locations and migrations.

  11. Conduit dynamics in transitional rhyolitic activity recorded by tuffisite vein textures from the 2008-2009 Chaitén eruption

    Directory of Open Access Journals (Sweden)

    Elodie eSaubin

    2016-05-01

    Full Text Available The mechanisms of hazardous silicic eruptions are controlled by complex, poorly-understood conduit processes. Observations of recent Chilean rhyolite eruptions have revealed the importance of hybrid activity, involving simultaneous explosive and effusive emissions from a common vent. Such behaviour hinges upon the ability of gas to decouple from magma in the shallow conduit. Tuffisite veins are increasingly suspected to be a key facilitator of outgassing, as they repeatedly provide a transient permeable escape route for volcanic gases. Intersection of foam domains by tuffisite veins appears critical to efficient outgassing. However, knowledge is currently lacking into textural heterogeneities within shallow conduits, their relationship with tuffisite vein propagation, and the implications for fragmentation and degassing processes. Similarly, the magmatic vesiculation response to upper conduit pressure perturbations, such as those related to the slip of dense magma plugs, remains largely undefined. Here we provide a detailed characterization of an exceptionally large tuffisite vein within a rhyolitic obsidian bomb ejected during transitional explosive-effusive activity at Chaitén, Chile in May 2008. Vein textures and chemistry provide a time-integrated record of the invasion of a dense upper conduit plug by deeper fragmented magma. Quantitative textural analysis reveals diverse vesiculation histories of various juvenile clast types.Using vesicle size distributions, bubble number densities, zones of diffusive water depletion, and glass H2O concentrations, we propose a multi-step degassing/fragmentation history, spanning deep degassing to explosive bomb ejection. Rapid decompression events of ~3-4 MPa are associated with fragmentation of foam and dense magma at ~200-350 metres depth in the conduit, permitting vertical gas and pyroclast mobility over hundreds of metres. Permeable pathway occlusion in the dense conduit plug by pyroclast accumulation

  12. Conduit dynamics in transitional rhyolitic activity recorded by tuffisite vein textures from the 2008-2009 Chaitén eruption

    Science.gov (United States)

    Saubin, Elodie; Tuffen, Hugh; Gurioli, Lucia; Owen, Jacqueline; Castro, Jonathan; Berlo, Kim; McGowan, Ellen; Schipper, C.; Wehbe, Katia

    2016-05-01

    The mechanisms of hazardous silicic eruptions are controlled by complex, poorly-understood conduit processes. Observations of recent Chilean rhyolite eruptions have revealed the importance of hybrid activity, involving simultaneous explosive and effusive emissions from a common vent. Such behaviour hinges upon the ability of gas to decouple from magma in the shallow conduit. Tuffisite veins are increasingly suspected to be a key facilitator of outgassing, as they repeatedly provide a transient permeable escape route for volcanic gases. Intersection of foam domains by tuffisite veins appears critical to efficient outgassing. However, knowledge is currently lacking into textural heterogeneities within shallow conduits, their relationship with tuffisite vein propagation, and the implications for fragmentation and degassing processes. Similarly, the magmatic vesiculation response to upper conduit pressure perturbations, such as those related to the slip of dense magma plugs, remains largely undefined. Here we provide a detailed characterization of an exceptionally large tuffisite vein within a rhyolitic obsidian bomb ejected during transitional explosive-effusive activity at Chaitén, Chile in May 2008. Vein textures and chemistry provide a time-integrated record of the invasion of a dense upper conduit plug by deeper fragmented magma. Quantitative textural analysis reveals diverse vesiculation histories of various juvenile clast types. Using vesicle size distributions, bubble number densities, zones of diffusive water depletion, and glass H2O concentrations, we propose a multi-step degassing/fragmentation history, spanning deep degassing to explosive bomb ejection. Rapid decompression events of ~3-4 MPa are associated with fragmentation of foam and dense magma at ~200-350 metres depth in the conduit, permitting vertical gas and pyroclast mobility over hundreds of metres. Permeable pathway occlusion in the dense conduit plug by pyroclast accumulation and sintering

  13. From Magma Chamber to Tephra- what can volcanic titanite tell us about pre-eruptive processes?

    Science.gov (United States)

    Iddon, Fiona; McLeod, Graham; Dempster, Tim; Walshaw, Richard; Everard, Lucie

    2014-05-01

    Large volume, apparently homogenous, crystal rich pyroclastic deposits, or so called 'monotonous intermediates' are often considered to represent erupted batholiths. Their formation and life-cycle can be preceded and eruptions triggered by highly complex magma chamber processes, with multiple periods of recharge, mixing and thermal oscillations [1]. This information is difficult to observe, even at the crystal scale due to fragmentation or re-equilibration with subsequent recharge events. Titanite is a geochemically robust mineral that acts as a reservoir for trace elements, in particular the HFSEs and REEs. This ability to act as a primary control on the trace element budget of a melt [2], coupled with its refractory nature, allows titanite to preserve compositional zoning, proven to act as a reliable record of magma chamber conditions even in long-lived plutons [3]. This study extends the use of titanite to volcanic rocks via a coupled micro-textural and geochemical study of titanites from the Fish Canyon Tuff, Colorado. Regarded as the largest ever recorded pyroclastic deposit, it is thought that the batholith-sized magma chamber cooled to a rigid crystalline mush prior to thermal rejuvenation via underplating mafic magma [1]. It is additionally suggested this may have acted as a trigger for the eruption [1]. Results have shown the titanites to possess trace element zoning reflecting changes in melt composition and chamber conditions. Dissolution horizons and inclusion suites additionally provide evidence for multiple changes in temperature and oxygen fugacity aiding the interpretation of pre-eruptive processes. The study is ongoing with investigation of titanite from the Cerro Galan Ignimbrite, Argentina. The deposit again is suggested to have undergone a complex magma chamber growth and recharge history, with further proposals of multiple magma storage locations at different crustal levels [4]. The crystal zoning may provide further evidence for this, however

  14. Conduit dynamics and post explosion degassing on Stromboli: A combined UV camera and numerical modeling treatment

    Science.gov (United States)

    McGonigle, A. J. S.; James, M. R.; Tamburello, G.; Aiuppa, A.; Delle Donne, D.; Ripepe, M.

    2016-01-01

    Abstract Recent gas flux measurements have shown that Strombolian explosions are often followed by periods of elevated flux, or “gas codas,” with durations of order a minute. Here we present UV camera data from 200 events recorded at Stromboli volcano to constrain the nature of these codas for the first time, providing estimates for combined explosion plus coda SO2 masses of ≈18–225 kg. Numerical simulations of gas slug ascent show that substantial proportions of the initial gas mass can be distributed into a train of “daughter bubbles” released from the base of the slug, which we suggest, generate the codas, on bursting at the surface. This process could also cause transitioning of slugs into cap bubbles, significantly reducing explosivity. This study is the first attempt to combine high temporal resolution gas flux data with numerical simulations of conduit gas flow to investigate volcanic degassing dynamics. PMID:27478285

  15. Conduit dynamics in transitional rhyolitic activity recorded by tuffisite vein textures from the 2008-2009 Chaitén eruption

    Science.gov (United States)

    Saubin, Elodie; Tuffen, Hugh; Gurioli, Lucia; Owen, Jacqueline; Castro, Jonathan; Berlo, Kim; McGowan, Ellen; Schipper, C. Ian; Wehbe, Katia

    2016-04-01

    Conduit processes govern the mechanisms of hazardous silicic eruptions, but our understanding of complex conduit behaviour is far from complete. Observations of recent Chilean rhyolite eruptions have revealed the importance of hybrid activity, involving simultaneous explosive and effusive emissions from a common vent[1]. Such behaviour hinges upon the ability of gas to decouple from magma in the shallow conduit. Tuffisite veins are increasingly suspected to be a key facilitator of outgassing, as they repeatedly provide a transient permeable escape route for volcanic gases. However, we have limited insights into the interactions between tuffisites and foams that appear critical to efficient outgassing[2], and into how heterogeneous conduit magma responds to pressure perturbations related to repeated disruption or slip of dense magma plugs. Here we provide a detailed characterization of an exceptionally large tuffisite vein within a rhyolitic obsidian bomb ejected during transitional explosive-effusive activity at volcán Chaitén, Chile in May 2008. Vein textures and chemistry provide a time-integrated record of the invasion of a dense upper conduit plug by deeper fragmented magma. Quantitative textural analysis reveals diverse vesiculation histories of varied juvenile clast types. Using vesicle size distributions, bubble number densities, zones of diffusive water depletion, and glass H2O concentrations, we propose a multi-step degassing/fragmentation history, spanning deep degassing to explosive bomb ejection. Rapid decompression events of ~3-4 MPa are associated with fragmentation of foam and dense magma at ~200-300 metres depth in the conduit, permitting vertical gas and pyroclast mobility over >100-200 metres. Permeable pathway occlusion in the dense conduit plug by pyroclast accumulation and sintering preceded ultimate bomb ejection, which triggered a final bubble nucleation event. Our results highlight how the vesiculation response of magma to decompression

  16. Carbothermal reduction process of silica formed from shirasu volcanic ash using solar furnace

    OpenAIRE

    Hatakeyama Keisuke; Sato Keigo; Nishioka Kensuke

    2016-01-01

    Metallurgical grade silicon was formed using Shirasu volcanic ash as starting material with solar furnace. The solar furnace was composed of two parts: Fresnel lens and reacting furnace. The reacting furnace was composed of a cylindrical vacuum chamber and quartz glass plate functioning to guide the concentrated sunlight into the furnace, and was placed at the focal point of the Fresnel lens. The sample was made from a mixture of silica formed from Shirasu volcanic ash and carbon, and placed ...

  17. Re-processing TOMS UV Measurements to Retrieve SO2 Emissions From Volcanic Eruptions

    Science.gov (United States)

    Fisher, B. L.; Krotkov, N. A.; Bhartia, P. K.; Li, C.; Haffner, D. P.; Leonard, P.; Carn, S. A.; Telling, J. W.

    2015-12-01

    The SO2 Monitoring Group at the NASA Goddard Space Flight Center is producing a new multi-satellite long term data set of volcanic SO2 column amounts and heights (MSVOLSO2L4) as part of the NASA MEaSUREs Program. Here we present re-analysis of the UV measurements (BUV) from the NASA Nimbus 7 Total Ozone Mapping Spectrometer (N7 TOMS: 1978-1993). Ozone is the dominant atmospheric absorber in the BUV spectrum, but volcanic eruptions can produce enough SO2 to be distinguished from ozone background. Quantitative retrieval of volcanic SO2 requires:1) Separation of the O3 and SO2 absorption in BUV radiances;2) Close to zero mean SO2 background;3) RT forward model that accounts for the presence of volcanic ash in the plume; 4) A priori knowledge of the ozone and SO2 vertical profiles.Our iterative retrieval algorithm returns O3 and SO2 column amounts, effective reflectivity and its spectral slope. The retrieval model also generates a 4 x 4 gain matrix for the SO2 free regions that is used to soft calibrate the measured 340 nm BUV radiance. The spectral slope implicitly accounts for the interference of volcanic ash, but more explicit ash treatment is required to better quantify SO2 errors in volcanic plumes heavily loaded with ash. This presentation will discuss the methods used to characterize the error sources and assess the quality of this unique long-term SO2 data set.

  18. Estimation of the soil strength parameters in Tertiary volcanic regolith (NE Turkey) using analytical hierarchy process

    Indian Academy of Sciences (India)

    Hakan Ersoy; Melek Betül Karsli; Seda Çellek; Bilgehan Kul; Idris Baykan; Robert L Parsons

    2013-12-01

    Costly and time consuming testing techniques and the difficulties in providing undisturbed samples for these tests have led researchers to estimate strength parameters of soils with simple index tests. However, the paper focuses on estimation of strength parameters of soils as a function of the index properties. Analytical hierarchy process and multiple regression analysis based methodology were performed on datasets obtained from soil tests on 41 samples in Tertiary volcanic regolith. While the hierarchy model focused on determining the most important index properties affecting on strength parameters, regression analysis established meaningful relationships between strength parameters and index properties. The negative polynomial correlations between the friction angle and plasticity properties, and the positive exponential relations between the cohesion and plasticity properties were determined. These relations are characterized by a regression coefficient of 0.80. However, Terzaghi bearing capacity formulas were used to test the model. It is important to see whether there is any statistically significant relation between the calculated and the observed bearing capacity values for model testing. Based on the model, the positive linear correlation characterized by the regression coefficient of 0.86 were determined between bearing capacity values obtained by direct and indirect methods.

  19. Conduit degassing and thermal controls on eruption styles at Mount St. Helens

    Science.gov (United States)

    Schneider, Andrew; Rempel, Alan W.; Cashman, Katharine V.

    2012-12-01

    The explosivity of silicic eruptions depends on the interplay between magma rheology, exsolution kinetics, and degassing. Magma degassing is governed by the competing effects of vertical transport within the conduit and the lateral flux of gas out of the conduit (Diller et al., 2006; Jaupart and Allegre, 1991). We combine a simplified treatment of these degassing processes with thermodynamic modeling to examine the conditions present at Mount St. Helens during the spine extruding eruption from 2004 to 2008. We find that two parameters are primarily responsible for controlling the eruptive style: the magma chamber temperature, and a dimensionless parameter that gauges the efficiency of lateral degassing. Together, these parameters determine whether and where magma can solidify at depth to form a dense solid plug that is gradually extruded as a volcanic spine. We show that the small (50 oC) decrease in magma chamber temperature between eruptive activity in the 1980s and that of 2004-2008, combined with a modest increase in degassing efficiency associated with lower volumetric flux, can explain the observed change in erupted material from viscous lava flows to solidified spines. More generally, we suggest that similar threshold behavior may explain observed abrupt transitions in effusive eruptive styles at other intermediate composition volcanoes. Finally, we extrapolate our results to suggest that the increase in degassing efficiency accompanying decreasing magma supply rates may have caused the transition from explosive to effusive activity in late 1980.

  20. Groundwater flow processes and mixing in active volcanic systems: the case of Guadalajara (Mexico)

    Science.gov (United States)

    Hernández-Antonio, A.; Mahlknecht, J.; Tamez-Meléndez, C.; Ramos-Leal, J.; Ramírez-Orozco, A.; Parra, R.; Ornelas-Soto, N.; Eastoe, C. J.

    2015-09-01

    Groundwater chemistry and isotopic data from 40 production wells in the Atemajac and Toluquilla valleys, located in and around the Guadalajara metropolitan area, were determined to develop a conceptual model of groundwater flow processes and mixing. Stable water isotopes (δ2H, δ18O) were used to trace hydrological processes and tritium (3H) to evaluate the relative contribution of modern water in samples. Multivariate analysis including cluster analysis and principal component analysis were used to elucidate distribution patterns of constituents and factors controlling groundwater chemistry. Based on this analysis, groundwater was classified into four groups: cold groundwater, hydrothermal groundwater, polluted groundwater and mixed groundwater. Cold groundwater is characterized by low temperature, salinity, and Cl and Na concentrations and is predominantly of Na-HCO3-type. It originates as recharge at "La Primavera" caldera and is found predominantly in wells in the upper Atemajac Valley. Hydrothermal groundwater is characterized by high salinity, temperature, Cl, Na and HCO3, and the presence of minor elements such as Li, Mn and F. It is a mixed-HCO3 type found in wells from Toluquilla Valley and represents regional flow circulation through basaltic and andesitic rocks. Polluted groundwater is characterized by elevated nitrate and sulfate concentrations and is usually derived from urban water cycling and subordinately from agricultural return flow. Mixed groundwaters between cold and hydrothermal components are predominantly found in the lower Atemajac Valley. Twenty-seven groundwater samples contain at least a small fraction of modern water. The application of a multivariate mixing model allowed the mixing proportions of hydrothermal fluids, polluted waters and cold groundwater in sampled water to be evaluated. This study will help local water authorities to identify and dimension groundwater contamination, and act accordingly. It may be broadly applicable to

  1. Depositional and welding processes in low aspect ratio ignimbrites: examples from the Sulcis Volcanic District(Sardinia, Italy)

    OpenAIRE

    Mulas, Maurizio

    2013-01-01

    The rheomorphic, high-grade, welded ignimbrites are a special type of pyroclastic density current (PDC) deposits usually associated with high intensity volcanic explosive activity (VEI >4). They are characterized by a high variability of physical features and sedimentological structures that may testify different emplacement mechanisms from a PDC and a different response to topography during and after the end of the depositional processes. When the temperatures of the deposits are higher than...

  2. A New Statistical Model for Eruption Forecasting at Open Conduit Volcanoes: an Application to Mt Etna and Kilauea Volcanoes

    Science.gov (United States)

    Passarelli, Luigi; Sanso, Bruno; Laura, Sandri; Marzocchi, Warner

    2010-05-01

    One of the main goals in volcanology is to forecast volcanic eruptions. A trenchant forecast should be made before the onset of a volcanic eruption, using the data available at that time, with the aim of mitigating the volcanic risk associated to the volcanic event. In other words, models implemented with forecast purposes have to take into account the possibility to provide "forward" forecasts and should avoid the idea of a merely "retrospective" fitting of the data available. In this perspective, the main idea of the present model is to forecast the next volcanic eruption after the end of the last one, using only the data available at that time. We focus our attention on volcanoes with open conduit regime and high eruption frequency. We assume a generalization of the classical time predictable model to describe the eruptive behavior of open conduit volcanoes and we use a Bayesian hierarchical model to make probabilistic forecast. We apply the model to Kilauea volcano eruptive data and Mt. Etna volcano flank eruption data. The aims of this model are: 1) to test whether or not the Kilauea and Mt Etna volcanoes follow a time predictable behavior; 2) to discuss the volcanological implications of the time predictable model parameters inferred; 3) to compare the forecast capabilities of this model with other models present in literature. The results obtained using the MCMC sampling algorithm show that both volcanoes follow a time predictable behavior. The numerical values of the time predictable model parameters inferred suggest that the amount of the erupted volume could change the dynamics of the magma chamber refilling process during the repose period. The probability gain of this model compared with other models already present in literature is appreciably greater than zero. This means that our model performs better forecast than previous models and it could be used in a probabilistic volcanic hazard assessment scheme. In this perspective, the probability of

  3. Processing of radon time series in underground environments: Implications for volcanic surveillance in the island of Tenerife, Canary Islands, Spain

    Energy Technology Data Exchange (ETDEWEB)

    Vinas, Ronaldo [Department of Soil Sciences and Geology, Faculty of Biology, Universidad de La Laguna, Av. Astrofisico Fransicso Sanchez s/n, 38206 Tenerife (Spain); Eff-Darwich, Antonio [Department of Soil Sciences and Geology, Faculty of Biology, Universidad de La Laguna, Av. Astrofisico Fransicso Sanchez s/n, 38206 Tenerife (Spain)]. E-mail: adarwich@ull.es; Soler, Vicente [Volcanological Station of the Canary Islands, IPNA-CSIC, 38206 La Laguna, Tenerife (Spain); Martin-Luis, Maria C. [Department of Soil Sciences and Geology, Faculty of Biology, Universidad de La Laguna, Av. Astrofisico Fransicso Sanchez s/n, 38206 Tenerife (Spain); Quesada, Maria L. [Department of Soil Sciences and Geology, Faculty of Biology, Universidad de La Laguna, Av. Astrofisico Fransicso Sanchez s/n, 38206 Tenerife (Spain); Nuez, Julio de la [Department of Soil Sciences and Geology, Faculty of Biology, Universidad de La Laguna, Av. Astrofisico Fransicso Sanchez s/n, 38206 Tenerife (Spain)

    2007-01-15

    The analysis of temporal and spatial variations in the flux of soil gases across the soil-air interface is a useful tool to study geo-dynamical processes associated with volcanic and/or seismic activity. However, many of these variations are induced by external variables, such as temperature, barometric pressure, rainfall and other meteorological variables. In an attempt to filter out non-endogenous variations in the emissions of gases, the optimal choice of the monitoring sites with numerical filtering techniques based on multi-variate and frequency domain analysis of the time series for gaseous emissions were combined, in the case of radon ({sup 222}Rn). Monitoring sites are located in underground galleries in the volcanic island of Tenerife, Canary Islands, Spain. Since the effect of wind, rainfall and temperature variations are very small inside galleries, a first natural filtering process of external parameters in the emissions of gases was achieved. This new approach has been successfully tested and as a result, the background level for radon emissions at various locations has been defined, by which correlations between gaseous emissions and the volcanic and/or seismic activity could be carried out.

  4. Using Websites to Convey Scientific Uncertainties for Volcanic Processes and Potential Hazards

    Science.gov (United States)

    Venezky, D. Y.; Lowenstern, J. B.; Hill, D. P.

    2005-12-01

    The Yellowstone Volcano Observatory (YVO) and Long Valley Observatory (LVO) websites have greatly increased the public's awareness and access to information about scientific uncertainties for volcanic processes by communicating at multiple levels of understanding and varied levels of detail. Our websites serve a broad audience ranging from visitors unaware of the calderas, to lay volcano enthusiasts, to scientists, federal agencies, and emergency managers. Both Yellowstone and Long Valley are highly visited tourist attractions with histories of caldera-forming eruptions large enough to alter global climate temporarily. Although it is much more likely that future activity would be on a small scale at either volcano, we are constantly posed questions about low-probability, high-impact events such as the caldera-forming eruption depicted in the recent BBC/Discovery movie, "Supervolcano". YVO and LVO website objectives include: providing monitoring data, explaining the likelihood of future events, summarizing research results, helping media provide reliable information, and expanding on information presented by the media. Providing detailed current information is a crucial website component as the public often searches online to augment information gained from often cryptic pronouncements by the media. In May 2005, for example, YVO saw an order of magnitude increase in page requests on the day MSNBC ran the misleading headline, "Yellowstone eruption threat high." The headline referred not to current events but a general rating of Yellowstone as one of 37 "high threat" volcanoes in the USGS National Volcano Early Warning System report. As websites become a more dominant source of information, we continuously revise our communication plans to make the most of this evolving medium. Because the internet gives equal access to all information providers, we find ourselves competing with various "doomsday" websites that sensationalize and distort the current understanding of

  5. Influence of seismic processes and volcanic activity on the formation of disastrous floods

    Science.gov (United States)

    Trifonov, Dmitriy

    2014-05-01

    models of hydraulic systems, but ultimately due to difference of pressures in their respective segments and areas of the transport network. At the exit of the groundwater on the surface such change in pressure is connected both with the state of the actual water flow in underground cavities, or violations of the structure (topology) of 3D-network. As one of the major and sudden reasons of change of pressure in the underground system can serve seismic processes, including volcanic eruptions (as magmatic and ash). During these processes enormous underground space can be freed from the dense rock. This leads to rapid changes in pressure and that, in principle, a new topology of 3D network and water flows in it. It is important that such dynamic processes occur over huge distances in underground basins of thousands of kilometers [3], of course, with a certain time delay. In the result of the analysis of large-scale flooding in Russia in 2001-2002, as well as the catastrophic floods in Western Europe, in the Amur region of Russia and in the state of Colorado USA in 2013, a correlation between seismic and volcanic activities and floods, expressed by specific numerical correlation coefficients, has been revealed. For example, knowing the date, location and magnitude of an earthquake, we can identify potentially dangerous territories in the aspect of the probability of occurrence of floods, because the stresses in the crust, spreading from the hypocenter of earthquakes, and their subsequent relaxation are one of the most important factors of floods. Mechanisms of distribution of these stresses are well-studied today [2] unlike their influence on the groundwater. The defined boundaries of potentially dangerous sites are broad enough; with regard to the direction of distribution of stress, it is about the sectors in 40 degrees (from the line of the movement of the crustal plate) in the direction from the boundaries of lithospheric plates. Distribution of this impact occurs, as a

  6. Nanofiber-reinforced biological conduit in cardiac surgery: preliminary report.

    Science.gov (United States)

    Guhathakurta, Soma; Galla, Satish; Ramesh, Balasundari; Venugopal, Jayarama Reddy; Ramakrishna, Seeram; Cherian, Kotturathu Mammen

    2011-06-01

    Several options are available for right ventricular outflow tract reconstruction, including commercially available bovine jugular vein and cryo-preserved homografts. Homograft non-availability and the problems of commercially available conduits led us to develop indigenously processed bovine jugular vein conduits with competent valves. They were made completely acellular and strengthened by non-conventional cross-linking without disturbing the extracellular matrix, which improved the luminal surface characteristics for hemocompatibility. Biocompatibility in vitro and in vivo, along with thermal stability, matrix stability, and mechanical strength have been evaluated. Sixty-nine patients received these conduits for right ventricular outflow tract reconstruction. Seven conduits dilated and 4 required replacement. To counteract dilatation, biodegradable polymeric nanofibers in various combinations and in isolation (collagen, polycaprolactone, polylactic acid) were characterized and used to reinforce the conduit circumferentially. Physical validation by mechanical testing, scanning electron microscopy, and in-vitro cytotoxicity was conducted. Thermal stability, spectroscopy studies of the polymer, and preclinical studies of the coated bovine jugular vein in animals are in progress. The feasibility studies have been completed, and the final polymer selection depends on evaluation of the functional superiority of the coated bovine jugular vein.

  7. LiDAR observations of an Earth magmatic plumbing system as an analog for Venus and Mars distributed volcanism

    Science.gov (United States)

    Richardson, Jacob; Connor, Charles; Malservisi, Rocco; Bleacher, Jacob; Connor, Laura

    2014-05-01

    Clusters of tens to thousands of small volcanoes (diameters generally system of these clusters can constrain magma ascent processes as well as the regional magma production budget and heat flux beneath each cluster. Unfortunately, directly observing the plumbing systems of volcano clusters on Mars and Venus eludes our current geologic abilities. Because erosion exposes such systems at the Earth's surface, a better understanding of magmatic processes and migration can be achieved via field analysis. The terrestrial plumbing system of an eroded volcanic field may be a valuable planetary analog for Venus and Mars clusters. The magmatic plumbing system of a Pliocene-aged monogenetic volcanic field, emplaced at 0.8 km depth, is currently exposed as a sill and dike swarm in the San Rafael Desert of Central Utah, USA. The mafic bodies in this region intruded into Mesozoic sedimentary units and now make up the most erosion resistant units as sills, dikes, and plug-like conduits. Light Detection and Ranging (LiDAR) can identify volcanic units (sills, dikes, and conduits) at high resolution, both geomorphologically and with near infrared return intensity values. Two Terrestrial LiDAR Surveys and an Airborne LiDAR Survey have been carried out over the San Rafael volcanic swarm, producing a three dimensional point cloud over approximately 36 sq. km. From the point clouds of these surveys, 1-meter DEMs are produced and volcanic intrusions have been mapped. Here we present reconstructions of the volcanic instrusions of the San Rafael Swarm. We create this reconstruction by extrapolating mapped intrustions from the LiDAR surveys into a 3D space around the current surface. We compare the estimated intrusive volume to the estimated conduit density and estimates of extrusive volume at volcano clusters of similar density. The extrapolated reconstruction and conduit mapping provide a first-order estimate of the final intrustive/extrusive volume ratio for the now eroded volcanic field

  8. A comparative review of petrogenetic processes beneath the Cameroon Volcanic Line: Geochemical constraints

    Directory of Open Access Journals (Sweden)

    Asobo N.E. Asaah

    2015-07-01

    Full Text Available The origin and petrogenesis of the Cameroon Volcanic Line (CVL, composed of volcanoes that form on both the ocean floor and the continental crust, are difficult to understand because of the diversity, heterogeneity, and nature of available data. Major and trace elements, and Sr-Nd-Pb isotope data of volcanic rocks of the CVL spanning four decades have been compiled to reinterpret their origin and petrogenesis. Volcanic rocks range from nephelinite, basanite and alkali basalts to phonolite, trachyte and rhyolite with the presence of a compositional gap between SiO2 58–64 wt.%. Similarities in geochemical characteristics, modeled results for two component mixing, and the existence of mantle xenoliths in most mafic rocks argue against significant crustal contamination. Major and trace element evidences indicate that the melting of mantle rocks to generate the CVL magma occurred dominantly in the garnet lherzolite stability field. Melting models suggest small degree (<3% partial melting of mantle bearing (6–10% garnet for Mt. Etinde, the Ngaoundere Plateau and the Biu Plateau, and <5% of garnet for the oceanic sector of the CVL, Mt. Cameroon, Mt. Bambouto, Mt. Manengouba and the Oku Volcanic Group. The Sr-Nd-Pb isotope systematics suggest that mixing in various proportions of Depleted MORB Mantle (DMM with enriched mantle 1 and 2 (EM1 and EM2 could account for the complex isotopic characteristics of the CVL lavas. Low Mg number (Mg# = 100 × MgO/(MgO + FeO and Ni, Cr and Co contents of the CVL mafic lavas reveal their crystallization from fractionated melts. The absence of systematic variation in Nb/Ta and Zr/Hf ratios, and Sr-Nd isotope compositions between the mafic and felsic lavas indicates progressive evolution of magmas by fractional crystallization. Trace element ratios and their plots corroborate mantle heterogeneity and reveal distinct geochemical signatures for individual the CVL volcanoes.

  9. A comparative review of petrogenetic processes beneath the Cameroon Volcanic Line:Geochemical constraints

    Institute of Scientific and Technical Information of China (English)

    Asobo N.E. Asaah; Tetsuya Yokoyama; Festus T. Aka; Tomohiro Usui; Mengnjo J. Wirmvem; Boris Chako Tchamabe; Takeshi Ohba; Gregory Tanyileke; J.V. Hell

    2015-01-01

    The origin and petrogenesis of the Cameroon Volcanic Line (CVL), composed of volcanoes that form on both the ocean floor and the continental crust, are difficult to understand because of the diversity, het-erogeneity, and nature of available data. Major and trace elements, and Sr-Nd-Pb isotope data of volcanic rocks of the CVL spanning four decades have been compiled to reinterpret their origin and petrogenesis. Volcanic rocks range from nephelinite, basanite and alkali basalts to phonolite, trachyte and rhyolite with the presence of a compositional gap between SiO2 58e64 wt.%. Similarities in geochemical characteristics, modeled results for two component mixing, and the existence of mantle xenoliths in most mafic rocks argue against significant crustal contamination. Major and trace element evidences indicate that the melting of mantle rocks to generate the CVL magma occurred dominantly in the garnet lherzolite stability field. Melting models suggest small degree (<3%) partial melting of mantle bearing (6e10%) garnet for Mt. Etinde, the Ngaoundere Plateau and the Biu Plateau, and<5%of garnet for the oceanic sector of the CVL, Mt. Cameroon, Mt. Bambouto, Mt. Manengouba and the Oku Volcanic Group. The Sr-Nd-Pb isotope sys-tematics suggest that mixing in various proportions of Depleted MORB Mantle (DMM) with enriched mantle 1 and 2 (EM1 and EM2) could account for the complex isotopic characteristics of the CVL lavas. Low Mg number (Mg# ¼ 100 ? MgO/(MgO þ FeO)) and Ni, Cr and Co contents of the CVL mafic lavas reveal their crystallization from fractionated melts. The absence of systematic variation in Nb/Ta and Zr/Hf ratios, and Sr-Nd isotope compositions between the mafic and felsic lavas indicates progressive evolution of magmas by fractional crystallization. Trace element ratios and their plots corroborate mantle het-erogeneity and reveal distinct geochemical signatures for individual the CVL volcanoes.

  10. Linear permeability evolution of expanding conduits due to feedback between flow and fast phase change

    Science.gov (United States)

    Wang, Lichun; Cardenas, M. Bayani

    2017-05-01

    Conduits are ubiquitous and critical pathways for many fluids relevant for geophysical processes such as magma, water, and gases. Predicting flow through conduits is challenging when the conduit geometry coevolves with the flow. We theoretically show that the permeability (k) of a conduit whose walls are eroding due to fast phase change increases linearly with time because of a self-reinforcing mechanism. This simple result is surprising given complex feedbacks between flow, transport, and phase change. The theory is congruent with previous experimental observations of fracture dissolution in calcite. Supporting computational fracture dissolution experiments showed that k only slightly increases until the dissolution front reaches the narrowest conduit constriction, after which the linear evolution of k manifests. The theory holds across multiple scales and a broad range of Peclet and Damkohler numbers and thus advances the prediction of dynamic mass fluxes through expanding conduits in various geologic and environmental settings.Plain Language SummaryGeological conduits are ubiquitous present in the subsurface. In many situations, these conduits may enlarge through time due to erosion of its walls by dissolution and melting. This leads to strongly coupled flow and reactive transport processes where the flow dictates the wall's erosion and vice versa. As the conduit expands, so does its permeability and thus flow. Thus, predicting fluid flow and relevant transport processes through expanding conduits is challenging. In this study, we presented a theory for the linear time dependence of permeability for expanding conduits. The theory is congruent with previous observations from fracture dissolution in calcite. An additional series of our own computational experiments also aligns with the theory. The theory will be of interest to geoscientists and engineers in many fields such as hydrology, glaciology, and petroleum engineering, to name a few.

  11. Onboard Processing of Multispectral and Hyperspectral Data of Volcanic Activity for Future Earth-Orbiting and Planetary Missions

    Science.gov (United States)

    Davies, Ashley Gerard; Chien, Steve; Tran, Daniel Q.; Doubleday, Joshua

    2010-01-01

    Autonomous onboard processing of data allows rapid response to detections of dynamic, changing processes. Software that can detect volcanic eruptions from thermal emission has been used to retask the Earth Observing 1 spacecraft to obtain additional data of the eruption. Rapid transmission of these data to the ground, and the automatic processing of the data to generated images, estimates of eruption parameters and maps of thermal structure, has allowed these products to be delivered rapidly to volcanologists to aid them in assessing eruption risk and hazard. Such applications will enhance science return from future Earth-orbiting spacecraft and also from spacecraft exploring the Solar System, or beyond, which hope to image dynamic processes. Especially in the latter case, long communication times between the spacecraft and Earth exclude a rapid response to what may be a transient process - only using onboard autonomy can the spacecraft react quickly to such an event.

  12. Peripheral nerve conduits: technology update

    Directory of Open Access Journals (Sweden)

    Arslantunali D

    2014-12-01

    Full Text Available D Arslantunali,1–3,* T Dursun,1,2,* D Yucel,1,4,5 N Hasirci,1,2,6 V Hasirci,1,2,7 1BIOMATEN, Center of Excellence in Biomaterials and Tissue Engineering, Middle East Technical University (METU, Ankara, Turkey; 2Department of Biotechnology, METU, Ankara, Turkey; 3Department of Bioengineering, Gumushane University, Gumushane, Turkey; 4Faculty of Engineering, Department of Medical Engineering, Acibadem University, Istanbul, Turkey; 5School of Medicine, Department of Histology and Embryology, Acibadem University, Istanbul, Turkey; 6Department of Chemistry, Faculty of Arts and Sciences, METU, Ankara, Turkey; 7Department of Biological Sciences, Faculty of Arts and Sciences, METU, Ankara, Turkey *These authors have contributed equally to this work Abstract: Peripheral nerve injury is a worldwide clinical problem which could lead to loss of neuronal communication along sensory and motor nerves between the central nervous system (CNS and the peripheral organs and impairs the quality of life of a patient. The primary requirement for the treatment of complete lesions is a tension-free, end-to-end repair. When end-to-end repair is not possible, peripheral nerve grafts or nerve conduits are used. The limited availability of autografts, and drawbacks of the allografts and xenografts like immunological reactions, forced the researchers to investigate and develop alternative approaches, mainly nerve conduits. In this review, recent information on the various types of conduit materials (made of biological and synthetic polymers and designs (tubular, fibrous, and matrix type are being presented. Keywords: peripheral nerve injury, natural biomaterials, synthetic biomaterials

  13. Confort 15 model of conduit dynamics: applications to Pantelleria Green Tuff and Etna 122 BC eruptions

    Science.gov (United States)

    Campagnola, S.; Romano, C.; Mastin, L. G.; Vona, A.

    2016-06-01

    Numerical simulations are useful tools to illustrate how flow parameters and physical processes may affect eruption dynamics of volcanoes. In this paper, we present an updated version of the Conflow model, an open-source numerical model for flow in eruptive conduits during steady-state pyroclastic eruptions (Mastin and Ghiorso in A numerical program for steady-state flow of magma-gas mixtures through vertical eruptive conduits. U.S. Geological Survey Open File Report 00-209, 2000). In the modified version, called Confort 15, the rheological constraints are improved, incorporating the most recent constitutive equations of both the liquid viscosity and crystal-bearing rheology. This allows all natural magma compositions, including the peralkaline melts excluded in the original version, to be investigated. The crystal-bearing rheology is improved by computing the effect of strain rate and crystal shape on the rheology of natural magmatic suspensions and expanding the crystal content range in which rheology can be modeled compared to the original version ( Conflow is applicable to magmatic mixtures with up to 30 vol% crystal content). Moreover, volcanological studies of the juvenile products (crystal and vesicle size distribution) of the investigated eruption are directly incorporated into the modeling procedure. Vesicle number densities derived from textural analyses are used to calculate, through Toramaru equations, maximum decompression rates experienced during ascent. Finally, both degassing under equilibrium and disequilibrium conditions are considered. This allows considerations on the effect of different fragmentation criteria on the conduit flow analyses, the maximum volume fraction criterion ("porosity criterion"), the brittle fragmentation criterion and the overpressure fragmentation criterion. Simulations of the pantelleritic and trachytic phases of the Green Tuff (Pantelleria) and of the Plinian Etna 122 BC eruptions are performed to test the upgrades in

  14. Supercomputer modeling of volcanic eruption dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Kieffer, S.W. [Arizona State Univ., Tempe, AZ (United States); Valentine, G.A. [Los Alamos National Lab., NM (United States); Woo, Mahn-Ling [Arizona State Univ., Tempe, AZ (United States)

    1995-06-01

    Our specific goals are to: (1) provide a set of models based on well-defined assumptions about initial and boundary conditions to constrain interpretations of observations of active volcanic eruptions--including movies of flow front velocities, satellite observations of temperature in plumes vs. time, and still photographs of the dimensions of erupting plumes and flows on Earth and other planets; (2) to examine the influence of subsurface conditions on exit plane conditions and plume characteristics, and to compare the models of subsurface fluid flow with seismic constraints where possible; (3) to relate equations-of-state for magma-gas mixtures to flow dynamics; (4) to examine, in some detail, the interaction of the flowing fluid with the conduit walls and ground topography through boundary layer theory so that field observations of erosion and deposition can be related to fluid processes; and (5) to test the applicability of existing two-phase flow codes for problems related to the generation of volcanic long-period seismic signals; (6) to extend our understanding and simulation capability to problems associated with emplacement of fragmental ejecta from large meteorite impacts.

  15. Nonlinear wavetrains in viscous conduits

    Science.gov (United States)

    Maiden, Michelle; Hoefer, Mark

    2016-11-01

    Viscous fluid conduits provide an ideal system for the study of dissipationless, dispersive hydrodynamics. A dense, viscous fluid serves as the background medium through which a lighter, less viscous fluid buoyantly rises. If the interior fluid is continuously injected, a deformable pipe forms. The long wave interfacial dynamics are well-described by a dispersive nonlinear partial differential equation. In this talk, experiments, numerics, and asymptotics of the viscous fluid conduit system will be presented. Structures at multiple length scales are discussed, including solitons, dispersive shock waves, and periodic waves. Modulations of periodic waves will be explored in the weakly nonlinear regime with the Nonlinear Schrödinger (NLS) equation. Modulational instability (stability) is identified for sufficiently short (long) periodic waves due to a change in dispersion curvature. These asymptotic results are confirmed by numerical simulations of perturbed nonlinear periodic wave solutions. Also, numerically observed are envelope bright and dark solitons well approximated by NLS. This work was partially supported by NSF CAREER DMS-1255422 (M.A.H.) and NSF GRFP (M.D.M.).

  16. The geochemistry of lithium-bearing geothermal water, Taupo Volcanic Zone, and shallow fluid processes in a very active silicic volcanic arc

    Science.gov (United States)

    Dean, A. S.; Hoskin, P. W.; Rudnick, R. L.; Liu, X.; Boseley, C.

    2011-12-01

    The Li abundances and isotopic systematics of Taupo Volcanic Zone (TVZ) geothermal fluids preserves a record of processes occurring within shallow portions of geothermal reservoirs as well as deeper portions of the arc crust. Understanding Li cycling and isotopic fractionation in TVZ geothermal systems contributes to a more refined understanding of physicochemical processes affecting New Zealand's geothermal resources. A comprehensive dataset of 73 samples was compiled, with samples collected from geothermal surface features (springs, spouters, geysers, etc.) and electric-power industry production wells, collectively representing18 geothermal fields across the breadth and width the TVZ. No comparable dataset of fluid analyses exists. Ion chromatography, AAS, and quadrupole ICP-MS analyses were done for Li, Cl-, SiO2, SO42- K, Na, Ca, Mg, B, Sr and Pb concentrations. Lithium abundance in geothermal fluids from the TVZ have a dataset-wide average of 5.9 mg/L and range 4 μg/L to 29 mg/L. The Li abundance and Li/Cl ratios for geothermal water and steam condensates vary systematically as a result of boiling, mixing, and water/rock reaction. Lithium abundance and Li/Cl ratios are, therefore, indicators of shallow (above 2.5 km) and locally variable reservoir processes. δ7Li analysis of 63 samples was performed at the University of Maryland, College Park. Data quality was controlled by measurement of L-SVEC as a calibration standard and by multiple analysis of selected samples. The average δ7Li value for TVZ geothermal fluids is -0.8%. Most δ7Li values for geothermal water fall within a small range of about -3% to+2% indicating similar processes are causing similar isotopic fractionation throughout the region. Considered together, Li aundances and δ7Li values, in combination with numerical models, indicate possible evolution pathways and water/rock reactions in TVZ geothermal systems. Models based on rocks and surface water analysis indicate that Li cycles and

  17. Development and relationship of monogenetic and polygenetic volcanic fields in time and space.

    Science.gov (United States)

    Germa, Aurelie; Connor, Chuck; Connor, Laura; Malservisi, Rocco

    2013-04-01

    The classification of volcanic systems, developed by G. P. L. Walker and colleagues, relates volcano morphology to magma transport and eruption processes. In general, distributed monogenetic volcanic fields are characterized by infrequent eruptions, low average output rate, and a low spatial intensity of the eruptive vents. In contrast, central-vent-dominated systems, such as stratovolcanoes, central volcanoes and lava shields are characterized by frequent eruptions, higher average flux rates, and higher spatial intensity of eruptive vents. However, it has been observed that a stratovolcano is often associated to parasitic monogenetic vents on its flanks, related to the central silicic systems, and surrounded by an apron of monogenetic edifices that are part of the volcanic field but independent from the principal central system. It appears from spatial distribution and time-volume relationships that surface area of monogenetic fields reflects the lateral extent of the magma source region and the lack of magma focusing mechanisms. In contrast, magma is focused through a unique conduit system for polygenetic volcanoes, provided by a thermally and mechanically favorable pathway toward the surface that is maintained by frequent and favorable stress conditions. We plan to relate surface observations of spatio-temporal location of eruptive vents and evolution of the field area through time to processes that control magma focusing during ascent and storage in the crust. We choose to study fields that range from dispersed to central-vent dominated, through transitional fields (central felsic system with peripheral field of monogenetic vents independent from the rhyolitic system). We investigate different well-studied volcanic fields in the Western US and Western Europe in order to assess influence of the geodynamic setting and tectonic stress on the spatial distribution of magmatism. In summary, incremental spatial intensity maps should reveal how fast a central conduit

  18. Magma fracture and hybrid earthquakes in the conduit of Augustine Volcano

    Science.gov (United States)

    Buurman, Helena; West, Michael E.

    2013-12-01

    exploit subtle but systematic shifts in seismic waveforms to examine a 2 h cluster of repeating hybrid volcanic earthquakes preceding the first magmatic explosions at Augustine Volcano in January 2006. We extract differential P wave traveltimes of <0.01 s to determine that the source locations migrated downward by approximately 35 m. Waveform characteristics, GPS observations, and visual reports of lava effusion at the summit suggest that the earthquakes were sourced by fracturing magma in the upper conduit. As the lava cooled and degassed at the surface, the conditions in the upper conduit changed causing the zone in which magma fracture could occur to move downward through the magma column. These changes may also have been the first indicators that the conduit was becoming choked, causing a buildup in pressure that resulted in the large magmatic explosions that followed 36 h later.

  19. Lunar Pyroclastic Eruptions: Basin Volcanism's Dying Gasps

    Science.gov (United States)

    Kramer, G. Y.; Nahm, A.; McGovern, P. J.; Kring, D. A.

    2011-12-01

    The relationship between mare volcanism and impact basins has long been recognized, although the degree of influence basin formation has on volcanism remains a point of contention. For example, did melting of magma sources result from thermal energy imparted by a basin-forming event? Did basin impacts initiate mantle overturn of the unstable LMO cumulate pile, causing dense ilmenite to sink and drag radioactive KREEPy material to provide the thermal energy to initiate melting of the mare sources? Did the dramatically altered stress states provide pathways ideally suited for magma ascent? The chemistry of sampled lunar volcanic glasses indicates that they experienced very little fractional crystallization during their ascent to the surface - they have pristine melt compositions. Volatile abundances, including recent measurements of OH [1,2] suggest that the mantle source of at least the OH-analyzed glasses have a water abundance of ~700 ppm - comparable to that of Earth's upper mantle. More recently, [3] showed that the abundance of OH and other volatiles measured in these glasses is positively correlated with trace element abundances, which is expected since water is incompatible in a magma. Volatile enrichment in a deep mantle source would lower the melting temperature and provide the thrust for magma ascent through 500 km of mantle and crust [4]. We are exploring the idea that such basin-related lunar pyroclastic volcanism may represent the last phase of basaltic volcanism in a given region. Remote sensing studies have shown volcanic glasses are fairly common, and often found along the perimeter of mare-filled basins [5]. Recent modeling of the stresses related to the basin-forming process [6,7] show that basin margins provide the ideal conduit for low-volume lunar pyroclastic volcanism (compared with the high output of mare volcanism). Schrödinger's basin floor is largely composed of a compositionally uniform impact breccia. The exceptions are two distinct and

  20. Volcanic processes recorded by inclusions in sanidine megacrystals ejected from Quaternary Rockeskyll volcano, Eifel, Germany

    Science.gov (United States)

    Eilhard, Nicole; Schreuer, Jürgen; Stöckhert, Bernhard

    2016-04-01

    Sanidine megacrystals were ejected by a late stage explosive eruption at the Quaternary Rockeskyll volcanic complex, Eifel volcanic field, Germany. The homogeneous distribution of barium (about 1 % wt BaO equivalent to about 2 mole % celsian component) indicates that the nearly perfect single crystals must have crystallized in the Ostwald-Miers range from a huge reservoir, probably in the roof of a magma chamber. Irregularities during crystal growth caused trapping of hydrous melt inclusions, which are the objective of the present study. The inclusions show a characteristic concentric microstructure, in the following described from the sanidine host towards the inclusion center: (1) Ba is enriched by a factor of 2 to 3 in a ca. 0.01 mm wide rim, compared to the otherwise homogeneous sanidine host; (2) inwards, the continuous rim is overgrown by a thin crust of Ba enriched sanidine with irregular surface; (3) a layer of glass with a composition similar to sanidine; (4) a second, thinner layer of glass slightly reduced in Na2O and K2O, separated from the first glass layer by a sharp interface with approximately spherical shape; (5) a bubble containing a fluid phase, composed of H2O and minor CO2. This record is interpreted as follows: After crystallization of the sanidine megacrystals, a rise in temperature within the magmatic system caused some re-melting of the Ba-rich sanidine around the inclusions. Partitioning of Ba between the small included melt reservoir and the host caused formation of the Ba-rich rim (layer 1) by diffusive exchange. The onset of cooling lead to crystallization of the thin sanidine crust (layer 2). Finally, very rapid decompression and cooling during the subsequent explosive eruption caused sequential phase separation (two stages) in the remaining melt, the denser melt phase (layers 3 and 4) quenched to glass, the complementary low-density volatile-rich phase forming the central bubble. In summary, the microstructure and phase composition of

  1. Combined physical and chemical nonequilibrium transport model for solution conduits.

    Science.gov (United States)

    Field, Malcolm S; Leij, Feike J

    2014-02-01

    Solute transport in karst aquifers is primarily constrained to relatively complex and inaccessible solution conduits where transport is often rapid, turbulent, and at times constrictive. Breakthrough curves generated from tracer tests in solution conduits are typically positively-skewed with long tails evident. Physical nonequilibrium models to fit breakthrough curves for tracer tests in solution conduits are now routinely employed. Chemical nonequilibrium processes are likely important interactions, however. In addition to partitioning between different flow domains, there may also be equilibrium and nonequilibrium partitioning between the aqueous and solid phases. A combined physical and chemical nonequilibrium (PCNE) model was developed for an instantaneous release similar to that developed by Leij and Bradford (2009) for a pulse release. The PCNE model allows for partitioning open space in solution conduits into mobile and immobile flow regions with first-order mass transfer between the two regions to represent physical nonequilibrium in the conduit. Partitioning between the aqueous and solid phases proceeds either as an equilibrium process or as a first-order process and represents chemical nonequilibrium for both the mobile and immobile regions. Application of the model to three example breakthrough curves demonstrates the applicability of the combined physical and chemical nonequilibrium model to tracer tests conducted in karst aquifers, with exceptionally good model fits to the data. The three models, each from a different state in the United States, exhibit very different velocities, dispersions, and other transport properties with most of the transport occurring via the fraction of mobile water. Fitting the model suggests the potentially important interaction of physical and chemical nonequilibrium processes.

  2. Distributed measurement of flow rate in conduits using heated fiber optic distributed temperature sensing

    Science.gov (United States)

    Sánchez, Raúl; Zubelzu, Sergio; Rodríguez-Sinobas, Leonor; Juana, Luis

    2016-04-01

    In some cases flow varies along conduits, such as in irrigated land drainage pipes and channels, irrigation laterals and others. Detailed knowledge of flow rate along the conduit makes possible analytical evaluation of water distribution and collection systems performance. Flow rate can change continuously in some systems, like in drainage pipes and channels, or abruptly, like in conduits bifurcations or emitter insertions. A heat pulse along the conduit makes possible to get flow rate from continuity and heat balance equations. Due to the great value of specific heat of water, temperature changes along conduit are smaller than the noise that involves the measurement process. This work presents a methodology that, dealing with the noise of distributed temperature measurements, leads to flow rate determination along pressurized pipes or open channel flows.

  3. 47 CFR 32.2441 - Conduit systems.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Conduit systems. 32.2441 Section 32.2441 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES UNIFORM SYSTEM OF ACCOUNTS FOR TELECOMMUNICATIONS COMPANIES Instructions for Balance Sheet Accounts § 32.2441 Conduit systems. (a...

  4. Experimental investigations of aeration efficiency in high-head gated circular conduits.

    Science.gov (United States)

    Cihat Tuna, M; Ozkan, Fahri; Baylar, Ahmet

    2014-01-01

    The primary purpose of water aeration is to increase the oxygen saturation of the water. This can be achieved by using hydraulic structures because of substantial air bubble entrainment at these structures. Closed conduit aeration is a particular instance of this. While there has been a great deal of research on air-demand ratio within closed conduit, very little research has specifically addressed aeration efficiency of closed conduit. In the present work an experimental study was conducted to investigate the aeration efficiency of high-head gated circular conduits. Results showed that high-head gated circular conduits were effective for oxygen transfer. The effects of Froude number and ratio of the water cross-sectional flow area to the conduit cross-sectional area on aeration efficiency were particularly significant, whereas the effect of conduit length was only moderate. Further, a design formula for the aeration efficiency was presented relating the aeration efficiency to ratio of water cross-sectional flow area to conduit cross-sectional area and Froude number. The obtained results will be useful in future modeling processes and aid the practicing engineer in predicting aeration efficiency for design purposes.

  5. Xylem hydraulic conductivity related to conduit dimensions along chrysanthemum stems.

    NARCIS (Netherlands)

    Nijsse, J.; Heijden, van der G.W.A.M.; Ieperen, van W.; Keijzer, C.J.; Meeteren, van U.

    2001-01-01

    The stem xylem conduit dimensions and hydraulic conductivity of chrysanthemum plants (Dendranthemaxgrandiflorum Tzvelev cv. Cassa) were analysed and quantified. Simple exponential relations describe conduit length distribution, height dependency of conduit length distribution, and height dependency

  6. Ore-bearing hydrothermal metasomatic processes in the Elbrus volcanic center, the northern Caucasus, Russia

    Science.gov (United States)

    Gurbanov, A. G.; Bogatikov, O. A.; Dokuchaev, A. Ya.; Gazeev, V. M.; Abramov, S. S.; Groznova, E. O.; Shevchenko, A. V.

    2008-06-01

    Precaldera, caldera, and postcaldera cycles are recognized in the geological evolution of the Pleistocene-Holocene Elbrus volcanic center (EVC). During the caldera cycle, the magmatic activity was not intense, whereas hydrothermal metasomatic alteration of rocks was vigorous and extensive. The Kyukyurtli and Irik ore-magmatic systems have been revealed in the EVC, with the former being regarded as the more promising one. The ore mineralization in rocks of the caldera cycle comprises occurrences of magnetite, ilmenite, pyrite and pyrrhotite (including Ni-Co varieties), arsenopyrite, chalcopyrite, millerite, galena, and finely dispersed particles of native copper. Pyrite and pyrrhotite from volcanics of the caldera cycle and dacite of the Kyukyurtli extrusion are similar in composition and differ from these minerals of the postcaldera cycle, where pyrite and pyrrhotite are often enriched in Cu, Co, and Ni and millerite is noted as well. The composition of ore minerals indicates that the hydrothermal metasomatic alteration related to the evolution of the Kyukyurtli hydrothermal system was superimposed on rocks of the caldera cycle, whereas the late mineralization in rocks of the postcaldera cycle developed autonomously. The homogenization temperature of fluid inclusions in quartz and carbonate from crosscutting veinlets in the apical portion of the Kyukyurtli extrusion is 140-170°C and in quartz from geyserite, 120-150°C. The temperature of formation of the chalcopyrite-pyrite-pyrrhotite assemblage calculated using mineral geothermometers is 156 and 275°C in dacite from the middle and lower portions of the Malka lava flow and 190°C in dacite of the Kyukyurtli extrusion. The hydrothermal solutions that participated in metasomatic alteration of rocks pertaining to the Kyukyurtli ore-magmatic system (KOMS) and formed both secondary quartzite and geyserite were enriched in fluorine, as evidenced from the occurrence of F-bearing minerals-zharchikhite, ralstonite,

  7. A multi-faceted approach to characterize acid-sulfate alteration processes in volcanic hydrothermal systems on Earth and Mars

    Science.gov (United States)

    Marcucci, Emma Cordts

    Acid-sulfate alteration is a dominant weathering process in high temperature, low pH, sulfur-rich volcanic environments. Additionally, hydrothermal environments have been proposed as locations where life could have originated on Earth. Based on the extensive evidence of flowing surface water and persistent volcanism, similar locations and processes could have existed on early Mars. Globally observed alteration mineral assemblages likely represent relic Martian hydrothermal settings. Yet the limited understanding of environmental controls, limits the confidence of interpreting the paleoconditions of these hydrothermal systems and assessing their habitability to support microbial life. This thesis presents a series of laboratory experiments, geochemical models, analog fieldwork, and Martian remote sensing to characterize distinguishing features and controls of acid-sulfate alteration. The experiments and models were designed to replicate alteration is a highly acidic, sulfurous, and hot field sites. The basaltic minerals were individually reacted in both experimental and model simulations with varying initial parameters to infer the geochemical pathways of acid-sulfate alteration on Earth and Mars. It was found that for a specific starting material, secondary mineralogies were consistent. Variations in pH, temperature and duration affected the abundance, shape, and size of mineral products. Additionally evaporation played a key role in secondary deposits; therefore, both alteration and evaporitic processes need to be taken into consideration. Analog volcanic sites in Nicaragua were used to supplement this work and highlight differences between natural and simulated alteration. In situ visible near-infrared spectroscopy demonstrated that primary lithology and gas chemistry were dominant controls of alteration, with secondary effects from environmental controls, such as temperature and pH. The spectroscopic research from the field was directly related to Mars

  8. Volcanic signals in oceans

    KAUST Repository

    Stenchikov, Georgiy L.

    2009-08-22

    Sulfate aerosols resulting from strong volcanic explosions last for 2–3 years in the lower stratosphere. Therefore it was traditionally believed that volcanic impacts produce mainly short-term, transient climate perturbations. However, the ocean integrates volcanic radiative cooling and responds over a wide range of time scales. The associated processes, especially ocean heat uptake, play a key role in ongoing climate change. However, they are not well constrained by observations, and attempts to simulate them in current climate models used for climate predictions yield a range of uncertainty. Volcanic impacts on the ocean provide an independent means of assessing these processes. This study focuses on quantification of the seasonal to multidecadal time scale response of the ocean to explosive volcanism. It employs the coupled climate model CM2.1, developed recently at the National Oceanic and Atmospheric Administration\\'s Geophysical Fluid Dynamics Laboratory, to simulate the response to the 1991 Pinatubo and the 1815 Tambora eruptions, which were the largest in the 20th and 19th centuries, respectively. The simulated climate perturbations compare well with available observations for the Pinatubo period. The stronger Tambora forcing produces responses with higher signal-to-noise ratio. Volcanic cooling tends to strengthen the Atlantic meridional overturning circulation. Sea ice extent appears to be sensitive to volcanic forcing, especially during the warm season. Because of the extremely long relaxation time of ocean subsurface temperature and sea level, the perturbations caused by the Tambora eruption could have lasted well into the 20th century.

  9. Atmospheric processes affecting the separation of volcanic ash and SO2 in volcanic eruptions: inferences from the May 2011 Grímsvötn eruption

    Science.gov (United States)

    Prata, Fred; Woodhouse, Mark; Huppert, Herbert E.; Prata, Andrew; Thordarson, Thor; Carn, Simon

    2017-09-01

    The separation of volcanic ash and sulfur dioxide (SO2) gas is sometimes observed during volcanic eruptions. The exact conditions under which separation occurs are not fully understood but the phenomenon is of importance because of the effects volcanic emissions have on aviation, on the environment, and on the earth's radiation balance. The eruption of Grímsvötn, a subglacial volcano under the Vatnajökull glacier in Iceland during 21-28 May 2011 produced one of the most spectacular examples of ash and SO2 separation, which led to errors in the forecasting of ash in the atmosphere over northern Europe. Satellite data from several sources coupled with meteorological wind data and photographic evidence suggest that the eruption column was unable to sustain itself, resulting in a large deposition of ash, which left a low-level ash-rich atmospheric plume moving southwards and then eastwards towards the southern Scandinavian coast and a high-level predominantly SO2 plume travelling northwards and then spreading eastwards and westwards. Here we provide observational and modelling perspectives on the separation of ash and SO2 and present quantitative estimates of the masses of ash and SO2 that erupted, the directions of transport, and the likely impacts. We hypothesise that a partial column collapse or sloughing fed with ash from pyroclastic density currents (PDCs) occurred during the early stage of the eruption, leading to an ash-laden gravity intrusion that was swept southwards, separated from the main column. Our model suggests that water-mediated aggregation caused enhanced ash removal because of the plentiful supply of source water from melted glacial ice and from entrained atmospheric water. The analysis also suggests that ash and SO2 should be treated with separate source terms, leading to improvements in forecasting the movement of both types of emissions.

  10. Atmospheric processes affecting the separation of volcanic ash and SO2 in volcanic eruptions: inferences from the May 2011 Grímsvötn eruption

    Directory of Open Access Journals (Sweden)

    F. Prata

    2017-09-01

    Full Text Available The separation of volcanic ash and sulfur dioxide (SO2 gas is sometimes observed during volcanic eruptions. The exact conditions under which separation occurs are not fully understood but the phenomenon is of importance because of the effects volcanic emissions have on aviation, on the environment, and on the earth's radiation balance. The eruption of Grímsvötn, a subglacial volcano under the Vatnajökull glacier in Iceland during 21–28 May 2011 produced one of the most spectacular examples of ash and SO2 separation, which led to errors in the forecasting of ash in the atmosphere over northern Europe. Satellite data from several sources coupled with meteorological wind data and photographic evidence suggest that the eruption column was unable to sustain itself, resulting in a large deposition of ash, which left a low-level ash-rich atmospheric plume moving southwards and then eastwards towards the southern Scandinavian coast and a high-level predominantly SO2 plume travelling northwards and then spreading eastwards and westwards. Here we provide observational and modelling perspectives on the separation of ash and SO2 and present quantitative estimates of the masses of ash and SO2 that erupted, the directions of transport, and the likely impacts. We hypothesise that a partial column collapse or sloughing fed with ash from pyroclastic density currents (PDCs occurred during the early stage of the eruption, leading to an ash-laden gravity intrusion that was swept southwards, separated from the main column. Our model suggests that water-mediated aggregation caused enhanced ash removal because of the plentiful supply of source water from melted glacial ice and from entrained atmospheric water. The analysis also suggests that ash and SO2 should be treated with separate source terms, leading to improvements in forecasting the movement of both types of emissions.

  11. MeMoVolc report on classification and dynamics of volcanic explosive eruptions

    Science.gov (United States)

    Bonadonna, C.; Cioni, R.; Costa, A.; Druitt, T.; Phillips, J.; Pioli, L.; Andronico, D.; Harris, A.; Scollo, S.; Bachmann, O.; Bagheri, G.; Biass, S.; Brogi, F.; Cashman, K.; Dominguez, L.; Dürig, T.; Galland, O.; Giordano, G.; Gudmundsson, M.; Hort, M.; Höskuldsson, A.; Houghton, B.; Komorowski, J. C.; Küppers, U.; Lacanna, G.; Le Pennec, J. L.; Macedonio, G.; Manga, M.; Manzella, I.; Vitturi, M. de'Michieli; Neri, A.; Pistolesi, M.; Polacci, M.; Ripepe, M.; Rossi, E.; Scheu, B.; Sulpizio, R.; Tripoli, B.; Valade, S.; Valentine, G.; Vidal, C.; Wallenstein, N.

    2016-11-01

    Classifications of volcanic eruptions were first introduced in the early twentieth century mostly based on qualitative observations of eruptive activity, and over time, they have gradually been developed to incorporate more quantitative descriptions of the eruptive products from both deposits and observations of active volcanoes. Progress in physical volcanology, and increased capability in monitoring, measuring and modelling of explosive eruptions, has highlighted shortcomings in the way we classify eruptions and triggered a debate around the need for eruption classification and the advantages and disadvantages of existing classification schemes. Here, we (i) review and assess existing classification schemes, focussing on subaerial eruptions; (ii) summarize the fundamental processes that drive and parameters that characterize explosive volcanism; (iii) identify and prioritize the main research that will improve the understanding, characterization and classification of volcanic eruptions and (iv) provide a roadmap for producing a rational and comprehensive classification scheme. In particular, classification schemes need to be objective-driven and simple enough to permit scientific exchange and promote transfer of knowledge beyond the scientific community. Schemes should be comprehensive and encompass a variety of products, eruptive styles and processes, including for example, lava flows, pyroclastic density currents, gas emissions and cinder cone or caldera formation. Open questions, processes and parameters that need to be addressed and better characterized in order to develop more comprehensive classification schemes and to advance our understanding of volcanic eruptions include conduit processes and dynamics, abrupt transitions in eruption regime, unsteadiness, eruption energy and energy balance.

  12. Draining mafic magma from conduits during Strombolian eruption

    Science.gov (United States)

    Wadsworth, F. B.; Kennedy, B.; Branney, M. J.; Vasseur, J.; von Aulock, F. W.; Lavallée, Y.; Kueppers, U.

    2014-12-01

    During and following eruption, mafic magmas can readily drain downward in conduits, dykes and lakes producing complex and coincident up-flow and down-flow textures. This process can occur at the top of the plumbing system if the magma outgases as slugs or through porous foam, causing the uppermost magma surface to descend and the magma to densify. In this scenario the draining volume is limited by the gas volume outgassed. Additionally, magma can undergo wholesale backflow when the pressure at the base of the conduit or feeder dyke exceeds the driving pressure in the chamber beneath. This second scenario will continue until pressure equilibrium is established. These two scenarios may occur coincidently as local draining of uppermost conduit magma by outgassing can lead to wholesale backflow because the densification of magma is an effective way to modify the vertical pressure profile in a conduit. In the rare case where conduits are preserved in cross section, the textural record of draining is often complex and great care should be taken in interpreting bimodal kinematic trends in detail. Lateral cooling into country rock leads to lateral profiles of physical and flow properties and, ultimately, outgassing potential, and exploration of such profiles elucidates the complexity involved. We present evidence from Red Crater volcano, New Zealand, and La Palma, Canary Islands, where we show that at least one draining phase followed initial ascent and eruption. We provide a rheological model approach to understand gravitational draining velocities and therefore, the timescales of up- and down-flow cycles predicted. These timescales can be compared with observed geophysical signals at monitored mafic volcanoes worldwide. Finally, we discuss the implications of shallow magma draining for edifice stability, eruption longevity and magma-groundwater interaction.

  13. Acoustic waves in the atmosphere and ground generated by volcanic activity

    Energy Technology Data Exchange (ETDEWEB)

    Ichihara, Mie; Lyons, John; Oikawa, Jun; Takeo, Minoru [Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032 (Japan); Instituto Geofisico, Escuela Politecnica Nacional, Ladron de Guevara E11-253, Aptdo 2759, Quito (Ecuador); Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032 (Japan)

    2012-09-04

    This paper reports an interesting sequence of harmonic tremor observed in the 2011 eruption of Shinmoe-dake volcano, southern Japan. The main eruptive activity started with ashcloud forming explosive eruptions, followed by lava effusion. Harmonic tremor was transmitted into the ground and observed as seismic waves at the last stage of the effusive eruption. The tremor observed at this stage had unclear and fluctuating harmonic modes. In the atmosphere, on the other hand, many impulsive acoustic waves indicating small surface explosions were observed. When the effusion stopped and the erupted lava began explosive degassing, harmonic tremor started to be transmitted also to the atmosphere and observed as acoustic waves. Then the harmonic modes became clearer and more stable. This sequence of harmonic tremor is interpreted as a process in which volcanic degassing generates an open connection between the volcanic conduit and the atmosphere. In order to test this hypothesis, a laboratory experiment was performed and the essential features were successfully reproduced.

  14. Strategies in the processing and analysis of continuous gravity record in active volcanic areas: the case of Mt. Vesuvius

    Directory of Open Access Journals (Sweden)

    J. Hinderer

    2008-06-01

    Full Text Available This research is intended to describe new strategies in the processing and analysis of continuous gravity records collected in active volcanic areas and to assess how permanent gravity stations can improve the geophysical monitoring of a volcano. The experience of 15 years in continuous gravity monitoring on Mt. Vesuvius is discussed. Several geodynamic phenomena can produce temporal gravity changes. An eruption, for instance, is associated with the ascent of magma producing changes in the density distribution at depth, and leading to ground deformation and gravity changes The amplitude of such gravity variations is often quite small, in the order of 10-102 nms-2, so their detection requires high quality data and a rigorous procedure to isolate from the records those weak gravity signals coming from different sources. Ideally we need gravity signals free of all effects which are not of volcanic origin. Therefore solid Earth tide, ocean and atmospheric loading, instrumental drift or any kind of disturbances other than due to the volcano dynamics have to be removed. The state of the art on the modelling of the solid Earth tide is reviewed. The atmospheric dynamics is one of the main sources precluding the detection of small gravity signals. The most advanced methods to reduce the atmospheric effects on gravity are presented. As the variations of the calibration factors can prevent the repeatability of high-precision measurements, new approaches to model the instrumental response of mechanical gravimeters are proposed too. Moreover, a strategy for an accurate modelling of the instrumental drift and to distinguish it from longterm gravity changes is suggested.

  15. Pumped Storage and Potential Hydropower from Conduits

    Energy Technology Data Exchange (ETDEWEB)

    none,

    2015-02-25

    Th is Congressional Report, Pumped Storage Hydropower and Potential Hydropower from Conduits, addresses the technical flexibility that existing pumped storage facilities can provide to support intermittent renewable energy generation. This study considered potential upgrades or retrofit of these facilities, the technical potential of existing and new pumped storage facilities to provide grid reliability benefits, and the range of conduit hydropower opportunities available in the United States.

  16. Phase distribution in complex geometry conduits

    Energy Technology Data Exchange (ETDEWEB)

    Lahey, R.T. Jr.; Lopez de Bertodano, M.; Jones, O.C. Jr.

    1992-12-31

    Some of the most important and challenging problems in two-phase flow today have to do with the understanding and prediction of multidimensional phenomena, in particular, lateral phase distribution in both simple and complex geometry conduits. A prior review paper summarized the state-of-the-art in the understanding of phase distribution phenomena, and the ability to perform mechanistic multidimensional predictions. The purpose of this paper is to update that review, with particular emphasis on complex geometry conduit predictive capabilities.

  17. Imaging mud fluid conduits of the Gunshuiping mud volcano with Electric Resistivity Methods

    Science.gov (United States)

    Liao, Ling-Rong; Lin, Ting-Li; Chang, Ping-Yu

    2016-04-01

    We conducted the resistivity survey at the Gunshuiping mud volcano and produced a 3D model in order to delineate the mud-fluid conduits in the mud volcano system. The Gunshuiping mud volcano is located in a 175-m × 90-m plateau in Southwest of Taiwan. There are three main mud-volcano craters: craters 1, 2 and 3. Crater 3 is active and the others are inactive. We conducted thirteen survey lines using the Wenner configuration to obtain the resistivity profile images. The lengths of the lines are about 155 m and 60 m, which can resolve the resistivity image down to 30 m and 10 m in depth, respectively. The results appeared that there is a vertical structure under the crater 3, and we suggest that it is the mud-fluid conduit. There is a chamber at depth between 3 and 14 m, and we interpret it is the temporary storage of mud fluid during the erupting process. Beneath the craters 1 and 2, there is a near-surface, horizontal conduit connecting the craters 1 and 2. At depth between 15 and 25 m, the vertical conduit beneath the crater 3 and the horizontal conduit beneath the craters 1 and 2 are connected. The resistivity images clearly delineate the conduit underneath the craters and suggest that the crater 3 is the main erupting conduit, which is consistent with the surface features, in the Gunshuiping mud volcano system.

  18. Appraisal and evolution of hydrochemical processes from proximity basalt and granite areas of Deccan Volcanic Province (DVP) in India

    Science.gov (United States)

    Sonkamble, Sahebrao; Sahya, Ashalata; Mondal, N. C.; Harikumar, P.

    2012-05-01

    SummaryThis paper deals with a systematic hydrochemical study carried out at proximity basalt and granite areas of Deccan Volcanic Province (DVP) in India to assess groundwater quality and evaluate the hydrochemical processes. A total of 40 groundwater samples were collected equally from these areas and analyzed. Results showed that the groundwaters rich in alkaline earth in the basalt and alkali rich element in the granite. The dominancy of cations was observed as Ca2+ > Mg2+ > Na+ > K+ in the basalt and Na+ > Mg2+ > K+ > Ca2+ in the granite, whereas anions as HCO3->Cl>SO42- and Cl>HCO3->SO42-, respectively. Hydrochemical processes were identified with the helps of ion exchange, carbonate weathering and dissolution, multiple ionic ratios, and silicate weathering, which shown the predominance of carbonate, dolomite, calcite and silicate (anorthite) weathering in basalt, but in granite, silicate (alkali feldspar) weathering was dominated. Factor analysis also showed that there were multiple processes acting on groundwaters, were separated from the main cluster. Salinity, Sodium Absorption Ratio (SAR), Soluble Sodium Percentage (SSP), Residual Sodium Carbonate (RSC), Kelley's Ratio (KR) and Permeability Index (PI) in well samples showed that groundwater in basalt was more suitable for irrigation purposes. Further, a digital elevation model (DEM) was generated using Global mapper (8.0 version) software, which aided to decipher the thickness of basalt trap, and vertical transition zone of basaltic (trap) and granitic (basement) aquifer at this DVP comprising with the well depths and groundwater chemistry.

  19. Sill emplacement and corresponding ground deformation processes at the Alu-Dalafilla volcanic centre in the Danakil Depression, Ethiopia

    Science.gov (United States)

    Magee, Craig; Bastow, Ian; Hetherington, Rachel; van Wyk de Vries, Ben; Jackson, Christopher

    2016-04-01

    evaporitic host rock sequence. Important consequences of the shift to sill-dominated magmatism in the Danakil Depression include: (i) roof uplift induced by sill intrusion may not directly relate to the emplaced magma volume if intrusion promotes ductile deformation of the host evaporitic sequence (Schofield et al. 2014), implying that InSAR studies of ground deformation, crucial to volcanic hazard assessment, may under-estimate intruded magma volumes; and (ii) sill volumes are not incorporated into total melt volume estimates, which are used to constrain lithospheric processes active during continental break-up.

  20. Deconvolving the process-origin of sediments on volcanic mountains and implications for paleoclimatic reconstruction: Mt Ruapehu area, New Zealand

    Science.gov (United States)

    Brook, Martin; Winkler, Stefan

    2016-04-01

    Glaciation on the central North Island of New Zealand is limited to the volcanoes of Tongariro National Park, including Mt Ruapehu, the largest and most active andesitic stratovolcano on the North Island. At 2797 m asl, Mt Ruapehu represents the only peak in the North Island to currently intercept the permanent snowline, with small cirque glaciers descending to an altitude of ~2300 m. During the last glacial maximum (LGM), small ice-caps existed on Mt Ruapehu and the Tongariro Massif (15 km to the NNE of Ruapehu), with a series of small (cirque glaciers, consists mainly of incorporated fluvial material. Following deposition, reworking is mainly by proglacial streams, debris flows and lahars. Within the vicinity of glaciers, the dominant facies appear to be: (i) bouldery gravel with angular clasts on steep slopes surrounding glaciers, (ii) silty-sandy boulder gravel, with mainly subangular clasts, forming lateral moraines, (iii) boulder/cobble gravel with mainly subrounded clasts and associated laminated sediments representing fluvially-reworked material; and (iv) debris-avalanche deposits including fragmental rock clasts with an unsorted inter-clast matrix. As some of these deposits appear to include unambiguous indicators of glacial transport, interpretation of unconsolidated debris ridges on volcanic mountains should not necessarily exclude the contribution of glacial processes.

  1. Peripheral nerve regeneration with conduits: use of vein tubes

    Directory of Open Access Journals (Sweden)

    Rodrigo Guerra Sabongi

    2015-01-01

    Full Text Available Treatment of peripheral nerve injuries remains a challenge to modern medicine due to the complexity of the neurobiological nerve regenerating process. There is a greater challenge when the transected nerve ends are not amenable to primary end-to-end tensionless neurorraphy. When facing a segmental nerve defect, great effort has been made to develop an alternative to the autologous nerve graft in order to circumvent morbidity at donor site, such as neuroma formation, scarring and permanent loss of function. Tubolization techniques have been developed to bridge nerve gaps and have been extensively studied in numerous experimental and clinical trials. The use of a conduit intends to act as a vehicle for moderation and modulation of the cellular and molecular ambience for nerve regeneration. Among several conduits, vein tubes were validated for clinical application with improving outcomes over the years. This article aims to address the investigation and treatment of segmental nerve injury and draw the current panorama on the use of vein tubes as an autogenous nerve conduit.

  2. Anisotropy of magnetic susceptibility in welded tuffs: application to a welded-tuff dyke in the tertiary Trans-Pecos Texas volcanic province, USA

    Science.gov (United States)

    Wolff, John A.; Ellwood, Brooks B.; Sachs, Scott D.

    1989-06-01

    Consideration of published anisotropy of magnetic susceptibility (AMS) studies on welded ignimbrites suggests that AMS fabrics are controlled by groundmass microlites distributed within the existing tuff fabric, the sum result of directional fabrics imposed by primary flow lineation, welding, and (if relevant) rheomorphism. AMS is a more sensitive indicator of fabric elements within welded tuffs than conventional methods, and usually yields primary flow azimuth estimates. Detailed study of a single densely welded tuff sample demonstrates that the overall AMS fabric is insensitive to the relative abundances of fiamme, matrix and lithics within individual drilled cores. AMS determinations on a welded-tuff dyke occurring in a choked vent in the Trans-Pecos Texas volcanic field reveals a consistent fabric with a prolate element imbricated with respect to one wall of the dyke, while total magnetic susceptibility and density exhibit axially symmetric variations across the dyke width. The dyke is interpreted to have formed as a result of agglutination of the erupting mixture on a portion of the conduit wall as it failed and slid into the conduit, followed by residual squeezing between the failed block and in situ wallrock. Irrespective of the precise mechanism, widespread occurrence of both welded-tuff dykes and point-welded, aggregate pumices in pyroclastic deposits may imply that lining of conduit walls by agglutionation during explosive volcanic eruptions is a common process.

  3. Volcanism on Mars. Chapter 41

    Science.gov (United States)

    Zimbelman, J. R.; Garry, W. B.; Bleacher, J. E.; Crown, D. A.

    2015-01-01

    Spacecraft exploration has revealed abundant evidence that Mars possesses some of the most dramatic volcanic landforms found anywhere within the solar system. How did a planet half the size of Earth produce volcanoes like Olympus Mons, which is several times the size of the largest volcanoes on Earth? This question is an example of the kinds of issues currently being investigated as part of the space-age scientific endeavor called "comparative planetology." This chapter summarizes the basic information currently known about volcanism on Mars. The volcanoes on Mars appear to be broadly similar in overall morphology (although, often quite different in scale) to volcanic features on Earth, which suggests that Martian eruptive processes are not significantly different from the volcanic styles and processes on Earth. Martian volcanoes are found on terrains of different age, and Martian volcanic rocks are estimated to comprise more than 50% of the Martian surface. This is in contrast to volcanism on smaller bodies such as Earth's Moon, where volcanic activity was mainly confined to the first half of lunar history (see "Volcanism on the Moon"). Comparative planetology supports the concept that volcanism is the primary mechanism for a planetary body to get rid of its internal heat; smaller bodies tend to lose their internal heat more rapidly than larger bodies (although, Jupiter's moon Io appears to contradict this trend; Io's intense volcanic activity is powered by unique gravitational tidal forces within the Jovian system; see "Volcanism on Io"), so that volcanic activity on Mars would be expected to differ considerably from that found on Earth and the Moon.

  4. A biosynthetic nerve guide conduit based on silk/SWNT/fibronectin nanocomposite for peripheral nerve regeneration.

    Science.gov (United States)

    Mottaghitalab, Fatemeh; Farokhi, Mehdi; Zaminy, Arash; Kokabi, Mehrdad; Soleimani, Masoud; Mirahmadi, Fereshteh; Shokrgozar, Mohammad Ali; Sadeghizadeh, Majid

    2013-01-01

    As a contribution to the functionality of nerve guide conduits (NGCs) in nerve tissue engineering, here we report a conduit processing technique through introduction and evaluation of topographical, physical and chemical cues. Porous structure of NGCs based on freeze-dried silk/single walled carbon nanotubes (SF/SWNTs) has shown a uniform chemical and physical structure with suitable electrical conductivity. Moreover, fibronectin (FN) containing nanofibers within the structure of SF/SWNT conduits produced through electrospinning process have shown aligned fashion with appropriate porosity and diameter. Moreover, fibronectin remained its bioactivity and influenced the adhesion and growth of U373 cell lines. The conduits were then implanted to 10 mm left sciatic nerve defects in rats. The histological assessment has shown that nerve regeneration has taken places in proximal region of implanted nerve after 5 weeks following surgery. Furthermore, nerve conduction velocities (NCV) and more myelinated axons were observed in SF/SWNT and SF/SWNT/FN groups after 5 weeks post implantation, indicating a functional recovery for the injured nerves. With immunohistochemistry, the higher S-100 expression of Schwann cells in SF/SWNT/FN conduits in comparison to other groups was confirmed. In conclusion, an oriented conduit of biocompatible SF/SWNT/FN has been fabricated with acceptable structure that is particularly applicable in nerve grafts.

  5. A biosynthetic nerve guide conduit based on silk/SWNT/fibronectin nanocomposite for peripheral nerve regeneration.

    Directory of Open Access Journals (Sweden)

    Fatemeh Mottaghitalab

    Full Text Available As a contribution to the functionality of nerve guide conduits (NGCs in nerve tissue engineering, here we report a conduit processing technique through introduction and evaluation of topographical, physical and chemical cues. Porous structure of NGCs based on freeze-dried silk/single walled carbon nanotubes (SF/SWNTs has shown a uniform chemical and physical structure with suitable electrical conductivity. Moreover, fibronectin (FN containing nanofibers within the structure of SF/SWNT conduits produced through electrospinning process have shown aligned fashion with appropriate porosity and diameter. Moreover, fibronectin remained its bioactivity and influenced the adhesion and growth of U373 cell lines. The conduits were then implanted to 10 mm left sciatic nerve defects in rats. The histological assessment has shown that nerve regeneration has taken places in proximal region of implanted nerve after 5 weeks following surgery. Furthermore, nerve conduction velocities (NCV and more myelinated axons were observed in SF/SWNT and SF/SWNT/FN groups after 5 weeks post implantation, indicating a functional recovery for the injured nerves. With immunohistochemistry, the higher S-100 expression of Schwann cells in SF/SWNT/FN conduits in comparison to other groups was confirmed. In conclusion, an oriented conduit of biocompatible SF/SWNT/FN has been fabricated with acceptable structure that is particularly applicable in nerve grafts.

  6. Rapid laccolith intrusion driven by explosive volcanic eruption

    Science.gov (United States)

    Castro, Jonathan M.; Cordonnier, Benoit; Schipper, C. Ian; Tuffen, Hugh; Baumann, Tobias S.; Feisel, Yves

    2016-11-01

    Magmatic intrusions and volcanic eruptions are intimately related phenomena. Shallow magma intrusion builds subsurface reservoirs that are drained by volcanic eruptions. Thus, the long-held view is that intrusions must precede and feed eruptions. Here we show that explosive eruptions can also cause magma intrusion. We provide an account of a rapidly emplaced laccolith during the 2011 rhyolite eruption of Cordón Caulle, Chile. Remote sensing indicates that an intrusion began after eruption onset and caused severe (>200 m) uplift over 1 month. Digital terrain models resolve a laccolith-shaped body ~0.8 km3. Deformation and conduit flow models indicate laccolith depths of only ~20-200 m and overpressures (~1-10 MPa) that likely stemmed from conduit blockage. Our results show that explosive eruptions may rapidly force significant quantities of magma in the crust to build laccoliths. These iconic intrusions can thus be interpreted as eruptive features that pose unique and previously unrecognized volcanic hazards.

  7. Variability of permeability with diameter of conduit

    Indian Academy of Sciences (India)

    J A Adegoke; J A Olowofela

    2008-05-01

    An entry length is always observed before laminar flow is achieved in fluid flowing in a conduit. This depends on the Reynolds number of the flow and the degree of smoothness of the conduit. This work examined this region and the point where laminar flow commences in the context of flow through conduit packed with porous material like beads, of known porosity. Using some theoretical assumptions, it is demonstrated that permeability varies from zero at wall-fluid boundary to maximum at mid-stream, creating a permeability profile similar to the velocity profile. An equation was obtained to establish this. We also found that peak values of permeability increase with increasing porosity, and therefore entry length increases with increasing porosity with all other parameters kept constant. A plot of peak permeability versus porosity revealed that they are linearly related.

  8. The earliest open conduit eruptive center of the Etnean region: evidence from aeromagnetic, geophysical, and geological data

    Science.gov (United States)

    Nicolosi, Iacopo; D'Ajello Caracciolo, Francesca; Branca, Stefano; Ferlito, Carmelo; Chiappini, Massimo

    2016-07-01

    At Mount Etna, the present-day active volcano is an open conduit structure characterized by continuous eruptive activity. Such conditions have been thought unique in the evolution of the Etnean volcano as well as in the Mediterranean region. However, a review study of available geophysical data and models, combined with geological records, petrographic and geochemical considerations, has led us to consider that a large area of about 28 km2 located in Val Calanna, on the eastern side of Valle del Bove, can be interpreted as the site of an old open conduit volcano. A dyke swarm outcrops in the area, whose deep alteration and fumarolization can be attributed to the sustained passage of volcanic gases over long periods. Radiometric dating yields an age of about 129 ka. This finding sheds new light on the evolution of Mount Etna volcano, indicating that the tectonic conditions leading to an open conduit volcano must also have been active in the past.

  9. Chitosan Conduit for Peripheral Nerve Regeneration

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Chitosan, the N-deacetylated form of chitin, has good biocompatibility and biodegradability.This paper investigates the feasibility of using chitosan conduits for peripheral nerve regeneration.Cell culture experiments were used to test the material's cytotoxicity and affinity to nerve cells.Conduit implantation experiments were used to study the degradation of the material and the regeneration of injured sciatic nerves.The primary results indicate that chitosan has good mechanical properties, biocompatibility, and biodegradability and it may be a promising biomaterial for peripheral nerve regeneration.

  10. Groundwater flow processes and mixing in active volcanic systems: the case of Guadalajara (Mexico

    Directory of Open Access Journals (Sweden)

    A. Hernández-Antonio

    2015-02-01

    Full Text Available Groundwater chemistry and isotopic data from 40 production wells in the Atemajac and Toluquilla Valleys, located in and around the Guadalajara metropolitan area, were determined to develop a conceptual model of groundwater flow processes and mixing. Multivariate analysis including cluster analysis and principal component analysis were used to elucidate distribution patterns of constituents and factors controlling groundwater chemistry. Based on this analysis, groundwater was classified into four groups: cold groundwater, hydrothermal water, polluted groundwater and mixed groundwater. Cold groundwater is characterized by low temperature, salinity, and Cl and Na concentrations and is predominantly of Na-HCO3 type. It originates as recharge at Primavera caldera and is found predominantly in wells in the upper Atemajac Valley. Hydrothermal water is characterized by high salinity, temperature, Cl, Na, HCO3, and the presence of minor elements such as Li, Mn and F. It is a mixed HCO3 type found in wells from Toluquilla Valley and represents regional flow circulation through basaltic and andesitic rocks. Polluted groundwater is characterized by elevated nitrate and sulfate concentrations and is usually derived from urban water cycling and subordinately from agricultural practices. Mixed groundwaters between cold and hydrothermal components are predominantly found in the lower Atemajac Valley. Tritium method elucidated that practically all of the sampled groundwater contains at least a small fraction of modern water. The multivariate mixing model M3 indicates that the proportion of hydrothermal fluids in sampled well water is between 13 (local groundwater and 87% (hydrothermal water, and the proportion of polluted water in wells ranges from 0 to 63%. This study may help local water authorities to identify and quantify groundwater contamination and act accordingly.

  11. Dating of the late Quaternary volcanic events using Uranium-series technique on travertine deposit: A case study in Ihlara, Central Anatolia Volcanic Province

    Science.gov (United States)

    Karabacak, Volkan; Tonguç Uysal, İ.; Ünal-İmer, Ezgi

    2016-04-01

    Dating of late Quaternary volcanism is crucial to understanding of the recent mechanism of crustal deformation and future volcanic explosivity risk of the region. However, radiometric dating of volcanic products has been a major challenge because of high methodological error rate. In most cases, there are difficulties on discrimination of the volcanic lava flow relations in the field. Furthermore, there would be unrecorded and unpreserved volcanoclastic layers by depositional and erosional processes. We present a new method that allows precise dating of late Quaternary volcanic events (in the time range of 0-500,000 years before present) using the Uranium-series technique on travertine mass, which is thought to be controlled by the young volcanism. Since the high pressure CO2 in the spring waters are mobilized during crustal strain cycles and the carbonates are precipitated in the fissures act as conduit for hot springs, thus, travertine deposits provide important information about crustal deformation. In this study we studied Ihlara fissure ridge travertines in the Central Anatolia Volcanic Province. This region is surrounded by many eruption centers (i.e. Hasandaǧı, Acıgöl and Göllüdaǧı) known as the late Quaternary and their widespread volcanoclastic products. Recent studies have suggested at least 11 events at around Acıgöl Caldera for the last 180 ka and 2 events at Hasandaǧı Stratovolcano for the last 30 ka. Active travertine masses around Ihlara deposited from hotwaters, which rise up through deep-penetrated fissures in volcanoclastic products of surrounding volcanoes. Analyses of the joint systems indicate that these vein structures are controlled by the crustal deformation due to young volcanism in the vicinity. Thus, the geological history of Ihlara travertine mass is regarded as a record of surrounding young volcanism. We dated 9 samples from 5 ridge-type travertine masses around Ihlara region. The age distribution indicates that the crustal

  12. Strontium isotopes provide clues for a process shift in base cation dynamics in young volcanic soils

    Science.gov (United States)

    Bingham, N.; Jackson, M. G.; Bookhagen, B.; Maher, K.; Chadwick, O.

    2015-12-01

    Despite advances in soil development theory based on studies of old soils or over long timescales, little is known about soil thresholds (dramatic changes in soil properties associated with only small shifts in external forcing factors) that might be expressed in young soils (less than 10 kyr). Therefore, we seek to understand infant soil development in a tropical environment through the sourcing of plant available base cations by measuring the strontium (Sr) isotopic composition of the soil exchange complex. Our sampling strategy spans soils in three different precipitation ranges (950-1060 mm, 1180-1210 mm, and 1450-1500) and an array of soil ages from 500 to 7500 years in the Kona region on the island of Hawaii. In Hawaiian soils, 87Sr/86Sr values are determined by a mixture of three components: a mantle-derived component from the lava (0.7034), a rainfall component (0.7093) and a component from continental dust (0.720). Elevation-controlled leaching intensity in the wettest localities produces a decline in the concentration of base cations supplied by basalt and a dilute resupply by rainfall. In the driest sites, where leaching intensity is dramatically reduced, there is a buildup of rainfall-derived extractable Sr in the soil over time. Slow rock weathering rates produce a small rock-derived cation input to the soil. Thus, Sr isotope signatures reflect both the input of rainfall-derived cations and rock-derived cations with values that fall between rainfall and basaltic signatures. Soils in the intermediate precipitation range have Sr isotopic signatures consistent with both the wet and dry trends; suggesting that they lie close to the critical precipitation amount that marks a shift between these two processes. For the Kona region, this transition seems to occur at 1200 mm /yr. In contrast to the clear-cut differentiation in strontium isotopes with precipitation shifts observed in older soils, patterns on these young soils in Kona are complicated by low soil

  13. Hawaiian fissure fountains: Quantifying vent and shallow conduit geometry, episode 1 of the 1969-1974 Mauna Ulu eruption: Chapter 17

    Science.gov (United States)

    Parcheta, Carolyn; Fagents, Sarah; Swanson, Donald A.; Houghton, Bruce; Ericksen, Todd; Carey, Rebecca; Cayol, Valérie; Poland, Michael P.; Weis, Dominique

    2015-01-01

    Geometries of shallow magmatic pathways feeding volcanic eruptions are poorly constrained, yet many key interpretations about eruption dynamics depend on knowledge of these geometries. Direct quantification is difficult because vents typically become blocked with lava at the end of eruptions. Indirect geophysical techniques have shed light on some volcanic conduit geometries, but the scales are too coarse to resolve narrow fissures (widths typically 1 m). Kīlauea's Mauna Ulu eruption, which started with 30 m. Direct measurements at the ground surface were augmented by tripod-mounted lidar measurements to quantify the shallow conduit geometry for three vents at a resolution factors influencing these parameters. In the past, simplified first-order fissure geometries have been used in computational modeling. Our data can provide more accurate conduit shapes for better understanding of shallow fissure fluid dynamics and how it controls eruptive behavior, especially if incorporated into computer models.

  14. In vitro evaluation of carbon-nanotube-reinforced bioprintable vascular conduits

    Science.gov (United States)

    Dolati, Farzaneh; Yu, Yin; Zhang, Yahui; De Jesus, Aribet M.; Sander, Edward A.; Ozbolat, Ibrahim T.

    2014-04-01

    Vascularization of thick engineered tissue and organ constructs like the heart, liver, pancreas or kidney remains a major challenge in tissue engineering. Vascularization is needed to supply oxygen and nutrients and remove waste in living tissues and organs through a network that should possess high perfusion ability and significant mechanical strength and elasticity. In this paper, we introduce a fabrication process to print vascular conduits directly, where conduits were reinforced with carbon nanotubes (CNTs) to enhance their mechanical properties and bioprintability. In vitro evaluation of printed conduits encapsulated in human coronary artery smooth muscle cells was performed to characterize the effects of CNT reinforcement on the mechanical, perfusion and biological performance of the conduits. Perfusion and permeability, cell viability, extracellular matrix formation and tissue histology were assessed and discussed, and it was concluded that CNT-reinforced vascular conduits provided a foundation for mechanically appealing constructs where CNTs could be replaced with natural protein nanofibers for further integration of these conduits in large-scale tissue fabrication.

  15. Comparison of a karst groundwater model with and without discrete conduit flow

    Science.gov (United States)

    Saller, Stephen P.; Ronayne, Michael J.; Long, Andrew J.

    2013-01-01

    Karst aquifers exhibit a dual flow system characterized by interacting conduit and matrix domains. This study evaluated the coupled continuum pipe-flow framework for modeling karst groundwater flow in the Madison aquifer of western South Dakota (USA). Coupled conduit and matrix flow was simulated within a regional finite-difference model over a 10-year transient period. An existing equivalent porous medium (EPM) model was modified to include major conduit networks whose locations were constrained by dye-tracing data and environmental tracer analysis. Model calibration data included measured hydraulic heads at observation wells and estimates of discharge at four karst springs. Relative to the EPM model, the match to observation well hydraulic heads was substantially improved with the addition of conduits. The inclusion of conduit flow allowed for a simpler hydraulic conductivity distribution in the matrix continuum. Two of the high-conductivity zones in the EPM model, which were required to indirectly simulate the effects of conduits, were eliminated from the new model. This work demonstrates the utility of the coupled continuum pipe-flow method and illustrates how karst aquifer model parameterization is dependent on the physical processes that are simulated.

  16. Impact of volcanic processes on the cryospheric system of the Peteroa Volcano, Andes of southern Mendoza, Argentina

    Science.gov (United States)

    Liaudat, Dario Trombotto; Penas, Pablo; Aloy, Gustavo

    2014-03-01

    Soil temperatures of the active Volcanic Complex Peteroa situated in the Cordillera Principal between Chile and Argentina at 35°15‧ S and 70°35‧ W (approximately) were monitored in the area, and local geomorphology (periglacial geomorphology, presence of permafrost, and cryoforms) was studied. The present contribution also resulted in a comparison of two consecutive analyses of the volcano peak carried out with special thermocameras (AGEMA TVH 550, FUR P660) in order to study the thermal range of different hot and cold sites selected in 2009. The thermocameras were used ascending by foot and also during flights with a Cessna 180. A night expedition to the volcanic avalanche caldera, at up to 3900 m asl (approximately), completed the monitoring activity of 2010. Hot zones were associated to present volcanism and cold zones to the presence of glacier ice and shadowy slopes with possible presence of permafrost. Identifying and mapping uncovered and covered ice was possible with the help of monitoring and geomorphological interpretation related to the upper englacement, which is severely affected by volcanism. Glaciers are retreating toward the north or approaching the rims of the volcanic avalanche caldera leaving islands of ice associated with superficial permafrost. The cryogenic area with slope permafrost was identified through active protalus and sedimentary cryogenic slopes. Craters have undergone considerable thermal changes in comparison to the year 2009; and new, much more vigorous fumaroles have appeared in hot areas detected in 2009 following a tendency toward the west. New subaquatic heat columns that appeared in crater 3, crater walls, and glaciated areas vanished, supplying cold water and thus contributing to the formation of a new lake in crater 4. A possible post-seismic shift of the volcanic activity may provide geodynamical evidence of the changes registered in other areas after the earthquake of 27 February 2010.

  17. What Controls the Sizes and Shapes of Volcanic Ash? Integrating Morphological, Textural and Geochemical Ash Properties to Decipher Eruptive Processes

    Science.gov (United States)

    Liu, E. J.; Cashman, K. V.; Rust, A.

    2015-12-01

    Volcanic ash particles encompass a diverse spectrum of shapes as a consequence of differences in the magma properties and the magma ascent and eruption conditions. We show how the quantitative analysis of ash particle shapes can be a valuable tool for deciphering magma fragmentation and transport processes. Importantly, integrating morphological data with ash texture (e.g. bubble and crystal sizes) and dissolved volatile data provides valuable insights into the physical and chemical controls on the resulting ash deposit. To explore the influence of magma-water interaction (MWI) on fine ash generation, we apply this multi-component characterisation to tephra from the 2500BC Hverfjall Fires, Iceland. Here, coeval fissure vents spanned sub-aerial to shallow lacustrine environments. Differences in the size and morphology of pyroclasts thus reflect fragmentation mechanisms under different near-surface conditions. Using shape parameters sensitive to both particle roughness and internal vesicularity, we quantify the relative proportions of dense fragments, bubble shards, and vesicular grains from 2-D SEM images. We show that componentry (and particle morphology) varies as a function of grain size, and that this variation can be related back to the bubble size distribution. Although both magmatic and hydromagmatic deposits exhibit similar component assemblages, they differ in how these assemblages change with grain size. These results highlight the benefits of characterising ash deposits over a wide range of grain sizes, and caution against inferring fragmentation mechanism from a narrow grain size range. Elevated matrix glass S concentrations in hydromagmatic ash (600-1500 ppm) compared to those in magmatic ash and scoria lapilli (200-500 ppm) indicate interrupted vesiculation. In contrast to the subaerial 'dry' deposits, fragmentation during MWI likely occurred over a greater range of depths with quench rates sufficient to prevent post-fragmentation degassing. High

  18. Controlling Wavebreaking in a Viscous Fluid Conduit

    Science.gov (United States)

    Anderson, Dalton; Maiden, Michelle; Hoefer, Mark

    2015-11-01

    This poster will present a new technique in the experimental investigation of dispersive hydrodynamics. In shallow water flows, internal ocean waves, superfluids, and optical media, wave breaking can be resolved by a dispersive shock wave (DSW). In this work, an experimental method to control the location of DSW formation (gradient catastrophe) is explained. The central idea is to convert an initial value problem (Riemann problem) into an equivalent boundary value problem. The system to which this technique is applied is a fluid conduit resulting from high viscosity contrast between a buoyant interior and heavier exterior fluid. The conduit cross-sectional area is modeled by a nonlinear, conservative, dispersive, third order partial differential equation. Using this model, the aim is to predict the breaking location of a DSW by controlling one boundary condition. An analytical expression for this boundary condition is derived by solving the dispersionless equation backward in time from the desired step via the method of characteristics. This is used in experiment to generate an injection rate profile for a high precision piston pump. This translates to the desired conduit shape. Varying the jump height and desired breaking location indicates good control of DSW formation. This result can be improved by deriving a conduit profile by numerical simulation of the full model equation. Controlling the breaking location of a DSW allows for the investigation of dynamics independent of the boundary. Support provided by NSF CAREER DMS-1255422 , NSF EXTREEMS.

  19. Biochemical engineering nerve conduits using peptide amphiphiles.

    Science.gov (United States)

    Tan, Aaron; Rajadas, Jayakumar; Seifalian, Alexander M

    2012-11-10

    Peripheral nerve injury is a debilitating condition. The gold standard for treatment is surgery, requiring an autologous nerve graft. Grafts are harvested from another part of the body (a secondary site) to treat the affected primary area. However, autologous nerve graft harvesting is not without risks, with associated problems including injury to the secondary site. Research into biomaterials has engendered the use of bioartificial nerve conduits as an alternative to autologous nerve grafts. These include synthetic and artificial materials, which can be manufactured into nerve conduits using techniques inspired by nanotechnology. Recent evidence indicates that peptide amphiphiles (PAs) are promising candidates for use as materials for bioengineering nerve conduits. PAs are biocompatible and biodegradable protein-based nanomaterials, capable of self-assembly in aqueous solutions. Their self-assembly system, coupled with their intrinsic capacity for carrying bioactive epitopes for tissue regeneration, form particularly novel attributes for biochemically-engineered materials. Furthermore, PAs can function as biomimetic materials and advanced drug delivery platforms for sustained and controlled release of a plethora of therapeutic agents. Here we review the realm of nerve conduit tissue engineering and the potential for PAs as viable materials in this exciting and rapidly advancing field. Copyright © 2012 Elsevier B.V. All rights reserved.

  20. Coupled conduit and atmospheric dispersal dynamics of the AD 79 Plinian eruption of Vesuvius

    Science.gov (United States)

    Neri, Augusto; Papale, Paolo; Del Seppia, Dario; Santacroce, Roberto

    2003-01-01

    The AD 79 eruption of Vesuvius is certainly one of the most investigated explosive eruptions in the world. This makes it particularly suitable for the application of numerical models since we can be quite confident about input data, and the model predictions can be compared with field-based reconstruction of the eruption dynamics. Magma ascent along the volcanic conduit and the dispersal of pyroclasts in the atmosphere were simulated. The conduit and atmospheric domain were coupled through the flow conditions computed at the conduit exit. We simulated two different peak phases of the eruption which correspond to the emplacement of the white and gray magma types that produced Plinian fallout deposits with interlayered pyroclastic flow units during the gray phase. The input data, independently constrained and representative of each of the two eruptive phases, consist of liquid magma composition, crystal and water content, mass flow rate, and pressure-temperature-depth of the magma at the conduit entrance. A parametric study was performed on the less constrained variables such as microlite content of magma, pressure at the conduit entrance, and particle size representative of the eruptive mixture. Numerical results are substantially consistent with the reconstructed eruptive dynamics. In particular, the white eruption phase is found to lead to a fully buoyant eruption plume in all cases investigated, whereas the gray phase shows a more transitional character, i.e. the simultaneous production of a buoyant convective plume and pyroclastic surges, with a significant influence of the microlite content of magma in determining the partition of pyroclast mass between convective plumes and pyroclastic flows.

  1. A quantitative model for volcanic hazard assessment

    OpenAIRE

    W. Marzocchi; Sandri, L.; Furlan, C

    2006-01-01

    Volcanic hazard assessment is a basic ingredient for risk-based decision-making in land-use planning and emergency management. Volcanic hazard is defined as the probability of any particular area being affected by a destructive volcanic event within a given period of time (Fournier d’Albe 1979). The probabilistic nature of such an important issue derives from the fact that volcanic activity is a complex process, characterized by several and usually unknown degrees o...

  2. Time scales of foam stability in shallow conduits: Insights from analogue experiments

    Science.gov (United States)

    Spina, L.; Scheu, B.; Cimarelli, C.; Arciniega-Ceballos, A.; Dingwell, D. B.

    2016-10-01

    Volcanic systems can exhibit periodical trends in degassing activity, characterized by a wide range of time scales. Understanding the dynamics that control such periodic behavior can provide a picture of the processes occurring in the feeding system. Toward this end, we analyzed the periodicity of outgassing in a series of decompression experiments performed on analogue material (argon-saturated silicone oil plus glass beads/fibers) scaled to serve as models of basaltic magma. To define the effects of liquid viscosity and crystal content on the time scale of outgassing, we investigated both: (1) pure liquid systems, at differing viscosities (100 and 1000 Pa s), and (2) particle-bearing suspensions (diluted and semidiluted). The results indicate that under dynamic conditions (e.g., decompressive bubble growth and fluid ascent within the conduit), the periodicity of foam disruption may be up to several orders of magnitude less than estimates based on the analysis of static conditions. This difference in foam disruption time scale is inferred to result from the contribution of bubble shear and bubble growth to inter-bubble film thinning. The presence of particles in the semidiluted regime is further linked to shorter bubble bursting times, likely resulting from contributions of the presence of a solid network and coalescence processes to the relative increase in bubble breakup rates. Finally, it is argued that these experiments represent a good analogue of gas-piston activity (i.e., the periodical rise-and-fall of a basaltic lava lake surface), implying a dominant role for shallow foam accumulation as a source process for these phenomena.

  3. Drill pipes and casings utilizing multi-conduit tubulars

    Energy Technology Data Exchange (ETDEWEB)

    Curlett, H.B.

    1989-01-24

    A seal adapted for use with a multi-conduit well tubular, or the like, is described which consists of: a plate with fluid passages, each passage corresponding to an opening of a conduit of the multiconduit tubular, and a groove on the plate around each passage; and elastomer means partially embeddable into each groove for sealing each conduit of a tubular to a corresponding conduit of another similar tubular.

  4. The 2010 Eyja eruption evolution by using IR satellite sensors measurements: retrieval comparison and insights into explosive volcanic processes

    Science.gov (United States)

    Piscini, A.; Corradini, S.; Merucci, L.; Scollo, S.

    2010-12-01

    The 2010 April-May Eyja eruption caused an unprecedented disruption to economic, political and cultural activities in Europe and across the world. Because of the harming effects of fine ash particles on aircrafts, many European airports were in fact closed causing millions of passengers to be stranded, and with a worldwide airline industry loss estimated of about 2.5 billion Euros. Both security and economical issues require robust and affordable volcanic cloud retrievals that may be really improved through the intercomparison among different remote sensing instruments. In this work the Thermal InfraRed (TIR) measurements of different polar and geostationary satellites instruments as the Moderate Resolution Imaging Spectroradiometer (MODIS), the Advanced Very High Resolution Radiometer (AVHRR) and the Spin Enhanced Visible and Infrared Imager (SEVIRI), have been used to retrieve the volcanic ash and SO2 in the entire eruption period over Iceland. The ash retrievals (mass, AOD and effective radius) have been carried out by means of the split window BTD technique using the channels centered around 11 and 12 micron. The least square fit procedure is used for the SO2 retrieval by using the 7.3 and 8.7 micron channels. The simulated TOA radiance Look-Up Table (LUT) needed for both the ash and SO2 column abundance retrievals have been computed using the MODTRAN 4 Radiative Transfer Model. Further, the volcanic plume column altitude and ash density have been computed and compared, when available, with ground observations. The results coming from the retrieval of different IR sensors show a good agreement over the entire eruption period. The column height, the volcanic ash and the SO2 emission trend confirm the indentified different phases occurred during the Eyja eruption. We remark that the retrieved volcanic plume evolution can give important insights into eruptive dynamics during long-lived explosive activity.

  5. Volcanic gas

    Science.gov (United States)

    McGee, Kenneth A.; Gerlach, Terrance M.

    1995-01-01

    In Roman mythology, Vulcan, the god of fire, was said to have made tools and weapons for the other gods in his workshop at Olympus. Throughout history, volcanoes have frequently been identified with Vulcan and other mythological figures. Scientists now know that the “smoke" from volcanoes, once attributed by poets to be from Vulcan’s forge, is actually volcanic gas naturally released from both active and many inactive volcanoes. The molten rock, or magma, that lies beneath volcanoes and fuels eruptions, contains abundant gases that are released to the surface before, during, and after eruptions. These gases range from relatively benign low-temperature steam to thick hot clouds of choking sulfurous fume jetting from the earth. Water vapor is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide. Other volcanic gases are hydrogen sulfide, hydrochloric acid, hydrogen, carbon monoxide, hydrofluoric acid, and other trace gases and volatile metals. The concentrations of these gas species can vary considerably from one volcano to the next.

  6. Sentinel-1 automatic processing chain for volcanic and seismic areas monitoring within the Geohazards Exploitation Platform (GEP)

    Science.gov (United States)

    De Luca, Claudio; Zinno, Ivana; Manunta, Michele; Lanari, Riccardo; Casu, Francesco

    2016-04-01

    The microwave remote sensing scenario is rapidly evolving through development of new sensor technology for Earth Observation (EO). In particular, Sentinel-1A (S1A) is the first of a sensors' constellation designed to provide a satellite data stream for the Copernicus European program. Sentinel-1A has been specifically designed to provide, over land, Differential Interferometric Synthetic Aperture Radar (DInSAR) products to analyze and investigate Earth's surface displacements. S1A peculiarities include wide ground coverage (250 km of swath), C-band operational frequency and short revisit time (that will reduce from 12 to 6 days when the twin system Sentinel-1B will be placed in orbit during 2016). Such characteristics, together with the global coverage acquisition policy, make the Sentinel-1 constellation to be extremely suitable for volcanic and seismic areas studying and monitoring worldwide, thus allowing the generation of both ground displacement information with increasing rapidity and new geological understanding. The main acquisition mode over land is the so called Interferometric Wide Swath (IWS) that is based on the Terrain Observation by Progressive Scans (TOPS) technique and that guarantees the mentioned S1A large coverage characteristics at expense of a not trivial interferometric processing. Moreover, the satellite spatial coverage and the reduced revisit time will lead to an exponential increase of the data archives that, after the launch of Sentine-1B, will reach about 3TB per day. Therefore, the EO scientific community needs from the one hand automated and effective DInSAR tools able to address the S1A processing complexity, and from the other hand the computing and storage capacities to face out the expected large amount of data. Then, it is becoming more crucial to move processors and tools close to the satellite archives, being not efficient anymore the approach of downloading and processing data with in-house computing facilities. To address

  7. Volcanic spreading forcing and feedback in geothermal reservoir development, Amiata Volcano, Italia

    Science.gov (United States)

    Borgia, Andrea; Mazzoldi, Alberto; Brunori, Carlo Alberto; Allocca, Carmine; Delcroix, Carlo; Micheli, Luigi; Vercellino, Alberto; Grieco, Giovanni

    2014-09-01

    We made a stratigraphic, structural and morphologic study of the Amiata Volcano in Italy. We find that the edifice is dissected by intersecting grabens that accommodate the collapse of the higher sectors of the volcano. In turn, a number of compressive structures and diapirs exist around the margin of the volcano. These structures create an angular drainage pattern, with stream damming and captures, and a set of lakes within and around the volcano. We interpret these structures as the result of volcanic spreading of Amiata on its weak substratum, formed by the late Triassic evaporites (Burano Anhydrites) and the Middle-Jurassic to Early-Cretaceous clayey chaotic complexes (Ligurian Complex). Regional doming created a slope in the basement facilitating the outward flow and spreading of the ductile layers forced by the volcanic load. We model the dynamics of spreading with a scaled lubrication approximation of the Navier Stokes equations, and numerically study a set of solutions. In the model we include simple functions for volcanic deposition and surface erosion that change the topography over time. Scaling indicates that spreading at Amiata could still be active. The numerical solution shows that, as the central part of the edifice sinks into the weak basement, diapiric structures of the underlying formations form around the base of the volcano. Deposition of volcanic rocks within the volcano and surface erosion away from it both enhance spreading. In addition, a sloping basement may constitute a trigger for spreading and formation of trains of adjacent diapirs. As a feedback, the hot hydrothermal fluids decrease the shear strength of the anhydrites facilitating the spreading process. Finally, we observe that volcanic spreading has created ideal heat traps that constitute todays' exploited geothermal fields at Amiata. Normal faults generated by volcanic spreading, volcanic conduits, and direct contact between volcanic rocks (which host an extensive fresh

  8. Reactive bromine chemistry in Mt. Etna's volcanic plume: the influence of total Br, high temperature processing, aerosol loading and plume-air mixing

    Directory of Open Access Journals (Sweden)

    T. J. Roberts

    2014-03-01

    Full Text Available Volcanic emissions present a source of reactive halogens to the troposphere, through rapid plume chemistry that converts the emitted HBr to more reactive forms such as BrO. The nature of this process is poorly quantified, yet is of interest to understand volcanic impacts on the troposphere, and infer volcanic activity from volcanic gas measurements (i.e. BrO / SO2 ratios. Recent observations from Etna report an initial increase and subsequent plateau or decline in BrO / SO2 ratios with distance downwind. We present daytime PlumeChem model simulations that reproduce and explain the reported trend in BrO / SO2 at Etna including the initial rise and subsequent plateau. Through suites of model simulations we also investigate the influences of volcanic aerosol loading, bromine emission, and plume-air mixing rate on the downwind plume chemistry. Emitted volcanic HBr is converted into reactive bromine by autocatalytic bromine chemistry cycles whose onset is accelerated by the model high-temperature initialisation. These rapid chemistry cycles also impact the reactive bromine speciation through inter-conversion of Br, Br2, BrO, BrONO2, BrCl, HOBr. Formation of BrNO2 is also discussed. We predict a new evolution of Br-speciation in the plume, with BrO, Br2, Br and HBr as the main plume species in the near downwind plume whilst BrO, and HOBr are present in significant quantities further downwind (where BrONO2 and BrCl also make up a minor fraction. The initial rise in BrO / SO2 occurs as ozone is entrained into the plume whose reaction with Br promotes net formation of BrO. Aerosol has a modest impact on BrO / SO2 near-downwind (2 occurs as entrainment of oxidants HO2 and NO2 promotes net formation of HOBr and BrONO2, whilst the plume dispersion dilutes volcanic aerosol so slows the heterogeneous loss rates of these species. A higher volcanic aerosol loading enhances BrO / SO2 in the (> 6 km downwind plume. Simulations assuming low/medium and high Etna

  9. Mapping the Hawaiian plume conduit with converted seismic waves

    Science.gov (United States)

    Li; Kind; Priestley; Sobolev; Tilmann; Yuan; Weber

    2000-06-22

    The volcanic edifice of the Hawaiian islands and seamounts, as well as the surrounding area of shallow sea floor known as the Hawaiian swell, are believed to result from the passage of the oceanic lithosphere over a mantle hotspot. Although geochemical and gravity observations indicate the existence of a mantle thermal plume beneath Hawaii, no direct seismic evidence for such a plume in the upper mantle has yet been found. Here we present an analysis of compressional-to-shear (P-to-S) converted seismic phases, recorded on seismograph stations on the Hawaiian islands, that indicate a zone of very low shear-wave velocity (effects of the Hawaiian plume conduit in the asthenosphere and mantle transition zone with excess temperature of approximately 300 degrees C. Large variations in the transition-zone thickness suggest a lower-mantle origin of the Hawaiian plume similar to the Iceland plume, but our results indicate a 100 degrees C higher temperature for the Hawaiian plume.

  10. Segment-scale variations in seafloor volcanic and tectonic processes from multibeam sonar imaging, Mid-Atlantic Ridge Rainbow region (35°45'-36°35'N)

    Science.gov (United States)

    Eason, Deborah E.; Dunn, Robert A.; Pablo Canales, J.; Sohn, Robert A.

    2016-09-01

    Along-axis variations in melt supply and thermal structure can lead to significant variations in the mode of crustal accretion at mid-ocean ridges. We examine variations in seafloor volcanic and tectonic processes on the scale of individual ridge segments in a region of the slow spreading Mid-Atlantic Ridge (35°45'-36°35'N) centered on the Rainbow nontransform discontinuity (NTD). We use multibeam sonar backscatter amplitude data, taking advantage of multifold and multidirectional coverage from the MARINER geophysical study to create a gridded compilation of seafloor reflectivity, and interpret the sonar image within the context of other data to examine seafloor properties and identify volcanic flow fields and tectonic features. Along the spreading segments, differences in volcanic productivity, faulting, eruption style, and frequency correlate with inferred magma supply. Regions of low magma supply are associated with more widely spaced faults, and larger volcanic flow fields that are more easily identified in the backscatter image. Identified flow fields with the highest backscatter occur near the ends of ridge segments. Their relatively smooth topography contrasts with the more hummocky, cone-dominated terrain that dominates most of the neovolcanic zone. Patches of seafloor with high, moderately high, and low backscatter intensity across the Rainbow massif are spatially correlated with observations of basalt, gabbro and serpentinized peridotite, and sediment, respectively. Large detachment faults have repeatedly formed along the inside corners of the Rainbow NTD, producing a series of oceanic core complexes along the wake of the NTD. A new detachment fault is currently forming in the ridge segment just north of the now inactive Rainbow massif.

  11. The generation and evolution of anisotropic gas-permeability during viscous deformation in conduit-filling ignimbrites

    Science.gov (United States)

    Kolzenburg, Stephan; Russell, Kelly

    2015-04-01

    Gas-permeability plays a governing role in the pre-explosive pressurization of volcanic edifices. Pressurization may only occur once the total volume flux of gases emitted by an underlying magmatic or hydrothermal source exceeds the flow capacity of the permeable pathways present in the edifice. We have measured the physical properties (strain, porosity, permeability and ultrasonic wave velocities) of breadcrust bombs recovered from the deposits of the 2350 B.P. eruption of Mt Meager, BC, Canada. These rocks represent a conduit-infilling pyroclastic breccia that underwent various degrees of welding and deformation and present a remarkable opportunity to constrain the nature and timescale of mechanical processes operating within explosive volcanic conduits during repose periods between eruptive cycles. Here we present data from permeability measurements along the directions of maximum and minimum shortening which help quantifying the effect of vesicle microstructure on permeability. Permeability is measured by applying a range of confining pressures (between 3.4 and 17.2 MPa) to each sample and imposing a constant head (of 0.2 to 3.5 MPa) across the sample. The permeability is then determined using a modified version of Darcy's law applicable to compressible fluids. These rocks display a profound directionality in the measured physical properties resulting from the deformation-induced fabric. For all samples the permeability across the elongation fabric is highly correlated to the sample porosity whereas along the elongation fabric there is little effect of porosity on permeability. At porosity values of about 20% the permeability seems to reach a minimum at 10-16 m2 and does not change significantly with further reduction of porosity. Further, the effect of confining pressure on the permeability of these samples appears to be more pronounced across the elongation fabric than along the elongation fabric. The deformation fabric has a significant effect on the gas

  12. Polymeric Nerve Conduits with Contact Guidance Cues Used in Nerve Repair

    Institute of Scientific and Technical Information of China (English)

    G DAI; X NIU; J YIN

    2016-01-01

    In the modern life, the nerve injury frequently happens due to mechanical, chemical or thermal accidents. In the trivial injuries, the peripheral nerves can regenerate on their own; however, in most of the cases the clinical treatments are required, where relatively large nerve injury gaps are formed. Currently, the nerve repair can be accomplished by direct suture when the injury gap is not too large;while the autologous nerve graft working as the gold standard of peripheral nerve injury treatment for nerve injuries with larger gaps. However, the direct suture is limited by heavy tension at the suture sites, and the autologous nerve graft also has the drawbacks of donor site morbidity and insufifcient donor tissue. Recently, artiifcial nerve conduits have been developed as an alternative for clinical nerve repair to overcome the limitations associated with the above treatments. In order to further improve the efifciency of nerve conduits, various guidance cues are incorporated, including physical cues, biochemical signals, as well as support cells. First, this paper reviewed the contact guidance cues applied in nerve conduits, such as lumen ifllers, multi-channels and micro-patterns on the inner surface. Then, the paper focused on the polymeric nerve conduits with micro inner grooves. The polymeric nerve conduits were fabricated using the phase inversion-based ifber spinning techniques. The smart spinneret with grooved die was designed in the spinning platform, while different spinning conditions, including flow rates, air-gap distances, and polymer concentrations, were adjusted to investigate the inlfuence of fabrication conditions on the geometry of nerve conduits. The inner groove size in the nerve conduits can be precisely controlled in our hollow ifber spinning process, which can work as the efifcient contact guidance cue for nerve regeneration.

  13. Segment-scale variations in seafloor volcanic and tectonic processes in the Rainbow region, Mid-Atlantic Ridge (36º N)

    Science.gov (United States)

    Eason, D. E.; Dunn, R. A.; Arai, R.; Canales, J. P.; Sohn, R. A.

    2016-12-01

    Slow spreading ridges exhibit significant along-axis variations in melt supply and thermal structure. We examine variations in seafloor volcanic and tectonic processes at the scale of individual ridge segments in an area of the Mid-Atlantic Ridge (35º45'-36º35'N) centered on the Rainbow non-transform discontinuity (NTD). This study brings together results from seafloor geophysical mapping and deeper crustal imaging via 3-D seismic imaging from the MARINER experiment, along with existing lava compositional data, in order to examine magmatic processes. We use a gridded compilation of multifold, multidirectional sonar backscatter amplitude data to examine seafloor properties and identify volcanic flow fields and tectonic features. Regions of low magma supply are associated with thinner crust, more widely spaced faults and larger but less likely frequent volcanic flow fields. The neovolcanic zone is dominated by hummocky volcanic terrain, but a few of the highest backscatter flow fields occur near the ends of ridge segments and exhibit relatively smooth topography. Lava compositions from these flow fields suggest relatively high crystallization pressures, consistent with deep and/or intermittent magma storage. Unlike at faster spreading ridges, the seismic imaging does not show large zones of high temperature and partial melt beneath the axis. However, the regions with the lowest seismic velocities also exhibit the highest backscatter seafloor on average, consistent with recent volcanic activity. The transition to the mantle in the study area is gradual with no clear wide-angle reflections. Seismic velocities rapidly approach mantle-like values beneath Rainbow massif, consistent with the ultramafic and gabbroic material exposed on the surface there. Along the ridge axes, rotated crustal blocks bound by large offset normal faults dominate the abyssal hill topography, and are visible in the seismic images. Large detachment faults have repeatedly formed along the inside

  14. A kinematic model for the Plio-Quaternary evolution of the Tyrrhenian Apenninic system: implications for rifting processes and volcanism

    Science.gov (United States)

    Turco, E.; Zuppetta, A.

    1998-06-01

    During the frontal accretion due to the Late Miocene-Quaternary thrusting, the interior of the Apenninic chain underwent large-scale extension which produced the opening of the Tyrrhenian Oceanic Basin, a back-arc basin in respect to the late Cenozoic Apenninic chain, and the onset of the Quaternary volcanic activity in the Campanian Plain and more generally in the Tyrrhenian area. To outline the space/time distribution and the geotectonic setting of the Tyrrhenian volcanics we approached the problem from a kinematic point of view. A synthesis of the available geological and geophysical data leads us to suggest that the progressive migration of the Apenninic Arcs is responsible for the extension phenomena which took place during the last 5 Ma. At first, the extension resulted from the kinematic interaction between the Northern Apenninic Arc and the Southern Apenninic Arc during the Late Pliocene. Then, from the Early Pleistocene the extension was controlled by the SE migration of the Southern arc only, and therefore it can be regarded as part of the general Southern Tyrrhenian extension phenomenon. Due to the intense thinning, the isotherms migrated upward very rapidly within the Toscana, Latium and Campania lithosphere where the melting point was reached, giving rise to the onset of volcanic activity at the end of the Early Pleistocene.

  15. Volcanic activity: a review for health professionals.

    Science.gov (United States)

    Newhall, C G; Fruchter, J S

    1986-03-01

    Volcanoes erupt magma (molten rock containing variable amounts of solid crystals, dissolved volatiles, and gas bubbles) along with pulverized pre-existing rock (ripped from the walls of the vent and conduit). The resulting volcanic rocks vary in their physical and chemical characteristics, e.g., degree of fragmentation, sizes and shapes of fragments, minerals present, ratio of crystals to glass, and major and trace elements composition. Variability in the properties of magma, and in the relative roles of magmatic volatiles and groundwater in driving an eruption, determine to a great extent the type of an eruption; variability in the type of an eruption in turn influences the physical characteristics and distribution of the eruption products. The principal volcanic hazards are: ash and larger fragments that rain down from an explosion cloud (airfall tephra and ballistic fragments); flows of hot ash, blocks, and gases down the slopes of a volcano (pyroclastic flows); "mudflows" (debris flows); lava flows; and concentrations of volcanic gases in topographic depressions. Progress in volcanology is bringing improved long- and short-range forecasts of volcanic activity, and thus more options for mitigation of hazards. Collaboration between health professionals and volcanologists helps to mitigate health hazards of volcanic activity.

  16. Thermal damping and retardation in karst conduits

    Directory of Open Access Journals (Sweden)

    A. J. Luhmann

    2014-08-01

    Full Text Available Water temperature is a non-conservative tracer in the environment. Variations in recharge temperature are damped and retarded as water moves through an aquifer due to heat exchange between water and rock. However, within karst aquifers, seasonal and short-term fluctuations in recharge temperature are often transmitted over long distances before they are fully damped. Using analytical solutions and numerical simulations, we develop relationships that describe the effect of flow path properties, flow-through time, recharge characteristics, and water and rock physical properties on the damping and retardation of thermal peaks/troughs in karst conduits. Using these relationships, one can estimate the thermal retardation and damping that would occur under given conditions with a given conduit geometry. Ultimately, these relationships can be used with thermal damping and retardation field data to estimate parameters such as conduit diameter. We also examine sets of numerical experiments where we relax some of the assumptions used to develop these relationships, testing the effects of variable diameter, variable velocity, open channels, and recharge shape on thermal damping and retardation to provide some constraints on uncertainty. Finally, we discuss a tracer experiment that provides field confirmation of our relationships. High temporal resolution water temperature data are required to obtain sufficient constraints on the magnitude and timing of thermal peaks and troughs in order to take full advantage of water temperature as a tracer.

  17. Assessment of conduit artery vasomotion using photoplethysmography

    Science.gov (United States)

    Kanders, Karlis; Grabovskis, Andris; Marcinkevics, Zbignevs; Aivars, Juris Imants

    2013-11-01

    Vasomotion is a spontaneous oscillation of vascular tone. The phenomenon has been observed in small arterioles and capillaries as well as in the large conduit arteries. The layer of smooth muscle cells that surrounds a blood vessel can spontaneously and periodically change its tension and thereby the arterial wall stiffness also changes. As the understanding of the phenomenon is still rather obscure, researchers would benefit from a low-cost and reliable investigation technique such as photoplethysmography (PPG). PPG is an optical blood pulsation measurement technique that can offer substantial information about the arterial stiffness. The aims of this pilot study were to evaluate the usefulness of the PPG technique in the research of vasomotion and to investigate vasomotion in the relatively large conduit arteries. Continuous 15 minute long measurements of posterior tibial artery wall stiffness were taken. Artery diameter, electrocardiogram, blood pressure and respiration were also simultaneously registered. Fast Fourier Transform power spectra were calculated to identify unique stiffness oscillations that did not correspond to fluctuations in the systemic parameters and thus would indicate vasomotion. We concluded that photoplethysmography is a convenient method for the research of the vasomotion in large arteries. Local stiffness parameter b/a is more accurate to use and easier to measure than the pulse wave velocity which describes stiffness of a segment of an artery. Conduit arteries might exhibit a low amplitude high frequency vasomotion ( 9 to 27 cycles per minute). Low frequency vasomotion is problematic to distinguish from the passive oscillations imposed by the arterial pressure.

  18. Volcanic Catastrophes

    Science.gov (United States)

    Eichelberger, J. C.

    2003-12-01

    The big news from 20th century geophysics may not be plate tectonics but rather the surprise return of catastrophism, following its apparent 19th century defeat to uniformitarianism. Divine miracles and plagues had yielded to the logic of integrating observations of everyday change over time. Yet the brilliant interpretation of the Cretaceous-Tertiary Boundary iridium anomaly introduced an empirically based catastrophism. Undoubtedly, decades of contemplating our own nuclear self-destruction played a role in this. Concepts of nuclear winter, volcanic winter, and meteor impact winter are closely allied. And once the veil of threat of all-out nuclear exchange began to lift, we could begin to imagine slower routes to destruction as "global change". As a way to end our world, fire is a good one. Three-dimensional magma chambers do not have as severe a magnitude limitation as essentially two-dimensional faults. Thus, while we have experienced earthquakes that are as big as they get, we have not experienced volcanic eruptions nearly as great as those preserved in the geologic record. The range extends to events almost three orders of magnitude greater than any eruptions of the 20th century. Such a calamity now would at the very least bring society to a temporary halt globally, and cause death and destruction on a continental scale. At maximum, there is the possibility of hindering photosynthesis and threatening life more generally. It has even been speculated that the relative genetic homogeneity of humankind derives from an evolutionary "bottleneck" from near-extinction in a volcanic cataclysm. This is somewhat more palatable to contemplate than a return to a form of Original Sin, in which we arrived at homogeneity by a sort of "ethnic cleansing". Lacking a written record of truly great eruptions, our sense of human impact must necessarily be aided by archeological and anthropological investigations. For example, there is much to be learned about the influence of

  19. Exploring Hawaiian Volcanism

    Science.gov (United States)

    Poland, Michael P.; Okubo, Paul G.; Hon, Ken

    2013-02-01

    In 1912 the Hawaiian Volcano Observatory (HVO) was established by Massachusetts Institute of Technology professor Thomas A. Jaggar Jr. on the island of Hawaii. Driven by the devastation he observed while investigating the volcanic disasters of 1902 at Montagne Pelée in the Caribbean, Jaggar conducted a worldwide search and decided that Hawai`i provided an excellent natural laboratory for systematic study of earthquake and volcano processes toward better understanding of seismic and volcanic hazards. In the 100 years since HVO's founding, surveillance and investigation of Hawaiian volcanoes have spurred advances in volcano and seismic monitoring techniques, extended scientists' understanding of eruptive activity and processes, and contributed to development of global theories about hot spots and mantle plumes.

  20. Exploring Hawaiian volcanism

    Science.gov (United States)

    Poland, Michael P.; Okubo, Paul G.; Hon, Ken

    2013-01-01

    In 1912 the Hawaiian Volcano Observatory (HVO) was established by Massachusetts Institute of Technology professor Thomas A. Jaggar Jr. on the island of Hawaii. Driven by the devastation he observed while investigating the volcanic disasters of 1902 at Montagne Pelée in the Caribbean, Jaggar conducted a worldwide search and decided that Hawai‘i provided an excellent natural laboratory for systematic study of earthquake and volcano processes toward better understanding of seismic and volcanic hazards. In the 100 years since HVO’s founding, surveillance and investigation of Hawaiian volcanoes have spurred advances in volcano and seismic monitoring techniques, extended scientists’ understanding of eruptive activity and processes, and contributed to development of global theories about hot spots and mantle plumes.

  1. Liver Transplantation Utilizing Mixed Biologic and Synthetic Arterial Conduits

    Directory of Open Access Journals (Sweden)

    Marcio F. Chedid

    2016-01-01

    Full Text Available Arterial conduits are necessary in nearly 5% of all liver transplants and are usually constructed utilizing segments of donor iliac artery. However, available segments of donor iliac artery may not be lengthy enough or may not possess enough quality to enable its inclusion in the conduit. Although there are few reports of arterial conduits constructed solely utilizing prosthetic material, no previous reports of conduits composed of a segment of donor iliac artery and prosthetic material (mixed biologic and synthetic arterial conduits were found in the medial literature to date. Two cases reporting successful outcomes after creation of mixed biologic and prosthetic arterial conduits are outlined in this report. Reason for creation of conduits was complete intimal dissection of the recipient’s hepatic artery in both cases. In both cases, available segments of donor iliac artery were not lengthy enough to bridge infrarenal aorta to porta hepatis. Both patients have patent conduits and normally functioning liver allografts, respectively, at 4 and 31 months after transplant. Mixed biologic and synthetic arterial conduits constitute a viable technical option and may offer potential advantages over fully prosthetic arterial conduits.

  2. Noise-induced variability of volcanic extrusions

    Science.gov (United States)

    Alexandrov, D. V.; Bashkirtseva, I. A.; Ryashko, L. B.

    2016-11-01

    Motivated by important physical applications, we study a non-linear dynamics of volcanic extrusions on the basis of a simple pressure-mass flow model. We demonstrate that the deterministic phase portrait represents either the bulbous-type curves or closed paths stretched to their left depending on the initial conditions. The period of phase trajectories therewith increases when the pressure drop between the conduit top and bottom compensates the lava column pressure in it. Stochastic forcing changes the system dynamics drastically. We show that a repetitive scenario of volcanic behaviour with intermittency of stochastic oscillations of different extrusion amplitudes and frequencies appears in the presence of noises. As this takes place, the mean values of interspike intervals characterizing the system periodicity have a tendency to grow with increasing the noise intensity. The probability distribution functions confirming this dynamic behaviour are constructed.

  3. A 6-year experience with radial artery conduit for myocardial revascularization

    Directory of Open Access Journals (Sweden)

    A Sadeghpour-Tabaee

    2007-07-01

    Full Text Available Background: Excellent long-term patencies of arterial grafts are considered, superior to those of vein grafts. In this study, we present our 6 years experience in using radial artery as a conduit for myocardial revascularization. The aim of the present study was to assess the safety and early and mid term results of using radial artery in coronary artery bypass graft. Methods: The radial artery used as a conduit in 308 cases was evaluated during past 6 years, and the results obtained were processed and analyzed. Results: The operative morbidity comprised re-operation for bleeding in 3.2%, MI in 5%, with paresthesis and stitch abscess of the hand in 10% in and 3.5% respectively. Hospital mortality included 2 patients, one case being directly due to complication of harvesting radial artery.Conclusion: The results of present study were satisfactory with acceptable morbidity and mortality and favored the application of this conduit to CABG patients.

  4. Seismic Tremors and Magma Wagging During Explosive Volcanism

    Science.gov (United States)

    Jellinek, M.; Bercovici, D.

    2010-12-01

    Volcanic tremor is a ubiquitous feature of explosive eruptions. This ground oscillation persists for minutes to weeks and is characterized by a remarkably narrow band of frequencies (i.e., ~0.5 - 7 Hz). Prior to major eruptions, tremor can occur in concert with ground deformation probably related to a buildup of magmatic gas. Volcanic tremor is, thus, of particular value for eruption forecasting. Most models for volcanic tremor rely on specific properties of the geometry, structure and constitution of volcanic conduits as well as the gas content of the erupting magma. Because neither the initial structure nor the evolution of the magma-conduit system will be the same from one volcano to the next, it is surprising that tremor characteristics are so consistent among different volcanoes. Indeed, this universality of tremor properties remains a major enigma. Here we employ the contemporary view that silicic magma rises in the conduit as a columnar plug surrounded by a highly vesicular annulus of sheared bubbles. We demonstrate that, for most geologically relevant conditions, the magma column will oscillate or "wag" against the restoring "gas-spring" force of the annulus at observed tremor frequencies. In contrast to previous models, the magma wagging oscillation is relatively insensitive to the conduit structure and geometry, thereby predicting the narrow band of tremor frequencies observed around the world. Moreover, the model predicts that as an eruption proceeds there will be an upward drift in both the maximum frequency and the total signal frequency bandwidth, the nature of which depends on the explosivity of the eruption, as observed.

  5. Optimization of Design of Steam Turbine Exhaust Conduits

    Directory of Open Access Journals (Sweden)

    A. S. Goldin

    2014-01-01

    Full Text Available Improving effectiveness turbine was and remains a key issue for today. In order to improve the efficiency of the turbine is necessary to reduce losses in the steam turbine exhaust conduit.This paper presents the design optimization exhaust conduit steam turbine K-27-2.9 produced by JSC «KTW» at the design stage. The aims of optimizing the design were: decreasing hydraulic resistance of the conduit, reduction of non-uniformity of the flow at the outlet of the conduit, equalizing steam flow ahead of the condenser tube bundle.The conduit models were made and flows in it were simulated in environment of the Solid Works and its application COSMOS Flo Works.As the initial conduit model was selected exhaust conduit of turbine PT-25/34-3.4 produced by JSC «KTW». Was obtained by the calculated velocity field at the outlet of the conduit. The analysis of the calculation results revealed the necessity of changes to the initial design of the conduit. The changes were accompanied by calculating currents flow in the conduit, and assessed the impact of design changes on the nature of the course. Further transformation of the construction of the conduit was held on the results of these calculations. Construction changes are not touched by the outer geometry of the conduit, and were introduced to meet technological.According to calculation results, conclusions were drawn and selected three versions of the conduit.Given are the research results for the initial conduit model and modified design versions. In order to evaluate the flow degree of irregularity the momentum factor (Bussinesku factor for outlet crosssection of the selected conduit design version. Analysis of the research results made it possible to determine optimum design of the exhaust conduit.Introducing the suggested alterations in the conduit design will result in improvement of heat exchange in the condenser, an increase in reliability of the tube bundle operation, a decrease in noise and

  6. Alkylation of Chitosan as Nerve Conduit Biomaterial

    Institute of Scientific and Technical Information of China (English)

    邓劲光; 公衍道; 程明愚; 赵南明; 张秀芳

    2002-01-01

    Chitosan under physiological conditions is a degradable and biocompatible biomaterial with a wide variety of useful physicochemical properties. However, as a nerve conduit biomaterial, its solubility was very low, so chitosan was modified chemically to enhance its solubility. The free amino groups of long molecular chains in chitosan are responsible for its solubility, and the solubility could be adjusted by controlling the free amidogen capacity with N-alkylation. The results show that the solubility of N-alkylation chitosan is increased to 10%, which is an increase of 500%.

  7. Enhanced noradrenergic axon regeneration into schwann cell-filled PVDF-TrFE conduits after complete spinal cord transection.

    Science.gov (United States)

    Lee, Yee-Shuan; Wu, Siliang; Arinzeh, Treena Livingston; Bunge, Mary Bartlett

    2017-02-01

    Schwann cell (SC) transplantation has been utilized for spinal cord repair and demonstrated to be a promising therapeutic strategy. In this study, we investigated the feasibility of combining SC transplantation with novel conduits to bridge the completely transected adult rat spinal cord. This is the first and initial study to evaluate the potential of using a fibrous piezoelectric polyvinylidene fluoride trifluoroethylene (PVDF-TrFE) conduit with SCs for spinal cord repair. PVDF-TrFE has been shown to enhance neurite growth in vitro and peripheral nerve repair in vivo. In this study, SCs adhered and proliferated when seeded onto PVDF-TrFE scaffolds in vitro. SCs and PVDF-TrFE conduits, consisting of random or aligned fibrous inner walls, were transplanted into transected rat spinal cords for 3 weeks to examine early repair. Glial fibrillary acidic protein (GFAP)(+) astrocyte processes and GFP (green fluorescent protein)-SCs were interdigitated at both rostral and caudal spinal cord/SC transplant interfaces in both types of conduits, indicative of permissivity to axon growth. More noradrenergic/DβH(+) (dopamine-beta-hydroxylase) brainstem axons regenerated across the transplant when greater numbers of GFAP(+) astrocyte processes were present. Aligned conduits promoted extension of DβH(+) axons and GFAP(+) processes farther into the transplant than random conduits. Sensory CGRP(+) (calcitonin gene-related peptide) axons were present at the caudal interface. Blood vessels formed throughout the transplant in both conduits. This study demonstrates that PVDF-TrFE conduits harboring SCs are promising for spinal cord repair and deserve further investigation. Biotechnol. Bioeng. 2017;114: 444-456. © 2016 Wiley Periodicals, Inc.

  8. Effects of steam-heating processes on a stratified volcanic aquifer: Stable isotopes and dissolved gases in thermal waters of Vulcano Island (Aeolian archipelago)

    Science.gov (United States)

    Federico, C.; Capasso, G.; Paonita, A.; Favara, R.

    2010-05-01

    We report on a comprehensive study of major-ion chemistry, dissolved gases, and stable isotopes measured in water wells at Vulcano Island since 1988. The work focuses on a quantitative model describing steam condensation and boiling phenomena in shallow water bodies. The model is based on the differences in partition coefficients between liquid water and vapor characterizing oxygen and hydrogen isotopes, as well as volcanic gases (CO 2, S species, and HCl). Based on both physical conditions of aquifers identified during drilling campaigns and the composition of the volcanic vapor, mass and enthalpy balances are applied in a multistep process of steam separation and condensation in shallower aquifers. By comparing the model results with measured data, we infer that (i) strong isotope enrichment observed in some shallow thermal waters can result from an increasing mass rate of condensing deep vapor, even in water meteoric in origin; (ii) the high CO 2 content measured in the fumarolic vapor during 1988-1993 affected the δ18O value of the steam-heated water due to CO 2-H 2O isotope exchange; (iii) the high pCO 2 measured in the coldest and peripheral waters are explained by the progressive enrichment of this gas in the vapor phase during multistep boiling; and (iv) the high Cl - and SO 42-contents in the hottest waters can be attributed to the direct condensation (single-step) of volcanic vapor. The model also takes into account both the mass fluxes and the compositions of the involved endmembers (steam and shallow groundwater), which provides important inferences on the modifications observed or expected during periods of increasing mass and heat input from depth.

  9. Delayed complication of pelvic lymphocele: Ileal conduit obstruction

    Directory of Open Access Journals (Sweden)

    Sanket S Bankar

    2015-01-01

    Full Text Available Radical cystectomy is the standard treatment for muscle invasive bladder cancer. Lymphocele is a common sequalae of pelvic lymphadenectomy. We report an unusual presentation of pelvic lymphocele developing after radical cystectomy reconstructed with an ileal conduit where the patient developed obstruction of the ileal conduit loop due to external pressure of the lymphocele. Catheter drainage of the conduit relieved the symptoms and a computerized tomography scan showed a large lymphocele causing acute angulation and resultant obstruction of the ileal conduit. The patient was treated with percutaneous drainage of the lymphocele and remains symptom-free on follow-up at 1 year.

  10. Experimental Observations of Multiscale Dynamics of Viscous Fluid Behavior: Implications in Volcanic Systems

    Science.gov (United States)

    Arciniega-Ceballos, A.; Spina, L.; Scheu, B.; Dingwell, D. B.

    2015-12-01

    We have investigated the dynamics of Newtonian fluids with viscosities (10-1000 Pa s; corresponding to mafic to intermediate silicate melts) during slow decompression, in a Plexiglas shock tube. As an analogue fluid we used silicon oil saturated with Argon gas for 72 hours. Slow decompression, dropping from 10 MPa to ambient pressure, acts as the excitation mechanism, initiating several processes with their own distinct timescales. The evolution of this multi-timescale phenomenon generates complex non-stationary microseismic signals, which have been recorded with 7 high-dynamic piezoelectric sensors located along the conduit. Correlation analysis of these time series with the associated high-speed imaging enables characterization of distinct phases of the dynamics of these viscous fluids and the extraction of the time and the frequency characteristics of the individual processes. We have identified fluid-solid elastic interaction, degassing, fluid mass expansion and flow, bubble nucleation, growth, coalescence and collapse, foam building and vertical wagging. All these processes (in fine and coarse scales) are sequentially coupled in time, occur within specific pressure intervals, and exhibit a localized distribution in space. Their coexistence and interactions constitute the stress field and driving forces that determine the dynamics of the system. Our observations point to the great potential of this experimental approach in the understanding of volcanic processes and volcanic seismicity.

  11. Pore Fluid Evolution Influenced by Volcanic Activities and Related Diagenetic Processes in a Rift Basin: Evidence from the Paleogene Medium-Deep Reservoirs of Huanghekou Sag, Bohai Bay Basin, China

    Directory of Open Access Journals (Sweden)

    Zhongheng Sun

    2017-01-01

    Full Text Available Volcanic activities exert a significant influence on pore fluid property and related diagenetic processes that substantially controlled reservoirs quality. Analysis of Paleogene medium-deep sandstones on the Huanghekou Sag provides insight into relating the diagenetic processes to pore fluid property evolution influenced by volcanic activities. Three distinct types of pore fluids were identified on the basis of an integrated and systematic analysis including core and thin section observation, XRD, SEM, CL, and trace element. Alkaline aqueous medium environment occurred in E2s1+2 where volcanic activities have insignificant influence on pore fluids, evidenced by typical alkaline diagenetic events such as K-feldspar albitization, quartz dissolution, feldspar dissolution, and carbonate cementation. During the deposition of E3d3, influx of terrestrial freshwater and alteration of ferromagnesian-rich pore water result in the formation of mixing aqueous medium environment through volcanic eruption dormancy causing zeolite dissolution, clay mineral transformation, and K-feldspar albitization. Ferromagnesian-rich aqueous medium environment developed resulting from the intensive hydrolysis of the unstable ferromagnesian minerals formed due to intense volcanic activities during E3d1+2 and corresponding predominant diagenetic processes were characterized by the precipitation and dissolution of low-silica zeolites. Therefore, the differential properties of pore fluids caused various diagenetic processes controlling reservoir quality.

  12. Geochemical and Sr Nd Pb isotopic evidence for a combined assimilation and fractional crystallisation process for volcanic rocks from the Huichapan caldera, Hidalgo, Mexico

    Science.gov (United States)

    Verma, Surendra P.

    2001-03-01

    This study reports new geochemical and Sr-Nd-Pb isotopic data for Miocene to Quaternary basaltic to andesitic, dacitic, and rhyolitic volcanic rocks from the Huichapan caldera, located in the central part of the Mexican Volcanic Belt (MVB). The initial Sr and Nd isotopic ratios, except for one rhyolite, range as follows: 87Sr/ 86Sr 0.70357-0.70498 and 143Nd/ 144Nd 0.51265-0.51282. The Sr-Nd-Pb isotopic ratios are generally similar to those for volcanic rocks from other areas of the central and eastern parts of the MVB. The isotopic ratios of one older pre-caldera rhyolite (HP30) from the Huichapan area, particularly its high 87Sr/ 86Sr, are significantly different from rhyolitic rocks from this and other areas of the MVB, but are isotopically similar to some felsic rocks from the neighbouring geological province of Sierra Madre Occidental (SMO), implying an origin as a partial melt of the underlying crust. The evolved andesitic to rhyolitic magmas could have originated from a basaltic magma through a combined assimilation and fractional crystallisation (AFC) process. Different compositions, representing lower crust (LC) and upper crust (UC) as well as a hypothetical crust similar to the source of high 87Sr/ 86Sr rhyolite HP30, were tested as plausible assimilants for the AFC process. The results show that the UC represented by granitic rocks from a nearby Los Humeros area or by Cretaceous limestone (L) rocks outcropping in the northern part of the study area, and the LC represented by granulitic xenoliths from a nearby San Luis Potosı´ (SLP) area are not possible assimilants for Huichapan magmas, whereas a hypothetical crust (HA) similar in isotopic compositions to rhyolite HP30 could be considered a possible assimilant for the AFC process. Chemical composition of assimilant HA, although not well constrained at present, was inferred under the assumption that HP30 type partial melts could be generated from its partial melting. These data were then used to evaluate

  13. A numerical program for steady-state flow of magma-gas mixtures through vertical eruptive conduits

    Science.gov (United States)

    Mastin, Larry G.; Ghiorso, Mark S.

    2000-01-01

    This report presents a model that calculates flow properties (pressure, vesicularity, and some 35 other parameters) as a function of vertical position within a volcanic conduit during a steady-state eruption. The model idealizes the magma-gas mixture as a single homogeneousfluid and calculates gas exsolution under the assumption of equilibrium conditions. These are the same assumptions on which classic conduit models (e.g. Wilson and Head, 1981) have been based. They are most appropriate when applied to eruptions of rapidly ascending magma (basaltic lava-fountain eruptions, and Plinian or sub-Plinian eruptions of intermediate or silicic magmas) that contains abundant nucleation sites (microlites, for example) for bubble growth.

  14. Subdiffusion of volcanic earthquakes

    CERN Document Server

    Abe, Sumiyoshi

    2016-01-01

    A comparative study is performed on volcanic seismicities at Mt.Eyjafjallajokull in Iceland and Mt. Etna in Sicily, Italy, from the viewpoint of science of complex systems, and the discovery of remarkable similarities between them regarding their exotic spatio-temporal properties is reported. In both of the volcanic seismicities as point processes, the jump probability distributions of earthquakes are found to obey the exponential law, whereas the waiting-time distributions follow the power law. In particular, a careful analysis is made about the finite size effects on the waiting-time distributions, and accordingly, the previously reported results for Mt. Etna [S. Abe and N. Suzuki, EPL 110, 59001 (2015)] are reinterpreted. It is shown that spreads of the volcanic earthquakes are subdiffusive at both of the volcanoes. The aging phenomenon is observed in the "event-time-averaged" mean-squared displacements of the hypocenters. A comment is also made on presence/absence of long term memories in the context of t...

  15. Volcanic hazard management in dispersed volcanism areas

    Science.gov (United States)

    Marrero, Jose Manuel; Garcia, Alicia; Ortiz, Ramon

    2014-05-01

    Traditional volcanic hazard methodologies were developed mainly to deal with the big stratovolcanoes. In such type of volcanoes, the hazard map is an important tool for decision-makers not only during a volcanic crisis but also for territorial planning. According to the past and recent eruptions of a volcano, all possible volcanic hazards are modelled and included in the hazard map. Combining the hazard map with the Event Tree the impact area can be zoned and defining the likely eruptive scenarios that will be used during a real volcanic crisis. But in areas of disperse volcanism is very complex to apply the same volcanic hazard methodologies. The event tree do not take into account unknown vents, because the spatial concepts included in it are only related with the distance reached by volcanic hazards. The volcanic hazard simulation is also difficult because the vent scatter modifies the results. The volcanic susceptibility try to solve this problem, calculating the most likely areas to have an eruption, but the differences between low and large values obtained are often very small. In these conditions the traditional hazard map effectiveness could be questioned, making necessary a change in the concept of hazard map. Instead to delimit the potential impact areas, the hazard map should show the expected behaviour of the volcanic activity and how the differences in the landscape and internal geo-structures could condition such behaviour. This approach has been carried out in La Palma (Canary Islands), combining the concept of long-term hazard map with the short-term volcanic scenario to show the expected volcanic activity behaviour. The objective is the decision-makers understand how a volcanic crisis could be and what kind of mitigation measurement and strategy could be used.

  16. Investigating the influence of conduit residues on polyurethane plates

    Directory of Open Access Journals (Sweden)

    Rachel Faverzani Magnago

    Full Text Available Abstract Converting waste into a product similar to the original one or into another useful product is to save energy, protect natural resources, and bring back to the production cycle what was discarded. In that direction, new polyurethane-based composites have been developed by incorporating 5%, 10%, 15%, and 20% PVC conduit discarded by the construction industry. The objective of this study was to investigate the interaction between the phases of waste incorporation and the effect upon the new material properties. The samples were produced by the polycondensation process. Microstructural analysis revealed a reduction in pore size across the polymer matrix. However, there were no changes in thermal insulation, water absorption, compressive strength, and burning rate tests and in the thermogravimetric analysis and differential scanning calorimetry. The results from this study showed that the replacement of raw material by waste did not affect its properties.

  17. Non-equilibrium processes in ash-laden volcanic plumes: new insights from 3D multiphase flow simulations

    Science.gov (United States)

    Esposti Ongaro, Tomaso; Cerminara, Matteo

    2016-10-01

    In the framework of the IAVCEI (International Association of Volcanology and Chemistry of the Earth Interior) initiative on volcanic plume models intercomparison, we discuss three-dimensional numerical simulations performed with the multiphase flow model PDAC (Pyroclastic Dispersal Analysis Code). The model describes the dynamics of volcanic and atmospheric gases (in absence of wind) and two pyroclastic phases by adopting a non-equilibrium Eulerian-Eulerian formulation. Accordingly, gas and particulate phases are treated as interpenetrating fluids, interacting with each other through momentum (drag) and heat exchange. Numerical results describe the time-wise and spatial evolution of weak (mass eruption rate: 1.5 × 106 kg/s) and strong (mass eruption rate: 1.5 × 109 kg/s) plumes. The two tested cases display a remarkably different phenomenology, associated with the different roles of atmospheric stratification, compressibility and mechanism of buoyancy reversal, reflecting in a different structure of the plume, of the turbulent eddies and of the atmospheric circulation. This also brings about different rates of turbulent mixing and atmospheric air entrainment. The adopted multiphase flow model allows to quantify temperature and velocity differences between the gas and particles, including settling, preferential concentration by turbulence and thermal non-equilibrium, as a function of their Stokes number, i.e., the ratio between their kinetic equilibrium time and the characteristic large-eddy turnover time of the turbulent plume. As a result, the spatial and temporal distribution of coarse ash in the atmosphere significantly differs from that of the fine ash, leading to a modification of the plume shape. Finally, three-dimensional numerical results have been averaged in time and across horizontal slices in order to obtain a one-dimensional picture of the plume in a stationary regime. For the weak plume, the results are consistent with one-dimensional models, at

  18. Monitoring priority substances, other organic contaminants and heavy metals in a volcanic aquifer from different sources and hydrological processes

    Energy Technology Data Exchange (ETDEWEB)

    Estevez, Esmeralda, E-mail: eestevez@proyinves.ulpgc.es [Dpt. Física (GEOVOL), Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas de Gran Canaria, Canary Islands (Spain); Agrifood and Phytopathological Laboratory (Cabildo de Gran Canaria), 35413 Arucas, Canary Islands (Spain); Cabrera, María del Carmen, E-mail: mcarmen.cabrera@ulpgc.es [Dpt. Física (GEOVOL), Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas de Gran Canaria, Canary Islands (Spain); IMDEA Water Institute, Alcalá de Henares, Madrid (Spain); Fernández-Vera, Juan Ramón, E-mail: jrfernandezv@grancanaria.com [Agrifood and Phytopathological Laboratory (Cabildo de Gran Canaria), 35413 Arucas, Canary Islands (Spain); Molina-Díaz, Antonio, E-mail: amolina@ujaen.es [Analytical Chemistry Research Group, Department of Physical and Analytical Chemistry, University of Jaen, 23071 Jaen (Spain); Robles-Molina, José, E-mail: jroblesmol@gmail.com [Analytical Chemistry Research Group, Department of Physical and Analytical Chemistry, University of Jaen, 23071 Jaen (Spain); Palacios-Díaz, María del Pino, E-mail: mp.palaciosdiaz@ulpgc.es [Dpt. de Patología Animal, Producción Animal, Bromatología y Tecnología de los Alimentos (GEOVOL), Universidad de Las Palmas de Gran Canaria, 35413 Arucas, Canary Islands (Spain)

    2016-05-01

    Irrigation with reclaimed water (R) is necessary to guarantee the sustainability of semi-arid areas. Results obtained during a two years monitoring network (2009–2011) in Gran Canaria are presented, including the analysis of chemical parameters, N and S isotopes, priority substances (2008/105/EC, 2013/39/EU), other organic contaminants and heavy metals in groundwater and R used to irrigate a golf course. The aims of this work are to evaluate the contamination in a volcanic aquifer, relate the presence of organic contaminants and heavy metals with the hydrogeochemistry and identify pollution sources in the area. No priority substance exceeded the EU thresholds for surface water, although seventeen were detected in R. The most frequent compounds were hexachlorobenzene, chlorpyrifos ethyl, fluorene, phenanthrene and pyrene. These compounds were detected at low concentration, except chlorpyrifos. Chlorpyrifos ethyl, terbuthylazine, diuron, terbutryn, procymidone, atrazine and propazine exceeded the European threshold concentration for pesticides in groundwater (100 ng L{sup −1}). Therefore, the priority substances chlorpyrifos ethyl and diuron must be included in monitoring studies. The priority pesticides chlorfenvinphos and diazinon were always detected in R but rarely in groundwater. Besides, the existence of contaminants not related to the current R irrigation has been identified. Absence of environmental problems related to heavy metals can be expected. The relationship among contaminant presence, hydrogeochemistry, including the stable isotopic prints of δ{sup 18}O, δ{sup 15}N and δ{sup 34}S and preferential recharge paths has been described. The coastal well shows high values of EC, nitrate, a variable chemistry, and 50% of organic contaminants detected above 100 ng L{sup −1}. The well located in the recharge area presents a stable hydrochemistry, the lowest value of δ{sup 15}N and the lowest contaminants occurrence. The area is an example of a complex

  19. Nanofibrous nerve conduit-enhanced peripheral nerve regeneration.

    Science.gov (United States)

    Jiang, Xu; Mi, Ruifa; Hoke, Ahmet; Chew, Sing Yian

    2014-05-01

    Fibre structures represent a potential class of materials for the formation of synthetic nerve conduits due to their biomimicking architecture. Although the advantages of fibres in enhancing nerve regeneration have been demonstrated, in vivo evaluation of fibre size effect on nerve regeneration remains limited. In this study, we analyzed the effects of fibre diameter of electrospun conduits on peripheral nerve regeneration across a 15-mm critical defect gap in a rat sciatic nerve injury model. By using an electrospinning technique, fibrous conduits comprised of aligned electrospun poly (ε-caprolactone) (PCL) microfibers (981 ± 83 nm, Microfiber) or nanofibers (251 ± 32 nm, Nanofiber) were obtained. At three months post implantation, axons regenerated across the defect gap in all animals that received fibrous conduits. In contrast, complete nerve regeneration was not observed in the control group that received empty, non-porous PCL film conduits (Film). Nanofiber conduits resulted in significantly higher total number of myelinated axons and thicker myelin sheaths compared to Microfiber and Film conduits. Retrograde labeling revealed a significant increase in number of regenerated dorsal root ganglion sensory neurons in the presence of Nanofiber conduits (1.93 ± 0.71 × 10(3) vs. 0.98 ± 0.30 × 10(3) in Microfiber, p regeneration. These results could provide useful insights for future nerve guide designs.

  20. 五大连池老黑山火山弹和喷发柱动力学模拟%Simulation on the Dynamic Process of Volcanic Bombs and Plumes of Laoheishan Volcano in Wudalianchi Area

    Institute of Scientific and Technical Information of China (English)

    李永生; 刘永顺; 张招崇; 聂保锋; 张东阳

    2012-01-01

    The volcanic eruption is a complex fluid dynamic process of gas, liquid and solid mixtures. A correct understanding of this process is the key factor to study the volcanic eruption. Eject and Plumeria softwares can be good simulations for dynamic processes of volcanic bombs and plumes during real volcanic eruption. On the basis of detailed investigation of volcanic bombs, volcanic debris and the published data of Laoheishan volcano in Wudalianchi area, this study evaluated dynamic processes of Laoheishan volcanic bombs and plumes using Eject and Plumeria softwares. The results show that the bombs ejected from Laoheishan volcano can reach a maximum height of 530 m and a maximum horizontal distance of 1,000 m when ejection angle is 45°; the maximum height of its volcanic plume is 4. 7 km, and the plume head radius is 2. 3 km. Through the discussion of the eruption scale and the ratio of volcanic ashes, it can be concluded that Laoheishan volcano is a small mafic eruption, and its effect on the environment is small.%火山喷发是一个气体、液体和固体混合物的复杂的流体动力学过程.正确理解这个过程是研究火山喷发的关键因素.Eject和Plumeria软件可以很好地模拟现实火山喷发过程中火山弹和喷发柱的动力学过程.在详细调查五大连池老黑山地区火山弹、火山碎屑物和整理已有数据的基础上,运用Eject和Plumeria软件对老黑山火山的火山弹和喷发柱进行了动力学模拟.结果表明:老黑山火山喷发的火山弹喷射最大高度为530 m,喷射角度45.时喷射水平距离最远为1000m,喷发柱最大高度为4.7 km,喷发柱半径为2.3 km.通过对其喷发规模和火山灰构成比例的探讨,认为老黑山火山喷发属于镁铁质火山小型喷发,对环境的影响范围有限.

  1. How to quantify conduits in wood?

    Directory of Open Access Journals (Sweden)

    Alexander eScholz

    2013-03-01

    Full Text Available Vessels and tracheids represent the most important xylem cells with respect to long distance water transport in plants. Wood anatomical studies frequently provide several quantitative details of these cells, such as vessel diameter, vessel density, vessel element length, and tracheid length, while important information on the three dimensional structure of the hydraulic network is not considered. This paper aims to provide an overview of various techniques, although there is no standard protocol to quantify conduits due to high anatomical variation and a wide range of techniques available. Despite recent progress in image analysis programs and automated methods for measuring cell dimensions, density, and spatial distribution, various characters remain time-consuming and tedious. Quantification of vessels and tracheids is not only important to better understand functional adaptations of tracheary elements to environment parameters, but will also be essential for linking wood anatomy with other fields such as wood development, xylem physiology, palaeobotany, and dendrochronology.

  2. How to quantify conduits in wood?

    Science.gov (United States)

    Scholz, Alexander; Klepsch, Matthias; Karimi, Zohreh; Jansen, Steven

    2013-01-01

    Vessels and tracheids represent the most important xylem cells with respect to long distance water transport in plants. Wood anatomical studies frequently provide several quantitative details of these cells, such as vessel diameter, vessel density, vessel element length, and tracheid length, while important information on the three dimensional structure of the hydraulic network is not considered. This paper aims to provide an overview of various techniques, although there is no standard protocol to quantify conduits due to high anatomical variation and a wide range of techniques available. Despite recent progress in image analysis programs and automated methods for measuring cell dimensions, density, and spatial distribution, various characters remain time-consuming and tedious. Quantification of vessels and tracheids is not only important to better understand functional adaptations of tracheary elements to environment parameters, but will also be essential for linking wood anatomy with other fields such as wood development, xylem physiology, palaeobotany, and dendrochronology.

  3. Volcanic hazard assessment in monogenetic volcanic fields

    OpenAIRE

    Bartolini, Stefania

    2014-01-01

    [eng] One of the most important tasks of modern volcanology, which represents a significant socio-economic implication, is to conduct hazard assessment in active volcanic systems. These volcanological studies are aimed at hazard that allows to constructing hazard maps and simulating different eruptive scenarios, and are mainly addressed to contribute to territorial planning, definition of emergency plans or managing volcanic crisis. The impact of a natural event, as a volcanic eruption, can s...

  4. Magmatic Conduit Metallogenic System - A New Model for the Origin of Ore-deposits

    Science.gov (United States)

    Su, S.; Tang, Z.; Wu, G.; Deng, J.; Xiao, Q.; Luo, Z.; Cui, Y.

    2013-12-01

    Origin and emplacement processes of ore-deposits connected with intrusions remains poorly understood. Here we propose a new model 'Magmatic Conduit Metallogenic System' to explain the origin of ore-deposits. Magmatic flow (or Melt-fluid flow) bearing metals will finally settle in the conduits at later stage of magma evolved in magma metallogenic system. Magmatic flow (or Melt-fluid flow) bearing metals include many types, such as sulfide melts and iron melts bearing fluids. Conduits will form along the zones of structural weakness, such as fault zone and interface of two different types of rocks. These conduits are usually very complicated in the magmatic system, exemplified by two typical ore-deposits, detailed as follows. The Jinchuan sulfide deposit, located in Gansu Province, China, is the third largest magmatic Cu-Ni Platinum Group Elements (PGE) in the world. There are mainly four orebodies (orebody 58, 24, 1, and 2) from west to east, with Ni/Cu value at 1.24, 1.56, 1.83 and 2.06 respectively; the content of Pt+Pd ranges from 0.4 to 10.3 ppm, with the highest value occurs in the west. This suggests that the direction of the melt flow bearing sulfide is from west to east and the front of the conduit system is in the east part of the deposit. Sulfide segregation in the magmatic chamber or in the conduits might have caused ore content to change in different part of the conduit systems. Another typical example is the Xishimen iron deposit, which is located in the South of Hebei Province, China. It has been considered as a skarn-type iron deposit conventionally. However, many geological evidence suggests that Xishimen iron deposit is a magmatic iron deposit instead. Such evidence includes: 1. The boundaries between iron orebodies and country rocks are obvious, no transitional relationship; 2. Iron ore body injected into the country rocks (including genesis, diorite, and marble); 3. There are some vesicular in the iron ores; 4. Magnetite as an interstitial mineral

  5. A New Equation Solver for Modeling Turbulent Flow in Coupled Matrix-Conduit Flow Models.

    Science.gov (United States)

    Hubinger, Bernhard; Birk, Steffen; Hergarten, Stefan

    2016-07-01

    Karst aquifers represent dual flow systems consisting of a highly conductive conduit system embedded in a less permeable rock matrix. Hybrid models iteratively coupling both flow systems generally consume much time, especially because of the nonlinearity of turbulent conduit flow. To reduce calculation times compared to those of existing approaches, a new iterative equation solver for the conduit system is developed based on an approximated Newton-Raphson expression and a Gauß-Seidel or successive over-relaxation scheme with a single iteration step at the innermost level. It is implemented and tested in the research code CAVE but should be easily adaptable to similar models such as the Conduit Flow Process for MODFLOW-2005. It substantially reduces the computational effort as demonstrated by steady-state benchmark scenarios as well as by transient karst genesis simulations. Water balance errors are found to be acceptable in most of the test cases. However, the performance and accuracy may deteriorate under unfavorable conditions such as sudden, strong changes of the flow field at some stages of the karst genesis simulations.

  6. Fabrication of Off-the-Shelf Multilumen Poly(Ethylene Glycol) Nerve Guidance Conduits Using Stereolithography.

    Science.gov (United States)

    Arcaute, Karina; Mann, Brenda K; Wicker, Ryan B

    2011-01-01

    A manufacturing process for fabricating off-the-shelf multilumen poly(ethylene glycol) (PEG)-based nerve guidance conduits (NGCs) was developed that included the use of stereolithography (SL). A rapid fabrication strategy for complex 3D scaffolds incorporated postprocessing with lyophilization and sterilization to preserve the scaffold, creating an implantable product with improved suturability. SL is easily adaptable to changes in scaffold design, is compatible with various materials and cells, and can be expanded for mass manufacture. The fabricated conduits were characterized using optical and scanning electron microscopy, and measurements of swelling ratio, dimensional swelling factor, resistance to compression, and coefficient of friction were performed. Water absorption curves showed that the conduits after lyophilization and sterilization return easily and rapidly to a swollen state when placed in an aqueous solution, successfully maintaining their original overall structure as required for implantation. Postprocessed conduits at the swollen state were less slippery and therefore easier to handle than those without postprocessing. Suture pullout experiments showed that NGCs fabricated with a higher concentration of PEG were better able to resist suture pullout. NGCs having a multilumen design demonstrated a better resistance to compression than a single-lumen design with an equivalent surface area, as well as a greater force required to collapse the design. Conduits fabricated with a higher PEG concentration were shown to have compressive resistances comparable to those of commercially available NGCs. The use of SL with PEG and the manufacturing process developed here shows promise for improving the current state of the art in peripheral nerve repair strategies.

  7. Application of a venous conduit as a stent for repairing rabbit facial nerve injury

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    BACKGROUND:Recently,many investigators have tried to use natural biomaterials,such as,artery,vein,decalcified bone,etc.,as conduits for nerve repair.However,immunological rejection of conduits made of natural biomaterials limits their application.Therefore,it is essential to identify more suitable types of biomaterials.OBJECTIVE:To observe the characteristics of a bioengineering processing method using venous conduit as a stent for repairing facial nerve injury.DESIGN:A controlled observational experiment.SETTING:Animal Laboratories of the Third Hospital Affiliated to Sun Yat-sen University and the 157 Hospital.MATERIALS:Thirty-three male New Zealand rabbits of pure breed,weighing 1.5 to 2.0 kg,were provided by Medical Experimental Animal Room of Sun Yat-sen University.The protocol was carried out in accordance with animal ethics guidelines for the use and care of animals.Venous conduits and autogenous nerves were transplanted into the left and right cheeks,respectively.Eleven animals were chosen for anatomical observations at 5,10 and 15 weeks after surgery.METHODS:This experiment was carried out in the Animal Laboratories of the Third Hospital Affiliated to Sun Yat-sen University and the 157 Hospital between May and November 2006.After animals were anesthetized,15 mm of retromandibular vein was harvested for preparing a venous conduit.Approximately 3 cm of low buccal branch of facial nerve was exposed.A segment of 1.2 cm nerve was resected from the middle,and a gap of 1.5 cm formed due to bilateral retraction.The prepared venous conduit of 1.5 cm was sutured to the outer membrane of the severed ends of the nerve.Muscle and skin were sutured layer by layer.Using the same above-mentioned method,the low buccal branch of right autogenous facial nerve was resected,and the left facial nerve segment from the same animal was transplanted using end-to-end neurorrhaphy for control.MAIN OUTCOME MEASURES:①Post-operatively,food intake,vibrissae activity and wound healing of

  8. Permeability Reduction in Passively Degassing Seawater-dominated Volcanic-hydrothermal systems: Processes and Perils on Raoul Island, Kermadecs (NZ)

    Science.gov (United States)

    Christenson, B. W.; Reyes, A. G.

    2014-12-01

    The 2006 eruption from Raoul Island occurred apparently in response to local tectonic swarm activity, but without any precursory indication of volcanic unrest within the hydrothermal system on the island. The eruption released some 200 T of SO2, implicating the involvement of a deep magmatic vapor input into the system during/prior to the event. In the absence of any recognized juvenile material in the eruption products, previous explanations for this eruptive event focused on this vapor being a driving force for the eruption. In 2004, at least 80 T/d of CO2 was escaping from the hydrothermal system, but mainly through areas that did not correspond to the 2006 eruption vents. The lack of a pre-eruptive hydrothermal system response related to the seismic event in 2006 can be explained by the presence of a hydrothermal mineralogic seal in the vent area of the volcano. Evidence for the existence of such a seal was found in eruption deposits in the form of massive fracture fillings of aragonite, calcite and anhydrite. Fluid inclusion homogenization temperatures in these phases range from ca. 140 °C to 220 °C which, for pure water indicate boiling point depths of between 40 and 230 m assuming a cold hydrostatic pressure constraint. Elevated pressures behind this seal are consistent with the occurrence of CO2 clathrates in some inclusion fluids, indicating CO2 concentrations approaching 1 molal in the parent fluids. Reactive transport modeling of magmatic volatile inputs into what is effectively a seawater-dominated hydrothermal system provide valuable insights into seal formation. Carbonate mineral phases ultimately come to saturation along this flow path, but we suggest that focused deposition of the observed massive carbonate seal is facilitated by near-surface boiling of these CO2-enriched altered seawaters, leading to large degrees of supersaturation which are required for the formation of aragonite. As the seal grew and permeability declined, pore pressures

  9. Modeling Solute Reactivity in a Phreatic Solution Conduit Penetrating a Karst Aquifer

    Science.gov (United States)

    Field, M.

    2014-12-01

    A two-dimensional model for solute migration, transformation, and sorption in a phreatic solution conduit penetrating a karst aquifer is presented in which the solute is anthropogenic to the natural system. Transformation of a reacting solute in a solution conduit has generally been accepted as likely occurring but actual physical measurements and mathematical analyses of the suspected process are lacking, primarily because of the logistics of sample collection and the complexities associated with solute transport through solution conduits. The model demonstrates how a reacting solute might be converted to a product solute some of which then diffuses to the solution conduit wall where it may become adsorbed. Model effects vary for laminar flow and turbulent flow in the axial direction. Laminar and turbulent diffusion in the radial direction also exhibits marked differences. In addition to single reaction zones simulations considered multiple adjacent and nonadjacent reaction zones, both with varying reaction rates. Reaction zones were found to enhance subsequent reactions due to some overlap resulting from the hydrodynamic dispersion caused by the axial flow. The simulations showed that varying the reaction rate coefficient strongly affects solute reactions, but that varying deposition coefficients had only minimal impacts. Application of the model to a tracer test that used the tracer dye, Rhodamine WT which readily converts to deaminoalkylated Rhodamine WT after release, illustrates how the model may be used to suggest a possible cause for less than 100% tracer mass recovery. In terms of pollutants in a karst aquifer the model suggests a possible explanation for pollutant transformation in a solution conduit.

  10. Biological conduit small gap sleeve bridging method for peripheral nerve injury: regeneration law of nerve fibers in the conduit

    Directory of Open Access Journals (Sweden)

    Pei-xun Zhang

    2015-01-01

    Full Text Available The clinical effects of 2-mm small gap sleeve bridging of the biological conduit to repair peripheral nerve injury are better than in the traditional epineurium suture, so it is possible to replace the epineurium suture in the treatment of peripheral nerve injury. This study sought to identify the regeneration law of nerve fibers in the biological conduit. A nerve regeneration chamber was constructed in models of sciatic nerve injury using 2-mm small gap sleeve bridging of a biodegradable biological conduit. The results showed that the biological conduit had good histocompatibility. Tissue and cell apoptosis in the conduit apparently lessened, and regenerating nerve fibers were common. The degeneration regeneration law of Schwann cells and axons in the conduit was quite different from that in traditional epineurium suture. During the prime period for nerve fiber regeneration (2-8 weeks, the number of Schwann cells and nerve fibers was higher in both proximal and distal ends, and the effects of the small gap sleeve bridging method were better than those of the traditional epineurium suture. The above results provide an objective and reliable theoretical basis for the clinical application of the biological conduit small gap sleeve bridging method to repair peripheral nerve injury.

  11. Biological conduit small gap sleeve bridging method for peripheral nerve injury:regeneration law of nerve ifbers in the conduit

    Institute of Scientific and Technical Information of China (English)

    Pei-xun Zhang; Li-ya A; Yu-hui Kou; Xiao-feng Yin; Feng Xue#; Na Han; Tian-bing Wang; Bao-guo Jiang

    2015-01-01

    The clinical effects of 2-mm small gap sleeve bridging of the biological conduit to repair periph-eral nerve injury are better than in the traditional epineurium suture, so it is possible to replace the epineurium suture in the treatment of peripheral nerve injury. This study sought to identify the regeneration law of nerve fibers in the biological conduit. A nerve regeneration chamber was constructed in models of sciatic nerve injury using 2-mm small gap sleeve bridging of a biodegradable biological conduit. The results showed that the biological conduit had good his-tocompatibility. Tissue and cell apoptosis in the conduit apparently lessened, and regenerating nerve ifbers were common. The degeneration regeneration law of Schwann cells and axons in the conduit was quite different from that in traditional epineurium suture. During the prime period for nerve fiber regeneration (2–8 weeks), the number of Schwann cells and nerve fibers was higher in both proximal and distal ends, and the effects of the small gap sleeve bridging method were better than those of the traditional epineurium suture. The above results provide an objec-tive and reliable theoretical basis for the clinical application of the biological conduit small gap sleeve bridging method to repair peripheral nerve injury.

  12. Geochemical study for volcanic surveillance

    Energy Technology Data Exchange (ETDEWEB)

    Panichi, C.; La Ruffa, G. [Consiglio Nazionale delle Ricerche, International Institute for Geothermal Research Ghezzano, PI (Italy)

    2000-07-01

    For years, geologists have been striving to reconstruct volcanic eruptions from the analysis of pyroclastic deposits and lava flows on the surface of the earth and in the oceans. This effort has produced valuable information on volcanic petrology and magma generation, separation, mixing, crystallisation, and interaction with water in phreatomagmatic and submarine eruptions. The volcanological process are tied to the dynamics of the earth's crust and lithosphere. The mantle, subducted oceanic crust, and continental crust contain different rock types and are sources of different magmas. Magmas consist primarily of completely or partially molten silicates containing volatile materials either dissolved in the melt or as bubbles of gas. The silicate and volatile portions affect the physical properties of magma and, therefore, the nature of a volcanic eruption.

  13. Spotlight on CERN : Le code de conduite

    CERN Multimedia

    CERN Video Productions

    2010-01-01

    Cette année 2010, le démarrage du LHC a été le témoignage de la réussite de la collaboration scientifique au CERN, rapprochant les personnes, hommes et femmes, tous ensemble pour la plus grande des réalisations. Cette collaboration nécessite une ouverture sur la diversité basée sur des valeurs solides. Pour s’assurer que l'Organisation continue sur la voie du succès, un consensus a été atteint sur des valeurs caractérisant le CERN et celles-ci ont été regroupées dans un Code de conduite, décrivant la norme de base du comportement que nous pouvons tous espérer de nous-mêmes et de nos collègues sur notre lieu de travail. Entrevues avec Rolf Heuer, Directeur Général du CERN, Anne-Sylvie Catherin, Chef du Département des Ressources Humaines, et Vincent Vuillemin, Ombuds au CERN.

  14. Controls on volcanism at intraplate basaltic volcanic fields

    Science.gov (United States)

    van den Hove, Jackson C.; Van Otterloo, Jozua; Betts, Peter G.; Ailleres, Laurent; Cas, Ray A. F.

    2017-02-01

    A broad range of controlling mechanisms is described for intraplate basaltic volcanic fields (IBVFs) in the literature. These correspond with those relating to shallow tectonic processes and to deep mantle plumes. Accurate measurement of the physical parameters of intraplate volcanism is fundamental to gain an understanding of the controlling factors that influence the scale and location of a specific IBVF. Detailed volume and geochronology data are required for this; however, these are not available for many IBVFs. In this study the primary controls on magma genesis and transportation are established for the Pliocene-Recent Newer Volcanics Province (NVP) of south-eastern Australia as a case-study for one of such IBVF. The NVP is a large and spatio-temporally complex IBVF that has been described as either being related to a deep mantle plume, or upper mantle and crustal processes. We use innovative high resolution aeromagnetic and 3D modelling analysis, constrained by well-log data, to calculate its dimensions, volume and long-term eruptive flux. Our estimates suggest volcanic deposits cover an area of 23,100 ± 530 km2 and have a preserved dense rock equivalent of erupted volcanics of least 680 km3, and may have been as large as 900 km3. The long-term mean eruptive flux of the NVP is estimated between 0.15 and 0.20 km3/ka, which is relatively high compared with other IBVFs. Our comparison with other IBVFs shows eruptive fluxes vary up to two orders of magnitude within individual fields. Most examples where a range of eruptive flux is available for an IBVF show a correlation between eruptive flux and the rate of local tectonic processes, suggesting tectonic control. Limited age dating of the NVP has been used to suggest there were pulses in its eruptive flux, which are not resolvable using current data. These changes in eruptive flux are not directly relatable to the rate of any interpreted tectonic driver such as edge-driven convection. However, the NVP and other

  15. Explosive volcanism and associated pressures - Implications for models of endogenically shocked quartz

    Science.gov (United States)

    De Silva, S. L.; Wolff, J. A.; Sharpton, V. L.

    1990-01-01

    The nature of explosive volcanic phenomena and associated pressures, both from field and theoretical perspectives, is discussed. An endogenic origin for shocked quartz at the K/T boundary requires impulsive pressures greater than 60 kbars to be generated during explosive volcanism. Explosive volcanic eruptions which are events of sustained decompression may be initiated by impulsive explosions while the magnitudes of the overpressures are small. These maximum overpressures can be controlled mainly by the tensile strength of the rock surrounding the magma chamber-conduit system. Thus maximum overpressures in the volcanic environment are limited to less than 500 bars which are orders of magnitude less than those required for shock quartz (greater than 60 kbars). This observation is found to be consistent with the complete lack of field or petrographic evidence in support of shock metamorphism associated with volcanic eruptions and their products.

  16. Nerve guidance conduit with a hybrid structure of a PLGA microfibrous bundle wrapped in a micro/nanostructured membrane

    Science.gov (United States)

    Peng, Shih-Wen; Li, Ching-Wen; Chiu, Ing-Ming; Wang, Gou-Jen

    2017-01-01

    Nerve repair in tissue engineering involves the precise construction of a scaffold to guide nerve cell regeneration in the desired direction. However, improvements are needed to facilitate the cell migration/growth rate of nerves in the center of a nerve conduit. In this paper, we propose a nerve guidance conduit with a hybrid structure comprising a microfibrous poly(lactic-co-glycolic acid) (PLGA) bundle wrapped in a micro/nanostructured PLGA membrane. We applied sequential fabrication processes, including photolithography, nano-electroforming, and polydimethylsiloxane casting to manufacture master molds for the repeated production of the PLGA subelements. After demolding it from the master molds, we rolled the microfibrous membrane into a bundle and then wrapped it in the micro/nanostructured membrane to form a nerve-guiding conduit. We used KT98/F1B-GFP cells to estimate the migration rate and guidance ability of the fabricated nerve conduit and found that both elements increased the migration rate 1.6-fold compared with a flat PLGA membrane. We also found that 90% of the cells in the hybrid nano/microstructured membrane grew in the direction of the designed patterns. After 3 days of culturing, the interior of the nerve conduit was filled with cells, and the microfiber bundle was also surrounded by cells. Our conduit cell culture results also demonstrate that the proposed micro/nanohybrid and microfibrous structures can retain their shapes. The proposed hybrid-structured conduit demonstrates a high capability for guiding nerve cells and promoting cell migration, and, as such, is feasible for use in clinical applications. PMID:28138239

  17. Records of Precambrian Early Palaeozoic volcanic and sedimentary processes in the Central European Variscides: A review of SHRIMP zircon data from the Kaczawa succession (Sudetes, SW Poland)

    Science.gov (United States)

    Kryza, Ryszard; Zalasiewicz, Jan

    2008-12-01

    The early, pre-orogenic stages of evolution in the Variscan belt, i.e. rifting processes, opening of sedimentary basins and associated igneous activities, are often obscure because many successions have yielded little or no biostratigraphic data, have a strong metamorphic overprint and are tectonically deformed and dislocated. The increasing application of SHRIMP zircon dating has provided useful constraints on magmatic and metamorphic processes, helped locate probable source areas for detritus within sedimentary successions and facilitated large-scale palaeogeographic correlations. This methodology has recently thrown considerable light on the age and relationships of the previously poorly constrained rock units of the Kaczawa Complex in the Polish West Sudetes. Thus, recent SHRIMP studies in the Kaczawa Mountains have yielded Early Ordovician ages of the initial rift type bimodal volcanic suites at the bottom part of the Kaczawa Succession: c. 503 Ma for metarhyodacites of crustal derivation, and c. 485 Ma for alkaline metatrachytes of mantle signature. These dates provide a firm temporal constraint on the initial rift magmatism interpreted as related to the continental break-up of the northern peripheries of Gondwana. New SHRIMP data from metavolcaniclastic and metasedimentary rocks of the Kaczawa Complex have yielded results that have provided significantly changed interpretations on their age and relationships. For instance, a siliciclastic sequence interpreted as belonging to the lower part of the Kaczawa Complex (the Gackowa Sandstones) and seemingly sourced (using an array of geochemical and mineralogical evidence) from nearby early Ordovician volcanic rocks has, surprisingly, yielded zircon ages not younger than Precambrian and thus this unit has tentatively been reinterpreted as a possible correlative of the Neoproterozoic Lusatian Graywackes. Felsic metavolcaniclastic rocks embedded in the carbonate succession of the Wojcieszów Limestone have yielded

  18. 26 CFR 1.7701(l)-1 - Conduit financing arrangements.

    Science.gov (United States)

    2010-04-01

    ... determines that such recharacterization is appropriate to prevent avoidance of any tax imposed by title 26 of...) INCOME TAX (CONTINUED) INCOME TAXES General Actuarial Valuations § 1.7701(l)-1 Conduit financing...

  19. Guided regeneration with resorbable conduits in experimental peripheral nerve injuries

    OpenAIRE

    Nicoli Aldini, N.; Fini, M; Rocca, M; Giavaresi, G.; Giardino, R.

    2000-01-01

    Guided tissue regeneration is a new approach in the reconstructive surgery of peripheral nerves. Artificial conduits can be constructed from biodegradable polymers. Lactic/caproic acid copolymers and polyphospazenes are biocompatible materials with a slow resorption rate. Conduits made from either poly-[l-lactide-co-6-caprolatone] or poly-[bis-(ethylalanate)-phosphazene] were assessed for use as guides for nerve regeneration in experimental animals. Under general anesthesia and by using a mic...

  20. Characterizing Volcanic Processes using Near-bottom, High Resolution Magnetic Mapping of the Caldera and Inner Crater of the Kick'em Jenny Submarine Volcano

    Science.gov (United States)

    Ruchala, T. L.; Chen, M.; Tominaga, M.; Carey, S.

    2016-12-01

    Kick'em Jenny (KEJ) is an active submarine volcano located in the Lesser Antilles subduction zone, 7.5 km north of the Caribbean island Grenada. KEJ, known as one of the most explosive volcanoes in Caribbean, erupted 12 times since 1939 with recent eruptions in 2001 and possibly in 2015. Multiple generations of submarine landslides and canyons have been observed in which some of them can be attributed to past eruptions. The structure of KEJ can be characterized as a 1300 m high conical profile with its summit crater located around 180 m in depth. Active hydrothermal venting and dominantly CO2 composition gas seepage take place inside this 250m diameter crater, with the most activity occurring primarily within a small ( 70 x 110 m) depression zone (inner crater). In order to characterize the subsurface structure and decipher the processes of this volcanic system, the Nautilus NA054 expedition in 2014 deployed the underwater Remotely Operated Vehicle (ROV) Hercules to conduct near-bottom geological observations and magnetometry surveys transecting KEJ's caldera. Raw magnetic data was corrected for vehicle induced magnetic noise, then merged with ROV to ship navigation at 1 HZ. To extract crustal magnetic signatures, the reduced magnetic data was further corrected for external variations such as the International Geomagnetic Reference Field and diurnal variations using data from the nearby San Juan Observatory. We produced a preliminary magnetic anomaly map of KEJ's caldera for subsequent inversion and forward modeling to delineate in situ magnetic source distribution in understanding volcanic processes. We integrated the magnetic characterization of the KEJ craters with shipboard multibeam, ROV visual descriptions, and photomosaics. Initial observations show the distribution of short wavelength scale highly magnetized source centered at the north western part of the inner crater. Although locations of gas seeps are ubiquitous over the inner crater area along ROV

  1. Volcanic Eruptions and Climate

    Science.gov (United States)

    LeGrande, Allegra N.; Anchukaitis, Kevin J.

    2015-01-01

    Volcanic eruptions represent some of the most climatically important and societally disruptive short-term events in human history. Large eruptions inject ash, dust, sulfurous gases (e.g. SO2, H2S), halogens (e.g. Hcl and Hbr), and water vapor into the Earth's atmosphere. Sulfurous emissions principally interact with the climate by converting into sulfate aerosols that reduce incoming solar radiation, warming the stratosphere and altering ozone creation, reducing global mean surface temperature, and suppressing the hydrological cycle. In this issue, we focus on the history, processes, and consequences of these large eruptions that inject enough material into the stratosphere to significantly affect the climate system. In terms of the changes wrought on the energy balance of the Earth System, these transient events can temporarily have a radiative forcing magnitude larger than the range of solar, greenhouse gas, and land use variability over the last millennium. In simulations as well as modern and paleoclimate observations, volcanic eruptions cause large inter-annual to decadal-scale changes in climate. Active debates persist concerning their role in longer-term (multi-decadal to centennial) modification of the Earth System, however.

  2. From rock to magma and back again: The evolution of temperature and deformation mechanism in conduit margin zones

    Science.gov (United States)

    Heap, Michael J.; Violay, Marie; Wadsworth, Fabian B.; Vasseur, Jérémie

    2017-04-01

    Explosive silicic volcanism is driven by gas overpressure in systems that are inefficient at outgassing. The zone at the margin of a volcanic conduit-thought to play an important role in the outgassing of magma and therefore pore pressure changes and explosivity-is the boundary through which heat is exchanged from the hot magma to the colder country rock. Using a simple heat transfer model, we first show that the isotherm for the glass transition temperature (whereat the glass within the groundmass transitions from a glass to an undercooled liquid) moves into the country rock when the magma within the conduit can stay hot, or into the conduit when the magma is quasi-stagnant and cools (on the centimetric scale over days to months). We then explore the influence of a migrating viscous boundary on compactive deformation micromechanisms in the conduit margin zone using high-pressure (effective pressure of 40 MPa), high-temperature (up to 800 °C) triaxial deformation experiments on porous andesite. Our experiments show that the micromechanism facilitating compaction in andesite is localised cataclastic pore collapse at all temperatures below the glass transition of the amorphous groundmass glass Tg (i.e., rock). In this regime, porosity is only reduced within the bands of crushed pores; the porosity outside the bands remains unchanged. Further, the strength of andesite is a positive function of temperature below the threshold Tg due to thermal expansion driven microcrack closure. The micromechanism driving compaction above Tg (i.e., magma) is the distributed viscous flow of the melt phase. In this regime, porosity loss is distributed and is accommodated by the widespread flattening and closure of pores. We find that viscous flow is much more efficient at reducing porosity than cataclastic pore collapse, and that it requires stresses much lower than those required to form bands of crushed pores. Our study therefore highlights that temperature excursions can result in a

  3. Hydrogen isotope investigation of amphibole and biotite phenocrysts in silicic magmas erupted at Lassen Volcanic Center, California

    Science.gov (United States)

    Underwood, S.J.; Feeley, T.C.; Clynne, M.A.

    2012-01-01

    Hydrogen isotope ratio, water content and Fe3 +/Fe2 + in coexisting amphibole and biotite phenocrysts in volcanic rocks can provide insight into shallow pre- and syn-eruptive magmatic processes such as vesiculation, and lava drainback with mixing into less devolatilized magma that erupts later in a volcanic sequence. We studied four ~ 35 ka and younger eruption sequences (i.e. Kings Creek, Lassen Peak, Chaos Crags, and 1915) at the Lassen Volcanic Center (LVC), California, where intrusion of crystal-rich silicic magma mushes by mafic magmas is inferred from the varying abundances of mafic magmatic inclusions (MMIs) in the silicic volcanic rocks. Types and relative proportions of reacted and unreacted hydrous phenocryst populations are evaluated with accompanying chemical and H isotope changes. Biotite phenocrysts were more susceptible to rehydration in older vesicular glassy volcanic rocks than coexisting amphibole phenocrysts. Biotite and magnesiohornblende phenocrysts toward the core of the Lassen Peak dome are extensively dehydroxylated and reacted from prolonged exposure to high temperature, low pressure, and higher fO2 conditions from post-emplacement cooling. In silicic volcanic rocks not affected by alteration, biotite phenocrysts are often relatively more dehydroxylated than are magnesiohornblende phenocrysts of similar size; this is likely due to the ca 10 times larger overall bulk H diffusion coefficient in biotite. A simplified model of dehydrogenation in hydrous phenocrysts above reaction closure temperature suggests that eruption and quench of magma ascended to the surface in a few hours is too short a time for substantial H loss from amphibole. In contrast, slowly ascended magma can have extremely dehydrogenated and possibly dehydrated biotite, relatively less dehydrogenated magnesiohornblende and reaction rims on both phases. Eruptive products containing the highest proportions of mottled dehydrogenated crystals could indicate that within a few days

  4. Recovery process of shear wave velocities of volcanic soil in central Mashiki Town after the 2016 Kumamoto earthquake revealed by intermittent measurements of microtremor

    Science.gov (United States)

    Hata, Yoshiya; Yoshimi, Masayuki; Goto, Hiroyuki; Hosoya, Takashi; Morikawa, Hitoshi; Kagawa, Takao

    2017-05-01

    An earthquake of JMA magnitude 6.5 (foreshock) hit Kumamoto Prefecture, Japan, at 21:26 JST on April 14, 2016. Subsequently, an earthquake of JMA magnitude 7.3 (main shock) hit Kumamoto and Oita Prefectures at 1:25 JST on April 16, 2016. The two epicenters were located adjacent to central Mashiki Town, and both events caused significantly strong motions. The heavy damage including collapse of residential houses was concentrated in "Sandwich Area" between Prefectural Route 28 and Akitsu River. During the main shock, we have successfully observed strong motions at TMP03 in Sandwich Area. Simultaneously with installation of the seismograph at TMP03 on April 15, 2016, between the foreshock and the main shock, a microtremor measurement was taken. After the main shock, intermittent measurements of microtremor at TMP03 were also taken within December 6, 2016. As the result, recovery process of shear wave velocities of volcanic soil at TMP03 before/after the main shock was revealed by time history of peak frequencies of the microtremor H/V spectra. Using results of original PS logging tests at proximity site of TMP03 on July 28, 2016, the applicability for the shear wave velocities to TMP03 was then confirmed based on similarity between the theoretical and monitored H/V spectra.

  5. Engineering a robotic approach to mapping exposed volcanic fissures

    Science.gov (United States)

    Parcheta, C. E.; Parness, A.; Mitchell, K. L.

    2014-12-01

    Field geology provides a framework for advanced computer models and theoretical calculations of volcanic systems. Some field terrains, though, are poorly preserved or accessible, making documentation, quantification, and investigation impossible. Over 200 volcanologists at the 2012 Kona Chapman Conference on volcanology agreed that and important step forward in the field over the next 100 years should address the realistic size and shape of volcanic conduits. The 1969 Mauna Ulu eruption of Kīlauea provides a unique opportunity to document volcanic fissure conduits, thus, we have an ideal location to begin addressing this topic and provide data on these geometries. Exposed fissures can be mapped with robotics using machine vision. In order to test the hypothesis that fissures have irregularities with depth that will influence their fluid dynamical behavior, we must first map the fissure vents and shallow conduit to deci- or centimeter scale. We have designed, constructed, and field-tested the first version of a robotic device that will image an exposed volcanic fissure in three dimensions. The design phase included three steps: 1) create the payload harness and protective shell to prevent damage to the electronics and robot, 2) construct a circuit board to have the electronics communicate with a surface-based computer, and 3) prototype wheel shapes that can handle a variety of volcanic rock textures. The robot's mechanical parts were built using 3d printing, milling, casting and laser cutting techniques, and the electronics were assembled from off the shelf components. The testing phase took place at Mauna Ulu, Kīlauea, Hawai'i, from May 5 - 9, 2014. Many valuable design lessons were learned during the week, and the first ever 3D map from inside a volcanic fissure were successfully collected. Three vents had between 25% and 95% of their internal surfaces imaged. A fourth location, a non-eruptive crack (possibly a fault line) had two transects imaging the textures

  6. Lorentz force effect on mixed convection micropolar flow in a vertical conduit

    Science.gov (United States)

    Abdel-wahed, Mohamed S.

    2017-05-01

    The present work provides a simulation of control and filtration process of hydromagnetic blood flow with Hall current under the effect of heat source or sink through a vertical conduit (pipe). This work meets other engineering applications, such as nuclear reactors cooled during emergency shutdown, geophysical transport in electrically conducting and heat exchangers at low velocity conditions. The problem is modeled by a system of partial differential equations taking the effect of viscous dissipation, and these equations are simplified and solved analytically as a series solution using the Differential Transformation Method (DTM). The velocities and temperature profiles of the flow are plotted and discussed. Moreover, the conduit wall shear stress and heat flux are deduced and explained.

  7. Biological and artificial nerve conduit for repairing peripheral nerve defect

    Institute of Scientific and Technical Information of China (English)

    Xuetao Xie; Changqing Zhang

    2006-01-01

    OBJECTIVE: Recently, with the development of biological and artificial materials, the experimental and clinical studies on application of this new material-type nerve conduit for treatment of peripheral nerve defect have become the hotspot topics for professorial physicians.DATA SOURCES: Using the terms "nerve conduits, peripheral nerve, nerve regeneration and nerve transplantation" in English, we searched Pubmed database, which was published during January 2000 to June 2006, for the literatures related to repairing peripheral nerve defect with various materials. At the same time, we also searched Chinese Technical Scientific Periodical Database at the same time period by inputting" peripheral nerve defect, nerve repair, nerve regeneration and nerve graft" in Chinese.STUDY SELECTION: The materials were firstly selected, and literatures about study on various materials for repairing peripheral nerve defect and their full texts were also searched. Inclusive criteria: nerve conduits related animal experiments and clinical studies. Exclusive criteria: review or repetitive studies.DATA EXTRACTION: Seventy-nine relevant literatures were collected and 30 of them met inclusive criteria and were cited.DATA SYNTHESTS: Peripheral nerve defect, a commonly seen problem in clinic, is difficult to be solved. Autogenous nerve grafting is still the gold standard for repairing peripheral nerve defect, but because of its application limitation and possible complications, people studied nerve conduits to repair nerve defect. Nerve conduits consist of biological and artificial materials.CONCLUSION: There have been numerous reports about animal experimental and clinical studies of various nerve conduits, but nerve conduit, which is more ideal than autogenous nerve grafting, needs further clinical observation and investigation.

  8. Conduit enlargement during the precursory Plinian eruption of Aira Caldera, Japan

    Science.gov (United States)

    Geshi, Nobuo; Miyabuchi, Yasuo

    2016-09-01

    Increase in magma flux as the result of conduit enlargement is one of the key processes that triggered caldera collapse and eruption of the Ito ignimbrite from Aira Caldera at ~29 ka. We examine the total volume of the pumice fall deposit, vertical variations in grain size of pumice, and the lithic content in the Osumi pumice deposit to investigate the trigger for caldera collapse. Wider distribution of the later-stage unit and the upward coarsening of grain size throughout the Osumi pumice fall deposit indicate an increase in magma discharge toward the onset of collapse. The total volume of lithic fragments in the Osumi pumice fall deposit is estimated as ~1.6 km3, based on the lithic content in several representative outcrops and the total volume of the Osumi pumice fall deposit. The lithic fragments in the Osumi pumice fall deposit indicate intense mechanical erosion of the conduit during the Plinian eruption prior to caldera collapse. Caldera collapse requires decompression of the magma chamber by withdrawal of magma; effective enlargement of the conduit diameter during precursory eruptive phases is one of the important processes that subsequently allow the rapid discharge of a large volume of magma, which in turn facilitates decompression of the reservoir and induces caldera collapse.

  9. Ground Penetrating Radar Field Studies of Lunar-Analog Geologic Settings and Processes: Barringer Meteor Crater and Northern Arizona Volcanics

    Science.gov (United States)

    Russell, P. S.; Grant, J. A.; Williams, K. K.; Bussey, B.

    2010-12-01

    Ground-Penetrating Radar (GPR) data from terrestrial analog environments can help constrain models for evolution of the lunar surface, aid in interpretation of orbital SAR data, and help predict what might be encountered in the subsurface during future, landed, scientific or engineering operations on the Moon. GPR can yield insight into the physical properties, clast-size distribution, and layering of the subsurface, granting a unique view of the processes affecting an area over geologic time. The purpose of our work is to demonstrate these capabilities at sites at which geologic processes, settings, and/or materials are similar to those that may be encountered on the moon, especially lava flows, impact-crater ejecta, and layered materials with varying properties. We present results from transects obtained at Barringer Meteor Crater, SP Volcano cinder cone, and Sunset Crater Volcano National Monument, all in northern Arizona. Transects were taken at several sites on the ejecta of Meteor Crater, all within a crater radius (~400 m) of the crater rim. Those taken across ejecta lobes or mounds reveal the subsurface contact of the ejecta upper surface and overlying, embaying sediments deposited by later alluvial, colluvial, and/or aeolian processes. Existing mine shafts and pits on the south side of the crater provide cross sections of the subsurface against which we compare adjacent GPR transects. The ‘actual’ number, size, and depth of clasts in the top 1-2 m of the subsurface are estimated from photos of the exposed cross sections. In GPR radargrams, reflections attributed to blocks in the top 2-5 m of the subsurface are counted, and their depth distribution noted. Taking GPR measurements along a transect at two frequencies (200 and 400 MHz) and to various depths, we obtain the ratio of the actual number of blocks in the subsurface to the number detectable with GPR, as well as an assessment of how GPR detections in ejecta decline with depth and depend on antenna

  10. Coherent-subspace array processing based on wavelet covariance: an application to broad-band, seismo-volcanic signals

    Science.gov (United States)

    Saccorotti, G.; Nisii, V.; Del Pezzo, E.

    2008-07-01

    Long-Period (LP) and Very-Long-Period (VLP) signals are the most characteristic seismic signature of volcano dynamics, and provide important information about the physical processes occurring in magmatic and hydrothermal systems. These events are usually characterized by sharp spectral peaks, which may span several frequency decades, by emergent onsets, and by a lack of clear S-wave arrivals. These two latter features make both signal detection and location a challenging task. In this paper, we propose a processing procedure based on Continuous Wavelet Transform of multichannel, broad-band data to simultaneously solve the signal detection and location problems. Our method consists of two steps. First, we apply a frequency-dependent threshold to the estimates of the array-averaged WCO in order to locate the time-frequency regions spanned by coherent arrivals. For these data, we then use the time-series of the complex wavelet coefficients for deriving the elements of the spatial Cross-Spectral Matrix. From the eigenstructure of this matrix, we eventually estimate the kinematic signals' parameters using the MUltiple SIgnal Characterization (MUSIC) algorithm. The whole procedure greatly facilitates the detection and location of weak, broad-band signals, in turn avoiding the time-frequency resolution trade-off and frequency leakage effects which affect conventional covariance estimates based upon Windowed Fourier Transform. The method is applied to explosion signals recorded at Stromboli volcano by either a short-period, small aperture antenna, or a large-aperture, broad-band network. The LP (0.2 2s) of the explosion recordings from the broad-band network. Source locations obtained this way are fully compatible with those retrieved from application of more traditional (and computationally expensive) time-domain techniques, such as the Radial Semblance method.

  11. Urea Fertilizer and pH Influence on Sorption Process of Flumetsulam and MCPA Acidic Herbicides in a Volcanic Soil.

    Science.gov (United States)

    Palma, Graciela; Jorquera, Milko; Demanet, Rolando; Elgueta, Sebastian; Briceño, Gabriela; de la Luz Mora, María

    2016-01-01

    The aim of this study was to evaluate the influence of urea fertilizer and pH on the sorption process of two acidic herbicides, flumetsulam (2',6'-difluoro-5-methyl[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonanilide) and MCPA (4-chloro--tolyloxyacetic acid), on an Andisol. Urea reduced the adsorption of MCPA but not that of flumetsulam. The Freundlich parameter of MCPA decreased from 8.5 to 5.1 mg L kg. This finding could be attributed to an increase in dissolved organic C due to an initial increase in soil pH for urea application. The higher acidic character of MCPA compared with that of flumetsulam produced a greater hydrolysis of urea, leading to a further pH increase. A marked effect of pH on the adsorption of both herbicides was observed. The organic C distribution coefficient () values for flumetsulam were in the range of 74 to 10 L kg, while those of MCPA were in the range of 208 to 45 L kg. In the kinetic studies, the pseudo-second-order model appeared to fit the data best ( > 0.994). The initial adsorption rates () ranged from 20.00 to 4.59 mg kg h for flumetsulam and from 125.00 to 25.60 mg kg hfor MCPA. Both herbicides were adsorbed rapidly during the first stage of the sorption process, and the rates of sorption were dependent on pH. The application of the Elovich and Weber-Morris models led us to conclude that mass transfer through the boundary layer and, to a lesser degree, intraparticle diffusion were influenced by the chemical character of the herbicide. These results suggest that urea application could increase leaching of acid herbicides in soils.

  12. The dynamic and ever-changing volcanic nature of Iceland -An outdoor laboratory for education on natural processes and the human impacts on them-

    Science.gov (United States)

    Petursdottir, Thorunn; Finger, David

    2015-04-01

    "Tell me and I will forget, show me and I may remember, involve me and I will understand" (Chinese Proverb). Throughout the global history fundamental knowledge on utilizing natural resources, nowadays known as ecoliteracy, was passed on to next generations by our ancestors. Nevertheless, their practices were often unsustainable and lead directly or indirectly to severe ecosystem degradation. Nowadays, overexploitation of natural resources is still a global main driver for ecological degradation, water quality decrease and climate change. While ecoliteracy is still an essential knowledge, the societal structures required to maintain the knowledge have diminished. Today, about 80% of the population in Western countries lives in urban areas dominated by concrete structures with frequently only isolated green spaces. Environmental education is dominated by theoretical concepts taught using a wide range of multimedia technologies to simulate direct experiences of natural processes. Nevertheless, these technologies can only provide a superficial insight into the functioning of natural processes. Only direct on-sight investigations can provide a thorough experience of the dynamic, ever-changing environmental processes. Iceland is a 103,000 km2 large island, located on the Mid Atlantic Ridge just south of the Arctic Circle. In that area the earth crust is only a few km thick, leading to frequent volcanic eruptions and seismic activity. Due to the long winter and the wet climate glaciers formed on all major peaks and cover 11% of the island. Most riverbeds are in their pristine state and water quality is in general excellent. The Icelandic nature may look pristine but is indeed severely degraded. Unsustainable landuse, namely deforestation and overgrazing, in an environment characterized by harsh winters and volcanic activities had devastating effects on the nature. Since settlement 1100 years ago 40% of its vegetation and soil have been lost. Soil conservation and

  13. Increased axonal regeneration through a biodegradable amnionic tube nerve conduit: effect of local delivery and incorporation of nerve growth factor/hyaluronic acid media.

    Science.gov (United States)

    Mohammad, J A; Warnke, P H; Pan, Y C; Shenaq, S

    2000-01-01

    The authors emphasize the possible pharmacological enhancement of axonal regeneration using a specific growth factor/ extracellular media incorporated in a biodegradable nonneural nerve conduit material. They investigated the early effects on nerve regeneration of continuous local delivery of nerve growth factor (NGF) and the local incorporation of hyaluronic acid (HA) inside a newly manufactured nerve conduit material from fresh human amnionic membrane. Human amnionic membrane contains important biochemical factors that play a major neurotrophic role in the nerve regeneration process. The process of manufacturing a nerve conduit from fresh human amnionic membrane is described. This nerve conduit system was used in rabbits to bridge a 25-mm nerve gap over 3 months. NGF was released locally, over 28 days, at the distal end of the tube via a system of slow release, and HA was incorporated inside the lumen of the tube at the time of surgery. NGF/HA treatment promoted axonal regeneration across the amnionic tube nerve conduit (8,962 +/- 383 myelinated axons) 45% better than the nontreated amnionic tube group (6,180 +/- 353 myelinated axons). The authors demonstrate that NGF/HA media enhances additional axonal regeneration in the amnionic tube nerve conduit. This result is secondary to the effect of the amnion promoting biochemical factors, in combination with the NGF/HA effect on facilitating early events in the nerve regeneration process.

  14. Volcanism and associated hazards: the Andean perspective

    Science.gov (United States)

    Tilling, R. I.

    2009-12-01

    Andean volcanism occurs within the Andean Volcanic Arc (AVA), which is the product of subduction of the Nazca Plate and Antarctica Plates beneath the South America Plate. The AVA is Earth's longest but discontinuous continental-margin volcanic arc, which consists of four distinct segments: Northern Volcanic Zone, Central Volcanic Zone, Southern Volcanic Zone, and Austral Volcanic Zone. These segments are separated by volcanically inactive gaps that are inferred to indicate regions where the dips of the subducting plates are too shallow to favor the magma generation needed to sustain volcanism. The Andes host more volcanoes that have been active during the Holocene (past 10 000 years) than any other volcanic region in the world, as well as giant caldera systems that have produced 6 of the 47 largest explosive eruptions (so-called "super eruptions") recognized worldwide that have occurred from the Ordovician to the Pleistocene. The Andean region's most powerful historical explosive eruption occurred in 1600 at Huaynaputina Volcano (Peru). The impacts of this event, whose eruptive volume exceeded 11 km3, were widespread, with distal ashfall reported at distances >1000 km away. Despite the huge size of the Huaynaputina eruption, human fatalities from hazardous processes (pyroclastic flows, ashfalls, volcanogenic earthquakes, and lahars) were comparatively small owing to the low population density at the time. In contrast, lahars generated by a much smaller eruption (indecisiveness by government officials, rather than any major deficiencies in scientific data. Ruiz's disastrous outcome, however, together with responses to subsequent hazardous eruptions in Chile, Colombia, Ecuador, and Peru has spurred significant improvements in reducing volcano risk in the Andean region. But much remains to be done.

  15. Volcanism and associated hazards: The Andean perspective

    Science.gov (United States)

    Tilling, R.I.

    2009-01-01

    Andean volcanism occurs within the Andean Volcanic Arc (AVA), which is the product of subduction of the Nazca Plate and Antarctica Plates beneath the South America Plate. The AVA is Earth's longest but discontinuous continental-margin volcanic arc, which consists of four distinct segments: Northern Volcanic Zone, Central Volcanic Zone, Southern Volcanic Zone, and Austral Volcanic Zone. These segments are separated by volcanically inactive gaps that are inferred to indicate regions where the dips of the subducting plates are too shallow to favor the magma generation needed to sustain volcanism. The Andes host more volcanoes that have been active during the Holocene (past 10 000 years) than any other volcanic region in the world, as well as giant caldera systems that have produced 6 of the 47 largest explosive eruptions (so-called "super eruptions") recognized worldwide that have occurred from the Ordovician to the Pleistocene. The Andean region's most powerful historical explosive eruption occurred in 1600 at Huaynaputina Volcano (Peru). The impacts of this event, whose eruptive volume exceeded 11 km3, were widespread, with distal ashfall reported at distances >1000 km away. Despite the huge size of the Huaynaputina eruption, human fatalities from hazardous processes (pyroclastic flows, ashfalls, volcanogenic earthquakes, and lahars) were comparatively small owing to the low population density at the time. In contrast, lahars generated by a much smaller eruption (indecisiveness by government officials, rather than any major deficiencies in scientific data. Ruiz's disastrous outcome, however, together with responses to subsequent hazardous eruptions in Chile, Colombia, Ecuador, and Peru has spurred significant improvements in reducing volcano risk in the Andean region. But much remains to be done.

  16. Nature, Source and Composition of Volcanic Ash in Surficial Sediments Around the Zhongsha Islands

    Institute of Scientific and Technical Information of China (English)

    YAN Quanshu; SHI Xuefa; WANG Xinyu

    2008-01-01

    Volcanic detrital sediments are a unique indicator for reconstructing the petrogenetie evolution of submarine volcanic terrains. Volcanic ash in surficial sediments around the Zhongsha Islands includes three kinds of volcanogenic detritus, i.e., brown volcanic glass, colorless volcanic glass and volcanic scoria. The major element characteristics show that bimodal volcanic activity may have taken place in the northern margin of the South China Sea, with brown volcanic glass and colorless volcanic glass repre-senting the maric end-member and felsie end-member, respectively. Fractional crystallization is the main process for magma evolu-tion. The nature of the volcanic activity implies that the origin of volcanic activity was related to extensional tectonic settings, which is corresponding to an extensional geodynamie setting in the Xisha Trench, and supports the notion, which is based on geophysical data and petrology, that there may exist a mantle plume around the Hainan Island.

  17. Active spreading processes at ultraslow mid-ocean ridges: The 1999-2001 seismo-volcanic episode at 85°E Gakkel ridge, Arctic Ocean

    Science.gov (United States)

    Schlindwein, Vera; Riedel, Carsten; Korger, Edith; Läderach, Christine

    2010-05-01

    The rate of magma and crustal production at mid-ocean ridges is thought to decrease with decreasing spreading rate. At ultraslow spreading rates below 10-20 mm/y full rate, heat loss by conduction greatly reduces melt production with less melt produced at increasingly greater depths. Gakkel Ridge, the actively spreading mid-ocean ridge in the Arctic Ocean, opens at rates of 14 mm/y in the west decreasing to less than 6 mm/y at its eastern termination and demonstrates that magma production is not only a function of spreading rate. Whereas amagmatic spreading takes place at rates of about 12-10 mm/y, focussed melt production occurs at even lower spreading rates in long-lived discrete volcanic centres. One such centre is the 85°E volcanic complex at eastern Gakkel ridge where in 1999 a teleseismically recorded earthquake swarm consisting of more than 250 earthquakes over 9 months signalled the onset of an active spreading episode. The earthquake swarm is believed to be associated with volcanic activity although no concurrent lava effusion was found. We analysed the teleseismic earthquake swarm together with visual observation and microseismic data recorded at this site in 2001 and 2007 and noted the following characteristics which may be indicative for volcanic spreading events at the still poorly explored ultraslow spreading ridges: - unusual duration: The 1999 earthquake swarm lasted over 9 months rather than a few weeks as observed on faster spreading ridges. In addition, in 2001 seismoacoustic sounds which we interpret as gas discharge in Strombolian eruptions and a giant event plume maintained over more than one year indicate waxing and waning volcanic activity since 1999. - unusual strength: The earthquake swarm was detected at teleseismic distances of more than 1000 km and included 11 events with a magnitude >5. No other confirmed mid-ocean ridge eruption released a comparable seismic moment. Rather than focussing in a narrow area or showing pronounced

  18. Study and management of atmospheric exhaust gas in acetic acid fermentation developing a new process for alcohol vinegar production; Etude et maitrise des rejets atmospheriques en vinaigrerie, developpement d'un procede nouveau de conduite de la fermentation acetique

    Energy Technology Data Exchange (ETDEWEB)

    Pochat Bohatier, C.

    1999-12-06

    The aim of the study was to examine emissions of volatile organic compounds (VOCs) during acetic (acid) fermentation. The first part of the study presents the methodology developed to reproduce production cycles for spirit vinegar and to analyse gas effluents. The second part describes the origin and quantification of the emissions (ethanol, acetic acid, acetaldehyde and ethyl acetate). The acetic acid is produced by bacterial metabolism while the ethyl acetate is a result of the chemical reaction of esterification. By modelling the emissions during batch processing we were able to identify the various parameters involved when VOCs are carried along by the fermentation gases. The quantities of ethyl acetate depend on the length of time the diluted alcohol is stored, and on its composition. By using a fed-batch method with a continuous supply of ethanol we could reduce alcohol emissions. The third part of the study develops the kinetics studies carried out to adapt the fed-batch process to acetic acid fermentation. The influence of ethanol, either in terms of deficiency or inhibition, is minimized between 8 and 16 g.1-1. A study of the growth rate of bacteria in relation to the amount of acetic acid showed that the latter was highly inhibitive. There is a critical concentration of acetic acid at which the growth of bacteria stops, and the death rate of the culture increases rapidly. The latter depends on the composition of the culture's medium; the corresponding pH of the concentration is between 2.25 and 2.28. By limiting the formation of ethyl acetate in the diluted alcohol and by controlling the concentration of ethanol at 16 g.l -1 per fermentation, the VOC emissions are reduced by 30% and the yield increases as a result. (author)

  19. Crystal Zoning Constrains on the Processes and Time Scales Involved in Monogenetic Mafic Volcanism (Tenerife, Canary Islands)

    Science.gov (United States)

    Albert, H.; Costa Rodriguez, F.; Marti, J.

    2014-12-01

    Most of the historical eruptive activity in Tenerife has been relatively mafic and mildly-explosive monogenetic eruptions, and thus it seems that this activity is the most likely in the near future. Here we investigate the processes and time scales that lead to such eruptions with the aim to better interpret and plan for any possible unrest in the island. We focus on three historical eruptions: Siete Fuentes (December 31 1704-January 1705), Fasnia (January 5-January 13 1705) and Arafo (February 2-February 26 1705) issued from a 10 km long basaltic fissure eruption oriented N45E and covering an area of 10.4 km2. The erupted volume increases by 5-fold from the first to the last eruption. All magmas are tephritic, although the bulk-rock becomes more mafic with time due to accumulation of olivine with Cr-spinel inclusions, and clinopyroxene rather than to the appearance of a truly more primitive melt. Olivine core compositions of the three eruptions range between Fo79 and Fo87. Frequency histograms show three main populations: at Fo79-80, Fo80-82 and Fo84-87 displaying normal and reverse zoning. Thermodynamic calculations show that only cores with Fo80-82 are in equilibrium with the whole rock. Clinopyroxene phenocrysts can have large pools of matrix glass and show rims of different composition. Only the rims, with Mg#84-86, are in equilibrium with the whole-rock. Considering olivine cores and clinopyroxene rims in equilibrium we obtained a temperature range of 1150-1165°C, and MELTS calculations suggest pressures of 1 to 5 kbar. The variety of olivine core populations reflects mixing and mingling between three different magmas, and their proportions have changed with time from Siete Fuentes to Arafo. Most crystals have complex zoning profiles that record two events: (1) one of magma mixing/mingling at depth, (2) another of magma transport and ascent to the surface. Magma mixing at depth ranges from about 3 months to two years and is similar for the three eruptions

  20. Source Dynamics of Long-Period Seismicity in Volcanic and Hydrothermal Systems

    Science.gov (United States)

    Chouet, B. A.

    2006-12-01

    Long-period (LP) seismicity, including individual LP events and tremor, is widely observed in relation to magmatic and hydrothermal activities in volcanic areas and is recognized as a precursory phenomenon for eruptive activity. The waveform of the LP event is characterized by simple decaying harmonic oscillations except for a brief interval at the event onset. This characteristic event signature is commonly interpreted as oscillations of a fluid-filled resonator in response to a time-localized excitation. By the same token, tremor may be viewed as oscillations of the same resonator in response to a sustained excitation. Because the properties of the resonator system at the source of the LP event can be inferred from the complex frequencies of the decaying harmonic oscillations in the tail of the seismogram, these events are particularly important in the quantification of volcanic and hydrothermal processes. The damped oscillations in the LP coda are characterized by two parameters, T and Q, where T is the period of the dominant mode of oscillation, and Q is the quality factor of the oscillatory system representing the combined effects of radiation and intrinsic losses. Typical periods observed for LP events are in the range 0.2 - 2 s, while observed Q range from values near 1 to values larger than 100. Waveform inversions of LP signals carried out so far point to a crack geometry at the source of these events. Detailed investigations of the oscillating characteristics of LP sources based on the fluid-filled crack model suggest source dimensions ranging from tens to several hundred meters. Such studies further indicate that dusty gases and bubbly basalt are the most common types of fluids involved at the source of LP events in magmatic systems, while misty gases, steam and bubbly water commonly represent LP events of hydrothermal origin. Observations carried out in different volcanic settings point to a wide variety of LP excitation mechanisms. At Stromboli

  1. Sciatic nerve repair using adhesive bonding and a modiifed conduit

    Institute of Scientific and Technical Information of China (English)

    Xiangdang Liang; Hongfei Cai; Yongyu Hao; Geng Sun; Yaoyao Song; Wen Chen

    2014-01-01

    When repairing nerves with adhesives, most researchers place glue directly on the nerve stumps, but this method does not ifx the nerve ends well and allows glue to easily invade the nerve ends. In this study, we established a rat model of completely transected sciatic nerve injury and re-paired it using a modiifed 1 cm-length conduit with inner diameter of 1.5 mm. Each end of the cylindrical conduit contains a short linear channel, while the enclosed central tube protects the nerve ends well. Nerves were repaired with 2-octyl-cyanoacrylate and suture, which complement the function of the modiifed conduit. The results demonstrated that for the same conduit, the av-erage operation time using the adhesive method was much shorter than with the suture method. No signiifcant differences were found between the two groups in sciatic function index, motor evoked potential latency, motor evoked potential amplitude, muscular recovery rate, number of medullated nerve fibers, axon diameter, or medullary sheath thickness. Thus, the adhesive method for repairing nerves using a modiifed conduit is feasible and effective, and reduces the operation time while providing an equivalent repair effect.

  2. Paleoproterozoic (~1.88Ga felsic volcanism of the Iricoumé Group in the Pitinga Mining District area, Amazonian Craton, Brazil: insights in ancient volcanic processes from field and petrologic data

    Directory of Open Access Journals (Sweden)

    Ronaldo Pierosan

    2011-09-01

    Full Text Available The Iricoumé Group correspond to the most expressive Paleoproterozoic volcanism in the Guyana Shield, Amazonian craton. The volcanics are coeval with Mapuera granitoids, and belong to the Uatumã magmatism. They have U-Pb ages around 1880 Ma, and geochemical signatures of α-type magmas. Iricoumé volcanics consist of porphyritic trachyte to rhyolite, associated to crystal-rich ignimbrites and co-ignimbritic fall tuffs and surges. The amount and morphology of phenocrysts can be useful to distinguish lava (flow and dome from hypabyssal units. The morphology of ignimbrite crystals allows the distinction between effusive units and ignimbrite, when pyroclasts are obliterated. Co-ignimbritic tuffs are massive, and some show stratifications that suggest deposition by current traction flow. Zircon and apatite saturation temperatures vary from 799°C to 980°C, are in agreement with most temperatures of α-type melts and can be interpreted as minimum liquidus temperature. The viscosities estimation for rhyolitic and trachytic compositions yield values close to experimentally determined melts, and show a typical exponential decay with water addition. The emplacement of Iricoumé volcanics and part of Mapuera granitoids was controlled by ring-faults in an intracratonic environment. A genesis related to the caldera complex setting can be assumed for the Iricoumé-Mapuera volcano-plutonic association in the Pitinga Mining District.O Grupo Iricoumé corresponde ao mais expressivo vulcanismo Paleoproterozóico do Escudo das Guianas, craton Amazônico. As rochas vulcânicas são coexistentes com os granitóides Mapuera, e pertencem ao magmatismo Uatumã. Possuem idades U-Pb em torno 1888 Ma, e assinaturas geoquímicas de magmas tipo-A. As vulcânicas do Iricoumé consistem de traquitos a riolitos porfiríticos, associados a ignimbritos ricos em cristal e tufos co-ignimbríticos de queda e surge. A quantidade e a morfologia dos fenocristais podem ser

  3. Bayesian inversion of data from effusive volcanic eruptions using physics-based models: Application to Mount St. Helens 2004--2008

    Science.gov (United States)

    Anderson, Kyle; Segall, Paul

    2013-01-01

    Physics-based models of volcanic eruptions can directly link magmatic processes with diverse, time-varying geophysical observations, and when used in an inverse procedure make it possible to bring all available information to bear on estimating properties of the volcanic system. We develop a technique for inverting geodetic, extrusive flux, and other types of data using a physics-based model of an effusive silicic volcanic eruption to estimate the geometry, pressure, depth, and volatile content of a magma chamber, and properties of the conduit linking the chamber to the surface. A Bayesian inverse formulation makes it possible to easily incorporate independent information into the inversion, such as petrologic estimates of melt water content, and yields probabilistic estimates for model parameters and other properties of the volcano. Probability distributions are sampled using a Markov-Chain Monte Carlo algorithm. We apply the technique using GPS and extrusion data from the 2004–2008 eruption of Mount St. Helens. In contrast to more traditional inversions such as those involving geodetic data alone in combination with kinematic forward models, this technique is able to provide constraint on properties of the magma, including its volatile content, and on the absolute volume and pressure of the magma chamber. Results suggest a large chamber of >40 km3 with a centroid depth of 11–18 km and a dissolved water content at the top of the chamber of 2.6–4.9 wt%.

  4. Advanced data processing of airborne electromagnetic data for imaging hidden conduit networks in the coastal karst plain of Tulum (Mexico); Tecnicas avanzadas de analisis de datos electromagneticos aerotransportados para cartografia de redes de conductos karsticos de la planicie costera de Tulum (Mexico)

    Energy Technology Data Exchange (ETDEWEB)

    Schiller, A.; Schattauer, I.; Ottowitz, D.

    2016-07-01

    This study is part of a series of international research cooperations which commenced in 2007 and are still ongoing. The study area is located on the east coast of the Yucatan Peninsula, Mexico, and comprises the northern most part of the Sian Kaan biosphere reserve, a coastal wetland of international importance, as well as the city of Tulum in the state of Quintana Roo, and part of the second largest barrier reef in the world some 300 metres to one kilometre off shore. Two airborne surveys, conducted in 2007 and 2008 by the Geological Survey of Austria, covered an area of some 200 square kilometres, including the well-known Ox Bel Ha cave system, already mapped by exploration divers. In order to get additional ground truth data and input for the hydrological model, extended ground geophysical campaigns have been conducted an - nually. The first processing of the airborne electromagnetic (AEM) data revealed not only a clear signature from known caves but also the image of a vast, unexplored, hidden conduit network. However, lateral and depth resolution was limited due to measurement drift and noise as well the specific behaviour of the ap - plied inversion technique. Newly developed algorithms for processing AEM data and inversion results have improved the signal-to-noise ratio significantly and enabled the imaging of well defined structures in the underground. Therefore, the AEM method is now capable of quickly deliver crucial structural information of karst-water regimes in difficult accessible areas with unique depth information compared to previous studies. (Author)

  5. Evaluation of biodegradable polymer conduits--poly(L-lactic acid)--for guiding sciatic nerve regeneration in mice.

    Science.gov (United States)

    Goulart, Camila Oliveira; Lopes, Fátima Rosalina Pereira; Monte, Zulmira Oliveira; Dantas, Severino Valentim; Souto, Allana; Oliveira, Júlia Teixeira; Almeida, Fernanda Martins; Tonda-Turo, Chiara; Pereira, Cristina Cardoso; Borges, Cristiano Piacsek; Martinez, Ana Maria Blanco

    2016-04-15

    Polymeric biomaterials are often used for stimulating nerve regeneration. Among different conduits, poly(lactide acid) - PLA polymer is considered to be a good substrate due to its biocompatibility and resorbable characteristics. This polymer is an aliphatic polyester which has been mostly used in biomedical application. It is an organic compound with low allergenic potential, low toxicity, high biocompatibility and predictable kinetics of degradation. In this study we fabricated and evaluated a PLA microporous hollow fiber as a conduit for its ability to bridge a nerve gap in a mouse sciatic nerve injury model. The PLA conduit was prepared from a polymer solution, throughout extrusion technique. The left sciatic nerve of C57BL/6 mouse was transected and the nerve stumps were placed into a resorbable PLA (PLA group) or a PCL conduit (PCL group), n=5 each group. We have also used another group in which the nerves were repaired by autograft (autograft group, n=5). Motor function was analyzed according to sciatic functional index (SFI). After 56days, the regenerated nerves were processed for light and electron microscopy and morphometric analyses were performed. A quantitative analysis of regenerated nerves showed significant increase in the number of myelinated fibers and blood vessels in animals that received PLA conduit. The PLA group exhibited better overall tissue organization compared to other groups. Presenting well-organized bundles, many regenerating clusters composed of preserved nerve fibers surrounded by layers of compacted perineurium-like cells. Also the SFI revealed a significant improvement in functional recovery. This work suggests that PLA conduits are suitable substrate for cell survival and it provides an effective strategy to be used to support axonal growth becoming a potential alternative to autograft.

  6. Natural Occurring Silks and Their Analogues as Materials for Nerve Conduits.

    Science.gov (United States)

    Radtke, Christine

    2016-10-20

    Spider silk and its synthetic derivatives have a light weight in combination with good strength and elasticity. Their high cytocompatibility and low immunogenicity make them well suited for biomaterial products such as nerve conduits. Silk proteins slowly degrade enzymatically in vivo, thus allowing for an initial therapeutic effect such as in nerve scaffolding to facilitate endogenous repair processes, and then are removed. Silks are biopolymers naturally produced by many species of arthropods including spiders, caterpillars and mites. The silk fibers are secreted by the labial gland of the larvae of some orders of Holometabola (insects with pupa) or the spinnerets of spiders. The majority of studies using silks for biomedical applications use materials from silkworms or spiders, mostly of the genus Nephila clavipes. Silk is one of the most promising biomaterials with effects not only in nerve regeneration, but in a number of regenerative applications. The development of silks for human biomedical applications is of high scientific and clinical interest. Biomaterials in use for biomedical applications have to meet a number of requirements such as biocompatibility and elicitation of no more than a minor inflammatory response, biodegradability in a reasonable time and specific structural properties. Here we present the current status in the field of silk-based conduit development for nerve repair and discuss current advances with regard to potential clinical transfer of an implantable nerve conduit for enhancement of nerve regeneration.

  7. Optimum air-demand ratio for maximum aeration efficiency in high-head gated circular conduits.

    Science.gov (United States)

    Ozkan, Fahri; Tuna, M Cihat; Baylar, Ahmet; Ozturk, Mualla

    2014-01-01

    Oxygen is an important component of water quality and its ability to sustain life. Water aeration is the process of introducing air into a body of water to increase its oxygen saturation. Water aeration can be accomplished in a variety of ways, for instance, closed-conduit aeration. High-speed flow in a closed conduit involves air-water mixture flow. The air flow results from the subatmospheric pressure downstream of the gate. The air entrained by the high-speed flow is supplied by the air vent. The air entrained into the flow in the form of a large number of bubbles accelerates oxygen transfer and hence also increases aeration efficiency. In the present work, the optimum air-demand ratio for maximum aeration efficiency in high-head gated circular conduits was studied experimentally. Results showed that aeration efficiency increased with the air-demand ratio to a certain point and then aeration efficiency did not change with a further increase of the air-demand ratio. Thus, there was an optimum value for the air-demand ratio, depending on the Froude number, which provides maximum aeration efficiency. Furthermore, a design formula for aeration efficiency was presented relating aeration efficiency to the air-demand ratio and Froude number.

  8. Natural Occurring Silks and Their Analogues as Materials for Nerve Conduits

    Science.gov (United States)

    Radtke, Christine

    2016-01-01

    Spider silk and its synthetic derivatives have a light weight in combination with good strength and elasticity. Their high cytocompatibility and low immunogenicity make them well suited for biomaterial products such as nerve conduits. Silk proteins slowly degrade enzymatically in vivo, thus allowing for an initial therapeutic effect such as in nerve scaffolding to facilitate endogenous repair processes, and then are removed. Silks are biopolymers naturally produced by many species of arthropods including spiders, caterpillars and mites. The silk fibers are secreted by the labial gland of the larvae of some orders of Holometabola (insects with pupa) or the spinnerets of spiders. The majority of studies using silks for biomedical applications use materials from silkworms or spiders, mostly of the genus Nephila clavipes. Silk is one of the most promising biomaterials with effects not only in nerve regeneration, but in a number of regenerative applications. The development of silks for human biomedical applications is of high scientific and clinical interest. Biomaterials in use for biomedical applications have to meet a number of requirements such as biocompatibility and elicitation of no more than a minor inflammatory response, biodegradability in a reasonable time and specific structural properties. Here we present the current status in the field of silk-based conduit development for nerve repair and discuss current advances with regard to potential clinical transfer of an implantable nerve conduit for enhancement of nerve regeneration. PMID:27775616

  9. Natural Occurring Silks and Their Analogues as Materials for Nerve Conduits

    Directory of Open Access Journals (Sweden)

    Christine Radtke

    2016-10-01

    Full Text Available Spider silk and its synthetic derivatives have a light weight in combination with good strength and elasticity. Their high cytocompatibility and low immunogenicity make them well suited for biomaterial products such as nerve conduits. Silk proteins slowly degrade enzymatically in vivo, thus allowing for an initial therapeutic effect such as in nerve scaffolding to facilitate endogenous repair processes, and then are removed. Silks are biopolymers naturally produced by many species of arthropods including spiders, caterpillars and mites. The silk fibers are secreted by the labial gland of the larvae of some orders of Holometabola (insects with pupa or the spinnerets of spiders. The majority of studies using silks for biomedical applications use materials from silkworms or spiders, mostly of the genus Nephila clavipes. Silk is one of the most promising biomaterials with effects not only in nerve regeneration, but in a number of regenerative applications. The development of silks for human biomedical applications is of high scientific and clinical interest. Biomaterials in use for biomedical applications have to meet a number of requirements such as biocompatibility and elicitation of no more than a minor inflammatory response, biodegradability in a reasonable time and specific structural properties. Here we present the current status in the field of silk-based conduit development for nerve repair and discuss current advances with regard to potential clinical transfer of an implantable nerve conduit for enhancement of nerve regeneration.

  10. Possible conduit-matrix water exchange signatures outlined at a karst spring.

    Science.gov (United States)

    Mitrofan, Horia; Marin, Constantin; Povară, Ioan

    2015-04-01

    During a significant flood event, reversible water exchanges may occur between a karst conduit and its adjacent porous rock (frequently designated as "matrix"): while the flood pulse rises, some conduit-derived water is forced into the matrix; then, as the flood recedes, the same water flows back into the stream passage. The present note addresses such a karst setting in the Carpathian Mountains (Romania), where in addition, a usually stable flux of chloride originating in a natural saline inflow, was being mixed with a variable flow of karst freshwater. For that particular case, with the above-mentioned process of matrix storage/release from storage assumedly taking place downstream of the mixing site, two distinct chemical signatures could be noticed during a flood event: an initial depletion in the spring flow chloride flux, subsequently followed by a comparable chloride flux enrichment (the depletion and the enrichment being outlined with respect to the essentially stable chloride flux value that had been noticed to persist at the spring over a long period of flow rate recession). Concomitantly with such flood-induced fluctuations in the spring chloride flux, the spring discharge displayed, for long periods, abnormally slow variations: the latter likely indicated that the spring supply rate actual oscillations were buffered by the reversible water exchanges which took place between the karst conduit and its adjacent matrix. On the whole, these results show that conduit-matrix water exchanges could be interpreted by simple mass balance calculations that involved fluxes of a conservative tracer (the chloride ion in that particular case). © 2014, National Ground Water Association.

  11. Differential expression of GAP-43 and neurofilament during peripheral nerve regeneration through bio-artificial conduits.

    Science.gov (United States)

    Carriel, Víctor; Garzón, Ingrid; Campos, Antonio; Cornelissen, Maria; Alaminos, Miguel

    2017-02-01

    Nerve conduits are promising alternatives for repairing nerve gaps; they provide a close microenvironment that supports nerve regeneration. In this sense, histological analysis of axonal growth is a determinant to achieve successful nerve regeneration. To evaluate this process, the most-used immunohistochemical markers are neurofilament (NF), β-III tubulin and, infrequently, GAP-43. However, GAP-43 expression in long-term nerve regeneration models is still poorly understood. In this study we analysed GAP-43 expression and its correlation with NF and S-100, using three tissue-engineering approaches with different regeneration profiles. A 10 mm gap was created in the sciatic nerve of 12 rats and repaired using collagen conduits or collagen conduits filled with fibrin-agarose hydrogels or with hydrogels containing autologous adipose-derived mesenchymal stem cells (ADMSCs). After 12 weeks the conduits were harvested for histological analysis. Our results confirm the long-term expression of GAP-43 in all groups. The expression of GAP-43 and NF was significantly higher in the group with ADMSCs. Interestingly, GAP-43 was observed in immature, newly formed axons and NF in thicker and mature axons. These proteins were not co-expressed, demonstrating their differential expression in newly formed nerve fascicles. Our descriptive and quantitative histological analysis of GAP-43 and NFL allowed us to determine, with high accuracy, the heterogenic population of axons at different stages of maturation in three tissue-engineering approaches. Finally, to perform a complete assessment of axonal regeneration, the quantitative immunohistochemical evaluation of both GAP-43 and NF could be a useful quality control in tissue engineering. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.

  12. Volcanic studies at Katmai

    Energy Technology Data Exchange (ETDEWEB)

    1989-12-31

    The Continental Scientific Drilling Program (CSDP) is a national effort supported by the Department of Energy, the US Geological Survey, and the National Science Foundation. One of the projects proposed for the CSDP consists of drilling a series of holes in Katmai National Park in Alaska to give a third dimension to the model of the 1912 eruption of Novarupta, and to investigate the processes of explosive volcanism and hydrothermal transport of metals (Eichelberger et al., 1988). The proposal for research drilling at Katmai states that ``the size, youth, elevated temperature, and simplicity of the Novarupta vent make it a truly unique scientific target.`` The National Park Service (NPS), which has jurisdiction, is sympathetic to aims of the study. However, NPS wishes to know whether Katmai is indeed uniquely suited to the research, and has asked the Interagency Coordinating Group to support an independent assessment of this claim. NPS suggested the National Academy of Sciences as an appropriate organization to conduct the assessment. In response, the National Research Council -- the working arm of the Academy -- established, under the aegis of its US Geodynamics Committee, a panel whose specific charge states: ``The proposed investigation at Katmai has been extensively reviewed for scientific merit by the three sponsoring and participating agencies. Thus, the scientific merit of the proposed drilling at Katmai is not at issue. The panel will review the proposal for scientific drilling at Katmai and prepare a short report addressing the specific question of the degree to which it is essential that the drilling be conducted at Katmai as opposed to volcanic areas elsewhere in the world.``

  13. Biogeochemical processes involving dissolved CO2 and CH4 at Albano, Averno, and Monticchio meromictic volcanic lakes (Central-Southern Italy)

    Science.gov (United States)

    Cabassi, Jacopo; Tassi, Franco; Vaselli, Orlando; Fiebig, Jens; Nocentini, Matteo; Capecchiacci, Francesco; Rouwet, Dmitri; Bicocchi, Gabriele

    2013-01-01

    This paper focuses on the chemical and isotopic features of dissolved gases (CH4 and CO2) from four meromictic lakes hosted in volcanic systems of Central-Southern Italy: Lake Albano (Alban Hills), Lake Averno (Phlegrean Fields), and Monticchio Grande and Piccolo lakes (Mt. Vulture). Deep waters in these lakes are characterized by the presence of a significant reservoir of extra-atmospheric dissolved gases mainly consisting of CH4 and CO2. The δ13C-CH4 and δD-CH4 values of dissolved gas samples from the maximum depths of the investigated lakes (from -66.8 to -55.6 ‰ V-PDB and from -279 to -195 ‰ V-SMOW, respectively) suggest that CH4 is mainly produced by microbial activity. The δ13C-CO2 values of Lake Grande, Lake Piccolo, and Lake Albano (ranging from -5.8 to -0.4 ‰ V-PDB) indicate a significant CO2 contribution from sublacustrine vents originating from (1) mantle degassing and (2) thermometamorphic reactions involving limestone, i.e., the same CO2 source feeding the regional thermal and cold CO2-rich fluid emissions. In contrast, the relatively low δ13C-CO2 values (from -13.4 to -8.2 ‰ V-PDB) of Lake Averno indicate a prevalent organic CO2. Chemical and isotopic compositions of dissolved CO2 and CH4 at different depths are mainly depending on (1) CO2 inputs from external sources (hydrothermal and/or anthropogenic); (2) CO2-CH4 isotopic exchange; and (3) methanogenic and methanotrophic activity. In the epilimnion, vertical water mixing, free oxygen availability, and photosynthesis cause the dramatic decrease of both CO2 and CH4 concentrations. In the hypolimnion, where the δ13C-CO2 values progressively increase with depth and the δ13C-CH4 values show an opposite trend, biogenic CO2 production from CH4 using different electron donor species, such as sulfate, tend to counteract the methanogenesis process whose efficiency achieves its climax at the water-bottom sediment interface. Theoretical values, calculated on the basis of δ13C-CO2 values, and

  14. Modeling Reactive Transport in Coupled Groundwater-Conduit Systems

    Science.gov (United States)

    Spiessl, S. M.; Sauter, M.; Zheng, C.; Viswanathan, H. S.

    2002-05-01

    Modeling reactive transport in coupled groundwater-conduit systems requires consideration of two transport time scales in the flow and transport models. Consider for example a subsurface mine consisting of a network of highly conductive shafts, drifts or ventilation raises (i.e., conduits) within the considerably less permeable ore material (i.e., matrix). In the conduits, potential contaminants can travel much more rapidly than in the background aquifer (matrix). Since conduits cannot necessarily be regarded as a continuum, double continuum models are only of limited use for simulation of contaminant transport in such coupled groundwater-conduit systems. This study utilizes a "hybrid" flow and transport model in which contaminants can in essence be transported at a slower time scale in the matrix and at a faster time scale in the conduits. The hybrid flow model uses an approach developed by Clemens et al. (1996), which is based on the modelling of flow in a discrete pipe network, coupled to a continuum representing the low-permeability inter-conduit matrix blocks. Laminar or turbulent flow can be simulated in the different pipes depending on the flow conditions in the model domain. The three-dimensional finite-difference groundwater flow model MODFLOW (Harbaugh and McDonald, 1996) is used to simulate flow in the continuum. Contaminant transport within the matrix is simulated with a continuum approach using the three-dimensional multi-species solute transport model MT3DMS (Zheng and Wang, 1999), while that in the conduit system is simulated with a one-dimensional advective transport model. As a first step for reactive transport modeling in such systems, only equilibrium reactions among multiple species are considered by coupling the hybrid transport model to a geochemical speciation package. An idealized mine network developed by Viswanathan and Sauter (2001) is used as a test problem in this study. The numerical experiment is based on reference date collected from

  15. Lab-scale ash production by abrasion and collision experiments of porous volcanic samples

    Science.gov (United States)

    Mueller, S. B.; Lane, S. J.; Kueppers, U.

    2015-09-01

    In the course of explosive eruptions, magma is fragmented into smaller pieces by a plethora of processes before and during deposition. Volcanic ash, fragments smaller than 2 mm, has near-volcano effects (e.g. increasing mobility of PDCs, threat to human infrastructure) but may also cause various problems over long duration and/or far away from the source (human health and aviation matters). We quantify the efficiency of ash generation during experimental fracturing of pumiceous and scoriaceous samples subjected to shear and normal stress fields. Experiments were designed to produce ash by overcoming the yield strength of samples from Tenerife (Canary Islands, Spain), Sicily and Lipari Islands (Italy), with this study having particular interest in the < 355 μm fraction. Fracturing within volcanic conduits, plumes and pyroclastic density currents (PDCs) was simulated through a series of abrasion (shear) and collision (normal) experiments. An understanding of these processes is crucial as they are capable of producing very fine ash (< 10 μm). These particles can remain in the atmosphere for several days and may travel large distances (~ 1000s of km). This poses a threat to the aviation industry and human health. From the experiments we establish that abrasion produced the finest-grained material and up to 50% of the generated ash was smaller than 10 μm. In comparison, the collision experiments that applied mainly normal stress fields produced coarser grain sizes. Results were compared to established grain size distributions for natural fall and PDC deposits and good correlation was found. Energies involved in collision and abrasion experiments were calculated and showed an exponential correlation with ash production rate. Projecting these experimental results into the volcanic environment, the greatest amounts of ash are produced in the most energetic and turbulent regions of volcanic flows, which are proximal to the vent. Finest grain sizes are produced in PDCs

  16. Nerve guidance conduit with a hybrid structure of a PLGA microfibrous bundle wrapped in a micro/nanostructured membrane

    Directory of Open Access Journals (Sweden)

    Peng SW

    2017-01-01

    Full Text Available Shih-Wen Peng,1 Ching-Wen Li,2 Ing-Ming Chiu,3,4 Gou-Jen Wang1–3 1Graduate Institute of Biomedical Engineering, 2Department of Mechanical Engineering, 3PhD Program in Tissue Engineering and Regenerative Medicine, National Chung-Hsing University, Taichung, 4Institute of Cellular and System Medicine, National Health Research Institutes, Miaoli, Taiwan Abstract: Nerve repair in tissue engineering involves the precise construction of a scaffold to guide nerve cell regeneration in the desired direction. However, improvements are needed to facilitate the cell migration/growth rate of nerves in the center of a nerve conduit. In this paper, we propose a nerve guidance conduit with a hybrid structure comprising a microfibrous poly(lactic-co-glycolic acid (PLGA bundle wrapped in a micro/nanostructured PLGA membrane. We applied sequential fabrication processes, including photolithography, nano-electroforming, and polydimethylsiloxane casting to manufacture master molds for the repeated production of the PLGA subelements. After demolding it from the master molds, we rolled the microfibrous membrane into a bundle and then wrapped it in the micro/nanostructured membrane to form a nerve-guiding conduit. We used KT98/F1B-GFP cells to estimate the migration rate and guidance ability of the fabricated nerve conduit and found that both elements increased the migration rate 1.6-fold compared with a flat PLGA membrane. We also found that 90% of the cells in the hybrid nano/microstructured membrane grew in the direction of the designed patterns. After 3 days of culturing, the interior of the nerve conduit was filled with cells, and the microfiber bundle was also surrounded by cells. Our conduit cell culture results also demonstrate that the proposed micro/nanohybrid and microfibrous structures can retain their shapes. The proposed hybrid-structured conduit demonstrates a high capability for guiding nerve cells and promoting cell migration, and, as such, is

  17. Textural variations and fragmentation processes in peperite formed between felsic lava flow and wet substrate: An example from the Cretaceous Buan Volcanics, southwest Korea

    Science.gov (United States)

    Gihm, Yong Sik; Kwon, Chang Woo

    2017-02-01

    Multiple exposures of peperite within the Cretaceous Buan Volcanics, southwest Korea, have been examined in order to determine variations in their textural characteristics and to investigate their mode of formation. Along undulating boundaries between rhyolite (lava flow) and deformed host sediment expressed as a series of load and flame structures, exposures commonly contain two distinct types of peperite. Type-1 peperites are composed mostly of rounded juvenile clasts at their base and polyhedral juvenile clasts at their upper levels, interpreted to have formed via a two-stage process. Firstly, abrasion of juvenile clasts occurred after their fragmentation due to shear stress imparted by the overlying and still-moving lava flow, forming rounded juvenile clasts. Subsequent in situ quenching fragmentation of the lava flow produced clasts with platy to polyhedral shapes immediately after emplacement of the lava flow. Type-2 peperites laterally extend into the interior of featureless rhyolite as layers that decrease in thickness with increasing distance away from the flame zone. These layers exhibit horizontal textural variations, ranging from poorly sorted mixtures of ash- to block-sized angular juvenile clasts in the proximal zone, to closely packed polyhedral and tabular juvenile clasts with jigsaw-crack textures in the middle and distal zones. Type-2 peperite are inferred to have formed due to internal steam explosions that resulted from an expansion of heated pore water (leading to an increase in pore fluid pressure) that had been vertically injected into the interior of the rhyolite from the flame zone. The proximal zone, composed mainly of poorly sorted mixtures of juvenile clasts, represents the explosion sites. Juvenile clasts in the middle and distal zones are interpreted to have formed due to three separate processes: the development of fractures in the rhyolite during the internal steam explosions, injection of the host sediment through the fractures, and

  18. A pilot muon radiography to image the shallow conduit of the Stromboli volcano: results and future prospects

    Science.gov (United States)

    Miyamoto, Seigo; Tioukov, Valeri; Sirignano, Chiara; Bozza, Cristiano; Morishima, Kunihiro

    2017-04-01

    The test result of imaging the shallow part of the Stromboli crater zone by using cosmic-ray muons in 2012 and possible performance of the future muon observation will be presented. It is well known that the behavior of volcanic eruptions strongly depends on the shape of the conduit. Stromboli is one of the most known and studied active volcanoes in the world, nevertheless the details of its internal structure are not well defined yet. Geophysical exploration method which use high energy cosmic-ray muons and makes the density image of the object like X-ray radiography for the human body is called "muon radiography " or "muography". A pilot muography was done for the shallow part of Stromboli in 2012. We succeeded to clarify that there is a less density part at the North-East cone in the crater zone. It is considered that the stack of volcanic ashes. On the other hand, we also confirmed that the contamination of the physical background particles and they makes the noisy density image especially about 50 meter below from the top of the crater. In another observation, Nishiyama et al (2014) revealed the contents of background particles and the way to remove them were presented. They showed that the main contents of the background particles is low kinetic energy charged particles and also showed that it is possible to remove them by using multi-layerd muon film detector. We can plan the future muography observation to see the deeper part of the conduit( at least until 100 meter from the top of crater) by their backgroundless method. Therefore we estimated possible performance of the future observation by multi-layer muon films. The result suggests that we might get the image of shallow conduit from the surface to the depth of e.g. 55 meter with 20 meter spatial resolution or 100 meter with 27 meter resolution in case the density in the conduit is 0.0 g/cm3 and with 71 percent statistical confidence level.

  19. Convective heat transfer of nanofluid flow through conduits with different cross-sectional shapes

    Energy Technology Data Exchange (ETDEWEB)

    Salimpour, Mohammad Reza; Dehshiri-Parizi, Amir [Isfahan University of Technology, Isfahan (Iran, Islamic Republic of)

    2015-02-15

    This study investigates the laminar forced convective heat transfer of TiO{sub 2}/water nanofluids through conduits with different cross sections, experimentally. The effects of different parameters, such as cross-sectional shape, Reynolds number, and concentration of nanoparticles, on the enhanced heat transfer are examined by designing and assembling an experimental apparatus. Results show that adding a small amount of nanoparticles to the base fluid improves heat transfer behavior in conduits. A conduit with a circular cross section performs better than conduits with square and triangular cross sections. However, conduits with square and triangular cross sections exhibit more relative enhancements than a conduit with a circular cross section.

  20. Experimental observations of pressure oscillations and flow regimes in an analogue volcanic system

    Science.gov (United States)

    Lane, S.J.; Chouet, B.A.; Phillips, J.C.; Dawson, P.; Ryan, G.A.; Hurst, E.

    2001-01-01

    Gas-liquid flows, designed to be analogous to those in volcanic conduits, are generated in the laboratory using organic gas-gum rosin mixtures expanding in a vertically mounted tube. The expanding fluid shows a range of both flow and pressure oscillation behaviors. Weakly supersaturated source liquids produce a low Reynolds number flow with foam expanding from the top surface of a liquid that exhibits zero fluid velocity at the tube wall; i.e., the conventional "no-slip" boundary condition. Pressure oscillations, often with strong long-period characteristics and consistent with longitudinal and radial resonant oscillation modes, are detected in these fluids. Strongly supersaturated source liquids generate more energetic flows that display a number of flow regimes. These regimes include a static liquid source, viscous flow, detached flow (comprising gas-pockets-at-wall and foam-in-gas annular flow, therefore demonstrating strong radial heterogeneity), and a fully turbulent transonic fragmented or mist flow. Each of these flow regimes displays characteristic pressure oscillations that can be related to resonance of flow features or wall impact phenomena. The pressure oscillations are produced by the degassing processes without the need of elastic coupling to the confining medium or flow restrictors and valvelike features. The oscillatory behavior of the experimental flows is compared to seismoacoustic data from a range of volcanoes where resonant oscillation of the fluid within the conduit is also often invoked as controlling the observed oscillation frequencies. On the basis of the experimental data we postulate on the nature of seismic signals that may be measured during large-scale explosive activity. Copyright 2001 by the American Geophysical Union.

  1. Mantle and crustal processes in the magmatism of the Campania region: inferences from mineralogy, geochemistry, and Sr-Nd-O isotopes of young hybrid volcanics of the Ischia island (South Italy)

    Science.gov (United States)

    D'Antonio, Massimo; Tonarini, Sonia; Arienzo, Ilenia; Civetta, Lucia; Dallai, Luigi; Moretti, Roberto; Orsi, Giovanni; Andria, Mariachiara; Trecalli, Alberto

    2013-06-01

    Ischia, one active volcano of the Phlegraean Volcanic District, prone to very high risk, is dominated by a caldera formed 55 ka BP, followed by resurgence of the collapsed area. Over the past 3 ka, the activity extruded evolved potassic magmas; only a few low-energy explosive events were fed by less evolved magmas. A geochemical and Sr-Nd-O isotope investigation has been performed on minerals and glass from products of three of such eruptions, Molara, Vateliero, and Cava Nocelle (Ischia volcanism in the past. Detailed study on the most mafic magma has permitted to investigate its origin. The mantle sector below Ischia underwent subduction processes that modified its pristine chemical, isotopic, and redox conditions by addition of ≤1 % of sediment fluids/melts. Similar processes occurred from Southeast to Northwest along the Apennine compressive margin, with addition of up to 2.5 % of sediment-derived material. This is shown by volcanics with poorly variable, typical δ18O mantle values, and 87Sr/86Sr progressively increasing toward typical continental crust values. Multiple partial melting of this modified mantle generated distinct primary magmas that occasionally assimilated continental crust, acquiring more 18O than 87Sr. At Ischia, 7 % of Hercynian granodiorite assimilation produced isotopically distinct, K-basaltic to latitic magmas. A SW-NE regional tectonic structure gave these magmas coming from large depth the opportunity to mingle/mix with felsic magmas stagnating in shallower reservoirs, eventually triggering explosive eruptions.

  2. Design of barrier coatings on kink-resistant peripheral nerve conduits

    Directory of Open Access Journals (Sweden)

    Basak Acan Clements

    2016-02-01

    Full Text Available Here, we report on the design of braided peripheral nerve conduits with barrier coatings. Braiding of extruded polymer fibers generates nerve conduits with excellent mechanical properties, high flexibility, and significant kink-resistance. However, braiding also results in variable levels of porosity in the conduit wall, which can lead to the infiltration of fibrous tissue into the interior of the conduit. This problem can be controlled by the application of secondary barrier coatings. Using a critical size defect in a rat sciatic nerve model, the importance of controlling the porosity of the nerve conduit walls was explored. Braided conduits without barrier coatings allowed cellular infiltration that limited nerve recovery. Several types of secondary barrier coatings were tested in animal studies, including (1 electrospinning a layer of polymer fibers onto the surface of the conduit and (2 coating the conduit with a cross-linked hyaluronic acid-based hydrogel. Sixteen weeks after implantation, hyaluronic acid-coated conduits had higher axonal density, displayed higher muscle weight, and better electrophysiological signal recovery than uncoated conduits or conduits having an electrospun layer of polymer fibers. This study indicates that braiding is a promising method of fabrication to improve the mechanical properties of peripheral nerve conduits and demonstrates the need to control the porosity of the conduit wall to optimize functional nerve recovery.

  3. Design of barrier coatings on kink-resistant peripheral nerve conduits.

    Science.gov (United States)

    Clements, Basak Acan; Bushman, Jared; Murthy, N Sanjeeva; Ezra, Mindy; Pastore, Christopher M; Kohn, Joachim

    2016-01-01

    Here, we report on the design of braided peripheral nerve conduits with barrier coatings. Braiding of extruded polymer fibers generates nerve conduits with excellent mechanical properties, high flexibility, and significant kink-resistance. However, braiding also results in variable levels of porosity in the conduit wall, which can lead to the infiltration of fibrous tissue into the interior of the conduit. This problem can be controlled by the application of secondary barrier coatings. Using a critical size defect in a rat sciatic nerve model, the importance of controlling the porosity of the nerve conduit walls was explored. Braided conduits without barrier coatings allowed cellular infiltration that limited nerve recovery. Several types of secondary barrier coatings were tested in animal studies, including (1) electrospinning a layer of polymer fibers onto the surface of the conduit and (2) coating the conduit with a cross-linked hyaluronic acid-based hydrogel. Sixteen weeks after implantation, hyaluronic acid-coated conduits had higher axonal density, displayed higher muscle weight, and better electrophysiological signal recovery than uncoated conduits or conduits having an electrospun layer of polymer fibers. This study indicates that braiding is a promising method of fabrication to improve the mechanical properties of peripheral nerve conduits and demonstrates the need to control the porosity of the conduit wall to optimize functional nerve recovery.

  4. Anomalous diffusion of volcanic earthquakes

    CERN Document Server

    Abe, Sumiyoshi

    2015-01-01

    Volcanic seismicity at Mt. Etna is studied. It is found that the associated stochastic process exhibits a subdiffusive phenomenon. The jump probability distribution well obeys an exponential law, whereas the waiting-time distribution follows a power law in a wide range. Although these results would seem to suggest that the phenomenon could be described by temporally-fractional kinetic theory based on the viewpoint of continuous-time random walks, the exponent of the power-law waiting-time distribution actually lies outside of the range allowed in the theory. In addition, there exists the aging phenomenon in the event-time averaged mean squared displacement, in contrast to the picture of fractional Brownian motion. Comments are also made on possible relevances of random walks on fractals as well as nonlinear kinetics. Thus, problems of volcanic seismicity are highly challenging for science of complex systems.

  5. How Volcanism Controls Climate Change

    Science.gov (United States)

    Ward, P. L.

    2013-12-01

    Large explosive volcanoes eject megatons of sulfur dioxide into the lower stratosphere where it spreads around the world within months and is oxidized slowly to form a sulfuric-acid aerosol with particle sizes that grow large enough to reflect and scatter solar radiation, cooling Earth ~0.5C for up to 3 years. Explosive eruptions also deplete total column ozone ~6% causing up to 3C winter warming at mid-latitudes over continents. Global cooling predominates. Extrusive, basaltic volcanoes deplete ozone ~6% but do not eject much sulfur dioxide into the lower stratosphere, causing net global warming. Anthropogenic chlorofluorocarbons (CFCs) deplete ozone ~3% for up to a century while each volcanic eruption, even small ones, depletes ozone twice as much but for less than a decade through eruption of halogens and ensuing photochemical processes. The 2010 eruption of Eyjafjallajökull, the 2011 eruption of Grímsvötn, plus anthropogenic CFCs depleted ozone over Toronto Canada 14% in 2012, causing an unusually warm winter and drought. Total column ozone determines how much solar ultraviolet energy with wavelengths between 290 and 340 nanometers reaches Earth where it is absorbed most efficiently by the ocean. A 25% depletion of ozone increases the amount of this radiation reaching Earth by 1 W m-2 for overhead sun and 0.25 W m-2 for a solar zenith angle of 70 degrees. The tropopause is the boundary between the troposphere heated from below by a sun-warmed Earth and the stratosphere heated from above by the Sun through photodissociation primarily of oxygen and ozone. The mean annual height of the tropopause increased ~160 m between 1980 and 2004 at the same time that northern mid-latitude total column ozone was depleted by ~4%, the lower stratosphere cooled ~2C, the upper troposphere warmed ~0.1C, and mean surface temperatures in the northern hemisphere rose ~0.5C. Regional total ozone columns are observed to increase as rapidly as 20% within 5 hours with an associated 5

  6. Clinical use of nerve conduits in peripheral-nerve repair : Review of the literature

    NARCIS (Netherlands)

    Meek, MF; Coert, JH

    2002-01-01

    The use of nerve conduits has evolved from a previous experimental idea to a clinical reality over the last ten years. An overview of the literature on the clinical use of nerve conduits in peripheral-nerve repair is presented.

  7. Clinical use of nerve conduits in peripheral-nerve repair : Review of the literature

    NARCIS (Netherlands)

    Meek, MF; Coert, JH

    2002-01-01

    The use of nerve conduits has evolved from a previous experimental idea to a clinical reality over the last ten years. An overview of the literature on the clinical use of nerve conduits in peripheral-nerve repair is presented.

  8. Archaeological applications of laser-induced breakdown spectroscopy: an example from the Coso Volcanic Field, California, using advanced statistical signal processing analysis

    Energy Technology Data Exchange (ETDEWEB)

    Remus, Jeremiah J.; Gottfried, Jennifer L.; Harmon, Russell S.; Draucker, Anne; Baron, Dirk; Yohe, Robert

    2010-05-01

    Over the past quarter century, multielement chemical analysis has become a common means for attributing the provenance of archaeological materials. The Coso Volcanic Field (CVF) in California, USA, contains at least 38 high-silica rhyolite domes, many of which contain obsidian glass that has been quarried for tools by the indigenous population for more than 12,000 years. Artifacts made from CVF obsidian are found throughout the southwestern United States and geochemical sourcing of CVF obsidian has been an important tool in understanding prehistoric Native American trading patterns. Laser-induced breakdown spectroscopy (LIBS) is a simple atomic emission spectroscopic technique that has the potential for real-time man-portable chemical analysis in the field. Because LIBS is simultaneously sensitive to all elements, a single laser shot can be used to record the broadband emission spectra, which provides a ''chemical fingerprint'' of a material. Single-shot broadband LIBS spectra were collected using a commercial benchtop LIBS system for 27 obsidian samples from major sites across the CVF and four additional sites in California and western Nevada outside of CVF. Classification of the samples was performed using partial least-squares discriminant analysis (PLSDA), a common chemometric technique suitable for performing regression on high-dimensional data. Provenance identification for the obsidian samples was evaluated for three separate labeling frameworks. The first framework consisted of a binary classification problem to distinguish CVF samples from non-CVF samples. The second approach focused on the CVF samples with labels that corresponded to the eight separate Coso sites encompassed by the 27 samples. In the third analysis, non-CVF samples were excluded, and the remaining 27 CVF samples were labeled based on groupings defined from previous major and trace element chemical studies, which reduces the number of possible classes from eight to four

  9. Long-term outcomes following Medtronic Open Pivot valved conduit.

    Science.gov (United States)

    Naidoo, Rishendran; Pearse, Bronwyn; Tesar, Peter J; Yap, Su-Ann; Barnett, Adrian G; Fayers, Trevor

    2014-01-01

    Aortic root replacement is a complex procedure, though subsequent modifications of the original Bentall procedure have made surgery more reproducible. The study aim was to examine the outcomes of a modified Bentall procedure, using the Medtronic Open PivotTM valved conduit. Whilst short-term data on the conduit and long-term data on the valve itself are available, little is known of the long-term results with the valved conduit. Patients undergoing aortic root replacement between February 1999 and February 2010, using the Medtronic Open Pivot valved conduit were identified from the prospectively collected Cardiothoracic Register at The Prince Charles Hospital, Brisbane, Australia. All patients were followed up echocardiographically and clinically. The primary end-point was death, and a Cox proportional model was used to identify factors associated.with survival. Secondary end-points were valve-related morbidity (as defined by STS guidelines) and postoperative morbidity. Predictors of morbidity were identified using logistic regression. A total of 246 patients (mean age 50 years) was included in the study. The overall mortality was 12%, with actuarial 10-year survival 79% and a 10-year estimate of valve-related death of 0.04 (95% CI: 0.004, 0.07). Preoperative myocardial infarction (p = 0.004, HR 4.74), urgency of operation (p = 0.038, HR 2.8) and 10% incremental decreases in ejection fraction (p = 0.046, HR 0.69) were predictive of mortality. Survival was also affected by the valve gradients, with a unit increase in peak gradient reducing mortality (p = 0.021, HR 0.93). Valve-related morbidity occurred in 11 patients. Urgent surgery (p Medtronic Open Pivot valved conduit is a safe and durable option for aortic root replacement, and is associated with low morbidity and 10-year survival of 79%. However, further studies are required to determine the effect of valve gradient on survival.

  10. Volcanic Rocks and Features

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Volcanoes have contributed significantly to the formation of the surface of our planet. Volcanism produced the crust we live on and most of the air we breathe. The...

  11. Dual-Component Gelatinous Peptide/Reactive Oligomer Formulations as Conduit Material and Luminal Filler for Peripheral Nerve Regeneration.

    Science.gov (United States)

    Kohn-Polster, Caroline; Bhatnagar, Divya; Woloszyn, Derek J; Richtmyer, Matthew; Starke, Annett; Springwald, Alexandra H; Franz, Sandra; Schulz-Siegmund, Michaela; Kaplan, Hilton M; Kohn, Joachim; Hacker, Michael C

    2017-05-21

    Toward the next generation of nerve guidance conduits (NGCs), novel biomaterials and functionalization concepts are required to address clinical demands in peripheral nerve regeneration (PNR). As a biological polymer with bioactive motifs, gelatinous peptides are promising building blocks. In combination with an anhydride-containing oligomer, a dual-component hydrogel system (cGEL) was established. First, hollow cGEL tubes were fabricated by a continuous dosing and templating process. Conduits were characterized concerning their mechanical strength, in vitro and in vivo degradation and biocompatibility. Second, cGEL was reformulated as injectable shear thinning filler for established NGCs, here tyrosine-derived polycarbonate-based braided conduits. Thereby, the formulation contained the small molecule LM11A-31. The biofunctionalized cGEL filler was assessed regarding building block integration, mechanical properties, in vitro cytotoxicity, and growth permissive effects on human adipose tissue-derived stem cells. A positive in vitro evaluation motivated further application of the filler material in a sciatic nerve defect. Compared to the empty conduit and pristine cGEL, the functionalization performed superior, though the autologous nerve graft remains the gold standard. In conclusion, LM11A-31 functionalized cGEL filler with extracellular matrix (ECM)-like characteristics and specific biochemical cues holds great potential to support PNR.

  12. Dual-Component Gelatinous Peptide/Reactive Oligomer Formulations as Conduit Material and Luminal Filler for Peripheral Nerve Regeneration

    Directory of Open Access Journals (Sweden)

    Caroline Kohn-Polster

    2017-05-01

    Full Text Available Toward the next generation of nerve guidance conduits (NGCs, novel biomaterials and functionalization concepts are required to address clinical demands in peripheral nerve regeneration (PNR. As a biological polymer with bioactive motifs, gelatinous peptides are promising building blocks. In combination with an anhydride-containing oligomer, a dual-component hydrogel system (cGEL was established. First, hollow cGEL tubes were fabricated by a continuous dosing and templating process. Conduits were characterized concerning their mechanical strength, in vitro and in vivo degradation and biocompatibility. Second, cGEL was reformulated as injectable shear thinning filler for established NGCs, here tyrosine-derived polycarbonate-based braided conduits. Thereby, the formulation contained the small molecule LM11A-31. The biofunctionalized cGEL filler was assessed regarding building block integration, mechanical properties, in vitro cytotoxicity, and growth permissive effects on human adipose tissue-derived stem cells. A positive in vitro evaluation motivated further application of the filler material in a sciatic nerve defect. Compared to the empty conduit and pristine cGEL, the functionalization performed superior, though the autologous nerve graft remains the gold standard. In conclusion, LM11A-31 functionalized cGEL filler with extracellular matrix (ECM-like characteristics and specific biochemical cues holds great potential to support PNR.

  13. Volcanic Plume Measurements with UAV (Invited)

    Science.gov (United States)

    Shinohara, H.; Kaneko, T.; Ohminato, T.

    2013-12-01

    volcano operated by ERI, Tokyo University. In all cases, we could estimated volcanic gas compositions, such as CO2/SO2 ratios, but also found out that it is necessary to improve the techniques to avoid the contamination of the exhaust gases and to approach more concentrated part of the plume. It was also revealed that the aerial measurements have an advantage of the stable background. The error of the volcanic gas composition estimates are largely due to the large fluctuation of the atmospheric H2O and CO2 concentrations near the ground. The stable atmospheric background obtained by the UAV measurements enables accurate estimate of the volcanic gas compositions. One of the most successful measurements was that on May 18, 2011 at Shinomoedake, Kirishima volcano during repeating Vulcanian eruption stage. The major component composition was obtained as H2O=97, CO2=1.5, SO2=0.2, H2S=0.24, H2=0.006 mol%; the high CO2 contents suggests relatively deep source of the magma degassing and the apparent equilibrium temperature obtained as 400°C indicates that the gas was cooled during ascent to the surface. The volcanic plume measurement with UAV will become an important tool for the volcano monitoring that provides important information to understand eruption processes.

  14. Using U-series and beryllium isotopes to reveal the occurrence and relative timing of crustal and mantle processes in the Southern Volcanic Zone of Chile

    Science.gov (United States)

    Cooper, L. B.; Reubi, O.; Dungan, M. A.; Bourdon, B.; Langmuir, C. H.; Turner, S. J.; Schaefer, J. M.

    2012-12-01

    Magmas erupted from subduction zone volcanoes represent the end products of multiple magmatic processes occurring in the asthenospheric mantle wedge and overlying lithosphere (i.e., fluid addition, melting, assimilation, and crystal fractionation). To resolve the contributions of diverse processes and components, and the relative timing of these events, we have determined U-series activities (U-Th-Ra-Pa) for 60 and 10Be compositions for 20 historic or very young lavas carefully chosen on the basis of major and trace element analyses of 625 samples from six volcanoes in the Andean Southern Volcanic Zone of Chile (37.6-41.1°S: Nevados de Chillán, Antuco, Llaima, Lonquimay, Villarrica, and Osorno). Our dataset demonstrates that each of these volcanoes reflects a unique combination and sequence of magmatic processes that are only revealed through analysis of multiple samples spanning the extent of intra-volcano and intra-eruption chemical variation. Sigmarsson et al. (1990; 2002) identified a regional trend using U-series and Be from mostly single samples, which they interpreted to represent along-strike variations in the flux of slab-derived fluids into the wedge [from 230Th-excess plus 226Ra-deficit plus low 10Be/9Be at Chillán towards progressively higher 238U- and Ra-excesses and 10Be/9Be at Villarrica and Osorno]. These data fall within the much broader array defined by our results, but we infer the operation of assimilation (e.g., Llaima; Reubi et al., 2011) and aging of subduction zone components of variable compositions and proportions in the mantle prior to partial melting as important factors in generating the highly individualized and complex U-series systematics observed at each of these six volcanoes. All of the volcanoes exhibit evidence of assimilation, with the exception of Lonquimay which has undergone mostly closed-system fractional crystallization. At Llaima and Chillán the assimilant is crustal. At Villarica, flux-related melts that dominate in

  15. Monitoring of stage and velocity, for computation of discharge in the Summit Conduit near Summit, Illinois, 2010-2012

    Science.gov (United States)

    Johnson, Kevin K.; Goodwin, Greg E.

    2013-01-01

    Lake Michigan diversion accounting is the process used by the U. S. Army Corps of Engineers to quantify the amount of water that is diverted from the Lake Michigan watershed into the Illinois and Mississippi River Basins. A network of streamgages within the Chicago area waterway system monitor tributary river flows and the major river flow on the Chicago Sanitary and Ship Canal near Lemont as one of the instrumental tools used for Lake Michigan diversion accounting. The mean annual discharges recorded by these streamgages are used as additions or deductions to the mean annual discharge recorded by the main stream gaging station currently used in the Lake Michigan diversion accounting process, which is the Chicago Sanitary and Ship Canal near Lemont, Illinois (station number 05536890). A new stream gaging station, Summit Conduit near Summit, Illinois (station number 414757087490401), was installed on September 23, 2010, for the purpose of monitoring stage, velocity, and discharge through the Summit Conduit for the U.S. Army Corps of Engineers in accordance with Lake Michigan diversion accounting. Summit Conduit conveys flow from a small part of the lower Des Plaines River watershed underneath the Des Plaines River directly into the Chicago Sanitary and Ship Canal. Because the Summit Conduit discharges into the Chicago Sanitary and Ship Canal upstream from the stream gaging station at Lemont, Illinois, but does not contain flow diverted from the Lake Michigan watershed, it is considered a flow deduction to the discharge measured by the Lemont stream gaging station in the Lake Michigan diversion accounting process. This report offers a technical summary of the techniques and methods used for the collection and computation of the stage, velocity, and discharge data at the Summit Conduit near Summit, Illinois stream gaging station for the 2011 and 2012 Water Years. The stream gaging station Summit Conduit near Summit, Illinois (station number 414757087490401) is an

  16. Petrogenesis of Volcanic Rocks in the Khabr-Marvast Tectonized Ophiolite: Evidence for Subduction Processes in the South-Western Margin of Central Iranian Microcontinent

    Institute of Scientific and Technical Information of China (English)

    Azam SOLTANMOHAMMADI; Mohammad RAHGOSHAY; Morteza KHALATBARI-JAFARI

    2009-01-01

    The Late Cretaceous Khabr-Marvast tectonized ophiolite is located in the middle part of the Nain-Baft ophiolite belt, at the south-western edge of the central Iranian microcontinent. Although all the volcanic rocks in the study area indicate subduction-related magmatism (e.g. high LILE (large ion lithophile elements)/ HFSE (high field strenght elements) ratios and negative anomalies in Nb and Ta), geological and geochemical data clearly distinguish two distinct groups of volcanic rocks in the tectonized association: (1) group 1 is comprised of hyaloclustic breccias, basaltic pillow iavas, and andesite sheet flows. These rocks represent the Nain-Baft oceanic crust; and (2) group 2 is alkaline iavas from the top section of the ophiolite suite. These lavas show shoshonite affinity, but do not support the propensity of ophiolite.

  17. Hemiresective reconstruction of a redundant ileal conduit with severe bilateral ileal conduit-ureteral re fl ux.

    Science.gov (United States)

    Fujimura, Tetsuya; Minowada, Shigeru; Kishi, Hiroichi; Hamasaki, Kimihisa; Saito, Kiyoshi; Kitamura, Tadaichi

    2005-10-01

    A 58-year-old man was referred to our hospital with high fever and anuria. Since undergoing a total pelvic exenteration due to bladder-invasive sigmoid colon cancer, urinary tract infections had frequently occurred. We treated with the construction of a bilateral percutaneous nephrostomy (PCN), and chemotherapy. Although we replaced the PCN with a single J ureteral catheter after an improvement of infection, urinary infection recurred because of an obstruction of the catheter. Urological examinations showed that an ileal conduit-ureteral reflux caused by kinking of the ileal loop was the reason why frequent pyelonephritis occurred. We decided to resect the proximal segment to improve conduit-ureteral reflux for the resistant pyelonephritis. After the surgery, the excretory urogram showed improvement and the urinary retention at the ileal conduit disappeared. Three years after the operation, renal function has been stable without episodes of pyelonephritis. Here we report a case of open repair surgery of an ileal conduit in a patient with severe urinary infection.

  18. Results and analysis of the hot-spot temperature experiment for a cable-in-conduit conductor with thick conduit

    Science.gov (United States)

    Sedlak, Kamil; Bruzzone, Pierluigi

    2015-12-01

    In the design of future DEMO fusion reactor a long time constant (∼23 s) is required for an emergency current dump in the toroidal field (TF) coils, e.g. in case of a quench detection. This requirement is driven mainly by imposing a limit on forces on mechanical structures, namely on the vacuum vessel. As a consequence, the superconducting cable-in-conduit conductors (CICC) of the TF coil have to withstand heat dissipation lasting tens of seconds at the section where the quench started. During that time, the heat will be partially absorbed by the (massive) steel conduit and electrical insulation, thus reducing the hot-spot temperature estimated strictly from the enthalpy of the strand bundle. A dedicated experiment has been set up at CRPP to investigate the radial heat propagation and the hot-spot temperature in a CICC with a 10 mm thick steel conduit and a 2 mm thick glass epoxy outer electrical insulation. The medium size, ∅ = 18 mm, NbTi CICC was powered by the operating current of up to 10 kA. The temperature profile was monitored by 10 temperature sensors. The current dump conditions, namely the decay time constant and the quench detection delay, were varied. The experimental results show that the thick conduit significantly contributes to the overall enthalpy balance, and consequently reduces the amount of copper required for the quench protection in superconducting cables for fusion reactors.

  19. Submarine seismic monitoring of El Hierro volcanic eruption with a 3C-geophone string: applying new acquisition and data processing techniques to volcano monitoring

    Science.gov (United States)

    Jurado, Maria Jose; Ripepe, Maurizio; Lopez, Carmen; Blanco, Maria Jose; Crespo, Jose

    2015-04-01

    A submarine volcanic eruption took place near the southernmost emerged land of the El Hierro Island (Canary Islands, Spain), from October 2011 to February 2012. The Instituto Geografico Nacional (IGN) seismic stations network evidenced seismic unrest since July 2011 and was a reference also to follow the evolution of the seismic activity associated with the volcanic eruption. Right after the eruption onset, in October 2011 a geophone string was deployed by the CSIC-IGN to monitor seismic activity. Monitoring with the seismic array continued till May 2012. The array was installed less than 2 km away from the new vol¬cano, next to La Restinga village shore in the harbor from 6 to 12m deep into the water. Our purpose was to record seismic activity related to the volcanic activity, continuously and with special interest on high frequency events. The seismic array was endowed with 8, high frequency, 3 component, 250 Hz, geophone cable string with a separation of 6 m between them. Each geophone consists on a 3-component module based on 3 orthogonal independent sensors that measures ground velocity. Some of the geophones were placed directly on the seabed, some were buried. Due to different factors, as the irregular characteristics of the seafloor. The data was recorded on the surface with a seismometer and stored on a laptop computer. We show how acoustic data collected underwater show a great correlation with the seismic data recorded on land. Finally we compare our data analysis results with the observed sea surface activity (ash and lava emission and degassing). This evidence is disclosing new and innovative tecniques on monitoring submarine volcanic activity. Reference Instituto Geográfico Nacional (IGN), "Serie El Hierro." Internet: http://www.ign.es/ign/resources /volcanologia/HIERRO.html [May, 17. 2013

  20. Eruption processes and deposit characteristics at the monogenetic Mt. Gambier Volcanic Complex, SE Australia: implications for alternating magmatic and phreatomagmatic activity

    Science.gov (United States)

    van Otterloo, Jozua; Cas, Raymond A. F.; Sheard, Malcolm J.

    2013-08-01

    The ˜5 ka Mt. Gambier Volcanic Complex in the Newer Volcanics Province, Australia is an extremely complex monogenetic, volcanic system that preserves at least 14 eruption points aligned along a fissure system. The complex stratigraphy can be subdivided into six main facies that record alternations between magmatic and phreatomagmatic eruption styles in a random manner. The facies are (1) coherent to vesicular fragmental alkali basalt (effusive/Hawaiian spatter and lava flows); (2) massive scoriaceous fine lapilli with coarse ash (Strombolian fallout); (3) bedded scoriaceous fine lapilli tuff (violent Strombolian fallout); (4) thin-medium bedded, undulating very fine lapilli in coarse ash (dry phreatomagmatic surge-modified fallout); (5) palagonite-altered, cross-bedded, medium lapilli to fine ash (wet phreatomagmatic base surges); and (6) massive, palagonite-altered, very poorly sorted tuff breccia and lapilli tuff (phreato-Vulcanian pyroclastic flows). Since most deposits are lithified, to quantify the grain size distributions (GSDs), image analysis was performed. The facies are distinct based on their GSDs and the fine ash to coarse+fine ash ratios. These provide insights into the fragmentation intensities and water-magma interaction efficiencies for each facies. The eruption chronology indicates a random spatial and temporal sequence of occurrence of eruption styles, except for a "magmatic horizon" of effusive activity occurring at both ends of the volcanic complex simultaneously. The eruption foci are located along NW-SE trending lineaments, indicating that the complex was fed by multiple dykes following the subsurface structures related to the Tartwaup Fault System. Possible factors causing vent migration along these dykes and changes in eruption styles include differences in magma ascent rates, viscosity, crystallinity, degassing and magma discharge rate, as well as hydrological parameters.

  1. 30 CFR 75.700 - Grounding metallic sheaths, armors, and conduits enclosing power conductors.

    Science.gov (United States)

    2010-07-01

    ... conduits enclosing power conductors. 75.700 Section 75.700 Mineral Resources MINE SAFETY AND HEALTH... Grounding § 75.700 Grounding metallic sheaths, armors, and conduits enclosing power conductors. All metallic sheaths, armors, and conduits enclosing power conductors shall be electrically continuous throughout...

  2. 30 CFR 77.700 - Grounding metallic sheaths, armors, and conduits enclosing power conductors.

    Science.gov (United States)

    2010-07-01

    ... conduits enclosing power conductors. 77.700 Section 77.700 Mineral Resources MINE SAFETY AND HEALTH..., and conduits enclosing power conductors. Metallic sheaths, armors, and conduits enclosing power conductors shall be electrically continuous throughout and shall be grounded by methods approved by...

  3. POROSITY OF THE WALL OF A NEUROLAC (R) NERVE CONDUIT HAMPERS NERVE REGENERATION

    NARCIS (Netherlands)

    Meek, Marcel F.; Den Dunnen, Wilfred F. A.

    2009-01-01

    One way to improve nerve regeneration and bridge longer nerve gaps may be the use of semipermeable/porous conduits. With porosity less biomaterial is used for the nerve conduit. We evaluated the short-term effects of porous Neurolac (R) nerve conduits for in vivo peripheral nerve regeneration. In 10

  4. Volcanic mercury in Pinus canariensis

    Science.gov (United States)

    Rodríguez Martín, José Antonio; Nanos, Nikos; Miranda, José Carlos; Carbonell, Gregoria; Gil, Luis

    2013-08-01

    Mercury (Hg) is a toxic element that is emitted to the atmosphere by both human activities and natural processes. Volcanic emissions are considered a natural source of mercury in the environment. In some cases, tree ring records taken close to volcanoes and their relation to volcanic activity over time are contradictory. In 1949, the Hoyo Negro volcano (La Palma-Canary Islands) produced significant pyroclastic flows that damaged the nearby stand of Pinus canariensis. Recently, 60 years after the eruption, we assessed mercury concentrations in the stem of a pine which survived volcano formation, located at a distance of 50 m from the crater. We show that Hg content in a wound caused by pyroclastic impacts (22.3 μg kg-1) is an order of magnitude higher than the Hg concentrations measured in the xylem before and after the eruption (2.3 μg kg-1). Thus, mercury emissions originating from the eruption remained only as a mark—in pyroclastic wounds—and can be considered a sporadic and very high mercury input that did not affect the overall Hg input in the xylem. In addition, mercury contents recorded in the phloem (9.5 μg kg-1) and bark (6.0 μg kg-1) suggest that mercury shifts towards non-living tissues of the pine, an aspect that can be related to detoxification in volcanism-adapted species.

  5. Morphometry of Concepcion Bank: Evidence of Geological and Biological Processes on a Large Volcanic Seamount of the Canary Islands Seamount Province.

    Science.gov (United States)

    Rivera, Jesus; Canals, Miquel; Lastras, Galderic; Hermida, Nuria; Amblas, David; Arrese, Beatriz; Martín-Sosa, Pablo; Acosta, Juan

    2016-01-01

    Concepcion Bank is the largest seamount in the Canary Islands Seamount Province (CISP), an oceanic area off NW Africa including 16 main seamounts, the Canaries archipelago and the Selvagens subarchipelago. The Bank is located 90 km northeast of Lanzarote Island and has been identified as a candidate Marine Protected Area (MPA) to be included in the Natura 2000 network. A compilation of complementary datasets consisting of multibeam bathymetry, TOPAS seismic reflection profiles, side scan sonar sonographs, Remotely Operated Vehicle video records and seafloor samples allowed describing in detail and ground truthing the submarine landforms and bioconstructions exhibited by the bank. The Concepcion Bank presently rises up to 2,433 m above the adjacent seafloor and exhibits two main domains: an extensive summit plateau and steep flanks. The sub-round summit plateau is 50km by 45 km and ranges from 158 to 1,485 m depth. The steep flanks that bound it descend to depths ranging between 1,700 and 2,500 m and define a seamount base that is 66km by 53 km. This morphology is the result of constructive and erosive processes involving different time scales, volumes of material and rates of change. The volcanic emplacement phase probably lasted 25-30 million years and was likely responsible for most of the 2,730 km3 of material that presently form the seamount. Subsequently, marine abrasion and, possibly, subaerial erosion modulated by global sea level oscillations, levelled the formerly emerging seamount summit plateau, in particular its shallower (<400 m), flatter (<0.5°) eastern half. Subsidence associated to the crustal cooling that followed the emplacement phase further contributed the current depth range of the seamount. The deeper and steeper (2.3°) western half of Concepcion Bank may result from tectonic tilting normal to a NNE-SSW fracture line. This fracture may still be expressed on the seafloor surface at some scarps detected on the seamount's summit. Sediment waves

  6. Morphometry of Concepcion Bank: Evidence of Geological and Biological Processes on a Large Volcanic Seamount of the Canary Islands Seamount Province

    Science.gov (United States)

    Canals, Miquel; Lastras, Galderic; Hermida, Nuria; Amblas, David; Arrese, Beatriz; Martín-Sosa, Pablo; Acosta, Juan

    2016-01-01

    Concepcion Bank is the largest seamount in the Canary Islands Seamount Province (CISP), an oceanic area off NW Africa including 16 main seamounts, the Canaries archipelago and the Selvagens subarchipelago. The Bank is located 90 km northeast of Lanzarote Island and has been identified as a candidate Marine Protected Area (MPA) to be included in the Natura 2000 network. A compilation of complementary datasets consisting of multibeam bathymetry, TOPAS seismic reflection profiles, side scan sonar sonographs, Remotely Operated Vehicle video records and seafloor samples allowed describing in detail and ground truthing the submarine landforms and bioconstructions exhibited by the bank. The Concepcion Bank presently rises up to 2,433 m above the adjacent seafloor and exhibits two main domains: an extensive summit plateau and steep flanks. The sub-round summit plateau is 50km by 45 km and ranges from 158 to 1,485 m depth. The steep flanks that bound it descend to depths ranging between 1,700 and 2,500 m and define a seamount base that is 66km by 53 km. This morphology is the result of constructive and erosive processes involving different time scales, volumes of material and rates of change. The volcanic emplacement phase probably lasted 25–30 million years and was likely responsible for most of the 2,730 km3 of material that presently form the seamount. Subsequently, marine abrasion and, possibly, subaerial erosion modulated by global sea level oscillations, levelled the formerly emerging seamount summit plateau, in particular its shallower (<400 m), flatter (<0.5°) eastern half. Subsidence associated to the crustal cooling that followed the emplacement phase further contributed the current depth range of the seamount. The deeper and steeper (2.3°) western half of Concepcion Bank may result from tectonic tilting normal to a NNE-SSW fracture line. This fracture may still be expressed on the seafloor surface at some scarps detected on the seamount’s summit. Sediment

  7. Raton-Clayton Volcanic Field magmatism in the context of the Jemez Lineament

    Science.gov (United States)

    Schrader, C. M.; Pontbriand, A.

    2013-12-01

    The Raton-Clayton Volcanic Field (RCVF) was active from 9 Ma to approximately 50 Ka and stretches from Raton, New Mexico in the west to Clayton, New Mexico in the east. The field occurs in the Great Plains at the northeastern end of the Jemez Lineament, a major crustal feature and focus of volcanism that extends southwest to the Colorado Plateau in Arizona and encompasses five other major volcanic fields. Jemez Lineament magmatism is temporally related to Rio Grande Rift magmatism, though it extends NE and SW from the rift itself, and it has been suggested that it represents an ancient crustal suture that serves as a conduit for magmatism occurring beneath the larger region of north and central New Mexico (Magnani et al., 2004, GEOL SOC AM BULL, 116:7/8, pp. 1-6). This study extends our work into the RCVF from prior and ongoing work in the Mount Taylor Volcanic Field, where we identified different mantle sources with varying degrees of subduction alteration and we determined some of the crustal processes that contribute to the diversity of magma chemistry and eruptive styles there (e.g., AGU Fall Meeting, abst. #V43D-2884 and #V43D-2883). In the RCVF, we are analyzing multiple phases by electron microprobe and plagioclase phenocrysts and glomerocrysts by LA-ICPMS for Sr isotopes and trace elements. We are undertaking this investigation with the following goals: (1) to evaluate previous magma mixing and crustal assimilation models for Sierra Grande andesites (Zhu, 1995, unpublished Ph.D. dissertation, Rice University; Hesse, 1999, unpublished M.S. thesis, Northern Arizona University); (2) to evaluate subduction-modified mantle as the source for RCVF basanites (specifically those at Little Grande); and (3) to assess the possible role of deep crustal cumulates in buffering transitional basalts. In the larger context, these data will be used to evaluate the varying degree of subduction-modification and the effect of crustal thickness on magmatism along the Jemez

  8. Volcanism and associated hazards: the Andean perspective

    Directory of Open Access Journals (Sweden)

    R. I. Tilling

    2009-12-01

    Full Text Available Andean volcanism occurs within the Andean Volcanic Arc (AVA, which is the product of subduction of the Nazca Plate and Antarctica Plates beneath the South America Plate. The AVA is Earth's longest but discontinuous continental-margin volcanic arc, which consists of four distinct segments: Northern Volcanic Zone, Central Volcanic Zone, Southern Volcanic Zone, and Austral Volcanic Zone. These segments are separated by volcanically inactive gaps that are inferred to indicate regions where the dips of the subducting plates are too shallow to favor the magma generation needed to sustain volcanism. The Andes host more volcanoes that have been active during the Holocene (past 10 000 years than any other volcanic region in the world, as well as giant caldera systems that have produced 6 of the 47 largest explosive eruptions (so-called "super eruptions" recognized worldwide that have occurred from the Ordovician to the Pleistocene.

    The Andean region's most powerful historical explosive eruption occurred in 1600 at Huaynaputina Volcano (Peru. The impacts of this event, whose eruptive volume exceeded 11 km3, were widespread, with distal ashfall reported at distances >1000 km away. Despite the huge size of the Huaynaputina eruption, human fatalities from hazardous processes (pyroclastic flows, ashfalls, volcanogenic earthquakes, and lahars were comparatively small owing to the low population density at the time. In contrast, lahars generated by a much smaller eruption (<0.05 km3 in 1985 of Nevado del Ruiz (Colombia killed about 25 000 people – the worst volcanic disaster in the Andean region as well as the second worst in the world in the 20th century. The Ruiz tragedy has been attributed largely to ineffective communications of hazards information and indecisiveness by government officials, rather than any major deficiencies in scientific data. Ruiz's disastrous outcome, however, together with responses to subsequent

  9. Crustal and tectonic controls on large-explosive volcanic eruptions

    Science.gov (United States)

    Sheldrake, Tom; Caricchi, Luca

    2017-04-01

    Quantifying the frequency-Magnitude (f-M) relationship for volcanic eruptions is important to estimate volcanic hazard. Furthermore, understanding how this relationship varies between different groups of volcanoes can provide insights into the processes that control the size and rate of volcanic events. Using a Bayesian framework, which allows us to conceptualise the volcanic record as a series of individual and unique time series, associated by a common group behaviour, we identify variations in the size and rate of volcanism in different volcanic arcs. These variations in behaviour are linked to key parameters that include the motion of subduction, rate of subduction, age of the slab and thickness of the crust. The effects of these parameters on volcanism are interpreted in terms of variations in mantle productivity and the thermal efficiency of magma transfer in arc crustal systems. Understanding the link between subduction architecture, heat content of magmatic systems, and volcanic activity will serve to improve our capacity to quantify volcanic hazard in regions with limited geological and historical records of volcanic activity.

  10. Neogene volcanism in Gutai Mts. (Eastern Carpathains: a review

    Directory of Open Access Journals (Sweden)

    Marinel Kovacs

    2003-04-01

    Full Text Available Two types of volcanism developed in Gutâi Mts. (inner volcanic chain of Eastern Carpathians: a felsic, extensional/“back-arc” type and an intermediate, arc type. The felsic volcanism of explosive origin, consisting of caldera-related rhyolitic ignimbrites and resedimented volcaniclastics, had taken place during Early-Middle Badenian and Early Sarmatian. The intermediate volcanism, consisting of extrusive (effusive and explosive and intrusive activity, had developed during Sarmatian and Pannonian (13.4-7.0 Ma. It is represented by typical calc-alkaline series, from basalts to rhyolites. Lava flows of basaltic andesites and andesites are predominant, often emplaced in subaqueous environment. Extrusive domes, mainly composed of dacites, are associated to the andesitic volcanic structures. The intermediate volcanism, consisting of extrusive (effusive and explosive and intrusive activity, had developed during Sarmatian and Pannonian (13.4-7.0 Ma. It is represented by typical calc-alkaline series, from basalts to rhyolites. Lava flows of basaltic andesites and andesites are predominant, often emplaced in subaqueous environment. Extrusive domes, mainly composed of dacites, are associated to the andesitic volcanic structures. The geochemical study on the volcanic rocks shows the calc-alkaline character of both felsic and intermediate volcanism and typical subduction zones geochemical signatures for the intermediate one. The felsic volcanism shows affinities with subduction-related rocks as well. The main petrogenetic process in Gutâi Mts. was crustal assimilation, strongly constrained by trace element and isotope geochemistry.

  11. Global volcanic emissions: budgets, plume chemistry and impacts

    Science.gov (United States)

    Mather, T. A.

    2012-12-01

    Over the past few decades our understanding of global volcanic degassing budgets, plume chemistry and the impacts of volcanic emissions on our atmosphere and environment has been revolutionized. Global volcanic emissions budgets are needed if we are to make effective use of regional and global atmospheric models in order to understand the consequences of volcanic degassing on global environmental evolution. Traditionally volcanic SO2 budgets have been the best constrained but recent efforts have seen improvements in the quantification of the budgets of other environmentally important chemical species such as CO2, the halogens (including Br and I) and trace metals (including measurements relevant to trace metal atmospheric lifetimes and bioavailability). Recent measurements of reactive trace gas species in volcanic plumes have offered intriguing hints at the chemistry occurring in the hot environment at volcanic vents and during electrical discharges in ash-rich volcanic plumes. These reactive trace species have important consequences for gas plume chemistry and impacts, for example, in terms of the global fixed nitrogen budget, volcanically induced ozone destruction and particle fluxes to the atmosphere. Volcanically initiated atmospheric chemistry was likely to have been particularly important before biological (and latterly anthropogenic) processes started to dominate many geochemical cycles, with important consequences in terms of the evolution of the nitrogen cycle and the role of particles in modulating the Earth's climate. There are still many challenges and open questions to be addressed in this fascinating area of science.

  12. Magma evolution and ascent at the Craters of the Moon and neighboring volcanic fields, southern Idaho, USA: implications for the evolution of polygenetic and monogenetic volcanic fields

    Science.gov (United States)

    Putirka, Keith D.; Kuntz, Mel A.; Unruh, Daniel M.; Vaid, Nitin

    2009-01-01

    The evolution of polygenetic and monogenetic volcanic fields must reflect differences in magma processing during ascent. To assess their evolution we use thermobarometry and geochemistry to evaluate ascent paths for neighboring, nearly coeval volcanic fields in the Snake River Plain, in south-central Idaho, derived from (1) dominantly Holocene polygenetic evolved lavas from the Craters of the Moon lava field (COME) and (2) Quaternary non-evolved, olivine tholeiites (NEOT) from nearby monogenetic volcanic fields. These data show that NEOT have high magmatic temperatures (1205 + or - 27 degrees C) and a narrow temperature range (50 degrees C). Prolonged storage of COME magmas allows them to evolve to higher 87Sr/86Sr and SiO2, and lower MgO and 143Nd/144Nd. Most importantly, ascent paths control evolution: NEOT often erupt near the axis of the plain where high-flux (Yellowstone-related), pre-Holocene magmatic activity replaces granitic middle crust with basaltic sills, resulting in a net increase in NEOT magma buoyancy. COME flows erupt off-axis, where felsic crustal lithologies sometimes remain intact, providing a barrier to ascent and a source for crustal contamination. A three-stage ascent process explains the entire range of erupted compositions. Stage 1 (40-20 km): picrites are transported to the middle crust, undergoing partial crystallization of olivine + or - clinopyroxene. COME magmas pass through unarmored conduits and assimilate 1% or less of ancient gabbroic crust having high Sr and 87Sr/86Sr and low SiO2. Stage 2 (20-10 km): magmas are stored within the middle crust, and evolve to moderate MgO (10%). NEOT magmas, reaching 10% MgO, are positively buoyant and migrate through the middle crust. COME magmas remain negatively buoyant and so crystallize further and assimilate middle crust. Stage 3 (15-0 km): final ascent and eruption occurs when volatile contents, increased by differentiation, are sufficient (1-2 wt % H2O) to provide magma buoyancy through the

  13. 80-Myr history of buoyancy and volcanic fluxes along the trails of the Walvis and St. Helena hotspots (South Atlantic)

    Science.gov (United States)

    Vidal, V.; Adam, C.; Escartin, J.

    2007-12-01

    Walvis and St.~Helena are the only long-lived hotspot chains in the South Atlantic. Therefore, their characterization is important to constrain the processes associated with mantle plume formation, their temporal evolution, and the interaction with plate and mantle dynamics in the region. We study the temporal evolution of plume buoyancy and magma production rate along both hotspot chains, which are constrained from the swell and volume of volcanic materials emplaced along the chain. The regional depth anomaly is calculated by correcting the 2' bathymetry grid of Smith & Sandwell (1997) for thermal subsidence and sediment loading. We separate the topography associated with volcanism and the swell surrounding the hotspot chains using the MiFil filtering method (Adam et al., 2005). We then estimate the temporal variations associated with both parameters by computing volumes along the hotspot tracks. Neither Walvis nor St.~Helena show a 'classical' hotspot behavior. We find that two plumes are at the origin of the St.~Helena chain. This study also shows a swell associated with the Circe seamount, supporting the existence of a hotspot NW of the St.~Helena trail. The variation in swell and volcanic fluxes suggests temporal variability in the plume behavior at time scales of 10-20~m.y. and 5~m.y., which may be related to oscillations and instabilities of the plume conduit, respectively. Cumulative fluxes in the area are largest for Walvis and weakest for Circe, and all are significantly lower than that reported for the Hawai'i hotspot.

  14. Using Uranium-series isotopes to understand processes of rapid soil formation in tropical volcanic settings: an example from Basse-Terre, French Guadeloupe

    Science.gov (United States)

    Ma, Lin

    2015-04-01

    Lin Ma1, Yvette Pereyra1, Peter B Sak2, Jerome Gaillardet3, Heather L Buss4 and Susan L Brantley5, (1) University of Texas at El Paso, El Paso, TX, United States, (2) Dickinson College, Carlisle, PA, United States, (3) Institute de Physique d Globe Paris, Paris, France, (4) University of Bristol, Bristol, United Kingdom, (5) Pennsylvania State University Main Campus, University Park, PA, United States Uranium-series isotopes fractionate during chemical weathering and their activity ratios can be used to determine timescales and rates of soil formation. Such soil formation rates provide important information to understand processes related to rapid soil formation in tropical volcanic settings, especially with respect to their fertility and erosion. Recent studies also highlighted the use of U-series isotopes to trace and quantify atmospheric inputs to surface soils. Such a process is particularly important in providing mineral nutrients to ecosystems in highly depleted soil systems such as the tropical soils. Here, we report U-series isotope compositions in thick soil profiles (>10 m) developed on andesitic pyroclastic flows in Basse-Terre Island of French Guadeloupe. Field observations have shown heterogeneity in color and texture in these thick profiles. However, major element chemistry and mineralogy show some general depth trends. The main minerals present throughout the soil profile are halloysite and gibbsite. Chemically immobile elements such as Al, Fe, and Ti show a depletion profile relative to Th while elements such as K, Mn, and Si show a partial depletion profile at depth. Mobile elements such as Ca, Mg, and Sr have undergone intensive weathering at depths, and an addition profile near the surface, most likely related to atmospheric inputs. (238U/232Th) activity ratios in one soil profile from the Brad David watershed in this study ranged from 0.374 to 1.696, while the (230Th/232Th) ratios ranged from 0.367 to 1.701. A decrease of (238U/232Th) in the

  15. The Temporal and Spatial Association of Faulting and Volcanism in the Cerros del Rio Volcanic Field - Rio Grande Rift, USA

    Science.gov (United States)

    Thompson, R. A.; Hudson, M. R.; Minor, S. A.; McIntosh, W. C.; Miggins, D. P.; Grauch, V.

    2008-12-01

    The Plio-Pleistocene Cerros del Rio volcanic field (CdRVF) in northern New Mexico is one of the largest ( greater than 700 square kilometers) predominantly basaltic and andesitic volcanic centers of the Rio Grande rift; it records the late-stage, volcano-tectonic evolution of the SW part of the Espanola Basin. The CdRVF reflects both regional proclivity toward Pliocene basaltic volcanism following protracted Neogene extensional tectonism and localized eruptive response to migration of basin- bounding faults. Approximately 180 cubic kilometers of flat lying to gently dipping basalt, andesite, and minor dacite lava flows and pyroclastic deposits of the CdRVF were erupted from more than 50 exposed vents between 2.8 Ma and 1.14 Ma. Subsurface interpretations of drill hole data and incised canyon exposures of the Rio Grande show that volcanic deposits are interbedded with Santa Fe Group sediments deposited in actively subsiding sub-basins of the southernmost Espanola Basin. Major basin-bounding faults in this area strike north to northwest, dip basinward, and have mostly dip-slip and subordinate strike-slip displacement. Although major basin-bounding faults were active prior to the onset of volcanism in the CdRVF, protracted extension resulted in a westward migration of graben-bounding faults. Phases of coeval volcanism at 2.8-2.6 Ma, 2.5-2.2 Ma, and 1.5-1.1 Ma, decreased in eruptive volume through time and are delineated on the basis of mapped stratigraphy, argon geochronology, paleomagnetic and aeromagnetic properties, and record a syntectonic westward migration of eruptive centers. The alignment of vent areas with mapped faults strongly suggests deep magmatic sources utilized local structures as conduits (i.e. faults and fractures developed in response to regional stress). However, some near-surface feeder dikes associated with eroded cinder cones record orientations that are not typically correlative with regional fault patterns suggesting near-surface conduits are

  16. Fluid-Solid Interaction and Multiscale Dynamic Processes: Experimental Approach

    Science.gov (United States)

    Arciniega-Ceballos, Alejandra; Spina, Laura; Mendo-Pérez, Gerardo M.; Guzmán-Vázquez, Enrique; Scheu, Bettina; Sánchez-Sesma, Francisco J.; Dingwell, Donald B.

    2017-04-01

    . Analysis of time series, both experimental and synthetics, synchronized with high-speed imaging enables the explanation and interpretation of distinct phases of the dynamics of these fluids and the extraction of time and frequency characteristics of the individual processes. We observed that the effects of both, pressure drop triggering function and viscosity, control the characteristics of the micro-signals in time and frequency. This suggests the great potential that experimental and numerical approaches provide to untangle from field volcanic seismograms the multiscale processes of the stress field, driving forces and fluid-rock interaction that determine the volcanic conduit dynamics.

  17. Volcanic hazards to airports

    Science.gov (United States)

    Guffanti, M.; Mayberry, G.C.; Casadevall, T.J.; Wunderman, R.

    2009-01-01

    Volcanic activity has caused significant hazards to numerous airports worldwide, with local to far-ranging effects on travelers and commerce. Analysis of a new compilation of incidents of airports impacted by volcanic activity from 1944 through 2006 reveals that, at a minimum, 101 airports in 28 countries were affected on 171 occasions by eruptions at 46 volcanoes. Since 1980, five airports per year on average have been affected by volcanic activity, which indicates that volcanic hazards to airports are not rare on a worldwide basis. The main hazard to airports is ashfall, with accumulations of only a few millimeters sufficient to force temporary closures of some airports. A substantial portion of incidents has been caused by ash in airspace in the vicinity of airports, without accumulation of ash on the ground. On a few occasions, airports have been impacted by hazards other than ash (pyroclastic flow, lava flow, gas emission, and phreatic explosion). Several airports have been affected repeatedly by volcanic hazards. Four airports have been affected the most often and likely will continue to be among the most vulnerable owing to continued nearby volcanic activity: Fontanarossa International Airport in Catania, Italy; Ted Stevens Anchorage International Airport in Alaska, USA; Mariscal Sucre International Airport in Quito, Ecuador; and Tokua Airport in Kokopo, Papua New Guinea. The USA has the most airports affected by volcanic activity (17) on the most occasions (33) and hosts the second highest number of volcanoes that have caused the disruptions (5, after Indonesia with 7). One-fifth of the affected airports are within 30 km of the source volcanoes, approximately half are located within 150 km of the source volcanoes, and about three-quarters are within 300 km; nearly one-fifth are located more than 500 km away from the source volcanoes. The volcanoes that have caused the most impacts are Soufriere Hills on the island of Montserrat in the British West Indies

  18. Nerve regeneration in chitosan conduits and in autologous nerve grafts in healthy and in type 2 diabetic Goto-Kakizaki rats.

    Science.gov (United States)

    Stenberg, Lena; Kodama, Akira; Lindwall-Blom, Charlotta; Dahlin, Lars B

    2016-02-01

    Knowledge about nerve regeneration after nerve injury and reconstruction in appropriate diabetic animal models is incomplete. Short-term nerve regeneration after reconstruction of a 10-mm sciatic nerve defect with either a hollow chitosan conduit or an autologous nerve graft was investigated in healthy Wistar and diabetic Goto-Kakizaki (GK) rats. After 21 days, axonal outgrowth, the presence of activated and apoptotic Schwann cells and the thickness of the formed matrix in the conduits were measured. In general, nerve regeneration was superior in autologous nerve grafts. In chitosan conduits, a matrix, which was thicker in diabetic rats, was formed and was positively correlated with length of axonal outgrowth. Axonal outgrowth in conduits and in nerve grafts extended further in diabetic rats than in healthy rats. There was a higher percentage of activating transcription factor 3 (ATF3)-immunostained cells in nerve segments from healthy rats than in diabetic rats after autologous nerve graft reconstruction. In chitosan conduits, more cleaved caspase 3-stained Schwann cells were generally observed in the matrix from the diabetic rats than in healthy rats. However, there were fewer apoptotic cells in the distal segment in diabetic rats reconstructed with a chitosan conduit. Preoperative glucose levels were positively correlated with axonal outgrowth after both reconstruction methods. Axonal regeneration was better in autologous nerve grafts than in hollow chitosan conduits and was enhanced in diabetic GK rats compared to healthy rats after reconstruction. This study provides insights into the nerve regeneration process in a clinically relevant diabetic animal model. © 2015 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  19. Explosive device of conduit using Ti Ni alloy

    Directory of Open Access Journals (Sweden)

    A. Yu. Kolobov

    2014-01-01

    Full Text Available Presently, materials have been developed which are capable at changing temperate to return significant inelastic deformations, exhibit rubber-like elasticity, convert heat into mechanical work, etc. The aggregate of these effects is usually called the shape memory effect.At present a great number of compounds and alloys with a shape memory effect has been known.These are alloys based on titanium nickelide (TiNi, copper-based alloys (Cu-Al, Cu-Sn, Cu-Al-Ni, Cu-Zn-Si, etc., gold and silver (Ag-Cd, Au-Ag-Cd, Au-Cd-Cu, Au-Zn-Cu, etc., manganese (Mn-Cr, Fe-Cu, Mn-Cu-Ni, Mn-Cu-Zr, Mn-Ni, etc., iron (Fe-Mn, Fe-Ni, Fe-Al, etc., and other compounds.The alloys based on titanium nickelide (nitinol are the most widely used.Alloys with shape memory effect find various applications in engineering and medicine, namely connecting devices, actuators, transformable design, multipurpose medical implants, etc.There is a task of breaking fuel conduit during separating the spacecraft from the rocket in space technology.The paper examines the procedure for design calculation of the separating device of conduit with the use of Ti-Ni alloy. This device can be used instead of the pyro-knives.The device contains two semi-rings from Ti-Ni alloy. In the place of break on the conduit an annular radius groove is made.At a temperature of martensite passage the semi-rings undergo deformation and in the strained state are set in the device. With heating to the temperature of the austenitic passage of bushing macro-deformation the energy stored by the nitinol bushing is great enough to break the conduit on the neck.The procedures of design calculation and response time of device are given.

  20. Stable and Reactive Centering in Conduits for Karstic Exploration

    OpenAIRE

    2014-01-01

    International audience; Karst groundwaters provide fresh water resources to supply cities. In the case of deep groundwater resources around the Mediterranean basin there is a need to explore karst aquifers and gather data about their structure. Robots are well adapted for this task especially when exploring karst conduits at depths greater than 200m. However, as karst aquifers environment is very complex, robots need to exhibit a collection of abilities to ensure a safe exploration. Among the...

  1. Collagen Type I Conduits for the Regeneration of Nerve Defects

    Directory of Open Access Journals (Sweden)

    Silvan Klein

    2016-03-01

    Full Text Available To date, reliable data to support the general use of biodegradable materials for bridging nerve defects are still scarce. We present the outcome of nerve regeneration following type I collagen conduit nerve repair in patients with large-diameter nerve gaps. Ten patients underwent nerve repair using a type I collagen nerve conduit. Patients were re-examined at a minimal follow-up of 14.0 months and a mean follow-up of 19.9 months. Regeneration of nerve tissue within the conduits was assessed by nerve conduction velocity (NCV, a static two-point discrimination (S2PD test, and as disability of arm shoulder and hand (DASH outcome measure scoring. Quality of life measures including patients’ perceived satisfaction and residual pain were evaluated using a visual analog scale (VAS. No implant-related complications were observed. Seven out of 10 patients reported being free of pain, and the mean VAS was 1.1. The mean DASH score was 17.0. The S2PD was below 6 mm in 40%, between 6 and 10 mm in another 40% and above 10 mm in 20% of the patients. Eight out of 10 patients were satisfied with the procedure and would undergo surgery again. Early treatment correlated with lower DASH score levels. The use of type I collagen in large-diameter gaps in young patients and early treatment presented superior functional outcomes.

  2. Free-boundary models of a meltwater conduit

    KAUST Repository

    Dallaston, Michael C.

    2014-08-01

    © 2014 AIP Publishing LLC. We analyse the cross-sectional evolution of an englacial meltwater conduit that contracts due to inward creep of the surrounding ice and expands due to melting. Making use of theoretical methods from free-boundary problems in Stokes flow and Hele-Shaw squeeze flow we construct an exact solution to the coupled problem of external viscous creep and internal heating, in which we adopt a Newtonian approximation for ice flow and an idealized uniform heat source in the conduit. This problem provides an interesting variant on standard free-boundary problems, coupling different internal and external problems through the kinematic condition at the interface. The boundary in the exact solution takes the form of an ellipse that may contract or expand (depending on the magnitudes of effective pressure and heating rate) around fixed focal points. Linear stability analysis reveals that without the melting this solution is unstable to perturbations in the shape. Melting can stabilize the interface unless the aspect ratio is too small; in that case, instabilities grow largest at the thin ends of the ellipse. The predictions are corroborated with numerical solutions using boundary integral techniques. Finally, a number of extensions to the idealized model are considered, showing that a contracting circular conduit is unstable to all modes of perturbation if melting occurs at a uniform rate around the boundary, or if the ice is modelled as a shear-thinning fluid.

  3. Melting Behavior of Volcanic Ash relevant to Aviation Ash Hazard

    Science.gov (United States)

    Song, W.; Hess, K.; Lavallee, Y.; Cimarelli, C.; Dingwell, D. B.

    2013-12-01

    Volcanic ash is one of the major hazards caused by volcanic eruptions. In particular, the threat to aviation from airborne volcanic ash has been widely recognized and documented. In the past 12 years, more than 60 modern jet airplanes, mostly jumbo jets, have been damaged by drifting clouds of volcanic ash that have contaminated air routes and airport facilities. Seven of these encounters are known to have caused in-flight loss of engine power to jumbo jets carrying a total of more than 2000 passengers. The primary cause of engine thrust loss is that the glass in volcanic ash particles is generated at temperatures far lower than the temperatures in the combustion chamber of a jet engine ( i.e. > 1600 oC) and when the molten volcanic ash particles leave this hottest section of the engine, the resolidified molten volcanic ash particles will be accumulated on the turbine nozzle guide vanes, which reduced the effective flow of air through the engine ultimately causing failure. Thus, it is essential to investigate the melting process and subsequent deposition behavior of volcanic ash under gas turbine conditions. Although few research studies that investigated the deposition behavior of volcanic ash at the high temperature are to be found in public domain, to the best our knowledge, no work addresses the formation of molten volcanic ash. In this work, volcanic ash produced by Santiaguito volcano in Guatemala in November 8, 2012 was selected for study because of their recent activity and potential hazard to aircraft safety. We used the method of accessing the behavior of deposit-forming impurities in high temperature boiler plants on the basis of observations of the change in shape and size of a cylindrical coal ash to study the sintering and fusion phenomena as well as determine the volcanic ash melting behavior by using characteristic temperatures by means of hot stage microscope (HSM), different thermal analysis (DTA) and Thermal Gravimetric Analysis (TGA) to

  4. Precambrian Lunar Volcanic Protolife

    Directory of Open Access Journals (Sweden)

    Jack Green

    2009-06-01

    Full Text Available Five representative terrestrial analogs of lunar craters are detailed relevant to Precambrian fumarolic activity. Fumarolic fluids contain the ingredients for protolife. Energy sources to derive formaldehyde, amino acids and related compounds could be by flow charging, charge separation and volcanic shock. With no photodecomposition in shadow, most fumarolic fluids at 40 K would persist over geologically long time periods. Relatively abundant tungsten would permit creation of critical enzymes, Fischer-Tropsch reactions could form polycyclic aromatic hydrocarbons and soluble volcanic polyphosphates would enable assembly of nucleic acids. Fumarolic stimuli factors are described. Orbital and lander sensors specific to protolife exploration including combined Raman/laser-induced breakdown spectrocsopy are evaluated.

  5. Refilling embolized xylem conduits: is it a matter of phloem unloading?

    Science.gov (United States)

    Nardini, Andrea; Lo Gullo, Maria A; Salleo, Sebastiano

    2011-04-01

    Long-distance water transport in plants relies on negative pressures established in continuous water columns in xylem conduits. Water under tension is in a metastable state and is prone to cavitation and embolism, which leads to loss of hydraulic conductance, reduced productivity and eventually plant death. Experimental evidence suggests that plants can repair embolized xylem by pushing water from living vessel-associated cells into the gas-filled conduit lumina. Most surprisingly, embolism refilling is known to occur even when the bulk of still functioning xylem is under tension, a finding that is in seemingly contradiction to basic principles of thermodynamics. This review summarizes our current understanding of xylem refilling processes and speculates that embolism repair under tension can be envisioned as a particular case of phloem unloading, as suggested by several events and components of embolism repair, typically involved in phloem unloading mechanisms. Far from being a challenge to irreversible thermodynamics, embolism refilling is emerging as a finely regulated vital process essential for plant functioning under different environmental stresses. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  6. Use of short half-life cosmogenic isotopes to quantify sediment mixing and transport in karst conduits

    Science.gov (United States)

    Paylor, R.

    2011-12-01

    Particulate inorganic carbon (PIC) transport and flux in karst aquifers is poorly understood. Methods to quantify PIC flux are needed in order to account for total inorganic carbon removal (chemical plus mechanical) from karst settings. Quantifying PIC flux will allow more accurate calculations of landscape denudation and global carbon sink processes. The study concentrates on the critical processes of the suspended sediment component of mass flux - surface soil/stored sediment mixing, transport rates and distance, and sediment storage times. The primary objective of the study is to describe transport and mixing with the resolution of single storm-flow events. To quantify the transport processes, short half-life cosmogenic isotopes are utilized. The isotopes 7Be (t1/2 = 53d) and 210Pb (t1/2 = 22y) are the primary isotopes measured, and other potential isotopes such as 137Cs and 241Am are investigated. The study location is at Mammoth Cave National Park within the Logsdon River watershed. The Logsdon River conduit is continuously traversable underground for two kilometers. Background levels and input concentrations of isotopes are determined from soil samples taken at random locations in the catchment area, and suspended sediment collected from the primary sinking stream during a storm event. Suspended sediment was also collected from the downstream end of the conduit during the storm event. After the storm flow receded, fine sediment samples were taken from the cave stream at regular intervals to determine transport distances and mixing ratios along the conduit. Samples were analyzed with a Canberra Industries gamma ray spectrometer, counted for 24 hours to increase detection of low radionuclide activities. The measured activity levels of radionuclides in the samples were adjusted for decay from time of sampling using standard decay curves. The results of the study show that surface sediment mixing, transport and storage in karst conduits is a dynamic but

  7. Lung problems and volcanic smog

    Science.gov (United States)

    ... releases gases into the atmosphere. Volcanic smog can irritate the lungs and make existing lung problems worse. ... deep into the lungs. Breathing in volcanic smog irritates the lungs and mucus membranes. It can affect ...

  8. Volcanic Supersites as cross-disciplinary laboratories

    Science.gov (United States)

    Provenzale, Antonello; Beierkuhnlein, Carl; Giamberini, Mariasilvia; Pennisi, Maddalena; Puglisi, Giuseppe

    2017-04-01

    Volcanic Supersites, defined in the frame of the GEO-GSNL Initiative, are usually considered mainly for their geohazard and geological characteristics. However, volcanoes are extremely challenging areas from many other points of view, including environmental and climatic properties, ecosystems, hydrology, soil properties and biogeochemical cycling. Possibly, volcanoes are closer to early Earth conditions than most other types of environment. During FP7, EC effectively fostered the implementation of the European volcano Supersites (Mt. Etna, Campi Flegrei/Vesuvius and Iceland) through the MED-SUV and FUTUREVOLC projects. Currently, the large H2020 project ECOPOTENTIAL (2015-2019, 47 partners, http://www.ecopotential-project.eu/) contributes to GEO/GEOSS and to the GEO ECO Initiative, and it is devoted to making best use of remote sensing and in situ data to improve future ecosystem benefits, focusing on a network of Protected Areas of international relevance. In ECOPOTENTIAL, remote sensing and in situ data are collected, processed and used for a better understanding of the ecosystem dynamics, analysing and modelling the effects of global changes on ecosystem functions and services, over an array of different ecosystem types, including mountain, marine, coastal, arid and semi-arid ecosystems, and also areas of volcanic origin such as the Canary and La Reunion Islands. Here, we propose to extend the network of the ECOPOTENTIAL project to include active Volcanic Supersites, such as Mount Etna and other volcanic Protected Areas, and we discuss how they can be included in the framework of the ECOPOTENTIAL workflow. A coordinated and cross-disciplinary set of studies at these sites should include geological, biological, ecological, biogeochemical, climatic and biogeographical aspects, as well as their relationship with the antropogenic impact on the environment, and aim at the global analysis of the volcanic Earth Critical Zone - namely, the upper layer of the Earth

  9. The influence of tectonic and volcanic processes on the morphology of the Iberian continental margins; Influencia de los procesos tectonicos y volcanicos en la morfologia de los margenes continentales ibericos

    Energy Technology Data Exchange (ETDEWEB)

    Maestro, A.; Bohoyo, F.; Lopez-Martinez, J.; Acosta, J.; Gomez-Ballesteros, M.; Llaave, E.; Munoz, A.; Terrinha, P. G.; Dominguez, M.; Fernandez-Saez, F.

    2015-07-01

    The Iberian continental margins are mainly passive margins. Nevertheless, the northern sector of the margin was active during some stages of its geological evolution. The southern sector is considered as a transformed margin, which defines the boundary between the Iberian and African plates. This margin was also an active margin in the past. The different types, origins and intensities of the endogenic processes that have affected he Iberian continental margins have led to the development of various tectonic and volcanic morphologies. The North Atlantic rifting allowed the development of large marginal platforms in the Cantabrian and Galician margins the North-Atlantic Ocean spreading. The reactivation of Variscan faults during the Mesozoic and Cenozoic controlled the strike of some of the largest canyons in the Iberian margins. The Gulf of Cadiz margin is characterized by the development of morphologies related to salt tectonic, fluid seepage, thrust fronts and strike-slip fault lineaments hundreds of kilometres long. The Alboran basin and the Betic margin show morphologies connected with the Miocene rift phase, which generated volcanic edifices and various structural reliefs, and with the subsequent compressive phase, when folds and strike-slip, reverse faults, diapirs and mud volcanoes were developed. Finally, the Catalan-Valencian margin and the Balearic promontory are characterized by the presence of horst and graben structures related to the development of the Valencia trough during the Paleogene. The morphological features of endogenic origin have largely controlled the location and extent of the sedimentary processes and morphological products along the Iberian margins. (Author)

  10. Insights into Focused Fluid Conduit Formation from Comparing Seismic Chimneys and Pipes with Field Observations of Fluid Flow Manifestations in the Colorado Plateau

    Science.gov (United States)

    Karstens, J.; Berndt, C.

    2014-12-01

    The understanding of focused fluid flow in sedimentary basins builds on field geological observations and the interpretation of reflection seismic data, where fluid conduits manifest as anomalous amplitude patterns known as seismic chimneys or pipes. Seismic data is the most effective method for the analysis of entire fluid flow systems by constraining subsurface geometries, fluid accumulations and permeability barriers, but seismic data cannot provide information about the internal architecture, interaction with the bedrock and flow processes due to its coarse resolution. Field geological investigations of fluid conduit outcrops are capable of filling observation gaps on a sub-seismic scale and help constrain formation dynamics as well as hydraulic properties of fluid conduits and the bedrock. Here, we show that it is possible to correlate specific amplitude patterns of seismic chimneys with field observation of focused fluid conduits from the Colorado Plateau. The migrating fluids (gas, water, fluidized sediment) and their formation dynamics, which can be associated with different types of conduits (fractures, fluidizations, injections), result in distinguishable seismic signatures. These constrains improve the qualitative interpretation of seismic chimneys by adding information about migration and formation characteristics. A further integration of field geological and seismic investigation of focused fluid flow structures may help to quantify their hydraulic properties and how these evolve with time, which has important implications for the hydrocarbon prospection and the subsurface storage of wastewater and CO2.

  11. Volcanism and Oil & Gas In Northeast China

    Institute of Scientific and Technical Information of China (English)

    Shan Xuanlong

    2000-01-01

    Based on study on the relation with volcanic rock and oil & gas in Songliao Basin and Liaohe Basin in northeast China, author proposes that material from deep by volcanism enrichs the resources in basins, that heat by volcanism promotes organic matter transforming to oil and gas, that volcanic reservoir is fracture, vesicular, solution pore, intercrystal pore.Lava facies and pyroclastic facies are favourable reservoir. Mesozoic volcanic reservoir is majority of intermediate, acid rock,but Cenozoic volcanic reservoir is majority of basalt. Types of oil and gas pool relating to volcanic rock include volcanic fracture pool, volcanic unconformity pool, volcanic rock - screened pool, volcanic darpe structural pool.

  12. Modeling volcanic ash dispersal

    CERN Document Server

    CERN. Geneva

    2010-01-01

    The assessment of volcanic fallout hazard is an important scientific, economic, and political issue, especially in densely populated areas. From a scientific point of view, considerable progress has been made during the last two decades through the use of increasingly powerful computational models and capabilities. Nowadays, models are used to quantify hazard...

  13. The Chthonic Charging of Volcanic Flows: The Generation of Vent Lightning

    Science.gov (United States)

    Méndez Harper, J.; Dufek, J.

    2015-12-01

    While volcanic lightning has been reported for millennia, the physics that generate charge in plumes still require clarification. Lightning observations during the Augustine (2006) and Redoubt (2009) eruptions have revealed a new form of lightning: nearly continuous, vent discharges associated with the explosive phase of the eruption. Vent lightning is often small (10-100 m in length) and disorganized, suggesting the existence of multiple, transient charge centers proximal to the volcanic vent. Thomas et al., 2007 and Behnke et al., 2012 have postulated that this form of lightning is driven by fragmentation charging [James et al., 2008]. However, triboelectrification—frictional charging arising from particle-particle collisions as material is advected up to the vent—should also play an important role. Because tribocharging is modulated by collision rates and energies, it is within the conduit and the gas-thrust regions that this frictional process should be most efficient. Indeed, the work of Cimarelli et al., 2014 has suggested that lightning can be generated at the vent via triboelectric charging alone. Using an energy-based comparison, we investigate the relative efficiencies of fracto- and triboelectric charging. To generate charged particles via a fragmentation process, we employ Prince Rupert's Drops (PRDs), meta-stable, tadpole-shaped structures formed by quenching molten glass in water. While a PDR's head is extremely strong, even the slightest damage to the tail causes explosive disintegration of the drop [Silverman et al., 2012]. A set of PDRs are disrupted in a controlled environment and the charge on the resulting particles is measured using a set of Faraday cups. The energy density associated with the breaking of PRDs is on the order of 105-106 J/m3. Then, to investigate tribocharging at similar energies, we eject spherical particles at high velocities, producing particle-particle collisions in a novel Faraday cube sensor. Our setup allows us to

  14. Mechanism of formation of volcanic bombs: insights from a pilot study of anisotropy of magnetic susceptibility and preliminary assessment of analytical models

    Science.gov (United States)

    Cañón-Tapia, Edgardo

    2017-07-01

    Volcanic bombs and achneliths are a special type of pyroclastic fragments formed by mildly explosive volcanic eruptions. Models explaining the general shapes of those particles can be divided in two broad categories. The most popular envisages the acquisition of shapes of volcanic bombs as the result of the rush of air acting on a fluid clot during flight, and it includes many variants. The less commonly quoted model envisages their shapes as the result of forces acting at the moment of ejection of liquid from the magma pool in the conduit, experiencing an almost negligible modification through its travel through air. Quantitative evidence supporting either of those two models is limited. In this work, I explore the extent to which the anisotropy of magnetic susceptibility (AMS) might be useful in the study of mechanisms of formation of volcanic bombs by comparing measurements made on two spindle and two bread-crusted bombs. The results of this pilot study reveal that the degree of anisotropy of spindle bombs is larger, and their principal susceptibility axes are better clustered than on bread-crusted bombs. Also, the orientation of the principal susceptibility axes is consistent with two specific models (one of the in-flight variants and the general ejection model). Consequently, the reported AMS measurements, albeit limited in number, indicate that it is reasonable to focus attention on only two specific models to explain the acquisition of the shapes of volcanic bombs. Based on a parallel theoretical assessment of analytical models, a third alternative is outlined, envisaging volcanic bomb formation as a two-stage process that involves the bursting of large ( m) gas bubbles on the surface of a magma pond. The new model advanced here is also consistent with the reported AMS results, and constitutes a working hypothesis that should be tested by future studies richer in data. Fortunately, since this work also establishes that AMS can be used to determine magnetic

  15. VOLCANIC TSUNAMI GENERATING SOURCE MECHANISMS IN THE EASTERN CARIBBEAN REGION

    Directory of Open Access Journals (Sweden)

    George Pararas-Carayannis

    2004-01-01

    Full Text Available Earthquakes, volcanic eruptions, volcanic island flank failures and underwater slides have generated numerous destructive tsunamis in the Caribbean region. Convergent, compressional and collisional tectonic activity caused primarily from the eastward movement of the Caribbean Plate in relation to the North American, Atlantic and South American Plates, is responsible for zones of subduction in the region, the formation of island arcs and the evolution of particular volcanic centers on the overlying plate. The inter-plate tectonic interaction and deformation along these marginal boundaries result in moderate seismic and volcanic events that can generate tsunamis by a number of different mechanisms. The active geo-dynamic processes have created the Lesser Antilles, an arc of small islands with volcanoes characterized by both effusive and explosive activity. Eruption mechanisms of these Caribbean volcanoes are complex and often anomalous. Collapses of lava domes often precede major eruptions, which may vary in intensity from Strombolian to Plinian. Locally catastrophic, short-period tsunami-like waves can be generated directly by lateral, direct or channelized volcanic blast episodes, or in combination with collateral air pressure perturbations, nuéss ardentes, pyroclastic flows, lahars, or cascading debris avalanches. Submarine volcanic caldera collapses can also generate locally destructive tsunami waves. Volcanoes in the Eastern Caribbean Region have unstable flanks. Destructive local tsunamis may be generated from aerial and submarine volcanic edifice mass edifice flank failures, which may be triggered by volcanic episodes, lava dome collapses, or simply by gravitational instabilities. The present report evaluates volcanic mechanisms, resulting flank failure processes and their potential for tsunami generation. More specifically, the report evaluates recent volcanic eruption mechanisms of the Soufriere Hills volcano on Montserrat, of Mt. Pel

  16. Ozone depletion following future volcanic eruptions

    Science.gov (United States)

    Eric Klobas, J.; Wilmouth, David M.; Weisenstein, Debra K.; Anderson, James G.; Salawitch, Ross J.

    2017-07-01

    While explosive volcanic eruptions cause ozone loss in the current atmosphere due to an enhancement in the availability of reactive chlorine following the stratospheric injection of sulfur, future eruptions are expected to increase total column ozone as halogen loading approaches preindustrial levels. The timing of this shift in the impact of major volcanic eruptions on the thickness of the ozone layer is poorly known. Modeling four possible climate futures, we show that scenarios with the smallest increase in greenhouse gas concentrations lead to the greatest risk to ozone from heterogeneous chemical processing following future eruptions. We also show that the presence in the stratosphere of bromine from natural, very short-lived biogenic compounds is critically important for determining whether future eruptions will lead to ozone depletion. If volcanic eruptions inject hydrogen halides into the stratosphere, an effect not considered in current ozone assessments, potentially profound reductions in column ozone would result.

  17. Tensile and fatigue qualification testing of ITER-CS conduit alloy JK2LB

    Science.gov (United States)

    Walsh, R. P.; McRae, D. M.; Han, K.; Martovetsky, N. N.

    2015-12-01

    The ITER Central Solenoid (CS) coils utilize cable-in-conduit conductor (CICC) and the conduit alloy is JK2LB. The production grade conduit alloy (and it's welds) must meet strict requirements for strength, toughness, fatigue crack resistance, and fabricability. The conduit alloy must retain good mechanical properties after additional fabrication steps such as welding, coil winding strain and exposure to the Nb3Sn superconductor's reaction heat treatment. Here we present data from cryogenic tensile, fracture toughness, fatigue crack growth rate, and axial fatigue tests of JK2LB alloy and conduit butt welds, before and after the exposure to the reaction heat treatment. The tests of specimens removed directly from the conduit provide confirmation of the materials properties and the effect of the cold work and aging. The 4 K fatigue performance is extremely important to the reliability of the CS and is covered both by axial cyclic fatigue tests and the fatigue crack growth rate measurements.

  18. Sensing turbulent flow and heat transport in a cave conduit

    Science.gov (United States)

    Kurtzman, D.; Lucia, F. J.; Jennings, J. W.; Wilson, J. L.; Tyler, S. W.; Jorgensen, A. M.; Dwivedi, R.; Boston, P.; Burger, P.

    2008-12-01

    Cave systems provide an extreme example of complex subsurface porous media, dominated by flow through an interconnected network of conduits. Whether water or air-filled, these flow systems have been largely observed subjectively, with only a few simple quantitative measurements of flow and pressure. In the spring of 2008 a joint campaign of New Mexico Tech and the University of Nevada Reno entered the 210m deep, ~8m "diameter," keyhole shaped, subhorizontal, Left Hand Tunnel, a large air-filled conduit in Carlsbad Caverns, New Mexico, with the intent to observe fluid flow with modern thermally-based instruments. The conduit experiences countercurrent, thermally stratified flow, with mean velocities in each layer less than 0.1m/s. It is part of a geothermally forced, large-scale convection cell. Two instruments were deployed. A distributed temperature sensing (DTS) fiber optic cable was stretched over 1km of the tunnel, and partially suspended by balloons to the roof, to sense spatial and low-frequency (0.01Hz) temporal variations of temperature with a resolution approaching 0.05 degree C. The mean temperature difference between layers was on the order of 0.5 degree and the caveward (subhorizontal) temperature gradient was 1 degree/400m. Influences of connecting subvertical shafts, wet areas of the cave, human activity, and diurnal fluctuations were observed. The second instrument, a 7m tall tower with an array of eight 300Hz thermocouple temperature sensors, with a sensitivity approaching 0.005 degree, was deployed 200m into the tunnel and used to detect high- frequency temperature fluctuations associated with turbulence and the stratified flow. Turbulence structure of each layer was similar. Temperature fluctuation (and turbulence intensity?) was significantly greater near the boundary between layers and its steep vertical gradient of mean temperature. Results from this 3-day campaign, as limited as they are, suggest that there is a wealth of information and

  19. Enhancing Peripheral Nerve Regeneration with a Novel Drug Delivering Nerve Conduit

    Science.gov (United States)

    2014-10-01

    Products 21 7. Participants & Other Collaborating Organizations 22 8. Special Reporting Requirements 23 9. Appendices 24 3... Corning Inc) were also added to the nerve conduit. Figure 2 illustrates the nerve conduit in which the drug (NGF) stored in the orifice between...7525 DLG 7E, Evonik). The PLGA was dissolved in acetone and ethanol and conduits were then formed and emulsified in water. 15µm diffusion holes

  20. Study on Braiding Parameters of a Biodegradable Nerve Regeneration Conduit with Regular Braided Structure

    Institute of Scientific and Technical Information of China (English)

    LIU Guo-hua; ZHANG Pei-hua; WANG Wen-zu; FENG Xun-wei; LIU Hong-feng

    2004-01-01

    A biodegradable nerve regeneration conduit has been developed by the regular braided technique on a spindle-braiding machine. The geometry property indexes of braided nerve conduit consist of pitch, density, wall thickness and porosity etc. In this article, the influences of the braiding parameters i.e. the linear density of yarn, gear ratio and spindle number of the braiding machine on these geometry property indexes of nerve conduit were discussed from which the optimal braiding parameters were obtained.

  1. Flow-to-fracture transition in a volcanic mush plug may govern normal eruptions at Stromboli

    Science.gov (United States)

    Suckale, J.; Keller, T.; Cashman, K. V.; Persson, P.-O.

    2016-12-01

    Stromboli is a model volcano for studying eruptions driven by degassing. The current paradigm posits that Strombolian eruptions represent the bursting of gas slugs ascending through melt-filled conduits, but petrological observations show that magma at shallow depth is crystalline enough to form a three-phase plug consisting of crystals, bubbles, and melt. We combine a 1-D model of gas flushing a crystalline mush with a 3-D stress model. Our results suggest that localized gas segregation establishes hot conduits of mobile magma within a stagnant plug. The plug is prone to tensile failure controlled by gas overpressure and tectonic stress, with failure most likely beneath the observed vent locations. We hence argue that Strombolian eruptions are related to plug failure rather than flow. Our proposed three-phase model of the shallow plumbing system may provide a promising framework for integrating geophysical, petrological, and morphological observations at Stromboli and in open-system volcanism more generally.

  2. Actinobacterial Diversity in Volcanic Caves and Associated Geomicrobiological Interactions.

    Science.gov (United States)

    Riquelme, Cristina; Marshall Hathaway, Jennifer J; Enes Dapkevicius, Maria de L N; Miller, Ana Z; Kooser, Ara; Northup, Diana E; Jurado, Valme; Fernandez, Octavio; Saiz-Jimenez, Cesareo; Cheeptham, Naowarat

    2015-01-01

    Volcanic caves are filled with colorful microbial mats on the walls and ceilings. These volcanic caves are found worldwide, and studies are finding vast bacteria diversity within these caves. One group of bacteria that can be abundant in volcanic caves, as well as other caves, is Actinobacteria. As Actinobacteria are valued for their ability to produce a variety of secondary metabolites, rare and novel Actinobacteria are being sought in underexplored environments. The abundance of novel Actinobacteria in volcanic caves makes this environment an excellent location to study these bacteria. Scanning electron microscopy (SEM) from several volcanic caves worldwide revealed diversity in the morphologies present. Spores, coccoid, and filamentous cells, many with hair-like or knobby extensions, were some of the microbial structures observed within the microbial mat samples. In addition, the SEM study pointed out that these features figure prominently in both constructive and destructive mineral processes. To further investigate this diversity, we conducted both Sanger sequencing and 454 pyrosequencing of the Actinobacteria in volcanic caves from four locations, two islands in the Azores, Portugal, and Hawai'i and New Mexico, USA. This comparison represents one of the largest sequencing efforts of Actinobacteria in volcanic caves to date. The diversity was shown to be dominated by Actinomycetales, but also included several newly described orders, such as Euzebyales, and Gaiellales. Sixty-two percent of the clones from the four locations shared less than 97% similarity to known sequences, and nearly 71% of the clones were singletons, supporting the commonly held belief that volcanic caves are an untapped resource for novel and rare Actinobacteria. The amplicon libraries depicted a wider view of the microbial diversity in Azorean volcanic caves revealing three additional orders, Rubrobacterales, Solirubrobacterales, and Coriobacteriales. Studies of microbial ecology in

  3. Environmental tracers as indicators of karst conduits in groundwater in South Dakota, USA

    Science.gov (United States)

    Long, A.J.; Sawyer, J.F.; Putnam, L.D.

    2008-01-01

    Environmental tracers sampled from the carbonate Madison aquifer on the eastern flank of the Black Hills, South Dakota, USA indicated the approximate locations of four major karst conduits. Contamination issues are a major concern because these conduits are characterized by direct connections to sinking streams, high groundwater velocities, and proximity to public water supplies. Objectives of the study were to estimate approximate conduit locations and assess possible anthropogenic influences associated with conduits. Anomalies of young groundwater based on chlorofluorocarbons (CFCs), tritium, and electrical conductivity (EC) indicated fast moving, focused flow and thus the likely presence of conduits. ??18O was useful for determining sources of recharge for each conduit, and nitrate was a useful tracer for assessing flow paths for anthropogenic influences. Two of the four conduits terminate at or near a large spring complex. CFC apparent ages ranged from 15 years near conduits to >50 years in other areas. Nitrate-N concentrations >0.4 mg/L in groundwater were associated with each of the four conduits compared with concentrations ranging from <0.1 to 0.4 mg/L in other areas. These higher nitrate-N concentrations probably do not result from sinking streams but rather from other areas of infiltration. ?? Springer-Verlag 2007.

  4. 3D-engineering of Cellularized Conduits for Peripheral Nerve Regeneration

    Science.gov (United States)

    Hu, Yu; Wu, Yao; Gou, Zhiyuan; Tao, Jie; Zhang, Jiumeng; Liu, Qianqi; Kang, Tianyi; Jiang, Shu; Huang, Siqing; He, Jiankang; Chen, Shaochen; Du, Yanan; Gou, Maling

    2016-08-01

    Tissue engineered conduits have great promise for bridging peripheral nerve defects by providing physical guiding and biological cues. A flexible method for integrating support cells into a conduit with desired architectures is wanted. Here, a 3D-printing technology is adopted to prepare a bio-conduit with designer structures for peripheral nerve regeneration. This bio-conduit is consisted of a cryopolymerized gelatin methacryloyl (cryoGelMA) gel cellularized with adipose-derived stem cells (ASCs). By modeling using 3D-printed “lock and key” moulds, the cryoGelMA gel is structured into conduits with different geometries, such as the designed multichannel or bifurcating and the personalized structures. The cryoGelMA conduit is degradable and could be completely degraded in 2-4 months in vivo. The cryoGelMA scaffold supports the attachment, proliferation and survival of the seeded ASCs, and up-regulates the expression of their neurotrophic factors mRNA in vitro. After implanted in a rat model, the bio-conduit is capable of supporting the re-innervation across a 10 mm sciatic nerve gap, with results close to that of the autografts in terms of functional and histological assessments. The study describes an indirect 3D-printing technology for fabricating cellularized designer conduits for peripheral nerve regeneration, and could lead to the development of future nerve bio-conduits for clinical use.

  5. A silk sericin/silicone nerve guidance conduit promotes regeneration of a transected sciatic nerve.

    Science.gov (United States)

    Xie, Hongjian; Yang, Wen; Chen, Jianghai; Zhang, Jinxiang; Lu, Xiaochen; Zhao, Xiaobo; Huang, Kun; Li, Huili; Chang, Panpan; Wang, Zheng; Wang, Lin

    2015-10-28

    Peripheral nerve gap defects lead to significant loss of sensory or motor function. Tissue engineering has become an important alternative to nerve repair. Sericin, a major component of silk, is a natural protein whose value in tissue engineering has just begun to be explored. Here, the first time use of sericin in vivo is reported as a long-term implant for peripheral nerve regeneration. A sericin nerve guidance conduit is designed and fabricated. This conduit is highly porous with mechanical strength matching peripheral nerve tissue. It supports Schwann cell proliferation and is capable of up-regulating the transcription of glial cell derived neurotrophic factor and nerve growth factor in Schwann cells. The sericin conduit wrapped with a silicone conduit (sericin/silicone double conduits) is used for bridging repair of a 5 mm gap in a rat sciatic nerve transection model. The sericin/silicone double conduits achieve functional recovery comparable to that of autologous nerve grafting as evidenced by drastically improved nerve function and morphology. Importantly, this improvement is mainly attributed to the sericin conduit as the silicone conduit alone only produces marginal functional recovery. This sericin/silicone-double-conduit strategy offers an efficient and valuable alternative to autologous nerve grafting for repairing damaged peripheral nerve. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. 3D-engineering of Cellularized Conduits for Peripheral Nerve Regeneration

    Science.gov (United States)

    Hu, Yu; Wu, Yao; Gou, Zhiyuan; Tao, Jie; Zhang, Jiumeng; Liu, Qianqi; Kang, Tianyi; Jiang, Shu; Huang, Siqing; He, Jiankang; Chen, Shaochen; Du, Yanan; Gou, Maling

    2016-01-01

    Tissue engineered conduits have great promise for bridging peripheral nerve defects by providing physical guiding and biological cues. A flexible method for integrating support cells into a conduit with desired architectures is wanted. Here, a 3D-printing technology is adopted to prepare a bio-conduit with designer structures for peripheral nerve regeneration. This bio-conduit is consisted of a cryopolymerized gelatin methacryloyl (cryoGelMA) gel cellularized with adipose-derived stem cells (ASCs). By modeling using 3D-printed “lock and key” moulds, the cryoGelMA gel is structured into conduits with different geometries, such as the designed multichannel or bifurcating and the personalized structures. The cryoGelMA conduit is degradable and could be completely degraded in 2-4 months in vivo. The cryoGelMA scaffold supports the attachment, proliferation and survival of the seeded ASCs, and up-regulates the expression of their neurotrophic factors mRNA in vitro. After implanted in a rat model, the bio-conduit is capable of supporting the re-innervation across a 10 mm sciatic nerve gap, with results close to that of the autografts in terms of functional and histological assessments. The study describes an indirect 3D-printing technology for fabricating cellularized designer conduits for peripheral nerve regeneration, and could lead to the development of future nerve bio-conduits for clinical use. PMID:27572698

  7. Evaluation of the ongoing rifting and subduction processes in the geochemistry of magmas from the western part of the Mexican Volcanic Belt

    Science.gov (United States)

    Verma, Surendra P.; Pandarinath, Kailasa; Rivera-Gómez, M. Abdelaly

    2016-03-01

    A compilation of new and published geochemical data for 1512 samples of volcanic rocks from the western part of the Mexican Volcanic Belt was first subdivided according to the age group (136 samples of Miocene and 1376 samples of Pliocene-Holocene). Rocks of the younger group were then subdivided as Rift (1014 samples from the triple-rift system) and No Rift (362 samples outside of the triple-rift system) or Near Trench (937 samples) and Far Trench (439 samples) magmas. These subdivisions were considered separately as basic, intermediate, and acid magmatic rocks. The application of the conventional and multidimensional techniques confirmed the great tectonic and geochemical complexity of this region. The presence of oceanic-type basalts suggested to result from a mantle plume was not confirmed from the tectonomagmatic multidimensional diagrams. The Miocene rocks, which are present at the surface far from the Middle-America Trench, showed a likely continental rift setting in most diagrams for basic rocks and a continental arc setting for intermediate rocks. These differences can be explained in terms of the petrogenetic origin of the magmas. Unlike the current thinking, the triple-rift system seems to have influenced the chemistry of Pliocene-Holocene basic rocks, which indicated a continental rift setting. The Pliocene-Holocene intermediate and acid rocks, however, did not show such an influence. The Pliocene-Holocene basic rocks indicated a continental rift setting, irrespective of the Near Trench and Far Trench subdivision because numerous Near Trench rocks also lie in the triple-rift and graben systems. However, the intermediate rocks having a crustal component in their genesis indicated a continental arc (Near Trench) or a transitional arc to within-plate setting (Far Trench). The acid rocks having a crustal component also suggested a continental arc (Near Trench) or a transitional setting (Far Trench). The application of the tectonomagmatic multidimensional

  8. Development of a new lacrimal drainage conduit using POSS nanocomposite.

    Science.gov (United States)

    Chaloupka, Karla; Motwani, Meghna; Seifalian, Alexander Marcus

    2011-01-01

    Lacrimal surgery in cases of severely obstructed or missing canalicular ducts is highly challenging. In these cases, the placement of a bypass tube is currently the only option to restore the drainage of tears into the nose and reduce the symptomatic watery eye. Different approaches to achieve functional drainage have been tried using blood vessels or artificial implants. The implantation of the rigid Lester Jones tube is, since its introduction in the late 1960s, the gold standard. The functional success is satisfactory. However, complication rates are high and remain, even with many modifications of the original design, a major problem. These complications include mainly the displacement and blockage of the tube, requiring regular checkups, as well as irritation of the surrounding tissue including the nose and the eye. The objective of this study was to develop a new lacrimal duct conduit (LDC) to restore structural and functional integrity of the lacrimal drainage system. The conduit is constructed with a novel polymer, polyhedral oligomeric silsesquioxane-poly(carbonate-urea)urethane (POSS-PCU), that offers biocompatibility. We exploit nanotopography to evade the problems associated with current applications. A number of extrusion techniques were investigated for this purpose: ultrasonic atomization spraying, electrohydrodynamic atomization spraying/spinning, extrusion-coagulation, and high-pressure coagulation by autoclave and casting. Finally, the coagulation and cast technique were selected to construct an LDC superior to its predecessors, and its advantages highlighted.

  9. Conduit for high temperature transfer of molten semiconductor crystalline material

    Science.gov (United States)

    Fiegl, George (Inventor); Torbet, Walter (Inventor)

    1983-01-01

    A conduit for high temperature transfer of molten semiconductor crystalline material consists of a composite structure incorporating a quartz transfer tube as the innermost member, with an outer thermally insulating layer designed to serve the dual purposes of minimizing heat losses from the quartz tube and maintaining mechanical strength and rigidity of the conduit at the elevated temperatures encountered. The composite structure ensures that the molten semiconductor material only comes in contact with a material (quartz) with which it is compatible, while the outer layer structure reinforces the quartz tube, which becomes somewhat soft at molten semiconductor temperatures. To further aid in preventing cooling of the molten semiconductor, a distributed, electric resistance heater is in contact with the surface of the quartz tube over most of its length. The quartz tube has short end portions which extend through the surface of the semiconductor melt and which are lef bare of the thermal insulation. The heater is designed to provide an increased heat input per unit area in the region adjacent these end portions.

  10. Repairing nerve gaps by vein conduits filled with lipoaspirate-derived entire adipose tissue hinders nerve regeneration.

    Science.gov (United States)

    Papalia, Igor; Raimondo, Stefania; Ronchi, Giulia; Magaudda, Ludovico; Giacobini-Robecchi, Maria G; Geuna, Stefano

    2013-05-01

    In spite of great recent advancements, the definition of the optimal strategy for bridging a nerve defect, especially across long gaps, still remains an open issue since the amount of autologous nerve graft material is limited while the outcome after alternative tubulization techniques is often unsatisfactory. The aim of this study was to investigate a new tubulization technique based on the employment of vein conduits filled with whole subcutaneous adipose tissue obtained by lipoaspiration. In adult rats, a 1cm-long defect of the left median nerve was repaired by adipose tissue-vein-combined conduits and compared with fresh skeletal muscle tissue-vein-combined conduits and autologous nerve grafts made by the excised nerve segment rotated by 180°. Throughout the postoperative period, functional recovery was assessed using the grasping test. Regenerated nerve samples were withdrawn at postoperative month-6 and processed for light and electron microscopy and stereology of regenerated nerve fibers. Results showed that functional recovery was significantly slower in the adipose tissue-enriched group in comparison to both control groups. Light and electron microscopy showed that a large amount of adipose tissue was still present inside the vein conduits at postoperative month-6. Stereology showed that all quantitative morphological predictors analyzed performed significantly worse in the adipose tissue-enriched group in comparison to the two control groups. On the basis of this experimental study in the rat, the use of whole adipose tissue for tissue engineering of peripheral nerves should be discouraged. Pre-treatment of adipose tissue aimed at isolating stromal vascular fraction and/or adipose derived stem/precursor cells should be considered a fundamental requisite for nerve repair.

  11. Developing International Guidelines on Volcanic Hazard Assessments for Nuclear Facilities

    Science.gov (United States)

    Connor, Charles

    2014-05-01

    Worldwide, tremendous progress has been made in recent decades in forecasting volcanic events, such as episodes of volcanic unrest, eruptions, and the potential impacts of eruptions. Generally these forecasts are divided into two categories. Short-term forecasts are prepared in response to unrest at volcanoes, rely on geophysical monitoring and related observations, and have the goal of forecasting events on timescales of hours to weeks to provide time for evacuation of people, shutdown of facilities, and implementation of related safety measures. Long-term forecasts are prepared to better understand the potential impacts of volcanism in the future and to plan for potential volcanic activity. Long-term forecasts are particularly useful to better understand and communicate the potential consequences of volcanic events for populated areas around volcanoes and for siting critical infrastructure, such as nuclear facilities. Recent work by an international team, through the auspices of the International Atomic Energy Agency, has focused on developing guidelines for long-term volcanic hazard assessments. These guidelines have now been implemented for hazard assessment for nuclear facilities in nations including Indonesia, the Philippines, Armenia, Chile, and the United States. One any time scale, all volcanic hazard assessments rely on a geologically reasonable conceptual model of volcanism. Such conceptual models are usually built upon years or decades of geological studies of specific volcanic systems, analogous systems, and development of a process-level understanding of volcanic activity. Conceptual models are used to bound potential rates of volcanic activity, potential magnitudes of eruptions, and to understand temporal and spatial trends in volcanic activity. It is these conceptual models that provide essential justification for assumptions made in statistical model development and the application of numerical models to generate quantitative forecasts. It is a

  12. Assessment of volcanic hazards, vulnerability, risk and uncertainty (Invited)

    Science.gov (United States)

    Sparks, R. S.

    2009-12-01

    A volcanic hazard is any phenomenon that threatens communities . These hazards include volcanic events like pyroclastic flows, explosions, ash fall and lavas, and secondary effects such as lahars and landslides. Volcanic hazards are described by the physical characteristics of the phenomena, by the assessment of the areas that they are likely to affect and by the magnitude-dependent return period of events. Volcanic hazard maps are generated by mapping past volcanic events and by modelling the hazardous processes. Both these methods have their strengths and limitations and a robust map should use both approaches in combination. Past records, studied through stratigraphy, the distribution of deposits and age dating, are typically incomplete and may be biased. Very significant volcanic hazards, such as surge clouds and volcanic blasts, are not well-preserved in the geological record for example. Models of volcanic processes are very useful to help identify hazardous areas that do not have any geological evidence. They are, however, limited by simplifications and incomplete understanding of the physics. Many practical volcanic hazards mapping tools are also very empirical. Hazards maps are typically abstracted into hazards zones maps, which are some times called threat or risk maps. Their aim is to identify areas at high levels of threat and the boundaries between zones may take account of other factors such as roads, escape routes during evacuation, infrastructure. These boundaries may change with time due to new knowledge on the hazards or changes in volcanic activity levels. Alternatively they may remain static but implications of the zones may change as volcanic activity changes. Zone maps are used for planning purposes and for management of volcanic crises. Volcanic hazards maps are depictions of the likelihood of future volcanic phenomena affecting places and people. Volcanic phenomena are naturally variable, often complex and not fully understood. There are

  13. Families of similar events and modes of oscillation of the conduit at Yasur volcano (Vanuatu)

    Science.gov (United States)

    Battaglia, Jean; Métaxian, Jean-Philippe; Garaebiti, Esline

    2016-08-01

    , sudden or progressive. These can be interpreted as representative of changes in the eruptive dynamics. The presence of similar EQs, especially for impulsive explosions, indicates that the source mechanism is reproducible and has a stable location for some periods. This favors a source process based on the oscillation of the conduit or oscillation of the edifice in response to the explosive decompression of gas slugs at the free surface of the conduit. Our results suggest that the seismic activity of Yasur is characterized by the presence of dominant modes of resonance of the conduit which may be influenced both by external and internal factors.

  14. Drill pipes and casings utilizing multi-conduit tubular; Flerkanals roerstreng

    Energy Technology Data Exchange (ETDEWEB)

    Curlett, H.B.

    1997-04-23

    The invention relates to a multi-conduit tubular having fluid conduits and electrical conduits, with associated surface fluid and electrical commutators, and downhole sensors for providing surface monitors with instantaneous formation data. Each tubular includes a plurality of uniform linear conduits there through, with a gasket seal plate interposed between joined tubular for assuring a high pressure seal between joined conduits. the seal plate includes an intermediate electrical connector for connecting electrical conduit connectors of one tubular to another. A coupling collar with uniform diameter internal coarse and fine threads joins the tubular ends having similar threads by differential thread action without respective tubular rotation. Each tubular end includes an inter-engaging index recess and index lug, and drive recesses and lugs for maintaining angular registry of the tubular string and for driving one drill tubular with another. A fluid commutator includes a rotating shaft with passages connected to the tubular conduits, and rotating in a manifold having annular grooves in communication with the shaft passages and external fluid sources. An adaptor couples each commutator shaft passage to one or more tubular conduits. Slip rings on a quill shaft and stationary brush means provide electrical continuity from the electrical conduit wires to surface equipment. A cross-over sub includes formation parameter sensors and telemetry equipment in a blocked off portion of a fluid conduit. An annular accumulator connected with the well bore annulus applies a pressure thereto in response to downhole sensors to change the effective density of the drill mud. The multi-conduit tubular is further adapted for use as a well casing to provide downhole access of a plurality of fluids and electrical parameter sensors. 28 figs.

  15. Volcanic tremors: Good indicators of change in plumbing systems during volcanic eruptions

    Science.gov (United States)

    Tárraga, Marta; Martí, Joan; Abella, Rafael; Carniel, Roberto; López, Carmen

    2014-03-01

    Geophysical and geochemical signals recorded during episodes of unrest preceding volcanic eruptions provide information on movements of magma inside the lithosphere and on how magma prepares to reach the surface. When the eruption ensues continuous volcanic monitoring can reveal the nature of changes occurring in the volcano's plumbing system, which may be correlated with changes in both eruption behaviour and products. During the 2011-2012 submarine eruption of El Hierro (Canary Islands), the seismic signal, surface deformation, a broad stain on the sea surface of the eruption site, and the occasional appearance of floating lava balloons and pyroclastic fragments were the main observable signs. A strong continuous tremor in the vent accompanied the eruption and varied significantly in amplitude, frequency and dynamical parameters. We analysed these variations and correlated them with changes in the distribution of earthquakes and in the petrology of the erupting magma. This enabled us to relate variations in tremors to changes in the (i) stress conditions of the plumbing system, (ii) dimensions of the conduit and vent, (iii) intensity of the explosive episodes, and (iv) rheological changes in the erupting magma. The results obtained show how the tremor signal was strongly influenced by stress changes in the host rock and in the rheological variations in the erupting magma. We conclude that the tracking of real-time syn-eruptive tremor signals via the observation of variations in plumbing systems and magma physics is a potentially effective tool for interpreting eruption dynamics, and suggest that similar variations observed in pre-eruptive tremors will have a similar origin.

  16. Aurorae and Volcanic Eruptions

    Science.gov (United States)

    2001-06-01

    Thermal-IR Observations of Jupiter and Io with ISAAC at the VLT Summary Impressive thermal-infrared images have been obtained of the giant planet Jupiter during tests of a new detector in the ISAAC instrument on the ESO Very Large Telescope (VLT) at the Paranal Observatory (Chile). . They show in particular the full extent of the northern auroral ring and part of the southern aurora. A volcanic eruption was also imaged on Io , the very active inner Jovian moon. Although these observations are of an experimental nature, they demonstrate a great potential for regular monitoring of the Jovian magnetosphere by ground-based telescopes together with space-based facilities. They also provide the added benefit of direct comparison with the terrestrial magnetosphere. PR Photo 21a/01 : ISAAC image of Jupiter (L-band: 3.5-4.0 µm) . PR Photo 21b/01 : ISAAC image of Jupiter (Narrow-band 4.07 µm) . PR Photo 21c/01 : ISAAC image of Jupiter (Narrow-band 3.28 µm) . PR Photo 21d/01 : ISAAC image of Jupiter (Narrow-band 3.21 µm) . PR Photo 21e/01 : ISAAC image of the Jovian aurorae (false-colour). PR Photo 21f/01 : ISAAC image of volcanic activity on Io . Addendum : The Jovian aurorae and polar haze. Aladdin Meets Jupiter Thermal-infrared images of Jupiter and its volcanic moon Io have been obtained during a series of system tests with the new Aladdin detector in the Infrared Spectrometer And Array Camera (ISAAC) , in combination with an upgrade of the ESO-developed detector control electronics IRACE. This state-of-the-art instrument is attached to the 8.2-m VLT ANTU telescope at the ESO Paranal Observatory. The observations were made on November 14, 2000, through various filters that isolate selected wavebands in the thermal-infrared spectral region [1]. They include a broad-band L-filter (wavelength interval 3.5 - 4.0 µm) as well as several narrow-band filters (3.21, 3.28 and 4.07 µm). The filters allow to record the light from different components of the Jovian atmosphere

  17. A novel approach to estimate the eruptive potential and probability in open conduit volcanoes.

    Science.gov (United States)

    De Gregorio, Sofia; Camarda, Marco

    2016-01-01

    In open conduit volcanoes, volatile-rich magma continuously enters into the feeding system nevertheless the eruptive activity occurs intermittently. From a practical perspective, the continuous steady input of magma in the feeding system is not able to produce eruptive events alone, but rather surplus of magma inputs are required to trigger the eruptive activity. The greater the amount of surplus of magma within the feeding system, the higher is the eruptive probability.Despite this observation, eruptive potential evaluations are commonly based on the regular magma supply, and in eruptive probability evaluations, generally any magma input has the same weight. Conversely, herein we present a novel approach based on the quantification of surplus of magma progressively intruded in the feeding system. To quantify the surplus of magma, we suggest to process temporal series of measurable parameters linked to the magma supply. We successfully performed a practical application on Mt Etna using the soil CO2 flux recorded over ten years.

  18. Circuitous embolic hemorrhagic stroke: carotid pseudoaneurysm to fetal posterior cerebral artery conduit: a case report

    Directory of Open Access Journals (Sweden)

    Hoque Romy

    2008-02-01

    Full Text Available Abstract Introduction The cervical internal carotid artery (ICA is susceptible to injury through various mechanisms, including dissection, which can lead to pseudoaneurysm formation. Pathological processes affecting the ICA, in association with an ipsilateral fetal posterior cerebral artery (PCA, resulting in parieto-occipital strokes are rarely reported. Case Presentation We present a patient with a left PCA territory, presumably embolic, stroke with early hemorrhagic transformation. The identified nidus of the embolus was a carotid artery pseudoaneurysm. Manifestations included right homonymous hemianopsia with right hemiparesis and hemisensory loss. Conclusion Our case is unique, and of clinical interest, because it illustrates both the potential anterior-posterior circulation conduit provided by a fetal origin PCA as well as the apparent early hemorrhagic transformation of embolic infarcts that can lead to further confusion from a mechanistic standpoint.

  19. Viscous Fluid Conduits as a Prototypical Nonlinear Dispersive Wave Platform

    Science.gov (United States)

    Lowman, Nicholas K.

    This thesis is devoted to the comprehensive characterization of slowly modulated, nonlinear waves in dispersive media for physically-relevant systems using a threefold approach: analytical, long-time asymptotics, careful numerical simulations, and quantitative laboratory experiments. In particular, we use this interdisciplinary approach to establish a two-fluid, interfacial fluid flow setting known as viscous fluid conduits as an ideal platform for the experimental study of truly one dimensional, unidirectional solitary waves and dispersively regularized shock waves (DSWs). Starting from the full set of fluid equations for mass and linear momentum conservation, we use a multiple-scales, perturbation approach to derive a scalar, nonlinear, dispersive wave equation for the leading order interfacial dynamics of the system. Using a generalized form of the approximate model equation, we use numerical simulations and an analytical, nonlinear wave averaging technique, Whitham-El modulation theory, to derive the key physical features of interacting large amplitude solitary waves and DSWs. We then present the results of quantitative, experimental investigations into large amplitude solitary wave interactions and DSWs. Overtaking interactions of large amplitude solitary waves are shown to exhibit nearly elastic collisions and universal interaction geometries according to the Lax categories for KdV solitons, and to be in excellent agreement with the dynamics described by the approximate asymptotic model. The dispersive shock wave experiments presented here represent the most extensive comparison to date between theory and data of the key wavetrain parameters predicted by modulation theory. We observe strong agreement. Based on the work in this thesis, viscous fluid conduits provide a well-understood, controlled, table-top environment in which to study universal properties of dispersive hydrodynamics. Motivated by the study of wave propagation in the conduit system, we

  20. Silicic magma differentiation in ascent conduits. Experimental constraints

    Science.gov (United States)

    Rodríguez, Carmen; Castro, Antonio

    2017-02-01

    Crystallization of water-bearing silicic magmas in a dynamic thermal boundary layer is reproduced experimentally by using the intrinsic thermal gradient of piston-cylinder assemblies. The standard AGV2 andesite under water-undersaturated conditions is set to crystallize in a dynamic thermal gradient of about 35 °C/mm in 10 mm length capsules. In the hotter area of the capsule, the temperature is initially set at 1200 °C and decreases by programmed cooling at two distinct rates of 0.6 and 9.6 °C/h. Experiments are conducted in horizontally arranged assemblies in a piston cylinder apparatus to avoid any effect of gravity settling and compaction of crystals in long duration runs. The results are conclusive about the effect of water-rich fluids that are expelled out the crystal-rich zone (mush), where water saturation is reached by second boiling in the interstitial liquid. Expelled fluids migrate to the magma ahead of the solidification front contributing to a progressive enrichment in the fluxed components SiO2, K2O and H2O. The composition of water-rich fluids is modelled by mass balance using the chemical composition of glasses (quenched melt). The results are the basis for a model of granite magma differentiation in thermally-zoned conduits with application of in-situ crystallization equations. The intriguing textural and compositional features of the typical autoliths, accompanying granodiorite-tonalite batholiths, can be explained following the results of this study, by critical phenomena leading to splitting of an initially homogeneous magma into two magma systems with sharp boundaries. Magma splitting in thermal boundary layers, formed at the margins of ascent conduits, may operate for several km distances during magma transport from deep sources at the lower crust or upper mantle. Accordingly, conduits may work as chromatographic columns contributing to increase the silica content of ascending magmas and, at the same time, leave behind residual mushes that

  1. Micro-seismic Signals Recorded During Fast Depressurization of Natural Volcanic Samples in a Shock Tube Apparatus

    Science.gov (United States)

    Arciniega-Ceballos, A.; Alatorre-Ibargüengoitia, M.; Dingwell, D. B.; Scheu, B.; Delgado Granados, H.; Navarrete Montesinos, M.; Richard, D.; Kueppers, U.; Lavallée, Y.

    2009-12-01

    Volcanic eruptions generate different types of seismic signals in a wide frequency bandwidth. Volcano seismology studies have dealt with analyzing seismic signals characteristics and waveform patterns in order to discriminate between source, path and site effects and reconstruct the volcanic source dynamics. The source may involve brittle failure, magma transport, magma fragmentation, bubble collapse, fluid depressurization, fluid instabilities, degassing or a combination of these processes. Given the complexity of the volcanic source dynamics and the impossibility to undertake direct observations of the source, laboratory experiments provide a promising approach to investigate the source process. In this study we present preliminary results of an experimental approach in a shock tube apparatus. The apparatus consists of two serial steel pipes separated by a diaphragm: the autoclave which represents the "source mechanism", where the samples are pressurized and fragmented, and a tank which represents a conduit. The physical mechanism consists of the slow pressurization (using Argon gas) followed by rapid depressurization of natural samples of ash (> 0.5 mm), pumice (with average porosity of 63%,) and fragmented particles of pumice. Several experiments were designed under controlled pressure conditions (ranging from 4 to 20 MPa), at room temperature. Micro-seismic signals were detected during the depressurization process using high dynamic piezo film sensors (PDF, 0.001 - 10 G Hz analog bandwidth, low impedance), fixed and distributed along the tube system. In addition, two laser beams (wavelength 532 nm) measure the speed of the ejected materials; all sensors were correlated and synchronized with two dynamic pressure sensors located at the autoclave. The resonance of the empty tube apparatus was characterized in order to distinguish between natural resonance of the tank due to the pressure shock wave and the signals generated by depressurization of the system and

  2. Volcanic Ash Nephelometer Probe Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Advanced dropsondes that could effectively be guided through atmospheric regions of interest such as volcanic plumes may enable unprecedented observations of...

  3. Volcanic Eruptions and Climate

    Science.gov (United States)

    Robock, A.

    2012-12-01

    Large volcanic eruptions inject sulfur gases into the stratosphere, which convert to sulfate aerosols with an e-folding residence time of about one year. The radiative and chemical effects of these aerosol clouds produce responses in the climate system. Observations and numerical models of the climate system show that volcanic eruptions produce global cooling and were the dominant natural cause of climate change for the past millennium, on timescales from annual to century. Major tropical eruptions produce winter warming of Northern Hemisphere continents for one or two years, while high latitude eruptions in the Northern Hemisphere weaken the Asian and African summer monsoon. The Toba supereruption 74,000 years ago caused very large climate changes, affecting human evolution. However, the effects did not last long enough to produce widespread glaciation. An episode of four large decadally-spaced eruptions at the end of the 13th century C.E. started the Little Ice Age. Since the Mt. Pinatubo eruption in the Philippines in 1991, there have been no large eruptions that affected climate, but the cumulative effects of small eruptions over the past decade had a small effect on global temperature trends. The June 13, 2011 Nabro eruption in Eritrea produced the largest stratospheric aerosol cloud since Pinatubo, and the most of the sulfur entered the stratosphere not by direct injection, but by slow lofting in the Asian summer monsoon circulation. Volcanic eruptions warn us that while stratospheric geoengineering could cool the surface, reducing ice melt and sea level rise, producing pretty sunsets, and increasing the CO2 sink, it could also reduce summer monsoon precipitation, destroy ozone, allowing more harmful UV at the surface, produce rapid warming when stopped, make the sky white, reduce solar power, perturb the ecology with more diffuse radiation, damage airplanes flying in the stratosphere, degrade astronomical observations, affect remote sensing, and affect

  4. The Zuni-Bandera Volcanic Field, NM: An Analog for Exploring Planetary Volcanic Terrains

    Science.gov (United States)

    Bleacher, J. E.; Garry, W. B.; Zimbelman, J. R.; Crumpler, L. S.; Aubele, J. C.

    2010-12-01

    The Zuni-Bandera volcanic field, near Grants, New Mexico, is comprised of volcanic deposits from several basaltic eruptions during the last million years. This vent field exhibits a diverse group of coalesced lava flows and displays well-preserved volcanic features including a’a and pahoehoe flows, collapsed lava tubes, cinder cones and low shields. The McCartys flow is a 48-km long inflated basalt flow and is the youngest in the field at around 3000 years old. Over the last three years we have used the Zuni-Bandera volcanic field, and the McCartys flow in particular, as a terrestrial analog for exploring planetary volcanic fields, and understanding the role of lava sheet inflation in flow field development. We have conducted three different styles of analog tests, 1) basic field science focused on understanding lava sheet inflation, 2) mission operations tests related to EVA design and real-time modification of traverse plans, and 3) science enabling technology tests. The Zuni-Bandera field is an ideal location for each style of analog test because it provides easy access to a diverse set of volcanic features with variable quality of preservation. However, many limitations must also be considered in order to maximize lessons learned. The McCartys flow displays well-preserved inflation plateaus that rise up to 15 m above the surrounding field. The preservation state enables textures and morphologies indicative of this process to be characterized. However, the pristine nature of the flow does not compare well with the much older and heavily modified inflated flows of Mars and the Moon. Older flows west of McCartys add value to this aspect of analog work because of their degraded surfaces, development of soil horizons, loose float, and limited exposure of outcrops, similar to what might be observed on the Moon or Mars. EVA design tests and science enabling technology tests at the Zuni-Bandera field provide the opportunity to document and interpret the relationships

  5. 75 FR 77000 - South Coast Conduit/Upper Reach Reliability Project, Santa Barbara County, CA

    Science.gov (United States)

    2010-12-10

    ... Bureau of Reclamation South Coast Conduit/Upper Reach Reliability Project, Santa Barbara County, CA... (Reclamation), the Federal lead agency, and the Cachuma Operation and Maintenance Board (COMB), the State lead agency, have prepared a Final EIS/EIR for the South Coast Conduit/Upper Reach Reliability Project (SCC...

  6. Repeated increases in blood flow, independent of exercise, enhance conduit artery vasodilator function in humans

    NARCIS (Netherlands)

    Naylor, L.H.; Carter, H.; Fitzsimons, M.G.; Cable, N.T.; Thijssen, D.H.J.; Green, D.J.

    2011-01-01

    This study aimed to determine the importance of repeated increases in blood flow to conduit artery adaptation, using an exercise-independent repeated episodic stimulus. Recent studies suggest that exercise training improves vasodilator function of conduit arteries via shear stress-mediated

  7. 78 FR 53752 - City of Sandpoint, Idaho; Notice of Preliminary Determination of a Qualifying Conduit Hydropower...

    Science.gov (United States)

    2013-08-30

    ... Qualifying Conduit Hydropower Facility and Soliciting Comments and Motions To Intervene On August 15, 2013, City of Sandpoint, Idaho filed a notice of intent to construct a qualifying conduit hydropower facility, pursuant to section 30 of the Federal Power Act, as amended by section 4 of the Hydropower Regulatory...

  8. 78 FR 61985 - City of Astoria, Oregon; Notice of Preliminary Determination of a Qualifying Conduit Hydropower...

    Science.gov (United States)

    2013-10-09

    ... Conduit Hydropower Facility and Soliciting Comments and Motions To Intervene On September 24, 2013, City of Astoria, Oregon (Astoria) filed a notice of intent to construct a qualifying conduit hydropower facility, pursuant to section 30 of the Federal Power Act, as amended by section 4 of the Hydropower...

  9. 78 FR 61987 - Corbett Water District; Notice of Preliminary Determination of a Qualifying Conduit Hydropower...

    Science.gov (United States)

    2013-10-09

    ... Conduit Hydropower Facility and Soliciting Comments and Motions To Intervene On September 23, 2013, Corbett Water District filed a notice of intent to construct a qualifying conduit hydropower facility, pursuant to section 30 of the Federal Power Act, as amended by section 4 of the Hydropower Regulatory...

  10. 78 FR 56872 - City of Barre, Vermont; Notice of Preliminary Determination of a Qualifying Conduit Hydropower...

    Science.gov (United States)

    2013-09-16

    ... Conduit Hydropower Facility and Soliciting Comments and Motions To Intervene On August 29, 2013, City of Barre, Vermont filed a notice of intent to construct a qualifying conduit hydropower facility, pursuant to section 30 of the Federal Power Act, as amended by section 4 of the Hydropower Regulatory...

  11. Urological leaks after pelvic exenterations comparing formation of colonic and ileal conduits.

    NARCIS (Netherlands)

    Teixeira, S.C.; Ferenschild, F.T.J.; Solomon, M.J.; Rodwell, L.; Harrison, J.D.; Young, J.M.; Vasilaras, A.; Eisinger, D.; Lee, P.; Byrne, C.

    2012-01-01

    BACKGROUND: The aim of this study was to assess possible risk factors for urinary leakage of a newly formed urinary conduit after a partial or total pelvic exenteration. METHODS: An analysis was conducted from prospectively collected data of patients who underwent a pelvic exenteration with conduit

  12. Cretaceous basaltic phreatomagmatic volcanism in West Texas: Maar complex at Peña Mountain, Big Bend National Park

    Science.gov (United States)

    Befus, K. S.; Hanson, R. E.; Lehman, T. M.; Griffin, W. R.

    2008-06-01

    A structurally complex succession of basaltic pyroclastic deposits produced from overlapping phreatomagmatic volcanoes occurs within Upper Cretaceous floodplain deposits in the Aguja Formation in Big Bend National Park, West Texas. Together with similar basaltic deposits recently documented elsewhere in the Aguja Formation, these rocks provide evidence for an episode of phreatomagmatic volcanism that predates onset of arc magmatism in the region in the Paleogene. At Peña Mountain, the pyroclastic deposits are ≥ 70 m thick and consist dominantly of tabular beds of lapillistone and lapilli tuff containing angular to fluidal pyroclasts of altered sideromelane intermixed with abundant accidental terrigenous detritus derived from underlying Aguja sediments. Tephra characteristics indicate derivation from phreatomagmatic explosions involving fine-scale interaction between magma and sediment in the shallow subsurface. Deposition occurred by pyroclastic fall and base-surge processes in near-vent settings; most base-surge deposits lack tractional sedimentary structures and are inferred to have formed by suspension sedimentation from rapidly decelerating surges. Complexly deformed pyroclastic strata beneath a distinct truncation surface within the succession record construction and collapse of an initial volcano, followed by a shift in the location of the conduit and excavation of another maar crater into Aguja strata nearby. Preserved portions of the margin of this second crater are defined by a zone of intense soft-sediment disruption of pyroclastic and nonvolcanic strata. U-Pb isotopic analyses of zircon grains from three basaltic bombs in the succession reveal the presence of abundant xenocrysts, in some cases with ages > 1.0 Ga. The youngest concordant analyses for all three samples yield a weighted mean age of 76.9 ± 1.2 Ma, consistent with the presence of Late Campanian vertebrate fossils in the upper Aguja Formation. We infer that the volcanism is related to the

  13. System of Volcanic activity

    Directory of Open Access Journals (Sweden)

    P. HÉDERVARI

    1972-06-01

    Full Text Available A comparison is made among the systems of B. G.
    Escher (3, of R. W. van Bemmelen (1 and that of the author (4. In this
    connection, on the basis of Esclier's classification, the terms of "constructiv
    e " and "destructive" eruptions are introduced into the author's system and
    at the same time Escher's concept on the possible relation between the depth
    of magma-chamber and the measure of the gas-pressure is discussed briefly.
    Three complementary remarks to the first paper (4 011 the subject of system
    of volcanic activity are added.

  14. The Role of Volcanic Activity in Climate and Global Change

    KAUST Repository

    Stenchikov, Georgiy L.

    2015-09-23

    Explosive volcanic eruptions are magnificent events that in many ways affect the Earth\\'s natural processes and climate. They cause sporadic perturbations of the planet\\'s energy balance, activating complex climate feedbacks and providing unique opportunities to better quantify those processes. We know that explosive eruptions cause cooling in the atmosphere for a few years, but we have just recently realized that volcanic signals can be seen in the subsurface ocean for decades. The volcanic forcing of the previous two centuries offsets the ocean heat uptake and diminishes global warming by about 30%. The explosive volcanism of the twenty-first century is unlikely to either cause any significant climate signal or to delay the pace of global warming. The recent interest in dynamic, microphysical, chemical, and climate impacts of volcanic eruptions is also excited by the fact that these impacts provide a natural analogue for climate geoengineering schemes involving deliberate development of an artificial aerosol layer in the lower stratosphere to counteract global warming. In this chapter we aim to discuss these recently discovered volcanic effects and specifically pay attention to how we can learn about the hidden Earth-system mechanisms activated by explosive volcanic eruptions. To demonstrate these effects we use our own model results when possible along with available observations, as well as review closely related recent publications.

  15. Geomagnetic imprint of the Persani volcanism

    Science.gov (United States)

    Besutiu, Lucian; Seghedi, Ioan; Zlagnean, Luminita; Atanasiu, Ligia; Popa, Razvan-Gabriel; Pomeran, Mihai; Visan, Madalina

    2016-04-01

    The Persani small volume volcanism is located in the SE corner of the Transylvanian Depression, at the north-western edge of the intra-mountainous Brasov basin. It represents the south-easternmost segment of the Neogene-Quaternary volcanic chain of the East Carpathians. The alkaline basalt monogenetic volcanic field is partly coeval with the high-K calc-alkaline magmatism south of Harghita Mountains (1-1.6 Ma). Its eruptions post-dated the calc-alkaline volcanism in the Harghita Mountains (5.3-1.6 Ma), but pre-dated the high-K calc-alkaline emissions of Ciomadul volcano (1.0-0.03 Ma). The major volcanic forms have been mapped in previous geological surveys. Still, due to the small size of the volcanoes and large extent of tephra deposits and recent sediments, the location of some vents or other volcanic structures has been incompletely revealed. To overcome this problem, the area was subject to several near-surface geophysical investigations, including paleomagnetic research. However, due to their large-scale features, the previous geophysical surveys proved to be an inappropriate approach to the volcanological issues. Therefore, during the summers of 2014 and 2015, based on the high magnetic contrast between the volcanic rocks and the hosting sedimentary formations, a detailed ground geomagnetic survey has been designed and conducted, within central Persani volcanism area, in order to outline the presence of volcanic structures hidden beneath the overlying deposits. Additionally, information on the rock magnetic properties was also targeted by sampling and analysing several outcrops in the area. Based on the acquired data, a detailed total intensity scalar geomagnetic anomaly map was constructed by using the recent IGRF12 model. The revealed pattern of the geomagnetic field proved to be fully consistent with the direction of magnetisation previously determined on rock samples. In order to enhance the signal/noise ratio, the results were further processed by

  16. Injunctions against mere conduit of information protected by copyright

    DEFF Research Database (Denmark)

    Sandfeld Jakobsen, Søren; Petersen, Clement Salung

    2011-01-01

    This paper includes an in-depth analysis of EU law and Scandinavian law on injunctions against internet access providers (IAPs) performing as mere conduit of information protected by copyright. In recent Scandinavian case law, courts have granted preliminary injunctions which have caused IAPs...... to either shut down specific internet connections allegedly used to infringe copyright or to block access to internet content, which allegedly infringed applicable copyright rules. This paper considers some significant legal challenges, which are emerging in the wake of this case law, and which should...... attract attention in all European member states. Firstly, it is shown that rules on preliminary injunctions are generally unable to safeguard the significant legitimate interests of third parties, which may be harmed by such relief, and that a proper implementation of Art. 8(3) of the Infosoc Directive...

  17. DECOVALEX-THMC Task D: Long-Term Permeability/Porosity Changes inthe EDZ and Near Field due to THM and THC Processes in Volcanic andCrystaline-Bentonite Systems, Status Report October 2005

    Energy Technology Data Exchange (ETDEWEB)

    Birkholzer, J.; Rutqvist, J.; Sonnenthal, E.; Barr, D.

    2005-11-01

    The DECOVALEX project is an international cooperativeproject initiated by SKI, the Swedish Nuclear Power Inspectorate, withparticipation of about 10 international organizations. The name DECOVALEXstands for DEvelopment of COupled models and their VALidation againstExperiments. The general goal of this project is to encouragemultidisciplinary interactive and cooperative research on modelingcoupled processes in geologic formations in support of the performanceassessment for underground storage of radioactive waste. Three multi-yearproject stages of DECOVALEX have been completed in the past decade,mainly focusing on coupled thermal-hydrological-mechanicalprocesses.Currently, a fourth three-year project stage of DECOVALEX isunder way, referred to as DECOVALEX-THMC. THMC stands for Thermal,Hydrological, Mechanical, and Chemical processes. The new project stageaims at expanding the traditional geomechanical scope of the previousDECOVALEX project stages by incorporating geochemical processes importantfor repository performance. The U.S. Department of Energy (DOE) leadsTask D of the new DECOVALEX phase, entitled "Long-termPermeability/Porosity Changes in the EDZ and Near Field due to THC andTHM Processes for Volcanic and Crystalline-Bentonite Systems." In itsleadership role for Task D, DOE coordinates and sets the direction forthe cooperative research activities of the international research teamsengaged in Task D.

  18. Large-scale tests of insulated conduit for the ITER CS coil

    Science.gov (United States)

    Reed, R. P.; Walsh, R. P.; Schutz, J. B.

    Compression-fatigue tests at 77 K were conducted on test modules of insulated Incoloy 908 conduit. To replicate the operating conditions for the ITER central solenoid (CS) full-scale coil, fatigue loads up to 3.6 MN were applied for 10 5 cycles; no mechanical breakdowns occurred. The conduits were insulated with a preimpregnated resin system, a tetraglycidyl diaminodiphenyl methane (TGDM) epoxy cured with DDS aromatic amine. The conduits were joined by vacuum-pressure impregnation with a diglycidyl ether of bisphenol-F epoxy/anhydride-cured resin system. In the 4×4 stacked-conduit test modules, the layer insulation (a high-pressure laminate of TGDM epoxy cured with DDS aromatic amine) was inserted. Periodically during the tests, breakdown voltage was measured across the conduits of both turn and layer insulation; throughout the test, breakdown voltages were at least 46 kV. The addition of a barrier increased structural and electrical reliability.

  19. Cellulose/soy protein composite-based nerve guidance conduits with designed microstructure for peripheral nerve regeneration

    Science.gov (United States)

    Gan, Li; Zhao, Lei; Zhao, Yanteng; Li, Ke; Tong, Zan; Yi, Li; Wang, Xiong; Li, Yinping; Tian, Weiqun; He, Xiaohua; Zhao, Min; Li, Yan; Chen, Yun

    2016-10-01

    Objective. The objective of this work was to develop nerve guidance conduits from natural polymers, cellulose and soy protein isolate (SPI), by evaluating the effects of cellulose/SPI film-based conduit (CSFC) and cellulose/SPI sponge-based conduit (CSSC) on regeneration of nerve defects in rats. Approach. CSFC and CSSC with the same chemical components were fabricated from cellulose and SPI. Effects of CSSC and CSFC on regeneration of the defective nerve were comparatively investigated in rats with a 10 mm long gap in sciatic nerve. The outcomes of peripheral nerve repair were evaluated by a combination of electrophysiological assessment, Fluoro-Gold retrograde tracing, double NF200/S100 immunofluorescence analysis, toluidine blue staining, and electron microscopy. The probable molecular mechanism was investigated using quantitative real-time PCR (qPCR) analysis. Main results. Compared with CSFC, CSSC had 2.69 times higher porosity and 5.07 times higher water absorption, thus ensuring much higher permeability. The nerve defects were successfully bridged and repaired by CSSC and CSFC. Three months after surgery, the CSSC group had a higher compound muscle action potential amplitude ratio, a higher percentage of positive NF200 and S100 staining, and a higher axon diameter and myelin sheath thickness than the CSFC group, showing the repair efficiency of CSSC was higher than that of CSFC. qPCR analysis indicated the mRNA levels of nerve growth factor, IL-10, IL-6, and growth-associated protein 43 (GAP-43) were higher in the CSSC group. This also indicated that there was better nerve repair with CSSC due to the higher porosity and permeability of CSSC providing a more favourable microenvironment for nerve regeneration than CSFC. Significance. A promising nerve guidance conduit was developed from cellulose/SPI sponge that showed potential for application in the repair of nerve defect. This work also suggests that nerve guidance conduits with better repair efficiency

  20. Current perspectives on energy and mass fluxes in volcanic arcs

    Science.gov (United States)

    Leeman, William; Davidson, Jon; Fischer, Tobias; Grunder, Anita; Reagan, Mark; Streck, Martin

    Volcanoes of the Pacific Ring of Fire and other convergent margins worldwide are familiar manifestations of nature's energy, account for about 25% of global volcanic outputs, dominate volcanic gas emissions to the atmosphere, and pose significant physical threats to a large human population. Yet the processes behind this prolific activity remain poorly understood.An international “State of the Arc” (SOTA) conference was held in August on the slopes of Mt. Hood, Oregon, to address current views on the energy and mass fluxes in volcanic arcs. This meeting brought together some 90 leading experts and students of subduction zones and their related magmatism.

  1. Volcan Reventador's Unusual Umbrella

    Science.gov (United States)

    Chakraborty, P.; Gioia, G.; Kieffer, S. W.

    2005-12-01

    In the past two decades, field observations of the deposits of volcanoes have been supplemented by systemmatic, and sometimes, opportunistic photographic documentation. Two photographs of the umbrella of the December 3, 2002 eruption of Volcan Reventador, Ecuador, reveal a prominently scalloped umbrella that is unlike any umbrella previously documented on a volcanic column. The material in the umbrella was being swept off a descending pyroclastic flow, and was, therefore, a co-ignimbrite cloud. We propose that the scallops are the result of a turbulent Rayleigh-Taylor (RT) instability with no precedents in volcanology. We ascribe the rare loss of buoyancy that drives this instability to the fact that the Reventador column fed on a cool co-ignimbrite cloud. On the basis of the observed wavelength of the scallops, we estimate a value for the eddy viscosity of the umbrella of 4000 ~m2/s. This value is consistent with a previously obtained lower bound (200 ~m2/s, K. Wohletz, priv. comm., 2005). We do not know the fate of the material in the umbrella subsequent to the photos. The analysis suggests that the umbrella was negatively buoyant. Field work on the co-ignimbrite deposits might reveal whether or not the material reimpacted, and if so, where and whether or not this material was involved in the hazardous flows that affected the main oil pipeline across Ecuador.

  2. Uranium series, volcanic rocks

    Science.gov (United States)

    Vazquez, Jorge A.

    2014-01-01

    Application of U-series dating to volcanic rocks provides unique and valuable information about the absolute timing of crystallization and differentiation of magmas prior to eruption. The 238U–230Th and 230Th-226Ra methods are the most commonly employed for dating the crystallization of mafic to silicic magmas that erupt at volcanoes. Dates derived from the U–Th and Ra–Th methods reflect crystallization because diffusion of these elements at magmatic temperatures is sluggish (Cherniak 2010) and diffusive re-equilibration is insignificant over the timescales (less than or equal to 10^5 years) typically associated with pre-eruptive storage of nearly all magma compositions (Cooper and Reid 2008). Other dating methods based on elements that diffuse rapidly at magmatic temperatures, such as the 40Ar/39Ar and (U–Th)/He methods, yield dates for the cooling of magma at the time of eruption. Disequilibrium of some short-lived daughters of the uranium series such as 210Po may be fractionated by saturation of a volatile phase and can be employed to date magmatic gas loss that is synchronous with volcanic eruption (e.g., Rubin et al. 1994).

  3. Retrieving eruptive vent conditions from dynamical properties of unsteady volcanic plume using high-speed imagery and numerical simulations

    Science.gov (United States)

    Tournigand, Pierre-Yves; Taddeucci, Jacopo; José Peña Fernandez, Juan; Gaudin, Damien; Sesterhenn, Jörn; Scarlato, Piergiorgio; Del Bello, Elisabetta

    2016-04-01

    Vent conditions are key parameters controlling volcanic plume dynamics and the ensuing different hazards, such as human health issues, infrastructure damages, and air traffic disruption. Indeed, for a given magma and vent geometry, plume development and stability over time mainly depend on the mass eruption rate, function of the velocity and density of the eruptive mixture at the vent, where direct measurements are impossible. High-speed imaging of eruptive plumes and numerical jet simulations were here non-dimensionally coupled to retrieve eruptive vent conditions starting from measurable plume parameters. High-speed videos of unsteady, momentum-driven volcanic plumes (jets) from Strombolian to Vulcanian activity from three different volcanoes (Sakurajima, Japan, Stromboli, Italy, and Fuego, Guatemala) were recorded in the visible and the thermal spectral ranges by using an Optronis CR600x2 (1280x1024 pixels definition, 500 Hz frame rate) and a FLIR SC655 (640x480 pixels definition, 50 Hz frame rate) cameras. Atmospheric effects correction and pre-processing of the thermal videos were performed to increase measurement accuracy. Pre-processing consists of the extraction of the plume temperature gradient over time, combined with a temperature threshold in order to remove the image background. The velocity and the apparent surface temperature fields of the plumes, and their changes over timescales of tenths of seconds, were then measured by particle image velocimetry and thermal image analysis, respectively, of the pre-processed videos. The parameters thus obtained are representative of the outer plume surface, corresponding to its boundary shear layer at the interface with the atmosphere, and may significantly differ from conditions in the plume interior. To retrieve information on the interior of the plume, and possibly extrapolate it even at the eruptive vent level, video-derived plume parameters were non-dimensionally compared to the results of numerical

  4. Numerical Simulation of the Stress and Distortion of the Fiberglass-Reinforced Plastics Crust-Stainless Steel Liner Compound Conduit

    Institute of Scientific and Technical Information of China (English)

    Hongyuan FANG; Chenglei FAN; Jianguo YANG; Ming LI; Zhen LUO; Xianzhong HOU

    2003-01-01

    A new type of compound conduit is designed and the finite element method (FEM) is applied to analyze the mechanicalperformance of a typical compound conduit. The results of the numerical simulation confirm that the distributionsof the strain

  5. Plumbing the Aquatic Conduit for Terrestrial Carbon: How far can we get with Hydrological Connectivity?

    Science.gov (United States)

    Bishop, K. H.; Campeau, A.; Billett, M. F.; Wallin, M.

    2016-12-01

    The water cycle is maddeningly difficultyto pin down with the level of detail that is desired for resolving issues about the fate of pollutants, nutrient cycling and the global carbon balance, etc. "Connectivity" is increasingly talked of in hydrology and water resources management as a way to better conceptualize how different parts of the catchment dynamically interact to influence runoff generation and water quality. Runoff is a major C flux (aquatic conduit) that is particularly sensitive to changes in climate and hydrological regimes. This paper uses three dimensions of connectivity (vertical, latitudinal and longitudinal), to plumb the sources of carbon leaving a boreal landscape via the aquatic conduit. We used the distributed sources and age of aquatic C export to help assess the role and stability of a boreal landscape in the global C cycle. We combined hydrometric data and mass balances with isotopic tracers of water and carbon, including both radiogenic (14C) and stable carbon isotopes (δ13C) of DOC, CO2 and CH4 in catchment soils and the stream network to define the connectivity of riparian, peatland and upland sources to the carbon in runoff throughout the year. The radiocarbon age of DOC, CO2 and CH4were predominantly modern, even in peat catotelm, but with localized excursions to millennial ages. The sources and processes that transport dissolved C species varied strongly with flow rates and the associated patterns of connectivity, mediated by seasonal variation that influence carbon cycling. The age of the C and other tracers exported to streams enabled us to "connect" the aquatic C exports to their origins in the mosaic of landscape elements. The effort also identified ways in which the concept of hydrological connectivity can be refined to strengthen the testing of biogeochemical hypotheses across temporal and spatial scales in specific landscapes.

  6. Numerical study of groundwater flow cycling controlled by seawater/freshwater interaction in a coastal karst aquifer through conduit network using CFPv2

    Science.gov (United States)

    Xu, Zexuan; Hu, Bill X.; Davis, Hal; Kish, Stephen

    2015-11-01

    In this study, a groundwater flow cycling in a karst springshed and an interaction between two springs, Spring Creek Springs and Wakulla Springs, through a subground conduit network are numerically simulated using CFPv2, the latest research version of MODFLOW-CFP (Conduit Flow Process). The Spring Creek Springs and Wakulla Springs, located in a marine estuary and 11 miles inland, respectively, are two major groundwater discharge spots in the Woodville Karst Plain (WKP), North Florida, USA. A three-phase conceptual model of groundwater flow cycling between the two springs and surface water recharge from a major surface creek (Lost Creek) was proposed in various rainfall conditions. A high permeable subground karst conduit network connecting the two springs was found by tracer tests and cave diving. Flow rate of discharge, salinity, sea level and tide height at Spring Creek Springs could significantly affect groundwater discharge and water stage at Wakulla Springs simultaneously. Based on the conceptual model, a numerical hybrid discrete-continuum groundwater flow model is developed using CFPv2 and calibrated by field measurements. Non-laminar flows in conduits and flow exchange between conduits and porous medium are implemented in the hybrid coupling numerical model. Time-variable salinity and equivalent freshwater head boundary conditions at the submarine spring as well as changing recharges have significant impacts on seawater/freshwater interaction and springs' discharges. The developed numerical model is used to simulate the dynamic hydrological process and quantitatively represent the three-phase conceptual model from June 2007 to June 2010. Simulated results of two springs' discharges match reasonably well to measurements with correlation coefficients 0.891 and 0.866 at Spring Creeks Springs and Wakulla Springs, respectively. The impacts of sea level rise on regional groundwater flow field and relationship between the inland springs and submarine springs are

  7. Engineering a multimodal nerve conduit for repair of injured peripheral nerve

    Science.gov (United States)

    Quigley, A. F.; Bulluss, K. J.; Kyratzis, I. L. B.; Gilmore, K.; Mysore, T.; Schirmer, K. S. U.; Kennedy, E. L.; O'Shea, M.; Truong, Y. B.; Edwards, S. L.; Peeters, G.; Herwig, P.; Razal, J. M.; Campbell, T. E.; Lowes, K. N.; Higgins, M. J.; Moulton, S. E.; Murphy, M. A.; Cook, M. J.; Clark, G. M.; Wallace, G. G.; Kapsa, R. M. I.

    2013-02-01

    Injury to nerve tissue in the peripheral nervous system (PNS) results in long-term impairment of limb function, dysaesthesia and pain, often with associated psychological effects. Whilst minor injuries can be left to regenerate without intervention and short gaps up to 2 cm can be sutured, larger or more severe injuries commonly require autogenous nerve grafts harvested from elsewhere in the body (usually sensory nerves). Functional recovery is often suboptimal and associated with loss of sensation from the tissue innervated by the harvested nerve. The challenges that persist with nerve repair have resulted in development of nerve guides or conduits from non-neural biological tissues and various polymers to improve the prognosis for the repair of damaged nerves in the PNS. This study describes the design and fabrication of a multimodal controlled pore size nerve regeneration conduit using polylactic acid (PLA) and (PLA):poly(lactic-co-glycolic) acid (PLGA) fibers within a neurotrophin-enriched alginate hydrogel. The nerve repair conduit design consists of two types of PLGA fibers selected specifically for promotion of axonal outgrowth and Schwann cell growth (75:25 for axons; 85:15 for Schwann cells). These aligned fibers are contained within the lumen of a knitted PLA sheath coated with electrospun PLA nanofibers to control pore size. The PLGA guidance fibers within the nerve repair conduit lumen are supported within an alginate hydrogel impregnated with neurotrophic factors (NT-3 or BDNF with LIF, SMDF and MGF-1) to provide neuroprotection, stimulation of axonal growth and Schwann cell migration. The conduit was used to promote repair of transected sciatic nerve in rats over a period of 4 weeks. Over this period, it was observed that over-grooming and self-mutilation (autotomy) of the limb implanted with the conduit was significantly reduced in rats implanted with the full-configuration conduit compared to rats implanted with conduits containing only an alginate

  8. DECOVALEX-THMC Project. Task D. Long-Term Permeability/Porosity Changes in the EDZ and Near Field due to THM and THC Processes in Volcanic and Crystalline-Bentonite Systems. Phase 1 Report

    Energy Technology Data Exchange (ETDEWEB)

    Birkholzer, J.; Rutqvist, J.; Sonnenthal, E. [Lawrence Berkeley National Laboratory, CA (United States); Barr, D. [Office of Repository Development, DOE (United States)

    2007-02-15

    The general goal of this project is to encourage multidisciplinary interactive and cooperative research on modeling coupled processes in geologic formations in support of the performance assessment for underground storage of radioactive waste. Three multi-year project stages of DECOVALEX have been completed in the past decade, mainly focusing on coupled thermal-hydrological-mechanical processes. Currently, a fourth three-year project stage of DECOVALEX is under way, referred to as DECOVALEX-THMC. THMC stands for Thermal, Hydrological, Mechanical, and Chemical processes. The new project stage aims at expanding the traditional geomechanical scope of the previous DECOVALEX project stages by incorporating geochemical processes important for repository performance. The U.S. Department of Energy (DOE) leads Task D of the new DECOVALEX phase, entitled 'Long-term Permeability/Porosity Changes in the EDZ and Near Field due to THC and THM Processes for Volcanic and Crystalline-Bentonite Systems.' In its leadership role for Task D, DOE coordinates and sets the direction for the cooperative research activities of the international research teams engaged in Task D. The research program developed for Task D of DECOVALEX-THMC involves geomechanical and geochemical research areas. THM and THC processes may lead to changes in hydrological properties that are important for performance because the flow processes in the vicinity of emplacement tunnels will be altered from their initial state. Some of these changes can be permanent (irreversible), in which case they persist after the thermal conditions have returned to ambient; i.e., they will affect the entire regulatory compliance period. Geochemical processes also affect the water and gas chemistry close to the waste packages, which are relevant for waste package corrosion, buffer stability, and radionuclide transport. Research teams participating in Task D evaluate long-term THM and THC processes in two generic geologic

  9. Late stage Imbrium volcanism on the Moon: Evidence for two source regions and implications for the thermal history of Mare Imbrium

    Science.gov (United States)

    Zhang, F.; Zhu, M.-H.; Zou, Y. L.

    2016-07-01

    Large open fissures or volcanic rifts can form in volcanic terrain and they are also conduits for magma ascending through the lunar crust. On the Moon, we investigated two volcanic source regions within Mare Imbrium by tracking surface morphologic features and compositional information. The Euler source region is situated at the southwest edge of the basin, while the Lambert source region lies off the south margin of the Imbrium mascon. Survey of dike surface manifestations in Euler source site suggest that dikes are the possible source of the local upper basaltic flows and the last lava phases with well developed scarps near the Euler crater, which extend northeast to the basin center. The Euler dike swarm are radial to the basin and reveal possible dike-to-conduit transition mechanism. They reveal radial subsurface fractures which may be tensional cracks preceding to the emplacement of the last stage of the mare fill. Of these, the largest dike has a more than 100 km length. The spatial arrangement of tectonic and volcanic features in Lambert source site is directly or indirectly controlled by the regional compression and extension stresses associated with flexure in response to mascon and basalt loading. In addition, compositional variation trends show a general southwest-to-northeast flooding direction of the exposed high-Ti basalts. This will have important implications for both the Imbrium basin's mare volcanism and for the thermal evolution of Mare Imbrium and the Moon.

  10. SURFACE AREA AND MICRO-ROUGHNESS OF VOLCANIC ASH PARTICLES: A case study, Acigol Volcanic Complex, Cappadocia, Central Turkiye

    Science.gov (United States)

    Ersoy, O.; Aydar, E.; Sen, E.; Atici, G.

    2009-04-01

    Every single ash particle may convey information about its own formation environment and conditions. Certain features on particles may give a hint about the fragmentation regime, the intensity of fragmentation and quantity of water that partakes in the fragmentation process, etc. On this account, this study majored in the analysis on finer pyroclastic material, namely volcanic ash particles. Here, we used volcanic ash particles from Quaternary Acigol Volcanic complex (West of Nevsehir, Cappadocia, Central Turkiye). Quaternary Acigol Volcanic complex lies between the towns of Nevsehir and Acigol. It consists of a shallow caldera, a thick pyroclastic apron, seven obsidian dome clusters, and scattered cinder cones and associated lavas (Druitt et al., 1995). The products of explosive volcanism of the region were distinguished as two main Quaternary tuffs by a recent study (Druitt et al., 1995). Samples are from ashfall beds in a sequence of intercalated pumice fall, ashfall, and ignimbrite beds. In this study in order to achieve surface properties of volcanic ash particles, surface areas and micro-roughness of ash particles were measured on digital elevation models (DEM) reconstructed from stereoscopic images acquired on Scanning Electron Microscope (SEM) at varying specimen tilt angles. Correlation between surface texture of volcanic ash particles and eruption characteristics was determined.

  11. Quaternary basaltic volcanism in the Payenia volcanic province, Argentina

    DEFF Research Database (Denmark)

    Søager, Nina

    The extensive Quaternary volcanism in the Payenia volcanic province, Mendoza, Argentina, is investigated in this study by major and trace element analyses, Sr, Nd, Hf and Pb-isotopic analyses and Zr-Hf isotope dilution data on samples from almost the entire province. The samples are mainly...... in basalts from all the studied volcanic fields in Payenia is signs of lower crustal contamination indicating assimilation of, in some cases, large amounts of trace element depleted, mafic, plagioclase-bearing rocks. The northern Payenia is dominated by backarc basalts erupted between late Pliocene to late...

  12. Scaling properties of planetary calderas and terrestrial volcanic eruptions

    Directory of Open Access Journals (Sweden)

    L. Sanchez

    2012-11-01

    Full Text Available Volcanism plays an important role in transporting internal heat of planetary bodies to their surface. Therefore, volcanoes are a manifestation of the planet's past and present internal dynamics. Volcanic eruptions as well as caldera forming processes are the direct manifestation of complex interactions between the rising magma and the surrounding host rock in the crust of terrestrial planetary bodies. Attempts have been made to compare volcanic landforms throughout the solar system. Different stochastic models have been proposed to describe the temporal sequences of eruptions on individual or groups of volcanoes. However, comprehensive understanding of the physical mechanisms responsible for volcano formation and eruption and more specifically caldera formation remains elusive. In this work, we propose a scaling law to quantify the distribution of caldera sizes on Earth, Mars, Venus, and Io, as well as the distribution of calderas on Earth depending on their surrounding crustal properties. We also apply the same scaling analysis to the distribution of interevent times between eruptions for volcanoes that have the largest eruptive history as well as groups of volcanoes on Earth. We find that when rescaled with their respective sample averages, the distributions considered show a similar functional form. This result implies that similar processes are responsible for caldera formation throughout the solar system and for different crustal settings on Earth. This result emphasizes the importance of comparative planetology to understand planetary volcanism. Similarly, the processes responsible for volcanic eruptions are independent of the type of volcanism or geographical location.

  13. Degradation properties of the electrostatic assembly PDLLA/CS/CHS nerve conduit

    Energy Technology Data Exchange (ETDEWEB)

    Xu Haixing [School of Chemical Engineering, Wuhan University of Technology, Wuhan 430070 (China); Yan Yuhua; Wan Tao; Li Shipu, E-mail: yanyuhua8@126.co [Biomedical Materials and Engineering Research Center, Wuhan University of Technology, Wuhan 430070 (China)

    2009-08-15

    A poly(d,l-lactic acid)/chondroitin sulfate/chitosan (PDLLA/CS/CHS) nerve conduit for repairing nerve defects was prepared by electrostatic assembly and the thermally induced phase separation technique. The hydrophilic characteristics of the PDLLA/CS/CHS assembly nerve conduits were improved markedly. The degradation behavior of the nerve conduit with various assembly layers was evaluated by a pH change, weight loss rate and molecular weight change. The pH of the solution of the nerve conduit could be effectively adjusted by varying the layer numbers and overcoming the acidity-caused auto-acceleration of PDLLA; the nerve conduit can retain its integrity in a phosphate buffer solution after being degraded for 3 months. After such a conduit was implanted in the rat for 3 months, obvious degradation occurred, but the regenerated nerve was integrated and it grew successfully from the proximal to distal nerve stump. All these results implied that the degradation rate of the prepared conduit can adapt to the regeneration of the peripheral nerve, which might be a new derivative of PDLLA-based biodegradable materials for repairing nerve injuries without acidity-caused irritations and acidity-induced auto-accelerating degradation behavior as shown by PDLLA.

  14. Poly(lactic-co-glycolic acid) conduit for repair of injured sciatic nerve: A mechanical analysis.

    Science.gov (United States)

    Yu, Tao; Zhao, Changfu; Li, Peng; Liu, Guangyao; Luo, Min

    2013-07-25

    Tensile stress and tensile strain directly affect the quality of nerve regeneration after bridging nerve defects by poly(lactic-co-glycolic acid) conduit transplantation and autogenous nerve grafting for sciatic nerve injury. This study collected the sciatic nerve from the gluteus maximus muscle from fresh human cadaver, and established 10-mm-long sciatic nerve injury models by removing the ischium, following which poly(lactic-co-glycolic acid) conduits or autogenous nerve grafts were transplanted. Scanning electron microscopy revealed that the axon and myelin sheath were torn, and the vessels of basilar membrane were obstructed in the poly(lactic-co-glycolic acid) conduit-repaired sciatic nerve following tensile testing. There were no significant differences in tensile tests with autogenous nerve graft-repaired sciatic nerve. Following poly(lactic-co-glycolic acid) conduit transplantation for sciatic nerve repair, tensile test results suggest that maximum tensile load, maximum stress, elastic limit load and elastic limit stress increased compared with autogenous nerve grafts, but elastic limit strain and maximum strain decreased. Moreover, the tendencies of stress-strain curves of sciatic nerves were similar after transplantation of poly(lactic-co-glycolic acid) conduits or autogenous nerve grafts. Results showed that after transplantation in vitro for sciatic nerve injury, poly(lactic-co-glycolic acid) conduits exhibited good intensity, elasticity and plasticity, indicating that poly(lactic-co-glycolic acid) conduits are suitable for sciatic nerve injury repair.

  15. Basaltic ignimbrites in monogenetic volcanism: the example of La Garrotxa volcanic field

    Science.gov (United States)

    Martí, J.; Planagumà, L. l.; Geyer, A.; Aguirre-Díaz, G.; Pedrazzi, D.; Bolós, X.

    2017-05-01

    Ignimbrites are pyroclastic density current deposits common in explosive volcanism involving intermediate and silicic magmas and in less abundance in eruptions of basaltic central and shield volcanoes. However, they are not widely described in association with monogenetic volcanism, where typical products include lava flows, scoria and lapilli fall deposits, as well as various kinds of pyroclastic density current deposits and explosion breccias. In La Garrotxa basaltic monogenetic volcanic field, part of the Neogene-Quaternary European rift system located in the northeast of the Iberian Peninsula, we have identified a particular group of pyroclastic density current deposits that show similar textural characteristics to silicic ignimbrites, indicating an overlap in transport and depositional processes. These deposits can be clearly distinguished from other pyroclastic density current deposits generated during phreatomagmatic phases that typically correspond to thinly laminated units with planar-to-cross-bedded stratification. The monogenetic ignimbrite deposits correspond to a few meters to several tens of meters thick units rich in lithic- and lapilli scoria fragments, with an abundant ash matrix, and internally massive structure, emplaced along valleys and gullies, with run-out distances up to 6 km and individual volumes ranging from 106 to 1.5 × 107 m3. The presence of flattened scoria and columnar jointing in some of these deposits suggests relatively high emplacement temperatures, coinciding with available paleomagnetic data that suggests an emplacement temperature around 450-500 °C. In this work, we describe the main characteristics of these pyroclastic deposits that were generated by a number of phreatomagmatic episodes. Comparison with similar deposits from silicic eruptions and previous examples of ignimbrites associated with basaltic volcanism allows us to classify them as `basaltic ignimbrites'. The recognition in monogenetic volcanism of such

  16. Long‐term TIR imagery processing for spatiotemporal monitoring of surface thermal features in volcanic environment: A case study in the Campi Flegrei (Southern Italy)

    National Research Council Canada - National Science Library

    Vilardo, G; Sansivero, F; Chiodini, G

    2015-01-01

    ...‐surface thermal features of an area affected by diffuse degassing. Long‐term infrared time series images were processed without taking into account atmospheric conditions and emissivity estimations...

  17. Hydrothermal Alteration of the Mt Unzen Conduit (Shimabara/Japan)

    Science.gov (United States)

    Yilmaz, T. I.; Mayer, K.; Hess, K. U.; Janots, E.; Gilg, H. A.; Dingwell, D. B.

    2016-12-01

    Investigations were carried out on hydrothermally altered coherent dacitic dykes samples from (USDP-4) drill core at Mt Unzen stratovolcano (Shimabara/Japan). XRF, XRD, EMPA, and C-O-isotope analysis led to insights concerning chemistry, mineralogy, and intensity of alteration as well as the origin of carbonate-precipitating fluids. Additionally a textural characterization of the occurring replacement features in the magma conduit zone was performed. The occurrence of the main secondary phases such as chlorite, pyrite, carbonates, and R1 (Reichweite parameter) illite-smectite indicate a weak to moderate propylitic to phyllic hydrothermal alteration. The dacitic samples of the dykes show different hydrothermal alteration features: (i) carbonate pseudomorphs after hornblende as well as core and zonal textures due to replacement of plagioclase by R1 illite-smectite, (ii) colloform banded fracture fillings and fillings in dissolution vugs, and (iii) chlorite and R1 illite-smectite in the groundmass. Carbonates in fractures comprise iron-rich dolomite solid solutions ("ankerite") and calcite. Isotopic values of d13Cvpdb = -4.59 ± 0.6‰ and d18Ovpdb = -21.73 ± 0.5‰ indicate a hydrothermal-magmatic origin for the carbonate formation. The chlorite-carbonate-pyrite index (CCPI) and the Ishikawa alteration index (AI), applied to the investigated samples show significant differences (CCPI=52.7-57.8; AI=36.1-40.6) indicating their different degree of alteration. According to Nakada et al., 2005, the C13 to C16 dykes represent the feeder dyke from the latest eruption (1991-1995) whereas C8 represents an earlier dyke feeder dyke from an older eruption. Weakest conduit alteration, which was obtained in samples C16-1-5 and C13-2-5, correlates with the alteration degree of the pristine dome rocks. Highest CCPI value was determined for sample C14-1-5 and the highest AI value was determined for sample C15-2-6. The degrees of alteration do not indicate highest alteration of the

  18. Emplacement of Volcanic Domes on Venus and Europa

    Science.gov (United States)

    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].

  19. Forgotten DJ Stent with a Large Calculus at Its Distal End in an Ileal Conduit Diversion

    Science.gov (United States)

    Puri, Anurag; Priyadarshi, Vinod; Raizada, Nivedita; Pal, Dilip Kumar

    2014-01-01

    Calculus formation in an ileal conduit following cystectomy is a known complication. Encrustation and formation of calculus may also occur over a DJ stent retained for a long period; but this is never reported in patients with conduit diversion because of close surveillance of these patients. Here we report first case of a large calculus encrusted over a forgotten DJ stent within an ileal conduit in a man who had undergone urinary diversion following radical cystectomy for carcinoma urinary bladder 8 years earlier. PMID:25215257

  20. Io. [theories concerning volcanic activity

    Science.gov (United States)

    Johnson, T. V.; Soderblom, L. A.

    1983-01-01

    A report on the continuing investigation of Io is presented. Gravitational resonance is discussed as the cause of Io's volcanism, and the volcanic activity is explained in terms of sulfur chemistry. Theories concerning the reasons for the two main types of volcanic eruptions on Io are advanced and correlated with geographical features of the satellite. The sulfur and silicate models of the calderas are presented, citing the strengths and weaknesses of each. Problems of the gravitational resonance theory of Io's heat source are then described. Finally, observations of Io planned for the Galileo mission are summarized.

  1. Amazonian volcanism inside Valles Marineris on Mars

    Science.gov (United States)

    Brož, Petr; Hauber, Ernst; Wray, James J.; Michael, Gregory

    2017-09-01

    The giant trough system of Valles Marineris is one of the most spectacular landforms on Mars, yet its origin is still unclear. Although often referred to as a rift, it also shows some characteristics that are indicative of collapse processes. For decades, one of the major open questions was whether volcanism was active inside the Valles Marineris. Here we present evidence for a volcanic field on the floor of the deepest trough of Valles Marineris, Coprates Chasma. More than 130 individual edifices resemble scoria and tuff cones, and are associated with units that are interpreted as lava flows. Crater counts indicate that the volcanic field was emplaced sometime between ∼0.4 Ga and ∼0.2 Ga. The spatial distribution of the cones displays a control by trough-parallel subsurface structures, suggesting magma ascent in feeder dikes along trough-bounding normal faults. Spectral data reveal an opaline-silica-rich unit associated with at least one of the cones, indicative of hydrothermal processes. Our results point to magma-water interaction, an environment of astrobiological interest, perhaps associated with late-stage activity in the evolution of Valles Marineris, and suggest that the floor of Coprates Chasma is promising target for the in situ exploration of Mars.

  2. Detection and estimation of volcanic eruption onset and mass flow rate using weather radar and infrasonic array

    Science.gov (United States)

    Marzano, Frank S.; Mereu, Luigi; Montopoli, Mario; Picciotti, Errico; Di Fabio, Saverio; Bonadonna, Costanza; Marchetti, Emanuele; Ripepe, Maurizio

    2015-04-01

    associated with explosive eruptions is generally produced by the rapid expansion of the gas-particle mixture within the conduit and, in consequence, it is related to the dynamics of the volume outflow and thus to the intensity of the eruption. Infrasound is closely linked to the magma fragmentation process. By combining data from ground surveys and remote sensing measurements, it is possible to gain more insights into tephra detection and distribution. Microwave scanning radars can be exploited to extract tephra spatial-temporal distribution in proximity of the volcano vent. Radar detection of ash clouds is a cumbersome problem, as their signature can be confused with that of hydrometeors. On the other hand, infrasonic arrays can provide a very accurate signal about the onset of a volcanic fountain, even though not necessarily discriminating between lava and ash eruptions. In this work we illustrate the methodology to combine microwave radar data with infrasonic measurements using, as a case study, the eruption of 2010 Eyjafjallajökull. The probabilistic detection module of the Volcanic Ash Radar Retrieval (VARR) physically-based technique is illustrated. The ash detection methodology is based on the temporal analysis of radar volumes of reflectivity and geographical information for the considered specific area. The infrasonic array signal is coupled with radar data to enhance the VARR probability of ash detection. Moreover, mass flow rates estimated from radar measurements are compared with those retrieved from infrasonic arrays and derived from simplified analytical eruption models.

  3. Cluster Analysis of vents in monogenetic volcanic fields, Lunar Crater Volcanic Field (Nevada)

    Science.gov (United States)

    Tadini, A.; Cortes, J. A.; Valentine, G. A.; Johnson, P. J.; Tibaldi, A.; Bonali, F. L.

    2012-12-01

    Monogenetic volcanic fields pose a serious risk to human activities and settlements due to their high occurrence around the world and because of the type of eruptive activity that they exhibit. The need of adequate tools to better undertake volcanic hazard assessment for volcanic fields, especially from a spatial point of view, is of key importance at the time of mitigate such hazard. Among these tools, a better understanding of the spatial distribution of cones and vents and any structural/tectonical relationship are essential to understand the plumbing system of the field and thus help to predict the likelihood location of future eruptions. In this study we have developed a spatial methodology, which is the combination of various methodologies developed for volcanic textures and other clustering goals [1,2], to study the clustering of volcanic vents and their relation with structural features from satellite images. The methodology first involves the statistical identification and removal of spatial outliers using a predictive elliptical area [2] and the generation of randomly distributed points in the same predictive area. A comparison of the Near Neighbor Distance (NND) between the generated data and the data measured in a volcanic field is used to determine whether the vents are clustered or not. If the vents are clustered, a combination of hierarchical clustering and K-means [3] is then used to identify the clusters and their related vents. Results are then further constrained with the study of lineaments and other structural features that can be affected and related with the clusters. The methodology was tested in the Lunar Crater Volcanic Field, Nevada (USA) and successfully has helped to identify tectonically controlled lineaments from those that are resultant of geomorphological processes such the drainage control imposed by the cone clusters. Theoretical approaches has been developed before to constrain the plumbing of a volcanic field [4], however these

  4. Long term volcanic hazard analysis in the Canary Islands

    Science.gov (United States)

    Becerril, L.; Galindo, I.; Laín, L.; Llorente, M.; Mancebo, M. J.

    2009-04-01

    Historic volcanism in Spain is restricted to the Canary Islands, a volcanic archipelago formed by seven volcanic islands. Several historic eruptions have been registered in the last five hundred years. However, and despite the huge amount of citizens and tourist in the archipelago, only a few volcanic hazard studies have been carried out. These studies are mainly focused in the developing of hazard maps in Lanzarote and Tenerife islands, especially for land use planning. The main handicap for these studies in the Canary Islands is the lack of well reported historical eruptions, but also the lack of data such as geochronological, geochemical or structural. In recent years, the use of Geographical Information Systems (GIS) and the improvement in the volcanic processes modelling has provided an important tool for volcanic hazard assessment. Although this sophisticated programs are really useful they need to be fed by a huge amount of data that sometimes, such in the case of the Canary Islands, are not available. For this reason, the Spanish Geological Survey (IGME) is developing a complete geo-referenced database for long term volcanic analysis in the Canary Islands. The Canarian Volcanic Hazard Database (HADA) is based on a GIS helping to organize and manage volcanic information efficiently. HADA includes the following groups of information: (1) 1:25.000 scale geologic maps, (2) 1:25.000 topographic maps, (3) geochronologic data, (4) geochemical data, (5) structural information, (6) climatic data. Data must pass a quality control before they are included in the database. New data are easily integrated in the database. With the HADA database the IGME has started a systematic organization of the existing data. In the near future, the IGME will generate new information to be included in HADA, such as volcanological maps of the islands, structural information, geochronological data and other information to assess long term volcanic hazard analysis. HADA will permit

  5. [Reconstruction of the pulmonary outflow tract without external conduit].

    Science.gov (United States)

    Yoshimura, N; Yamaguchi, M; Oka, S; Ootaki, Y; Yoshida, M; Hayashi, T; Shinkawa, T; Tei, T; Kuroe, K; Kido, S; Tsukuda, K; Oshima, Y

    2001-07-01

    Between October 1987 and December 2000, 50 patients underwent reconstruction of the pulmonary outflow tract without external conduit. The primary malformation was tetralogy of Fallot with pulmonary atresia in 37, double outlet of right ventricle in 4, corrected transposition of the great arteries in 4, transposition of the great arteries with ventricular septal defect and pulmonary stenosis in 4, and double outlet of left ventricle in 2. Mean age at operation was 7.2 years, and mean body weight was 18.3 kg. To reconstruct posterior wall of the pulmonary outflow tract, interposition of autologous pericardium was performed in 24, direct anastomosis between pulmonary trunk and ventriculotomy in 13, longitudinal incision from ventriculotomy through pulmonary trunk in 12, and interposition of left atrial appendage in 1. Anterior wall was reconstructed with monocusp valved outflow patch (MVOP). There was one hospital death and no late death. At 10 years, the freedom from reoperation for pulmonary outflow tract obstruction was 100%, and freedom from reoperation for any cause was 86.6%. Transcatheter stenting for peripheral pulmonary stenosis was performed in 6 patients 2 to 10 months after operation.

  6. Structure of a bacterial cell surface decaheme electron conduit.

    Science.gov (United States)

    Clarke, Thomas A; Edwards, Marcus J; Gates, Andrew J; Hall, Andrea; White, Gaye F; Bradley, Justin; Reardon, Catherine L; Shi, Liang; Beliaev, Alexander S; Marshall, Matthew J; Wang, Zheming; Watmough, Nicholas J; Fredrickson, James K; Zachara, John M; Butt, Julea N; Richardson, David J

    2011-06-07

    Some bacterial species are able to utilize extracellular mineral forms of iron and manganese as respiratory electron acceptors. In Shewanella oneidensis this involves decaheme cytochromes that are located on the bacterial cell surface at the termini of trans-outer-membrane electron transfer conduits. The cell surface cytochromes can potentially play multiple roles in mediating electron transfer directly to insoluble electron sinks, catalyzing electron exchange with flavin electron shuttles or participating in extracellular intercytochrome electron exchange along "nanowire" appendages. We present a 3.2-Å crystal structure of one of these decaheme cytochromes, MtrF, that allows the spatial organization of the 10 hemes to be visualized for the first time. The hemes are organized across four domains in a unique crossed conformation, in which a staggered 65-Å octaheme chain transects the length of the protein and is bisected by a planar 45-Å tetraheme chain that connects two extended Greek key split β-barrel domains. The structure provides molecular insight into how reduction of insoluble substrate (e.g., minerals), soluble substrates (e.g., flavins), and cytochrome redox partners might be possible in tandem at different termini of a trifurcated electron transport chain on the cell surface.

  7. Volcanic ash: What it is and how it forms

    Energy Technology Data Exchange (ETDEWEB)

    Heiken, G.

    1991-09-13

    There are four basic eruption processes that produce volcanic ash: (1) decompression of rising magma, gas bubble growth, and fragmentation of the foamy magma in the volcanic vent (magmatic), (2) explosive mixing of magma with ground or surface water (hydrovolcanic), (3) fragmentation of country rock during rapid expansion of steam and/or hot water (phreatic), and (4) breakup of lava fragments during rapid transport from the vent. Variations in eruption style and the characteristics of volcanic ashes produced during explosive eruptions depend on many factors, including magmatic temperature, gas content, viscosity and crystal content of the magma before eruption, the ratio of magma to ground or surface water, and physical properties of the rock enclosing the vent. Volcanic ash is composed of rock and mineral fragments, and glass shards, which is less than 2 mm in diameter. Glass shard shapes and sizes depend upon size and shape of gas bubbles present within the magma immediately before eruption and the processes responsible for fragmentation of the magma. Shards range from slightly curved, thin glass plates, which were broken from large, thin-walled spherical bubble walls, to hollow needles broken from pumiceous melts containing gas bubbles stretched by magma flow within the volcanic vent. Pumice fragments make up the coarser-grained portions of the glass fraction. Particle sizes range from meters for large blocks expelled near the volcanic vent to nanometers for fine ash and aerosol droplets within well-dispersed eruption plumes. 18 refs., 6 figs., 1 tab.

  8. Submarine Volcanic Morphology of Santorini Caldera, Greece

    Science.gov (United States)

    Nomikou, P.; Croff Bell, K.; Carey, S.; Bejelou, K.; Parks, M.; Antoniou, V.

    2012-04-01

    the area that lies between the town of Fira on the main island of Santorini and Nea Kammeni has been revealed. The lower slopes were covered with landslide debris which consisted of lava blocks mostly mantled with soft sediment. At the upper slopes an abrupt cliff face was exposed that was highly indurated by biologic material. At the top of a volcanic dome, a crater with its deepest part at 43m, its rim at about 34m with an approximately 8m diameter was also found. Shimmery water with temperatures as much as 25°C above ambient was observed there but the source of venting has not yet been found. The combination of ROV video footage and multibeam data provide new information about the main morphological characteristics of Santorini Caldera which demonstrates the intense geodynamic processes occurring at the central part of the active Hellenic volcanic arc. These results will be useful for the interpretation of understanding the offshore volcanic area and its linkage with the onshore structures.

  9. Chemo-probe into the mantle origin of the NW Anatolia Eocene to Miocene volcanic rocks: Implications for the role of, crustal accretion, subduction, slab roll-back and slab break-off processes in genesis of post-collisional magmatism

    Science.gov (United States)

    Ersoy, E. Yalçın; Palmer, Martin R.; Genç, Ş. Can; Prelević, Dejan; Akal, Cüneyt; Uysal, İbrahim

    2017-09-01

    Post-collisional Cenozoic magmatic activity in NW Anatolia produced widespread volcanism across the region. In the Biga Peninsula, in the west, medium-K calc-alkaline to ultra-K rocks with orogenic geochemical signature were emplaced at 43-15 Ma (Biga orogenic volcanic rocks; BOVR). Volcanic activity in the Central Sakarya region, to the east, is mainly restricted to 53-38 Ma, but also continued during the Early Miocene with small basaltic extrusives (Sakarya orogenic volcanic rocks; SOVR). This study presents a new set of geochemical data (whole rock major and trace elements and Sr-Nd-Pb isotopic compositions), obtained from the Cenozoic calc-alkaline volcanic rocks from these two regions. While there is considerable overlap in the emplacement time of volcanism in the two areas, the post-collisional volcanic rocks of these two regions differ in terms of their geochemical compositions: (1) the BOVR show an age-dependent increase in K and other large-ion lithophile elements (LILE), coupled with an increase in radiogenic Sr and Pb compositions from the Eocene to Miocene; whereas (2) the SOVR are characterized by more sodic compositions with lower K and less radiogenic Sr contents with respect to the BOVR, which were unchanged in Eocene and Miocene. We conclude that these geochemical features were principally related to the distinct modes of subduction-related mantle enrichment processes. We suggest that the Eocene to Miocene progressive enrichment in the BOVR mantle was related to successive subduction of oceanic and crustal materials in the western Aegean, while the SOVR mantle was dominantly enriched during the pre-collisional events. Magma generation in the western region was related to subduction roll-back processes associated with post-collisional extension. In the east, thermal perturbation of the mantle in response to asthenospheric upwelling due to slab break-off process was responsible for the magma generation. The time-dependent increase of K (and other

  10. Chemistry, mineralogy and alteration intensity of hydrothermal altered Mt Unzen conduit rocks (Shimabara/Japan)

    Science.gov (United States)

    Hess, Kai-Uwe; Yilmaz, Tim; Gilg, H. Albert; Janots, Emilie; Mayer, Klaus; Nakada, Setsuya; Dingwell, Donald

    2017-04-01

    Investigations were carried out on hydrothermally altered coherent dacitic dykes samples from (USDP-4) drill core at Mt Unzen stratovolcano (Shimabara/Japan). XRF, XRD, EMPA, C-O-isotope, hot-cathode CL and SEM analysis led to insights concerning chemistry, mineralogy, and intensity and type of alteration as well as the origin of carbonate-precipitating fluids. Additionally a textural characterization of the occurring replacement features in the volcanic conduit rocks was performed. The occurrence of the main secondary phases such as chlorite, pyrite, carbonates, and R1 (Reichweite parameter) illite-smectite and kaolinite group minerals indicate a weak to moderate propylitic to phyllic hydrothermal alteration. The dacitic samples of the dykes show different hydrothermal alteration features: (i) carbonate and chlorite pseudomorphs after hornblende as well as core and zonal textures due to replacement of plagioclase by R1 illite-smectite as well as kaolinite group minerals, (ii) colloform banded fracture fillings and fillings in dissolution vugs, and (iii) chlorite, R1 illite-smectite as well as kaolinite group minerals in the groundmass. Late chlorite veins crosscut precipitates of R1 illite-smectite as well as kaolinite group minerals. Carbonates in fractures and in pseudomorphs after hornblende comprise iron-rich dolomite solid solutions ("ankerite") and calcite. Isotopic values indicate a hydrothermal-magmatic origin for the carbonate formation. The chlorite-carbonate-pyrite index (CCPI) and the Ishikawa alteration index (AI), applied to the investigated samples show significant differences (CCPI=52.7-57.8; AI=36.1-40.6) indicating their different degree of alteration. According to Nakada et al., 2005, the C13 to C16 dykes represent the feeder dyke from the latest eruption (1991-1995) whereas C8 represents an earlier dyke feeder dyke from an older eruption. Weakest alteration, which was obtained in samples C16-1-5 and C13-2-5, correlates with the alteration

  11. MRI of the heart following implantation of a left ventricular apico-aortic conduit; Kernspintomografie zur umfassenden Untersuchung des Herzens nach Implantation von linksventrikulaeren apikoaortalen Conduits

    Energy Technology Data Exchange (ETDEWEB)

    Ruhl, K.M.; Katoh, M.; Guenther, R.W.; Krombach, G.A. [Technische Hochschule Aachen (Germany). Klinik fuer Radiologische Diagnostik; Langebartels, G.; Autschbach, R. [Technische Hochschule Aachen (Germany). Klinik fuer Thorax-, Herz- und Gefaesschirurgie

    2007-06-15

    Purpose: To investigate the potential of ECG-triggered MRI for the evaluation of postoperative anatomy and function of the heart and conduit following implantation of a left-ventricular apico-aortic conduit. Materials and Methods: 5 patients (2 female, 3 male, mean age 72.5 years) were examined using a 1.5 Tesla whole-body MRI (Gyroscan Intera, Philips Medical Systems, Best, The Netherlands) following apico-aortic conduit surgery due to severe aortic valve stenosis. The reason for performing conduit implantation instead of aortic valve replacement was the risk of injuring a bypass graft from prior coronary artery bypass surgery. Cine steady-state-free-precession (SSFP) sequences were used to assess ventricular function, navigator-gated 3D-SSFP and breath-hold, time-resolved contrast-enhanced MR angiography was used to display the postoperative anatomy, and 2D-gradient echo sequences with an inversion pulse to suppress the signal of the healthy myocardium were used to evaluate potential myocardial scarring. Flow sensitive gradient echo sequences were performed to determine the blood flow in the conduit. Results: In all patients the apico-aortic conduit proved to be open with a maximum flow velocity of 126 (+ 43) cm/s. The postoperative anatomy was able to be evaluated in all patients and perioperative myocardial infarction was able to be ruled out. The mean ejection fraction of the left ventricle was 44.2 + 6.2 % with a mean volume of 80 + 20.6 ml per heart beat. (orig.)

  12. The Medial Temporal Lobe – Conduit of Parallel Connectivity: A model for Attention, Memory, and Perception.

    Directory of Open Access Journals (Sweden)

    Brian B. Mozaffari

    2014-11-01

    Full Text Available Based on the notion that the brain is equipped with a hierarchical organization, which embodies environmental contingencies across many time scales, this paper suggests that the medial temporal lobe (MTL – located deep in the hierarchy – serves as a bridge connecting supra to infra – MTL levels. Bridging the upper and lower regions of the hierarchy provides a parallel architecture that optimizes information flow between upper and lower regions to aid attention, encoding, and processing of quick complex visual phenomenon. Bypassing intermediate hierarchy levels, information conveyed through the MTL ‘bridge’ allows upper levels to make educated predictions about the prevailing context and accordingly select lower representations to increase the efficiency of predictive coding throughout the hierarchy. This selection or activation/deactivation is associated with endogenous attention. In the event that these ‘bridge’ predictions are inaccurate, this architecture enables the rapid encoding of novel contingencies. A review of hierarchical models in relation to memory is provided along with a new theory, Medial-temporal-lobe Conduit for Parallel Connectivity (MCPC. In this scheme, consolidation is considered as a secondary process, occurring after a MTL-bridged connection, which eventually allows upper and lower levels to access each other directly. With repeated reactivations, as contingencies become consolidated, less MTL activity is predicted. Finally, MTL bridging may aid processing transient but structured perceptual events, by allowing communication between upper and lower levels without calling on intermediate levels of representation.

  13. The medial temporal lobe-conduit of parallel connectivity: a model for attention, memory, and perception.

    Science.gov (United States)

    Mozaffari, Brian

    2014-01-01

    Based on the notion that the brain is equipped with a hierarchical organization, which embodies environmental contingencies across many time scales, this paper suggests that the medial temporal lobe (MTL)-located deep in the hierarchy-serves as a bridge connecting supra- to infra-MTL levels. Bridging the upper and lower regions of the hierarchy provides a parallel architecture that optimizes information flow between upper and lower regions to aid attention, encoding, and processing of quick complex visual phenomenon. Bypassing intermediate hierarchy levels, information conveyed through the MTL "bridge" allows upper levels to make educated predictions about the prevailing context and accordingly select lower representations to increase the efficiency of predictive coding throughout the hierarchy. This selection or activation/deactivation is associated with endogenous attention. In the event that these "bridge" predictions are inaccurate, this architecture enables the rapid encoding of novel contingencies. A review of hierarchical models in relation to memory is provided along with a new theory, Medial-temporal-lobe Conduit for Parallel Connectivity (MCPC). In this scheme, consolidation is considered as a secondary process, occurring after a MTL-bridged connection, which eventually allows upper and lower levels to access each other directly. With repeated reactivations, as contingencies become consolidated, less MTL activity is predicted. Finally, MTL bridging may aid processing transient but structured perceptual events, by allowing communication between upper and lower levels without calling on intermediate levels of representation.

  14. Efficacy of nanofibrous conduits in repair of long-segment sciatic nerve defects*

    Institute of Scientific and Technical Information of China (English)

    Esmaeil Biazar; Saeed Heidari Keshel; Majid Pouya

    2013-01-01

    Our previous studies have histomorphological y confirmed that nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) conduit can be used to repair 30-mm-long sciatic nerve defects. However, the repair effects on rat behaviors remain poorly understood. In this study, we used nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) conduit and autologous sciatic nerve to bridge 30-mm-long rat sciatic nerve gaps. Within 4 months after surgery, rat sciatic nerve functional re-covery was evaluated per month by behavioral analyses, including toe out angle, toe spread anal-ysis, walking track analysis, extensor postural thrust, swimming test, open-field analysis and noci-ceptive function. Results showed that rat sciatic nerve functional recovery was similar after nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) conduit and autologous nerve grafting. These findings suggest that nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) conduit is suitable in use for repair of long-segment sciatic nerve defects.

  15. In vivo visualization of microneedle conduits in human skin using laser scanning microscopy

    Science.gov (United States)

    Bal, S.; Kruithof, A. C.; Liebl, H.; Tomerius, M.; Bouwstra, J.; Lademann, J.; Meinke, M.

    2010-03-01

    Solid microneedles enhance the penetration of drugs into the viable skin but little is known about the geometry of the conduits in vivo. Therefore, laser scanning microscopy was used to visualize the conduits of a microneedle system with needles at a length of 300 μm in 6 healthy subjects over a period of time. The model drug, a fluorescent dye was applied before and after piercing. Laser scanning microscopy was evaluated as being an excellent method to monitor the geometry and closure of the conduits over time. The used microneedle system was evaluated as suitable to enhance the transport of model drugs into the viable epidermis without bleeding and a short closure time of the conduits at the skin surface.

  16. Los volcanes y los hombres

    OpenAIRE

    García, Carmen

    2007-01-01

    Desde las entrañas de la tierra, los volcanes han creado la atmósfera, el agua de los océanos, y esculpido los relieves del planeta: son, pues, los zahoríes de la vida. Existen volcanes que los hombres explotan o cultivan, y otros sobre los cuales se han construido observatorios en los que se llevan a cabo avanzadas investigaciones científicas.

  17. Volcanic hazards and aviation safety

    Science.gov (United States)

    Casadevall, Thomas J.; Thompson, Theodore B.; Ewert, John W.; ,

    1996-01-01

    An aeronautical chart was developed to determine the relative proximity of volcanoes or ash clouds to the airports and flight corridors that may be affected by volcanic debris. The map aims to inform and increase awareness about the close spatial relationship between volcanoes and aviation operations. It shows the locations of the active volcanoes together with selected aeronautical navigation aids and great-circle routes. The map mitigates the threat that volcanic hazards pose to aircraft and improves aviation safety.

  18. Volcanic Zone, New Zealand

    Directory of Open Access Journals (Sweden)

    Graham J. Weir

    2001-01-01

    Full Text Available A conceptual model of the Taupo Volcanic Zone (TVZ is developed, to a depth of 25 km, formed from three constant density layers. The upper layer is formed from eruption products. A constant rate of eruption is assumed, which eventually implies a constant rate of extension, and a constant rate of volumetric creation in the middle and bottom layers. Tectonic extension creates volume which can accomodate magmatic intrusions. Spreading models assume this volume is distributed throughout the whole region, perhaps in vertical dykes, whereas rifting models assume the upper crust is thinned and the volume created lies under this upper crust. Bounds on the heat flow from such magmatic intrusions are calculated. Heat flow calculations are performed and some examples are provided which match the present total heat output from the TVZ of about 4200 MW, but these either have extension rates greater than the low values of about 8 ± 4 mm/a being reported from GPS measurements, or else consider extension rates in the TVZ to have varied over time.

  19. Constraining the dynamics of volcanic eruptions by characterization of pumice textures

    Directory of Open Access Journals (Sweden)

    M. Polacci

    2005-06-01

    Full Text Available We have characterized the textures of pumice clasts from Phlegraean Fields to gain insights into the conduit flow-dynamics of alkaline explosive eruptions. Vesicularities, vesicle number densities, and vesicle sizes and shapes were measured to obtain the bulk and groundmass properties of the juvenile fraction of Campanian Ignimbrite (CI and Agnano Monte Spina (AMS eruptions. The results report the coexistence of three end-member pumice types in the deposits of both eruptions, 1 microvesicular, 2 tube and 3 expanded, which differ according to clast morphology and the macro- to microscopic vesicle texture. Vesicularities (0.85-0.94 for CI, 0.51-0.91 for AMS and vesicle number densities (2-4×105 cm-2 in CI, 3×105-106 cm-2 in AMS span quite a wide range in all the three pumice types. Overall, tube pumices exhibit the highest bulk (0.89 and groundmass (CI 0.85, AMS 0.82 average vesicle volume fractions but the lowest average vesicle number densities (CI 2×105, AMS 4×105 cm-2. Comparison with textures of calc-alkaline pumices has revealed many similarities and points to a common origin and distribution of the products from both magma compositions within the volcanic conduit. In addition, the results of the textural analysis were interpreted in the light of the conduit flow modeling of Phlegraean Fields eruptions. The comparison of textural observations with results from simulations of conduit magma ascent has exhibited a good agreement between measured and numerically calculated vesicularities for both compositions, helping to constrain the overall dynamics of alkaline versus calc-alkaline eruptions.

  20. Ice nucleating properties of volcanic ash particles from the Eyjafjallajökull volcanic eruption

    Science.gov (United States)

    Kulkarni, G.; Zelenyuk, A.; Beranek, J.

    2011-12-01

    The volcanic ash from the volcanic emissions can significantly contribute to the natural source of aerosols in the atmosphere. In the vicinity and downwind of eruption site, the transported ash might have a stronger impact on the aviation industry, regional air quality, and climate. Despite the environmental significance of ash, our understanding of ash particles reacting with other volcanic plume constituents is rudimentary. In particular, the complex interactions between the water vapor and ash particles under different meteorological conditions that lead to cloud hydrometeors are poorly understood. To improve our understanding, we focus on investigating the ice formation properties of ash particles collected from the recent volcanic eruption. It was observed that the ash particles are less efficient ice nuclei compared to the natural dust particles in the deposition nucleation regime, but have similar efficiencies in the condensation freezing mode. The ice nucleated ash particles are separated from the interstitial particles, and further evaporated to understand the elemental composition, size, shape and morphology of the ice residue using the single particle mass spectrometer. The elemental composition reveals that majority of the elements are also present in the natural dust particles, but subtle differences are observed. This suggests that particle properties play an important role in the ice nucleation process.

  1. The anatomy of a cinder cone: preliminary paleomagnetic, rock magnetic, structural, and petrologic data from the La Cienega volcano, Cerros del Rio volcanic field, northern New Mexico

    Science.gov (United States)

    Petronis, M. S.; Foucher, M.; Lineline, J.; Van Wyk de Vries, B.

    2011-12-01

    The Cerros del Rio volcanic field is one of several middle Pliocene to Pleistocene basaltic volcanic fields of the axial Rio Grande Rift in central and northern New Mexico. It is a monogenetic volcanic field that comprises about 60 cinder-spatter cones, occupies ~ 700 km2, and ranges in age from 2.7 Ma to 1.1 Ma. Eruptive centers are typically central vent volcanoes, ranging from low-relief shields to steep-sided, breached cinder and spatter cone remnants. They represent short eruptive events that likely were derived from rapidly evolving reservoir-conduit systems. Mining activity has exposed the volcanic plumbing system of the Cienega Mine cinder cone, just west of Santa Fe, NM. Here, geologists from France and USA have been investigating the exposed roots of this eviscerated Pliocene volcano to investigate magma conduit geometry, magma flow structures, and eruption patterns. We are testing models for magma transport and volcano construction using a variety of field and laboratory tools. Common models of volcanic construction envision the magma feeder as a dike or pipe-like conduit transporting molten rock from a deep reservoir to the eruptive vent. We posit that small volcanic pluming systems are inherently more complex and actually involve numerous feeder geometries throughout the volcano lifespan. Our preliminary work suggests that the simple exteriors of some cinder cones hide a long life and complex history, both of which would change the appreciation of the related volcanic hazards in active systems. The Cienega Mine cinder cone consists of several meter- to decimeter-wide intrusions that connect to eruptive centers. These intrusions show a continuity of brittle to ductile structures from their margins to interiors. We have collected samples across each intrusion as well as along strike for anisotropy of magnetic susceptibility (AMS) and petrographic analysis in order to establish magma flow patterns. AMS results yield a remarkably consistent dataset that

  2. A cryptoendolithic community in volcanic glass.

    Science.gov (United States)

    Herrera, Aude; Cockell, Charles S; Self, Stephen; Blaxter, Mark; Reitner, Joachim; Thorsteinsson, Thorsteinn; Arp, Gernot; Dröse, Wolfgang; Tindle, Andrew G

    2009-05-01

    Fluorescent in situ hybridization (FISH) and 16S rDNA analysis were used to characterize the endolithic colonization of silica-rich rhyolitic glass (obsidian) in a barren terrestrial volcanic environment in Iceland. The rocks were inhabited by a diverse eubacterial assemblage. In the interior of the rock, we identified cyanobacterial and algal 16S (plastid) sequences and visualized phototrophs by FISH, which demonstrates that molecular methods can be used to characterize phototrophs at the limits of photosynthetically active radiation (PAR). Temperatures on the surface of the dark rocks can exceed 40 degrees C but are below freezing for much of the winter. The rocks effectively shield the organisms within from ultraviolet radiation. Although PAR sufficient for photosynthesis cannot penetrate more than approximately 250 mum into the solid rock, the phototrophs inhabit cavities; and we hypothesize that by weathering the rock they may contribute to the formation of cavities in a feedback process, which allows them to acquire sufficient PAR at greater depths. These observations show how pioneer phototrophs can colonize the interior of volcanic glasses and rocks, despite the opaque nature of these materials. The data show that protected microhabitats in volcanic rocky environments would have been available for phototrophs on early Earth.

  3. Poly(lactic-co-glycolic acid) conduit for repair of injured sciatic nerve A mechanical analysis*

    Institute of Scientific and Technical Information of China (English)

    Tao Yu; Changfu Zhao; Peng Li; Guangyao Liu; Min Luo

    2013-01-01

    Tensile stress and tensile strain directly affect the quality of nerve regeneration after bridging nerve defects by poly(lactic-co-glycolic acid) conduit transplantation and autogenous nerve grafting for sciatic nerve injury. This study col ected the sciatic nerve from the gluteus maximus muscle from fresh human cadaver, and established 10-mm-long sciatic nerve injury models by removing the ischium, fol owing which poly(lactic-co-glycolic acid) conduits or autogenous nerve grafts were transplanted. Scanning electron microscopy revealed that the axon and myelin sheath were torn, and the vessels of basilar membrane were obstructed in the poly(lactic-co-glycolic acid) con-duit-repaired sciatic nerve fol owing tensile testing. There were no significant differences in tensile tests with autogenous nerve graft-repaired sciatic nerve. Fol owing poly(lactic-co-glycolic acid) conduit transplantation for sciatic nerve repair, tensile test results suggest that maximum tensile load, maximum stress, elastic limit load and elastic limit stress increased compared with autogen-ous nerve grafts, but elastic limit strain and maximum strain decreased. Moreover, the tendencies of stress-strain curves of sciatic nerves were similar after transplantation of poly(lactic-co-glycolic acid) conduits or autogenous nerve grafts. Results showed that after transplantation in vitro for sciatic nerve injury, poly(lactic-co-glycolic acid) conduits exhibited good intensity, elasticity and plasticity, indicating that poly(lactic-co-glycolic acid) conduits are suitable for sciatic nerve injury repair.

  4. MR and CT imaging of pulmonary valved conduits in children and adolescents: normal appearance and complications

    Energy Technology Data Exchange (ETDEWEB)

    Tenisch, Estelle V.; Alamo, Leonor T.; Gudinchet, Francois [Lausanne University Hospital, Department of Medical Imaging, Lausanne (Switzerland); Sekarski, Nicole [Lausanne University Hospital, Department of Pediatrics, Lausanne (Switzerland); Hurni, Michel [Lausanne University Hospital, Department of Cardiovascular Surgery, Lausanne (Switzerland)

    2014-12-15

    The Contegra registered is a conduit made from the bovine jugular vein and then interposed between the right ventricle and the pulmonary artery. It is used for cardiac malformations in the reconstruction of right ventricular outflow tract. To describe both normal and pathological appearances of the Contegra registered in radiological imaging, to describe imaging of complications and to define the role of CT and MRI in postoperative follow-up. Forty-three examinations of 24 patients (17 boys and 7 girls; mean age: 10.8 years old) with Contegra registered conduits were reviewed. Anatomical description and measurements of the conduits were performed. Pathological items examined included stenosis, dilatation, plicature or twist, thrombus or vegetations, calcifications and valvular regurgitation. Findings were correlated to the echographic gradient through the conduit when available. CT and MR work-up showed Contegra registered stenosis (n = 12), dilatation (n = 9) and plicature or twist (n = 7). CT displayed thrombus or vegetations in the Contegra registered in three clinically infected patients. Calcifications of the conduit were present at CT in 12 patients and valvular regurgitation in three patients. The comparison between CT and/or MR results showed a good correlation between the echographic gradient and the presence of stenosis in the Contegra registered. CT and MR bring additional information about permeability and postoperative anatomy especially when echocardiography is inconclusive. Both techniques depict the normal appearance of the conduit, and allow comparison and precise evaluation of changes in the postoperative follow-up. (orig.)

  5. Conduit Magma Storage during the 800 BP Quilotoa Eruption, Ecuador

    Science.gov (United States)

    Ort, M. H.; Cashman, K. V.; Di Muro, A.; Best, J. A.; Rosi, M.; Mothes, P. A.; Bustillos, J.

    2013-12-01

    The 800 BP eruption of Quilotoa produced two large ignimbrites, U1 (~5.8 km3 DRE) and U3 (~1.8 km3 DRE). These eruptions were separated by a series of much smaller eruptions over one to several weeks, as inferred from 1) the intercalation of secondary pyroclastic and debris flow deposits between U1 and U3, 2) deposits from phreatic explosions from the U1 ignimbrite surface, 3) oxidation of the upper 2 m of U1, and 4) a lack of erosion of the U1 surface. Why did the main phase of the eruption (U1) stall when eruptable magma was available? How did explosive activity stop and restart? We address these questions by examining deposits (U2) emplaced during the 'hiatus' that provide information on the conditions in the conduit and vent area between explosive episodes. The lowest sub-unit, U2a, forms a series of pumiceous surge deposits found only within 5 km of the crater rim. U2b is a vitric-poor, crystal- and lithic-rich fall deposit distributed to about 15 km from the crater. U2c is a thin gray fine ash containing 2-5-mm-diameter rhyolite lapilli that is present within 6 km of the vent. Similar lapilli also occur in the lowermost few centimeters of U3 and appear to be from a dome that exploded as the new magma arrived at the surface; their presence as small ballistic fragments ties U2c to lowermost U3 in time. U2a appears to have been emplaced by episodic surges and weak fallout plumes, whereas U2b and U2c were deposited from a series of sustained eruption columns. Moreover, the lack of U2b grain-size variation with distance suggests that the grain size was determined at the vent, not by transport. FTIR analysis of CO2 and H2O in melt inclusions (MIs) indicates that a deep magma chamber (>400 MPa; ~12 km) fed U1. U2a and U2b MIs plot along vapor isopleths, suggesting equilibration at pressures to about 300 MPa as CO2 outgassed. U2b MIs have lower CO2 than U2a, perhaps indicating continued degassing during the 'hiatus'. MIs from the lower few centimeters of U3 lie along

  6. Polytetrafluoroethylene pulmonary valve conduit implantation for chronic pulmonary insufficiency.

    Science.gov (United States)

    Quintessenza, James A

    2014-12-01

    Pulmonary valve replacement in patients with congenital cardiac disease is now being performed with more liberal indications in light of the data that chronic pulmonary insufficiency is not a benign lesion. The beneficial effects of valve replacement with low operative mortality and morbidity support this approach. Many options exist for a pulmonary valve prosthesis, which underscores the fact that there is no ideal valve available. Our efforts are focussed around a synthetic valve that avoids the bio-degeneration of a bio-prosthesis and avoids the need for life-long coumadin. We developed a bicuspid (bileaflet) polytetrafluoroethylene valve design, which has now gone through three major revisions in >200 patients over 14 years. We began the experience utilising a polytetrafluoroethylene hand-sewn bicuspid valve in the right ventricular outflow tract, initially using 0.6 mm and more recently 0.1 mm polytetrafluoroethylene. The 0.1 mm thickness material functions well as a leaflet, maintaining a relatively thin and flexible nature. It does not calcify or initiate thromboses at least for the first several years. We identified issues with dehiscence of the leaflet from the right ventricular outflow tract muscle, especially in the larger, potentially expansive right ventricular outflow tracts, and this prompted our latest design change to place the valve within a polytetrafluoroethylene tube. This current version of the polytetrafluoroethylene valve conduit has excellent short-to-intermediate-term function. Further follow-up is necessary to determine late durability and life-long valve-related procedural risk for our patients.

  7. The Himalayas: barrier and conduit for gene flow.

    Science.gov (United States)

    Gayden, Tenzin; Perez, Annabel; Persad, Patrice J; Bukhari, Areej; Chennakrishnaiah, Shilpa; Simms, Tanya; Maloney, Trisha; Rodriguez, Kristina; Herrera, Rene J

    2013-06-01

    The Himalayan mountain range is strategically located at the crossroads of the major cultural centers in Asia, the Middle East and Europe. Although previous Y-chromosome studies indicate that the Himalayas served as a natural barrier for gene flow from the south to the Tibetan plateau, this region is believed to have played an important role as a corridor for human migrations between East and West Eurasia along the ancient Silk Road. To evaluate the effects of the Himalayan mountain range in shaping the maternal lineages of populations residing on either side of the cordillera, we analyzed mitochondrial DNA variation in 344 samples from three Nepalese collections (Newar, Kathmandu and Tamang) and a general population of Tibet. Our results revealed a predominantly East Asian-specific component in Tibet and Tamang, whereas Newar and Kathmandu are both characterized by a combination of East and South Central Asian lineages. Interestingly, Newar and Kathmandu harbor several deep-rooted Indian lineages, including M2, R5, and U2, whose coalescent times from this study (U2, >40 kya) and previous reports (M2 and R5, >50 kya) suggest that Nepal was inhabited during the initial peopling of South Central Asia. Comparisons with our previous Y-chromosome data indicate sex-biased migrations in Tamang and a founder effect and/or genetic drift in Tamang and Newar. Altogether, our results confirm that while the Himalayas acted as a geographic barrier for human movement from the Indian subcontinent to the Tibetan highland, it also served as a conduit for gene flow between Central and East Asia.

  8. Photofabricated gelatin-based nerve conduits: nerve tissue regeneration potentials.

    Science.gov (United States)

    Gámez, Eduardo; Goto, Yoshinobu; Nagata, Kengo; Iwaki, Toru; Sasaki, Tomio; Matsuda, Takehisa

    2004-01-01

    There is a strong demand for development of nerve guide conduit with prompt nerve regeneration potential for injury-induced nerve defect. Prior to study on nerve tissue engineering using Schwann cells or nerve stem cells, the effectiveness of photofabricated scaffolds based on photocurable gelatin was examined. This study describes the evaluation of in vivo nerve tissue regeneration potentials of three custom-designed and -fabricated prostheses (inner diameter, 1.2 mm; outer diameter, 2.4 mm; wall thickness, 0.60 mm; and length, 15 mm) made of photocured gelatin: a plain photocured gelatin tube (model I), a photocured gelatin tube packed with bioactive substances (laminin, fibronectin, and nerve growth factor) coimmobilized in a photocured gelatin rod (model II), and a photocured gelatin tube packed with bioactive substances coimmobilized in multifilament fibers (model III). These prostheses were implanted between the proximal and distal stumps 10 mm of the dissected right sciatic nerve of 70 adult male Lewis rats for up to 1 year. The highest regenerative potentials were found using the model III prosthesis, followed by the model II prosthesis. Markedly retarded neural regeneration was observed using the model I prosthesis. These were evaluated from the viewpoints of functional recovery, electrophysiological responses, and tissue morphological regeneration. The significance of the synergistic cooperative functions of multifilaments, which serve as a platform that provides contact guidance to direct longitudinal cell movement and tissue ingrowth and as a cell adhesive matrix with high surface area, and immobilized bioactive substances, which enhance nerve regeneration via biological stimulation, is discussed.

  9. Modern analogues for Miocene to Pleistocene alkali basaltic phreatomagmatic fields in the Pannonian Basin: "soft-substrate" to "combined" aquifer controlled phreatomagmatism in intraplate volcanic fields Research Article

    Science.gov (United States)

    Németh, Károly; Cronin, Shane; Haller, Miguel; Brenna, Marco; Csillag, Gabor

    2010-09-01

    The Pannonian Basin (Central Europe) hosts numerous alkali basaltic volcanic fields in an area similar to 200 000 km2. These volcanic fields were formed in an approximate time span of 8 million years producing smallvolume volcanoes typically considered to be monogenetic. Polycyclic monogenetic volcanic complexes are also common in each field however. The original morphology of volcanic landforms, especially phreatomagmatic volcanoes, is commonly modified. by erosion, commonly aided by tectonic uplift. The phreatomagmatic volcanoes eroded to the level of their sub-surface architecture expose crater to conduit filling as well as diatreme facies of pyroclastic rock assemblages. Uncertainties due to the strong erosion influenced by tectonic uplifts, fast and broad climatic changes, vegetation cover variations, and rapidly changing fluvio-lacustrine events in the past 8 million years in the Pannonian Basin have created a need to reconstruct and visualise the paleoenvironment into which the monogenetic volcanoes erupted. Here phreatomagmatic volcanic fields of the Miocene to Pleistocene western Hungarian alkali basaltic province have been selected and compared with modern phreatomagmatic fields. It has been concluded that the Auckland Volcanic Field (AVF) in New Zealand could be viewed as a prime modern analogue for the western Hungarian phreatomagmatic fields by sharing similarities in their pyroclastic successions textures such as pyroclast morphology, type, juvenile particle ratio to accidental lithics. Beside the AVF two other, morphologically more modified volcanic fields (Pali Aike, Argentina and Jeju, Korea) show similar features to the western Hungarian examples, highlighting issues such as preservation potential of pyroclastic successions of phreatomagmatic volcanoes.

  10. DECOVALEX-THMC Project. Task D. Long-Term Permeability/Porosity Changes in the EDZ and Near Field due to THM and THC Processes in Volcanic and Crystalline-Bentonite Systems. Phase 1 Report

    Energy Technology Data Exchange (ETDEWEB)

    Birkholzer, J.; Rutqvist, J.; Sonnenthal, E. [Lawrence Berkeley National Laboratory, CA (United States); Barr, D. [Office of Repository Development, DOE (United States)

    2007-02-15

    The general goal of this project is to encourage multidisciplinary interactive and cooperative research on modeling coupled processes in geologic formations in support of the performance assessment for underground storage of radioactive waste. Three multi-year project stages of DECOVALEX have been completed in the past decade, mainly focusing on coupled thermal-hydrological-mechanical processes. Currently, a fourth three-year project stage of DECOVALEX is under way, referred to as DECOVALEX-THMC. THMC stands for Thermal, Hydrological, Mechanical, and Chemical processes. The new project stage aims at expanding the traditional geomechanical scope of the previous DECOVALEX project stages by incorporating geochemical processes important for repository performance. The U.S. Department of Energy (DOE) leads Task D of the new DECOVALEX phase, entitled 'Long-term Permeability/Porosity Changes in the EDZ and Near Field due to THC and THM Processes for Volcanic and Crystalline-Bentonite Systems.' In its leadership role for Task D, DOE coordinates and sets the direction for the cooperative research activities of the international research teams engaged in Task D. The research program developed for Task D of DECOVALEX-THMC involves geomechanical and geochemical research areas. THM and THC processes may lead to changes in hydrological properties that are important for performance because the flow processes in the vicinity of emplacement tunnels will be altered from their initial state. Some of these changes can be permanent (irreversible), in which case they persist after the thermal conditions have returned to ambient; i.e., they will affect the entire regulatory compliance period. Geochemical processes also affect the water and gas chemistry close to the waste packages, which are relevant for waste package corrosion, buffer stability, and radionuclide transport. Research teams participating in Task D evaluate long-term THM and THC processes in two generic geologic

  11. Characteristics and biocompatibility of a biodegradable genipin-cross-linked gelatin/β-tricalcium phosphate reinforced nerve guide conduit.

    Science.gov (United States)

    Yang, Yi-Chin; Shen, Chiung-Chyi; Huang, Tsung-Bin; Chang, Shun-Hsung; Cheng, Hsu-Chen; Liu, Bai-Shuan

    2010-10-01

    To modulate the mechanical properties of nerve guide conduit for surgical manipulation, this study develops a biodegradable composite containing genipin cross-linked gelatin annexed with β-tricalcium phosphate ceramic particles as a nerve guide material. The conduit was dark bluish and round with a rough and compact outer surface compared to the genipin cross-linked gelatin conduit (without β-tricalcium phosphate). Water uptake and swelling tests indicate that the conduit noticeably increases the stability in water, and the hydrated conduit does not collapse and stenose. The conduit has a sufficiently high level of mechanical properties to serve as a nerve guide. After subcutaneous implantation on the dorsal side of a rat, the degraded conduit only evokes a mild tissue response, and the formation of a very thin fibrous capsule surrounds the conduit. This paper assesses the effectiveness of the conduit as a guidance channel when we use it to repair a 10 mm gap in the rat's sciatic nerve. The experimental results show no gross inflammatory reactions of the peripheral nerve tissues at the implantation site in either group. In overall gross examination, the diameter of the intratubular and newly formed nerve fibers in the conduits exceeds that of the silicone tubes during the implantation period. The quantitative results indicate the superiority of the conduits over the silicone tubes. This study microscopically observes the nerve regeneration in the tissue section at the middle region of all implanted conduits. Therefore, the histomorphometric assessment demonstrates that the conduit could be a candidate for peripheral nerve repair.

  12. Geophysical surveys of the Joya Honda maar (México) and surroundings; volcanic implications

    Science.gov (United States)

    López Loera, Héctor; Aranda-Gómez, José Jorge; Arzate, Jorge A.; Molina-Garza, Roberto Stanley

    2008-03-01

    Joya Honda (JH) is a Quaternary maar excavated in Mesozoic limestone. It is located in central Mexico and belongs to the Ventura volcanic field (VVF), which is composed by cinder cones and maars made of intraplate-type mafic alkalic rocks. Volcanoes in the region form ˜ N20W lineaments, roughly parallel to a regional set of normal faults, but there is no obvious relation between these faults and vent distribution in the exposed geology around the maar. The volcanic rock volume is small in the VVF, and most volcanoes and their products are scattered in a region where outcrops are dominated by limestone. The near-vent tephra associated to the JH maar lies north of the crater. This relation suggests that the crater was formed by directed hydromagmatic explosions and may indicate an inclined volcanic conduit near the surface. The tephra stratigraphy suggests that the initial explosions were relatively dry and the amount of water increased during the maar forming eruption. Therefore, the existing model of the maar-diatreme formation may not be applicable to Joya Honda as it requires the formation of a cone of depression in the aquifer and deepening of the focii of the explosions as the crater and underlying diatreme grew. Thus, it is unlikely that there is a diatreme below Joya Honda. Aeromagnetic data shows a boundary between two regional magnetic domains near the elongated volcanic cluster of the VVF. The boundary is straight, with a distinct kink, from NE- to NW-trend, near JH. The limit between the domains is interpreted as fault contacts between mid-Tertiary volcanic rocks and marine Mesozoic sedimentary rocks. Hence, magma ascent in the area may have been facilitated by fractures near the surface. Magnetic and gravimetric ground surveys show that the anomalies associated with the maar are not centered in the crater, which could be consistent with an inclined volcanic conduit. A magnetic profile measured on exposed limestone across the volcanic lineament failed to

  13. Quaternary basaltic volcanism in the Payenia volcanic province, Argentina

    DEFF Research Database (Denmark)

    Søager, Nina

    primitive basalts and trachybasalts but also more evolved samples from the retroarc region and the larger volcanoes Payún Matrú and Payún Liso are presented. The samples cover a broad range of compositions from intraplate lavas similar to ocean island basalts to arc andesites. A common feature found...... Pleistocene times. These basalts mark the end of a period of shallow subduction of the Nazca slab beneath the Payenia province and volcanism in the Nevado volcanic field apparently followed the downwarping slab in a north-northwest direction ending in the Northern Segment. The northern Payenia basalts...... the literature. The Nevado basalts have been modelled by 4-10 % melting of a primitive mantle added 1-5 % upper continental crust. In the southern Payenia province, intraplate basalts dominate. The samples from the Payún Matrú and Río Colorado volcanic fields are apparently unaffected by the subducting slab...

  14. Fluid-magmatic systems and volcanic centers in Northern Caucasus

    Science.gov (United States)

    Sobisevich, Alexey L.; Masurenkov, Yuri P.; Pouzich, Irina N.; Laverova, Ninel I.

    2013-04-01

    The central segment of Alpine mobile folded system and the Greater Caucasus is considered with respect to fluid-magmatic activity within modern and Holocene volcanic centers. A volcanic center is a combination of volcanoes, intrusions, and hydrothermal features supported by endogenous flow of matter and energy localised in space and steady in time; responsible for magma generation and characterized by structural representation in the form of circular dome and caldera associations. Results of complimentary geological and geophysical studies carried out in the Elbrus volcanic area and the Pyatogorsk volcanic center are presented. The deep magmatic source and the peripheral magmatic chamber of the Elbrus volcano are outlined via comparative analysis of geological and experimental geophysical data (microgravity studies, magneto-telluric profiling, temperature of carbonaceous mineral waters). It has been determined that the peripheral magmatic chamber and the deep magmatic source of the volcano are located at depths of 0-7 and 20-30 km below sea level, respectively, and the geothermal gradient beneath the volcano is 100°C/km. In this study, analysis of processes of modern heat outflux produced by carbonaceous springs in the Elbrus volcanic center is carried out with respect to updated information about spatial configuration of deep fluid-magmatic structures of the Elbrus volcano. It has been shown, that degradation of the Elbrus glaciers throughout the historical time is related both to climatic variations and endogenic heat. The stable fast rate of melting for the glaciers on the volcano's eastern slope is of theoretical and practical interest as factors of eruption prognosis. The system approach to studying volcanism implies that events that seem to be outside the studied process should not be ignored. This concerns glaciers located in the vicinity of volcanoes. The crustal rocks contacting with the volcanism products exchange matter and energy between each other

  15. Laboratory simulations of volcanic ash charging and conditions for volcanic lightning on Venus

    Science.gov (United States)

    Airey, Martin; Warriner-Bacon, Elliot; Aplin, Karen

    2017-04-01

    Lightning may be important in the emergence of life on Earth and elsewhere, as significant chemical reactions occur in the superheated region around the lightning channel. This, combined with the availability of phosphates in volcanic clouds, suggests that volcanic lightning could have been the catalyst for the formation of biological compounds on the early Earth [1]. In addition to meteorological lightning, volcanic activity also generates electrical discharges within charged ash plumes, which can be a significant contributor to atmospheric electricity on geologically active planets. The physical properties of other planetary atmospheres, such as that of Venus, have an effect on the processes that lead to the generation of volcanic lightning. Volcanism is known to have occurred on Venus in the past, and recent observations made by ESA's Venus Express satellite have provided evidence for currently active volcanism [2-4], and lightning discharges [e.g. 5]. Venusian lightning could potentially be volcanic in origin, since no meteorological mechanisms are known to separate charge effectively in its clouds [6]. The hunt for further evidence for lightning at Venus is ongoing, for example by means of the Lightning and Airglow Camera (LAC) [7] on Akatsuki, the current JAXA mission at Venus. Our laboratory experiments simulate ash generation and measure electrical charging of the ash under typical atmospheric conditions on Earth and Venus. The study uses a 1 litre chamber, which, when pressurised and heated, can simulate the high-pressure, high-temperature, carbon dioxide-dominated atmosphere of Venus at 10 km altitude ( 5 MPa, 650 K). A key finding of previous work [8] is that ash plume-forming eruptions are more likely to occur at higher altitudes such as these on Venus. The chamber contains temperature/pressure monitoring and logging equipment, a rock collision apparatus (based on [9]) to generate the charged rock fragments, and charge measurement electrodes connected

  16. Atmospheric chemistry in volcanic plumes.

    Science.gov (United States)

    von Glasow, Roland

    2010-04-13

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

  17. Climatic impact of volcanic eruptions

    Science.gov (United States)

    Rampino, Michael R.

    1991-01-01

    Studies have attempted to 'isolate' the volcanic signal in noisy temperature data. This assumes that it is possible to isolate a distinct volcanic signal in a record that may have a combination of forcings (ENSO, solar variability, random fluctuations, volcanism) that all interact. The key to discovering the greatest effects of volcanoes on short-term climate may be to concentrate on temperatures in regions where the effects of aerosol clouds may be amplified by perturbed atmospheric circulation patterns. This is especially true in subpolar and midlatitude areas affected by changes in the position of the polar front. Such climatic perturbation can be detected in proxy evidence such as decrease in tree-ring widths and frost rings, changes in the treeline, weather anomalies, severity of sea-ice in polar and subpolar regions, and poor grain yields and crop failures. In low latitudes, sudden temperature drops were correlated with the passage overhead of the volcanic dust cloud (Stothers, 1984). For some eruptions, such as Tambora, 1815, these kinds of proxy and anectdotal information were summarized in great detail in a number of papers and books (e.g., Post, 1978; Stothers, 1984; Stommel and Stommel, 1986; C. R. Harrington, in press). These studies lead to the general conclusion that regional effects on climate, sometimes quite severe, may be the major impact of large historical volcanic aerosol clouds.

  18. Evolution of karst conduit networks in transition from pressurised flow to free surface flow

    Science.gov (United States)

    Perne, M.; Covington, M. D.; Gabrovšek, F.

    2014-06-01

    We present a novel modelling approach to study the evolution of conduit networks in soluble rocks. Unlike the models presented so far, the model allows a transition from pressurised (pipe) flow to a free surface (open channel) flow in evolving discrete conduit networks. It calculates flow, solute transport and dissolutional enlargement within each time step and steps through time until a stable flow pattern establishes. The flow in each time step is calculated by calling the EPA Storm Water Management Model (EPA SWMM), which efficiently solves the 1-D Saint Venant equations in a network of conduits. We present several cases with low dip and sub-vertical networks to demonstrate mechanisms of flow pathway selection. In low dip models the inputs were randomly distributed to several junctions. The evolution of pathways progresses upstream: initially pathways linking outlets to the closest inputs evolve fastest because the gradient along these pathways is largest. When a pathway efficiently drains the available recharge, the head drop along the pathway attracts flow from the neighbouring upstream junctions and new connecting pathways evolve. The mechanism progresses from the output boundary inwards until all inputs are connected to the stable flow system. In the pressurised phase, each junction is drained by at least one conduit, but only one conduit remains active in the vadose phase. The selection depends on the initial geometry of a junction, initial distribution of diameters, the evolution in a pressurised regime, and on the dip of the conduits, which plays an important role in vadose entrenchment. In high dip networks, the vadose zone propagates downwards and inwards from the rim of the massif. When a network with randomly distributed initial diameters is supplied with concentrated recharge from the adjacent area, the sink point regresses up upstream along junctions connected to the prominent pathways. Large conductive structures provide deep penetration of high

  19. Evolution of karst conduit networks in transition from pressurised flow to free surface flow

    Directory of Open Access Journals (Sweden)

    M. Perne

    2014-06-01

    Full Text Available We present a novel modelling approach to study the evolution of conduit networks in soluble rocks. Unlike the models presented so far, the model allows a transition from pressurised (pipe flow to a free surface (open channel flow in evolving discrete conduit networks. It calculates flow, solute transport and dissolutional enlargement within each time step and steps through time until a stable flow pattern establishes. The flow in each time step is calculated by calling the EPA Storm Water Management Model (EPA SWMM, which efficiently solves the 1-D Saint Venant equations in a network of conduits. We present several cases with low dip and sub-vertical networks to demonstrate mechanisms of flow pathway selection. In low dip models the inputs were randomly distributed to several junctions. The evolution of pathways progresses upstream: initially pathways linking outlets to the closest inputs evolve fastest because the gradient along these pathways is largest. When a pathway efficiently drains the available recharge, the head drop along the pathway attracts flow from the neighbouring upstream junctions and new connecting pathways evolve. The mechanism progresses from the output boundary inwards until all inputs are connected to the stable flow system. In the pressurised phase, each junction is drained by at least one conduit, but only one conduit remains active in the vadose phase. The selection depends on the initial geometry of a junction, initial distribution of diameters, the evolution in a pressurised regime, and on the dip of the conduits, which plays an important role in vadose entrenchment. In high dip networks, the vadose zone propagates downwards and inwards from the rim of the massif. When a network with randomly distributed initial diameters is supplied with concentrated recharge from the adjacent area, the sink point regresses up upstream along junctions connected to the prominent pathways. Large conductive structures provide deep

  20. Morphology and displacement of dunes in a closed-conduit flow

    CERN Document Server

    Franklin, Erick de Moraes

    2016-01-01

    The transport of solid particles entrained by a fluid flow is frequently found in industrial applications. A better knowledge of it, is of importance to improve particle related industrial processes. When shear stresses exerted by the fluid on the bed of particles are bounded to some limits, a mobile layer of particles known as bed-load takes place in which the particles stay in contact with the fixed bed. If it takes place over a non-erodible ground, and if the particle flow rate is small enough, an initial thin continuous layer of particles becomes discontinuous and composed of isolated dunes. We present here an experimental study to understand some features of the dynamics of isolated dunes under a fluid flow using a closed-conduit experimental loop made of transparent material. Acquired data concerns mainly dune morphology and displacement velocity under different conditions: different types of beads (diameters and densities) and different water flow conditions. We observed that an initial pile of beads p...

  1. Geopulsation, Volcanism and Astronomical Periods

    Institute of Scientific and Technical Information of China (English)

    Yang Xuexiang; Chen Dianyou; Yang Xiaoying; Yang Shuchen

    2000-01-01

    Volcanism is mainly controlled by the intermittent release of energy in the earth. As far as the differential rotation of the earth's inner core is concerned, the Galactic Year may change the gravitational constant G, the solar radiative quantity and the moving speed of the solar system and affect the exchange of angular momentum between core and mantle as well as the energy exchange between crust and mantle. As a result, this leads to eruptions of superplumes and magma, and controls the energy flow from core - mantle boundary (CMB) to crust. When the earth' s speed decreases, it will release a huge amount of energy. They are the reason of the correspondence of the volcanic cycles one by one with the astronomical periods one by one. According to the astronomical periods, volcanic eruptions may possibly be predicted in the future.

  2. Volcanic eruptions and solar activity

    Science.gov (United States)

    Stothers, Richard B.

    1989-01-01

    The historical record of large volcanic eruptions from 1500 to 1980 is subjected to detailed time series analysis. In two weak but probably statistically significant periodicities of about 11 and 80 yr, the frequency of volcanic eruptions increases (decreases) slightly around the times of solar minimum (maximum). Time series analysis of the volcanogenic acidities in a deep ice core from Greenland reveals several very long periods ranging from about 80 to about 350 yr which are similar to the very slow solar cycles previously detected in auroral and C-14 records. Solar flares may cause changes in atmospheric circulation patterns that abruptly alter the earth's spin. The resulting jolt probably triggers small earthquakes which affect volcanism.

  3. Models of volcanic eruption hazards

    Energy Technology Data Exchange (ETDEWEB)

    Wohletz, K.H.

    1992-01-01

    Volcanic eruptions pose an ever present but poorly constrained hazard to life and property for geothermal installations in volcanic areas. Because eruptions occur sporadically and may limit field access, quantitative and systematic field studies of eruptions are difficult to complete. Circumventing this difficulty, laboratory models and numerical simulations are pivotal in building our understanding of eruptions. For example, the results of fuel-coolant interaction experiments show that magma-water interaction controls many eruption styles. Applying these results, increasing numbers of field studies now document and interpret the role of external water eruptions. Similarly, numerical simulations solve the fundamental physics of high-speed fluid flow and give quantitative predictions that elucidate the complexities of pyroclastic flows and surges. A primary goal of these models is to guide geologists in searching for critical field relationships and making their interpretations. Coupled with field work, modeling is beginning to allow more quantitative and predictive volcanic hazard assessments.

  4. Modeling transport and aggregation of volcanic ash particles

    Science.gov (United States)

    Costa, Antonio; Folch, Arnau; Macedonio, Giovanni; Durant, Adam

    2010-05-01

    A complete description of ash aggregation processes in volcanic clouds is an very arduous task and the full coupling of ash transport and ash aggregation models is still computationally prohibitive. A large fraction of fine ash injected in the atmosphere during explosive eruptions aggregate because of complex interactions of surface liquid layers, electrostatic forces, and differences in settling velocities. The formation of aggregates of size and density different from those of the primary particles dramatically changes the sedimentation dynamics and results in lower atmospheric residence times of ash particles and in the formation of secondary maxima of tephra deposit. Volcanic ash transport models should include a full aggregation model accounting for all particle class interaction. However this approach would require prohibitive computational times. Here we present a simplified model for wet aggregation that accounts for both atmospheric and volcanic water transport. The aggregation model assumes a fractal relationship for the number of primary particles in aggregates, average efficiencies factors, and collision frequency functions accounting for Brownian motion, laminar and turbulent fluid shear, and differential settling velocity. We implemented the aggregation model in the WRF+FALL3D coupled modelling system and applied it to different eruptions where aggregation has been recognized to play an important role, such as the August and September 1992 Crater Peak eruptions and the 1980 Mt St Helens eruption. Moreover, understanding aggregation processes in volcanic clouds will contribute to mitigate the risks related with volcanic ash transport and sedimentation.

  5. Using multiple data sets to populate probabilistic volcanic event trees

    Science.gov (United States)

    Newhall, C.G.; Pallister, John S.

    2014-01-01

    The key parameters one needs to forecast outcomes of volcanic unrest are hidden kilometers beneath the Earth’s surface, and volcanic systems are so complex that there will invariably be stochastic elements in the evolution of any unrest. Fortunately, there is sufficient regularity in behaviour that some, perhaps many, eruptions can be forecast with enough certainty for populations to be evacuated and kept safe. Volcanologists charged with forecasting eruptions must try to understand each volcanic system well enough that unrest can be interpreted in terms of pre-eruptive process, but must simultaneously recognize and convey uncertainties in their assessment. We have found that use of event trees helps to focus discussion, integrate data from multiple sources, reach consensus among scientists about both pre-eruptive process and uncertainties and, in some cases, to explain all of this to officials. Figure 1 shows a generic volcanic event tree from Newhall and Hoblitt (2002) that can be modified as needed for each specific volcano. This paper reviews how we and our colleagues have used such trees during a number of volcanic crises worldwide, for rapid hazard assessments in situations in which more formal expert elicitations could not be conducted. We describe how Multiple Data Sets can be used to estimate probabilities at each node and branch. We also present case histories of probability estimation during crises, how the estimates were used by public officials, and some suggestions for future improvements.

  6. On a Possible Unified Scaling Law for Volcanic Eruption Durations.

    Science.gov (United States)

    Cannavò, Flavio; Nunnari, Giuseppe

    2016-03-01

    Volcanoes constitute dissipative systems with many degrees of freedom. Their eruptions are the result of complex processes that involve interacting chemical-physical systems. At present, due to the complexity of involved phenomena and to the lack of precise measurements, both analytical and numerical models are unable to simultaneously include the main processes involved in eruptions thus making forecasts of volcanic dynamics rather unreliable. On the other hand, accurate forecasts of some eruption parameters, such as the duration, could be a key factor in natural hazard estimation and mitigation. Analyzing a large database with most of all the known volcanic eruptions, we have determined that the duration of eruptions seems to be described by a universal distribution which characterizes eruption duration dynamics. In particular, this paper presents a plausible global power-law distribution of durations of volcanic eruptions that holds worldwide for different volcanic environments. We also introduce a new, simple and realistic pipe model that can follow the same found empirical distribution. Since the proposed model belongs to the family of the self-organized systems it may support the hypothesis that simple mechanisms can lead naturally to the emergent complexity in volcanic behaviour.

  7. Zircon U-Pb geochronology of the volcanic rocks from Fanchang-Ningwu volcanic basins in the Lower Yangtze region and its geological implications

    Institute of Scientific and Technical Information of China (English)

    YAN Jun; LIU HaiQuan; SONG ChuanZhong; XU XiSheng; AN YaJun; LIU Jia; DAI LiQun

    2009-01-01

    The latest eruptions in two important Mesozoic volcanic basins of Fanchang and Ningwu located in the middle-lower reaches of the Yangtze River formed the bimodal volcanic rocks of the Kedoushan Formation and ultrapotassic volcanic rocks of the Niangniangshan Formation,respectively.The representative volcanic rocks of the two Formations were selected for LA-ICPMS zircon U-Pb dating.The results indicate that there exist a large amount of magmatic zircons as indicated by high Th/U ratios in these volcanic rocks.The weighted mean age of 21 analyses is 130.7±1.1 Ma for the Kedoushan Formation,and that of 20 analyses is 130.6±1.1 Ma for the Niangniangshan Formation.These U-Pb ages are interpreted to represent the formation times of the volcanic rocks.In combination with other known geochronological data for Mesozoic volcanic rocks from the Lower Yangtze region,it is proposed that the latest volcanic activations in the Jinniu,Luzong,Fanchang and Ningwu volcanic basins probably came to end prior to ca.128 Me.There is no significant time interval between the early and later volcanic activities in the Luzong and Ningwu basins,suggesting e short duration of volcanic activities and thus implying the onset of an extensional tectonic setting at about 130 Ma in the Lower Yangtze region.Integrated studies reveal that the Early Cretaceous magmatic activities and their geochronological framework in the Lower Yangtze region are a response to progressively dynamic deep processes that started with the transformation of tectonic setting from compression to extension,followed by delaminating of the lower part of the thickened lithosphere,lithospheric thinning,asthenosphere upwelling,and crust-mantle interaction.

  8. Percutaneous balloon dilation of Carpentier-Edwards porcine-valved right ventricle-to-pulmonary artery conduits.

    Science.gov (United States)

    Hall, Amanda C; Miga, Daniel E; Leonard, Glenn T; Wang, Hongyue; Kavey, Rae-Ellen; Alfieris, George M

    2013-04-01

    Right ventricular outflow tract (RVOT) conduit stenosis remains a significant problem for patients with right ventricle-to-pulmonary artery (RV-to-PA) conduits placed as palliation for congenital heart disease. Previous reports on balloon dilation of RVOT conduits all describe small series with varying levels of success during limited follow-up evaluation. This study reviewed all patients with RV-to-PA conduits who underwent percutaneous balloon dilation for conduit stenosis at the authors' institution from 2000 to 2011. Patients with Carpentier-Edwards (CE) model 4300 porcine-valved conduits (Edwards Lifesciences Corp., Irvine, CA) (n = 19) were compared with patients who had all other types of conduits (n = 19). Successful balloon angioplasty was defined as a 20 % decrease in the RV-to-PA gradient, a 20 % decrease in the ratio of the RV systolic-to-aortic systolic pressure, or both. Balloon dilation was successful for 57.9 % of the patients with CE conduits and for 31.6 % of patients with other types of conduits (p = 0.10, Chi square test). Logistic regression analysis showed that balloon dilation was significantly more likely to be successful with CE valves than with other types (odds ratio [OR], 6.59; 95 % confidence interval [CI], 1.22-35.49). In a continuous series of patients with stenotic RV-to-PA conduits, the CE porcine-valved conduit was more amenable to percutaneous balloon dilation than other types of RV-to-PA conduits at the midterm follow-up evaluation. This has important ramifications in terms of valve selection for patients with congenital heart disease who will require surgical reintervention for RVOT stenosis.

  9. Aspects of mineral transformation during weathering of volcanic material (the microscopic and submicroscopic level).

    NARCIS (Netherlands)

    Jongmans, A.G.

    1994-01-01

    Mineral transformation at the earth surface is a complex process. In volcanic ejecta, such transformations tend to be fairly rapid. Many weathering studies on volcanic materials have been carried out at different scales of observations, mostly using bulk samples. However, to get a proper understandi

  10. Aspects of mineral transformation during weathering of volcanic materials : the microscopic and submicroscopic level

    NARCIS (Netherlands)

    Jongmans, A.G.

    1994-01-01

    Mineral transformation at the earth surface is a complex process. In volcanic ejecta, such transformations tend to be fairly rapid. Many weathering studies on volcanic materials have been carried out at different scales of observations, mostly using bulk samples. However, to get a proper

  11. Recurrence models of volcanic events: Applications to volcanic risk assessment

    Energy Technology Data Exchange (ETDEWEB)

    Crowe, B.M. [Los Alamos National Lab., Las Vegas, NV (United States); Picard, R.; Valentine, G. [Los Alamos National Lab., NM (United States); Perry, F.V. [New Mexico Univ., Albuquerque, NM (United States)

    1992-03-01

    An assessment of the risk of future volcanism has been conducted for isolation of high-level radioactive waste at the potential Yucca Mountain site in southern Nevada. Risk used in this context refers to a combined assessment of the probability and consequences of future volcanic activity. Past studies established bounds on the probability of magmatic disruption of a repository. These bounds were revised as additional data were gathered from site characterization studies. The probability of direct intersection of a potential repository located in an eight km{sup 2} area of Yucca Mountain by ascending basalt magma was bounded by the range of 10{sup {minus}8} to 10{sup {minus}10} yr{sup {minus}1 2}. The consequences of magmatic disruption of a repository were estimated in previous studies to be limited. The exact releases from such an event are dependent on the strike of an intruding basalt dike relative to the repository geometry, the timing of the basaltic event relative to the age of the radioactive waste and the mechanisms of release and dispersal of the waste radionuclides in the accessible environment. The combined low probability of repository disruption and the limited releases associated with this event established the basis for the judgement that the risk of future volcanism was relatively low. It was reasoned that that risk of future volcanism was not likely to result in disqualification of the potential Yucca Mountain site.

  12. Electrospun Polycaprolactone/Polylactic Acid Nanofibers as an Artificial Nerve Conduit