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Sample records for volcanic front evf

  1. Evaluation verification facilities (EVF) at MINT: concept and implementation

    International Nuclear Information System (INIS)

    Mohamed Hairul Hasmoni; Abd Nassir Ibrahim; Ab Razak Hamzah

    2003-01-01

    EVF facilities and components available are described comprehensively. Objective of establishing EVF as a National Centre for non-destructive testing (NDT) are discussed for various activities of method and equipment validation, R and D on quantitative NDT technique, training and certification, and defect characterization. For a successful activity available at EVF, it is vital that industry participates through input of funding, sponsorship and knowledge sharing. The Malaysian Institute for Nuclear Technology Research (MINT) invested a lot in this facility and ready to share this facility under various mechanisms such as memorandum of understanding (MOU), memorandum of agreement (MOA), contract research or letter of agreement. The facility would be open to industry. Member of NDT community are welcomed to conduct trial and discuss particular areas of interest with others in the industry. Optimising the facility by utilising the facility available and adding new components would make EVF a national centre for NDT and centre of excellence. This paper reviews the concept and implementation of an Evaluation Verification Facility (EVF) at MINT. The types and designs of facilities available are described and characterised by usage NDT. (Author)

  2. The Valle de Bravo Volcanic Field. A monogenetic field in the central front of the Mexican Volcanic Belt

    Science.gov (United States)

    Aguirre-Diaz, G. J.; Jaimes-Viera, M. D.; Nieto-Obreg¢n, J.; Lozano-Santacruz, R.

    2003-12-01

    The Valle de Bravo volcanic field, VBVF, is located in the central-southern front of the Mexican Volcanic Belt just to the southwest of Nevado de Toluca volcano. The VBVF covers 3,703 square Km and includes at least 122 cinder cones, 1 shield volcano, several domes, and the 2 volcanic complexes of Zitacuaro and Villa de Allende. Morphometric parameters calibrated with isotopic ages of the volcanic products indicate four groups or units for the VBVF, Pliocene domes and lava flows, undifferentiated Pleistocene lava flows,> 40 Ka cones and lavas, 40 to 25 Ka cones and lavas, 25 to 10 Ka cones and lavas, and < 10 Ka cones and lavas. Whole-rock chemistry shows that all products of the VBVF range from basaltic andesites to dacites. No basalts were found, in spite of many units are olivine-rich and large some with large weight percent contents of MgO, 1 to 9. There is the possibility that some or all of the olivines in some samples could be xenocrysts. Some andesites are high in Sr, 1000 to 1800 ppm, that correlates with relatively high values of Ba, Cr, Ni, Cu, CaO and MgO. Y and Nb have the typical low values for orogenic rocks. The only shield volcano of the VBVF has a base of 9 Km, and its composition is practically the average composition of the whole field. Stratigraphycally, it is one of the earlier events of the VBVF. Compared with other volcanic fields of the Mexican Volcanic Belt, it lacks basalts and alkalic rocks. All volcanism of this field is calcalkaline

  3. Greated era of volcanic front in Middle Kyushu and Western Chugoku districts

    Energy Technology Data Exchange (ETDEWEB)

    Kamata, Hirotake; Hoshizumi, Hideo; Koyaguchi, Takehiro

    1987-10-01

    Purpose of this study was to determine the era when the creation of the volcanos commenced which were extending from north-east to south west, by using the K-Ar age of volcanic rocks which were continuously distributed from middle Kyushu to San-in district and which were mainly composed of amphibole andesite. By comparing with geological map, relation with the stratigraphic order of layers at Yabakei, Himejima and Aono were considered. It was concluded that, in every place, the vocanic activities commenced much later era than creation of basement rock. It was also recognized that, by studying the relation with Phillipine Plate, deep earthquake was related with the volcanic front of south west Japan arc. (8 figs, 2 tabs, 14 refs)

  4. Origin of silicic magmas along the Central American volcanic front: Genetic relationship to mafic melts

    Science.gov (United States)

    Vogel, Thomas A.; Patino, Lina C.; Eaton, Jonathon K.; Valley, John W.; Rose, William I.; Alvarado, Guillermo E.; Viray, Ela L.

    2006-09-01

    Silicic pyroclastic flows and related deposits are abundant along the Central American volcanic front. These silicic magmas erupted through both the non-continental Chorotega block to the southeast and the Paleozoic continental Chortis block to the northwest. The along-arc variations of the silicic deposits with respect to diagnostic trace element ratios (Ba/La, U/Th, Ce/Pb), oxygen isotopes, Nd and Sr isotope ratios mimic the along-arc variation in the basaltic and andesitic lavas. This variation in the lavas has been interpreted to indicate relative contributions from the slab and asthenosphere to the basaltic magmas [Carr, M.J., Feigenson, M.D., Bennett, E.A., 1990. Incompatible element and isotopic evidence for tectonic control of source mixing and melt extraction along the Central American arc. Contributions to Mineralogy and Petrology, 105, 369-380.; Patino, L.C., Carr, M.J. and Feigenson, M.D., 2000. Local and regional variations in Central American arc lavas controlled by variations in subducted sediment input. Contributions to Mineralogy and Petrology, 138 (3), 265-283.]. With respect to along-arc trends in basaltic lavas the largest contribution of slab fluids is in Nicaragua and the smallest input from the slab is in central Costa Rica — similar trends are observed in the silicic pyroclastic deposits. Data from melting experiments of primitive basalts and basaltic andesites demonstrate that it is difficult to produce high K 2O/Na 2O silicic magmas by fractional crystallization or partial melting of low-K 2O/Na 2O sources. However fractional crystallization or partial melting of medium- to high-K basalts can produce these silicic magmas. We interpret that the high-silica magmas associated Central America volcanic front are partial melts of penecontemporaneous, mantle-derived, evolved magmas that have ponded and crystallized in the mid-crust — or are melts extracted from these nearly completely crystallized magmas.

  5. Evf2 lncRNA/BRG1/DLX1 interactions reveal RNA-dependent inhibition of chromatin remodeling.

    Science.gov (United States)

    Cajigas, Ivelisse; Leib, David E; Cochrane, Jesse; Luo, Hao; Swyter, Kelsey R; Chen, Sean; Clark, Brian S; Thompson, James; Yates, John R; Kingston, Robert E; Kohtz, Jhumku D

    2015-08-01

    Transcription-regulating long non-coding RNAs (lncRNAs) have the potential to control the site-specific expression of thousands of target genes. Previously, we showed that Evf2, the first described ultraconserved lncRNA, increases the association of transcriptional activators (DLX homeodomain proteins) with key DNA enhancers but represses gene expression. In this report, mass spectrometry shows that the Evf2-DLX1 ribonucleoprotein (RNP) contains the SWI/SNF-related chromatin remodelers Brahma-related gene 1 (BRG1, SMARCA4) and Brahma-associated factor (BAF170, SMARCC2) in the developing mouse forebrain. Evf2 RNA colocalizes with BRG1 in nuclear clouds and increases BRG1 association with key DNA regulatory enhancers in the developing forebrain. While BRG1 directly interacts with DLX1 and Evf2 through distinct binding sites, Evf2 directly inhibits BRG1 ATPase and chromatin remodeling activities. In vitro studies show that both RNA-BRG1 binding and RNA inhibition of BRG1 ATPase/remodeling activity are promiscuous, suggesting that context is a crucial factor in RNA-dependent chromatin remodeling inhibition. Together, these experiments support a model in which RNAs convert an active enhancer to a repressed enhancer by directly inhibiting chromatin remodeling activity, and address the apparent paradox of RNA-mediated stabilization of transcriptional activators at enhancers with a repressive outcome. The importance of BRG1/RNA and BRG1/homeodomain interactions in neurodevelopmental disorders is underscored by the finding that mutations in Coffin-Siris syndrome, a human intellectual disability disorder, localize to the BRG1 RNA-binding and DLX1-binding domains. © 2015. Published by The Company of Biologists Ltd.

  6. The effect of deformation after backarc spreading between the rear arc and current volcanic front in Shikoku Basin obtained by seismic reflection survey

    Science.gov (United States)

    Yamashita, M.; Takahashi, N.; Nakanishi, A.; Kodaira, S.; Tamura, Y.

    2012-12-01

    Detailed crustal structure information of a back-arc basin must be obtained to elucidate the mechanism of its opening. Especially, the Shikoku Basin, which occupies the northern part of the Philippine Sea Plate between the Kyushu-Palau Ridge and the Izu-Bonin (Ogasawara) Arc, is an important area to understand the evolution of the back-arc basins as a part of the growth process of the Philippine Sea. Especially, the crustal structure oft the east side of Shikoku Basin is complicated by colliding to the Izu Peninsula Japan Agency for Marine-Earth Science and Technology has been carried out many multi-channel seismic reflection surveys since 2004 in Izu-Bonin region. Kodaira et al. (2008) reported the results of a refraction seismic survey along a north-south profile within paleoarc in the rear arc (i.e., the Nishi-shichito ridge) about 150 km west of current volcanic front. According to their results, the variation relationship of crustal thickness between the rear arc and volcanic front is suggested the evidence of rifting from current volcanic arc. There is the en-echelon arrangement is located in the eastern side of Shikoku Basin from current arc to rear arc, and it is known to activate after ceased spreading at 15 Ma (Okino et al., 1994) of Shikoku Basin by geologic sampling of Ishizuka et al. (2003). Our MCS results are also recognized the recent lateral fault zone is located in east side of Shikoku Basin. We carried out high density grid multi-channel seismic reflection (MCS) survey using tuned airgun in order to obtain the relationship between the lateral faults and en-echelon arrangement in KR08-04 cruise. We identified the deformation of sediments in Shikoku Basin after activity of Kanbun seamount at 8 Ma in MCS profile. It is estimated to activate a part of the eastern side of Shikoku Basin after construction of en-echelon arrangement and termination of Shikoku Basin spreading. Based on analyses of magnetic and gravity anomalies, Yamazaki and Yuasa (1998

  7. Drosophila larvae food intake cessation following exposure to Erwinia contaminated media requires odor perception, Trpa1 channel and evf virulence factor.

    Science.gov (United States)

    Keita, Seydou; Masuzzo, Ambra; Royet, Julien; Kurz, C Leopold

    2017-05-01

    When exposed to microorganisms, animals use several protective strategies. On one hand, as elegantly exemplified in Drosophila melanogaster, the innate immune system recognizes microbial compounds and triggers an antimicrobial response. On the other hand, behaviors preventing an extensive contact with the microbes and thus reducing the risk of infection have been described. However, these reactions ranging from microbes aversion to intestinal transit increase or food intake decrease have been rarely defined at the molecular level. In this study, we set up an experimental system that allowed us to rapidly identify and quantify food intake decreases in Drosophila larvae exposed to media contaminated with bacteria. Specifically, we report a robust dose-dependent food intake decrease following exposure to the bacteria Erwinia carotovora carotovora strain Ecc15. We demonstrate that this response does not require Imd innate immune pathway, but rather the olfactory neuronal circuitry, the Trpa1 receptor and the evf virulence factor. Finally, we show that Ecc15 induce the same behavior in the invasive pest insect Drosophila suzukii. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Influence of the balance of the intertropical front on seasonal variations of the isotopic composition in rainfall at Kisiba Masoko (Rungwe Volcanic Province, SW, Tanzania).

    Science.gov (United States)

    Nivet, Fantine; Bergonzini, Laurent; Mathé, Pierre-Etienne; Noret, Aurélie; Monvoisin, Gaël; Majule, Amos; Williamson, David

    2018-08-01

    Tropical rainfall isotopic composition results from complex processes. The climatological and environmental variability in East Africa increases this complexity. Long rainfall isotope datasets are needed to fill the lack of observations in this region. At Kisiba Masoko, Tanzania, rainfall and rain isotopic composition have been monitored during 6 years. Mean year profiles allow to analyse the seasonal variations. The mean annual rainfall is 2099 mm with a rain-weighted mean composition of -3.2 ‰ for δ 18 O and -11.7 ‰ for δ 2 H. The results are consistent with available data although they present their own specificity. Thus, if the local meteoric water line is δ 2 H = 8.6 δ 18 O + 14.8, two seasonal lines are observed. The seasonality of the isotopic composition in rain and deuterium excess has been compared with precipitating air masses backtracking trajectories to characterize a simple scheme of vapour histories. The three major oceanic sources have two moisture signatures with their own trajectory histories: one originated from the tropical Indian Ocean at the beginning of the rainy season and one from the Austral Ocean at its end. The presented isotopic seasonality depends on the balance of the intertropical front and provides a useful dataset to improve the knowledge about local processes.

  9. Redox fronts

    International Nuclear Information System (INIS)

    Chapman, N.; McKinley, I.; Shea, M.; Smellie, J.

    1993-01-01

    This article describes the investigations of redox fronts performed at the Osamu Utsumi mine. Results obtained by modelling groups on the rate of movement of the redox fronts and on the chemical reactions involved are discussed. Some of the most important rockwater interactions which occur at redox fronts can be modelled reasonably well but the complex redox chemistry of elements like sulphur is poorly simulated. The observed enrichment of many trace elements close to the redox fronts could be of significance for high-level waste repositories, but cannot be quantified by existing models. (author) 6 figs., 1 tab

  10. 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.

  11. Volcanic risk

    International Nuclear Information System (INIS)

    Rancon, J.P.; Baubron, J.C.

    1995-01-01

    This project follows the previous multi-disciplinary studies carried out by the French Bureau de Recherches Geologiques et Minieres (BRGM) on the two active volcanoes of the French lesser Antilles: Mt Pelee (Martinique) and Soufriere (Guadeloupe) for which geological maps and volcanic risk studies have been achieved. The research program comprises 5 parts: the study of pyroclastic deposits from recent eruptions of the two volcanoes for a better characterization of their eruptive phenomenology and a better definition of crisis scenarios; the study of deposits and structures of active volcanoes from Central America and the study of eruptive dynamics of andesite volcanoes for a transposition to Antilles' volcanoes; the starting of a methodological multi-disciplinary research (volcanology, geography, sociology...) on the volcanic risk analysis and on the management of a future crisis; and finally, the development of geochemical survey techniques (radon, CO 2 , H 2 O) on active volcanoes of Costa-Rica and Europe (Fournaise, Furnas, Etna) and their application to the Soufriere. (J.S.). 9 refs., 3 figs

  12. Volcanic features of Io

    International Nuclear Information System (INIS)

    Carr, M.H.; Masursky, H.; Strom, R.G.; Terrile, R.J.

    1979-01-01

    The volcanic features of Io as detected during the Voyager mission are discussed. The volcanic activity is apparently higher than on any other body in the Solar System. Its volcanic landforms are compared with features on Earth to indicate the type of volcanism present on Io. (U.K.)

  13. Volcanic signals in oceans

    KAUST Repository

    Stenchikov, Georgiy L.; Delworth, Thomas L.; Ramaswamy, V.; Stouffer, Ronald J.; Wittenberg, Andrew; Zeng, Fanrong

    2009-01-01

    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

  14. Volcanic stratigraphy: A review

    Science.gov (United States)

    Martí, Joan; Groppelli, Gianluca; Brum da Silveira, Antonio

    2018-05-01

    Volcanic stratigraphy is a fundamental component of geological mapping in volcanic areas as it yields the basic criteria and essential data for identifying the spatial and temporal relationships between volcanic products and intra/inter-eruptive processes (earth-surface, tectonic and climatic), which in turn provides greater understanding of the geological evolution of a region. Establishing precise stratigraphic relationships in volcanic successions is not only essential for understanding the past behaviour of volcanoes and for predicting how they might behave in the future, but is also critical for establishing guidelines for exploring economic and energy resources associated with volcanic systems or for reconstructing the evolution of sedimentary basins in which volcanism has played a significant role. Like classical stratigraphy, volcanic stratigraphy should also be defined using a systematic methodology that can provide an organised and comprehensive description of the temporal and spatial evolution of volcanic terrain. This review explores different methods employed in studies of volcanic stratigraphy, examines four case studies that use differing stratigraphic approaches, and recommends methods for using systematic volcanic stratigraphy based on the application of the concepts of traditional stratigraphy but adapted to the needs of volcanological environment.

  15. Negative Ion Density Fronts

    International Nuclear Information System (INIS)

    Igor Kaganovich

    2000-01-01

    Negative ions tend to stratify in electronegative plasmas with hot electrons (electron temperature Te much larger than ion temperature Ti, Te > Ti ). The boundary separating a plasma containing negative ions, and a plasma, without negative ions, is usually thin, so that the negative ion density falls rapidly to zero-forming a negative ion density front. We review theoretical, experimental and numerical results giving the spatio-temporal evolution of negative ion density fronts during plasma ignition, the steady state, and extinction (afterglow). During plasma ignition, negative ion fronts are the result of the break of smooth plasma density profiles during nonlinear convection. In a steady-state plasma, the fronts are boundary layers with steepening of ion density profiles due to nonlinear convection also. But during plasma extinction, the ion fronts are of a completely different nature. Negative ions diffuse freely in the plasma core (no convection), whereas the negative ion front propagates towards the chamber walls with a nearly constant velocity. The concept of fronts turns out to be very effective in analysis of plasma density profile evolution in strongly non-isothermal plasmas

  16. Volcanism on Io

    Science.gov (United States)

    Davies, Ashley Gerard

    2014-03-01

    Preface; Introduction; Part I. Io, 1610 to 1995: Galileo to Galileo: 1. Io, 1610-1979; 2. Between Voyager and Galileo: 1979-95; 3. Galileo at Io; Part II. Planetary Volcanism: Evolution and Composition: 4. Io and Earth: formation, evolution, and interior structure; 5. Magmas and volatiles; Part III. Observing and Modeling Volcanic Activity: 6. Observations: thermal remote sensing of volcanic activity; 7. Models of effusive eruption processes; 8. Thermal evolution of volcanic eruptions; Part IV. Galileo at Io: the Volcanic Bestiary: 9. The view from Galileo; 10. The lava lake at Pele; 11. Pillan and Tvashtar: lava fountains and flows; 12. Prometheus and Amirani: Effusive activity and insulated flows; 13. Loki Patera: Io's powerhouse; 14. Other volcanoes and eruptions; Part V. Volcanism on Io: The Global View: 15. Geomorphology: paterae, shields, flows and mountains; 16. Volcanic plumes; 17. Hot spots; Part VI. Io after Galileo: 18. Volcanism on Io: a post-Galileo view; 19. The future of Io observations; Appendix 1; Appendix 2; References; Index.

  17. 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.

  18. Light-Front QCD

    Energy Technology Data Exchange (ETDEWEB)

    Brodsky, S.

    2004-11-30

    In these lectures, I survey a number of applications of light-front methods to hadron and nuclear physics phenomenology and dynamics, including light-front statistical physics. Light-front Fock-state wavefunctions provide a frame-independent representation of hadrons in terms of their fundamental quark and gluon degrees of freedom. Nonperturbative methods for computing LFWFs in QCD are discussed, including string/gauge duality which predicts the power-law fall-off at high momentum transfer of light-front Fock-state hadronic wavefunctions with an arbitrary number of constituents and orbital angular momentum. The AdS/CFT correspondence has important implications for hadron phenomenology in the conformal limit, including an all-orders derivation of counting rules for exclusive processes. One can also compute the hadronic spectrum of near-conformal QCD assuming a truncated AdS/CFT space. Given the LFWFs, one can compute form factors, heavy hadron decay amplitudes, hadron distribution amplitudes, and the generalized parton distributions underlying deeply virtual Compton scattering. The quantum fluctuations represented by the light-front Fock expansion leads to novel QCD phenomena such as color transparency, intrinsic heavy quark distributions, diffractive dissociation, and hidden-color components of nuclear wavefunctions. A new test of hidden color in deuteron photodisintegration is proposed. The origin of leading-twist phenomena such as the diffractive component of deep inelastic scattering, single-spin asymmetries, nuclear shadowing and antishadowing is also discussed; these phenomena cannot be described by light-front wavefunctions of the target computed in isolation. Part of the anomalous NuTeV results for the weak mixing angle {theta}{sub W} could be due to the non-universality of nuclear antishadowing for charged and neutral currents.

  19. 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...

  20. Modes of uranium occurrences in Colorado Front Range

    International Nuclear Information System (INIS)

    Carpenter, R.H.; Gallagher, J.R.L.; Huber, G.C.

    1978-01-01

    This report is an analysis of the various types of uranium occurrences in the Colorado Front Range and the environments in which they developed. The early Proterozoic crust of this region is believed to have been a platform on which intermediate to felsic volcanic centers formed. Some units in the volcanic stratigraphy as well as in the sediments which were deposited in the shallow, intervening seaways are thought to have been uraniferous. Tectonism, occurring about 1.7 By ago, was accompanied and followed by three periods of Precambrian igneous activity. The volcanics and sediments were converted to a metavolcanic-metasedimentary sequence known as the Idaho Springs Formation. Some of the syngenetic uranium remaining in the volcanics and sediments after metamorphism may have been mobilized and incorporated within the Silver Plume plutons and the Pikes Peak batholith and concentrated in pegmatite dikes, pegmatites and fractured areas in the hood zones in the apophyses, or along the flanks of these intrusives. Some or most of the uranium found in these sites may have been generated deeper in the continental plate. Uplift of the Front Range in the Late Mississippian and arching during the Laramide with accompanying faulting set the stage for early and mid-Tertiary igneous activity and associated uranium mineralization. The source of the early and mid-Tertiary uranium mineralization is a point of current debate. Exploration for uranium in the igneous and metamorphic terrain of the Front Range is summarized, and models of each major uranium occurrence are described. Finally, the Front Range exploration potential for uranium is outlined

  1. Beam front accelerators

    International Nuclear Information System (INIS)

    Reiser, M.

    1982-01-01

    An intense relativistic electron beam cannot propagate in a metal drift tube when the current exceeds the space charge limit. Very high charge density and electric field gradients (10 2 to 10 3 MV/m) develop at the beam front and the electrons are reflected. When a neutral gas or a plasma is present, collective acceleration of positive ions occur, and the resulting charge neutralization enables the beam to propagate. Experimental results, theoretical understanding, and schemes to achieve high ion energies by external control of the beam front velocity will be reviewed

  2. Martian volcanism: A review

    International Nuclear Information System (INIS)

    Carr, M.H.

    1987-01-01

    Martian volcanism is reviewed. It is emphasized that lava plains constitute the major type of effusive flow, and can be differentiated by morphologic characteristics. Shield volcanoes, domes, and patera constitute the major constructional landforms, and recent work has suggested that explosive activity and resulting pyroclastic deposits may have been involved with formation of some of the small shields. Analysis of morphology, presumed composition, and spectroscopic data all indicate that Martian volcanism was dominantly basaltic in composition

  3. Paleogene Sediment Character of Mountain Front Central Sumatra Basin

    Directory of Open Access Journals (Sweden)

    P. A. Suandhi

    2014-07-01

    Full Text Available DOI: 10.17014/ijog.v8i3.164The SE-NW trending Mountain Front of Central Sumatra Basin is located in the southern part of the basin. The Mountain Front is elongated parallel to the Bukit Barisan Mountain, extending from the Regencies of North Padang Lawas (Gunung Tua in the northwest, Rokan Hulu, Kampar, Kuantan Singingi, and Inderagiri Hulu Regency in the southeast. The Palaeogene sediments also represent potential exploration objectives in Central Sumatra Basin, especially in the mountain front area. Limited detailed Palaeogene sedimentology information cause difficulties in hydrocarbon exploration in this area. Latest age information and attractive sediment characters based on recent geological fieldwork (by chaining method infer Palaeogene sediment potential of the area. The Palaeogene sedimentary rock of the mountain front is elongated from northwest to southeast. Thickness of the sedimentary unit varies between 240 - 900 m. Palynology samples collected recently indicate that the oldest sedimentary unit is Middle Eocene and the youngest one is Late Oligocene. This latest age information will certainly cause significant changes to the existing surface geological map of the mountain front area. Generally, the Palaeogene sediments of the mountain front area are syn-rift sediments. The lower part of the Palaeogene deposit consists of fluvial facies of alluvial fan and braided river facies sediments. The middle part consists of fluvial meandering facies, lacustrine delta facies, and turbidity lacustrine facies sediments. The upper part consists of fluvial braided facies and transitional marine facies sediments. Volcanism in the area is detected from the occurrence of volcanic material as lithic material and spotted bentonite layers in the middle part of the mountain front area. Late rifting phase is indicated by the presence of transitional marine facies in the upper part of the Palaeogene sediments.

  4. 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

  5. Dynamics of curved fronts

    CERN Document Server

    Pelce, Pierre

    1989-01-01

    In recent years, much progress has been made in the understanding of interface dynamics of various systems: hydrodynamics, crystal growth, chemical reactions, and combustion. Dynamics of Curved Fronts is an important contribution to this field and will be an indispensable reference work for researchers and graduate students in physics, applied mathematics, and chemical engineering. The book consist of a 100 page introduction by the editor and 33 seminal articles from various disciplines.

  6. Radiative thermal conduction fronts

    International Nuclear Information System (INIS)

    Borkowski, K.J.; Balbus, S.A.; Fristrom, C.C.

    1990-01-01

    The discovery of the O VI interstellar absorption lines in our Galaxy by the Copernicus observatory was a turning point in our understanding of the Interstellar Medium (ISM). It implied the presence of widespread hot (approx. 10 to the 6th power K) gas in disk galaxies. The detection of highly ionized species in quasi-stellar objects' absorption spectra may be the first indirect observation of this hot phase in external disk galaxies. Previous efforts to understand extensive O VI absorption line data from our Galaxy were not very successful in locating the regions where this absorption originates. The location at interfaces between evaporating ISM clouds and hot gas was favored, but recent studies of steady-state conduction fronts in spherical clouds by Ballet, Arnaud, and Rothenflug (1986) and Bohringer and Hartquist (1987) rejected evaporative fronts as the absorption sites. Researchers report here on time-dependent nonequilibrium calculations of planar conductive fronts whose properties match well with observations, and suggest reasons for the difference between the researchers' results and the above. They included magnetic fields in additional models, not reported here, and the conclusions are not affected by their presence

  7. Modeling volcanic ash dispersal

    CERN Multimedia

    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...

  8. Stationary flow near fronts

    Directory of Open Access Journals (Sweden)

    Reinhold Steinacker

    2016-12-01

    Full Text Available In 1906, the Austrian scientist Max Margules published a paper on temperature stratification in resting and non-accelerated moving air. The paper derives conditions for stationary slopes of air mass boundaries and was an important forerunner of frontal theories. Its formulation of relations between changes in density and geostrophic wind across the front is basically a discrete version of the thermal wind balance equation. The paper was highly influential and is still being cited to the present day. This paper accompanies an English translation of Margules’ seminal paper. We conclude here our “Classic Papers” series of the Meteorologische Zeitschrift.

  9. Backprojection of volcanic tremor

    Science.gov (United States)

    Haney, Matthew M.

    2014-01-01

    Backprojection has become a powerful tool for imaging the rupture process of global earthquakes. We demonstrate the ability of backprojection to illuminate and track volcanic sources as well. We apply the method to the seismic network from Okmok Volcano, Alaska, at the time of an escalation in tremor during the 2008 eruption. Although we are able to focus the wavefield close to the location of the active cone, the network array response lacks sufficient resolution to reveal kilometer-scale changes in tremor location. By deconvolving the response in successive backprojection images, we enhance resolution and find that the tremor source moved toward an intracaldera lake prior to its escalation. The increased tremor therefore resulted from magma-water interaction, in agreement with the overall phreatomagmatic character of the eruption. Imaging of eruption tremor shows that time reversal methods, such as backprojection, can provide new insights into the temporal evolution of volcanic sources.

  10. Volcanic eruptions on Io

    Science.gov (United States)

    Strom, R. G.; Schneider, N. M.; Terrile, R. J.; Hansen, C.; Cook, A. F.

    1981-01-01

    Nine eruption plumes which were observed during the Voyager 1 encounter with Io are discussed. During the Voyager 2 encounter, four months later, eight of the eruptions were still active although the largest became inactive sometime between the two encounters. Plumes range in height from 60 to over 300 km with corresponding ejection velocities of 0.5 to 1.0 km/s and plume sources are located on several plains and consist of fissures or calderas. The shape and brightness distribution together with the pattern of the surface deposition on a plume 3 is simulated by a ballistic model with a constant ejection velocity of 0.5 km/s and ejection angles which vary from 0-55 deg. The distribution of active and recent eruptions is concentrated in the equatorial regions and indicates that volcanic activity is more frequent and intense in the equatorial regions than in the polar regions. Due to the geologic setting of certain plume sources and large reservoirs of volatiles required for the active eruptions, it is concluded that sulfur volcanism rather than silicate volcanism is the most likely driving mechanism for the eruption plumes.

  11. Front propagation in flipping processes

    International Nuclear Information System (INIS)

    Antal, T; Ben-Avraham, D; Ben-Naim, E; Krapivsky, P L

    2008-01-01

    We study a directed flipping process that underlies the performance of the random edge simplex algorithm. In this stochastic process, which takes place on a one-dimensional lattice whose sites may be either occupied or vacant, occupied sites become vacant at a constant rate and simultaneously cause all sites to the right to change their state. This random process exhibits rich phenomenology. First, there is a front, defined by the position of the leftmost occupied site, that propagates at a nontrivial velocity. Second, the front involves a depletion zone with an excess of vacant sites. The total excess Δ k increases logarithmically, Δ k ≅ ln k, with the distance k from the front. Third, the front exhibits ageing-young fronts are vigorous but old fronts are sluggish. We investigate these phenomena using a quasi-static approximation, direct solutions of small systems and numerical simulations

  12. Photoionization effects in ionization fronts

    International Nuclear Information System (INIS)

    Arrayas, Manuel; Fontelos, Marco A; Trueba, Jose L

    2006-01-01

    In this paper we study the effects of photoionization processes on the propagation of both negative and positive ionization fronts in streamer discharge. We show that negative fronts accelerate in the presence of photoionization events. The appearance and propagation of positive ionization fronts travelling with constant velocity is explained as the result of the combined effects of photoionization and electron diffusion. The photoionization range plays an important role in the selection of the velocity of the ionization front as we show in this work

  13. Photoionization effects in ionization fronts

    Energy Technology Data Exchange (ETDEWEB)

    Arrayas, Manuel [Departamento de Electromagnetismo, Universidad Rey Juan Carlos, Tulipan s/n, 28933 Mostoles, Madrid (Spain); Fontelos, Marco A [Departamento de Matematicas, Instituto de Matematicas y Fisica Fundamental, Consejo Superior de Investigaciones CientIficas, C/Serrano 123, 28006 Madrid (Spain); Trueba, Jose L [Departamento de Electromagnetismo, Universidad Rey Juan Carlos, Tulipan s/n, 28933 Mostoles, Madrid (Spain)

    2006-12-21

    In this paper we study the effects of photoionization processes on the propagation of both negative and positive ionization fronts in streamer discharge. We show that negative fronts accelerate in the presence of photoionization events. The appearance and propagation of positive ionization fronts travelling with constant velocity is explained as the result of the combined effects of photoionization and electron diffusion. The photoionization range plays an important role in the selection of the velocity of the ionization front as we show in this work.

  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. Active learning of Pareto fronts.

    Science.gov (United States)

    Campigotto, Paolo; Passerini, Andrea; Battiti, Roberto

    2014-03-01

    This paper introduces the active learning of Pareto fronts (ALP) algorithm, a novel approach to recover the Pareto front of a multiobjective optimization problem. ALP casts the identification of the Pareto front into a supervised machine learning task. This approach enables an analytical model of the Pareto front to be built. The computational effort in generating the supervised information is reduced by an active learning strategy. In particular, the model is learned from a set of informative training objective vectors. The training objective vectors are approximated Pareto-optimal vectors obtained by solving different scalarized problem instances. The experimental results show that ALP achieves an accurate Pareto front approximation with a lower computational effort than state-of-the-art estimation of distribution algorithms and widely known genetic techniques.

  16. Geochemistry of Natural Redox Fronts

    International Nuclear Information System (INIS)

    Hofmann, B.A.

    1999-05-01

    Redox fronts are important geochemical boundaries which need to be considered in safety assessment of deep repositories for radioactive waste. In most cases, selected host-rock formations will be reducing due to the presence of ferrous minerals, sulphides, etc. During construction and operation of the repository, air will be introduced into the formation. After repository closure, oxidising conditions may persist locally until all oxygen is consumed. In the case of high-level waste, radiolysis of water may provide an additional source of oxidants. Oxidising conditions within a repository are thus possible and potentially have a strong influence on the mobility of many elements. The rate of movement of redox fronts, the boundary between oxidising and reducing environments, and their influence on migrating radionuclides are thus important factors influencing repository performance. The present report is a review of elemental behaviour at natural redox fronts, based on published information and work of the author. Redox fronts are geochemically and geometrically variable manifestations of a global interface between generally oxidising geochemical milieux in contact with the atmosphere and generally reducing milieux in contact with rocks containing ferrous iron, sulphide and/or organic carbon. A classification of redox fronts based on a subdivision into continental near-surface, marine near-surface, and deep environments is proposed. The global redox interface is often located close to the surface of rocks and sediments and, sometimes, within bodies of water. Temperature conditions are close to ambient. A deeper penetration of the global redox front to depths of several kilometres is found in basins containing oxidised sediments (red beds) and in some hydrothermal circulation systems. Temperatures at such deep redox fronts may reach 200 o C. Both near-surface and deep redox fronts are sites of formation of economic deposits of redox-sensitive elements, particularly of

  17. Volcanic risk; Risque volcanique

    Energy Technology Data Exchange (ETDEWEB)

    Rancon, J.P.; Baubron, J.C.

    1995-12-31

    This project follows the previous multi-disciplinary studies carried out by the French Bureau de Recherches Geologiques et Minieres (BRGM) on the two active volcanoes of the French lesser Antilles: Mt Pelee (Martinique) and Soufriere (Guadeloupe) for which geological maps and volcanic risk studies have been achieved. The research program comprises 5 parts: the study of pyroclastic deposits from recent eruptions of the two volcanoes for a better characterization of their eruptive phenomenology and a better definition of crisis scenarios; the study of deposits and structures of active volcanoes from Central America and the study of eruptive dynamics of andesite volcanoes for a transposition to Antilles` volcanoes; the starting of a methodological multi-disciplinary research (volcanology, geography, sociology...) on the volcanic risk analysis and on the management of a future crisis; and finally, the development of geochemical survey techniques (radon, CO{sub 2}, H{sub 2}O) on active volcanoes of Costa-Rica and Europe (Fournaise, Furnas, Etna) and their application to the Soufriere. (J.S.). 9 refs., 3 figs.

  18. 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.

  19. Hubble Captures Volcanic Eruption Plume From Io

    Science.gov (United States)

    1997-01-01

    The Hubble Space Telescope has snapped a picture of a 400-km-high (250-mile-high) plume of gas and dust from a volcanic eruption on Io, Jupiter's large innermost moon.Io was passing in front of Jupiter when this image was taken by the Wide Field and Planetary Camera 2 in July 1996. The plume appears as an orange patch just off the edge of Io in the eight o'clock position, against the blue background of Jupiter's clouds. Io's volcanic eruptions blasts material hundreds of kilometers into space in giant plumes of gas and dust. In this image, material must have been blown out of the volcano at more than 2,000 mph to form a plume of this size, which is the largest yet seen on Io.Until now, these plumes have only been seen by spacecraft near Jupiter, and their detection from the Earth-orbiting Hubble Space Telescope opens up new opportunities for long-term studies of these remarkable phenomena.The plume seen here is from Pele, one of Io's most powerful volcanos. Pele's eruptions have been seen before. In March 1979, the Voyager 1 spacecraft recorded a 300-km-high eruption cloud from Pele. But the volcano was inactive when the Voyager 2 spacecraft flew by Jupiter in July 1979. This Hubble observation is the first glimpse of a Pele eruption plume since the Voyager expeditions.Io's volcanic plumes are much taller than those produced by terrestrial volcanos because of a combination of factors. The moon's thin atmosphere offers no resistance to the expanding volcanic gases; its weak gravity (one-sixth that of Earth) allows material to climb higher before falling; and its biggest volcanos are more powerful than most of Earth's volcanos.This image is a contrast-enhanced composite of an ultraviolet image (2600 Angstrom wavelength), shown in blue, and a violet image (4100 Angstrom wavelength), shown in orange. The orange color probably occurs because of the absorption and/or scattering of ultraviolet light in the plume. This light from Jupiter passes through the plume and is

  20. Seismic evidence for arc segmentation, active magmatic intrusions and syn-rift fault system in the northern Ryukyu volcanic arc

    Science.gov (United States)

    Arai, Ryuta; Kodaira, Shuichi; Takahashi, Tsutomu; Miura, Seiichi; Kaneda, Yoshiyuki

    2018-04-01

    Tectonic and volcanic structures of the northern Ryukyu arc are investigated on the basis of multichannel seismic (MCS) reflection data. The study area forms an active volcanic front in parallel to the non-volcanic island chain in the eastern margin of the Eurasian plate and has been undergoing regional extension on its back-arc side. We carried out a MCS reflection experiment along two across-arc lines, and one of the profiles was laid out across the Tokara Channel, a linear bathymetric depression which demarcates the northern and central Ryukyu arcs. The reflection image reveals that beneath this topographic valley there exists a 3-km-deep sedimentary basin atop the arc crust, suggesting that the arc segment boundary was formed by rapid and focused subsidence of the arc crust driven by the arc-parallel extension. Around the volcanic front, magmatic conduits represented by tubular transparent bodies in the reflection images are well developed within the shallow sediments and some of them are accompanied by small fragments of dipping seismic reflectors indicating intruded sills at their bottoms. The spatial distribution of the conduits may suggest that the arc volcanism has multiple active outlets on the seafloor which bifurcate at crustal depths and/or that the location of the volcanic front has been migrating trenchward over time. Further distant from the volcanic front toward the back-arc (> 30 km away), these volcanic features vanish, and alternatively wide rift basins become predominant where rapid transitions from normal-fault-dominant regions to strike-slip-fault-dominant regions occur. This spatial variation in faulting patterns indicates complex stress regimes associated with arc/back-arc rifting in the northern Okinawa Trough.[Figure not available: see fulltext.

  1. 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

  2. "Front" hotshet izvinitsja / Aleksandr Ikonnikov

    Index Scriptorium Estoniae

    Ikonnikov, Aleksandr

    2003-01-01

    Põhiliselt vene rahvusest noori ühendava liikumise "Front" esindajad kavatsevad kohtuda USA suursaadikuga Eestis ja vabandada kevadel suursaatkonna ees vägivallatsemisega lõppenud meeleavalduse pärast

  3. Energy conversion at dipolarization fronts

    Science.gov (United States)

    Khotyaintsev, Yu. V.; Divin, A.; Vaivads, A.; André, M.; Markidis, S.

    2017-02-01

    We use multispacecraft observations by Cluster in the Earth's magnetotail and 3-D particle-in-cell simulations to investigate conversion of electromagnetic energy at the front of a fast plasma jet. We find that the major energy conversion is happening in the Earth (laboratory) frame, where the electromagnetic energy is being transferred from the electromagnetic field to particles. This process operates in a region with size of the order several ion inertial lengths across the jet front, and the primary contribution to E·j is coming from the motional electric field and the ion current. In the frame of the front we find fluctuating energy conversion with localized loads and generators at sub-ion scales which are primarily related to the lower hybrid drift instability excited at the front; however, these provide relatively small net energy conversion.

  4. Closer look at lunar volcanism

    International Nuclear Information System (INIS)

    Vaniman, D.T.; Heiken, G.; Taylor, G.J.

    1984-01-01

    Although the American Apollo and Soviet Luna missions concentrated on mare basalt samples, major questions remain about lunar volcanism. Lunar field work will be indispensable for resolving the scientific questions about ages, compositions, and eruption processes of lunar volcanism. From a utilitarian standpoint, a better knowledge of lunar volcanism will also yield profitable returns in lunar base construction (e.g., exploitation of rille or lava-tube structures) and in access to materials such as volatile elements, pure glass, or ilmenite for lunar industry

  5. Volcanology: Volcanic bipolar disorder explained

    Science.gov (United States)

    Jellinek, Mark

    2014-02-01

    Eruptions come in a range of magnitudes. Numerical simulations and laboratory experiments show that rare, giant super-eruptions and smaller, more frequent events reflect a transition in the essential driving forces for volcanism.

  6. Lidar sounding of volcanic plumes

    Science.gov (United States)

    Fiorani, Luca; Aiuppa, Alessandro; Angelini, Federico; Borelli, Rodolfo; Del Franco, Mario; Murra, Daniele; Pistilli, Marco; Puiu, Adriana; Santoro, Simone

    2013-10-01

    Accurate knowledge of gas composition in volcanic plumes has high scientific and societal value. On the one hand, it gives information on the geophysical processes taking place inside volcanos; on the other hand, it provides alert on possible eruptions. For this reasons, it has been suggested to monitor volcanic plumes by lidar. In particular, one of the aims of the FP7 ERC project BRIDGE is the measurement of CO2 concentration in volcanic gases by differential absorption lidar. This is a very challenging task due to the harsh environment, the narrowness and weakness of the CO2 absorption lines and the difficulty to procure a suitable laser source. This paper, after a review on remote sensing of volcanic plumes, reports on the current progress of the lidar system.

  7. Volcanic eruption plumes on Io

    International Nuclear Information System (INIS)

    Strom, R.G.; Terrile, R.J.; Masursky, H.; Hansen, C.

    1979-01-01

    The detection of an umbrella-shaped plume extending about 280 km above the bright limb of Io was one of the most important discoveries made during the Voyager 1 encounter with the jovian system. This discovery proves that Io is volcanically active at present, and the number and magnitude of these eruptions indicate that Io is the most volcanically active body so far discovered in the Solar System. Preliminary analyses of these eruptive plumes are presented. (U.K.)

  8. 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.

  9. Volcanic crisis in

    Directory of Open Access Journals (Sweden)

    Mgs. Víctor Manuel Pérez Martínez

    2007-01-01

    Full Text Available The article is the result of an investigation which is focussed on some deontological aspects of the scientificjournalism. In the first place it gives a theoretical vision about science, journalism, internet and including some reflectionsabout the deontological principles in handling the information about science and technology. This focus is useful as it formsthe base of an investigation where we deal with the information about a possible ”volcanic crisis” in El Teide during the years2004-2005 done by the digital newspaper” El Dïa” a canarian newspaper from Tenerife. The work required the revision of theinformation which was published and a followed analysis of its context. It was used the digital version with the purpose ofvisualizing the news which was published. It was also compared with a printed version, with local cover but divulged theinformation to the public who was most affected by this particular news. The results give rise to some questions regardinghow the information is given to a topic which is of local interest as well as national and international interest due to therepercussions in the social, economical and tourist field (the tourist field is the main industrial sector in Tenerife by receivingthis type of news.

  10. Characteristic wave fronts in magnetohydrodynamics

    International Nuclear Information System (INIS)

    Menon, V.V.; Sharma, V.D.

    1981-01-01

    The influence of magnetic field on the process of steepening or flattening of the characteristic wave fronts in a plane and cylindrically symmetric motion of an ideal plasma is investigated. This aspect of the problem has not been considered until now. Remarkable differences between plane, cylindrical diverging, and cylindrical converging waves are discovered. The discontinuity in the velocity gradient at the wave front is shown to satisfy a Bernoulli-type equation. The discussion of the solutions of such equations reported in the literature is shown to be incomplete, and three general theorems are established. 18 refs

  11. Correlations between silicic volcanic rocks of the St Mary's Islands (southwestern India) and eastern Madagascar

    DEFF Research Database (Denmark)

    Melluso, Leone; Sheth, Hetu C.; Mahoney, John J.

    2009-01-01

    The St Mary's, Islands (southwestern India) expose silicic volcanic and sub-volcanic rocks (rhyolites and granophyric dacites) emplaced contemporaneously with the Cretaceous igneous province of Madagascar, roughly 88-90 Ma ago. I he St Mary's Islands rocks have phenocrysts of plagioclase...... and isotopic Compositions very close to those of rhyolites exposed between Vatomandry Ilaka and Mananjary in eastern Madagascar, and are distinctly different from rhyolites front other sectors of the Madagascan province. We therefore postulate that the St Mary's and the Vatomandry-Ilaka Mananjary silicic rock...

  12. Align the Front End First.

    Science.gov (United States)

    Perry, Jim

    1995-01-01

    Discussion of management styles and front-end analysis focuses on a review of Douglas McGregor's theories. Topics include Theories X, Y, and Z; leadership skills; motivational needs of employees; intrinsic and extrinsic rewards; and faulty implementation of instructional systems design processes. (LRW)

  13. Rate of volcanism on Venus

    International Nuclear Information System (INIS)

    Fegley, B. Jr.; Prinn, R.G.

    1988-07-01

    The maintenance of the global H 2 SO 4 clouds on Venus requires volcanism to replenish the atmospheric SO 2 which is continually being removed from the atmosphere by reaction with calcium minerals on the surface of Venus. The first laboratory measurements of the rate of one such reaction, between SO 2 and calcite (CaCO 3 ) to form anhydrite (CaSO 4 ), are reported. If the rate of this reaction is representative of the SO 2 reaction rate at the Venus surface, then we estimate that all SO 2 in the Venus atmosphere (and thus the H 2 SO 4 clouds) will be removed in 1.9 million years unless the lost SO 2 is replenished by volcanism. The required rate of volcanism ranges from about 0.4 to about 11 cu km of magma erupted per year, depending on the assumed sulfur content of the erupted material. If this material has the same composition as the Venus surface at the Venera 13, 14 and Vega 2 landing sites, then the required rate of volcanism is about 1 cu km per year. This independent geochemically estimated rate can be used to determine if either (or neither) of the two discordant (2 cu km/year vs. 200 to 300 cu km/year) geophysically estimated rates is correct. The geochemically estimated rate also suggests that Venus is less volcanically active than the Earth

  14. Volcanic Eruptions in Kamchatka

    Science.gov (United States)

    2007-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] Sheveluch Stratovolcano Click on the image for full resolution TIFF Klyuchevskoy Stratovolcano Click on the image for full resolution TIFF One of the most volcanically active regions of the world is the Kamchatka Peninsula in eastern Siberia, Russia. It is not uncommon for several volcanoes to be erupting at the same time. On April 26, 2007, the Advanced Spaceborne Thermal Emission and Reflection Radioneter (ASTER) on NASA's Terra spacecraft captured these images of the Klyuchevskoy and Sheveluch stratovolcanoes, erupting simultaneously, and 80 kilometers (50 miles) apart. Over Klyuchevskoy, the thermal infrared data (overlaid in red) indicates that two open-channel lava flows are descending the northwest flank of the volcano. Also visible is an ash-and-water plume extending to the east. Sheveluch volcano is partially cloud-covered. The hot flows highlighted in red come from a lava dome at the summit. They are avalanches of material from the dome, and pyroclastic flows. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER images Earth to map and monitor the changing surface of our planet. ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra spacecraft. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. The broad spectral coverage and high spectral resolution of ASTER provides scientists in numerous disciplines with critical information for surface mapping, and monitoring of dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and

  15. Geologic field-trip guide to the volcanic and hydrothermal landscape of the Yellowstone Plateau

    Science.gov (United States)

    Morgan Morzel, Lisa Ann; Shanks, W. C. Pat; Lowenstern, Jacob B.; Farrell, Jamie M.; Robinson, Joel E.

    2017-11-20

    Yellowstone National Park, a nearly 9,000 km2 (~3,468 mi2) area, was preserved in 1872 as the world’s first national park for its unique, extraordinary, and magnificent natural features. Rimmed by a crescent of older mountainous terrain, Yellowstone National Park has at its core the Quaternary Yellowstone Plateau, an undulating landscape shaped by forces of late Cenozoic explosive and effusive volcanism, on-going tectonism, glaciation, and hydrothermal activity. The Yellowstone Caldera is the centerpiece of the Yellowstone Plateau. The Yellowstone Plateau lies at the most northeastern front of the 17-Ma Yellowstone hot spot track, one of the few places on Earth where time-transgressive processes on continental crust can be observed in the volcanic and tectonic (faulting and uplift) record at the rate and direction predicted by plate motion. Over six days, this field trip presents an intensive overview into volcanism, tectonism, and hydrothermal activity on the Yellowstone Plateau (fig. 1). Field stops are linked directly to conceptual models related to monitoring of the various volcanic, geochemical, hydrothermal, and tectonic aspects of the greater Yellowstone system. Recent interest in young and possible future volcanism at Yellowstone as well as new discoveries and synthesis of previous studies, (for example, tomographic, deformation, gas, aeromagnetic, bathymetric, and seismic surveys), provide a framework in which to discuss volcanic, hydrothermal, and seismic activity in this dynamic region.

  16. K-Ar chronological study of the quaternary volcanic activity in Shin-etsu Highland

    International Nuclear Information System (INIS)

    Kaneko, Takayuki; Shimizu, Satoshi; Itaya, Tetsumaru.

    1989-01-01

    In order to clarify the temporal and spatial patterns in arc volcanism, 55 K-Ar ages of volcanic rocks from 17 volcanoes in Shin-etsu Highland, central Japan were determined. In addition, life spans, volume of erupted materials and eruption rates of each volcano were estimated. Graphical analysis demonstrates that volume of ejecta varies proportionately with both life span and eruption rate, and that there is no significant correlation between eruption rate and distance from the volcanic front. The life span of each volcano in this Highland is less than 0.6 m.y. In the central Shiga and southern Asama area, the volcanism started at 1 Ma and is still active. However the former had a peak in the activity at around 0.5 Ma, while the latter is apparently most intense at present. Northern Kenashi area has the volcanism without peak in 1.7 - 0.2 Ma, though the activity within a volcanic cluster or chain in central Japan lasts generally for 1 m.y. or less with a peak. (author)

  17. 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.

  18. The Lathrop Wells volcanic center

    International Nuclear Information System (INIS)

    Crowe, B.; Morley, R.

    1992-01-01

    The Lathrop Wells volcanic center is located 20 km south of the potential Yucca Mountain site, at the south end of the Yucca Mountain range. This paper discusses a detailed Study Plan which was prepared describing planned geochronology and field studies to assess the chronology of the Lathrop Wells volcanic center and other Quaternary volcanic centers in the region. A paper was published discussing the geomorphic and soil evidence for a late Pleistocene or Holoceno age for the main cone of the center. The purpose of this paper was to expose the ideas concerning the age of the Lathrop Wells center to scientific scrutiny. Additionally, field evidence was described suggesting the Lathrop Wells center may have formed from multiple eruptive events with significant intervals of no activity between events. This interpretation breaks with established convention in the volcanological literature that small volume basalt centers are monogenetic

  19. Tectonic, volcanic, and climatic geomorphology study of the Sierras Pampeanas Andes, northwestern Argentina

    Science.gov (United States)

    Bloom, A. L.; Strecker, M. R.; Fielding, E. J.

    1984-01-01

    A proposed analysis of Shuttle Imaging Radar-B (SIR-B) data extends current research in the Sierras Pampeanas and the Puna of northwestern Argentina to the determination - by the digital analysis of mountain-front sinuousity - of the relative age and amount of fault movement along mountain fronts of the late-Cenozoic Sierras Pampeanas basement blocks; the determination of the age and history of the boundary across the Andes at about 27 S latitude between continuing volcanism to the north and inactive volcanism to the south; and the determination of the age and extent of Pleistocene glaciation in the High Sierras, as well as the comparative importance of climatic change and tectonic movements in shaping the landscape. The integration of these studies into other ongoing geology projects contributes to the understanding of landform development in this active tectonic environment and helps distinguish between climatic and tectonic effects on landforms.

  20. Recurrence models of volcanic events: Applications to volcanic risk assessment

    International Nuclear Information System (INIS)

    Crowe, B.M.; Picard, R.; Valentine, G.; Perry, F.V.

    1992-01-01

    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 2 area of Yucca Mountain by ascending basalt magma was bounded by the range of 10 -8 to 10 -10 yr -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

  1. The Volcanism Ontology (VO): a model of the volcanic system

    Science.gov (United States)

    Myer, J.; Babaie, H. A.

    2017-12-01

    We have modeled a part of the complex material and process entities and properties of the volcanic system in the Volcanism Ontology (VO) applying several top-level ontologies such as Basic Formal Ontology (BFO), SWEET, and Ontology of Physics for Biology (OPB) within a single framework. The continuant concepts in BFO describe features with instances that persist as wholes through time and have qualities (attributes) that may change (e.g., state, composition, and location). In VO, the continuants include lava, volcanic rock, and volcano. The occurrent concepts in BFO include processes, their temporal boundaries, and the spatio-temporal regions within which they occur. In VO, these include eruption (process), the onset of pyroclastic flow (temporal boundary), and the space and time span of the crystallization of lava in a lava tube (spatio-temporal region). These processes can be of physical (e.g., debris flow, crystallization, injection), atmospheric (e.g., vapor emission, ash particles blocking solar radiation), hydrological (e.g., diffusion of water vapor, hot spring), thermal (e.g., cooling of lava) and other types. The properties (predicates) relate continuants to other continuants, occurrents to continuants, and occurrents to occurrents. The ontology also models other concepts such as laboratory and field procedures by volcanologists, sampling by sensors, and the type of instruments applied in monitoring volcanic activity. When deployed on the web, VO will be used to explicitly and formally annotate data and information collected by volcanologists based on domain knowledge. This will enable the integration of global volcanic data and improve the interoperability of software that deal with such data.

  2. Light front quantum chromodynamics: Towards phenomenology

    Indian Academy of Sciences (India)

    Light front dynamics; quantum chromodynamics; deep inelastic scattering. PACS Nos 11.10. ... What makes light front dynamics appealing from high energy phenomenology point of view? .... given in terms of Poincarй generators by. MВ = W P ...

  3. Front Propagation in Stochastic Neural Fields

    KAUST Repository

    Bressloff, Paul C.; Webber, Matthew A.

    2012-01-01

    We analyze the effects of extrinsic multiplicative noise on front propagation in a scalar neural field with excitatory connections. Using a separation of time scales, we represent the fluctuating front in terms of a diffusive-like displacement

  4. Candidate constructional volcanic edifices on Mercury

    OpenAIRE

    Wright, J.; Rothery, D. A.; Balme, M. R.; Conway, S. J.

    2018-01-01

    [Introduction] Studies using MESSENGER data suggest that Mercury’s crust is predominantly a product of effusive volcanism that occurred in the first billion years following the planet’s formation. Despite this planet-wide effusive volcanism, no constructional volcanic edifices, characterized by a topographic rise, have hitherto been robustly identified on Mercury, whereas constructional volcanoes are common on other planetary bodies in the solar system with volcanic histories. Here, we descri...

  5. Seabirds and fronts: a brief overview

    OpenAIRE

    Schneider, David C.

    1990-01-01

    Oceanographic fronts are the sites of enhanced physical and biological activity, including locally concentrated feeding by marine birds. Two general hypotheses relating marine birds to fronts have been developed. The first is that enhanced primary production at fronts increases prey supply through increased animal growth, reproduction, or immigration. The second is that prey patches develop at fronts either through behavioural responses of prey to thermal or salinity gradients, or through int...

  6. Disruptive event analysis: volcanism and igneous intrusion

    International Nuclear Information System (INIS)

    Crowe, B.M.

    1979-01-01

    Three basic topics are addressed for the disruptive event analysis: first, the range of disruptive consequences of a radioactive waste repository by volcanic activity; second, the possible reduction of the risk of disruption by volcanic activity through selective siting of a repository; and third, the quantification of the probability of repository disruption by volcanic activity

  7. Fluctuation charge effects in ionization fronts

    International Nuclear Information System (INIS)

    Arrayas, Manuel; Trueba, Jose L; Baltanas, J P

    2008-01-01

    In this paper, we study the effects of charge fluctuations on the propagation of both negative and positive ionization fronts in streamer discharges. We show that fronts accelerate when random charge creation events are present. This effect might play a similar role to photoionization in order to make the front move faster

  8. Fluctuation charge effects in ionization fronts

    Energy Technology Data Exchange (ETDEWEB)

    Arrayas, Manuel; Trueba, Jose L [Area de Electromagnetismo, Universidad Rey Juan Carlos, Camino del Molino s/n, 28943 Fuenlabrada, Madrid (Spain); Baltanas, J P [Departamento de Fisica Aplicada II, Universidad de Sevilla, Av. Reina Mercedes 2, 41012 Sevilla (Spain)

    2008-05-21

    In this paper, we study the effects of charge fluctuations on the propagation of both negative and positive ionization fronts in streamer discharges. We show that fronts accelerate when random charge creation events are present. This effect might play a similar role to photoionization in order to make the front move faster.

  9. A Volcanic Hydrogen Habitable Zone

    International Nuclear Information System (INIS)

    Ramirez, Ramses M.; Kaltenegger, Lisa

    2017-01-01

    The classical habitable zone (HZ) is the circular region around a star in which liquid water could exist on the surface of a rocky planet. The outer edge of the traditional N_2–CO_2–H_2O HZ extends out to nearly ∼1.7 au in our solar system, beyond which condensation and scattering by CO_2 outstrips its greenhouse capacity. Here, we show that volcanic outgassing of atmospheric H_2 can extend the outer edge of the HZ to ∼2.4 au in our solar system. This wider volcanic-hydrogen HZ (N_2–CO_2–H_2O–H_2) can be sustained as long as volcanic H_2 output offsets its escape from the top of the atmosphere. We use a single-column radiative-convective climate model to compute the HZ limits of this volcanic hydrogen HZ for hydrogen concentrations between 1% and 50%, assuming diffusion-limited atmospheric escape. At a hydrogen concentration of 50%, the effective stellar flux required to support the outer edge decreases by ∼35%–60% for M–A stars. The corresponding orbital distances increase by ∼30%–60%. The inner edge of this HZ only moves out ∼0.1%–4% relative to the classical HZ because H_2 warming is reduced in dense H_2O atmospheres. The atmospheric scale heights of such volcanic H_2 atmospheres near the outer edge of the HZ also increase, facilitating remote detection of atmospheric signatures.

  10. A Volcanic Hydrogen Habitable Zone

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez, Ramses M.; Kaltenegger, Lisa, E-mail: rmr277@cornell.edu [Carl Sagan Institute, Cornell University, Ithaca, NY (United States)

    2017-03-01

    The classical habitable zone (HZ) is the circular region around a star in which liquid water could exist on the surface of a rocky planet. The outer edge of the traditional N{sub 2}–CO{sub 2}–H{sub 2}O HZ extends out to nearly ∼1.7 au in our solar system, beyond which condensation and scattering by CO{sub 2} outstrips its greenhouse capacity. Here, we show that volcanic outgassing of atmospheric H{sub 2} can extend the outer edge of the HZ to ∼2.4 au in our solar system. This wider volcanic-hydrogen HZ (N{sub 2}–CO{sub 2}–H{sub 2}O–H{sub 2}) can be sustained as long as volcanic H{sub 2} output offsets its escape from the top of the atmosphere. We use a single-column radiative-convective climate model to compute the HZ limits of this volcanic hydrogen HZ for hydrogen concentrations between 1% and 50%, assuming diffusion-limited atmospheric escape. At a hydrogen concentration of 50%, the effective stellar flux required to support the outer edge decreases by ∼35%–60% for M–A stars. The corresponding orbital distances increase by ∼30%–60%. The inner edge of this HZ only moves out ∼0.1%–4% relative to the classical HZ because H{sub 2} warming is reduced in dense H{sub 2}O atmospheres. The atmospheric scale heights of such volcanic H{sub 2} atmospheres near the outer edge of the HZ also increase, facilitating remote detection of atmospheric signatures.

  11. Hydrodynamic instabilities in an ablation front

    International Nuclear Information System (INIS)

    Piriz, A R; Portugues, R F

    2004-01-01

    The hydrodynamic stability of an ablation front is studied for situations in which the wavelength of the perturbations is larger than the distance to the critical surface where the driving radiation is absorbed. An analytical model is presented, and it shows that under conditions in which the thermal flux is limited within the supercritical region of the ablative corona, the front may behave like a flame or like an ablation front, depending on the perturbation wavelength. For relatively long wavelengths the critical and ablation surfaces practically lump together into a unique surface and the front behaves like a flame, whereas for the shortest wavelengths the ablation front substructure is resolved

  12. Hydrodynamic instabilities in an ablation front

    Energy Technology Data Exchange (ETDEWEB)

    Piriz, A R; Portugues, R F [E.T.S.I. Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain)

    2004-06-01

    The hydrodynamic stability of an ablation front is studied for situations in which the wavelength of the perturbations is larger than the distance to the critical surface where the driving radiation is absorbed. An analytical model is presented, and it shows that under conditions in which the thermal flux is limited within the supercritical region of the ablative corona, the front may behave like a flame or like an ablation front, depending on the perturbation wavelength. For relatively long wavelengths the critical and ablation surfaces practically lump together into a unique surface and the front behaves like a flame, whereas for the shortest wavelengths the ablation front substructure is resolved.

  13. Dipolarization Fronts from Reconnection Onset

    Science.gov (United States)

    Sitnov, M. I.; Swisdak, M. M.; Merkin, V. G.; Buzulukova, N.; Moore, T. E.

    2012-12-01

    Dipolarization fronts observed in the magnetotail are often viewed as signatures of bursty magnetic reconnection. However, until recently spontaneous reconnection was considered to be fully prohibited in the magnetotail geometry because of the linear stability of the ion tearing mode. Recent theoretical studies showed that spontaneous reconnection could be possible in the magnetotail geometries with the accumulation of magnetic flux at the tailward end of the thin current sheet, a distinctive feature of the magnetotail prior to substorm onset. That result was confirmed by open-boundary full-particle simulations of 2D current sheet equilibria, where two magnetotails were separated by an equilibrium X-line and weak external electric field was imposed to nudge the system toward the instability threshold. To investigate the roles of the equilibrium X-line, driving electric field and other parameters in the reconnection onset process we performed a set of 2D PIC runs with different initial settings. The investigated parameter space includes the critical current sheet thickness, flux tube volume per unit magnetic flux and the north-south component of the magnetic field. Such an investigation is critically important for the implementation of kinetic reconnection onset criteria into global MHD codes. The results are compared with Geotail visualization of the magnetotail during substorms, as well as Cluster and THEMIS observations of dipolarization fronts.

  14. Holocene volcanic geology, volcanic hazard, and risk on Taveuni, Fiji

    International Nuclear Information System (INIS)

    Cronin, S.J.; Neall, V.E.

    2001-01-01

    The Holocene volcanic geology of Taveuni has been mapped in order to produce a volcanic hazard and risk assessment for the island. Taveuni is the third-largest island of the Fiji group and home to 14,500 people. At least cubic km 2.7 of olivine-alkali-basalt magma was erupted from over 100 events throughout the Holocene. Vents are concentrated along a northeast-striking rift zone that is parallel to other regional structural trends. There is an overall trend of younging southward along the rift. Holocene lavas and tephras are grouped within six newly defined eruptive periods, established on a basis of radiocarbon dating. Within these periods, 14 tephra layers, useful as local marker horizons, are recognised. At least 58% of Holocene eruptions produced lava flows, while almost all produced some tephra. Individual eruption event volumes ranged between 0.001 and cubic km 0.20 (dense rock equivalent). Many eruptions involved at least some phases of phreatic and/or phreato-magmatic activity, although dominant hydrovolcanic activity was limited to only a few events. A volcanic hazard map is presented, based on the Holocene geology map and statistical analyses of eruption recurrence. The highest levels of ground-based and near-vent hazards are concentrated along the southern portion of the island's rift axis, with the paths of initial lava flows predicted from present topography. Tephra fall hazards are based on eruption parameters interpreted from mapped Holocene tephra layers. Hawaiian explosive-style eruptions appear to be a dominant eruptive process, with prevailing low-level (<3 km) southeasterly winds dispersing most tephra to the northwestern quadrant. Vulnerable elements (population centres, infrastructure, and economy) on Taveuni have been considered in deriving a volcanic risk assessment for the island. A number of infrastructural and subdivision developments are either under way or planned for the island, driven by its highly fertile soils and availability of

  15. Can rain cause volcanic eruptions?

    Science.gov (United States)

    Mastin, Larry G.

    1993-01-01

    Volcanic eruptions are renowned for their violence and destructive power. This power comes ultimately from the heat and pressure of molten rock and its contained gases. Therefore we rarely consider the possibility that meteoric phenomena, like rainfall, could promote or inhibit their occurrence. Yet from time to time observers have suggested that weather may affect volcanic activity. In the late 1800's, for example, one of the first geologists to visit the island of Hawaii, J.D. Dana, speculated that rainfall influenced the occurrence of eruptions there. In the early 1900's, volcanologists suggested that some eruptions from Mount Lassen, Calif., were caused by the infiltration of snowmelt into the volcano's hot summit. Most such associations have not been provable because of lack of information; others have been dismissed after careful evaluation of the evidence.

  16. Source mechanisms of volcanic tsunamis.

    Science.gov (United States)

    Paris, Raphaël

    2015-10-28

    Volcanic tsunamis are generated by a variety of mechanisms, including volcano-tectonic earthquakes, slope instabilities, pyroclastic flows, underwater explosions, shock waves and caldera collapse. In this review, we focus on the lessons that can be learnt from past events and address the influence of parameters such as volume flux of mass flows, explosion energy or duration of caldera collapse on tsunami generation. The diversity of waves in terms of amplitude, period, form, dispersion, etc. poses difficulties for integration and harmonization of sources to be used for numerical models and probabilistic tsunami hazard maps. In many cases, monitoring and warning of volcanic tsunamis remain challenging (further technical and scientific developments being necessary) and must be coupled with policies of population preparedness. © 2015 The Author(s).

  17. Volcanic hazards in Central America

    Science.gov (United States)

    Rose, William I.; Bluth, Gregg J.S.; Carr, Michael J.; Ewert, John W.; Patino, Lina C.; Vallance, James W.

    2006-01-01

    This volume is a sampling of current scientific work about volcanoes in Central America with specific application to hazards. The papers reflect a variety of international and interdisciplinary collaborations and employ new methods. The book will be of interest to a broad cross section of scientists, especially volcanologists. The volume also will interest students who aspire to work in the field of volcano hazards mitigation or who may want to work in one of Earth’s most volcanically active areas.

  18. Long Valley caldera and the UCERF depiction of Sierra Nevada range-front faults

    Science.gov (United States)

    Hill, David P.; Montgomery-Brown, Emily K.

    2015-01-01

    Long Valley caldera lies within a left-stepping offset in the north-northwest-striking Sierra Nevada range-front normal faults with the Hilton Creek fault to the south and Hartley Springs fault to the north. Both Uniform California Earthquake Rupture Forecast (UCERF) 2 and its update, UCERF3, depict slip on these major range-front normal faults as extending well into the caldera, with significant normal slip on overlapping, subparallel segments separated by ∼10  km. This depiction is countered by (1) geologic evidence that normal faulting within the caldera consists of a series of graben structures associated with postcaldera magmatism (intrusion and tumescence) and not systematic down-to-the-east displacements consistent with distributed range-front faulting and (2) the lack of kinematic evidence for an evolving, postcaldera relay ramp structure between overlapping strands of the two range-front normal faults. The modifications to the UCERF depiction described here reduce the predicted shaking intensity within the caldera, and they are in accord with the tectonic influence that underlapped offset range-front faults have on seismicity patterns within the caldera associated with ongoing volcanic unrest.

  19. Volcanic deformation in the Andes

    Science.gov (United States)

    Riddick, S.; Fournier, T.; Pritchard, M.

    2009-05-01

    We present the results from an InSAR survey of volcanic activity in South America. We use data from the Japanese Space Agency's ALOS L-band radar satellite from 2006-2009. The L-band instrument provides better coherence in densely vegetated regions, compared to the shorter wave length C-band data. The survey reveals volcano related deformation in regions, north, central and southern, of the Andes volcanic arc. Since observations are limited to the austral summer, comprehensive coverage of all volcanoes is not possible. Yet, our combined observations reveal volcanic/hydrothermal deformation at Lonquimay, Llaima, Laguna del Maule, and Chaitén volcanoes, extend deformation measurements at Copahue, and illustrate temporal complexity to the previously described deformation at Cerro Hudson and Cordón Caulle. No precursory deformation is apparent before the large Chaitén eruption (VEI_5) of 2 May 2008, (at least before 16 April) suggesting rapid magma movement from depth at this long dormant volcano. Subsidence at Ticsani Volcano occurred coincident with an earthquake swarm in the same region.

  20. 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.

  1. Source mechanism of volcanic tremor

    Energy Technology Data Exchange (ETDEWEB)

    Ferrick, M.G.; Qamar, A.; St. Lawrence, W.F.

    1982-10-10

    Low-frequency (<10 Hz) volcanic earthquakes originate at a wide range of depths and occur before, during, and after magmatic eruptions. The characteristics of these earthquakes suggest that they are not typical tectonic events. Physically analogous processes occur in hydraulic fracturing of rock formations, low-frequency icequakes in temperate glaciers, and autoresonance in hydroelectric power stations. We propose that unsteady fluid flow in volcanic conduits is the common source mechanism of low-frequency volcanic earthquakes (tremor). The fluid dynamic source mechanism explains low-frequency earthquakes of arbitrary duration, magnitude, and depth of origin, as unsteady flow is independent of physical properties of the fluid and conduit. Fluid transients occur in both low-viscosity gases and high-viscosity liquids. A fluid transient analysis can be formulated as generally as is warranted by knowledge of the composition and physical properties of the fluid, material properties, geometry and roughness of the conduit, and boundary conditions. To demonstrate the analytical potential of the fluid dynamic theory, we consider a single-phase fluid, a melt of Mount Hood andesite at 1250/sup 0/C, in which significant pressure and velocity variations occur only in the longitudinal direction. Further simplification of the conservation of mass and momentum equations presents an eigenvalue problem that is solved to determine the natural frequencies and associated damping of flow and pressure oscillations.

  2. 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.

  3. Front Propagation in Stochastic Neural Fields

    KAUST Repository

    Bressloff, Paul C.

    2012-01-01

    We analyze the effects of extrinsic multiplicative noise on front propagation in a scalar neural field with excitatory connections. Using a separation of time scales, we represent the fluctuating front in terms of a diffusive-like displacement (wandering) of the front from its uniformly translating position at long time scales, and fluctuations in the front profile around its instantaneous position at short time scales. One major result of our analysis is a comparison between freely propagating fronts and fronts locked to an externally moving stimulus. We show that the latter are much more robust to noise, since the stochastic wandering of the mean front profile is described by an Ornstein-Uhlenbeck process rather than a Wiener process, so that the variance in front position saturates in the long time limit rather than increasing linearly with time. Finally, we consider a stochastic neural field that supports a pulled front in the deterministic limit, and show that the wandering of such a front is now subdiffusive. © 2012 Society for Industrial and Applied Mathematics.

  4. Disruptive event analysis: volcanism and igneous intrusion

    International Nuclear Information System (INIS)

    Crowe, B.M.

    1980-08-01

    An evaluation is made of the disruptive effects of volcanic activity with respect to long term isolation of radioactive waste through deep geologic storage. Three major questions are considered. First, what is the range of disruption effects of a radioactive waste repository by volcanic activity. Second, is it possible, by selective siting of a repository, to reduce the risk of disruption by future volcanic activity. And third, can the probability of repository disruption by volcanic activity be quantified. The main variables involved in the evaluation of the consequences of repository disruption by volcanic activity are the geometry of the magma-repository intersection (partly controlled by depth of burial) and the nature of volcanism. Potential radionuclide dispersal by volcanic transport within the biosphere ranges in distance from several kilometers to global. Risk from the most catastrophic types of eruptions can be reduced by careful site selection to maximize lag time prior to the onset of activity. Certain areas or volcanic provinces within the western United States have been sites of significant volcanism and should be avoided as potential sites for a radioactive waste repository. Examples of projection of future sites of active volcanism are discussed for three areas of the western United States. Probability calculations require two types of data: a numerical rate or frequency of volcanic activity and a numerical evaluation of the areal extent of volcanic disruption for a designated region. The former is clearly beyond the current state of art in volcanology. The latter can be approximated with a reasonable degree of satisfaction. In this report, simplified probability calculations are attempted for areas of past volcanic activity

  5. The upgraded Tevatron front end

    International Nuclear Information System (INIS)

    Glass, M.; Zagel, J.; Smith, P.; Marsh, W.; Smolucha, J.

    1990-01-01

    We are replacing the computers which support the CAMAC crates in the Fermilab accelerator control system. We want a significant performance increase, but we still want to be able to service scores of different varieties of CAMAC cards in a manner essentially transparent to console applications software. Our new architecture is based on symmetric multiprocessing. Several processors on the same bus, each running identical software, work simultaneously at satisfying different pieces of a console's request for data. We dynamically adjust the load between the processors. We can obtain more processing power by simply plugging in more processor cards and rebooting. We describe in this paper what we believe to be the interesting architectural features of the new front-end computers. We also note how we use some of the advanced features of the Multibus TM II bus and the Intel 80386 processor design to achieve reliability and expandability of both hardware and software. (orig.)

  6. Le front oriental de Lille

    Directory of Open Access Journals (Sweden)

    Étienne Poncelet

    2011-06-01

    Full Text Available De la porte d’eau de la Basse Deûle jusqu’au fort Saint-Sauveur, le front oriental de Lille, fortifié à l’époque espagnole, glisse ses courtines dans les entrelacs du périphérique et des gares. L’enjeu urbain actuel consiste à s’appuyer sur ces murs historiques pour « passer malgré tout » à travers cet écheveau urbain et retisser les fils de la continuité des promenades au cœur de la ville. Moins connus que le front occidental de la reine des citadelles, ces anciens espaces militaires sont une chance pour l’urbanisme de demain dont les opérations en cours de la Porte de Gand et de la Basse Deûle témoignent déjà.The east wall, at Lille, fortified during the period of Spanish occupation, extends from the Porte d'Eau de la Basse-Deûle to the Saint-Sauveur fort. Its curtain walls emerge today in a landscape of ring roads and railway territories. The issue today is to profit from these historic walls in order to make some sense of the urban chaos and to reinstate some urban continuity in the city-centre walkways. Although they are not as well known as the western wall of this major fortified city, these former military properties are an exciting opportunity for tomorrow's town-planners, as the operations already underway at the Porte de Gand et de la Basse Deûle suggest.

  7. Muon front end for the neutrino factory

    Directory of Open Access Journals (Sweden)

    C. T. Rogers

    2013-04-01

    Full Text Available In the neutrino factory, muons are produced by firing high-energy protons onto a target to produce pions. The pions decay to muons and pass through a capture channel known as the muon front end, before acceleration to 12.6 GeV. The muon front end comprises a variable frequency rf system for longitudinal capture and an ionization cooling channel. In this paper we detail recent improvements in the design of the muon front end.

  8. Muon front end for the neutrino factory

    CERN Document Server

    Rogers, C T; Prior, G; Gilardoni, S; Neuffer, D; Snopok, P; Alekou, A; Pasternak, J

    2013-01-01

    In the neutrino factory, muons are produced by firing high-energy protons onto a target to produce pions. The pions decay to muons and pass through a capture channel known as the muon front end, before acceleration to 12.6 GeV. The muon front end comprises a variable frequency rf system for longitudinal capture and an ionization cooling channel. In this paper we detail recent improvements in the design of the muon front end.

  9. Volcanic hazards and public response

    Science.gov (United States)

    Peterson, Donald W.

    1988-05-01

    Although scientific understanding of volcanoes is advancing, eruptions continue to take a substantial toll of life and property. Some of these losses could be reduced by better advance preparation, more effective flow of information between scientists and public officials, and better understanding of volcanic behavior by all segments of the public. The greatest losses generally occur at volcanoes that erupt infrequently where people are not accustomed to dealing with them. Scientists sometimes tend to feel that the blame for poor decisions in emergency management lies chiefly with officials or journalists because of their failure to understand the threat. However, the underlying problem embraces a set of more complex issues comprising three pervasive factors. The first factor is the volcano: signals given by restless volcanoes are often ambiguous and difficult to interpret, especially at long-quiescent volcanoes. The second factor is people: people confront hazardous volcanoes in widely divergent ways, and many have difficulty in dealing with the uncertainties inherent in volcanic unrest. The third factor is the scientists: volcanologists correctly place their highest priority on monitoring and hazard assessment, but they sometimes fail to explain clearly their conclusions to responsible officials and the public, which may lead to inadequate public response. Of all groups in society, volcanologists have the clearest understanding of the hazards and vagaries of volcanic activity; they thereby assume an ethical obligation to convey effectively their knowledge to benefit all of society. If society resists, their obligation nevertheless remains. They must use the same ingenuity and creativity in dealing with information for the public that they use in solving scientific problems. When this falls short, even excellent scientific results may be nullified.

  10. Thermal vesiculation during volcanic eruptions.

    Science.gov (United States)

    Lavallée, Yan; Dingwell, Donald B; Johnson, Jeffrey B; Cimarelli, Corrado; Hornby, Adrian J; Kendrick, Jackie E; von Aulock, Felix W; Kennedy, Ben M; Andrews, Benjamin J; Wadsworth, Fabian B; Rhodes, Emma; Chigna, Gustavo

    2015-12-24

    Terrestrial volcanic eruptions are the consequence of magmas ascending to the surface of the Earth. This ascent is driven by buoyancy forces, which are enhanced by bubble nucleation and growth (vesiculation) that reduce the density of magma. The development of vesicularity also greatly reduces the 'strength' of magma, a material parameter controlling fragmentation and thus the explosive potential of the liquid rock. The development of vesicularity in magmas has until now been viewed (both thermodynamically and kinetically) in terms of the pressure dependence of the solubility of water in the magma, and its role in driving gas saturation, exsolution and expansion during decompression. In contrast, the possible effects of the well documented negative temperature dependence of solubility of water in magma has largely been ignored. Recently, petrological constraints have demonstrated that considerable heating of magma may indeed be a common result of the latent heat of crystallization as well as viscous and frictional heating in areas of strain localization. Here we present field and experimental observations of magma vesiculation and fragmentation resulting from heating (rather than decompression). Textural analysis of volcanic ash from Santiaguito volcano in Guatemala reveals the presence of chemically heterogeneous filaments hosting micrometre-scale vesicles. The textures mirror those developed by disequilibrium melting induced via rapid heating during fault friction experiments, demonstrating that friction can generate sufficient heat to induce melting and vesiculation of hydrated silicic magma. Consideration of the experimentally determined temperature and pressure dependence of water solubility in magma reveals that, for many ascent paths, exsolution may be more efficiently achieved by heating than by decompression. We conclude that the thermal path experienced by magma during ascent strongly controls degassing, vesiculation, magma strength and the effusive

  11. Evaluation on changes caused by volcanic activities in the groundwater environment as a natural barrier for the HLW disposal. Literature survey and groundwater observation conducted at Mt. Iwate

    International Nuclear Information System (INIS)

    Mahara, Yasunori; Nakata, Eiji; Tanaka, Kazuhiro

    2000-01-01

    It is very important in the site characterization for the HLW disposal to understand changes in geochemical performances caused by volcanic activities in the groundwater environment as the natural barrier. The various effects and its magnitude of changes were listed up and were filed from literature surveys of the correlation between volcanic activities and hydrological can geochemical changes (e.g. water temperature, water pressure, water level, dissolved gas concentration of He and Rn, isotopic ratio of He, and chloride concentration) in volcanic aquifer. However, it is difficult to evaluate the magnitude of impacts, which volcanic activities will give to the groundwater environment in the natural barrier, through only the literature surveys. We have started monitoring of groundwater level and changes in groundwater quality, since volcanic activities have enhanced at Mt. Iwate from June in 1998. Judging from variation of isotopic ratio of dissolved He in groundwater, a prompt and sharp signals indicating volcanic activities will easily be found in shallow groundwater and discharged ponds. On the other hands, geochemical conditions in deep groundwater surroundings from some 100 m to 1000 m deep will be very stable, if the area being more than 5 km apart from the volcanic active center. Consequently, our observed results suggest that the groundwater environment which is not directly disturbed by the underground magmatic activities spreads under the area that is connected to trench side of the volcanic front. (author)

  12. Stability of cosmological deflagration fronts

    Science.gov (United States)

    Mégevand, Ariel; Membiela, Federico Agustín

    2014-05-01

    In a cosmological first-order phase transition, bubbles of the stable phase nucleate and expand in the supercooled metastable phase. In many cases, the growth of bubbles reaches a stationary state, with bubble walls propagating as detonations or deflagrations. However, these hydrodynamical solutions may be unstable under corrugation of the interface. Such instability may drastically alter some of the cosmological consequences of the phase transition. Here, we study the hydrodynamical stability of deflagration fronts. We improve upon previous studies by making a more careful and detailed analysis. In particular, we take into account the fact that the equation of motion for the phase interface depends separately on the temperature and fluid velocity on each side of the wall. Fluid variables on each side of the wall are similar for weakly first-order phase transitions, but differ significantly for stronger phase transitions. As a consequence, we find that, for large enough supercooling, any subsonic wall velocity becomes unstable. Moreover, as the velocity approaches the speed of sound, perturbations become unstable on all wavelengths. For smaller supercooling and small wall velocities, our results agree with those of previous works. Essentially, perturbations on large wavelengths are unstable, unless the wall velocity is higher than a critical value. We also find a previously unobserved range of marginally unstable wavelengths. We analyze the dynamical relevance of the instabilities, and we estimate the characteristic time and length scales associated with their growth. We discuss the implications for the electroweak phase transition and its cosmological consequences.

  13. Stability of cosmological detonation fronts

    Science.gov (United States)

    Mégevand, Ariel; Membiela, Federico Agustín

    2014-05-01

    The steady-state propagation of a phase-transition front is classified, according to hydrodynamics, as a deflagration or a detonation, depending on its velocity with respect to the fluid. These propagation modes are further divided into three types, namely, weak, Jouguet, and strong solutions, according to their disturbance of the fluid. However, some of these hydrodynamic modes will not be realized in a phase transition. One particular cause is the presence of instabilities. In this work we study the linear stability of weak detonations, which are generally believed to be stable. After discussing in detail the weak detonation solution, we consider small perturbations of the interface and the fluid configuration. When the balance between the driving and friction forces is taken into account, it turns out that there are actually two different kinds of weak detonations, which behave very differently as functions of the parameters. We show that the branch of stronger weak detonations are unstable, except very close to the Jouguet point, where our approach breaks down.

  14. Up front in the CIS

    International Nuclear Information System (INIS)

    Grey, C.A.

    1994-01-01

    A picture is drawn of the current supply side of the front-end fuel cycle production capacities in the CIS. Uranium production has been steadily declining, as in the West. Market realities have been reflected in local costs of production since the break-up of the former Soviet Union and some uneconomic mines have been closed. In terms of actual production, Kazakhstan, Russia and Uzbekistan, remain among the top five uranium producers in the world. Western government action has been taken to restrict the market access for natural uranium from the CIS. Reactors in the CIS continue to be supplied with fabricated fuel solely by Russian, though Western fuel fabricators have reduced Russian supplies to Eastern Europe. Russia's current dominance in conversion and enrichment services in both the CIS and Eastern Europe is likely to continue as long as the present surplus low enriched uranium stocks last and surplus production capacity exists. Market penetration in the West has been limited by government action but Russia in 1993 still held about 20% of the world's conversion market and nearly 19% of the enrichment market. (6 figures, 2 tables, 4 references) (UK)

  15. Application of up-front licensing

    International Nuclear Information System (INIS)

    Grant, S.D.; Snell, V.G.

    1995-01-01

    AECL has been pioneering 'up-front' licensing of new reactor designs. The CANDU 3 design has been formally reviewed by AECB staff for a number of years. The CANDU 9 design has just started the up-front licensing process. The process gives designers, regulators and potential customers early confidence in the licensability of future plants. (author). 4 refs., 2 tabs

  16. Application of up-front licensing

    Energy Technology Data Exchange (ETDEWEB)

    Grant, S D [Atomic Energy of Canada Ltd., Saskatoon, SK (Canada); Snell, V G [Atomic Energy of Canada Ltd., Mississauga, ON (Canada)

    1996-12-31

    AECL has been pioneering `up-front` licensing of new reactor designs. The CANDU 3 design has been formally reviewed by AECB staff for a number of years. The CANDU 9 design has just started the up-front licensing process. The process gives designers, regulators and potential customers early confidence in the licensability of future plants. (author). 4 refs., 2 tabs.

  17. RPC performance vs. front-end electronics

    International Nuclear Information System (INIS)

    Cardarelli, R.; Aielli, G.; Camarri, P.; Di Ciaccio, A.; Di Stante, L.; Liberti, B.; Pastori, E.; Santonico, R.; Zerbini, A.

    2012-01-01

    Moving the amplification from the gas to the front-end electronics was a milestone in the development of Resistive Plate Chambers. Here we discuss the historical evolution of RPCs and we show the results obtained with newly developed front-end electronics with threshold in the fC range.

  18. Through the EU's Back and Front Doors

    DEFF Research Database (Denmark)

    Adler-Nissen, Rebecca

    2015-01-01

    Through the EU's front- and backdoors: The selective Danish and Norwegian approaches in the Area of Freedom, Security and Justice Rebecca Adler-Nissen......Through the EU's front- and backdoors: The selective Danish and Norwegian approaches in the Area of Freedom, Security and Justice Rebecca Adler-Nissen...

  19. Control of a laser front wave

    International Nuclear Information System (INIS)

    Akaoka, K.; Wakaida, I.

    1996-01-01

    We controlled the laser wave front through a laser beam simulation experiment propagating through medium. Thus, we confirmed that the RMS, defined as the quadratic mean of the laser beam wave front, dropped to the 1/3 - 1/6 of the pre-control value

  20. Nuclear Physics on the Light Front

    OpenAIRE

    Miller, Gerald A.

    1999-01-01

    High energy scattering experiments involving nuclei are typically analyzed in terms of light front variables. The desire to provide realistic, relativistic wave functions expressed in terms of these variables led me to try to use light front dynamics to compute nuclear wave functions. The progress is summarized here.

  1. Wave fronts of electromagnetic cyclotron harmonic waves

    International Nuclear Information System (INIS)

    Ohnuma, T.; Watanabe, T.

    1982-01-01

    In an inhomogeneous high-density magnetized plasma, the spatial properties of the wave fronts and ray trajectories of electromagnetic ordinary and extraordinary cyclotron harmonic waves are investigated. Those waves which are radiated from a local source are found to have wave fronts which are almost parallel to the magnetic field. Also, the reflective properties of the electromagnetic cyclotron harmonic waves are confirmed

  2. End-Users, Front Ends and Librarians.

    Science.gov (United States)

    Bourne, Donna E.

    1989-01-01

    The increase in end-user searching, the advantages and limitations of front ends, and the role of the librarian in end-user searching are discussed. It is argued that librarians need to recognize that front ends can be of benefit to themselves and patrons, and to assume the role of advisors and educators for end-users. (37 references) (CLB)

  3. 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 (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 hazardous eruptions in Chile, Colombia, Ecuador, and Peru has spurred significant

  4. Electrostatic phenomena in volcanic eruptions

    Energy Technology Data Exchange (ETDEWEB)

    Lane, S J; James, M R; Gilbert, J S, E-mail: s.lane@lancaster.ac.uk [Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ (United Kingdom)

    2011-06-23

    Electrostatic phenomena have long been associated with the explosive eruption of volcanoes. Lightning generated in volcanic plumes is a spectacular atmospheric electrical event that requires development of large potential gradients over distances of up to kilometres. This process begins as hydrated liquid rock (magma) ascends towards Earth's surface. Pressure reduction causes water supersaturation in the magma and the development of bubbles of supercritical water, where deeper than c. 1000 m, and water vapour at shallower depths that drives flow expansion. The generation of high strain rates in the expanding bubbly magma can cause it to fracture in a brittle manner, as deformation relaxation timescales are exceeded. The brittle fracture provides the initial charge separation mechanism, known as fractoemission. The resulting mixture of charged silicate particles and ions evolves over time, generating macro-scale potential gradients in the atmosphere and driving processes such as particle aggregation. For the silicate particles, aggregation driven by electrostatic effects is most significant for particles smaller than c. 100 {mu}m. Aggregation acts to change the effective aerodynamic behaviour of silicate particles, thus altering the sedimentation rates of particles from volcanic plumes from the atmosphere. The presence of liquid phases also promotes aggregation processes and lightning.

  5. Cenozoic volcanic rocks of Saudi Arabia

    Science.gov (United States)

    Coleman, R.G.; Gregory, R.T.; Brown, G.F.

    2016-01-01

    The Cenozoic volcanic rocks of Saudi Arabia cover about 90,000 km2, one of the largest areas of alkali olivine basalt in the world. These volcanic rocks are in 13 separate fields near the eastern coast of the Red Sea and in the western Arabian Peninsula highlands from Syria southward to the Yemen Arab Republic.

  6. 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...... are isotopically similar to the Andean Southern Volcanic Zone arc rocks and their mantle source possibly resembled the source of South Atlantic N-MORB prior to addition of fluids and melts from the subduction channel. However, it must have been more enriched than the estimates of depleted upper mantle from...... the lithosphere is thinnest and possibly in areas of elevated mantle temperatures. The pyroxenite melts formed at deeper levels react with the surrounding peridotite and thereby changes composition leading to eruption of melts which experienced variable degrees of melt-peridotite interaction. This can presumably...

  7. Imaging of volcanic activity on Jupiter's moon Io by Galileo during the Galileo Europa Mission and the Galileo Millennium Mission

    Science.gov (United States)

    Keszthelyi, L.; McEwen, A.S.; Phillips, C.B.; Milazzo, M.; Geissler, P.; Turtle, E.P.; Radebaugh, J.; Williams, D.A.; Simonelli, D.P.; Breneman, H.H.; Klaasen, K.P.; Levanas, G.; Denk, T.; Alexander, D.D.A.; Capraro, K.; Chang, S.-H.; Chen, A.C.; Clark, J.; Conner, D.L.; Culver, A.; Handley, T.H.; Jensen, D.N.; Knight, D.D.; LaVoie, S.K.; McAuley, M.; Mego, V.; Montoya, O.; Mortensen, H.B.; Noland, S.J.; Patel, R.R.; Pauro, T.M.; Stanley, C.L.; Steinwand, D.J.; Thaller, T.F.; Woncik, P.J.; Yagi, G.M.; Yoshimizu, J.R.; Alvarez, Del; Castillo, E.M.; Belton, M.J.S.; Beyer, R.; Branston, D.; Fishburn, M.B.; Mueller, B.; Ragan, R.; Samarasinha, N.; Anger, C.D.; Cunningham, C.; Little, B.; Arriola, S.; Carr, M.H.; Asphaug, E.; Moore, J.; Morrison, D.; Rages, K.; Banfield, D.; Bell, M.; Burns, J.A.; Carcich, B.; Clark, B.; Currier, N.; Dauber, I.; Gierasch, P.J.; Helfenstein, P.; Mann, M.; Othman, O.; Rossier, L.; Solomon, N.; Sullivan, R.; Thomas, P.C.; Veverka, J.; Becker, T.; Edwards, K.; Gaddis, L.; Kirk, R.; Lee, E.; Rosanova, T.; Sucharski, R.M.; Beebe, R.F.; Simon, A.; Bender, K.; Chuang, F.; Fagents, S.; Figueredo, P.; Greeley, R.; Homan, K.; Kadel, S.; Kerr, J.; Klemaszewski, J.; Lo, E.; Schwarz, W.; Williams, K.; Bierhaus, E.; Brooks, S.; Chapman, C.R.; Merline, B.; Keller, J.; Schenk, P.; Tamblyn, P.; Bouchez, A.; Dyundian, U.; Ingersoll, A.P.; Showman, A.; Spitale, J.; Stewart, S.; Vasavada, A.; Cunningham, W.F.; Johnson, T.V.; Jones, T.J.; Kaufman, J.M.; Magee, K.P.; Meredith, M.K.; Orton, G.S.; Senske, D.A.; West, A.; Winther, D.; Collins, G.; Fripp, W.J.; Head, J. W.; Pappalardo, R.; Pratt, S.; Procter, L.; Spaun, N.; Colvin, T.; Davies, M.; DeJong, E.M.; Hall, J.; Suzuki, S.; Gorjian, Z.; Giese, B.; Koehler, U.; Neukum, G.; Oberst, J.; Roatsch, T.; Tost, W.; Schuster, P.; Wagner, R.; Dieter, N.; Durda, D.; Greenberg, R.J.; Hoppa, G.; Jaeger, W.; Plassman, J.; Tufts, R.; Fanale, F.P.; Gran,

    2001-01-01

    The Solid-State Imaging (SSI) instrument provided the first high- and medium-resolution views of Io as the Galileo spacecraft closed in on the volcanic body in late 1999 and early 2000. While each volcanic center has many unique features, the majority can be placed into one of two broad categories. The "Promethean" eruptions, typified by the volcanic center Prometheus, are characterized by long-lived steady eruptions producing a compound flow field emplaced in an insulating manner over a period of years to decades. In contrast, "Pillanian" eruptions are characterized by large pyroclastic deposits and short-lived but high effusion rate eruptions from fissures feeding open-channel or open-sheet flows. Both types of eruptions commonly have ???100-km-tall, bright, SO2-rich plumes forming near the flow fronts and smaller deposits of red material that mark the vent for the silicate lavas. Copyright 2001 by the American Geophysical Union.

  8. Geomorphological Approach for Regional Zoning In The Merapi Volcanic Area

    Directory of Open Access Journals (Sweden)

    Langgeng Wahyu Santosa

    2013-07-01

    Full Text Available Geomorphologial approach can be used as the basic for identifying and analyzing the natural resources potentials, especially in volcanic landscape. Based on its geomorphology, Merapi volcanic landscape can be divided into 5 morphological units, i.e.: volcanic cone, volcanic slope, volcanic foot, volcanic foot plain, and fluvio-volcanic plain. Each of these morphological units has specific characteristic and natural resources potential. Based on the condition of geomorphology, the regional zoning can be compiled to support the land use planning and to maintain the conservation of environmental function in the Merapi Volcanic area.

  9. Volcanic emissions from soils at the base of La Fossa volcano, Vulcano island, Italy

    Science.gov (United States)

    Obenholzner, J. H.; Parks, J. L.

    2006-12-01

    A top-sealed plastic tube with a diameter of ca. 15 cm had been buried vertically at the base of La Fossa volcano, Volcano island, Italy, next to the front of the obsidian flow. The tube had been filled with quartz wool to condense vapors emanating from the soil. At ca. 75 cm below the surface the sample had been exposed to vapors from Sept. 2005 to April 2006. The leached sample had not been in touch with the ground. Another glass wool cushion (ca. 3 cm thick) had been underneath to minimize capillary effects. Leaching of the quartz wool and ICP-MS analysis documented positive values for: Mg, Al, Si, P, K, Ca, Cr, Mn, Ni, Cu, Zn, Cd, Sn, Pb. Leaching with nitric acid documented also V and Fe. Acid leaching produced higher values for all elements, except K and Sn, than leaching with deionized water. Negative values had been obtained for As, Se, Mo. Influence from soil breathing can be excluded as the active fumaroles contain As and Se. This experiment documents for the first time an unknown element transport by vapors/gases through a volcanic edifice interacting with hydrothermal and magmatic gases. It remains unknown if elements detected are entering the atmosphere or are getting adsorbed onto the volcanic ash soil particles derived from reworked surge beds. This question is very important as soils might be an unknown filter medium to filter volcanically polluted air in case of major volcanic crises. Data can be obtained from the authors.

  10. Large Volcanic Rises on Venus

    Science.gov (United States)

    Smrekar, Suzanne E.; Kiefer, Walter S.; Stofan, Ellen R.

    1997-01-01

    Large volcanic rises on Venus have been interpreted as hotspots, or the surface manifestation of mantle upwelling, on the basis of their broad topographic rises, abundant volcanism, and large positive gravity anomalies. Hotspots offer an important opportunity to study the behavior of the lithosphere in response to mantle forces. In addition to the four previously known hotspots, Atla, Bell, Beta, and western Eistla Regiones, five new probable hotspots, Dione, central Eistla, eastern Eistla, Imdr, and Themis, have been identified in the Magellan radar, gravity and topography data. These nine regions exhibit a wider range of volcano-tectonic characteristics than previously recognized for venusian hotspots, and have been classified as rift-dominated (Atla, Beta), coronae-dominated (central and eastern Eistla, Themis), or volcano-dominated (Bell, Dione, western Eistla, Imdr). The apparent depths of compensation for these regions ranges from 65 to 260 km. New estimates of the elastic thickness, using the 90 deg and order spherical harmonic field, are 15-40 km at Bell Regio, and 25 km at western Eistla Regio. Phillips et al. find a value of 30 km at Atla Regio. Numerous models of lithospheric and mantle behavior have been proposed to interpret the gravity and topography signature of the hotspots, with most studies focusing on Atla or Beta Regiones. Convective models with Earth-like parameters result in estimates of the thickness of the thermal lithosphere of approximately 100 km. Models of stagnant lid convection or thermal thinning infer the thickness of the thermal lithosphere to be 300 km or more. Without additional constraints, any of the model fits are equally valid. The thinner thermal lithosphere estimates are most consistent with the volcanic and tectonic characteristics of the hotspots. Estimates of the thermal gradient based on estimates of the elastic thickness also support a relatively thin lithosphere (Phillips et al.). The advantage of larger estimates of

  11. Blocking-resistant communication through domain fronting

    Directory of Open Access Journals (Sweden)

    Fifield David

    2015-06-01

    Full Text Available We describe “domain fronting,” a versatile censorship circumvention technique that hides the remote endpoint of a communication. Domain fronting works at the application layer, using HTTPS, to communicate with a forbidden host while appearing to communicate with some other host, permitted by the censor. The key idea is the use of different domain names at different layers of communication. One domain appears on the “outside” of an HTTPS request—in the DNS request and TLS Server Name Indication—while another domain appears on the “inside”—in the HTTP Host header, invisible to the censor under HTTPS encryption. A censor, unable to distinguish fronted and nonfronted traffic to a domain, must choose between allowing circumvention traffic and blocking the domain entirely, which results in expensive collateral damage. Domain fronting is easy to deploy and use and does not require special cooperation by network intermediaries. We identify a number of hard-to-block web services, such as content delivery networks, that support domain-fronted connections and are useful for censorship circumvention. Domain fronting, in various forms, is now a circumvention workhorse. We describe several months of deployment experience in the Tor, Lantern, and Psiphon circumvention systems, whose domain-fronting transports now connect thousands of users daily and transfer many terabytes per month.

  12. Characterizing Ion Flows Across a Dipolarization Front

    Science.gov (United States)

    Arnold, H.; Drake, J. F.; Swisdak, M.

    2017-12-01

    In light of the Magnetospheric Multiscale Mission (MMS) moving to study predominately symmetric magnetic reconnection in the Earth's magnetotail, it is of interest to investigate various methods for determining the relative location of the satellites with respect to the x line or a dipolarization front. We use a 2.5 dimensional PIC simulation to explore the dependence of various characteristics of a front, or flux bundle, on the width of the front in the dawn-dusk direction. In particular, we characterize the ion flow in the x-GSM direction across the front. We find a linear relationship between the width of a front, w, and the maximum velocity of the ion flow in the x-GSM direction, Vxi, for small widths: Vxi/VA=w/di*1/2*(mVA2)/Ti*Bz/Bxwhere m, VA, di, Ti, Bz, and Bx are the ion mass, upstream Alfven speed, ion inertial length, ion temperature, and magnetic fields in the z-GSM and x-GSM directions respectively. However, once the width reaches around 5 di, the relationship gradually approaches the well-known theoretical limit for ion flows, the upstream Alfven speed. Furthermore, we note that there is a reversal in the Hall magnetic field near the current sheet on the positive y-GSM side of the front. This reversal is most likely due to conservation of momentum in the y-GSM direction as the ions accelerate towards the x-GSM direction. This indicates that while the ions are primarily energized in the x-GSM direction by the front, they transfer energy to the electromagnetic fields in the y-GSM direction. The former energy transfer is greater than the latter, but the reversal of the Hall magnetic field drags the frozen-in electrons along with it outside of the front. These simulations should better able researchers to determine the relative location of a satellite crossing a dipolarization front.

  13. Managing Controversies in the Fuzzy Front End

    DEFF Research Database (Denmark)

    Christiansen, John K.; Gasparin, Marta

    2016-01-01

    This research investigates the controversies that emerge in the fuzzy front end (FFE) and how they are closed so the innovation process can move on. The fuzzy front has been characterized in the literature as a very critical phase, but controversies in the FFE have not been studied before....... The analysis investigates the microprocesses around the controversies that emerge during the fuzzy front end of four products. Five different types of controversies are identified: profit, production, design, brand and customers/market. Each controversy represents a threat, but also an opportunity to search...

  14. Dinasour extinction and volcanic activity

    Science.gov (United States)

    Gledhill, J. A.

    There is at present some controversy about the reason for the mass extinction of dinosaurs and other forms of life at the end of the Cretaceous. A suggestion by Alvarez et al. [1980] that this was due to the collision of the earth with a meteorite 10 km or so in diameter has excited considerable interest [Silver and Schultz, 1982] and also some criticism [Stanley, 1984]. A recent publication [Wood, 1984] describing the catastrophic effects of a relatively minor lava flow in Iceland suggests that intense volcanic activity could have played a large part in the extinctions. In this letter it is pointed out that the Deccan lava flows in India took place in the appropriate time and may well have been of sufficient magnitude to be a major factor in the Cretaceous-Tertiary (C-T) boundary catastrophe.

  15. SPD very front end electronics

    International Nuclear Information System (INIS)

    Luengo, S.; Gascon, D.; Comerma, A.; Garrido, L.; Riera, J.; Tortella, S.; Vilasis, X.

    2006-01-01

    The Scintillator Pad Detector (SPD) is part of the LHCb calorimetry system [D. Breton, The front-end electronics for LHCb calorimeters, Tenth International Conference on Calorimetry in Particle Physics, CALOR, Pasadena, 2002] that provides high-energy hadron, electron and photon candidates for the first level trigger. The SPD is designed to distinguish electrons from photons. It consists of a plastic scintillator layer, divided into about 6000 cells of different size to obtain better granularity near the beam [S. Amato, et al., LHCb technical design report, CERN/LHCC/2000-0036, 2000]. Charged particles will produce, and photons will not, ionization in the scintillator. This ionization generates a light pulse that is collected by a WaveLength Shifting (WLS) fiber that is coiled inside the scintillator cell. The light is transmitted through a clear fiber to the readout system that is placed at the periphery of the detector. Due to space constraints, and in order to reduce costs, these 6000 cells are divided in groups using a MAPMT [Z. Ajaltouni, et al., Nucl. Instr. and Meth. A 504 (2003) 9] of 64 channels that provides information to the VFE readout electronics. The SPD signal has rather large statistical fluctuations because of the low number (20-30) of photoelectrons per MIP. Therefore the signal is integrated over the whole bunch crossing length of 25 ns in order to have the maximum value. Since in average about 85% of the SPD signal is within 25 ns, 15% of a sample is subtracted from the following one using an operational amplifier. The SPD VFE readout system that will be presented consists of the following components. A specific ASIC [D. Gascon, et al., Discriminator ASIC for the VFE SPD of the LHCb Calorimeter, LHCB Technical Note, LHCB 2004-xx] integrates the signal, makes the signal-tail subtraction, and compares the level obtained to a programmable threshold (to distinguish electrons from photons). A FPGA programmes the ASIC threshold and the value for

  16. On Front Slope Stability of Berm Breakwaters

    DEFF Research Database (Denmark)

    Burcharth, Hans F.

    2013-01-01

    The short communication presents application of the conventional Van der Meer stability formula for low-crested breakwaters for the prediction of front slope erosion of statically stable berm breakwaters with relatively high berms. The method is verified (Burcharth, 2008) by comparison...... with the reshaping of a large Norwegian breakwater exposed to the North Sea waves. As a motivation for applying the Van der Meer formula a discussion of design parameters related to berm breakwater stability formulae is given. Comparisons of front erosion predicted by the use of the Van der Meer formula with model...... test results including tests presented in Sigurdarson and Van der Meer (2011) are discussed. A proposal is presented for performance of new model tests with the purpose of developing more accurate formulae for the prediction of front slope erosion as a function of front slope, relative berm height...

  17. Life on the front lines.

    Science.gov (United States)

    Hern, W M

    1993-01-01

    honor those who advanced the cause of women's rights. They honored the physician who had to shout over hecklers to make his remarks heard. After a year of operation, the physician encountered differences with the Board of Directors of the clinic. Soon after that, he resigned and opened his own clinic with a bank loan of $7000. Within 4 years, his clinic had expanded, and he purchased its building. The harassment from antiabortion protesters continued, with broken windows, pickets, and, in February 1988, bullets fired through the front windows of the waiting room. This necessitated the installation of bullet-proof glass and a security system which cost $17,000. As of March 1, 1993, there had been 1285 acts of violence towards abortion clinics, which led to the destruction of more than 100. On March 10 of that year, a physician who performed abortions in Florida was gunned down by an anti-abortion protestor. People who provide abortions hope for legal protection and respect for their civil liberties, but they will continue to provide this service even if conditions do not improve.

  18. Volcanic Plume Measurements with UAV (Invited)

    Science.gov (United States)

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

    2013-12-01

    Volatiles in magmas are the driving force of volcanic eruptions and quantification of volcanic gas flux and composition is important for the volcano monitoring. Recently we developed a portable gas sensor system (Multi-GAS) to quantify the volcanic gas composition by measuring volcanic plumes and obtained volcanic gas compositions of actively degassing volcanoes. As the Multi-GAS measures variation of volcanic gas component concentrations in the pumped air (volcanic plume), we need to bring the apparatus into the volcanic plume. Commonly the observer brings the apparatus to the summit crater by himself but such measurements are not possible under conditions of high risk of volcanic eruption or difficulty to approach the summit due to topography etc. In order to overcome these difficulties, volcanic plume measurements were performed by using manned and unmanned aerial vehicles. The volcanic plume measurements by manned aerial vehicles, however, are also not possible under high risk of eruption. The strict regulation against the modification of the aircraft, such as installing sampling pipes, also causes difficulty due to the high cost. Application of the UAVs for the volcanic plume measurements has a big advantage to avoid these problems. The Multi-GAS consists of IR-CO2 and H2O gas analyzer, SO2-H2O chemical sensors and H2 semiconductor sensor and the total weight ranges 3-6 kg including batteries. The necessary conditions of the UAV for the volcanic plumes measurements with the Multi-GAS are the payloads larger than 3 kg, maximum altitude larger than the plume height and installation of the sampling pipe without contamination of the exhaust gases, as the exhaust gases contain high concentrations of H2, SO2 and CO2. Up to now, three different types of UAVs were applied for the measurements; Kite-plane (Sky Remote) at Miyakejima operated by JMA, Unmanned airplane (Air Photo Service) at Shinomoedake, Kirishima volcano, and Unmanned helicopter (Yamaha) at Sakurajima

  19. Beyond Colorado's Front Range - A new look at Laramide basin subsidence, sedimentation, and deformation in north-central Colorado

    Science.gov (United States)

    Cole, James C.; Trexler, James H.; Cashman, Patricia H.; Miller, Ian M.; Shroba, Ralph R.; Cosca, Michael A.; Workman, Jeremiah B.

    2010-01-01

    This field trip highlights recent research into the Laramide uplift, erosion, and sedimentation on the western side of the northern Colorado Front Range. The Laramide history of the North Park?Middle Park basin (designated the Colorado Headwaters Basin in this paper) is distinctly different from that of the Denver basin on the eastern flank of the range. The Denver basin stratigraphy records the transition from Late Cretaceous marine shale to recessional shoreline sandstones to continental, fluvial, marsh, and coal mires environments, followed by orogenic sediments that span the K-T boundary. Upper Cretaceous and Paleogene strata in the Denver basin consist of two mega-fan complexes that are separated by a 9 million-year interval of erosion/non-deposition between about 63 and 54 Ma. In contrast, the marine shale unit on the western flank of the Front Range was deeply eroded over most of the area of the Colorado Headwaters Basin (approximately one km removed) prior to any orogenic sediment accumulation. New 40Ar-39Ar ages indicate the oldest sediments on the western flank of the Front Range were as young as about 61 Ma. They comprise the Windy Gap Volcanic Member of the Middle Park Formation, which consists of coarse, immature volcanic conglomerates derived from nearby alkalic-mafic volcanic edifices that were forming at about 65?61 Ma. Clasts of Proterozoic granite, pegmatite, and gneiss (eroded from the uplifted core of the Front Range) seem to arrive in the Colorado Headwaters Basin at different times in different places, but they become dominant in arkosic sandstones and conglomerates about one km above the base of the Colorado Headwaters Basin section. Paleocurrent trends suggest the southern end of the Colorado Headwaters Basin was structurally closed because all fluvial deposits show a northward component of transport. Lacustrine depositional environments are indicated by various sedimentological features in several sections within the >3 km of sediment

  20. Volcanic Ash Advisory Database, 1983-2003

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Volcanic ash is a significant hazard to aviation and can also affect global climate patterns. To ensure safe navigation and monitor possible climatic impact, the...

  1. Age of the Auckland Volcanic Field

    International Nuclear Information System (INIS)

    Lindsay, J.; Leonard, G.S.

    2009-01-01

    In 2008 a multi-disciplinary research programme was launched, a GNS Science-University of Auckland collaboration with the aim of DEtermining VOlcanic Risk in Auckland (DEVORA). A major aspiration of DEVORA is development of a probabilistic hazard model for the Auckland Volcanic Field (AVF). This will be achieved by investigating past eruption magnitude-frequency relationships and comparing these with similar data from analogous volcanic fields. A key data set underpinning this is an age database for the AVF. To this end a comprehensive dating campaign is planned as part of DEVORA. This report, Age of the Auckland Volcanic Field, is a synthesis of all currently available age data for the AVF. It represents one of several reports carried out as part of the 'synthesis' phase of DEVORA, whereby existing data from all previous work is collated and summarised, so that gaps in current knowledge can be identified and addressed. (author). 60 refs., 7 figs., 31 tabs.

  2. Volcanic eruptions are cooling the earth

    International Nuclear Information System (INIS)

    Groenaas, Sigbjoern

    2005-01-01

    The article discusses how volcanic eruptions may influence the climate. The environmental impacts both on the earth surface and the atmosphere are surveyed. Some major eruptions in modern times are mentioned

  3. Stochastic Modeling of Past Volcanic Crises

    Science.gov (United States)

    Woo, Gordon

    2018-01-01

    The statistical foundation of disaster risk analysis is past experience. From a scientific perspective, history is just one realization of what might have happened, given the randomness and chaotic dynamics of Nature. Stochastic analysis of the past is an exploratory exercise in counterfactual history, considering alternative possible scenarios. In particular, the dynamic perturbations that might have transitioned a volcano from an unrest to an eruptive state need to be considered. The stochastic modeling of past volcanic crises leads to estimates of eruption probability that can illuminate historical volcanic crisis decisions. It can also inform future economic risk management decisions in regions where there has been some volcanic unrest, but no actual eruption for at least hundreds of years. Furthermore, the availability of a library of past eruption probabilities would provide benchmark support for estimates of eruption probability in future volcanic crises.

  4. Imaging volcanic CO2 and SO2

    Science.gov (United States)

    Gabrieli, A.; Wright, R.; Lucey, P. G.; Porter, J. N.

    2017-12-01

    Detecting and quantifying volcanic carbon dioxide (CO2) and sulfur dioxide (SO2) emissions is of relevance to volcanologists. Changes in the amount and composition of gases that volcanoes emit are related to subsurface magma movements and the probability of eruptions. Volcanic gases and related acidic aerosols are also an important atmospheric pollution source that create environmental health hazards for people, animals, plants, and infrastructures. For these reasons, it is important to measure emissions from volcanic plumes during both day and night. We present image measurements of the volcanic plume at Kīlauea volcano, HI, and flux derivation, using a newly developed 8-14 um hyperspectral imaging spectrometer, the Thermal Hyperspectral Imager (THI). THI is capable of acquiring images of the scene it views from which spectra can be derived from each pixel. Each spectrum contains 50 wavelength samples between 8 and 14 um where CO2 and SO2 volcanic gases have diagnostic absorption/emission features respectively at 8.6 and 14 um. Plume radiance measurements were carried out both during the day and the night by using both the lava lake in the Halema'uma'u crater as a hot source and the sky as a cold background to detect respectively the spectral signatures of volcanic CO2 and SO2 gases. CO2 and SO2 path-concentrations were then obtained from the spectral radiance measurements using a new Partial Least Squares Regression (PLSR)-based inversion algorithm, which was developed as part of this project. Volcanic emission fluxes were determined by combining the path measurements with wind observations, derived directly from the images. Several hours long time-series of volcanic emission fluxes will be presented and the SO2 conversion rates into aerosols will be discussed. The new imaging and inversion technique, discussed here, are novel allowing for continuous CO2 and SO2 plume mapping during both day and night.

  5. QCD and Light-Front Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Brodsky, Stanley J.; de Teramond, Guy F.; /SLAC /Southern Denmark U., CP3-Origins /Costa Rica U.

    2011-01-10

    AdS/QCD, the correspondence between theories in a dilaton-modified five-dimensional anti-de Sitter space and confining field theories in physical space-time, provides a remarkable semiclassical model for hadron physics. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The result is a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound state wavefunctions as a function of the invariant mass of the constituents. The hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. Higher Fock states with extra quark-anti quark pairs also arise. The soft-wall model also predicts the form of the nonperturbative effective coupling and its {beta}-function. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method to systematically include QCD interaction terms. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.

  6. QCD and Light-Front Dynamics

    International Nuclear Information System (INIS)

    Brodsky, Stanley J.; de Teramond, Guy F.

    2011-01-01

    AdS/QCD, the correspondence between theories in a dilaton-modified five-dimensional anti-de Sitter space and confining field theories in physical space-time, provides a remarkable semiclassical model for hadron physics. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The result is a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate ζ which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound state wavefunctions as a function of the invariant mass of the constituents. The hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. Higher Fock states with extra quark-anti quark pairs also arise. The soft-wall model also predicts the form of the nonperturbative effective coupling and its β-function. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method to systematically include QCD interaction terms. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.

  7. Pareto fronts in clinical practice for pinnacle.

    Science.gov (United States)

    Janssen, Tomas; van Kesteren, Zdenko; Franssen, Gijs; Damen, Eugène; van Vliet, Corine

    2013-03-01

    Our aim was to develop a framework to objectively perform treatment planning studies using Pareto fronts. The Pareto front represents all optimal possible tradeoffs among several conflicting criteria and is an ideal tool with which to study the possibilities of a given treatment technique. The framework should require minimal user interaction and should resemble and be applicable to daily clinical practice. To generate the Pareto fronts, we used the native scripting language of Pinnacle(3) (Philips Healthcare, Andover, MA). The framework generates thousands of plans automatically from which the Pareto front is generated. As an example, the framework is applied to compare intensity modulated radiation therapy (IMRT) with volumetric modulated arc therapy (VMAT) for prostate cancer patients. For each patient and each technique, 3000 plans are generated, resulting in a total of 60,000 plans. The comparison is based on 5-dimensional Pareto fronts. Generating 3000 plans for 10 patients in parallel requires on average 96 h for IMRT and 483 hours for VMAT. Using VMAT, compared to IMRT, the maximum dose of the boost PTV was reduced by 0.4 Gy (P=.074), the mean dose in the anal sphincter by 1.6 Gy (P=.055), the conformity index of the 95% isodose (CI(95%)) by 0.02 (P=.005), and the rectal wall V(65 Gy) by 1.1% (P=.008). We showed the feasibility of automatically generating Pareto fronts with Pinnacle(3). Pareto fronts provide a valuable tool for performing objective comparative treatment planning studies. We compared VMAT with IMRT in prostate patients and found VMAT had a dosimetric advantage over IMRT. Copyright © 2013 Elsevier Inc. All rights reserved.

  8. Pareto Fronts in Clinical Practice for Pinnacle

    International Nuclear Information System (INIS)

    Janssen, Tomas; Kesteren, Zdenko van; Franssen, Gijs; Damen, Eugène; Vliet, Corine van

    2013-01-01

    Purpose: Our aim was to develop a framework to objectively perform treatment planning studies using Pareto fronts. The Pareto front represents all optimal possible tradeoffs among several conflicting criteria and is an ideal tool with which to study the possibilities of a given treatment technique. The framework should require minimal user interaction and should resemble and be applicable to daily clinical practice. Methods and Materials: To generate the Pareto fronts, we used the native scripting language of Pinnacle 3 (Philips Healthcare, Andover, MA). The framework generates thousands of plans automatically from which the Pareto front is generated. As an example, the framework is applied to compare intensity modulated radiation therapy (IMRT) with volumetric modulated arc therapy (VMAT) for prostate cancer patients. For each patient and each technique, 3000 plans are generated, resulting in a total of 60,000 plans. The comparison is based on 5-dimensional Pareto fronts. Results: Generating 3000 plans for 10 patients in parallel requires on average 96 h for IMRT and 483 hours for VMAT. Using VMAT, compared to IMRT, the maximum dose of the boost PTV was reduced by 0.4 Gy (P=.074), the mean dose in the anal sphincter by 1.6 Gy (P=.055), the conformity index of the 95% isodose (CI 95% ) by 0.02 (P=.005), and the rectal wall V 65 Gy by 1.1% (P=.008). Conclusions: We showed the feasibility of automatically generating Pareto fronts with Pinnacle 3 . Pareto fronts provide a valuable tool for performing objective comparative treatment planning studies. We compared VMAT with IMRT in prostate patients and found VMAT had a dosimetric advantage over IMRT

  9. Local and remote infrasound from explosive volcanism

    Science.gov (United States)

    Matoza, R. S.; Fee, D.; LE Pichon, A.

    2014-12-01

    Explosive volcanic eruptions can inject large volumes of ash into heavily travelled air corridors and thus pose a significant societal and economic hazard. In remote volcanic regions, satellite data are sometimes the only technology available to observe volcanic eruptions and constrain ash-release parameters for aviation safety. Infrasound (acoustic waves ~0.01-20 Hz) data fill this critical observational gap, providing ground-based data for remote volcanic eruptions. Explosive volcanic eruptions are among the most powerful sources of infrasound observed on earth, with recordings routinely made at ranges of hundreds to thousands of kilometers. Advances in infrasound technology and the efficient propagation of infrasound in the atmosphere therefore greatly enhance our ability to monitor volcanoes in remote regions such as the North Pacific Ocean. Infrasound data can be exploited to detect, locate, and provide detailed chronologies of the timing of explosive volcanic eruptions for use in ash transport and dispersal models. We highlight results from case studies of multiple eruptions recorded by the International Monitoring System and dedicated regional infrasound networks (2008 Kasatochi, Alaska, USA; 2008 Okmok, Alaska, USA; 2009 Sarychev Peak, Kuriles, Russian Federation; 2010 Eyjafjallajökull, Icleand) and show how infrasound is currently used in volcano monitoring. We also present progress towards characterizing and modeling the variability in source mechanisms of infrasound from explosive eruptions using dedicated local infrasound field deployments at volcanoes Karymsky, Russian Federation and Sakurajima, Japan.

  10. Light-Front Holography and the Light-Front Schrodinger Equation

    Energy Technology Data Exchange (ETDEWEB)

    Brodsky, Stanley J.; de Teramond, Guy

    2012-08-15

    One of the most important nonperturbative methods for solving QCD is quantization at fixed light-front time {tau} = t+z=c - Dirac's 'Front Form'. The eigenvalues of the light-front QCD Hamiltonian predict the hadron spectrum and the eigensolutions provide the light-front wavefunctions which describe hadron structure. More generally, we show that the valence Fock-state wavefunctions of the light-front QCD Hamiltonian satisfy a single-variable relativistic equation of motion, analogous to the nonrelativistic radial Schrodinger equation, with an effective confining potential U which systematically incorporates the effects of higher quark and gluon Fock states. We outline a method for computing the required potential from first principles in QCD. The holographic mapping of gravity in AdS space to QCD, quantized at fixed light-front time, yields the same light front Schrodinger equation; in fact, the soft-wall AdS/QCD approach provides a model for the light-front potential which is color-confining and reproduces well the light-hadron spectrum. One also derives via light-front holography a precise relation between the bound-state amplitudes in the fifth dimension of AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. The elastic and transition form factors of the pion and the nucleons are found to be well described in this framework. The light-front AdS/QCD holographic approach thus gives a frame-independent first approximation of the color-confining dynamics, spectroscopy, and excitation spectra of relativistic light-quark bound states in QCD.

  11. Light-Front Quantization of Gauge Theories

    Energy Technology Data Exchange (ETDEWEB)

    Brodsky, Stanley J.

    2003-03-25

    Light-front wavefunctions provide a frame-independent representation of hadrons in terms of their physical quark and gluon degrees of freedom. The light-front Hamiltonian formalism provides new nonperturbative methods for obtaining the QCD spectrum and eigensolutions, including resolvant methods, variational techniques, and discretized light-front quantization. A new method for quantizing gauge theories in light-cone gauge using Dirac brackets to implement constraints is presented. In the case of the electroweak theory, this method of light-front quantization leads to a unitary and renormalizable theory of massive gauge particles, automatically incorporating the Lorentz and 't Hooft conditions as well as the Goldstone boson equivalence theorem. Spontaneous symmetry breaking is represented by the appearance of zero modes of the Higgs field leaving the light-front vacuum equal to the perturbative vacuum. I also discuss an ''event amplitude generator'' for automatically computing renormalized amplitudes in perturbation theory. The importance of final-state interactions for the interpretation of diffraction, shadowing, and single-spin asymmetries in inclusive reactions such as deep inelastic lepton-hadron scattering is emphasized.

  12. Light-Front Quantization of Gauge Theories

    Energy Technology Data Exchange (ETDEWEB)

    Brodskey, Stanley

    2002-12-01

    Light-front wavefunctions provide a frame-independent representation of hadrons in terms of their physical quark and gluon degrees of freedom. The light-front Hamiltonian formalism provides new nonperturbative methods for obtaining the QCD spectrum and eigensolutions, including resolvant methods, variational techniques, and discretized light-front quantization. A new method for quantizing gauge theories in light-cone gauge using Dirac brackets to implement constraints is presented. In the case of the electroweak theory, this method of light-front quantization leads to a unitary and renormalizable theory of massive gauge particles, automatically incorporating the Lorentz and 't Hooft conditions as well as the Goldstone boson equivalence theorem. Spontaneous symmetry breaking is represented by the appearance of zero modes of the Higgs field leaving the light-front vacuum equal to the perturbative vacuum. I also discuss an ''event amplitude generator'' for automatically computing renormalized amplitudes in perturbation theory. The importance of final-state interactions for the interpretation of diffraction, shadowing, and single-spin asymmetries in inclusive reactions such as deep inelastic lepton-hadron scattering is emphasized.

  13. Statistical Physics and Light-Front Quantization

    Energy Technology Data Exchange (ETDEWEB)

    Raufeisen, J

    2004-08-12

    Light-front quantization has important advantages for describing relativistic statistical systems, particularly systems for which boost invariance is essential, such as the fireball created in a heavy ion collisions. In this paper the authors develop light-front field theory at finite temperature and density with special attention to quantum chromodynamics. They construct the most general form of the statistical operator allowed by the Poincare algebra and show that there are no zero-mode related problems when describing phase transitions. They then demonstrate a direct connection between densities in light-front thermal field theory and the parton distributions measured in hard scattering experiments. The approach thus generalizes the concept of a parton distribution to finite temperature. In light-front quantization, the gauge-invariant Green's functions of a quark in a medium can be defined in terms of just 2-component spinors and have a much simpler spinor structure than the equal-time fermion propagator. From the Green's function, the authors introduce the new concept of a light-front density matrix, whose matrix elements are related to forward and to off-diagonal parton distributions. Furthermore, they explain how thermodynamic quantities can be calculated in discretized light-cone quantization, which is applicable at high chemical potential and is not plagued by the fermion-doubling problems.

  14. Sharp fronts within geochemical transport problems

    International Nuclear Information System (INIS)

    Grindrod, P.

    1995-01-01

    The authors consider some reactive geochemical transport problems in groundwater systems. When incoming fluid is in disequilibrium with the mineralogy sharp transition fronts may develop. They show that this is a generic property for a class of systems where the timescales associated with reaction and diffusion phenomena are much shorter than those associated with advective transport. Such multiple timescale problems are relevant to a variety of processes in natural systems: mathematically methods of singular perturbation theory reduce the dimension of the problems to be solved locally. Furthermore, they consider how spatial heterogeneous mineralogy can impact upon the propagation of sharp geochemical fronts. The authors developed an asymptotic approach in which they solve equations for the evolving geometry of the front and indicate how the non-smooth perturbations due to natural heterogeneity of the mineralogy on underlying ground water flow field are balanced against the smoothing effect of diffusion/dispersive processes. Fronts are curvature damped, and the results here indicate the generic nature of separate front propagation within both model (idealized) and natural (heterogeneous) geochemical systems

  15. The Origin of Widespread Long-lived Volcanism Across the Galapagos Volcanic Province

    Science.gov (United States)

    O'Connor, J. M.; Stoffers, P.; Wijbrans, J. R.; Worthington, T. J.

    2005-12-01

    40Ar/39Ar ages for rocks dredged (SO144 PAGANINI expedition) and drilled (DSDP) from the Galapagos Volcanic Province (Cocos, Carnegie, Coiba and Malpelo aseismic ridges and associated seamounts) show evidence of 1) increasing age with distance from the Galapagos Archipelago, 2) long-lived episodic volcanism at many locations, and 3) broad overlapping regions of coeval volcanism. The widespread nature of synchronous volcanism across the Galapagos Volcanic Province (GVP) suggests a correspondingly large Galapagos hotspot melting anomaly (O'Connor et al., 2004). Development of the GVP via Cocos and Nazca plate migration and divergence over this broad melting anomaly would explain continued multiple phases of volcanism over millions of years following the initial onset of hotspot volcanism. The question arising from these observations is whether long-lived GVP episodic volcanism is equivalent to `rejuvenescent' or a `post-erosional' phase of volcanism that occurs hundreds of thousands or million years after the main shield-building phase documented on many mid-plate seamount chains, most notably along the Hawaiian-Emperor Seamount Chain? Thus, investigating the process responsible for long-lived episodic GVP volcanism provides the opportunity to evaluate this little understood process of rejuvenation in a physical setting very different to the Hawaiian-Emperor Chain (i.e. on/near spreading axis versus mid-plate). We consider here timing and geochemical information to test the various geodynamic models proposed to explain the origin of GVP hotspot volcanism, especially the possibility of rejuvenated phases that erupt long after initial shield-building.

  16. Systematic front distortion and presence of consecutive fronts in a precipitation system

    NARCIS (Netherlands)

    Volford, A.; Izsak, F.; Ripszam, M.; Lagzi, I.

    2006-01-01

    A new simple reaction-diffusion system is presented focusing on pattern formation phenomena as consecutive precipitation fronts and distortion of the precipitation front.The chemical system investigated here is based on the amphoteric property of aluminum hydroxide and exhibits two unique phenomena.

  17. Behavior of fragmentation front in a porous viscoelastic material

    Science.gov (United States)

    Ichihara, M.; Takayama, K.

    2002-12-01

    We are developing laboratory experiments to investigate dynamics of magma fragmentation during explosive volcanic eruptions. Fragmentation of such a mixture as magma consisting of viscoelastic melt, bubbles and solid particles, is not known yet, and experiments are necessary to establish a mathematical model. It has been shown that viscoelastic silicone compound (Dow Corning 3179) is a useful analogous material to simulate magma fragmentation. In the previous work, a porous specimen made of the compound was rapidly decompressed and development of brittle fragmentation was observed. However, there were arguments that the experiment was different from actual processes which produce fragments as small as volcanic ash, because in the experiment the specimen was broken into only several pieces. This time, results of the improved experiments are presented. The experimental apparatus is a kind of a vertical shock tube, which mainly consists of a high pressure test section and low pressure chambers. The test section is made of acrylic tube of which inner diameter is 25 mm. The internal phenomenon is recorded by a high-speed video camera. Pressure is measured in the gas above and beneath the specimen by piezoelectric transducers. The specimen is prepared in the following way. First, an acrylic tube filled with the compound is put in a nitrogen tank and kept at 45 bar for more than 8 hours. The compound absorbs the gas and equilibrates with the nitrogen. Next, the tank is decompressed back to the atmospheric pressure slowly. Nitrogen exsolves and bubbles are formed in the compound quite uniformly. Finally, the expanded compound sticking out of both ends of the tube is cut down, and the tube containing the specimen is attached to the shock tube. The specimen is rapidly decompressed by 24, 16, and 8 bars. The high-speed video images demonstrate a sequence of the fragmentation process. We observe propagation of a clear fracture front at 50 m/s for 24 bar of decompression and at

  18. Volcanism on differentiated asteroids (Invited)

    Science.gov (United States)

    Wilson, L.

    2013-12-01

    after passing through optically dense fire fountains. At low eruption rates and high volatile contents many clasts cooled to form spatter or cinder deposits, but at high eruption rates and low volatile contents most clasts landed hot and coalesced into lava ponds to feed lava flows. Lava flow thickness varies with surface slope, acceleration due to gravity, and lava yield strength induced by cooling. Low gravity on asteroids caused flows to be relatively thick which reduced the effects of cooling, and many flows probably attained lengths of tens of km and stopped as a result of cessation of magma supply from the reservoir rather than cooling. On most asteroids larger than 100 km radius experiencing more than ~30% mantle melting, the erupted volcanic deposits will have buried the original chondritic surface layers of the asteroid to such great depths that they were melted, or at least heavily thermally metamorphosed, leaving no present-day meteoritical evidence of their prior existence. Tidal stresses from close encounters between asteroids and proto-planets may have very briefly increased melting and melt migration speeds in asteroid interiors but only gross structural disruption would have greatly have changed volcanic histories.

  19. Optimal back-to-front airplane boarding

    Science.gov (United States)

    Bachmat, Eitan; Khachaturov, Vassilii; Kuperman, Ran

    2013-06-01

    The problem of finding an optimal back-to-front airplane boarding policy is explored, using a mathematical model that is related to the 1+1 polynuclear growth model with concave boundary conditions and to causal sets in gravity. We study all airplane configurations and boarding group sizes. Optimal boarding policies for various airplane configurations are presented. Detailed calculations are provided along with simulations that support the main conclusions of the theory. We show that the effectiveness of back-to-front policies undergoes a phase transition when passing from lightly congested airplanes to heavily congested airplanes. The phase transition also affects the nature of the optimal or near-optimal policies. Under what we consider to be realistic conditions, optimal back-to-front policies lead to a modest 8-12% improvement in boarding time over random (no policy) boarding, using two boarding groups. Having more than two groups is not effective.

  20. Friction forces on phase transition fronts

    International Nuclear Information System (INIS)

    Mégevand, Ariel

    2013-01-01

    In cosmological first-order phase transitions, the microscopic interaction of the phase transition fronts with non-equilibrium plasma particles manifests itself macroscopically as friction forces. In general, it is a nontrivial problem to compute these forces, and only two limits have been studied, namely, that of very slow walls and, more recently, ultra-relativistic walls which run away. In this paper we consider ultra-relativistic velocities and show that stationary solutions still exist when the parameters allow the existence of runaway walls. Hence, we discuss the necessary and sufficient conditions for the fronts to actually run away. We also propose a phenomenological model for the friction, which interpolates between the non-relativistic and ultra-relativistic values. Thus, the friction depends on two friction coefficients which can be calculated for specific models. We then study the velocity of phase transition fronts as a function of the friction parameters, the thermodynamic parameters, and the amount of supercooling

  1. Optimal back-to-front airplane boarding.

    Science.gov (United States)

    Bachmat, Eitan; Khachaturov, Vassilii; Kuperman, Ran

    2013-06-01

    The problem of finding an optimal back-to-front airplane boarding policy is explored, using a mathematical model that is related to the 1+1 polynuclear growth model with concave boundary conditions and to causal sets in gravity. We study all airplane configurations and boarding group sizes. Optimal boarding policies for various airplane configurations are presented. Detailed calculations are provided along with simulations that support the main conclusions of the theory. We show that the effectiveness of back-to-front policies undergoes a phase transition when passing from lightly congested airplanes to heavily congested airplanes. The phase transition also affects the nature of the optimal or near-optimal policies. Under what we consider to be realistic conditions, optimal back-to-front policies lead to a modest 8-12% improvement in boarding time over random (no policy) boarding, using two boarding groups. Having more than two groups is not effective.

  2. Design and construction of a testbed for the application of real volcanic ash from the Eyjafjallajökull and Grimsvötn eruptions to microgas turbines

    Science.gov (United States)

    Weber, Konradin; Fischer, Christian; Lange, Martin; Schulz, Uwe; Naraparaju, Ravisankar; Kramer, Dietmar

    2017-04-01

    It is well known that volcanic ash clouds emitted from erupting volcanoes pose a considerable threat to the aviation. The volcanic ash particles can damage the turbine blades and their thermal barrier coatings as well as the bearings of the turbine. For a detailed investigation of this damaging effect a testbed was designed and constructed, which allowed to study the damaging effects of real volcanic ash to an especially for these investigations modified microgas turbine. The use of this microgas turbine had the advantage that it delivers near reality conditions, using kerosene and operating at similar temperatures as big turbines, but at a very cost effective level. The testbed consisted out of a disperser for the real volcanic ash and all the equipment needed to control the micro gas turbine. Moreover, in front and behind the microgas turbine the concentration and the distribution of the volcanic ash were measured online by optical particle counters (OPCs). The particle concentration and size distribution of the volcanic ash particles in the intake in front of the microgas turbine was measured by an optical particle counter (OPC) combined with an isokinetic intake. Behind the microgas turbine in the exhaust gas additionally to the measurement with a second OPC ash particles were caught with an impactor, in order to enable the later analysis with an electron microscope concerning the morphology to verify possible melting processes of the ash particles. This testbed is of high importance as it allows detailed investigations of the impact of volcanic ash to jet turbines and appropriate countermeasures.

  3. PIV tracer behavior on propagating shock fronts

    International Nuclear Information System (INIS)

    Glazyrin, Fyodor N; Mursenkova, Irina V; Znamenskaya, Irina A

    2016-01-01

    The present work was aimed at the quantitative particle image velocimetry (PIV) measurement of a velocity field near the front of a propagating shock wave and the study of the dynamics of liquid tracers crossing the shock front. For this goal, a shock tube with a rectangular cross-section (48  ×  24 mm) was used. The flat shock wave with Mach numbers M  =  1.4–2.0 propagating inside the tube channel was studied as well as an expanding shock wave propagating outside the channel with M  =  1.2–1.8 at its main axis. The PIV imaging of the shock fronts was carried out with an aerosol of dioctyl sebacate (DEHS) as tracer particles. The pressures of the gas in front of the shock waves studied ranged from 0.013 Mpa to 0.1 MPa in the series of experiments. The processed PIV data, compared to the 1D normal shock theory, yielded consistent values of wake velocity immediately behind the plain shock wave. Special attention was paid to the blurring of the velocity jump on the shock front due to the inertial particle lag and peculiarities of the PIV technique. A numerical algorithm was developed for analysis and correction of the PIV data on the shock fronts, based on equations of particle-flow interaction. By application of this algorithm, the effective particle diameter of the DEHS aerosol tracers was estimated as 1.03  ±  0.12 μm. A number of different formulations for particle drag were tested with this algorithm, with varying success. The results show consistency with previously reported experimental data obtained for cases of stationary shock waves. (paper)

  4. 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

  5. RF front-end world class designs

    CERN Document Server

    Love, Janine

    2009-01-01

    All the design and development inspiration and direction a harware engineer needs in one blockbuster book! Janine Love site editor for RF Design Line,columnist, and author has selected the very best RF design material from the Newnes portfolio and has compiled it into this volume. The result is a book covering the gamut of RF front end design from antenna and filter design fundamentals to optimized layout techniques with a strong pragmatic emphasis. In addition to specific design techniques and practices, this book also discusses various approaches to solving RF front end design problems and h

  6. THREE PERSPECTIVES ON MANAGING FRONT END INNOVATION

    DEFF Research Database (Denmark)

    Jensen, Anna Rose Vagn; Clausen, Christian; Gish, Liv

    2018-01-01

    as a complementary perspective. The paper combines a literature review with an empirical examination of the application of these multiple perspectives across three cases of front end of innovation (FEI) management in mature product developing companies. While the process models represent the dominant, albeit rather...... to represent an emergent approach in managing FEI where process models, knowledge strategies and objects become integrated elements in more advanced navigational strategies for key players.......This paper presents three complementary perspectives on the management of front end innovation: A process model perspective, a knowledge perspective and a translational perspective. While the first two perspectives are well established in literature, we offer the translation perspective...

  7. TopN-Pareto Front Search

    Energy Technology Data Exchange (ETDEWEB)

    2016-12-21

    The JMP Add-In TopN-PFS provides an automated tool for finding layered Pareto front to identify the top N solutions from an enumerated list of candidates subject to optimizing multiple criteria. The approach constructs the N layers of Pareto fronts, and then provides a suite of graphical tools to explore the alternatives based on different prioritizations of the criteria. The tool is designed to provide a set of alternatives from which the decision-maker can select the best option for their study goals.

  8. Discretionary Power on the Front-line

    DEFF Research Database (Denmark)

    Sanden, Guro Refsum; Lønsmann, Dorte

    This article investigates the communication practices used by front-line employees to cross language boundaries in the context of English language policies implemented by the management of three multinational corporations (MNCs) headquartered in Scandinavia. Based on an analysis of interview...... and document data, our findings show that employees face a number of different language boundaries in their everyday work, and that ad hoc and informal solutions in many cases are vital for successful cross-language communication. We introduce the concept of ‘discretionary power’ to explain how and why front...

  9. Coping on the Front-line

    DEFF Research Database (Denmark)

    Sanden, Guro Refsum; Lønsmann, Dorte

    language boundaries in their everyday work. Despite official English language policies in the three companies, our findings show that employees face a number of different language boundaries, and that ad hoc and informal solutions in many cases are vital for successful cross-language communication. Drawing......This article investigates how front-line employees respond to English language policies implemented by the management of three multinational corporations (MNCs) headquartered in Scandinavia. Based on interview and document data the article examines the ways in which front-line employees cross...

  10. Discretionary power on the front-line

    DEFF Research Database (Denmark)

    Sanden, Guro Refsum; Lønsmann, Dorte

    2018-01-01

    This article investigates the communication practices used by front-line employees to cross language boundaries in the context of English language policies implemented by the management of three multinational corporations headquartered in Scandinavia. Based on an analysis of interview and document...... data, our findings show that employees face a number of different language boundaries in their everyday work, and that ad hoc and informal solutions in many cases are vital for successful cross-language communication. We introduce the concept of discretionary power to explain how and why front...

  11. Discretionary Power on the Front Line

    DEFF Research Database (Denmark)

    Sanden, Guro Refsum; Lønsmann, Dorte

    2018-01-01

    This paper investigates the communication practices used by front-line employees to cross language boundaries in the context of English language policies implemented by the management of three multinational corporations (MNCs) headquartered in Scandinavia. Based on an analysis of interview...... and document data, our findings show that employees face a number of different language boundaries in their everyday work, and that ad hoc and informal solutions in many cases are vital for successful cross-language communication. We introduce the concept of 'discretionary power' to explain how and why front...

  12. Pole solutions for flame front propagation

    CERN Document Server

    Kupervasser, Oleg

    2015-01-01

    This book deals with solving mathematically the unsteady flame propagation equations. New original mathematical methods for solving complex non-linear equations and investigating their properties are presented. Pole solutions for flame front propagation are developed. Premixed flames and filtration combustion have remarkable properties: the complex nonlinear integro-differential equations for these problems have exact analytical solutions described by the motion of poles in a complex plane. Instead of complex equations, a finite set of ordinary differential equations is applied. These solutions help to investigate analytically and numerically properties of the flame front propagation equations.

  13. Light-front nuclear shell-model

    International Nuclear Information System (INIS)

    Johnson, M.B.

    1990-01-01

    I examine the effects of nuclear structure on high-energy, high-momentum transfer processes, specifically the EMC effect. For pedagogical reasons, a fictitious but simple two-body system consisting of two equal-mass particles interacting in a harmonic oscillator potential has been chosen. For this toy nucleus, I utilize a widely-used link between instant-form and light-front dynamics, formulating nuclear structure and deep-inelastic scattering consistently in the laboratory system. Binding effects are compared within conventional instant-form and light-front dynamical frameworks, with appreciable differences being found in the two cases. 20 refs

  14. Aeromagnetic Study of the Nortern Acambay Graben and Amealco Caldera, Central Mexican Volcanic Belt

    Science.gov (United States)

    Gonzalez, T.

    2011-12-01

    The Mexican Volcanic Belt (MVB) is characterized by E-W striking faults which form a series of en echelon graben along its length. In the central region of the MVB is located the Acambay graben an intra-arc tectonic depression structure, of apparent Quaternary age, which gives rise to pronounced scarps over a distance of about 80 Km. and 15 to 35 Km wide. The general arrangement of the faults that constitute the Acambay graben shows E-W trend which defines the fronts of the graben exhibits a major fault discontinuity. The graben is limited of the north by the Acambay- Tixmadeje and Epitafio Huerta faults and in the south by the Pastores and Venta de Bravo faults.. In the northern wall in the graben is located the Amealco caldera. This volcanic center (approximately 10 km in diameter) was formed by several discrete volcanic events, which produced an ignimbrite which covers the area. It is partially cut by a regional fault and the southern portion of the Amealco Caldera was displaced by a normal faulting along a segment of the Epitafio Huerta system. Continued tectonic activity in the Acambay area is confirmed by recent seismic episodes The Amealco tuff is the most important volcanic unit because of its volume and distribution. Aeromagnetic data was obtained and analyzed the anomalies. The anomaly map was compared with the surface geology and larger anomalies were correlated with major volcanic features. Since our main interest was in mapping the subsurface intrusive and volcanic bodies, the total field magnetic anomalies were reduced to the pole by using the double integral Fourier method. The reduced to the pole anomaly map results in a simplified pattern of isolated positive and negative anomalies, which show an improved correlation with all major volcanic structures. For the analysis and interpretation of the anomalies, the reduced to the pole anomalies were continued upward at various reference levels. These operations result in smoothing of the anomaly field by

  15. 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

  16. Indirect Climatic Effects of Major Volcanic Eruptions

    Science.gov (United States)

    Hofmann, D. J.

    2007-05-01

    The direct effects on climate, related to atmospheric emissions to the atmosphere following major volcanic eruptions, are well-known although the sparseness of such eruptions make detailed study on the range of such variations difficult. In general terms, infrared absorption by volcanic emissions to the stratosphere result in local heating early in the event when gaseous sulfur compounds exist. This early period is followed by gas to particle conversion, on a time scale of 1-2 months, promoting the formation of sulfuric acid-water droplets. Coagulation and droplet growth result in the "volcanic stratospheric aerosol layer" which is related to the predominant direct climatic effect of large eruptions, the cooling of the troposphere by backscattering of solar visible radiation to space with a recovery time scale of 1-2 years. In this paper we will discuss some of the less-known "indirect" effects of the volcanic stratospheric aerosol on climate. We label them indirect as they act on climate through intermediary atmospheric constituents. The intermediaries in the volcanic indirect climatic effect are generally atmospheric greenhouse gases or other atmospheric gases and conditions which affect greenhouse gases. For example, cooling of the troposphere following major eruptions reduces the growth rate of atmospheric carbon dioxide related to respiration by the terrestrial biosphere. In addition, redirection of part of the direct solar beam into diffuse radiation by the volcanic stratospheric aerosol stimulates plant photosynthesis, further reducing the carbon dioxide growth rate. The growth rate of the second-most important atmospheric greenhouse gas, methane, is also affected by volcanic emissions. Volcanic stratospheric aerosol particles provide surface area which catalyzes heterogeneous chemical reactions thus stimulating removal of stratospheric ozone, also a greenhouse gas. Although major droughts usually related to ENSO events have opposite effects on carbon

  17. Ages of plains volcanism on Mars

    Science.gov (United States)

    Hauber, Ernst; Jagert, Felix; Broz, Petr

    2010-05-01

    Plain-style volcanism [1] is widespread in the Tharsis and Elysium volcanic provinces on Mars, [2,3]. Detailed images and topographic data reveal the morphology and topography of clusters of low shields and associated lava flows. The landforms of plains volcanism on Mars have all well-known terrestrial analogues in basaltic volcanic regions, such as Hawaii, Iceland, and in particular the Snake River Plains [4]. The very gentle flank slopes (J. (1981) Icarus, 45, 586-601. [3] Hodges C.A. and Moore H.J. (1994) Atlas of volcanic features on Mars: USGS Prof. Paper 1534, 194 p. [4] Hauber E. et al. (2009) J. Volcanol. Geotherm. Res. 185, 69-95. [5] Wilson L. et al. (2009) J. Volcanol. Geotherm. Res. 185, 28-46. [6] Vaucher, J. et al. (2009) Icarus 204, 418-442. [7] Baratoux D. et al. (2009) J. Volcanol. Geotherm. Res. 185, 47-68. [8] Bleacher J.E. et al. (2009) J. Volcanol. Geotherm. Res. 185, 96-102. [9] Ivanov B.A. (2001) Space Sci. Rev. 96, 87-104. [10] Hartmann W.H. and Neukum G. (2001) Space Sci. Rev. 96, 165-194 [11] Kneissl T. et al. (2010) LPS XVI, submitted. [12] Michael, G.G. and Neukum G. (2010) Earth Planet. Sci. Lett., in press. . [13] Malin M.C. et al. (2007) JGR 112, E05S04, doi: 10.1029/2006JE002808.

  18. Evidence of volcanic and glacial activity in Chryse and Acidalia Planitiae, Mars

    Science.gov (United States)

    Martinez-Alonso, Sara; Mellon, Michael T.; Banks, Maria E.; Keszthelyi, Laszlo P.; McEwen, Alfred S.

    2011-01-01

    Chryse and Acidalia Planitiae show numerous examples of enigmatic landforms previously interpreted to have been influenced by a water/ice-rich geologic history. These landforms include giant polygons bounded by kilometer-scale arcuate troughs, bright pitted mounds, and mesa-like features. To investigate the significance of the last we have analyzed in detail the region between 60°N, 290°E and 10°N, 360°E utilizing HiRISE (High Resolution Imaging Science Experiment) images as well as regional-scale data for context. The mesas may be analogous to terrestrial tuyas (emergent sub-ice volcanoes), although definitive proof has not been identified. We also report on a blocky unit and associated landforms (drumlins, eskers, inverted valleys, kettle holes) consistent with ice-emplaced volcanic or volcano-sedimentary flows. The spatial association between tuya-like mesas, ice-emplaced flows, and further possible evidence of volcanism (deflated flow fronts, volcanic vents, columnar jointing, rootless cones), and an extensive fluid-rich substratum (giant polygons, bright mounds, rampart craters), allows for the possibility of glaciovolcanic activity in the region.Landforms indicative of glacial activity on Chryse/Acidalia suggest a paleoclimatic environment remarkably different from today's. Climate changes on Mars (driven by orbital/obliquity changes) or giant outflow channel activity could have resulted in ice-sheet-related landforms far from the current polar caps.

  19. Oxygen Isotopes in Intra-Back Arc Basalts from the Andean Southern Volcanic Zone

    Science.gov (United States)

    Parks, B. H.; Wang, Z.; Saal, A. E.; Frey, F. A.; Blusztajn, J.

    2013-12-01

    The chemical compositions of volcanic rocks from the Andean Southern Volcanic Zone (SVZ) reflect complex and dynamic interactions among the subducting oceanic lithosphere, the mantle wedge, and the overlying continental crust. Oxygen isotope ratios of olivine phenocrysts can be a useful means to identifying their relative contributions to the arc magmatism. In this study, we report high-precision oxygen-isotope ratios of olivine phenocrysts in a set of intra-back arc basalts from the SVZ. The samples were collected from monogenetic cinder cones east of the volcanic front (35-39 degrees S), and have been geochemically well-characterized with major and trace element contents, and Sr-Nd-Pb isotope compositions. Compared to lavas from the volcanic front, these intra-back arc lavas have similar radiogenic isotope, and a more alkalic and primitive (higher MgO content) chemical composition. We determined the oxygen-isotope ratios using the CO2-laser-fluorination method set up at the Department of Geology and Geophysics, Yale University following the techniques reported in Wang et al (2011). The samples were analyzed with standards of Gore Mountain Garnet (5.77×0.12‰ 1σ; Valley et al., 1995) and Kilbourne Hole Olivine (5.23×0.07‰ 1σ; Sharp, 1990) in order to account for minor changes in the vacuum line during analyses. The obtained δ18OSMOW values of olivine phenocrysts from the intra-back arc basalts vary from 4.98×0.01 to 5.34×0.01‰. This range, surprisingly, is similar to the δ18O values of olivines from mantle peridotites (5.2×0.2‰). Preliminary results indicate significant correlations of 87Sr/86Sr, 143Nd/144Nd and trace element ratios of the basaltic matrix with the δ18O values of olivine phenocrysts, indicating at least three components involved in the formation of the arc volcanism. By comparing the δ18O with the variations of major and trace element contents (e.g., MgO, TiO2 and Ni), and trace element ratios (e.g. Ba/Nb), we evaluate the effects

  20. Active Volcanic Eruptions on Io

    Science.gov (United States)

    1996-01-01

    Six views of the volcanic plume named Prometheus, as seen against Io's disk and near the bright limb (edge) of the satellite by the SSI camera on the Galileo spacecraft during its second (G2) orbit of Jupiter. North is to the top of each frame. To the south-southeast of Prometheus is another bright spot that appears to be an active plume erupting from a feature named Culann Patera. Prometheus was active 17 years ago during both Voyager flybys, but no activity was detected by Voyager at Culann. Both of these plumes were seen to glow in the dark in an eclipse image acquired by the imaging camera during Galileo's first (G1) orbit, and hot spots at these locations were detected by Galileo's Near-Infrared Mapping Spectrometer.The plumes are thought to be driven by heating sulfur dioxide in Io's subsurface into an expanding fluid or 'geyser'. The long-lived nature of these eruptions requires that a substantial supply of sulfur dioxide must be available in Io's subsurface, similar to groundwater. Sulfur dioxide gas condenses into small particles of 'snow' in the expanding plume, and the small particles scatter light and appear bright at short wavelengths. The images shown here were acquired through the shortest-wavelength filter (violet) of the Galileo camera. Prometheus is about 300 km wide and 75 km high and Culann is about 150 km wide and less than 50 km high. The images were acquired on September 4, 1996 at a range of 2,000,000 km (20 km/pixel resolution). Prometheus is named after the Greek fire god and Culann is named after the Celtic smith god.The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can

  1. Light-Front Dynamics in Hadron Physics

    NARCIS (Netherlands)

    Ji, C.R.; Bakker, B.L.G.; Choi, H.M.

    2013-01-01

    Light-front dynamics(LFD) plays an important role in the analyses of relativistic few-body systems. As evidenced from the recent studies of generalized parton distributions (GPDs) in hadron physics, a natural framework for a detailed study of hadron structures is LFD due to its direct application in

  2. Positional Velar Fronting: An Updated Articulatory Account

    Science.gov (United States)

    Byun, Tara McAllister

    2012-01-01

    This study develops the hypothesis that the child-specific phenomenon of positional velar fronting can be modeled as the product of phonologically encoded articulatory limitations unique to immature speakers. Children have difficulty executing discrete tongue movements, preferring to move the tongue and jaw as a single unit. This predisposes the…

  3. QCD and Light-Front Holography

    Energy Technology Data Exchange (ETDEWEB)

    Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins; de Teramond, Guy F.; /Costa Rica U.

    2010-10-27

    The soft-wall AdS/QCD model, modified by a positive-sign dilaton metric, leads to a remarkable one-parameter description of nonperturbative hadron dynamics. The model predicts a zero-mass pion for zero-mass quarks and a Regge spectrum of linear trajectories with the same slope in the leading orbital angular momentum L of hadrons and the radial quantum number N. Light-Front Holography maps the amplitudes which are functions of the fifth dimension variable z of anti-de Sitter space to a corresponding hadron theory quantized on the light front. The resulting Lorentz-invariant relativistic light-front wave equations are functions of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. The result is to a semi-classical frame-independent first approximation to the spectra and light-front wavefunctions of meson and baryon light-quark bound states, which in turn predict the behavior of the pion and nucleon form factors. The theory implements chiral symmetry in a novel way: the effects of chiral symmetry breaking increase as one goes toward large interquark separation, consistent with spectroscopic data, and the the hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. The soft-wall model also predicts the form of the non-perturbative effective coupling {alpha}{sub s}{sup AdS} (Q) and its {beta}-function which agrees with the effective coupling {alpha}{sub g1} extracted from the Bjorken sum rule. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms. A new perspective on quark and gluon condensates is also reviewed.

  4. New results in light-front phenomenology

    International Nuclear Information System (INIS)

    Brodsky, S.J.

    2005-01-01

    The light-front quantization of gauge theories in light-cone gauge provides a frame-independent wavefunction representation of relativistic bound states, simple forms for current matrix elements, explicit unitarity, and a trivial vacuum. In this talk I review the theoretical methods and constraints which can be used to determine these central elements of QCD phenomenology. The freedom to choose the light-like quantization four-vector provides an explicitly covariant formulation of light-front quantization and can be used to determine the analytic structure of light-front wave functions and define a kinematical definition of angular momentum. The AdS/CFT correspondence of large N c supergravity theory in higher-dimensional anti-de Sitter space with supersymmetric QCD in four-dimensional space-time has interesting implications for hadron phenomenology in the conformal limit, including an all-orders demonstration of counting rules for exclusive processes. String/gauge duality also predicts the QCD power-law behavior of light-front Fock-state hadronic wavefunctions with arbitrary orbital angular momentum at high momentum transfer. The form of these near-conformal wavefunctions can be used as an initial ansatz for a variational treatment of the light-front QCD Hamiltonian. The light-front Fock-state wavefunctions encode the bound state properties of hadrons in terms of their quark and gluon degrees of freedom at the amplitude level. The nonperturbative Fock-state wavefunctions contain intrinsic gluons, and sea quarks at any scale Q with asymmetries such as s(x) ≠ s-bar(x), u-bar(x) ≠ d-bar(x). Intrinsic charm and bottom quarks appear at large x in the light-front wavefunctions since this minimizes the invariant mass and off-shellness of the higher Fock state. In the case of nuclei, the Fock state expansion contains 'hidden color' states which cannot be classified in terms of of nucleonic degrees of freedom. I also briefly review recent analyses which show that some

  5. National volcanic ash operations plan for aviation

    Science.gov (United States)

    ,; ,

    2007-01-01

    The National Aviation Weather Program Strategic Plan (1997) and the National Aviation Weather Initiatives (1999) both identified volcanic ash as a high-priority informational need to aviation services. The risk to aviation from airborne volcanic ash is known and includes degraded engine performance (including flameout), loss of visibility, failure of critical navigational and operational instruments, and, in the worse case, loss of life. The immediate costs for aircraft encountering a dense plume are potentially major—damages up to $80 million have occurred to a single aircraft. Aircraft encountering less dense volcanic ash clouds can incur longer-term costs due to increased maintenance of engines and external surfaces. The overall goal, as stated in the Initiatives, is to eliminate encounters with ash that could degrade the in-flight safety of aircrews and passengers and cause damage to the aircraft. This goal can be accomplished by improving the ability to detect, track, and forecast hazardous ash clouds and to provide adequate warnings to the aviation community on the present and future location of the cloud. To reach this goal, the National Aviation Weather Program established three objectives: (1) prevention of accidental encounters with hazardous clouds; (2) reduction of air traffic delays, diversions, or evasive actions when hazardous clouds are present; and (3) the development of a single, worldwide standard for exchange of information on airborne hazardous materials. To that end, over the last several years, based on numerous documents (including an OFCMsponsored comprehensive study on aviation training and an update of Aviation Weather Programs/Projects), user forums, and two International Conferences on Volcanic Ash and Aviation Safety (1992 and 2004), the Working Group for Volcanic Ash (WG/VA), under the OFCM-sponsored Committee for Aviation Services and Research, developed the National Volcanic Ash Operations Plan for Aviation and Support of the

  6. QCD Phenomenology and Light-Front Wavefunctions

    International Nuclear Information System (INIS)

    Brodsky, Stanley J.

    2001-01-01

    A natural calculus for describing the bound-state structure of relativistic composite systems in quantum field theory is the light-front Fock expansion which encodes the properties of a hadrons in terms of a set of frame-independent n-particle wavefunctions. Light-front quantization in the doubly-transverse light-cone gauge has a number of remarkable advantages, including explicit unitarity, a physical Fock expansion, the absence of ghost degrees of freedom, and the decoupling properties needed to prove factorization theorems in high momentum transfer inclusive and exclusive reactions. A number of applications are discussed in these lectures, including semileptonic B decays, two-photon exclusive reactions, diffractive dissociation into jets, and deeply virtual Compton scattering. The relation of the intrinsic sea to the light-front wavefunctions is discussed. Light-front quantization can also be used in the Hamiltonian form to construct an event generator for high energy physics reactions at the amplitude level. The light-cone partition function, summed over exponentially weighted light-cone energies, has simple boost properties which may be useful for studies in heavy ion collisions. I also review recent work which shows that the structure functions measured in deep inelastic lepton scattering are affected by final-state rescattering, thus modifying their connection to light-front probability distributions. In particular, the shadowing of nuclear structure functions is due to destructive interference effects from leading-twist diffraction of the virtual photon, physics not included in the nuclear light-cone wavefunctions

  7. Venus - Volcanic features in Atla Region

    Science.gov (United States)

    1991-01-01

    This Magellan image from the Atla region of Venus shows several types of volcanic features and superimposed surface fractures. The area in the image is approximately 350 kilometers (217 miles) across, centered at 9 degrees south latitude, 199 degrees east longitude. Lava flows emanating from circular pits or linear fissures form flower-shaped patterns in several areas. A collapse depression approximately 20 kilometers by 10 kilometers (12 by 6 miles) near the center of the image is drained by a lava channel approximately 40 kilometers (25 miles) long. Numerous surface fractures and graben (linear valleys) criss-cross the volcanic deposits in north to northeast trends. The fractures are not buried by the lavas, indicating that the tectonic activity post-dates most of the volcanic activity.

  8. 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.

  9. Geochemistry of volcanic series of Aragats province

    International Nuclear Information System (INIS)

    Meliksetyan, Kh.B.

    2012-01-01

    In this contribution we discuss geochemical and isotope characteristics of volcanism of the Aragats volcanic province and possible petrogenetical models of magma generation in collision zone of Armenian highland. We talk about combination of some specific features of collision related volcanism such as dry and high temperature conditions of magma generation, that demonstrate some similarities to intraplate-like petrogenesis and presence of mantle source enriched by earlier subductions, indicative to island-arc type magma generation models. Based on comprehensive analysis of isotope and geochemical data and some published models of magma generation beneath Aragats we lead to a petrogenetic model of origin of Aragats system to be a result of magma mixture between mantle originated mafic magma with felsic, adakite-type magmas

  10. Tropical Volcanic Soils From Flores Island, Indonesia

    Directory of Open Access Journals (Sweden)

    Hikmatullah

    2010-01-01

    Full Text Available Soils that are developed intropical region with volcanic parent materials have many unique properties, and high potential for agricultural use.The purpose of this study is to characterize the soils developed on volcanic materials from Flores Island, Indonesia,and to examine if the soils meet the requirements for andic soil properties. Selected five soils profiles developed fromandesitic volcanic materials from Flores Island were studied to determine their properties. They were compared intheir physical, chemical and mineralogical characteristics according to their parent material, and climatic characteristicdifferent. The soils were developed under humid tropical climate with ustic to udic soil moisture regimes withdifferent annual rainfall. The soils developed from volcanic ash parent materials in Flores Island showed differentproperties compared to the soils derived from volcanic tuff, even though they were developed from the sameintermediary volcanic materials. The silica contents, clay mineralogy and sand fractions, were shown as the differences.The different in climatic conditions developed similar properties such as deep solum, dark color, medium texture, andvery friable soil consistency. The soils have high organic materials, slightly acid to acid, low to medium cationexchange capacity (CEC. The soils in western region have higher clay content and showing more developed than ofthe eastern region. All the profiles meet the requirements for andic soil properties, and classified as Andisols order.The composition of sand mineral was dominated by hornblende, augite, and hypersthenes with high weatherablemineral reserves, while the clay fraction was dominated by disordered kaolinite, and hydrated halloysite. The soilswere classified into subgroup as Thaptic Hapludands, Typic Hapludands, and Dystric Haplustands

  11. Tellurium in active volcanic environments: Preliminary results

    Science.gov (United States)

    Milazzo, Silvia; Calabrese, Sergio; D'Alessandro, Walter; Brusca, Lorenzo; Bellomo, Sergio; Parello, Francesco

    2014-05-01

    Tellurium is a toxic metalloid and, according to the Goldschmidt classification, a chalcophile element. In the last years its commercial importance has considerably increased because of its wide use in solar cells, thermoelectric and electronic devices of the last generation. Despite such large use, scientific knowledge about volcanogenic tellurium is very poor. Few previous authors report result of tellurium concentrations in volcanic plume, among with other trace metals. They recognize this element as volatile, concluding that volcanic gases and sulfur deposits are usually enriched with tellurium. Here, we present some results on tellurium concentrations in volcanic emissions (plume, fumaroles, ash leachates) and in environmental matrices (soils and plants) affected by volcanic emissions and/or deposition. Samples were collected at Etna and Vulcano (Italy), Turrialba (Costa Rica), Miyakejima, Aso, Asama (Japan), Mutnovsky (Kamchatka) at the crater rims by using common filtration techniques for aerosols (polytetrafluoroethylene filters). Filters were both eluted with Millipore water and acid microwave digested, and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Volcanic ashes emitted during explosive events on Etna and Copahue (Argentina) were analyzed for tellurium bulk composition and after leaching experiments to evaluate the soluble fraction of tellurium. Soils and leaves of vegetation were also sampled close to active volcanic vents (Etna, Vulcano, Nisyros, Nyiragongo, Turrialba, Gorely and Masaya) and investigated for tellurium contents. Preliminary results showed very high enrichments of tellurium in volcanic emissions comparing with other volatile elements like mercury, arsenic, thallium and bismuth. This suggests a primary transport in the volatile phase, probably in gaseous form (as also suggested by recent studies) and/or as soluble salts (halides and/or sulfates) adsorbed on the surface of particulate particles and ashes. First

  12. Volcanic air pollution hazards in Hawaii

    Science.gov (United States)

    Elias, Tamar; Sutton, A. Jeff

    2017-04-20

    Noxious sulfur dioxide gas and other air pollutants emitted from Kīlauea Volcano on the Island of Hawai‘i react with oxygen, atmospheric moisture, and sunlight to produce volcanic smog (vog) and acid rain. Vog can negatively affect human health and agriculture, and acid rain can contaminate household water supplies by leaching metals from building and plumbing materials in rooftop rainwater-catchment systems. U.S. Geological Survey scientists, along with health professionals and local government officials are working together to better understand volcanic air pollution and to enhance public awareness of this hazard.

  13. Volcanic Eruptions and Climate: Outstanding Research Issues

    Science.gov (United States)

    Robock, Alan

    2016-04-01

    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 this aerosol cloud produce responses in the climate system. Based on observations after major eruptions of the past and experiments with numerical models of the climate system, we understand much about their climatic impact, but there are also a number of unanswered questions. Volcanic eruptions produce global cooling, and are an important natural cause of interannual, interdecadal, and even centennial-scale climate change. One of the most interesting volcanic effects is the "winter warming" of Northern Hemisphere continents following major tropical eruptions. During the winter in the Northern Hemisphere following every large tropical eruption of the past century, surface air temperatures over North America, Europe, and East Asia were warmer than normal, while they were colder over Greenland and the Middle East. This pattern and the coincident atmospheric circulation correspond to the positive phase of the Arctic Oscillation. While this response is observed after recent major eruptions, most state-of-the-art climate models have trouble simulating winter warming. Why? High latitude eruptions in the Northern Hemisphere, while also producing global cooling, do not have the same impact on atmospheric dynamics. Both tropical and high latitude eruptions can weaken the Indian and African summer monsoon, and the effects can be seen in past records of flow in the Nile and Niger Rivers. 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 have had a small effect on global temperature trends. Some important outstanding research questions include: How much seasonal, annual, and decadal predictability is possible following a large volcanic eruption? Do

  14. Winter warming from large volcanic eruptions

    Science.gov (United States)

    Robock, Alan; Mao, Jianping

    1992-01-01

    An examination of the Northern Hemisphere winter surface temperature patterns after the 12 largest volcanic eruptions from 1883-1992 shows warming over Eurasia and North America and cooling over the Middle East which are significant at the 95-percent level. This pattern is found in the first winter after tropical eruptions, in the first or second winter after midlatitude eruptions, and in the second winter after high latitude eruptions. The effects are independent of the hemisphere of the volcanoes. An enhanced zonal wind driven by heating of the tropical stratosphere by the volcanic aerosols is responsible for the regions of warming, while the cooling is caused by blocking of incoming sunlight.

  15. Evidences for a volcanic province in the Central Indian Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.; Sudhakar, M.

    Based on various lines of evidence such as the widespread occurrence of basalts, pumice, volcanic glass shards and their transformational products (zeolites, palagonites, and smectite-rich sediments), we suggest the presence of a volcanic province...

  16. Managing Controversies in the Fuzzy Front End

    DEFF Research Database (Denmark)

    Christiansen, John K.; Gasparin, Marta

    2016-01-01

    . The analysis investigates the microprocesses around the controversies that emerge during the fuzzy front end of four products. Five different types of controversies are identified: profit, production, design, brand and customers/market. Each controversy represents a threat, but also an opportunity to search...... for new solutions in the unpredictable non-linear processes. The study uses an ethnographic approach using qualitative data from interviews, company documents, external communication and marketing material, minutes of meetings, informal conversations and observations. The analysis of four FFE processes...... demonstrates how the fuzzy front requires managers to deal with controversies that emerge from many different places and involve both human and non-human actors. Closing the controversies requires managers to take account of the situation, identify the problem that needs to be addressed, and initiate a search...

  17. Multiclass gene selection using Pareto-fronts.

    Science.gov (United States)

    Rajapakse, Jagath C; Mundra, Piyushkumar A

    2013-01-01

    Filter methods are often used for selection of genes in multiclass sample classification by using microarray data. Such techniques usually tend to bias toward a few classes that are easily distinguishable from other classes due to imbalances of strong features and sample sizes of different classes. It could therefore lead to selection of redundant genes while missing the relevant genes, leading to poor classification of tissue samples. In this manuscript, we propose to decompose multiclass ranking statistics into class-specific statistics and then use Pareto-front analysis for selection of genes. This alleviates the bias induced by class intrinsic characteristics of dominating classes. The use of Pareto-front analysis is demonstrated on two filter criteria commonly used for gene selection: F-score and KW-score. A significant improvement in classification performance and reduction in redundancy among top-ranked genes were achieved in experiments with both synthetic and real-benchmark data sets.

  18. Trace metal fronts in European shelf waters

    International Nuclear Information System (INIS)

    Kremling, K.

    1983-01-01

    The Hebrides shelf edge area is characterized by strong horizontal salinity gradients (fronts) which mark the boundary between Scottish coastal and oceanic waters. The results presented here, obtained in summer 1981 on a transect between the open north Atlantic and the German Bight, confirm that the hydrographical front is accompanied by dramatic increases in inorganic nutrients (phosphate, silicate) and dissolved trace elements such as Cd, Cu, Mn, and 226 Ra. These data (together with measurements from North Sea regions) suggest that the trace metals are mobilized from partly reduced (organic-rich) sediments and vertically mixed into the surface waters. The regional variations evident from the transect are interpreted as being the result of the hydrography prevailing in waters around the British Isles. (author)

  19. Improving volcanic ash forecasts with ensemble-based data assimilation

    NARCIS (Netherlands)

    Fu, Guangliang

    2017-01-01

    The 2010 Eyjafjallajökull volcano eruption had serious consequences to civil aviation. This has initiated a lot of research on volcanic ash forecasting in recent years. For forecasting the volcanic ash transport after eruption onset, a volcanic ash transport and diffusion model (VATDM) needs to be

  20. Volcanic Characteristics of Kueishantao in Northeast Taiwan and Their Implications

    Directory of Open Access Journals (Sweden)

    Ching-Lung Chiu

    2010-01-01

    Full Text Available Kueishantao (KST is a small offshore volcanic island located at the southernmost part of the Okinawa Trough. In this study, we conducted a detailed mapping incorporating the new high resolution LiDAR DTM laser scanning device to accurately construct a volcanic sequence. A new 1/5000 geological map was established. One primary volcanic cone, composed of layers of both lava flows and pyroclastic rocks constituted the major edifice of KST. The other minor volcanic cone, which consists of volcanic lapillis and blocks, is seated to the east of the main cone. The escarped and nearly straight coast in the southern part of the KST indicates that the volcano suffered a large post-volcanic edifice collapse erasing nearly one half of the volume of both volcanic cones. The increase in the abundance of the xenoliths of sedimentary rocks from the lower to the upper part of the volcanic sequence indicates that the formation of volcanic rocks of the KST involved an intensification of crustal contamination. The possibility of volcanic eruption can not be excluded in the future based on the present thermolu¬minescene age data of 7 ka. The associated eruptive ash fall and tsunami induced by the further collapse of the KST volcanic edifice might have great influence to the adjacent inland. Thus, long-term monitoring of volcanic activities around KST should be required for future hazard assessments.

  1. Apollo 15 mare volcanism: constraints and problems

    International Nuclear Information System (INIS)

    Delano, J.W.

    1985-01-01

    The Apollo 15 landing site contains more volcanics in the form of crystalline basalts and pristine glasses, which form the framework for all models dealing with the mantle beneath that site. Major issues on the petrology of the mare source regions beneath that portion of Mare Imbrium are summarized

  2. Monogenetic volcanism: personal views and discussion

    Science.gov (United States)

    Németh, K.; Kereszturi, G.

    2015-11-01

    Monogenetic volcanism produces small-volume volcanoes with a wide range of eruptive styles, lithological features and geomorphic architectures. They are classified as spatter cones, scoria (or cinder) cones, tuff rings, maars (maar-diatremes) and tuff cones based on the magma/water ratio, dominant eruption styles and their typical surface morphotypes. The common interplay between internal, such as the physical-chemical characteristics of magma, and external parameters, such as groundwater flow, substrate characteristics or topography, plays an important role in creating small-volume volcanoes with diverse architectures, which can give the impression of complexity and of similarities to large-volume polygenetic volcanoes. In spite of this volcanic facies complexity, we defend the term "monogenetic volcano" and highlight the term's value, especially to express volcano morphotypes. This study defines a monogenetic volcano, a volcanic edifice with a small cumulative volume (typically ≤1 km3) that has been built up by one continuous, or many discontinuous, small eruptions fed from one or multiple magma batches. This definition provides a reasonable explanation of the recently recognized chemical diversities of this type of volcanism.

  3. Payenia volcanic province, southern Mendoza, Argentina

    DEFF Research Database (Denmark)

    Søager, Nina; Holm, Paul Martin; Llambias, Eduardo Jorge

    2013-01-01

    The Pleistocene to Holocene Payenia volcanic province is a backarc region of 60,000 km2 in Mendoza, Argentina, which is dominated by transitional to alkaline basalts and trachybasalts. We present major and trace element compositions of 139 rocks from this area of which the majority are basaltic...

  4. Monitoring and forecasting Etna volcanic plumes

    Directory of Open Access Journals (Sweden)

    S. Scollo

    2009-09-01

    Full Text Available In this paper we describe the results of a project ongoing at the Istituto Nazionale di Geofisica e Vulcanologia (INGV. The objective is to develop and implement a system for monitoring and forecasting volcanic plumes of Etna. Monitoring is based at present by multispectral infrared measurements from the Spin Enhanced Visible and Infrared Imager on board the Meteosat Second Generation geosynchronous satellite, visual and thermal cameras, and three radar disdrometers able to detect ash dispersal and fallout. Forecasting is performed by using automatic procedures for: i downloading weather forecast data from meteorological mesoscale models; ii running models of tephra dispersal, iii plotting hazard maps of volcanic ash dispersal and deposition for certain scenarios and, iv publishing the results on a web-site dedicated to the Italian Civil Protection. Simulations are based on eruptive scenarios obtained by analysing field data collected after the end of recent Etna eruptions. Forecasting is, hence, supported by plume observations carried out by the monitoring system. The system was tested on some explosive events occurred during 2006 and 2007 successfully. The potentiality use of monitoring and forecasting Etna volcanic plumes, in a way to prevent threats to aviation from volcanic ash, is finally discussed.

  5. X-ray microanalysis of volcanic ash

    International Nuclear Information System (INIS)

    Kearns, S L; Buse, B

    2012-01-01

    The 2010 eruption of Eyjafjallajökull volcano in Iceland demonstrated the disruptive nature of high-level volcanic ash emissions to the world's air traffic. The chemistry of volcanic material is complex and varied. Different eruptions yield both compositional and morphological variation. Equally a single eruption, such as that in Iceland will evolve over time and may potentially produce a range of volcanic products of varying composition and morphology. This variability offers the petrologist the opportunity to derive a tracer to the origins both spatially and temporally of a single particle by means of electron microbeam analysis. EPMA of volcanic ash is now an established technique for this type of analysis as used in tephrachronology. However, airborne paniculate material may, as in the case of Eyjafjallajökull, result in a particle size that is too small and too dispersed for preparation of standard EPMA mounts. Consequently SEM-EDS techniques are preferred for this type of quantitative analysis . Results of quantitative SEM-EDS analysis yield data with a larger precision error than EPMA yet sufficient to source the original eruption. Uncoated samples analyzed using variable pressure SEM yield slightly poorer results at modest pressures.

  6. Amazonian volcanism inside Valles Marineris on Mars

    Czech Academy of Sciences Publication Activity Database

    Brož, Petr; Hauber, E.; Wray, J. J.; Michael, G.

    2017-01-01

    Roč. 473, September (2017), s. 122-130 ISSN 0012-821X Institutional support: RVO:67985530 Keywords : Mars * Valles Marineris * volcanism * scoria cone * hydrothermal activity Subject RIV: DC - Siesmology, Volcanology, Earth Structure OBOR OECD: Volcanology Impact factor: 4.409, year: 2016

  7. The Elusive Evidence of Volcanic Lightning.

    Science.gov (United States)

    Genareau, K; Gharghabi, P; Gafford, J; Mazzola, M

    2017-11-14

    Lightning strikes are known to morphologically alter and chemically reduce geologic formations and deposits, forming fulgurites. A similar process occurs as the result of volcanic lightning discharge, when airborne volcanic ash is transformed into lightning-induced volcanic spherules (LIVS). Here, we adapt the calculations used in previous studies of lightning-induced damage to infrastructure materials to determine the effects on pseudo-ash samples of simplified composition. Using laboratory high-current impulse experiments, this research shows that within the lightning discharge channel there is an ideal melting zone that represents roughly 10% or less of the total channel radius at which temperatures are sufficient to melt the ash, regardless of peak current. The melted ash is simultaneously expelled from the channel by the heated, expanding air, permitting particles to cool during atmospheric transport before coming to rest in ash fall deposits. The limited size of this ideal melting zone explains the low number of LIVS typically observed in volcanic ash despite the frequent occurrence of lightning during explosive eruptions.

  8. Prototype ALICE front-end card

    CERN Multimedia

    Maximilien Brice

    2004-01-01

    This circuit board is a prototype 48-channel front end digitizer card for the ALICE time projection chamber (TPC), which takes electrical signals from the wire sensors in the TPC and shapes the data before converting the analogue signal to digital data. A total of 4356 cards will be required to process the data from the ALICE TPC, the largest of this type of detector in the world.

  9. Front Cover Photograph & Interview for FREEYE Magazine

    OpenAIRE

    Murray, Matthew

    2003-01-01

    Matthew Murray Front Cover Photograph & Interview for FREEYE Magazine - Dutch Quarterly For Exceptional International Photography, Holland.\\ud The article focuses on Murray's practice, his personal work, commissioned work, advertising, gallery and exhibition work along with his methodology. Looking at Murray's inspirations and how they feed into his personal projects and how this personal work feeds into shooting above the line advertising campaigns. Murray's work blurs the lines between pers...

  10. Wave Front Sensor for Solar Concentrator Control

    Science.gov (United States)

    2009-10-01

    terrestrial-based and space-based. Both types of concentrator can be either imaging or nonimaging and they can be rigid or inflatable. Other...and T is the temperature of the absorber and propellant. In (5), Iin is input intensity with effects of the optical path through the concentrator acting...Hartmann in 1900 and was used for checking optical telescopes for aberrations. It was an array of holes in a plate placed in front of the mirror of

  11. Fronting and exhaustive exclusion in Biblical Hebrew

    African Journals Online (AJOL)

    Kate H

    48, 2017, 219-222 doi: 10.5774/48-0-292. Fronting and exhaustive exclusion in Biblical Hebrew. Christo H. J. van der Merwe. Department of Ancient Studies, University of Stellenbosch, South ... Merwe, Naudé and Kroeze 2017: 491-493). .... “And I will give him to the Lord all the days of his life, and no razor shall touch his.

  12. Sources of Quaternary volcanism in the Itasy and Ankaratra volcanic fields, Madagascar

    Science.gov (United States)

    Rasoazanamparany, C.; Widom, E.; Kuentz, D. C.; Raharimahefa, T.; Rakotondrazafy, F. M. A.; Rakotondravelo, K. M.

    2017-12-01

    We present new major and trace element and Sr, Nd, Pb and Os isotope data for Quaternary basaltic lavas and tephra from the Itasy and Ankaratra volcanic fields, representing the most recent volcanism in Madagascar. Mafic magmas from Itasy and Ankaratra exhibit significant inter- and intra-volcanic field geochemical heterogeneity. The Itasy eruptive products range in composition from foidite to phonotephrite whereas Ankaratra lavas range from basanite to trachybasalts. Trace element signatures of samples from both volcanic fields are very similar to those of ocean island basalts (OIB), with significant enrichment in Nb and Ta, depletion in Rb, Cs, and K, and relatively high Nb/U and Ce/Pb. However, the Itasy volcanic rocks show enrichment relative to those of Ankaratra in most incompatible elements, indicative of a more enriched source and/or lower degrees of partial melting. Significant inter- and intra-volcanic field heterogeneity is also observed in Sr, Nd, Pb and Os isotope signatures. The Itasy volcanic rocks generally have less radiogenic Sr and Nd isotopic ratios but more radiogenic Pb isotopic signatures than the Ankaratra volcanic field. Together, the Itasy and Ankaratra volcanic rocks form a well-defined negative correlation in Sr vs. Pb isotopes that could be attributed to lithospheric contamination or variable degrees of mixing between distinct mantle sources. However, the lack of correlation between isotopes and indices of crustal contamination (e.g. MgO and Nb/U) are inconsistent with shallow lithospheric contamination, and instead suggest mixing between compositionally distinct mantle sources. Furthermore, although Sr-Pb isotope systematics are apparently consistent with mixing between two different sources, distinct trends in Sr vs. Nd isotopes displayed by samples from Itasy and Ankaratra, respectively, argue for more complex source mixing involving three or more sources. The current data demonstrate that although the Itasy and Ankaratra volcanic

  13. Microphysical Properties of Alaskan Volcanic Ash

    Science.gov (United States)

    Puthukkudy, A.; Espinosa, R.; Rocha Lima, A.; Remer, L.; Colarco, P. R.; Whelley, P.; Krotkov, N. A.; Young, K.; Dubovik, O.; Wallace, K.; Martins, J. V.

    2017-12-01

    Volcanic ash has the potential to cause a variety of severe problems for human health and the environment. Therefore, effective monitoring of the dispersion and fallout from volcanic ash clouds and characterization of the aerosol particle properties are essential. One way to acquire information from volcanic clouds is through satellite remote sensing: such images have greater coverage than ground-based observations and can present a "big picture" perspective. A challenge of remote sensing is that assumptions of certain properties of the target are often a pre-requisite for making accurate and quantitative retrievals. For example, detailed information about size distribution, sphericity, and optical properties of the constituent matter is needed or must be assumed. The same kind of information is also needed for atmospheric transport models to properly simulate the dispersion and fallout of volcanic ash. Presented here is a laboratory method to determine the microphysical and optical properties of volcanic ash samples collected from two Alaskan volcanoes with markedly different compositions. Our method uses a Polarized Imaging Nephelometer (PI-Neph) and a system that re-suspends the particles in an air flow. The PI-Neph measures angular light scattering and polarization of the re-suspended particles from 3o to 175o in scattering angle, with an angular resolution of 1o . Primary measurements include phase function and polarized phase function at three wavelengths (445nm, 532nm, and 661nm). Size distribution, sphericity, and complex refractive index are retrieved indirectly from the PI-Neph measurements using the GRASP (Generalized Retrieval of Aerosol and Surface Properties) inversion algorithm. We report the results of this method applied to samples from the Mt. Okmok (2008) and Mt. Katmai (1912) volcanic eruptions. To our knowledge, this is the first time direct measurements of phase matrix elements of ash from Mt. Okmok and Mt. Katmai have been reported. Retrieved

  14. Fluids in volcanic and geothermal systems

    Science.gov (United States)

    Sigvaldason, Gudmundur E.

    Mineral buffers control the composition of most volatile components of magmas and dissolved species in geothermal fluids. The only element which occurs in significant quantities in volcanic and geothermal fluids and is not controlled by mineral buffers is chlorine. It is argued that in absence of marine influence, geothermal fluids reflect the chlorine content of associated magmatic fluids. The chlorine content of oceanic volcanic rocks has a positive correlation with elements, which are believed to indicate a heterogenous source region. Since the source is generally believed to be the Earth's mantle, the implication is that the mantle is heterogenous with regard to chlorine and other volatiles. Such heterogeneities would have important consequences for genesis and distribution of ore. All major magma types of the oceanic environment occur in Iceland. Their spatial distribution is closely related to a volcanotectonic pattern, suggesting crustal control. A geophysical model of crustal accretion in a rift zone is used in conjunction with classical petrology to predict geochemical processes in a rift zone crust. The model has two kinematic parameters-drift rate and subsidence rate-which combined describe trajectories of mass particles deposited on the surface. When considering in conjunction with thermal gradients of the rift zone a series of metamorphic reactions and chemical fractionation processes are bound to occur, eventually resulting in a layering of the oceanic crust. The physical parameters result in a derived variable, rift zone residence time, which depends on the width of a rift zone. Long residence times in a wide rift zone lead to multistage recycling of material. Other properties of the model, based on geometric arrangement of productive fissure swarms within a rift zone, explain off-rift volcanism as directly related to rift zone processes, either as plate trapped magmatic domains or a transgressive thermal anomaly into an older crust. Off

  15. Kinetics of a plasma streamer ionization front

    Science.gov (United States)

    Taccogna, Francesco; Pellegrini, Fabrizio

    2018-02-01

    A streamer is a non-linear and non-local gas breakdown mode. Its large-scale coherent structures, such as the ionization front, are the final results of a hierarchical cascade starting from the single particle dynamics. Therefore, this phenomenon covers, by definition, different space and time scales. In this study, we have reproduced the ionization front formation and development by means of a particle-based numerical methodology. The physical system investigated concerns of a high-voltage ns-pulsed surface dielectric barrier discharge. Different reduced electric field regimes ranging from 50 to 500 Td have been considered for two gases: pure atomic Ar and molecular N2. Results have shown the detailed structure of the negative streamer: the leading edge, the head, the interior and the tail. Its dynamical evolution and the front propagation velocity have been calculated for the different cases. Finally, the deviation of the electron energy distribution function from equilibrium behavior has been pointed out as a result of a fast and very localized phenomenon.

  16. Wintertime sea surface temperature fronts in the Taiwan Strait

    Science.gov (United States)

    Chang, Yi; Shimada, Teruhisa; Lee, Ming-An; Lu, Hsueh-Jung; Sakaida, Futoki; Kawamura, Hiroshi

    2006-12-01

    We present wintertime variations and distributions of sea surface temperature (SST) fronts in the Taiwan Strait by applying an entropy-based edge detection method to 10-year (1996-2005) satellite SST images with grid size of 0.01°. From climatological monthly mean maps of SST gradient magnitude in winter, we identify four significant SST fronts in the Taiwan Strait. The Mainland China Coastal Front is a long frontal band along the 50-m isobath near the Chinese coast. The sharp Peng-Chang Front appears along the Peng-Hu Channel and extends northward around the Chang-Yuen Ridge. The Taiwan Bank Front evolves in early winter. As the winter progresses, the front becomes broad and moves toward the Chinese coast, connecting to the Mainland China Coastal Front. The Kuroshio Front extends northeastward from the northeastern tip of Taiwan with a semicircle-shape curving along the 100-m isobath.

  17. Bibliometric analysis of acupuncture research fronts and their ...

    African Journals Online (AJOL)

    Bibliometric analysis of acupuncture research fronts and their worldwide ... This study chronologically examined the changing features and research fronts of ... from the Science Citation Index Expanded and Social Science Citation Index.

  18. Pacific seamount volcanism in space and time

    Science.gov (United States)

    Hillier, J. K.

    2007-02-01

    Seamounts constitute some of the most direct evidence about intraplate volcanism. As such, when seamounts formed and into which tectonic setting they erupted (i.e. on-ridge or off-ridge) are a useful reflection of how the properties of the lithosphere interact with magma generation in the fluid mantle beneath. Proportionately few seamounts are radiometrically dated however, and these tend to be recently active. In order to more representatively sample and better understand Pacific seamount volcanism this paper estimates the eruption ages (tvolc) of 2706 volcanoes via automated estimates of lithospheric strength. Lithospheric strength (GTRrel) is deduced from the ratio of gravity to topography above the summits of volcanoes, and is shown to correlate with seafloor age at the time of volcanic loading (Δt) at 61 sites where radiometric constraints upon Δt exist. A trend of fits data for these 61, and with seafloor age (tsf) known, can date the 2706 volcanoes; tvolc = tsf - Δt. Widespread recurrences of volcanism proximal to older features (e.g. the Cook-Austral alignment in French Polynesia) suggest that the lithosphere exerts a significant element of control upon the location of volcanism, and that magmatic throughput leaves the lithosphere more susceptible to the passage of future melts. Observations also prompt speculation that: the Tavara seamounts share morphological characteristics and isostatic compensation state with the Musicians, and probably formed similarly; the Easter Island chain may be a modern analogy to the Cross-Lines; a Musicians - South Hawaiian seamounts alignment may be deflecting the Hawaiian hotspot trace.

  19. Cooling Rates of Lunar Volcanic Glass Beads

    Science.gov (United States)

    Hui, Hejiu; Hess, Kai-Uwe; Zhang, Youxue; Peslier, Anne; Lange, Rebecca; Dingwell, Donald; Neal, Clive

    2016-01-01

    It is widely accepted that the Apollo 15 green and Apollo 17 orange glass beads are of volcanic origin. The diffusion profiles of volatiles in these glass beads are believed to be due to degassing during eruption (Saal et al., 2008). The degree of degassing depends on the initial temperature and cooling rate. Therefore, the estimations of volatiles in parental magmas of lunar pyroclastic deposits depend on melt cooling rates. Furthermore, lunar glass beads may have cooled in volcanic environments on the moon. Therefore, the cooling rates may be used to assess the atmospheric condition in an early moon, when volcanic activities were common. The cooling rates of glasses can be inferred from direct heat capacity measurements on the glasses themselves (Wilding et al., 1995, 1996a,b). This method does not require knowledge of glass cooling environments and has been applied to calculate the cooling rates of natural silicate glasses formed in different terrestrial environments. We have carried out heat capacity measurements on hand-picked lunar glass beads using a Netzsch DSC 404C Pegasus differential scanning calorimeter at University of Munich. Our preliminary results suggest that the cooling rate of Apollo 17 orange glass beads may be 12 K/min, based on the correlation between temperature of the heat capacity curve peak in the glass transition range and glass cooling rate. The results imply that the parental magmas of lunar pyroclastic deposits may have contained more water initially than the early estimations (Saal et al., 2008), which used higher cooling rates, 60-180 K/min in the modeling. Furthermore, lunar volcanic glass beads could have been cooled in a hot gaseous medium released from volcanic eruptions, not during free flight. Therefore, our results may shed light on atmospheric condition in an early moon.

  20. The Online GVP/USGS Weekly Volcanic Activity Report: Providing Timely Information About Worldwide Volcanism

    Science.gov (United States)

    Mayberry, G. C.; Guffanti, M. C.; Luhr, J. F.; Venzke, E. A.; Wunderman, R. L.

    2001-12-01

    The awesome power and intricate inner workings of volcanoes have made them a popular subject with scientists and the general public alike. About 1500 known volcanoes have been active on Earth during the Holocene, approximately 50 of which erupt per year. With so much activity occurring around the world, often in remote locations, it can be difficult to find up-to-date information about current volcanism from a reliable source. To satisfy the desire for timely volcano-related information the Smithsonian Institution and US Geological Survey combined their strengths to create the Weekly Volcanic Activity Report. The Smithsonian's Global Volcanism Program (GVP) has developed a network of correspondents while reporting worldwide volcanism for over 30 years in their monthly Bulletin of the Global Volcanism Network. The US Geological Survey's Volcano Hazards Program studies and monitors volcanoes in the United States and responds (upon invitation) to selected volcanic crises in other countries. The Weekly Volcanic Activity Report is one of the most popular sites on both organization's websites. The core of the Weekly Volcanic Activity Report is the brief summaries of current volcanic activity around the world. In addition to discussing various types of volcanism, the summaries also describe precursory activity (e.g. volcanic seismicity, deformation, and gas emissions), secondary activity (e.g. debris flows, mass wasting, and rockfalls), volcanic ash hazards to aviation, and preventative measures. The summaries are supplemented by links to definitions of technical terms found in the USGS photoglossary of volcano terms, links to information sources, and background information about reported volcanoes. The site also includes maps that highlight the location of reported volcanoes, an archive of weekly reports sorted by volcano and date, and links to commonly used acronyms. Since the Weekly Volcanic Activity Report's inception in November 2000, activity has been reported at

  1. Topology optimization of front metallization patterns for solar cells

    NARCIS (Netherlands)

    Gupta, D.K.; Langelaar, M.; Barink, M.; Keulen, F. van

    2015-01-01

    This paper presents the application of topology optimization (TO) for designing the front electrode patterns for solar cells. Improving the front electrode design is one of the approaches to improve the performance of the solar cells. It serves to produce the voltage distribution for the front

  2. The Ngorongoro Volcanic Highland and its relationships to volcanic deposits at Olduvai Gorge and East African Rift volcanism.

    Science.gov (United States)

    Mollel, Godwin F; Swisher, Carl C

    2012-08-01

    The Ngorongoro Volcanic Highland (NVH), situated adjacent and to the east of Olduvai Gorge in northern Tanzania, is the source of the immense quantities of lava, ignimbrite, air fall ash, and volcaniclastic debris that occur interbedded in the Plio-Pleistocene sedimentary deposits in the Laetoli and Olduvai areas. These volcanics have proven crucial to unraveling stratigraphic correlations, the age of these successions, the archaeological and paleontological remains, as well as the source materials from which the bulk of the stone tools were manufactured. The NVH towers some 2,000 m above the Olduvai and Laetoli landscapes, affecting local climate, run-off, and providing varying elevation - climate controlled ecosystem, habitats, and riparian corridors extending into the Olduvai and Laetoli lowlands. The NVH also plays a crucial role in addressing the genesis and history of East African Rift (EAR) magmatism in northern Tanzania. In this contribution, we provide age and petrochemical compositions of the major NVH centers: Lemagurut, basalt to benmorite, 2.4-2.2 Ma; Satiman, tephrite to phonolite, 4.6-3.5 Ma; Oldeani, basalt to trachyandesite, 1.6-1.5 Ma; Ngorongoro, basalt to rhyolite, 2.3-2.0 Ma; Olmoti, basalt to trachyte, 2.0-1.8 Ma; Embagai, nephelinite to phonolite, 1.2-0.6 Ma; and Engelosin, phonolite, 3-2.7 Ma. We then discuss how these correlate in time and composition with volcanics preserved at Olduvai Gorge. Finally, we place this into context with our current understanding as to the eruptive history of the NVH and relationship to East African Rift volcanism. Copyright © 2011 Elsevier Ltd. All rights reserved.

  3. Novel Perspectives from Light-Front QCD, Super-Conformal Algebra, and Light-Front Holography

    Energy Technology Data Exchange (ETDEWEB)

    Brodsky, Stanley J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-12-01

    Light-Front Quantization – Dirac’s “Front Form” – provides a physical, frame-independent formalism for hadron dynamics and structure. Observables such as structure functions, transverse momentum distributions, and distribution amplitudes are defined from the hadronic LFWFs. One obtains new insights into the hadronic mass scale, the hadronic spectrum, and the functional form of the QCD running coupling in the nonperturbative domain using light-front holography. In addition, superconformal algebra leads to remarkable supersymmetric relations between mesons and baryons. I also discuss evidence that the antishadowing of nuclear structure functions is nonuniversal; i.e., flavor dependent, and why shadowing and antishadowing phenomena may be incompatible with the momentum and other sum rules for the nuclear parton distribution functions.

  4. Conceptual model of volcanism and volcanic hazards of the region of Ararat valley, Armenia

    Science.gov (United States)

    Meliksetian, Khachatur; Connor, Charles; Savov, Ivan; Connor, Laura; Navasardyan, Gevorg; Manucharyan, Davit; Ghukasyan, Yura; Gevorgyan, Hripsime

    2015-04-01

    Armenia and the adjacent volcanically active regions in Iran, Turkey and Georgia are located in the collision zone between the Arabian and Eurasian lithospheric plates. The majority of studies of regional collision related volcanism use the model proposed by Keskin, (2003) where volcanism is driven by Neo-Tethyan slab break-off. In Armenia, >500 Quaternary-Holocene volcanoes from the Gegham, Vardenis and Syunik volcanic fields are hosted within pull-apart structures formed by active faults and their segments (Karakhanyan et al., 2002), while tectonic position of the large in volume basalt-dacite Aragats volcano and periphery volcanic plateaus is different and its position away from major fault lines necessitates more complex volcano-tectonic setup. Our detailed volcanological, petrological and geochemical studies provide insight into the nature of such volcanic activity in the region of Ararat Valley. Most magmas, such as those erupted in Armenia are volatile-poor and erupt fairly hot. Here we report newly discovered tephra sequences in Ararat valley, that were erupted from historically active Ararat stratovolcano and provide evidence for explosive eruption of young, mid K2O calc-alkaline and volatile-rich (>4.6 wt% H2O; amph-bearing) magmas. Such young eruptions, in addition to the ignimbrite and lava flow hazards from Gegham and Aragats, present a threat to the >1.4 million people (~ ½ of the population of Armenia). We will report numerical simulations of potential volcanic hazards for the region of Ararat valley near Yerevan that will include including tephra fallout, lava flows and opening of new vents. Connor et al. (2012) J. Applied Volcanology 1:3, 1-19; Karakhanian et al. (2002), JVGR, 113, 319-344; Keskin, M. (2003) Geophys. Res. Lett. 30, 24, 8046.

  5. Volcanic Gases and Hot Spring Water to Evaluate the Volcanic Activity of the Mt. Baekdusan

    Science.gov (United States)

    Yun, S. H.; Lee, S.; Chang, C.

    2017-12-01

    This study performed the analysis on the volcanic gases and hot spring waters from the Julong hot spring at Mt. Baekdu, also known as Changbaishan on the North Korea(DPRK)-China border, during the period from July 2015 to August 2016. Also, we confirmed the errors that HCO3- concentrations of hot spring waters in the previous study (Lee et al. 2014) and tried to improve the problem. Dissolved CO2 in hot spring waters was analyzed using gas chromatograph in Lee et al.(2014). Improving this, from 2015, we used TOC-IC to analysis dissolved CO2. Also, we analyzed the Na2CO3 standard solutions of different concentrations using GC, and confirmed the correlation between the analytical concentrations and the real concentrations. However, because the analytical results of the Julong hot spring water were in discord with the estimated values based on this correlation, we can't estimate the HCO3-concentrations of 2014 samples. During the period of study, CO2/CH4 ratios in volcanic gases are gradually decreased, and this can be interpreted in two different ways. The first interpretation is that the conditions inside the volcanic edifice are changing into more reduction condition, and carbon in volcanic gases become more favorable to distribute into CH4 or CO than CO2. The second interpretation is that the interaction between volcanic gases and water becomes greater than past, and the concentrations of CO2which have much higher solubility in water decreased, relatively. In general, the effect of scrubbing of volcanic gas is strengthened during the quiet periods of volcanic activity rather than active periods. Meanwhile, the analysis of hot spring waters was done on the anion of acidic gases species, the major cations, and some trace elements (As, Cd, Re).This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMIPA 2015-3060.

  6. [Effects of volcanic eruptions on human health in Iceland. Review].

    Science.gov (United States)

    Gudmundsson, Gunnar; Larsen, Guðrun

    2016-01-01

    Volcanic eruptions are common in Iceland and have caused health problems ever since the settlement of Iceland. Here we describe volcanic activity and the effects of volcanic gases and ash on human health in Iceland. Volcanic gases expelled during eruptions can be highly toxic for humans if their concentrations are high, irritating the mucus membranes of the eyes and upper respiratory tract at lower concentrations. They can also be very irritating to the skin. Volcanic ash is also irritating for the mucus membranes of the eyes and upper respiratory tract. The smalles particles of volcanic ash can reach the alveoli of the lungs. Described are four examples of volcanic eruptions that have affected the health of Icelanders. The eruption of Laki volcanic fissure in 1783-1784 is the volcanic eruption that has caused the highest mortality and had the greatest effects on the well-being of Icelanders. Despite multiple volcanic eruptions during the last decades in Iceland mortality has been low and effects on human health have been limited, although studies on longterm effects are lacking. Studies on the effects of the Eyjafjallajökul eruption in 2010 on human health showed increased physical and mental symptoms, especially in those having respiratory disorders. The Directorate of Health in Iceland and other services have responded promptly to recurrent volcanic eruptions over the last few years and given detailed instructions on how to minimize the effects on the public health. Key words: volcanic eruptions, Iceland, volcanic ash, volcanic gases, health effects, mortality. Correspondence: Gunnar Guðmundsson, ggudmund@landspitali.is.

  7. Light front field theory: an advanced primer

    International Nuclear Information System (INIS)

    Martinovic, L.

    2007-01-01

    We present an elementary introduction to quantum field theory formulated in terms of Dirac's light front variables. In addition to general principles and methods, a few more specific topics and approaches based on the author's work will be discussed. Most of the discussion deals with massive two-dimensional models formulated in a finite spatial volume starting with a detailed comparison between quantization of massive free fields in the usual field theory and the light front (LF) quantization. We discuss basic properties such as relativistic invariance and causality. After the LF treatment of the soluble Federbush model, a LF approach to spontaneous symmetry breaking is explained and a simple gauge theory - the massive Schwinger model in various gauges is studied. A LF version of bosonization and the massive Thirring model are also discussed. A special chapter is devoted to the method of discretized light cone quantization and its application to calculations of the properties of quantum solitons. The problem of LF zero modes is illustrated with the example of the two/dimensional Yukawa model. Hamiltonian perturbation theory in the LF formulation is derived and applied to a few simple processes to demonstrate its advantages. As a byproduct, it is shown that the LF theory cannot be obtained as a 'light-like' limit of the usual field theory quantized on a initial space-like surface. A simple LF formulation of the Higgs mechanism is then given Since our intention was to provide a treatment of the light front quantization accessible to postgradual students, an effort was made to discuss most of the topics pedagogically and number of technical details and derivations are contained in the appendices (Author)

  8. Functional description of APS beamline front ends

    International Nuclear Information System (INIS)

    Kuzay, T.

    1993-02-01

    Traditional synchrotron sources were designed to produce bending magnet radiation and have proven to be an essential scientific tool. Currently, a new generation of synchrotron sources is being built that will be able to accommodate a large number of insertion device (ID) and high quality bending magnet (BM) sources. One example is the 7-GeV Advanced Photon Source (APS) now under construction at Argonne National Laboratory. The research and development effort at the APS is designed to fully develop the potential of this new generation of synchrotron sources. Of the 40 straight sections in the APS storage ring, 34 will be available for IDs. The remaining six sections are reserved for the storage ring hardware and diagnostics. Although the ring incorporates 80 BMs, only 40 of them can be used to extract radiation. The accelerator hardware shadows five of these 40 bending magnets, so the maximum number of BM sources on the lattice is 35. Generally, a photon beamline consists of four functional sections. The first section is the ID or the BM, which provides the radiation source. The second section, which is immediately outside the storage ring but inside a concrete shielding tunnel, is the front end, which is designed to control, define, and/or confine the x-ray beam. In the case of the APS, the front ends are designed to confine the photon beam. The third section, just outside the concrete shielding tunnel and on the experimental floor, is the first optics enclosure, which contains optics to filter and monochromatize the photon beam. The fourth section of a beamline consists of beam transports, additional optics, and experiment stations to do the scientific investigations. This document describes only the front ends of the APS beamlines

  9. Front panel human interface for FASTBUS

    International Nuclear Information System (INIS)

    Gustavson, D.B.; Holmes, T.L.; Paffrath, L.; Steffani, J.P.

    1980-01-01

    A human interface based on the Snoop diagnostic module has been designed to facilitate checkout of FASTBUS devices, diagnosis of system faults, and monitoring of system performance. This system, which is a generalization of the usual computer front panel or control console, includes logic analyzer functions, display and manual-control access to other modules, a microprocessor which allows the user to create and execute diagnostic programs and store them on a minifloppy disk, and a diagnostic network which allows remote console operation and coordination of information from multiple segments' Snoops

  10. Light-Front Holography, Light-Front Wavefunctions, and Novel QCD Phenomena

    DEFF Research Database (Denmark)

    Brodsky, S. J.; de Teramond, G. F.

    2012-01-01

    Light-front holography is one of the most remarkable features of the AdS/CFT correspondence. In spite of its present limitations, it provides important physical insights into the non-perturbative regime of QCD and its transition to the perturbative domain. This novel framework allows hadronic...... projected on the free Fock basis provides the complete set of valence and non-valence light-front Fock state wavefunctions Psi(n)/H(x(i), k(perpendicular to i), lambda(i)) which describe the hadron's momentum and spin distributions needed to compute the direct measures of hadron structure at the quark...

  11. Syntactic and FSP Aspects of Fronting as a Style Marker

    Directory of Open Access Journals (Sweden)

    Libuše Dušková

    2017-07-01

    Full Text Available The paper examines contextual and emphatic fronting in academic prose, fiction narrative and fiction dialogue in order to ascertain whether the types of fronting can serve as a style marker. The differences in the distribution and their effect on style are assumed to be connected with the respective FSP structures: in emphatic fronting the fronted element is the rheme, whereas in contextual fronting it is the diatheme. Hence emphatic fronting displays a prominent deviation from the basic distribution of communicative dynamism, whereas contextual fronting achieves agreement with it. As compared with the unmarked postverbal ordering, emphatic fronting intensifies the emphatic/emotional character of the content being expressed, which is a feature of speech, while contextual fronting serves as a direct link with what precedes, hence contributes to textual cohesion, which is a characteristic of academic prose, with fiction narrative presumably occupying an intermediate position. The results of the study show more types of fronting with diversified structures and less clear-cut relations between the types of frontings and the examined text sorts.

  12. Obsidian hydration dating of volcanic events

    Science.gov (United States)

    Friedman, I.; Obradovich, J.

    1981-01-01

    Obsidian hydration dating of volcanic events had been compared with ages of the same events determined by the 14C and KAr methods at several localities. The localities, ranging in age from 1200 to over 1 million yr, include Newberry Craters, Oregon; Coso Hot Springs, California; Salton Sea, California; Yellowstone National Park, Wyoming; and Mineral Range, Utah. In most cases the agreement is quite good. A number of factors including volcanic glass composition and exposuretemperature history must be known in order to relate hydration thickness to age. The effect of composition can be determined from chemical analysis or the refractive index of the glass. Exposure-temperature history requires a number of considerations enumerated in this paper. ?? 1981.

  13. Volcanic Origin of Alkali Halides on Io

    Science.gov (United States)

    Schaefer, L.; Fegley, B., Jr.

    2003-01-01

    The recent observation of NaCl (gas) on Io confirms our earlier prediction that NaCl is produced volcanically. Here we extend our calculations by modeling thermochemical equilibrium of O, S, Li, Na, K, Rb, Cs, F, Cl, Br, and I as a function of temperature and pressure in a Pele-like volcanic gas with O/S/Na/Cl/K = 1.518/1/0.05/0.04/0.005 and CI chondritic ratios of the other (as yet unobserved) alkalis and halogens. For reference, the nominal temperature and pressure for Pele is 1760 plus or minus 210 K and 0.01 bars based on Galileo data and modeling.

  14. Volcanic ash impacts on critical infrastructure

    Science.gov (United States)

    Wilson, Thomas M.; Stewart, Carol; Sword-Daniels, Victoria; Leonard, Graham S.; Johnston, David M.; Cole, Jim W.; Wardman, Johnny; Wilson, Grant; Barnard, Scott T.

    2012-01-01

    Volcanic eruptions can produce a wide range of hazards. Although phenomena such as pyroclastic flows and surges, sector collapses, lahars and ballistic blocks are the most destructive and dangerous, volcanic ash is by far the most widely distributed eruption product. Although ash falls rarely endanger human life directly, threats to public health and disruption to critical infrastructure services, aviation and primary production can lead to significant societal impacts. Even relatively small eruptions can cause widespread disruption, damage and economic loss. Volcanic eruptions are, in general, infrequent and somewhat exotic occurrences, and consequently in many parts of the world, the management of critical infrastructure during volcanic crises can be improved with greater knowledge of the likely impacts. This article presents an overview of volcanic ash impacts on critical infrastructure, other than aviation and fuel supply, illustrated by findings from impact assessment reconnaissance trips carried out to a wide range of locations worldwide by our international research group and local collaborators. ‘Critical infrastructure’ includes those assets, frequently taken for granted, which are essential for the functioning of a society and economy. Electricity networks are very vulnerable to disruption from volcanic ash falls. This is particularly the case when fine ash is erupted because it has a greater tendency to adhere to line and substation insulators, where it can cause flashover (unintended electrical discharge) which can in turn cause widespread and disruptive outages. Weather conditions are a major determinant of flashover risk. Dry ash is not conductive, and heavy rain will wash ash from insulators, but light rain/mist will mobilise readily-soluble salts on the surface of the ash grains and lower the ash layer’s resistivity. Wet ash is also heavier than dry ash, increasing the risk of line breakage or tower/pole collapse. Particular issues for water

  15. Magnetic properties of frictional volcanic materials

    Science.gov (United States)

    Kendrick, Jackie E.; Lavallée, Yan; Biggin, Andrew; Ferk, Annika; Leonhardt, Roman

    2015-04-01

    During dome-building volcanic eruptions, highly viscous magma extends through the upper conduit in a solid-like state. The outer margins of the magma column accommodate the majority of the strain, while the bulk of the magma is able to extrude, largely undeformed, to produce magma spines. Spine extrusion is often characterised by the emission of repetitive seismicity, produced in the upper <1 km by magma failure and slip at the conduit margins. The rheology of the magma controls the depth at which fracture can occur, while the frictional properties of the magma are important in controlling subsequent marginal slip processes. Upon extrusion, spines are coated by a carapace of volcanic fault rocks which provide insights into the deeper conduit processes. Frictional samples from magma spines at Mount St. Helens (USA), Soufriere Hills (Montserrat) and Mount Unzen (Japan) have been examined using structural, thermal and magnetic analyses to reveal a history of comminution, frictional heating, melting and cooling to form volcanic pseudotachylyte. Pseudotachylyte has rarely been noted in volcanic materials, and the recent observation of its syn-eruptive formation in dome-building volcanoes was unprecedented. The uniquely high thermal conditions of volcanic environments means that frictional melt remains at elevated temperatures for longer than usual, causing slow crystallisation, preventing the development of some signature "quench" characteristics. As such, rock-magnetic tests have proven to be some of the most useful tools in distinguishing pseudotachylytes from their andesite/ dacite hosts. In volcanic pseudotachylyte the mass normalised natural remanent magnetisation (NRM) when further normalised with the concentration dependent saturation remanence (Mrs) was found to be higher than the host rock. Remanence carriers are defined as low coercive materials across all samples, and while the remanence of the host rock displays similarities to an anhysteretic remanent

  16. The scaling of experiments on volcanic systems

    Directory of Open Access Journals (Sweden)

    Olivier eMERLE

    2015-06-01

    Full Text Available In this article, the basic principles of the scaling procedure are first reviewed by a presentation of scale factors. Then, taking an idealized example of a brittle volcanic cone intruded by a viscous magma, the way to choose appropriate analogue materials for both the brittle and ductile parts of the cone is explained by the use of model ratios. Lines of similarity are described to show that an experiment simulates a range of physical processes instead of a unique natural case. The pi theorem is presented as an alternative scaling procedure and discussed through the same idealized example to make the comparison with the model ratio procedure. The appropriateness of the use of gelatin as analogue material for simulating dyke formation is investigated. Finally, the scaling of some particular experiments such as pyroclastic flows or volcanic explosions is briefly presented to show the diversity of scaling procedures in volcanology.

  17. Volcanic emission of radionuclides and magma dynamics

    International Nuclear Information System (INIS)

    Lambert, G.; Le Cloarec, M.F.; Ardouin, B.; Le Roulley, J.C.

    1985-01-01

    210 Pb, 210 Bi and 210 Po, the last decay products of the 238 U series, are highly enriched in volcanic plumes, relative to the magma composition. Moreover this enrichment varies over time and from volcano to volcano. A model is proposed to describe 8 years of measurements of Mt. Etna gaseous emissions. The lead and bismuth coefficients of partition between gaseous and condensated phases in the magma are determined by comparing their concentrations in lava flows and condensated volatiles. In the case of volatile radionuclides, an escaping time is calculated which appears to be related to the volcanic activity. Finally, it is shown that that magma which is degassing can already be partly degassed; it should be considered as a mixture of a few to 50% of deep non-degassed magma with a well degassed superficial magma cell. (orig.)

  18. Seasonal variations of volcanic eruption frequencies

    Science.gov (United States)

    Stothers, Richard B.

    1989-01-01

    Do volcanic eruptions have a tendency to occur more frequently in the months of May and June? Some past evidence suggests that they do. The present study, based on the new eruption catalog of Simkin et al.(1981), investigates the monthly statistics of the largest eruptions, grouped according to explosive magnitude, geographical latitude, and year. At the 2-delta level, no month-to-month variations in eruption frequency are found to be statistically significant. Examination of previously published month-to-month variations suggests that they, too, are not statistically significant. It is concluded that volcanism, at least averaged over large portions of the globe, is probably not periodic on a seasonal or annual time scale.

  19. Coping with volcanic hazards; a global perspective

    Science.gov (United States)

    Tilling, R.I.

    1990-01-01

    Compared to some other natural hazards-such as floods, storms, earthquakes, landslides- volcanic hazards strike infrequently. However, in populated areas , even very small eruptions can wreak havoc and cause widespread devastation. For example, the 13 November 1985 eruption of Nevado del Ruiz in Colombia ejected only about 3 percent of the volume of ash produced during the 18 May 1980 eruption of Mount St. Helens. Yet, the mudflows triggered by this tiny eruption killed more than 25,000 people.

  20. Feasibility study on volcanic power generation system

    Energy Technology Data Exchange (ETDEWEB)

    None

    1977-07-01

    Investigations were carried out to determine the feasibility of volcanic power generation on Satsuma Io Island. Earthquakes were studied, as were the eruptions of subaerial and submarine hot springs. Hydrothermal rock alteration was studied and electrical surveys were made. General geophysical surveying was performed with thermocameras and radiation monitoring equipment. In particular, the Toyoba mine was studied, both with respect to its hot spring and its subsurface temperatures.

  1. 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.

  2. Geothermal and volcanism in west Java

    Science.gov (United States)

    Setiawan, I.; Indarto, S.; Sudarsono; Fauzi I, A.; Yuliyanti, A.; Lintjewas, L.; Alkausar, A.; Jakah

    2018-02-01

    Indonesian active volcanoes extend from Sumatra, Jawa, Bali, Lombok, Flores, North Sulawesi, and Halmahera. The volcanic arc hosts 276 volcanoes with 29 GWe of geothermal resources. Considering a wide distribution of geothermal potency, geothermal research is very important to be carried out especially to tackle high energy demand in Indonesia as an alternative energy sources aside from fossil fuel. Geothermal potency associated with volcanoes-hosted in West Java can be found in the West Java segment of Sunda Arc that is parallel with the subduction. The subduction of Indo-Australian oceanic plate beneath the Eurasian continental plate results in various volcanic products in a wide range of geochemical and mineralogical characteristics. The geochemical and mineralogical characteristics of volcanic and magmatic rocks associated with geothermal systems are ill-defined. Comprehensive study of geochemical signatures, mineralogical properties, and isotopes analysis might lead to the understanding of how large geothermal fields are found in West Java compared to ones in Central and East Java. The result can also provoke some valuable impacts on Java tectonic evolution and can suggest the key information for geothermal exploration enhancement.

  3. Low-pressure evolution of arc magmas in thickened crust: The San Pedro-Linzor volcanic chain, Central Andes, Northern Chile

    Science.gov (United States)

    Godoy, Benigno; Wörner, Gerhard; Kojima, Shoji; Aguilera, Felipe; Simon, Klaus; Hartmann, Gerald

    2014-07-01

    Magmatism at Andean Central Volcanic Zone (CVZ), or Central Andes, is strongly influenced by differentiation and assimilation at high pressures that occurred at lower levels of the thick continental crust. This is typically shown by high light to heavy rare earth element ratios (LREE/HREE) of the erupted lavas at this volcanic zone. Increase of these ratios with time is interpreted as a change to magma evolution in the presence of garnet during evolution of Central Andes. Such geochemical signals could be introduced into the magmas be high-pressure fractionation with garnet on the liquidus and/or assimilation from crustal rocks with a garnet-bearing residue. However, lavas erupted at San Pedro-Linzor volcanic chain show no evidence of garnet fractionation in their trace element patterns. This volcanic chain is located in the active volcanic arc, between 22°00‧S and 22°30‧S, over a continental crust ˜70 km thick. Sampled lavas show Sr/Y and Sm/Yb ratios Chile. We relate our geochemical observations to shallow crustal evolution of primitive magmas involving a high degree of assimilation of upper continental crust. We emphasize that low pressure AFC- (Assimilation Fractional Crystallization) type evolution of the San Pedro-Linzor volcanic chain reflects storage, fractionation, and contamination of mantle-derived magmas at the upper felsic crust (<40 km depth). The ascent of mantle-derived magmas to mid-crustal levels is related with the extensional regime that has existed in this zone of arc-front offset since Late-Miocene age, and the relatively thin portion of mafic lower crust observed below the volcanic chain.

  4. Internal waves and temperature fronts on slopes

    Directory of Open Access Journals (Sweden)

    S. A. Thorpe

    Full Text Available Time series measurements from an array of temperature miniloggers in a line at constant depth along the sloping boundary of a lake are used to describe the `internal surf zone' where internal waves interact with the sloping boundary. More small positive temperature time derivatives are recorded than negative, but there are more large negative values than positive, giving the overall distribution of temperature time derivatives a small negative skewness. This is consistent with the internal wave dynamics; fronts form during the up-slope phase of the motion, bringing cold water up the slope, and the return flow may become unstable, leading to small advecting billows and weak warm fronts. The data are analysed to detect `events', periods in which the temperature derivatives exceed a set threshold. The speed and distance travelled by `events' are described. The motion along the slope may be a consequence of (a instabilities advected by the flow (b internal waves propagating along-slope or (c internal waves approaching the slope from oblique directions. The propagation of several of the observed 'events' can only be explained by (c, evidence that the internal surf zone has some, but possibly not all, the characteristics of the conventional 'surface wave' surf zone, with waves steepening as they approach the slope at oblique angles.

    Key words. Oceanography: general (benthic boundary layers; limnology, Oceanography: physical (internal and inertial waves

  5. Biomechanics of front and back squat exercises

    International Nuclear Information System (INIS)

    Braidot, A A; Brusa, M H; Lestussi, F E; Parera, G P

    2007-01-01

    Squat constitutes one of the most popular exercises to strengthen the muscles of the lower limbs. It is considered one of the most widely spread exercises for muscle sport training and is part of the competition movements comprised within olympic weight-lifting. In physical rehabilitation, squats are used for muscular recovery after different injuries of the lower limbs, especially the knee. In previous anterior cruciate ligament injuries, the mini-squats are generally used, in a knee flexion motion range from 0 deg. to 50 deg. because in this range the shear forces, the tibiofemoral and patellofemoral compression forces decrease related to greater flexion angles. The aim of this work is to make a comparative bidimensional study of the kinematic and dynamic variables of the excecution of the parallel squat exercise with the front and back bar. It is observed in the knee a better development of energy with the front bar, allowing a better muscular exercise with the same load. The mean power absorbed by the hip with the back bar is considerably greater, associated to the speed of the gesture

  6. Travelling fronts in stochastic Stokes’ drifts

    KAUST Repository

    Blanchet, Adrien

    2008-10-01

    By analytical methods we study the large time properties of the solution of a simple one-dimensional model of stochastic Stokes\\' drift. Semi-explicit formulae allow us to characterize the behaviour of the solutions and compute global quantities such as the asymptotic speed of the center of mass or the effective diffusion coefficient. Using an equivalent tilted ratchet model, we observe that the speed of the center of mass converges exponentially to its limiting value. A diffuse, oscillating front attached to the center of mass appears. The description of the front is given using an asymptotic expansion. The asymptotic solution attracts all solutions at an algebraic rate which is determined by the effective diffusion coefficient. The proof relies on an entropy estimate based on homogenized logarithmic Sobolev inequalities. In the travelling frame, the macroscopic profile obeys to an isotropic diffusion. Compared with the original diffusion, diffusion is enhanced or reduced, depending on the regime. At least in the limit cases, the rate of convergence to the effective profile is always decreased. All these considerations allow us to define a notion of efficiency for coherent transport, characterized by a dimensionless number, which is illustrated on two simple examples of travelling potentials with a sinusoidal shape in the first case, and a sawtooth shape in the second case. © 2008 Elsevier B.V. All rights reserved.

  7. Biomechanics of front and back squat exercises

    Energy Technology Data Exchange (ETDEWEB)

    Braidot, A A [Laboratorio de Biomecanica FI-UNER. Ruta 11 Km 10 Oro Verde Entre Rios (Argentina); Brusa, M H [Laboratorio de Biomecanica FI-UNER. Ruta 11 Km 10 Oro Verde Entre Rios (Argentina); Lestussi, F E [Laboratorio de Biomecanica FI-UNER. Ruta 11 Km 10 Oro Verde Entre Rios (Argentina); Parera, G P [Licenciatura en KinesiologIa y FisiatrIa Universidad Abierta Interamericana. Sede Regional Rosario (Argentina)

    2007-11-15

    Squat constitutes one of the most popular exercises to strengthen the muscles of the lower limbs. It is considered one of the most widely spread exercises for muscle sport training and is part of the competition movements comprised within olympic weight-lifting. In physical rehabilitation, squats are used for muscular recovery after different injuries of the lower limbs, especially the knee. In previous anterior cruciate ligament injuries, the mini-squats are generally used, in a knee flexion motion range from 0 deg. to 50 deg. because in this range the shear forces, the tibiofemoral and patellofemoral compression forces decrease related to greater flexion angles. The aim of this work is to make a comparative bidimensional study of the kinematic and dynamic variables of the excecution of the parallel squat exercise with the front and back bar. It is observed in the knee a better development of energy with the front bar, allowing a better muscular exercise with the same load. The mean power absorbed by the hip with the back bar is considerably greater, associated to the speed of the gesture.

  8. Biomechanics of front and back squat exercises

    Science.gov (United States)

    Braidot, A. A.; Brusa, M. H.; Lestussi, F. E.; Parera, G. P.

    2007-11-01

    Squat constitutes one of the most popular exercises to strengthen the muscles of the lower limbs. It is considered one of the most widely spread exercises for muscle sport training and is part of the competition movements comprised within olympic weight-lifting. In physical rehabilitation, squats are used for muscular recovery after different injuries of the lower limbs, especially the knee. In previous anterior cruciate ligament injuries, the mini-squats are generally used, in a knee flexion motion range from 0° to 50° because in this range the shear forces, the tibiofemoral and patellofemoral compression forces decrease related to greater flexion angles. The aim of this work is to make a comparative bidimensional study of the kinematic and dynamic variables of the excecution of the parallel squat exercise with the front and back bar. It is observed in the knee a better development of energy with the front bar, allowing a better muscular exercise with the same load. The mean power absorbed by the hip with the back bar is considerably greater, associated to the speed of the gesture.

  9. Tracer filamentation at an unstable ocean front

    Science.gov (United States)

    Feng, Yen Chia; Mahadevan, Amala; Thiffeault, Jean-Luc; Yecko, Philip

    2017-11-01

    A front, where two bodies of ocean water with different physical properties meet, can become unstable and lead to a flow with high strain rate and vorticity. Phytoplankton and other oceanic tracers are stirred into filaments by such flow fields, as can often be seen in satellite imagery. The stretching and folding of a tracer by a two-dimensional flow field has been well studied. In the ocean, however, the vertical shear of horizontal velocity is typically two orders of magnitude larger than the horizontal velocity gradient. Theoretical calculations show that vertical shear alters the way in which horizontal strain affects the tracer, resulting in thin, sloping structures in the tracer field. Using a non-hydrostatic ocean model of an unstable ocean front, we simulate tracer filamentation to identify the effect of vertical shear on the deformation of the tracer. In a complementary laboratory experiment, we generate a simple, vertically sheared strain flow and use dye and particle image velocimetry to quantify the filamentary structures in terms of the strain and shear. We identify how vertical shear alters the tracer filaments and infer how the evolution of tracers in the ocean will differ from the idealized two-dimensional paradigm. Support of NSF DMS-1418956 is acknowledged.

  10. The ALICE TPC front end electronics

    CERN Document Server

    Musa, L; Bialas, N; Bramm, R; Campagnolo, R; Engster, Claude; Formenti, F; Bonnes, U; Esteve-Bosch, R; Frankenfeld, Ulrich; Glässel, P; Gonzales, C; Gustafsson, Hans Åke; Jiménez, A; Junique, A; Lien, J; Lindenstruth, V; Mota, B; Braun-Munzinger, P; Oeschler, H; Österman, L; Renfordt, R E; Ruschmann, G; Röhrich, D; Schmidt, H R; Stachel, J; Soltveit, A K; Ullaland, K

    2004-01-01

    In this paper we present the front end electronics for the time projection chamber (TPC) of the ALICE experiment. The system, which consists of about 570000 channels, is based on two basic units: (a) an analogue ASIC (PASA) that incorporates the shaping-amplifier circuits for 16 channels; (b) a mixed-signal ASIC (ALTRO) that integrates 16 channels, each consisting of a 10-bit 25-MSPS ADC, the baseline subtraction, tail cancellation filter, zero suppression and multi-event buffer. The complete readout chain is contained in front end cards (FEC), with 128 channels each, connected to the detector by means of capton cables. A number of FECs (up to 25) are controlled by a readout control unit (RCU), which interfaces the FECs to the data acquisition (DAQ), the trigger, and the detector control system (DCS) . A function of the final electronics (1024 channels) has been characterized in a test that incorporates a prototype of the ALICE TPC as well as many other components of the final set-up. The tests show that the ...

  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. 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.

  13. The global chemical systematics of arc front stratovolcanoes: Evaluating the role of crustal processes

    Science.gov (United States)

    Turner, Stephen J.; Langmuir, Charles H.

    2015-07-01

    Petrogenetic models for convergent margins should be consistent with the global systematics of convergent margin volcanic compositions. A newly developed tool for compiling and screening data from the GEOROC database was used to generate a global dataset of whole rock chemical analyses from arc front stratovolcano samples. Data from 227 volcanoes within 31 volcanic arc segments were first averaged by volcano and then by arc to explore global systematics. Three different methods of data normalization produce consistent results that persist across a wide range of Mg# [Mg# =Mg / (Mg +Fe) ]. Remarkably coherent systematics are present among major and trace element concentrations and ratios, with the exception of three arcs influenced by mantle plumes and Peru/N. Chile, which is built on exceptionally thick crust. Chemical parameters also correlate with the thickness of the overlying arc crust. In addition to previously established correlations of Na6.0 with Ca6.0 and crustal thickness, correlations are observed among major elements, trace elements, and trace element ratios (e.g. La/Yb, Dy/Yb, Zr/Sm, Zr/Ti). Positive correlations include "fluid mobile," "high field strength," and "large ion lithophile" element groups, with concentrations that vary by a factor of five in all groups. Incompatible element enrichments also correlate well with crustal thickness, with the greatest enrichment found at arcs with the thickest crust. Intra-crustal processes, however, do not reproduce the global variations. High pressure fractionation produces intermediate magmas enriched in aluminum, but such magmas are rare. Furthermore, differences among magma compositions at various volcanic arcs persist from primitive to evolved compositions, which is inconsistent with the possibility that global variations are produced by crystal fractionation at any pressure. Linear relationships among elements appear to be consistent with mixing between depleted primary magma and an enriched contaminant

  14. Spatially hybrid computations for streamer discharges with generic features of pulled fronts: I. Planar fronts

    International Nuclear Information System (INIS)

    Li Chao; Ebert, Ute; Hundsdorfer, Willem

    2010-01-01

    Streamers are the first stage of sparks and lightning; they grow due to a strongly enhanced electric field at their tips; this field is created by a thin curved space charge layer. These multiple scales are already challenging when the electrons are approximated by densities. However, electron density fluctuations in the leading edge of the front and non-thermal stretched tails of the electron energy distribution (as a cause of X-ray emissions) require a particle model to follow the electron motion. But present computers cannot deal with all electrons in a fully developed streamer. Therefore, super-particle have to be introduced, which leads to wrong statistics and numerical artifacts. The method of choice is a hybrid computation in space where individual electrons are followed in the region of high electric field and low density while the bulk of the electrons is approximated by densities (or fluids). We here develop the hybrid coupling for planar fronts. First, to obtain a consistent flux at the interface between particle and fluid model in the hybrid computation, the widely used classical fluid model is replaced by an extended fluid model. Then the coupling algorithm and the numerical implementation of the spatially hybrid model are presented in detail, in particular, the position of the model interface and the construction of the buffer region. The method carries generic features of pulled fronts that can be applied to similar problems like large deviations in the leading edge of population fronts, etc.

  15. Volcanic styles at Alba Patera, Mars: implications of lava flow morphology to the volcanic history

    International Nuclear Information System (INIS)

    Schneeberger, D.M.; Pieri, D.C.

    1988-01-01

    Alba Patera presents styles of volcanism that are unique to Mars. Its very low profile, large areal extent, unusually long and voluminous lava flows, and circumferential graben make it among Mars' most interesting volcanic features. Clues to Alba's volcanic history are preserved in its morphology and stratigraphy. Understanding the relationship of lava flow morphology to emplacement processes should enable estimates of viscosity, effusion rate, and gross composition to be made. Lava flows, with dimensions considered enormous by terrestrial standards, account for a major portion of the exposed surface of Alba Patera. These flows exhibit a range of morphologies. While most previous works have focused on the planimetric characteristics, attention was drawn to the important morphological attributes, paying particular attention to what the features suggest about the emplacement process

  16. Geophysical expression of caldera related volcanism, structures and mineralization in the McDermitt volcanic field

    Science.gov (United States)

    Rytuba, J. J.; Blakely, R. J.; Moring, B.; Miller, R.

    2013-12-01

    The High Rock, Lake Owyhee, and McDermitt volcanic fields, consisting of regionally extensive ash flow tuffs and associated calderas, developed in NW Nevada and SE Oregon following eruption of the ca. 16.7 Ma Steens flood basalt. The first ash flow, the Tuff of Oregon Canyon, erupted from the McDermitt volcanic field at 16.5Ma. It is chemically zoned from peralkaline rhyolite to dacite with trace element ratios that distinguish it from other ash flow tuffs. The source caldera, based on tuff distribution, thickness, and size of lithic fragments, is in the area in which the McDermitt caldera (16.3 Ma) subsequently formed. Gravity and magnetic anomalies are associated with some but not all of the calderas. The White Horse caldera (15.6 Ma), the youngest caldera in the McDermitt volcanic field has the best geophysical expression, with both aeromagnetic and gravity lows coinciding with the caldera. Detailed aeromagnetic and gravity surveys of the McDermitt caldera, combined with geology and radiometric surveys, provides insight into the complexities of caldera collapse, resurgence, post collapse volcanism, and hydrothermal mineralization. The McDermitt caldera is among the most mineralized calderas in the world, whereas other calderas in these three Mid Miocene volcanic fields do not contain important hydrothermal ore deposits, despite having similar age and chemistry. The McDermitt caldera is host to Hg, U, and Li deposits and potentially significant resources of Ga, Sb, and REE. The geophysical data indicate that post-caldera collapse intrusions were important in formation of the hydrothermal systems. An aeromagnetic low along the E caldera margin reflects an intrusion at a depth of 2 km associated with the near-surface McDermitt-hot-spring-type Hg-Sb deposit, and the deeper level, high-sulfidation Ga-REE occurrence. The Li deposits on the W side of the caldera are associated with a series of low amplitude, small diameter aeromagnetic anomalies that form a continuous

  17. Using Volcanic Lightning Measurements to Discern Variations in Explosive Volcanic Activity

    Science.gov (United States)

    Behnke, S. A.; Thomas, R. J.; McNutt, S. R.; Edens, H. E.; Krehbiel, P. R.; Rison, W.

    2013-12-01

    VHF observations of volcanic lightning have been made during the recent eruptions of Augustine Volcano (2006, Alaska, USA), Redoubt Volcano (2009, Alaska, USA), and Eyjafjallajökull (2010, Iceland). These show that electrical activity occurs both on small scales at the vent of the volcano, concurrent with an eruptive event and on large scales throughout the eruption column during and subsequent to an eruptive event. The small-scale discharges at the vent of the volcano are often referred to as 'vent discharges' and are on the order of 10-100 meters in length and occur at rates on the order of 1000 per second. The high rate of vent discharges produces a distinct VHF signature that is sometimes referred to as 'continuous RF' radiation. VHF radiation from vent discharges has been observed at sensors placed as far as 100 km from the volcano. VHF and infrasound measurements have shown that vent discharges occur simultaneously with the onset of eruption, making their detection an unambiguous indicator of explosive volcanic activity. The fact that vent discharges are observed concurrent with explosive volcanic activity indicates that volcanic ejecta are charged upon eruption. VHF observations have shown that the intensity of vent discharges varies between eruptive events, suggesting that fluctuations in eruptive processes affect the electrification processes giving rise to vent discharges. These fluctuations may be variations in eruptive vigor or variations in the type of eruption; however, the data obtained so far do not show a clear relationship between eruption parameters and the intensity or occurrence of vent discharges. Further study is needed to clarify the link between vent discharges and eruptive behavior, such as more detailed lightning observations concurrent with tephra measurements and other measures of eruptive strength. Observations of vent discharges, and volcanic lightning observations in general, are a valuable tool for volcano monitoring, providing a

  18. Supervolcanoes within an ancient volcanic province in Arabia Terra, Mars.

    Science.gov (United States)

    Michalski, Joseph R; Bleacher, Jacob E

    2013-10-03

    Several irregularly shaped craters located within Arabia Terra, Mars, represent a new type of highland volcanic construct and together constitute a previously unrecognized Martian igneous province. Similar to terrestrial supervolcanoes, these low-relief paterae possess a range of geomorphic features related to structural collapse, effusive volcanism and explosive eruptions. Extruded lavas contributed to the formation of enigmatic highland ridged plains in Arabia Terra. Outgassed sulphur and erupted fine-grained pyroclastics from these calderas probably fed the formation of altered, layered sedimentary rocks and fretted terrain found throughout the equatorial region. The discovery of a new type of volcanic construct in the Arabia volcanic province fundamentally changes the picture of ancient volcanism and climate evolution on Mars. Other eroded topographic basins in the ancient Martian highlands that have been dismissed as degraded impact craters should be reconsidered as possible volcanic constructs formed in an early phase of widespread, disseminated magmatism on Mars.

  19. Volcanic flows versus water- and ice-related outburst deposits in eastern Hellas: A comparison

    Science.gov (United States)

    Voelker, M.; Hauber, E.; Stephan, K.; Jaumann, R.

    2018-06-01

    Hellas Planitia is one of the major topographic sinks on Mars for the deposition of any kind of sediments. We report on our observations of sheet deposits in the eastern part of the basin that are apparently related to the Dao Vallis outflow channel. The deposits have lobate flow fronts and a thickness of a few decameters. Despite their generally smooth surface, some distinctive textures and patterns can be identified, such as longitudinal lineations, distributive channels, and polygons. We compared these deposits to other sheet deposits on Mars and tested three hypotheses of their origin: volcanic flows as well as water- and ice-related mass wastings. Despite some similarities to volcanic sheet flows on Mars, we found several morphological characteristics that are not known for sheet lava flows; for example conically arranged lineations and channel systems very similar to fluvial incisions. We also reject an ice-related formation similar to terrestrial rock-ice avalanches, as there is no sufficient relief energy to explain their extent and location. A water-related origin appears most consistent with our observations, and we favor an emplacement by fluvially-driven mass wasting processes, e.g., debris flows. Assuming a water-related origin, we calculated the amount of water that would be required to deposit such large sedimentary bodies for different flow types. Our calculations show a large range of possible water volumes, from 64 to 2,042 km³, depending on the specific flow mechanism. The close link to Dao Vallis makes these deposits a unique place to study the deposition of outflow channel sediments, as the deposits of other outflow channels on Mars, such as those around Chryse Planitia, are mostly buried by younger sediments and volcanic flows.

  20. Vector mesons on the light front

    International Nuclear Information System (INIS)

    Naito, K.; Maedan, S.; Itakura, K.

    2004-01-01

    We apply the light-front quantization to the Nambu-Jona-Lasinio model with the vector interaction, and compute vector meson's mass and light-cone wavefunction in the large N limit. Following the same procedure as in the previous analyses for scalar and pseudo-scalar mesons, we derive the bound-state equations of a qq-bar system in the vector channel. We include the lowest order effects of the vector interaction. The resulting transverse and longitudinal components of the bound-state equation look different from each other. But eventually after imposing an appropriate cutoff, one finds these two are identical, giving the same mass and the same (spin-independent) light-cone wavefunction. Mass of the vector meson decreases as one increases the strength of the vector interaction

  1. Light-front quantization of field theory

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Prem P. [Universidade do Estado, Rio de Janeiro, RJ (Brazil). Inst. de Fisica]|[Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)

    1996-07-01

    Some basic topics in Light-Front (LF) quantized field theory are reviewed. Poincare algebra and the LF spin operator are discussed. The local scalar field theory of the conventional framework is shown to correspond to a non-local Hamiltonian theory on the LF in view of the constraint equations on the phase space, which relate the bosonic condensates to the non-zero modes. This new ingredient is useful to describe the spontaneous symmetry breaking on the LF. The instability of the symmetric phase in two dimensional scalar theory when the coupling constant grows is shown in the LF theory renormalized to one loop order. Chern-Simons gauge theory, regarded to describe excitations with fractional statistics, is quantized in the light-cone gauge and a simple LF Hamiltonian obtained which may allow us to construct renormalized theory of anyons. (author). 20 refs.

  2. Light-front quantization of field theory

    International Nuclear Information System (INIS)

    Srivastava, Prem P.

    1996-07-01

    Some basic topics in Light-Front (LF) quantized field theory are reviewed. Poincare algebra and the LF spin operator are discussed. The local scalar field theory of the conventional framework is shown to correspond to a non-local Hamiltonian theory on the LF in view of the constraint equations on the phase space, which relate the bosonic condensates to the non-zero modes. This new ingredient is useful to describe the spontaneous symmetry breaking on the LF. The instability of the symmetric phase in two dimensional scalar theory when the coupling constant grows is shown in the LF theory renormalized to one loop order. Chern-Simons gauge theory, regarded to describe excitations with fractional statistics, is quantized in the light-cone gauge and a simple LF Hamiltonian obtained which may allow us to construct renormalized theory of anyons. (author). 20 refs

  3. The CMS Tracker Readout Front End Driver

    CERN Document Server

    Foudas, C.; Ballard, D.; Church, I.; Corrin, E.; Coughlan, J.A.; Day, C.P.; Freeman, E.J.; Fulcher, J.; Gannon, W.J.F.; Hall, G.; Halsall, R.N.J.; Iles, G.; Jones, J.; Leaver, J.; Noy, M.; Pearson, M.; Raymond, M.; Reid, I.; Rogers, G.; Salisbury, J.; Taghavi, S.; Tomalin, I.R.; Zorba, O.

    2004-01-01

    The Front End Driver, FED, is a 9U 400mm VME64x card designed for reading out the Compact Muon Solenoid, CMS, silicon tracker signals transmitted by the APV25 analogue pipeline Application Specific Integrated Circuits. The FED receives the signals via 96 optical fibers at a total input rate of 3.4 GB/sec. The signals are digitized and processed by applying algorithms for pedestal and common mode noise subtraction. Algorithms that search for clusters of hits are used to further reduce the input rate. Only the cluster data along with trigger information of the event are transmitted to the CMS data acquisition system using the S-LINK64 protocol at a maximum rate of 400 MB/sec. All data processing algorithms on the FED are executed in large on-board Field Programmable Gate Arrays. Results on the design, performance, testing and quality control of the FED are presented and discussed.

  4. Light-Front Holography, Light-Front Wavefunctions, and Novel QCD Phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins; de Teramond, Guy F.; /Costa Rica U.

    2012-02-16

    Light-Front Holography is one of the most remarkable features of the AdS/CFT correspondence. In spite of its present limitations it provides important physical insights into the nonperturbative regime of QCD and its transition to the perturbative domain. This novel framework allows hadronic amplitudes in a higher dimensional anti-de Sitter (AdS) space to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The model leads to an effective confining light-front QCD Hamiltonian and a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound-state wavefunctions, and thus the fall-off as a function of the invariant mass of the constituents. The soft-wall holographic model modified by a positive-sign dilaton metric, leads to a remarkable one-parameter description of nonperturbative hadron dynamics - a semi-classical frame-independent first approximation to the spectra and light-front wavefunctions of meson and baryons. The model predicts a Regge spectrum of linear trajectories with the same slope in the leading orbital angular momentum L of hadrons and the radial quantum number n. The hadron eigensolutions projected on the free Fock basis provides the complete set of valence and non-valence light-front Fock state wavefunctions {Psi}{sub n/H} (x{sub i}, k{sub {perpendicular}i}, {lambda}{sub i}) which describe the hadron's momentum and spin distributions needed to compute the direct measures of hadron structure at the quark and gluon level, such as elastic and transition form factors, distribution amplitudes, structure functions, generalized parton distributions and transverse

  5. Volcanism Studies: Final Report for the Yucca Mountain Project

    International Nuclear Information System (INIS)

    Crowe, Bruce M.; Perry, Frank V.; Valentine, Greg A.; Bowker, Lynn M.

    1998-01-01

    This report synthesizes the results of volcanism studies conducted by scientists at the Los Alamos National Laboratory and collaborating institutions on behalf of the Department of Energy's Yucca Mountain Project. An assessment of the risk of future volcanic activity is one of many site characterization studies that must be completed to evaluate the Yucca Mountain site for potential long-term storage of high-level radioactive waste. The presence of several basaltic volcanic centers in the Yucca Mountain region of Pliocene and Quaternary age indicates that there is a finite risk of a future volcanic event occurring during the 10,000-year isolation period of a potential repository. Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The risk of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Future volcanic events cannot be predicted with certainty but instead are estimated using formal methods of probabilistic volcanic hazard assessment (PVHA). Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The distribution, eruptive history, and geochronology of Plio-Quaternary basalt centers are described by individual center emphasizing the younger postcaldera basalt ( than about 7 x 10 -8 events yr -1 . Simple probability estimates are used to assess possible implications of not drilling aeromagnetic anomalies in the Amargosa Valley. The sensitivity of the disruption probability to the location of northeast boundaries of volcanic zones near the Yucca Mountain sit

  6. Sr isotopes at Copahue Volcanic Center, Neuquen, Argentina: Preliminary report

    International Nuclear Information System (INIS)

    Linares, E.; Ostera, H.A.; Cagnoni, M.C

    2001-01-01

    The Copahue Volcanic Center is located in the Cordillera Principal, at 38 L.S., in the Argentina- Chilean border. Detailed geological, geochronological and structural studies were carried out during the last decade (Pesce, 1989; Delpino y Bermudez, 1993; Linares et al., 1995, 1999; Folguera y Ramos, 2000; among others). We present Sr isotopes data on the main units of the Volcanic Center, coupled with a major element geochemistry, to constrain the evolution of the volcanic center (au)

  7. Eocene volcanism and the origin of horizon A

    Science.gov (United States)

    Gibson, T.G.; Towe, K.M.

    1971-01-01

    A series of closely time-equivalent deposits that correlate with seismic reflector horizon A exists along the coast of eastern North America. These sediments of Late-Early to Early-Middle Eocene age contain an authigenic mineral suite indicative of the alteration of volcanic glass. A volcanic origin for these siliceous deposits onshore is consistent with a volcanic origin for the cherts of horizon A offshore.

  8. Bare quantifier fronting as contrastive topicalization

    Directory of Open Access Journals (Sweden)

    Ion Giurgea

    2015-11-01

    Full Text Available I argue that indefinites (in particular bare quantifiers such as ‘something’, ‘somebody’, etc. which are neither existentially presupposed nor in the restriction of a quantifier over situations, can undergo topicalization in a number of Romance languages (Catalan, Italian, Romanian, Spanish, but only if the sentence contains “verum” focus, i.e. focus on a high degree of certainty of the sentence. I analyze these indefinites as contrastive topics, using Büring’s (1999 theory (where the term ‘S-topic’ is used for what I call ‘contrastive topic’. I propose that the topic is evaluated in relation to a scalar set including generalized quantifiers such as {lP $x P(x, lP MANYx P(x, lP MOSTx P(x, lP “xP(x} or {lP $xP(x, lP P(a, lP P(b …}, and that the contrastive topic is the weakest generalized quantifier in this set. The verum focus, which is part of the “comment” that co-occurs with the “Topic”, introduces a set of alternatives including degrees of certainty of the assertion. The speaker asserts that his claim is certainly true or highly probable, contrasting it with stronger claims for which the degree of probability is unknown. This explains the observation that in downward entailing contexts, the fronted quantified DPs are headed by ‘all’ or ‘many’, whereas ‘some’, small numbers or ‘at least n’ appear in upward entailing contexts. Unlike other cases of non-specific topics, which are property topics, these are quantifier topics: the topic part is a generalized quantifier, the comment is a property of generalized quantifiers. This explains the narrow scope of the fronted quantified DP.

  9. Salinity fronts in the tropical Pacific Ocean.

    Science.gov (United States)

    Kao, Hsun-Ying; Lagerloef, Gary S E

    2015-02-01

    This study delineates the salinity fronts (SF) across the tropical Pacific, and describes their variability and regional dynamical significance using Aquarius satellite observations. From the monthly maps of the SF, we find that the SF in the tropical Pacific are (1) usually observed around the boundaries of the fresh pool under the intertropical convergence zone (ITCZ), (2) stronger in boreal autumn than in other seasons, and (3) usually stronger in the eastern Pacific than in the western Pacific. The relationship between the SF and the precipitation and the surface velocity are also discussed. We further present detailed analysis of the SF in three key tropical Pacific regions. Extending zonally around the ITCZ, where the temperature is nearly homogeneous, we find the strong SF of 1.2 psu from 7° to 11°N to be the main contributor of the horizontal density difference of 0.8 kg/m 3 . In the eastern Pacific, we observe a southward extension of the SF in the boreal spring that could be driven by both precipitation and horizontal advection. In the western Pacific, the importance of these newly resolved SF associated with the western Pacific warm/fresh pool and El Niño southern oscillations are also discussed in the context of prior literature. The main conclusions of this study are that (a) Aquarius satellite salinity measurements reveal the heretofore unknown proliferation, structure, and variability of surface salinity fronts, and that (b) the fine-scale structures of the SF in the tropical Pacific yield important new information on the regional air-sea interaction and the upper ocean dynamics.

  10. Volcanic Hazards in Site Evaluation for Nuclear Installations

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2012-10-15

    This publication provides comprehensive and updated guidance for site evaluation in relation to volcanic hazards. It includes recommendations on assessing the volcanic hazards at a nuclear installation site, in order to identify and characterize, in a comprehensive manner, all potentially hazardous phenomena that may be associated with future volcanic events. It describes how some of these volcanic phenomena may affect the acceptability of the selected site, resulting in exclusion of a site or determining the corresponding design basis parameters for the installation. This Safety Guide is applicable to both existing and new sites, and a graded approach is recommended to cater for all types of nuclear installations. Contents: 1. Introduction; 2. Overview of volcanic hazard assessment; 3. General recommendations; 4. Necessary information and investigations (database); 5. Screening of volcanic hazards; 6. Site specific volcanic hazard assessment; 7. Nuclear installations other than nuclear power plants; 8. Monitoring and preparation for response; 9. Management system for volcanic hazard assessment; Annex I: Volcanic hazard scenarios; Annex II: Worldwide sources of information.

  11. Constructional Volcanic Edifices on Mercury: Candidates and Hypotheses of Formation

    Science.gov (United States)

    Wright, Jack; Rothery, David A.; Balme, Matthew R.; Conway, Susan J.

    2018-04-01

    Mercury, a planet with a predominantly volcanic crust, has perplexingly few, if any, constructional volcanic edifices, despite their common occurrence on other solar system bodies with volcanic histories. Using image and topographical data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, we describe two small (Earth and the Moon. Though we cannot definitively conclude that these landforms are volcanic, the paucity of constructional volcanic edifices on Mercury is intriguing in itself. We suggest that this lack is because volcanic eruptions with sufficiently low eruption volumes, rates, and flow lengths, suitable for edifice construction, were highly spatiotemporally restricted during Mercury's geological history. We suggest that volcanic edifices may preferentially occur in association with late-stage, postimpact effusive volcanic deposits. The European Space Agency/Japan Aerospace Exploration Agency BepiColombo mission to Mercury will be able to investigate further our candidate volcanic edifices; search for other, as-yet unrecognized edifices beneath the detection limits of MESSENGER data; and test our hypothesis that edifice construction is favored by late-stage, low-volume effusive eruptions.

  12. Basaltic volcanic episodes of the Yucca Mountain region

    International Nuclear Information System (INIS)

    Crowe, B.M.

    1990-01-01

    The purpose of this paper is to summarize briefly the distribution and geologic characteristics of basaltic volcanism in the Yucca Mountain region during the last 10--12 Ma. This interval largely postdates the major period of silicic volcanism and coincides with and postdates the timing of major extensional faulting in the region. Field and geochronologic data for the basaltic rocks define two distinct episodes. The patterns in the volume and spatial distribution of these basaltic volcanic episodes in the central and southern part of the SNVF are used as a basis for forecasting potential future volcanic activity in vicinity of Yucca Mountain. 33 refs., 2 figs

  13. MMIC front-ends for optical communication systems

    DEFF Research Database (Denmark)

    Petersen, Anders Kongstad

    1993-01-01

    Two different types of optical front-end MMIC amplifiers for a 2.5-Gb/s coherent heterodyne optical receiver are presented. A bandwidth of 6-12 GHz has been obtained for a tuned front-end and 3-13 GHz for a distributed front-end. An input noise current density of 5-15 pA/√Hz has been obtained for...

  14. The upgraded CDF front end electronics for calorimetry

    Energy Technology Data Exchange (ETDEWEB)

    Drake, G.; Frei, D.; Hahn, S.R.; Nelson, C.A.; Segler, S.L.; Stuermer, W.

    1991-11-01

    The front end electronics used in the calorimetry of the CDF detector has been upgraded to meet system requirements for higher expected luminosity. A fast digitizer utilizing a 2 {mu}Sec, 16 bit ADC has been designed and built. Improvements to the front end trigger circuitry have been implemented, including the production of 900 new front end modules. Operational experience with the previous system is presented, with discussion of the problems and performance goals.

  15. The upgraded CDF front end electronics for calorimetry

    International Nuclear Information System (INIS)

    Drake, G.; Frei, D.; Hahn, S.R.; Nelson, C.A.; Segler, S.L.; Stuermer, W.

    1991-11-01

    The front end electronics used in the calorimetry of the CDF detector has been upgraded to meet system requirements for higher expected luminosity. A fast digitizer utilizing a 2 μSec, 16 bit ADC has been designed and built. Improvements to the front end trigger circuitry have been implemented, including the production of 900 new front end modules. Operational experience with the previous system is presented, with discussion of the problems and performance goals

  16. Mud volcanism of South-Caspian depression

    International Nuclear Information System (INIS)

    Aliyev, A.A.

    2002-01-01

    Full text : South-Caspian depression is presented by area of large warping with thick (more than 25 km) sedimentary series and with wide development of mud volcanism. This depression is unique according to its number of mud volcanoes and intensity of their eruptions. There are about 400 mud volcanoes in this area, which is more than than a half of all volcanoes of the planet. Among them - 220 are continental, more 170 are marine, defined by different methods in the South-Caspian aquatorium. As a result of mudvolcanic activity islands, banks, shoals and underwater ridges are formed in marine conditions. Depths of underwater volcanoes vary from few meters to 900 m as the height of cones are different too. Marine mud volcanoes in geological history of Caspian sea evolution and in its recent history had and important significance. Activity of mud volcanoes in sea conditions lead to the formation of positive elements of relief. Products of ejection take part in the formation of microrelief of surrounding areas of sea bottom influence upon its dynamics and composition of bottom sediments. The carried out comparative analysis of mud volcanism manifestation both onshore and offshore showed the basic differences and similarities in morphology of volcanoes and geology-geochemical peculiarities of eruption products. New data on tectonics of mud volcanism development has been obtained over recent years. Mud volcanoes of South-Caspian depression are studied for assessment and oil-gas content of deep-seated deposits. Geochemical method of search of oil and gas deposits in mudvolcanic areas had been worked out.

  17. Application of deep convolutional neural networks for ocean front recognition

    Science.gov (United States)

    Lima, Estanislau; Sun, Xin; Yang, Yuting; Dong, Junyu

    2017-10-01

    Ocean fronts have been a subject of study for many years, a variety of methods and algorithms have been proposed to address the problem of ocean fronts. However, all these existing ocean front recognition methods are built upon human expertise in defining the front based on subjective thresholds of relevant physical variables. This paper proposes a deep learning approach for ocean front recognition that is able to automatically recognize the front. We first investigated four existing deep architectures, i.e., AlexNet, CaffeNet, GoogLeNet, and VGGNet, for the ocean front recognition task using remote sensing (RS) data. We then propose a deep network with fewer layers compared to existing architecture for the front recognition task. This network has a total of five learnable layers. In addition, we extended the proposed network to recognize and classify the front into strong and weak ones. We evaluated and analyzed the proposed network with two strategies of exploiting the deep model: full-training and fine-tuning. Experiments are conducted on three different RS image datasets, which have different properties. Experimental results show that our model can produce accurate recognition results.

  18. Volcanism/tectonics working group summary

    International Nuclear Information System (INIS)

    Kovach, L.A.; Young, S.R.

    1995-01-01

    This article is a summary of the proceedings of a group discussion which took place at the Workshop on the Role of Natural Analogs in Geologic Disposal of High-Level Nuclear Waste in San Antonio, Texas on July 22-25, 1991. The working group concentrated on the subject of the impacts of earthquakes, fault rupture, and volcanic eruption on the underground repository disposal of high-level radioactive wastes. The tectonics and seismic history of the Yucca Mountain site in Nevada is discussed and geologic analogs to that site are described

  19. VOLCANIC RISK ASSESSMENT - PROBABILITY AND CONSEQUENCES

    International Nuclear Information System (INIS)

    G.A. Valentine; F.V. Perry; S. Dartevelle

    2005-01-01

    Risk is the product of the probability and consequences of an event. Both of these must be based upon sound science that integrates field data, experiments, and modeling, but must also be useful to decision makers who likely do not understand all aspects of the underlying science. We review a decision framework used in many fields such as performance assessment for hazardous and/or radioactive waste disposal sites that can serve to guide the volcanological community towards integrated risk assessment. In this framework the underlying scientific understanding of processes that affect probability and consequences drive the decision-level results, but in turn these results can drive focused research in areas that cause the greatest level of uncertainty at the decision level. We review two examples of the determination of volcanic event probability: (1) probability of a new volcano forming at the proposed Yucca Mountain radioactive waste repository, and (2) probability that a subsurface repository in Japan would be affected by the nearby formation of a new stratovolcano. We also provide examples of work on consequences of explosive eruptions, within the framework mentioned above. These include field-based studies aimed at providing data for ''closure'' of wall rock erosion terms in a conduit flow model, predictions of dynamic pressure and other variables related to damage by pyroclastic flow into underground structures, and vulnerability criteria for structures subjected to conditions of explosive eruption. Process models (e.g., multiphase flow) are important for testing the validity or relative importance of possible scenarios in a volcanic risk assessment. We show how time-dependent multiphase modeling of explosive ''eruption'' of basaltic magma into an open tunnel (drift) at the Yucca Mountain repository provides insight into proposed scenarios that include the development of secondary pathways to the Earth's surface. Addressing volcanic risk within a decision

  20. Seismological evidence for a sub-volcanic arc mantle wedge beneath the Denali volcanic gap, Alaska

    Science.gov (United States)

    McNamara, D.E.; Pasyanos, M.E.

    2002-01-01

    Arc volcanism in Alaska is strongly correlated with the 100 km depth contour of the western Aluetian Wadati-Benioff zone. Above the eastern portion of the Wadati-Benioff zone however, there is a distinct lack of volcanism (the Denali volcanic gap). We observe high Poisson's ratio values (0.29-0.33) over the entire length of the Alaskan subduction zone mantle wedge based on regional variations of Pn and Sn velocities. High Poisson's ratios at this depth (40-70 km), adjacent to the subducting slab, are attributed to melting of mantle-wedge peridotites, caused by fluids liberated from the subducting oceanic crust and sediments. Observations of high values of Poisson's ratio, beneath the Denali volcanic gap suggest that the mantle wedge contains melted material that is unable to reach the surface. We suggest that its inability to migrate through the overlying crust is due to increased compression in the crust at the northern apex of the curved Denali fault.

  1. Modelling ground deformation patterns associated with volcanic processes at the Okataina Volcanic Centre

    Science.gov (United States)

    Holden, L.; Cas, R.; Fournier, N.; Ailleres, L.

    2017-09-01

    The Okataina Volcanic Centre (OVC) is one of two large active rhyolite centres in the modern Taupo Volcanic Zone (TVZ) in the North Island of New Zealand. It is located in a complex section of the Taupo rift, a tectonically active section of the TVZ. The most recent volcanic unrest at the OVC includes the 1315 CE Kaharoa and 1886 Tarawera eruptions. Current monitoring activity at the OVC includes the use of continuous GPS receivers (cGPS), lake levelling and seismographs. The ground deformation patterns preceding volcanic activity the OVC are poorly constrained and restricted to predictions from basic modelling and comparison to other volcanoes worldwide. A better understanding of the deformation patterns preceding renewed volcanic activity is essential to determine if observed deformation is related to volcanic, tectonic or hydrothermal processes. Such an understanding also means that the ability of the present day cGPS network to detect these deformation patterns can also be assessed. The research presented here uses the finite element (FE) modelling technique to investigate ground deformation patterns associated with magma accumulation and diking processes at the OVC in greater detail. A number of FE models are produced and tested using Pylith software and incorporate characteristics of the 1315 CE Kaharoa and 1886 Tarawera eruptions, summarised from the existing body of research literature. The influence of a simple ring fault structure at the OVC on the modelled deformation is evaluated. The ability of the present-day continuous GPS (cGPS) GeoNet monitoring network to detect or observe the modelled deformation is also considered. The results show the modelled horizontal and vertical displacement fields have a number of key features, which include prominent lobe based regions extending northwest and southeast of the OVC. The results also show that the ring fault structure increases the magnitude of the displacements inside the caldera, in particular in the

  2. Slab dehydration in Cascadia and its relationship to volcanism, seismicity, and non-volcanic tremor

    Science.gov (United States)

    Delph, J. R.; Levander, A.; Niu, F.

    2017-12-01

    The characteristics of subduction beneath the Pacific Northwest (Cascadia) are variable along strike, leading to the segmentation of Cascadia into 3 general zones: Klamath, Siletzia, and Wrangelia. These zones show marked differences in tremor density, earthquake density, seismicity rates, and the locus and amount of volcanism in the subduction-related volcanic arc. To better understand what controls these variations, we have constructed a 3D shear-wave velocity model of the upper 80 km along the Cascadia margin from the joint inversion of CCP-derived receiver functions and ambient noise surface wave data using 900 temporary and permanent broadband seismic stations. With this model, we can investigate variations in the seismic structure of the downgoing oceanic lithosphere and overlying mantle wedge, the character of the crust-mantle transition beneath the volcanic arc, and local to regional variations in crustal structure. From these results, we infer the presence and distribution of fluids released from the subducting slab and how they affect the seismic structure of the overriding lithosphere. In the Klamath and Wrangelia zones, high seismicity rates in the subducting plate and high tremor density correlate with low shear velocities in the overriding plate's forearc and relatively little arc volcanism. While the cause of tremor is debated, intermediate depth earthquakes are generally thought to be due to metamorphic dehydration reactions resulting from the dewatering of the downgoing slab. Thus, the seismic characteristics of these zones combined with rather sparse arc volcanism may indicate that the slab has largely dewatered by the time it reaches sub-arc depths. Some of the water released during earthquakes (and possibly tremor) may percolate into the overriding plate, leading to slow seismic velocities in the forearc. In contrast, Siletzia shows relatively low seismicity rates and tremor density, with relatively higher shear velocities in the forearc

  3. 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

  4. Adakite-like volcanism of Ecuador: lower crust magmatic evolution and recycling

    Science.gov (United States)

    Chiaradia, Massimo; Müntener, Othmar; Beate, Bernardo; Fontignie, Denis

    2009-11-01

    In the Northern Andes of Ecuador, a broad Quaternary volcanic arc with significant across-arc geochemical changes sits upon continental crust consisting of accreted oceanic and continental terranes. Quaternary volcanic centers occur, from west to east, along the Western Cordillera (frontal arc), in the Inter-Andean Depression and along the Eastern Cordillera (main arc), and in the Sub-Andean Zone (back-arc). The adakite-like signatures of the frontal and main arc volcanoes have been interpreted either as the result of slab melting plus subsequent slab melt-mantle interactions or of lower crustal melting, fractional crystallization, and assimilation processes. In this paper, we present petrographic, geochemical, and isotopic (Sr, Nd, Pb) data on dominantly andesitic to dacitic volcanic rocks as well as crustal xenolith and cumulate samples from five volcanic centers (Pululagua, Pichincha, Ilalo, Chacana, Sumaco) forming a NW-SE transect at about 0° latitude and encompassing the frontal (Pululagua, Pichincha), main (Ilalo, Chacana), and back-arc (Sumaco) chains. All rocks display typical subduction-related geochemical signatures, such as Nb and Ta negative anomalies and LILE enrichment. They show a relative depletion of fluid-mobile elements and a general increase in incompatible elements from the front to the back-arc suggesting derivation from progressively lower degrees of partial melting of the mantle wedge induced by decreasing amounts of fluids released from the slab. We observe widespread petrographic evidence of interaction of primary melts with mafic xenoliths as well as with clinopyroxene- and/or amphibole-bearing cumulates and of magma mixing at all frontal and main arc volcanic centers. Within each volcanic center, rocks display correlations between evolution indices and radiogenic isotopes, although absolute variations of radiogenic isotopes are small and their values are overall rather primitive (e.g., ɛNd = +1.5 to +6, 87Sr/86Sr = 0

  5. Geoethics implications in volcanic hazards in Argentina: 24 years of uninterrupted ash-fall

    Science.gov (United States)

    Rovere, Elizabeth I.; Violante, Roberto A.; Uber, Silvia M.; Vázquez Herrera, Marcelo

    2016-04-01

    bricks, abrasive cleaning powders, raw material for cosmetics, glass, porcelain, etc. From a geoscientific deontology point of view, there are a wide range of parameters to be considered in terms of the interaction of human activities, the rapid own decisions, the roll in front of our colleagues, and the responsibility towards society and the environment. The ethical implications of geo communication and education must be supported under standards and strategic plans that address all socio-cultural aspects and include primarily, women heads of households and teachers who will have to make decisions for their children in times of emergency. After the eruption of 1932 there was a gap of 59 years without a significant eruption and ashfall in Argentina. Why the actions taken for the use of volcanic ash as a resource were not repeated during the eruptions occurred in 1991 and beyond? This contribution intends to answer this question which has multiple variables that turn around the economy, politics and socio-cultural traditions of European immigrants in Argentina.

  6. Reduced cooling following future volcanic eruptions

    Science.gov (United States)

    Hopcroft, Peter O.; Kandlbauer, Jessy; Valdes, Paul J.; Sparks, R. Stephen J.

    2017-11-01

    Volcanic eruptions are an important influence on decadal to centennial climate variability. Large eruptions lead to the formation of a stratospheric sulphate aerosol layer which can cause short-term global cooling. This response is modulated by feedback processes in the earth system, but the influence from future warming has not been assessed before. Using earth system model simulations we find that the eruption-induced cooling is significantly weaker in the future state. This is predominantly due to an increase in planetary albedo caused by increased tropospheric aerosol loading with a contribution from associated changes in cloud properties. The increased albedo of the troposphere reduces the effective volcanic aerosol radiative forcing. Reduced sea-ice coverage and hence feedbacks also contribute over high-latitudes, and an enhanced winter warming signal emerges in the future eruption ensemble. These findings show that the eruption response is a complex function of the environmental conditions, which has implications for the role of eruptions in climate variability in the future and potentially in the past.

  7. Robust satellite techniques for monitoring volcanic eruptions

    Energy Technology Data Exchange (ETDEWEB)

    Pergola, N.; Pietrapertosa, C. [Consiglio Nazionale delle Ricerche, Istituto di Metodologie Avanzate, Tito Scalo, PZ (Italy); Lacava, T.; Tramutoli, V. [Potenza Universita' della Basilicata, Potenza (Italy). Dipt. di Ingegneria e Fisica dell' Ambiente

    2001-04-01

    Through this paper the robust approach to monitoring volcanic aerosols by satellite is applied to an extended set of events affecting Stromboli and Etna volcanoes to assess its performance in automated detection of eruptive clouds and in monitoring pre-eruptive emission activities. Using only NOAA/AVHRR data at hand (without any specific atmospheric model or ancillary ground-based measurements) the proposed method automatically discriminates meteorological from eruptive volcanic clouds and, in several cases, identified pre-eruptive anomalies in the emission rates not identified by traditional methods. The main merit of this approach is its effectiveness in recognising field anomalies also in the presence of a highly variable surface background as well as its intrinsic exportability not only on different geographic areas but also on different satellite instrumental packages. In particular, the possibility to extend the proposed method to the incoming new MSG/SEVIRI satellite package (which is going to fly next year) with its improved spectral (specific bands for SO{sub 2}) and temporal (up to 15 min) resolutions has been evaluated representing the natural continuation of this work.

  8. Viscosity characteristics of selected volcanic rock melts

    Science.gov (United States)

    Hobiger, Manuel; Sonder, Ingo; Büttner, Ralf; Zimanowski, Bernd

    2011-02-01

    A basic experimental study of the behavior of magma rheology was carried out on remelted volcanic rocks using wide gap viscometry. The complex composition of magmatic melts leads to complicated rheologic behavior which cannot be described with one simple model. Therefore, measurement procedures which are able to quantify non-Newtonian behavior have to be employed. Furthermore, the experimental apparatus must be able to deal with inhomogeneities of magmatic melts. We measured the viscosity of a set of materials representing a broad range of volcanic processes. For the lower viscous melts (low-silica compositions), non-Newtonian behavior is observed, whereas the high-silica melts show Newtonian behavior in the measured temperature and shear rate range (T = 1423 K - 1623 K, γ˙ = 10 - 2 s - 1 - 20 s - 1 ). The non-Newtonian materials show power-law behavior. The measured viscosities η and power-law indexes m lie in the intervals 8 Pa s ≤ η ≤ 210 3 Pa s, 0.71 ≤ m ≤ 1.0 (Grímsvötn basalt), 0.9 Pa s ≤ η ≤ 350 Pa s, 0.61 ≤ m ≤ 0.93 (Hohenstoffeln olivine-melilitite), and 8 Pa s ≤ η ≤ 1.510 4 Pa s, 0.55 ≤ m ≤ 1.0 (Sommata basalt). Measured viscosities of the Newtonian high-silica melts lie in the range 10 4 Pa s ≤ η ≤ 310 5 Pa s.

  9. The scientific management of volcanic crises

    Science.gov (United States)

    Marzocchi, Warner; Newhall, Christopher; Woo, Gordon

    2012-12-01

    Sound scientific management of volcanic crises is the primary tool to reduce significantly volcanic risk in the short-term. At present, a wide variety of qualitative or semi-quantitative strategies is adopted, and there is not yet a commonly accepted quantitative and general strategy. Pre-eruptive processes are extremely complicated, with many degrees of freedom nonlinearly coupled, and poorly known, so scientists must quantify eruption forecasts through the use of probabilities. On the other hand, this also forces decision-makers to make decisions under uncertainty. We review the present state of the art in this field in order to identify the main gaps of the existing procedures. Then, we put forward a general quantitative procedure that may overcome the present barriers, providing guidelines on how probabilities may be used to take rational mitigation actions. These procedures constitute a crucial link between science and society; they can be used to establish objective and transparent decision-making protocols and also clarify the role and responsibility of each partner involved in managing a crisis.

  10. WSR-88D observations of volcanic ash

    Science.gov (United States)

    Wood, J.; Scott, C.; Schneider, D.

    2007-01-01

    Conclusions that may impact operations are summarized below: ??? Current VCPs may not be optimal for the scharacterization of volcanic events. Therefore, the development of a new VCP that combines the enhanced low level elevation density and increased temporal resolution of VCP 12 with the enhanced sensitivity of VCP 31. ??? Given currently available scan strategies, this preliminary investigation would suggest that it is advisable to use VCP 12 during the initial explosive phase of an eruptive event. Once the maximum reflectivity has dropped below 30 dBZ, VCP 31 should be used. ??? This study clearly indicates that WSR-88D Level II data offers many advantages over Level III data currently available in Alaska. The ability to access this data would open up greater opportunities for research. Given the proximity of WSR-88D platforms to active volcanoes in Alaska, as well as in the western Lower 48 states and Hawaii, radar data will likely play a major operational role when volcanic eruptions again pose a threat to life and property. The utilization of this tool to its maximum capability is vital.

  11. Nano-volcanic Eruption of Silver

    Science.gov (United States)

    Lin, Shih-Kang; Nagao, Shijo; Yokoi, Emi; Oh, Chulmin; Zhang, Hao; Liu, Yu-Chen; Lin, Shih-Guei; Suganuma, Katsuaki

    2016-10-01

    Silver (Ag) is one of the seven metals of antiquity and an important engineering material in the electronic, medical, and chemical industries because of its unique noble and catalytic properties. Ag thin films are extensively used in modern electronics primarily because of their oxidation-resistance. Here we report a novel phenomenon of Ag nano-volcanic eruption that is caused by interactions between Ag and oxygen (O). It involves grain boundary liquation, the ejection of transient Ag-O fluids through grain boundaries, and the decomposition of Ag-O fluids into O2 gas and suspended Ag and Ag2O clusters. Subsequent coating with re-deposited Ag-O and the de-alloying of O yield a conformal amorphous Ag coating. Patterned Ag hillock arrays and direct Ag-to-Ag bonding can be formed by the homogenous crystallization of amorphous coatings. The Ag “nano-volcanic eruption” mechanism is elaborated, shedding light on a new mechanism of hillock formation and new applications of amorphous Ag coatings.

  12. Modulations of stratospheric ozone by volcanic eruptions

    Science.gov (United States)

    Blanchette, Christian; Mcconnell, John C.

    1994-01-01

    We have used a time series of aerosol surface based on the measurements of Hofmann to investigate the modulation of total column ozone caused by the perturbation to gas phase chemistry by the reaction N2O5(gas) + H2O(aero) yields 2HNO3(gas) on the surface of stratospheric aerosols. We have tested a range of values for its reaction probability, gamma = 0.02, 0.13, and 0.26 which we compared to unperturbed homogeneous chemistry. Our analysis spans a period from Jan. 1974 to Oct. 1994. The results suggest that if lower values of gamma are the norm then we would expect larger ozone losses for highly enhanced aerosol content that for larger values of gamma. The ozone layer is more sensitive to the magnitude of the reaction probability under background conditions than during volcanically active periods. For most conditions, the conversion of NO2 to HNO3 is saturated for reaction probability in the range of laboratory measurements, but is only absolutely saturated following major volcanic eruptions when the heterogeneous loss dominates the losses of N2O5. The ozone loss due to this heterogeneous reaction increases with the increasing chlorine load. Total ozone losses calculated are comparable to ozone losses reported from TOMS and Dobson data.

  13. Mantle updrafts and mechanisms of oceanic volcanism

    Science.gov (United States)

    Anderson, Don L.; Natland, James H.

    2014-10-01

    Convection in an isolated planet is characterized by narrow downwellings and broad updrafts-consequences of Archimedes' principle, the cooling required by the second law of thermodynamics, and the effect of compression on material properties. A mature cooling planet with a conductive low-viscosity core develops a thick insulating surface boundary layer with a thermal maximum, a subadiabatic interior, and a cooling highly conductive but thin boundary layer above the core. Parts of the surface layer sink into the interior, displacing older, colder material, which is entrained by spreading ridges. Magma characteristics of intraplate volcanoes are derived from within the upper boundary layer. Upper mantle features revealed by seismic tomography and that are apparently related to surface volcanoes are intrinsically broad and are not due to unresolved narrow jets. Their morphology, aspect ratio, inferred ascent rate, and temperature show that they are passively responding to downward fluxes, as appropriate for a cooling planet that is losing more heat through its surface than is being provided from its core or from radioactive heating. Response to doward flux is the inverse of the heat-pipe/mantle-plume mode of planetary cooling. Shear-driven melt extraction from the surface boundary layer explains volcanic provinces such as Yellowstone, Hawaii, and Samoa. Passive upwellings from deeper in the upper mantle feed ridges and near-ridge hotspots, and others interact with the sheared and metasomatized surface layer. Normal plate tectonic processes are responsible both for plate boundary and intraplate swells and volcanism.

  14. 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

  15. Volcanic ash in ancient Maya ceramics of the limestone lowlands: implications for prehistoric volcanic activity in the Guatemala highlands

    Science.gov (United States)

    Ford, Anabel; Rose, William I.

    1995-07-01

    In the spirit of collaborative research, Glicken and Ford embarked on the problem of identifying the source of volcanic ash used as temper in prehistoric Maya ceramics. Verification of the presence of glass shards and associated volcanic mineralogy in thin sections of Maya ceramics was straightforward and pointed to the Guatemala Highland volcanic chain. Considering seasonal wind rose patterns, target volcanoes include those from the area west of and including Guatemala City. Joint field research conducted in 1983 by Glicken and Ford in the limestone lowlands of Belize and neighboring Guatemala, 300 km north of the volcanic zone and 150 km from the nearest identified ash deposits, was unsuccessful in discovering local volcanic ash deposits. The abundance of the ash in common Maya ceramic vessels coupled with the difficulties of long-distance procurement without draft animals lead Glicken to suggest that ashfall into the lowlands would most parsimoniously explain prehistoric procurement; it literally dropped into their hands. A major archaeological problem with this explanation is that the use of volcanic ash occurring over several centuries of the Late Classic Period (ca. 600-900 AD). To accept the ashfall hypothesis for ancient Maya volcanic ash procurement, one would have to demonstrate a long span of consistent volcanic activity in the Guatemala Highlands for the last half of the first millennium AD. Should this be documented through careful petrographic, microprobe and tephrachronological studies, a number of related archaeological phenomena would be explained. In addition, the proposed model of volcanic activity has implications for understanding volcanism and potential volcanic hazards in Central America over a significantly longer time span than the historic period. These avenues are explored and a call for further collaborative research of this interdisciplinary problem is extended in this paper.

  16. Compositional Differences between Felsic Volcanic rocks from the ...

    African Journals Online (AJOL)

    The elemental and Sr-Nd isotopic compositions of the volcanic rocks suggest that fractional crystallization from differing basic parents accompanied by a limited assimilation (AFC) was the dominant process controlling the genesis of the MER felsic volcanic rocks. Keywords: Ethiopia; Northern Main Ethiopian Rift; Bimodal ...

  17. Assessment of the atmospheric impact of volcanic eruptions

    Science.gov (United States)

    Sigurdsson, H.

    1988-01-01

    The dominant global impact of volcanic activity is likely to be related to the effects of volcanic gases on the Earth's atmosphere. Volcanic gas emissions from individual volcanic arc eruptions are likely to cause increases in the stratospheric optical depth that result in surface landmass temperature decline of 2 to 3 K for less than a decade. Trachytic and intermediate magmas are much more effective in this regard than high-silica magmas, and may also lead to extensive ozone depletion due to effect of halogens and magmatic water. Given the assumed relationship between arc volcanism and subduction rate, and the relatively small variation in global spreading rates in the geologic record, it is unlikely that the rates of arc volcanism have varied greatly during the Cenozoic. Hotspot related basaltic fissure eruptions in the subaerial environment have a higher mass yield of sulfur, but lofting of the valcanic aerosol to levels above the tropopause is required for a climate impact. High-latitude events, such as the Laki 1783 eruption can easily penetrate the tropopause and enter the stratosphere, but formation of a stratospheric volcanic aerosol form low-latitude effusive basaltic eruptions is problematical, due to the elevated low-latitude tropopause. Due to the high sulfur content of hotspot-derived basaltic magmas, their very high mass eruption rates and the episodic behavior, hotspots must be regarded as potentially major modifiers of Earth's climate through the action of their volcanic volatiles on the chemistry and physics of the atmosphere.

  18. Volcanic Ash from the 1999 Eruption of Mount Cameroon Volcano ...

    African Journals Online (AJOL)

    2008-10-21

    Oct 21, 2008 ... fluorine (F) content of the ash was determined by the selective ion electrode method. The results ... the main mineral in volcanic ash responsible for causing silicosis. The F ... volcanic ash with little or no attention to the < 4 µm.

  19. Improving communication during volcanic crises on small, vulnerable islands

    Science.gov (United States)

    McGuire, W. J.; Solana, M. C.; Kilburn, C. R. J.; Sanderson, D.

    2009-05-01

    Increased exposure to volcanic hazard, particularly at vulnerable small islands, is driving an urgent and growing need for improved communication between monitoring scientists, emergency managers and the media, in advance of and during volcanic crises. Information gathering exercises undertaken on volcanic islands (Guadeloupe, St. Vincent and Montserrat) in the Lesser Antilles (eastern Caribbean), which have recently experienced - or are currently experiencing - volcanic action, have provided the basis for the compilation and publication of a handbook on Communication During Volcanic Emergencies, aimed at the principal stakeholder groups. The findings of the on-island surveys point up the critical importance of (1) bringing together monitoring scientists, emergency managers, and representatives of the media, well in advance of a volcanic crisis, and (2), ensuring that procedures and protocols are in place that will allow, as far as possible, effective and seamless cooperation and coordination when and if a crisis situation develops. Communication During Volcanic Emergencies is designed to promote and encourage both of these priorities through providing the first source-book addressing working relationships and inter-linkages between the stakeholder groups, and providing examples of good and bad practice. While targeting the volcanic islands of the eastern Caribbean, the source-book and its content are largely generic, and the advice and guidelines contained therein have equal validity in respect of improving communication before and during crises at any volcano, and have application to the communication issue in respect of a range of other geophysical hazards.

  20. The PHENIX Drift Chamber Front End Electroncs

    Science.gov (United States)

    Pancake, C.; Velkovska, J.; Pantuev, V.; Fong, D.; Hemmick, T.

    1998-04-01

    The PHENIX Drift Chamber (DC) is designed to operate in the high particle flux environment of the Relativistic Heavy Ion Collider and provide high resolution track measurements. It is segmented into 80 keystones with 160 readout channels each. The Front End Electronics (FEE) developed to meet the demanding operating conditions and the large number of readout channels of the DC will be discussed. It is based on two application specific integrated circuits: the ASD8 and the TMC-PHX1. The ASD8 chip contains 8 channels of bipolar amplifier-shaper-discriminator with 6 ns shaping time and ≈ 20 ns pulse width, which satisfies the two track resolution requirements. The TMC-PHX1 chip is a high-resolution multi-hit Time-to-Digital Converter. The outputs from the ASD8 are digitized in the Time Memory Cell (TMC) every (clock period)/32 or 0.78 ns (at 40 MHz), which gives the intrinsic time resolution of the system. A 256 words deep dual port memory keeps 6.4 μs time history of data at 40 MHz clock. Each DC keystone is supplied with 4 ASD8/TMC boards and one FEM board, which performs the readout of the TMC-PHX1's, buffers and formats the data to be transmitted over the Glink. The slow speed control communication between the FEM and the system is carried out over ARCNET. The full readout chain and the data aquisition system are being tested.

  1. How I treat CLL up front.

    Science.gov (United States)

    Gribben, John G

    2010-01-14

    Although chronic lymphocytic leukemia (CLL) remains incurable, over the past decade there have been major advances in understanding the pathophysiology of CLL and in the treatment of this disease. This has led to greatly increased response rates and durations of response but not yet improved survival. Advances in the use of prognostic factors that identify patients at high risk for progression have led us to the question whether there is still a role for a "watch and wait" approach in asymptomatic high-risk patients or whether they should be treated earlier in their disease course. Questions remain, including, what is the optimal first-line treatment and its timing and is there any role of maintenance therapy or stem cell transplantation in this disease? CLL is a disease of the elderly and not all patients are eligible for aggressive up-front chemoimmunotherapy regimens, so what is the optimal treatment approach for more frail elderly patients? It is highly likely that our treatment approaches will continue to evolve as the results of ongoing clinical trials are released and that further improvements in the outcome of this disease will result from identification of therapies that target the underlying pathophysiology of CLL.

  2. Front lighted optical tooling method and apparatus

    International Nuclear Information System (INIS)

    Stone, W. J.

    1985-01-01

    An optical tooling method and apparatus uses a front lighted shadowgraphic technique to enhance visual contrast of reflected light. The apparatus includes an optical assembly including a fiducial mark, such as cross hairs, reflecting polarized light with a first polarization, a polarizing element backing the fiducial mark and a reflective surface backing the polarizing element for reflecting polarized light bypassing the fiducial mark and traveling through the polarizing element. The light reflected by the reflecting surface is directed through a second pass of the polarizing element toward the frontal direction with a polarization differing from the polarization of the light reflected by the fiducial mark. When used as a tooling target, the optical assembly may be mounted directly to a reference surface or may be secured in a mounting, such as a magnetic mounting. The optical assembly may also be mounted in a plane defining structure and used as a spherometer in conjunction with an optical depth measuring instrument. A method of measuring a radius of curvature of an unknown surface includes positioning the spherometer on a surface between the surface and a depth measuring optical instrument. As the spherometer is frontally illuminated, the distance from the depth measuring instrument to the fiducial mark and the underlying surface are alternately measured and the difference in these measurements is used as the sagittal height to calculate a radius of curvature

  3. Front tracking for hyperbolic conservation laws

    CERN Document Server

    Holden, Helge

    2015-01-01

    This is the second edition of a well-received book providing the fundamentals of the theory hyperbolic conservation laws. Several chapters have been rewritten, new material has been added, in particular, a chapter on space dependent flux functions, and the detailed solution of the Riemann problem for the Euler equations. Hyperbolic conservation laws are central in the theory of nonlinear partial differential equations and in science and technology. The reader is given a self-contained presentation using front tracking, which is also a numerical method. The multidimensional scalar case and the case of systems on the line are treated in detail. A chapter on finite differences is included. From the reviews of the first edition: "It is already one of the few best digests on this topic. The present book is an excellent compromise between theory and practice. Students will appreciate the lively and accurate style." D. Serre, MathSciNet  "I have read the book with great pleasure, and I can recommend it to experts ...

  4. Front tracking for hyperbolic conservation laws

    CERN Document Server

    Holden, Helge

    2002-01-01

    Hyperbolic conservation laws are central in the theory of nonlinear partial differential equations and in science and technology. The reader is given a self-contained presentation using front tracking, which is also a numerical method. The multidimensional scalar case and the case of systems on the line are treated in detail. A chapter on finite differences is included. "It is already one of the few best digests on this topic. The present book is an excellent compromise between theory and practice. Students will appreciate the lively and accurate style." D. Serre, MathSciNet "I have read the book with great pleasure, and I can recommend it to experts as well as students. It can also be used for reliable and very exciting basis for a one-semester graduate course." S. Noelle, Book review, German Math. Soc. "Making it an ideal first book for the theory of nonlinear partial differential equations...an excellent reference for a graduate course on nonlinear conservation laws." M. Laforest, Comp. Phys. Comm.

  5. Light-Front Dynamics in Hadron Physics

    International Nuclear Information System (INIS)

    Ji, C.-R.; Bakker, B.L.G.; Choi, H.-M.

    2013-01-01

    Light-front dynamics(LFD) plays an important role in the analyses of relativistic few-body systems. As evidenced from the recent studies of generalized parton distributions (GPDs) in hadron physics, a natural framework for a detailed study of hadron structures is LFD due to its direct application in Minkowski space as well as its distinct feature of accounting for the vacuum fluctuations in quantum field theories. In the last few years, however, it has been emphasized that treacherous points such as LF singularities and zero-modes should be taken into account for successful LFD applications to hadron phenomenology. In this paper, we discuss a typical example of the contemporary relativistic hadron physics in which the fundamental issues should be taken into account for the successful application of LFD. In particular, we focus on the kinematic issue of GPDs in deeply virtual Compton scattering (DVCS). Although this fundamental issue has been glossed over in the literature, it must be taken care of for the correct analysis of DVCS data. (author)

  6. The Front Line of Genomic Translation

    International Nuclear Information System (INIS)

    O'Neill, C. S.; McBride, C. M.; Koehly, L. M.; Bryan, A. D.; Wideroff, L.

    2012-01-01

    Cancer prevention, detection, and treatment represent the front line of genomic translation. Increasingly, new genomic knowledge is being used to inform personalized cancer prevention recommendations and treatment [1-3]. Genomic applications proposed and realized span the full cancer continuum, from cancer prevention and early detection vis a vis genomic risk profiles to motivate behavioral risk reduction and adherence [4] to screening and prophylactic prevention recommendations for high-risk families [5-7], to enhancing cancer survivorship by using genomic tumor profiles to inform treatment decisions and targeted cancer therapies [8, 9]. Yet the utility for many of these applications is as yet unclear and will be influenced heavily by the public’s, patients’, and health care providers’ responses and in numerous other factors, such as health care delivery models [3]. The contributors to this special issue consider various target groups’ responses and contextual factors. To reflect the cancer continuum, the special issue is divided into three broad, overlapping themes-primary prevention, high risk families and family communication and clinical translation.

  7. FACILITATING RADICAL FRONT-END INNOVATION THROUGH TARGETED HR PRACTICES

    DEFF Research Database (Denmark)

    Aagaard, Annabeth

    2017-01-01

    This study examines how radical front end innovation can be actively facilitated through selected and targeted HR practices and bundles of HR practices. The empirical field is an explorative case study of front end innovation and HR practices in the pharmaceutical industry, with an in-depth case ...

  8. An improved front tracking method for the Euler equations

    NARCIS (Netherlands)

    Witteveen, J.A.S.; Koren, B.; Bakker, P.G.

    2007-01-01

    An improved front tracking method for hyperbolic conservation laws is presented. The improved method accurately resolves discontinuities as well as continuous phenomena. The method is based on an improved front interaction model for a physically more accurate modeling of the Euler equations, as

  9. MMIC tuned front-end for a coherent optical receiver

    DEFF Research Database (Denmark)

    Petersen, Anders Kongstad; Jagd, A. M.; Ebskamp, F.

    1993-01-01

    A low-noise transformer tuned optical front-end for a coherent optical receiver is described. The front-end is based on a GaInAs/InP p-i-n photodiode and a full custom designed GaAs monolithic microwave integrated circuit (MMIC). The measured equivalent input noise current density is between 5-16 p...

  10. Desirable forest structures for a restored Front Range

    Science.gov (United States)

    Yvette L. Dickinson; Rob Addington; Greg Aplet; Mike Babler; Mike Battaglia; Peter Brown; Tony Cheng; Casey Cooley; Dick Edwards; Jonas Feinstein; Paula Fornwalt; Hal Gibbs; Megan Matonis; Kristen Pelz; Claudia Regan

    2014-01-01

    As part of the federal Collaborative Forest Landscape Restoration Program administered by the US Forest Service, the Colorado Front Range Collaborative Forest Landscape Restoration Project (FR-CFLRP, a collaborative effort of the Front Range Roundtable1 and the US Forest Service) is required to define desired conditions for lower montane ponderosa pine (Pinus ponderosa...

  11. Stability of reaction fronts in random walk simulations

    NARCIS (Netherlands)

    Nagy, Noemi; Izsak, F.

    A model of propagating reaction fronts is given for simple autocatalytic reactions and the stability of the propagating reaction fronts are studied in several numerical experiments. The corresponding random walk simulations - extending of a recent algorithm - make possible the simultaneous treatment

  12. Formation and evolution of mesozoic volcanic basins in Gan-Hang tectonic belt

    International Nuclear Information System (INIS)

    Zhang Xingpu

    1999-01-01

    The author mainly discusses the principle model for the formation and the evolution of Mesozoic volcanic basins in the Gan-Hang Tectonic Belt, and describes the distinct evolution features between the internal and external sites of volcanic basins, the natural relation between the down-warped, down-faulted, collapse volcanic basins and volcanic domes, the relationship between the formation of inter layered fractured zones of the volcanic cover and the evolution of volcanic basins

  13. Explosive Volcanic Activity at Extreme Depths: Evidence from the Charles Darwin Volcanic Field, Cape Verdes

    Science.gov (United States)

    Kwasnitschka, T.; Devey, C. W.; Hansteen, T. H.; Freundt, A.; Kutterolf, S.

    2013-12-01

    Volcanic eruptions on the deep sea floor have traditionally been assumed to be non-explosive as the high-pressure environment should greatly inhibit steam-driven explosions. Nevertheless, occasional evidence both from (generally slow-) spreading axes and intraplate seamounts has hinted at explosive activity at large water depths. Here we present evidence from a submarine field of volcanic cones and pit craters called Charles Darwin Volcanic Field located at about 3600 m depth on the lower southwestern slope of the Cape Verdean Island of Santo Antão. We examined two of these submarine volcanic edifices (Tambor and Kolá), each featuring a pit crater of 1 km diameter, using photogrammetric reconstructions derived from ROV-based imaging followed by 3D quantification using a novel remote sensing workflow, aided by sampling. The measured and calculated parameters of physical volcanology derived from the 3D model allow us, for the first time, to make quantitative statements about volcanic processes on the deep seafloor similar to those generated from land-based field observations. Tambor cone, which is 2500 m wide and 250 m high, consists of dense, probably monogenetic medium to coarse-grained volcaniclastic and pyroclastic rocks that are highly fragmented, probably as a result of thermal and viscous granulation upon contact with seawater during several consecutive cycles of activity. Tangential joints in the outcrops indicate subsidence of the crater floor after primary emplacement. Kolá crater, which is 1000 m wide and 160 m deep, appears to have been excavated in the surrounding seafloor and shows stepwise sagging features interpreted as ring fractures on the inner flanks. Lithologically, it is made up of a complicated succession of highly fragmented deposits, including spheroidal juvenile lapilli, likely formed by spray granulation. It resembles a maar-type deposit found on land. The eruption apparently entrained blocks of MORB-type gabbroic country rocks with

  14. Ash production by attrition in volcanic conduits and plumes.

    Science.gov (United States)

    Jones, T J; Russell, J K

    2017-07-17

    Tephra deposits result from explosive volcanic eruption and serve as indirect probes into fragmentation processes operating in subsurface volcanic conduits. Primary magmatic fragmentation creates a population of pyroclasts through volatile-driven decompression during conduit ascent. In this study, we explore the role that secondary fragmentation, specifically attrition, has in transforming primary pyroclasts upon transport in volcanic conduits and plumes. We utilize total grain size distributions from a suite of natural and experimentally produced tephra to show that attrition is likely to occur in all explosive volcanic eruptions. Our experimental results indicate that fine ash production and surface area generation is fast (eruption column stability, tephra dispersal, aggregation, volcanic lightening generation, and has concomitant effects on aviation safety and Earth's climate.

  15. Explosive volcanism, shock metamorphism and the K-T boundary

    International Nuclear Information System (INIS)

    Desilva, S.L.; Sharpton, V.L.

    1988-01-01

    The issue of whether shocked quartz can be produced by explosive volcanic events is important in understanding the origin of the K-T boundary constituents. Proponents of a volcanic origin for the shocked quartz at the K-T boundary cite the suggestion of Rice, that peak overpressures of 1000 kbars can be generated during explosive volcanic eruptions, and may have occurred during the May, 1980 eruption of Mt. St. Helens. Attention was previously drawn to the fact that peak overpressures during explosive eruptions are limited by the strength of the rock confining the magma chamber to less than 8 kbars even under ideal conditions. The proposed volcanic mechanisms for generating pressures sufficient to shock quartz are further examined. Theoretical arguments, field evidence and petrographic data are presented showing that explosive volcanic eruptions cannot generate shock metamorphic features of the kind seen in minerals at the K-T boundary

  16. Global time-size distribution of volcanic eruptions on Earth.

    Science.gov (United States)

    Papale, Paolo

    2018-05-01

    Volcanic eruptions differ enormously in their size and impacts, ranging from quiet lava flow effusions along the volcano flanks to colossal events with the potential to affect our entire civilization. Knowledge of the time and size distribution of volcanic eruptions is of obvious relevance for understanding the dynamics and behavior of the Earth system, as well as for defining global volcanic risk. From the analysis of recent global databases of volcanic eruptions extending back to more than 2 million years, I show here that the return times of eruptions with similar magnitude follow an exponential distribution. The associated relative frequency of eruptions with different magnitude displays a power law, scale-invariant distribution over at least six orders of magnitude. These results suggest that similar mechanisms subtend to explosive eruptions from small to colossal, raising concerns on the theoretical possibility to predict the magnitude and impact of impending volcanic eruptions.

  17. 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

  18. Classifcation of volcanic structure in mesozoic era in the Fuzhou-Shaoxing area

    International Nuclear Information System (INIS)

    Zhang Fengqi.

    1989-01-01

    The volcanic structure in the Fuzhou-Shaoxing area can be classified into IV grades: the grade I be the zone of volcanic activity; the grade II be the second zone of volcanic activity; the grade III be the positive, negative volcanic structure; the grade IV be volcanic conduit, volcanic crater, concealed eruption breccia pipe. Based on the geological situation in this area, the different types of volcanic structure are also dealt with. In the mean time, both the embossed type in the depression area and the depressed type in the embossed area in the volcanic basin are pointed out. It is of great advantage to Uranium mineralization

  19. Volcanic sulfur dioxide index and volcanic explosivity index inferred from eruptive volume of volcanoes in Jeju Island, Korea: application to volcanic hazard mitigation

    Science.gov (United States)

    Ko, Bokyun; Yun, Sung-Hyo

    2016-04-01

    Jeju Island located in the southwestern part of Korea Peninsula is a volcanic island composed of lavaflows, pyroclasts, and around 450 monogenetic volcanoes. The volcanic activity of the island commenced with phreatomagmatic eruptions under subaqueous condition ca. 1.8-2.0 Ma and lasted until ca. 1,000 year BP. For evaluating volcanic activity of the most recently erupted volcanoes with reported age, volcanic explosivity index (VEI) and volcanic sulfur dioxide index (VSI) of three volcanoes (Ilchulbong tuff cone, Songaksan tuff ring, and Biyangdo scoria cone) are inferred from their eruptive volumes. The quantity of eruptive materials such as tuff, lavaflow, scoria, and so on, is calculated using a model developed in Auckland Volcanic Field which has similar volcanic setting to the island. The eruptive volumes of them are 11,911,534 m3, 24,987,557 m3, and 9,652,025 m3, which correspond to VEI of 3, 3, and 2, respectively. According to the correlation between VEI and VSI, the average quantity of SO2 emission during an eruption with VEI of 3 is 2-8 × 103 kiloton considering that the island was formed under intraplate tectonic setting. Jeju Island was regarded as an extinct volcano, however, several studies have recently reported some volcanic eruption ages within 10,000 year BP owing to the development in age dating technique. Thus, the island is a dormant volcano potentially implying high probability to erupt again in the future. The volcanoes might have explosive eruptions (vulcanian to plinian) with the possibility that SO2 emitted by the eruption reaches stratosphere causing climate change due to backscattering incoming solar radiation, increase in cloud reflectivity, etc. Consequently, recommencement of volcanic eruption in the island is able to result in serious volcanic hazard and this study provides fundamental and important data for volcanic hazard mitigation of East Asia as well as the island. ACKNOWLEDGMENTS: This research was supported by a grant [MPSS

  20. Volcanism in the Sumisu Rift. Pt. 2

    International Nuclear Information System (INIS)

    Hochstaedter, A.G.; Gill, J.B.; Morris, J.D.

    1990-01-01

    A bimodal suite of volcanic rocks collected from the Sumisu Rift by ALVIN provide present day example of the first magmatic products of arc rifting during the initiation of back-arc spreading. The trace element and isotopic composition of these rocks, which are contemporaneous with island arc tholeiite lavas of the Izu-Ogasawara arc 20 km to the east, differ from those of arc rocks and N-MORB in their relative incorporation of both subduction-related and non-subduction-related components. Subduction-related components, i.e., those that distinguish volcanic arc basalts from N-MORB, are less pronounced in rift lavas than in arc lavas. Alkali and alkaline earth to high field strength element and REE ratios as well as 87 Sr/ 86 Sr are intermediate between those of N-MORB and Izu arc lavas and indicate that Sumisu Rift basalts are similar to BABB erupted in other, more mature back-arc basins. These results show that back-arc basins may begin their magmatic evolution with BABB rather than more arc-like lavas. Evidence of non-subduction related components remains after the effects of subduction related components are removed or accounted for. Compared to the arc, higher HFSE and REE concentrations, contrasting REE patterns, and ≤ε Nd in the rift reflect derivation of rift lavas from more enriched components. Although SR basalt resembles E-MORB in many trace element ratios, it is referred to as BABB because low concentrations of Nb are similar to those in volcanic arcs and H 2 O/REE and H 2 O/K 2 O exceed those of E-MORB. Differences in HREE pattern and ε Nd require that the E-MORB characteristics result from source heterogeneities and not lower degrees of melting. Enriched mantle beneath the rift may reflect enriched blobs entrained in a more depleted matrix, or injection of new, more enriched mantle. High 208 Pb/ 204 Pb and moderate 207 Pb/ 204 Pb ratios with respect to Pacific MORB also reflect ancient mantle enrichment. (orig.)

  1. Sill intrusion in volcanic calderas: implications for vent opening probability

    Science.gov (United States)

    Giudicepietro, Flora; Macedonio, Giovanni; Martini, Marcello; D'Auria, Luca

    2017-04-01

    Calderas show peculiar behaviors with remarkable dynamic processes, which do not often culminate in eruptions. Observations and studies conducted in recent decades have shown that the most common cause of unrest in the calderas is due to magma intrusion; in particular, the intrusion of sills at shallow depths. Monogenic cones, with large areal dispersion, are quite common in the calderas, suggesting that the susceptibility analysis based on geological features, is not strictly suitable for estimating the vent opening probability in calderas. In general, the opening of a new eruptive vent can be regarded as a rock failure process. The stress field in the rocks that surrounds and tops the magmatic reservoirs plays an important role in causing the rock failure and creating the path that magma can follow towards the surface. In this conceptual framework, we approach the problem of getting clues about the probability of vent opening in volcanic calderas through the study of the stress field produced by the intrusion of magma, in particular, by the intrusion of a sill. We simulate the intrusion of a sill free to expand radially, with shape and dimensions which vary with time. The intrusion process is controlled by the elastic response of the rock plate above the sill, which bends because of the intrusion, and by gravity, that drives the magma towards the zones where the thickness of the sill is smaller. We calculated the stress field in the plate rock above the sill. We found that at the bottom of the rock plate above the sill the maximum intensity of tensile stress is concentrated at the front of the sill and spreads radially with it, over time. For this reason, we think that the front of the spreading sill is prone to open for eruptive vents. Even in the central area of the sill the intensity of stress is relatively high, but at the base of the rock plate stress is compressive. Under isothermal conditions, the stress soon reaches its maximum value (time interval

  2. Volcanism Studies: Final Report for the Yucca Mountain Project

    Energy Technology Data Exchange (ETDEWEB)

    Bruce M. Crowe; Frank V. Perry; Greg A. Valentine; Lynn M. Bowker

    1998-12-01

    This report synthesizes the results of volcanism studies conducted by scientists at the Los Alamos National Laboratory and collaborating institutions on behalf of the Department of Energy's Yucca Mountain Project. An assessment of the risk of future volcanic activity is one of many site characterization studies that must be completed to evaluate the Yucca Mountain site for potential long-term storage of high-level radioactive waste. The presence of several basaltic volcanic centers in the Yucca Mountain region of Pliocene and Quaternary age indicates that there is a finite risk of a future volcanic event occurring during the 10,000-year isolation period of a potential repository. Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The risk of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Future volcanic events cannot be predicted with certainty but instead are estimated using formal methods of probabilistic volcanic hazard assessment (PVHA). Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The distribution, eruptive history, and geochronology of Plio-Quaternary basalt centers are described by individual center emphasizing the younger postcaldera basalt (<5 Ma). The Lathrop Wells volcanic center is described in detail because it is the youngest basalt center in the YMR. The age of the Lathrop Wells center is now confidently determined to be about 75 thousand years old. Chapter 3 describes the tectonic setting of the YMR and presents and assesses the significance of multiple alternative tectonic models. The Crater Flat volcanic zone is

  3. Cluster Observations of Multiple Dipolarization Fronts

    Science.gov (United States)

    Hwang, Kyoung-Joo; Goldstein, Melvyn L.; Lee, Ensang; Pickett, Jolene S.

    2011-01-01

    We present Cluster observations of a series of dipolarization fronts (DF 1 to 6) at the central current sheet in Earth's magnetotail. The velocities of fast earthward flow following behind each DF 1-3, are comparable to the Alfven velocity, indicating that the flow bursts might have been generated by bursty reconnection that occurred tailward of the spacecraft. Based on multi-spacecraft timing analysis, DF normals are found to propagate mainly earthward at $160-335$ km/s with a thickness of 900-1500 km, which corresponds to the ion inertial length or gyroradius scale. Each DF is followed by significant fluctuations in the $x$ and $y$ components of the magnetic field whose peaks are found 1-2 minutes after the DF passage. These $(B_{x},B_{y} )$-fluctuations propagate dawnward (mainly) and earthward. Strongly enhanced field-aligned beams are observed coincidently with $(B_{x},B_{y})$ fluctuations, while an enhancement of cross-tail currents is associated with the DFs. From the observed pressure imbalance and flux-tube entropy changes between the two regions separated by the DF, we speculate that interchange instability destabilizes the DFs and causes the deformation of the mid-tail magnetic topology. This process generates significant field-aligned currents, and might power the auroral brightening in the ionosphere. However, this event is neither associated with the main substorm auroral breakup nor the poleward expansion, which might indicate that the observed multiple DFs have been dissipated before they reach the inner plasma sheet boundary.

  4. Iu. Ushakov & A. Stukalov, Front voennykh prokurorov [The Military Procurators’ Front], Moskva, Viatka, 2000, 223 pages.

    Directory of Open Access Journals (Sweden)

    Vanessa Voisin

    2008-07-01

    Full Text Available Front voennykh prokurorov is a collection of essays written by two writers who are not known as specialists of military history, but obviously have access to archives, as proves the reprint, in the middle of the book, of several pages from the personal files of Afanas’ev, former Main Military Prosecutor of Soviet Armed Forces.The first part of the book is devoted to Nikolai Porfir’evich Afanas’ev’s memoirs, written, according to the editors, after his retirement in 1950. Afanas’ev, though les...

  5. Tungsten abundances in some volcanic rocks

    International Nuclear Information System (INIS)

    Helsen, J.N.; Shaw, D.M.; Crocket, J.H.

    1978-01-01

    A radiochemical N.A.A. method was used to obtain new values on W distribution in some 125 volcanic rocks, mainly basalts and andesites, from different petrotectonic environments. These W data are below previously reported abundances. New median values in various types of rocks are suggested (ppm W). Basalts: ocean floor, 0.15; ocean islands subalkaline, 0.28; ocean islands alkaline, 0.60; island arc, 0.19; continental margin, 0.40; continental subalkaline, 0.30; continental alkaline, 1.35. Andesites: island arc, 0.23; continental margin, 1.05. Median values for all 91 basalts and all 20 andesites are 0.36 and 0.29 ppm respectively. (author)

  6. Inside the volcanic boiler room: knowledge exchange among stakeholders of volcanic unrest

    Science.gov (United States)

    Gottsmann, Joachim; Christie, Ryerson; Bretton, Richard

    2014-05-01

    The knowledge of the causative links between subsurface processes, resulting monitoring signals and imminent eruption is incomplete. As a consequence, hazard assessment and risk mitigation strategies are subject to uncertainty. Discussion of unrest and pre-eruptive scenarios with uncertain outcomes are central during the discourse between a variety of stakeholders in volcanic unrest including scientists, emergency managers, policy makers and the public. Drawing from research within the EC FP7 VUELCO project, we argue that knowledge exchange amongst the different stakeholders of volcanic unrest evolves along three dimensions: 1) the identification of knowledge holders (including local communities) and their needs and expectations, 2) vehicles of communication and 3) trust. In preparing products that feed into risk assessment and management, scientists need to ensure that their deliverables are timely, accurate, clear, understandable and cater to the expectations of emergency managers. The means and content of communication amongst stakeholders need to be defined and adhered to. Finally, efficient and effective interaction between stakeholders is ideally based on mutual trust between those that generate knowledge and those that receive knowledge. For scientists, this entails contextualising volcanic hazard and risk in the framework of environmental and social values. Periods of volcanic quiescence are ideally suited to test established protocols of engagement between stakeholders in preparation for crises situations. The different roles of stakeholders and associated rules of engagement can be scrutinised and reviewed in antecessum rather than ad-hoc during a crisis situation to avoid issues related to distrust, loss of credibility and overall poor risk management. We will discuss these themes drawing from exploitation of research results from Mexico and Ecuador.

  7. The monogenetic Bayuda Volcanic Field, Sudan - New insights into geology and volcanic morphology

    Science.gov (United States)

    Lenhardt, Nils; Borah, Suranjana B.; Lenhardt, Sukanya Z.; Bumby, Adam J.; Ibinoof, Montasir A.; Salih, Salih A.

    2018-05-01

    The small monogenetic Bayuda Volcanic Field (BVF; 480 km2), comprising at least 53 cinder cones and 15 maar volcanoes in the Bayuda desert of northern Sudan is one of a few barely studied volcanic occurrences of Quaternary age in Sudan. The exact age of the BVF and the duration of volcanic activity has not yet been determined. Furthermore, not much is known about the eruptional mechanisms and the related magmatic and tectonic processes that led to the formation of the volcanic field. In the framework of a larger project focusing on these points it is the purpose of this contribution to provide a first account of the general geology of the BVF volcanoes as well as a first description of a general stratigraphy, including a first description of their morphological characteristics. This was done by means of fieldwork, including detailed rock descriptions, as well as the analysis of satellite images (SRTM dataset at 30 m spatial resolution). The BVF cinder cones are dominated by scoracious lapilli tephra units, emplaced mainly by pyroclastic fallout from Strombolian eruptions. Many cones are breached and are associated with lava flows. The subordinate phreatomagmatism represented by maar volcanoes suggests the presence of ground and/or shallow surface water during some of the eruptions. The deposits constituting the rims around the maar volcanoes are interpreted as having mostly formed due to pyroclastic surges. Many of the tephra rings around the maars are underlain by thick older lava flows. These are inferred to be the horizons where rising magma interacted with groundwater. The existence of phreatomagmatic deposits may point to a time of eruptive activity during a phase with wetter conditions and therefore higher groundwater levels than those encountered historically. This is supported by field observations as well as the morphological analysis, providing evidence for relatively high degrees of alteration of the BVF volcanoes and therefore older eruption ages as

  8. 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.

  9. Detecting Volcanic Ash Plumes with GNSS Signals

    Science.gov (United States)

    Rainville, N.; Larson, K. M.; Palo, S. E.; Mattia, M.; Rossi, M.; Coltelli, M.; Roesler, C.; Fee, D.

    2016-12-01

    Global Navigation Satellite Systems (GNSS) receivers are commonly placed near volcanic sites to measure ground deformation. In addition to the carrier phase data used to measure ground position, these receivers also record Signal to Noise ratio (SNR) data. Larson (2013) showed that attenuations in SNR data strongly correlate with ash emissions at a series of eruptions of Redoubt Volcano. This finding has been confirmed at eruptions for Tongariro, Mt Etna, Mt Shindake, and Sakurajima. In each of these detections, very expensive geodetic quality GNSS receivers were used. If low-cost GNSS instruments could be used instead, a networked array could be deployed and optimized for plume detection and tomography. The outputs of this sensor array could then be used by both local volcanic observatories and Volcano Ash Advisory Centers. Here we will describe progress in developing such an array. The sensors we are working with are intended for navigation use, and thus lack the supporting power and communications equipment necessary for a networked system. Reliably providing those features is major challenge for the overall sensor design. We have built prototypes of our Volcano Ash Plume Receiver (VAPR), with solar panels, lithium-ion batteries and onboard data storage for preliminary testing. We will present results of our field tests of both receivers and antennas. A second critical need for our array is a reliable detection algorithm. We have tested our algorithm on data from recent eruptions and have incorporated the noise characteristics of the low-cost GNSS receiver. We have also developed a simulation capability so that the receivers can be deployed to optimize vent crossing GNSS signals.

  10. Chemical deposits in volcanic caves of Argentina

    Directory of Open Access Journals (Sweden)

    Carlos Benedetto

    1998-01-01

    Full Text Available During the last Conference of the FEALC (Speleological Federation of Latin America and Caribbean Islands which was held in the town of Malargue, Mendoza, in February 1997, two volcanic caves not far from that town were visited and sampled for cave mineral studies. The first cave (Cueva del Tigre opens close to the Llancanelo lake, some 40 kms far from Malargue and it is a classical lava tube. Part of the walls and of the fallen lava blocks are covered by white translucent fibres and grains. The second visited cave is a small tectonic cavity opened on a lava bed some 100 km southward of Malargue. The cave “El Abrigo de el Manzano” is long no more than 10-12 meters with an average width of 3 meters and it hosts several bird nests, the larger of which is characterized by the presence of a relatively thick pale yellow, pale pink flowstone. Small broken or fallen samples of the secondary chemical deposits of both these caves have been collected in order to detect their mineralogical composition. In the present paper the results of the detailed mineralogical analyses carried out on the sampled material are shortly reported. In the Cueva del Tigre lava tube the main detected minerals are Sylvite, Thenardite, Bloedite and Kieserite, all related to the peculiar dry climate of that area. The flowstone of “El Abrigo de el Manzano” consists of a rather complex admixture of several minerals, the large majority of which are phosphates but also sulfates and silicates, not all yet identified. The origin of all these minerals is related to the interaction between bird guano and volcanic rock.

  11. Global volcanic earthquake swarm database and preliminary analysis of volcanic earthquake swarm duration

    Directory of Open Access Journals (Sweden)

    S. R. McNutt

    1996-06-01

    Full Text Available Global data from 1979 to 1989 pertaining to volcanic earthquake swarms have been compiled into a custom-designed relational database. The database is composed of three sections: 1 a section containing general information on volcanoes, 2 a section containing earthquake swarm data (such as dates of swarm occurrence and durations, and 3 a section containing eruption information. The most abundant and reliable parameter, duration of volcanic earthquake swarms, was chosen for preliminary analysis. The distribution of all swarm durations was found to have a geometric mean of 5.5 days. Precursory swarms were then separated from those not associated with eruptions. The geometric mean precursory swarm duration was 8 days whereas the geometric mean duration of swarms not associated with eruptive activity was 3.5 days. Two groups of precursory swarms are apparent when duration is compared with the eruption repose time. Swarms with durations shorter than 4 months showed no clear relationship with the eruption repose time. However, the second group, lasting longer than 4 months, showed a significant positive correlation with the log10 of the eruption repose period. The two groups suggest that different suites of physical processes are involved in the generation of volcanic earthquake swarms.

  12. The Te Rere and Okareka eruptive episodes : Okataina Volcanic Centre, Taupo Volcanic Zone, New Zealand

    International Nuclear Information System (INIS)

    Nairn, I.A.

    1992-01-01

    The Te Rere and Okareka eruptive episodes occurred within the Okataina Volcanic Centre at c. 21 000 and 18 000 yr B.P., respectively. The widespread rhyolitic pumice fall deposits of Te Rere Ash (volume 5 km 3 ) and Okareka Ash (6 km 3 ) are only rarely exposed in near-source areas, and locations of their vent areas have been uncertain. New exposures and petrographic and chemical analyses show that the Te Rere episode eruptions occurred from multiple vents, up to 20 km apart, on the Haroharo linear vent zone. The Okareka episode eruptions occurred from vents since buried beneath the Tarawera volcanic massif. Eruption of the rhyolitic Okareka pumice fall was immediately preceded by a small basaltic scoria eruption, apparently from vents close to those for the following rhyolite eruptions. Dacitic mixed pumices scattered within the rhyolite pumice layers immediately overlying the scoria were formed by mixing of the basalt and rhyolite magmas. The Te Rere and Okareka pyroclastic eruptions were both followed by extrusion of voluminous rhyolite lavas. These eruptive episodes mark the commencement of growth of the present-day Haroharo and Tarawera volcanic complexes. (author). 27 refs., 14 figs., 6 tabs

  13. Simulating the Evolving Behavior of Secondary Slow Slip Fronts

    Science.gov (United States)

    Peng, Y.; Rubin, A. M.

    2017-12-01

    High-resolution tremor catalogs of slow slip events reveal secondary slow slip fronts behind the main front that repetitively occupy the same source area during a single episode. These repetitive fronts are most often observed in regions with high tremor density. Their recurrence intervals gradually increase from being too short to be tidally modulated (tens of minutes) to being close to tidal periods (about 12 or 24 hours). This could be explained by a decreasing loading rate from creep in the surrounding regions (with few or no observable tremor events) as the main front passes by. As the recurrence intervals of the fronts increase, eventually they lock in on the tidal periods. We attempt to simulate this numerically using a rate-and-state friction law that transitions from velocity-weakening at low slip speeds to velocity strengthening at high slip speeds. Many small circular patches with a cutoff velocity an order of magnitude higher than that of the background are randomly placed on the fault, in order to simulate the average properties of the high-density tremor zone. Preliminary results show that given reasonable parameters, this model produces similar propagation speeds of the forward-migrating main front inside and outside the high-density tremor zone, consistent with observations. We will explore the behavior of the secondary fronts that arise in this model, in relation to the local density of the small tremor-analog patches, the overall geometry of the tremor zone and the tides.

  14. Hindrances to bistable front propagation: application to Wolbachia invasion.

    Science.gov (United States)

    Nadin, Grégoire; Strugarek, Martin; Vauchelet, Nicolas

    2018-05-01

    We study the biological situation when an invading population propagates and replaces an existing population with different characteristics. For instance, this may occur in the presence of a vertically transmitted infection causing a cytoplasmic effect similar to the Allee effect (e.g. Wolbachia in Aedes mosquitoes): the invading dynamics we model is bistable. We aim at quantifying the propagules (what does it take for an invasion to start?) and the invasive power (how far can an invading front go, and what can stop it?). We rigorously show that a heterogeneous environment inducing a strong enough population gradient can stop an invading front, which will converge in this case to a stable front. We characterize the critical population jump, and also prove the existence of unstable fronts above the stable (blocking) fronts. Being above the maximal unstable front enables an invading front to clear the obstacle and propagate further. We are particularly interested in the case of artificial Wolbachia infection, used as a tool to fight arboviruses.

  15. Catastrophic debris flows transformed from landslides in volcanic terrains : mobility, hazard assessment and mitigation strategies

    Science.gov (United States)

    Scott, Kevin M.; Macias, Jose Luis; Naranjo, Jose Antonio; Rodriguez, Sergio; McGeehin, John P.

    2001-01-01

    precipitation, as well as magmatic activity and eruptions. (3) Risk of collapse begins with initial magmatic activity and increases as intrusion proceeds. An archetypal debris flow from volcanic terrain occurred in Colombia with a tectonic earthquake (M 6.4) in 1994. The Rio Piez conveyed a catastrophic wave of debris flow over 100 kilometers, coalesced from multiple slides of surflcial material weakened both by weathering and by hydrothermal alteration in a large strato- volcano. Similar seismogenic flows occurred in Mexico in 1920 (M -6.5), Chile in 1960 (M 9.2), and Ecuador in 1987 (M 6.1 and 6.9). Velocities of wave fronts in two examples were 60 to 90 km/hr (17-25 meters per second) over the initial 30 kilometers. Volcano flank and sector collapses may produce untransformed debris avalanches, as occurred initially at Mount St. Helens in 1980. However, at least as common is direct transformation of the failed mass to a debris flow. At two other volcanoes in the Cascade Range-- Mount Rainier and Mount Baker--rapid transformation and high mobility were typical of most of at least 15 Holocene flows. This danger exists downstream from many stratovolcanoes worldwide; the population at risk is near 150,000 and increasing at Mount Rainier. The first step in preventing future catastrophes is documenting past flows. Deposits of some debris flows, however, can be mistaken for those of less-mobile debris avalanches on the basis of mounds formed by buoyed megaclasts. Megaclasts may record only the proximal phase of a debris flow that began as a debris avalanche. Runout may have extended much farther, and thus furore flow mobility may be underestimated. Processes and behaviors of megaclast-bearing paleoflows are best inferred from the intermegaclast matrix. Mitigation strategy can respond to volcanic flows regardless of type and trigger by: (1) Avoidance: Limit settlement in flow pathways to numbers that can be evacuated after event warnings (flow is occurring). (2) Instrumental even

  16. Park Volcanics, Murihiku Terrane, New Zealand : petrology, petrochemistry, and tectonic significance

    International Nuclear Information System (INIS)

    Coombs, D.S.; Cook, N.D.J.; Kawachi, Y.; Johnstone, R.D.; Gibson, I.L.

    1996-01-01

    established forearc basins whereas they are characteristic of back-arc sites. At the time of emplacement of the Park Volcanics, the southern Murihiku sedimentary basin is therefore unlikely to have occupied a forearc setting. The volcanic arc that provided detritus and ash deposits to the basin at that time was probably sited on a strip of largely Proterozoic continental crust detached from the Gondwana mainland by a marginal sea with a subduction zone dipping away from that marginal sea under the volcanic arc, with the Murihiku sedimentary basin towards the rear on the proto-Pacific side. Drumduan Group, with a low-temperature, high-pressure metamorphic overprint, and other largely volcaniclastic terrane fragments in the Median Tectonic Zone of southern New Zealand, may be arc-front remnants of the same arc system. (author). 59 refs., 18 figs., 11 tabs

  17. What, When, Where, and Why of Secondary Hawaiian Hotspot Volcanism

    Science.gov (United States)

    Garcia, M. O.; Ito, G.; Applegate, B.; Weis, D.; Swinnard, L.; Flinders, A.; Hanano, D.; Nobre-Silva, I.; Bianco, T.; Naumann, T.; Geist, D.; Blay, C.; Sciaroni, L.; Maerschalk, C.; Harpp, K.; Christensen, B.

    2007-12-01

    Secondary hotspot volcanism occurs on most oceanic island groups (Hawaii, Canary, Society) but its origins remain enigmatic. A 28-day marine expedition used multibeam bathymetry and acoustic imagery to map the extent of submarine volcanic fields around the northern Hawaiian Islands (Kauai, Niihau and Kaula), and the JASON2 ROV to sample many volcanoes to characterize the petrology, geochemistry (major and trace elements, and isotopes) and ages of the lavas from these volcanoes. Our integrated geological, geochemical and geophysical study attempts to examine the what (compositions and source), where (distribution and volumes), when (ages), and why (mechanisms) of secondary volcanism on and around the northern Hawaiian Islands. A first-order objective was to establish how the submarine volcanism relates in space, time, volume, and composition to the nearby shield volcanoes and their associated onshore secondary volcanism. Our surveying and sampling revealed major fields of submarine volcanoes extending from the shallow slopes of these islands to more than 100 km offshore. These discoveries dramatically expand the volumetric importance, distribution and geodynamic framework for Hawaiian secondary volcanism. New maps and rock petrology on the samples collected will be used to evaluate currently proposed mechanisms for secondary volcanism and to consider new models such as small-scale mantle convection driven by thermal and melt-induced buoyancy to produce the huge volume of newly discovered lava. Our results seem to indicate substantial revisions are needed to our current perceptions of hotspot dynamics for Hawaii and possibly elsewhere.

  18. 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.

  19. Volcanic hazard studies for the Yucca Mountain project

    International Nuclear Information System (INIS)

    Crowe, B.; Turrin, B.; Wells, S.; Perry, F.; McFadden, L.; Renault, C.E.; Champion, D.; Harrington, C.

    1989-01-01

    Volcanic hazard studies are ongoing to evaluate the risk of future volcanism with respect to siting of a repository for disposal of high-level radioactive waste at the Yucca Mountain site. Seven Quaternary basaltic volcanic centers are located a minimum distance of 12 km and a maximum distance of 47 km from the outer boundary of the exploration block. The conditional probability of disruption of a repository by future basaltic volcanism is bounded by the range of 10/sup /minus/8/ to 10/sup /minus/10/ yr/sup /minus/1/. These values are currently being reexamined based on new developments in the understanding of the evaluation of small volume, basaltic volcanic centers including: (1) Many, perhaps most, of the volcanic centers exhibit brief periods of eruptive activity separated by longer periods of inactivity. (2) The centers may be active for time spans exceeding 10 5 yrs, (3) There is a decline in the volume of eruptions of the centers through time, and (4) Small volume eruptions occurred at two of the Quaternary centers during latest Pleistocene or Holocene time. We classify the basalt centers as polycyclic, and distinguish them from polygenetic volcanoes. Polycyclic volcanism is characterized by small volume, episodic eruptions of magma of uniform composition over time spans of 10 3 to 10 5 yrs. Magma eruption rates are low and the time between eruptions exceeds the cooling time of the magma volumes. 25 refs., 2 figs

  20. Lunar cryptomaria: Physical characteristics, distribution, and implications for ancient volcanism

    Science.gov (United States)

    Whitten, Jennifer L.; Head, James W.

    2015-02-01

    Cryptomaria, lunar volcanic deposits obscured by crater and basin impact ejecta, can provide important information about the thermal and volcanic history of the Moon. The timing of cryptomare deposition has implications for the duration and flux of mare basalt volcanism. In addition, knowing the distribution of cryptomaria can provide information about mantle convection and lunar magma ocean solidification. Here we use multiple datasets (e.g., M3, LOLA, LROC, Diviner) to undertake a global analysis to identify the general characteristics (e.g., topography, surface roughness, rock abundance, albedo, etc.) of lunar light plains in order to better distinguish between ancient volcanic deposits (cryptomaria) and impact basin and crater ejecta deposits. We find 20 discrete regions of cryptomaria, covering approximately 2% of the Moon, which increase the total area covered by mare volcanism to 18% of the lunar surface. Comparisons of light plains deposits indicate that the two deposit types (volcanic and impact-produced) are best distinguished by mineralogic data. On the basis of cryptomaria locations, the distribution of mare volcanism does not appear to have changed in the time prior to its exposed mare basalt distribution. There are several hypotheses explaining the distribution of mare basalts, which include the influence of crustal thickness, mantle convection patterns, asymmetric distribution of source regions, KREEP distribution, and the influence of a proposed Procellarum impact basin. The paucity of farside mare basalts means that multiple factors, such as crustal thickness variations and mantle convection, are likely to play a role in mare basalt emplacement.

  1. Submarine Volcanic Eruptions and Potential Analogs for Venus

    Science.gov (United States)

    Wilson, L.; Mouginismark, P. J.; Fryer, P.; Gaddis, L. R.

    1985-01-01

    As part of an analysis program to better understand the diversity of volcanic processes on the terrestrial planets, an investigation of the volcanic landforms which exist on the Earth's ocean floor was initiated. In part, this analysis is focused toward gaining a better understanding of submarine volcanic landforms in their own right, but also it is hoped that these features may show similarities to volcanic landforms on Venus, due to the high ambient water (Earth) and atmospheric (Venus) pressures. A series of numerical modelling experiments was performed to investigate the relative importance of such attributes as water pressure and temperature on the eruption process, and to determine the rate of cooling and emplacement of lava flows in the submarine environment. Investigations to date show that the confining water pressure and the buoyancy effects of the surrounding water significantly affect the styles of volcanism on the ocean floor. In the case of Venusian volcanism, confining pressures will not be as great as that found at the ocean's abyssal plains, but nevertheless the general trend toward reducing magma vesiculation will hold true for Venus as well as the ocean floor. Furthermore, other analogs may also be found between submarine volcanism and Venusian activity.

  2. Spin-1 particles with light-front approach

    Directory of Open Access Journals (Sweden)

    de Melo J.P.B.C.

    2014-06-01

    Full Text Available For the vector sector, i.e, mesons with spin-1, the electromagnetic form factors and anothers observables are calculated with the light-front approach. However, the light-front quantum field theory have some problems, for example, the rotational symmetry breaking. We solve that problem added the zero modes contribuition to the matrix elements of the electromagnetic current, besides the valence contribuition. We found that among the four independent matrix elements of the plus component in the light-front helicity basis only the 0 → 0 one carries zero mode contributions.

  3. Determination of cut front position in laser cutting

    International Nuclear Information System (INIS)

    Pereira, M; Thombansen, U

    2016-01-01

    Laser cutting has a huge importance to manufacturing industry. Laser cutting machines operate with fixed technological parameters and this does not guarantee the best productivity. The adjustment of the cutting parameters during operation can improve the machine performance. Based on a coaxial measuring device it is possible to identify the cut front position during the cutting process. This paper describes the data analysis approach used to determine the cut front position for different feed rates. The cut front position was determined with good resolution, but improvements are needed to make the whole process more stable. (paper)

  4. Adaptive RF front-ends for hand-held applications

    CERN Document Server

    van Bezooijen, Andre; van Roermund, Arthur

    2010-01-01

    The RF front-end - antenna combination is a vital part of a mobile phone because its performance is very relevant to the link quality between hand-set and cellular network base-stations. The RF front-end performance suffers from changes in operating environment, like hand-effects, that are often unpredictable. ""Adaptive RF Front-Ends for Hand-Held Applications"" presents an analysis on the impact of fluctuating environmental parameters. In order to overcome undesired behavior two different adaptive control methods are treated that make RF frond-ends more resilient: adaptive impedance control,

  5. Light-front field theory in the description of hadrons

    Science.gov (United States)

    Ji, Chueng-Ryong

    2017-03-01

    We discuss the use of light-front field theory in the descriptions of hadrons. In particular, we clarify the confusion in the prevailing notion of the equivalence between the infinite momentum frame and the light-front dynamics and the advantage of the light-front dynamics in hadron physics. As an application, we present our recent work on the flavor asymmetry in the proton sea and identify the presence of the delta-function contributions associated with end-point singularities arising from the chiral effective theory calculation. The results pave the way for phenomenological applications of pion cloud models that are manifestly consistent with the chiral symmetry properties of QCD.

  6. Chaos of radiative heat-loss-induced flame front instability.

    Science.gov (United States)

    Kinugawa, Hikaru; Ueda, Kazuhiro; Gotoda, Hiroshi

    2016-03-01

    We are intensively studying the chaos via the period-doubling bifurcation cascade in radiative heat-loss-induced flame front instability by analytical methods based on dynamical systems theory and complex networks. Significant changes in flame front dynamics in the chaotic region, which cannot be seen in the bifurcation diagrams, were successfully extracted from recurrence quantification analysis and nonlinear forecasting and from the network entropy. The temporal dynamics of the fuel concentration in the well-developed chaotic region is much more complicated than that of the flame front temperature. It exhibits self-affinity as a result of the scale-free structure in the constructed visibility graph.

  7. Time-delayed fronts from biased random walks

    International Nuclear Information System (INIS)

    Fort, Joaquim; Pujol, Toni

    2007-01-01

    We generalize a previous model of time-delayed reaction-diffusion fronts (Fort and Mendez 1999 Phys. Rev. Lett. 82 867) to allow for a bias in the microscopic random walk of particles or individuals. We also present a second model which takes the time order of events (diffusion and reproduction) into account. As an example, we apply them to the human invasion front across the USA in the 19th century. The corrections relative to the previous model are substantial. Our results are relevant to physical and biological systems with anisotropic fronts, including particle diffusion in disordered lattices, population invasions, the spread of epidemics, etc

  8. Gluon cascades and amplitudes in light-front perturbation theory

    International Nuclear Information System (INIS)

    Cruz-Santiago, C.A.; Staśto, A.M.

    2013-01-01

    We construct the gluon wave functions, fragmentation functions and scattering amplitudes within the light-front perturbation theory. Recursion relations on the light-front are constructed for the wave functions and fragmentation functions, which in the latter case are the light-front analogs of the Berends–Giele recursion relations. Using general relations between wave functions and scattering amplitudes it is demonstrated how to obtain the maximally-helicity violating amplitudes, and explicit verification of the results is based on simple examples.

  9. Determination of cut front position in laser cutting

    Science.gov (United States)

    Pereira, M.; Thombansen, U.

    2016-07-01

    Laser cutting has a huge importance to manufacturing industry. Laser cutting machines operate with fixed technological parameters and this does not guarantee the best productivity. The adjustment of the cutting parameters during operation can improve the machine performance. Based on a coaxial measuring device it is possible to identify the cut front position during the cutting process. This paper describes the data analysis approach used to determine the cut front position for different feed rates. The cut front position was determined with good resolution, but improvements are needed to make the whole process more stable.

  10. Lidar detection of carbon dioxide in volcanic plumes

    Science.gov (United States)

    Fiorani, Luca; Santoro, Simone; Parracino, Stefano; Maio, Giovanni; Del Franco, Mario; Aiuppa, Alessandro

    2015-06-01

    Volcanic gases give information on magmatic processes. In particular, anomalous releases of carbon dioxide precede volcanic eruptions. Up to now, this gas has been measured in volcanic plumes with conventional measurements that imply the severe risks of local sampling and can last many hours. For these reasons and for the great advantages of laser sensing, the thorough development of volcanic lidar has been undertaken at the Diagnostics and Metrology Laboratory (UTAPRAD-DIM) of the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA). In fact, lidar profiling allows one to scan remotely volcanic plumes in a fast and continuous way, and with high spatial and temporal resolution. Two differential absorption lidar instruments will be presented in this paper: BILLI (BrIdge voLcanic LIdar), based on injection seeded Nd:YAG laser, double grating dye laser, difference frequency mixing (DFM) and optical parametric amplifier (OPA), and VULLI (VULcamed Lidar), based on injection seeded Nd:YAG laser and optical parametric oscillator (OPO). The first one is funded by the ERC (European Research Council) project BRIDGE and the second one by the ERDF (European Regional Development Fund) project VULCAMED. While VULLI has not yet been tested in a volcanic site, BILLI scanned the gas emitted by Pozzuoli Solfatara (Campi Flegrei volcanic area, Naples, Italy) during a field campaign carried out from 13 to 17 October 2014. Carbon dioxide concentration maps were retrieved remotely in few minutes in the crater area. Lidar measurements were in good agreement with well-established techniques, based on different operating principles. To our knowledge, it is the first time that carbon dioxide in a volcanic plume is retrieved by lidar, representing the first direct measurement of this kind ever performed on an active volcano and showing the high potential of laser remote sensing in geophysical research.

  11. Volcanic hazards of North Island, New Zealand-overview

    Science.gov (United States)

    Dibble, R. R.; Nairn, I. A.; Neall, V. E.

    1985-10-01

    In October 1980, a National Civil Defence Planning Committee on Volcanic Hazards was formed in New Zealand, and solicited reports on the likely areas and types of future eruptions, the risk to public safety, and the need for special precautions. Reports for eight volcanic centres were received, and made available to the authors. This paper summarises and quantifies the type and frequency of hazard, the public risk, and the possibilities for mitigation at the 7 main volcanic centres: Northland, Auckland, White Island, Okataina, Taupo, Tongariro, and Egmont. On the basis of Recent tephrostratigraphy, eruption probabilities up to 20% per century (but commonly 5%), and tephra volumes up to 100 km 3 are credible.

  12. Volcanic ash as fertiliser for the surface ocean

    Directory of Open Access Journals (Sweden)

    B. Langmann

    2010-04-01

    Full Text Available Iron is a key limiting micro-nutrient for marine primary productivity. It can be supplied to the ocean by atmospheric dust deposition. Volcanic ash deposition into the ocean represents another external and so far largely neglected source of iron. This study demonstrates strong evidence for natural fertilisation in the iron-limited oceanic area of the NE Pacific, induced by volcanic ash from the eruption of Kasatochi volcano in August 2008. Atmospheric and oceanic conditions were favourable to generate a massive phytoplankton bloom in the NE Pacific Ocean which for the first time strongly suggests a connection between oceanic iron-fertilisation and volcanic ash supply.

  13. 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

  14. Glacial evolution of the Ampato Volcanic Complex (Peru)

    Science.gov (United States)

    Alcalá, J.; Palacios, D.; Zamorano, J. J.; Vázquez, L.

    2009-04-01

    these climatic conditions, glaciers expanded and their fronts descended to a minimum altitude of 3900 m a.s.l. in the Huayuray valley. The ELA was at 4980 m a.s.l., implying an ELA depression of 900 m compared to the situation in 2000 AD. The age obtained for the Ampato Volcanic Complex using cosmogenic methods is 16,500 ± 0.37 y. AP, similar to the dates proposed by Clapperton (1993) - around 18,800 y. BP-, and far away from those proposed by Seltzer (2002) -30,000 y. BP- or by Smith et al. (2005) -21,000 y. BP-, although there is no certainty that the samples represent the oldest ridges of this period. Several records exist of Neoglacial advances, mainly well preserved moraines located in the glacial valleys immediately behind LGM moraines. One of these reached a minimum altitude of 4300 m a.s.l., with the ELA at 5240 m a.s.l., which implies an ELA depression of 560 m compared to the 2000 AD situation. 36Cl dating indicates that this Neoglacial advance occurred in 11,400 ± 0.21 y. BP. Two main glacial readvancement events due to climatic conditions have been noted in the Central Andes: The first between 15,000 and 13,000 yr. BP and the second at 12,000-10,000 yr. BP (Clapperton, 1993; Zech, et al., 2007). The latter has been dated with sufficient precision on the Chimborazo (Ecuador), the Junin Plains (Peru), and the Quelccaya Glacier (Peru) (Clapperton, 1993; Seltzer, 1990 and Smith et al. 2005) and corresponds to the described event in the Ampato Complex. There is limited data on the Little Ice Age for the Central Andes. This phase is represented by small moraines, located at high altitudes, very near the current glacial fronts. Ice cores extracted from some Central Andean glaciers, such as the Quelccaya Glacier (Peru), show a cooling episode between 1500 and 1820 AD, which corresponds to the LIA (Seltzer, 1990). During this recent global cold event, the minimum altitude of glaciers on the Ampato Volcanic Complex reached 5400 m a.s.l., 250 m below their 2000

  15. Relvakogujad sõjaajalooklubist Front Line vahistati / Kadri Ratt

    Index Scriptorium Estoniae

    Ratt, Kadri

    2009-01-01

    Kaitsepolitsei võttis vahi alla 9 meest, keda kahtlustatakse suures koguses lõhkeainete, lõhkekehade ja tulirelvade ebaseaduslikus käitlemises. 6 meest neist kuuluvad sõjaajalooklubisse Front Line

  16. Your employees: the front line in cyber security

    OpenAIRE

    Ashenden, D

    2016-01-01

    First published in The Chemical Engineer and reproduced by Crest - Centre for Research and Evidence on Security Threats, 26/01/2016 (https://crestresearch.ac.uk/comment/employees-front-line-cyber-security/)

  17. Light-front quantization of the sine-Gordon model

    International Nuclear Information System (INIS)

    Burkardt, M.

    1993-01-01

    It is shown how to modify the canonical light-front quantization of the (1+1)-dimensional sine-Gordon model such that the zero-mode problem of light-front quantization is avoided. The canonical sine-Gordon Lagrangian is replaced by an effective Lagrangian which does not lead to divergences as k + =(k 0 +k 1 )/ √2 →0. After canonically quantizing the effective Lagrangian, one obtains the effective light-front Hamiltonian which agrees with the naive light-front (LF) Hamiltonian, up to one additional renormalization. The spectrum of the effective LF Hamiltonian is determined using discrete light-cone quantization and agrees with results from equal-time quantization

  18. Temperature in subsonic and supersonic radiation fronts measured at OMEGA

    Science.gov (United States)

    Johns, Heather; Kline, John; Lanier, Nick; Perry, Ted; Fontes, Chris; Fryer, Chris; Brown, Colin; Morton, John

    2017-10-01

    Propagation of heat fronts relevant to astrophysical plasmas is challenging in the supersonic regime. Plasma Te changes affect opacity and equation of state without hydrodynamic change. In the subsonic phase density perturbations form at material interfaces as the plasma responds to radiation pressure of the front. Recent experiments at OMEGA studied this transition in aerogel foams driven by a hohlraum. In COAX, two orthogonal backlighters drive x-ray radiography and K-shell absorption spectroscopy to diagnose the subsonic shape of the front and supersonic Te profiles. Past experiments used absorption spectroscopy in chlorinated foams to measure the heat front; however, Cl dopant is not suitable for higher material temperatures at NIF. COAX has developed use of Sc and Ti dopants to diagnose Te between 60-100eV and 100-180eV. Analysis with PrismSPECT using OPLIB tabular opacity data will evaluate the platform's ability to advance radiation transport in this regime.

  19. Idea management in support of pharmaceutical front end innovation

    DEFF Research Database (Denmark)

    Aagaard, Annabeth

    2012-01-01

    The pharmaceutical industry faces continuing pressures from rising R&D costs and depreciating value of patents, as patent lives is eroded by testing procedures and pressures from public authorities to cut health care costs. These challenges have increased the focus on shortening development times......, which again put pressure on the efficiency of front end innovation (FEI). In the attempt to overcome these various challenges pharmaceutical companies are looking for new models to support FEI. This paper explores in what way idea management can be applied as a tool in facilitation of front end...... innovation in practice. First I show through a literature study, how idea management and front end innovation are related and may support each other. Hereafter I apply an exploratory case study of front end innovation in eight medium to large pharmaceutical companies in examination of how idea management...

  20. Fast front-end electronics for COMPASS MWPCs

    CERN Document Server

    Colantoni, M L; Ferrero, A; Frolov, V; Grasso, A; Heinz, S; Maggiora, A; Maggiora, M G; Panzieri, D; Popov, A; Tchalyshev, V

    2000-01-01

    In the COMPASS experiment, under construction at CERN, about 23000 channels of MWPCs will be used. The very high rate of the muon and hadron beams, and the consequently high trigger rate, require front- end electronics with innovative conceptual design. A new MWPC front- end electronics that fulfills the main COMPASS requirement to have a fast DAQ with a minimum dead-time has been designed. The general concept of the front-end cards is described; the comparative tests of two front-end chips, and different fast gas mixtures, are also shown. The commissioning of the experiment will start in the summer 2000, and production running, using the muon beam, is foreseen for the year 2001. (8 refs).

  1. Variational data assimilation of satellite observations to estimate volcanic ash emissions

    NARCIS (Netherlands)

    Lu, S.

    2017-01-01

    Volcanic eruptions release a large amount of volcanic ash, which can pose hazard to human and animal health, land transportation, and aviation safety. Volcanic Ash Transport and Dispersion (VATD) models are critical tools to provide advisory information and timely volcanic ash forecasts. Due to the

  2. Volcanic geomorphology using TanDEM-X

    Science.gov (United States)

    Poland, Michael; Kubanek, Julia

    2016-04-01

    Topography is perhaps the most fundamental dataset for any volcano, yet is surprisingly difficult to collect, especially during the course of an eruption. For example, photogrammetry and lidar are time-intensive and often expensive, and they cannot be employed when the surface is obscured by clouds. Ground-based surveys can operate in poor weather but have poor spatial resolution and may expose personnel to hazardous conditions. Repeat passes of synthetic aperture radar (SAR) data provide excellent spatial resolution, but topography in areas of surface change (from vegetation swaying in the wind to physical changes in the landscape) between radar passes cannot be imaged. The German Space Agency's TanDEM-X satellite system, however, solves this issue by simultaneously acquiring SAR data of the surface using a pair of orbiting satellites, thereby removing temporal change as a complicating factor in SAR-based topographic mapping. TanDEM-X measurements have demonstrated exceptional value in mapping the topography of volcanic environments in as-yet limited applications. The data provide excellent resolution (down to ~3-m pixel size) and are useful for updating topographic data at volcanoes where surface change has occurred since the most recent topographic dataset was collected. Such data can be used for applications ranging from correcting radar interferograms for topography, to modeling flow pathways in support of hazards mitigation. The most valuable contributions, however, relate to calculating volume changes related to eruptive activity. For example, limited datasets have provided critical measurements of lava dome growth and collapse at volcanoes including Merapi (Indonesia), Colima (Mexico), and Soufriere Hills (Montserrat), and of basaltic lava flow emplacement at Tolbachik (Kamchatka), Etna (Italy), and Kīlauea (Hawai`i). With topographic data spanning an eruption, it is possible to calculate eruption rates - information that might not otherwise be available

  3. The Variable Climate Impact of Volcanic Eruptions

    Science.gov (United States)

    Graf, H.

    2011-12-01

    The main effect of big volcanic eruptions in the climate system is due to their efficient transport of condensable gases and their precursors into the stratosphere. There the formation of aerosols leads to effects on atmospheric radiation transfer inducing a reduction of incoming solar radiation by reflection (i.e. cooling of the Earth surface) and absorption of near infrared radiation (i.e. heating) in the aerosol laden layers. In the talk processes determining the climate effect of an eruption will be illustrated by examples, mainly from numerical modelling. The amount of gases released from a magma during an eruption and the efficiency of their transport into very high altitudes depends on the geological setting (magma type) and eruption style. While mid-sized eruption plumes of Plinian style quickly can develop buoyancy by entrainment of ambient air, very large eruptions with high magma flux rates often tend to collapsing plumes and co-ignimbrite style. These cover much bigger areas and are less efficient in entraining ambient air. Vertical transport in these plumes is chaotic and less efficient, leading to lower neutral buoyancy height and less gas and particles reaching high stratospheric altitudes. Explosive energy and amount of released condensable gases are not the only determinants for the climatic effect of an eruption. The effect on shortwave radiation is not linear with the amount of aerosols formed since according to the Lambert-Beer Law atmospheric optical depth reaches a saturation limit with increased absorber concentration. In addition, if more condensable gas is available for aerosol growth, particles become larger and this affects their optical properties to less reflection and more absorption. Larger particles settle out faster, thus reducing the life time of the aerosol disturbance. Especially for big tropical eruptions the strong heating of the stratosphere in low latitudes leads to changes in atmospheric wave propagation by strengthened

  4. Gas measurements from the Costa Rica-Nicaragua volcanic segment suggest possible along-arc variations in volcanic gas chemistry

    Science.gov (United States)

    Aiuppa, A.; Robidoux, P.; Tamburello, G.; Conde, V.; Galle, B.; Avard, G.; Bagnato, E.; De Moor, J. M.; Martínez, M.; Muñóz, A.

    2014-12-01

    Obtaining accurate estimates of the CO2 output from arc volcanism requires a precise understanding of the potential along-arc variations in volcanic gas chemistry, and ultimately of the magmatic gas signature of each individual arc segment. In an attempt to more fully constrain the magmatic gas signature of the Central America Volcanic Arc (CAVA), we present here the results of a volcanic gas survey performed during March and April 2013 at five degassing volcanoes within the Costa Rica-Nicaragua volcanic segment (CNVS). Observations of the volcanic gas plume made with a multicomponent gas analyzer system (Multi-GAS) have allowed characterization of the CO2/SO2-ratio signature of the plumes at Poás (0.30±0.06, mean ± SD), Rincón de la Vieja (27.0±15.3), and Turrialba (2.2±0.8) in Costa Rica, and at Telica (3.0±0.9) and San Cristóbal (4.2±1.3) in Nicaragua (all ratios on molar basis). By scaling these plume compositions to simultaneously measured SO2 fluxes, we estimate that the CO2 outputs at CNVS volcanoes range from low (25.5±11.0 tons/day at Poás) to moderate (918 to 1270 tons/day at Turrialba). These results add a new information to the still fragmentary volcanic CO2 output data set, and allow estimating the total CO2 output from the CNVS at 2835±1364 tons/day. Our novel results, with previously available information about gas emissions in Central America, are suggestive of distinct volcanic gas CO2/ST (= SO2 + H2S)-ratio signature for magmatic volatiles in Nicaragua (∼3) relative to Costa Rica (∼0.5-1.0). We also provide additional evidence for the earlier theory relating the CO2-richer signature of Nicaragua volcanism to increased contributions from slab-derived fluids, relative to more-MORB-like volcanism in Costa Rica. The sizeable along-arc variations in magmatic gas chemistry that the present study has suggested indicate that additional gas observations are urgently needed to more-precisely confine the volcanic CO2 from the CAVA, and from

  5. Timing and compositional evolution of Late Pleistocene to Holocene volcanism within the Harrat Rahat volcanic field, Kingdom of Saudi Arabia

    Science.gov (United States)

    Stelten, M. E.; Downs, D. T.; Dietterich, H. R.

    2017-12-01

    Harrat Rahat is one of the largest ( 20,000 km2) of 15 active Cenozoic volcanic fields that stretch 3,000 km along the western Arabian Peninsula from Yemen to Syria. The Harrat Rahat volcanic field is 310 km long (N-S) by 75 km wide (E-W), and is dominated by alkalic basalts with minor hawaiite, mugearite, benmoreite, and trachyte eruptives. The timing of volcanism within greater Harrat Rahat is poorly constrained, but field relations and geochronology indicate that northern Harrat Rahat hosted the most recent eruptions. To better constrain the timing and compositional evolution of Harrat Rahat during this recent phase, we present 743 geochemical analyses, 144 40Ar/39Ar ages, and 9 36Cl exposure ages for volcanic strata from northernmost Harrat Rahat. These data demonstrate that volcanism has been ongoing from at least 1.2 Ma to the present, with the most recent eruption known from historical accounts at 1256 CE. Basalt has erupted persistently from 1.2 Ma to the present, but more evolved volcanism has been episodic. Benmoreite erupted at 1.1 Ma and between 550 to 400 ka. Trachytic volcanism has only occurred over the past 150 ka, with the most recent eruption at 5 ka. Aside from the well-documented basaltic eruption at 1256 CE, prior workers interpreted 6 additional basaltic eruptions during the Holocene. However, our 36Cl exposure ages demonstrate that these erupted between 60 to 13 ka. Interestingly, in the northern part of our field area, where the spatial density of volcanic vents is low, young volcanism (<150 ka) is dominated by basaltic eruptions. Conversely, young volcanism in the southern part of our field area, where volcanic vent density is high, is dominated by trachyte. This observation is consistent with a process wherein the time-integrated effects of basaltic influx into the crust in the south produced a mafic intrusive complex, through which younger basaltic magmas cannot ascend. Instead, these magmas stall and produce trachyte, likely through

  6. Front-end electronics development for the SSC

    International Nuclear Information System (INIS)

    Levi, M.

    1990-12-01

    This is a status report on electronics development undertaken by the Front-End Electronics Collaboration. The overall goal of the collaboration remains the development by 1992 of complete, architecturally compatible, front end electronic systems for calorimeter, wire drift chamber, and silicon strip readout. We report here a few highlights to give a brief overview of the work underway. Performance requirements and capabilities, selected architectures, circuit designs and test results are presented. 13 refs., 21 figs., 1 tab

  7. Flow structure in front of the broad-crested weir

    Directory of Open Access Journals (Sweden)

    Zachoval Zbyněk

    2015-01-01

    Full Text Available The paper deals with research focused on description of flow structure in front of broad-crested weir. Based on experimental measurement, the flow structure in front of the weir (the recirculation zone of flow and tornado vortices and flow structure on the weir crest has been described. The determined flow character has been simulated using numerical model and based on comparing results the suitable model of turbulence has been recommended.

  8. Multiple Scale Reaction-Diffusion-Advection Problems with Moving Fronts

    Science.gov (United States)

    Nefedov, Nikolay

    2016-06-01

    In this work we discuss the further development of the general scheme of the asymptotic method of differential inequalities to investigate stability and motion of sharp internal layers (fronts) for nonlinear singularly perturbed parabolic equations, which are called in applications reaction-diffusion-advection equations. Our approach is illustrated for some new important cases of initial boundary value problems. We present results on stability and on the motion of the fronts.

  9. Landau-Darrieus instability in an ablation front

    International Nuclear Information System (INIS)

    Piriz, A.R.; Portugues, R.F.

    2003-01-01

    An analytical model that shows the conditions for the existence of the Landau-Darrieus instability of an ablation front is presented. The model seems to agree with recently claimed simulation results [L. Masse et al., Proceedings of the 1st International Conference on Inertial Fusion Sciences and Applications (Elsevier, Paris, 2000), p. 220]. The model shows that the ablation front can be unstable in absence of gravity when the thermal flux is inhibited within the supercritical region of the corona

  10. An Alternative Front End Analysis Strategy for Complex Systems

    Science.gov (United States)

    2014-12-01

    missile ( ABM ) system . Patriot is employed in the field through a battalion echelon organizational structure. The line battery is the basic building...Research Report 1981 An Alternative Front End Analysis Strategy for Complex Systems M. Glenn Cobb U.S. Army Research Institute...NUMBER W5J9CQ11D0003 An Alternative Front End Analysis Strategy for Complex Systems 5b. PROGRAM ELEMENT NUMBER 633007 6

  11. Radiation hardness on very front-end for SPD

    International Nuclear Information System (INIS)

    Cano, Xavier; Graciani, Ricardo; Gascon, David; Garrido, Lluis; Bota, Sebastia; Herms, Atila; Comerma, Albert; Riera, Jordi

    2005-01-01

    The calorimeter front-end electronics of the LHCb experiment will be located in a region, which is not protected from radiation. Therefore, all the electronics must be qualified to stand some defined radiation levels. The procedure, measurements and results of an irradiation test for every component of the very front-end SPD detector, which is part of the LHCb calorimeter are presented here. All the tested components, except a custom made ASIC, are commercially available

  12. Are Hydrostatic Models Still Capable of Simulating Oceanic Fronts

    Science.gov (United States)

    2016-11-10

    Hydrostatic Models Still Capable of Simulating Oceanic Fronts Yalin Fan Zhitao Yu Ocean Dynamics and Prediction Branch Oceanography Division FengYan Shi...OF PAGES 17. LIMITATION OF ABSTRACT Are Hydrostatic Models Still Capable of Simulating Oceanic Fronts? Yalin Fan, Zhitao Yu, and, Fengyan Shi1 Naval...mixed layer and thermocline simulations as well as large scale circulations. Numerical experiments are conducted using hydrostatic (HY) and

  13. Poincare invariant algebra from instant to light-front quantization

    International Nuclear Information System (INIS)

    Ji, Chueng-Ryong; Mitchell, Chad

    2001-01-01

    We present the Poincare algebra interpolating between instant and light-front time quantizations. The angular momentum operators satisfying SU(2) algebra are constructed in an arbitrary interpolation angle and shown to be identical to the ordinary angular momentum and Leutwyler-Stern angular momentum in the instant and light-front quantization limits, respectively. The exchange of the dynamical role between the transverse angular mometum and the boost operators is manifest in our newly constructed algebra

  14. Indico front-end: From spaghetti to lasagna

    CERN Multimedia

    CERN. Geneva

    2017-01-01

    We will present how we transitioned from legacy spaghetti UI code to a more coherent, easier to understand and maintain ecosystem of front-end technologies and facilities with a strong emphasis in reusable components. In particular, we will share with you: 1) how we use Sass to maintain our home-baked CSS, 2) how we survive in 2017 without front-end Javascript frameworks, and 3) how we use template macros and WTForms for generating consistent HTML transparently.

  15. Traveling wave front solutions in lateral-excitatory neuronal networks

    Directory of Open Access Journals (Sweden)

    Sittipong Ruktamatakul

    2008-05-01

    Full Text Available In this paper, we discuss the shape of traveling wave front solutions to a neuronal model with the connection function to be of lateral excitation type. This means that close connecting cells have an inhibitory influence, while cells that aremore distant have an excitatory influence. We give results on the shape of the wave fronts solutions, which exhibit different shapes depend ing on the size of a threshold parameter.

  16. Hyper-X Vehicle Model - Front View

    Science.gov (United States)

    1996-01-01

    A front view of an early desk-top model of NASA's X-43A 'Hyper-X,' or Hypersonic Experimental Vehicle, which has been developed to flight test a dual-mode ramjet/scramjet propulsion system at speeds from Mach 7 up to Mach 10 (7 to 10 times the speed of sound, which varies with temperature and altitude). Hyper-X, the flight vehicle for which is designated as X-43A, is an experimental flight-research program seeking to demonstrate airframe-integrated, 'air-breathing' engine technologies that promise to increase payload capacity for future vehicles, including hypersonic aircraft (faster than Mach 5) and reusable space launchers. This multiyear program is currently underway at NASA Dryden Flight Research Center, Edwards, California. The Hyper-X schedule calls for its first flight later this year (2000). Hyper-X is a joint program, with Dryden sharing responsibility with NASA's Langley Research Center, Hampton, Virginia. Dryden's primary role is to fly three unpiloted X-43A research vehicles to validate engine technologies and hypersonic design tools as well as the hypersonic test facility at Langley. Langley manages the program and leads the technology development effort. The Hyper-X Program seeks to significantly expand the speed boundaries of air-breathing propulsion by being the first aircraft to demonstrate an airframe-integrated, scramjet-powered free flight. Scramjets (supersonic-combustion ramjets) are ramjet engines in which the airflow through the whole engine remains supersonic. Scramjet technology is challenging because only limited testing can be performed in ground facilities. Long duration, full-scale testing requires flight research. Scramjet engines are air-breathing, capturing their oxygen from the atmosphere. Current spacecraft, such as the Space Shuttle, are rocket powered, so they must carry both fuel and oxygen for propulsion. Scramjet technology-based vehicles need to carry only fuel. By eliminating the need to carry oxygen, future hypersonic

  17. Combustion waves and fronts in flows flames, shocks, detonations, ablation fronts and explosion of stars

    CERN Document Server

    Clavin, Paul

    2016-01-01

    Combustion is a fascinating phenomenon coupling complex chemistry to transport mechanisms and nonlinear fluid dynamics. This book provides an up-to-date and comprehensive presentation of the nonlinear dynamics of combustion waves and other non-equilibrium energetic systems. The major advances in this field have resulted from analytical studies of simplified models performed in close relation with carefully controlled laboratory experiments. The key to understanding the complex phenomena is a systematic reduction of the complexity of the basic equations. Focusing on this fundamental approach, the book is split into three parts. Part I provides physical insights for physics-oriented readers, Part II presents detailed technical analysis using perturbation methods for theoreticians, and Part III recalls the necessary background knowledge in physics, chemistry and fluid dynamics. This structure makes the content accessible to newcomers to the physics of unstable fronts in flows, whilst also offering advanced mater...

  18. Digital front-end module (DFEM) series; Digital front end module (DFEM) series

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    The digital front-end module (DFEM) is a module in which the processes ranging from the reception of digitally modulated radiofrequencies to the output of digital IF (Intermediate Frequency) signals or data streams are integrated. Beginning with a module for the MCNS (Multimedia Cable Network System) cable modem which was the first module in this business field approved by the Cable Labs, U.S., Toshiba has developed a series of DFEMs for various digital media for satellites, ground waves, and CATV (Cable Television) systems. The series is characterized by (1) the serialization of DFEMs compatible with various digital modulation techniques such as 8 PSK (Phase Shift Keying), OFDM (Orthogonal Frequency Division Multiplexing), and 256 QAM (Quadrature Amplitude Modulation), (2) easy connection with digital circuits thanks to the high shielding effect, and (3) the achievement of smaller size, higher performance, and lower power consumption. (translated by NEDO)

  19. Zero modes in discretized light-front quantization

    International Nuclear Information System (INIS)

    Martinovic, E.

    1997-01-01

    The current understanding of the role of bosonic zero modes in field-theoretical models quantized at the equal light-front time is reviewed. After a brief discussion of the main features of the light-front field theories - in particular the simplicity of the physical vacuum - the light-front canonical formalism for the quantum electrodynamics and the Yukawa model is sketched. The zero mode of Maskawa and Yamawaki is reviewed. Reasons for the appearance of the constrained and/or dynamical zero modes are explained along with the subtleties of the gauge fixing in presence of boundary conditions. Perturbative treatment of the corresponding constraint equations in the Yukawa model and quantum electrodynamics (3+1) is outlined. The next topic is the manifestation of the symmetry breaking in the light-front field theory. A pattern of multiple solutions to the zero-mode constraint equations replacing physical picture of multiple vacua of the conventionally quantized field theories is illustrated on an example of 2-dimensional theory. The importance of a (regularized) constrained zero mode of the pion field for the consistency of the Nambu-Goldstone phase of the discretized light-front linear a/model is demonstrated. Finally, a non-trivial physical vacuum based on the dynamical zero mode is constructed for the two-dimensional light-front quantum electrodynamics. (authors)

  20. Light-Front Holography and AdS/QCD Correspondence

    Energy Technology Data Exchange (ETDEWEB)

    Brodsky, Stanley J.; de Teramond, Guy F.

    2008-04-23

    Light-Front Holography is a remarkable consequence of the correspondence between string theory in AdS space and conformal field theories in physical-space time. It allows string modes {Phi}(z) in the AdS fifth dimension to be precisely mapped to the light-front wavefunctions of hadrons in terms of a specific light-front impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron. This mapping was originally obtained by matching the exact expression for electromagnetic current matrix elements in AdS space with the corresponding exact expression for the current matrix element using light-front theory in physical space-time. More recently we have shown that one obtains the identical holographic mapping using matrix elements of the energy-momentum tensor, thus providing an important consistency test and verification of holographic mapping from AdS to physical observables defined on the light-front. The resulting light-front Schrodinger equations predicted from AdS/QCD give a good representation of the observed meson and baryon spectra and give excellent phenomenological predictions for amplitudes such as electromagnetic form factors and decay constants.

  1. Feedback from operational experience in front-end transportation

    International Nuclear Information System (INIS)

    Mondonel, J.L.; Parison, C.

    1998-01-01

    Transport forms an integral part of the nuclear fuel cycle, representing the strategic link between each stage of the cycle. In a way there is a transport cycle that parallels the nuclear fuel cycle. This concerns particularly the front-end of the cycle whose steps - mining conversion, enrichment and fuel fabrication - require numerous transports. Back-end shipments involve a handful of countries, but front-end transports involve all five continents, and many exotic countries. All over Europe such transports are routinely performed with an excellent safety track record. Transnucleaire dominates the French nuclear transportation market and carries out both front and back-end transports. For instance in 1996 more than 28,400 front-end packages were transported as well as more than 3,600 back-end packages. However front-end transport is now a business undergoing much change. A nuclear transportation company must now cope with an evolving picture including new technical requirements, new transportation schemes and new business conditions. This paper describes the latest evolutions in terms of front-end transportation and the way this activity is carried out by Transnucleaire, and goes on to discuss future prospects. (authors)

  2. Optimal Design of HGV Front Structure for Pedestrian Safety

    Science.gov (United States)

    Ramli, Faiz Redza; Yamazaki, Koetsu

    This paper addresses a pedestrian safety design of front structure of Heavy Goods Vehicle (HGV) by two concepts; firstly by equipping a lower bumper stiffener structure under the front bumper and secondly by putting an airbag in front of the HGV front panel. In this study, HGV-pedestrian collision accident was simulated by the crash analysis solver MADYMO environment, where the HGV model with the speed of 20 km/h was collided with an adult male and with an adult female pedestrian, respectively. The bumper and lower bumper stiffener were varied their positions, while the airbag was adjusted the vent hole size and the position of airbag in front of front panel vertically. The pedestrian injuries that can be sustained during the simulation impact were limited at the critical body parts of head, chest, upper leg; an injury criteria of Head Injury Criterion (HIC), Thorax Cumulative 3ms Acceleration (C3ms) and peak loads of femur, respectively. Because of various parameters and constraints of initial conditions and injury thresholds, a multi-objective optimization design problem considered these main injury criterion is solved in order to achieve the best solution for this study. The results of optimized design parameters for each cases and conditions were obtained and the possibilities of the proposed concept were discussed.

  3. Palynology and clay mineralogy of the Deccan volcanic associated ...

    Indian Academy of Sciences (India)

    ontological studies of Deccan volcanic associated intertrappean sediments at ... and also for bridging the gap in the knowledge of palynofloral ..... G P, Systematic Association Special Volume, (Oxford: Clarendon .... Traps: A review; Geol. Surv.

  4. Observations of volcanic plumes using small balloon soundings

    Science.gov (United States)

    Voemel, H.

    2015-12-01

    Eruptions of volcanoes are very difficult to predict and for practical purposes may occur at any time. Any observing system intending to observe volcanic eruptions has to be ready at any time. Due to transport time scales, emissions of large volcanic eruptions, in particular injections into the stratosphere, may be detected at locations far from the volcano within days to weeks after the eruption. These emissions may be observed using small balloon soundings at dedicated sites. Here we present observations of particles of the Icelandic Grimsvotn eruption at the Meteorological Observatory Lindenberg, Germany in the months following the eruption and observations of opportunity of other volcanic particle events. We also present observations of the emissions of SO2 from the Turrialba volcano at San Jose, Costa Rica. We argue that dedicated sites for routine observations of the clean and perturbed atmosphere using small sounding balloons are an important element in the detection and quantification of emissions from future volcanic eruptions.

  5. Petrogeochemistry of Mesozoic basaltic volcanics in Daqingshan area

    International Nuclear Information System (INIS)

    Li Xiaoguang; Li Ziying; Wei Sanyuan; Qi Da'neng

    2009-01-01

    Through the discussion on petrogeochemistry of Later Mesozoic basaltic volcanics in Daqingshan Basin in Manzhouli area, combined with field observation and the predecessors' study, its magma evolution,genesis and diagenetic structural environment are discussed, and some suggestion are provided for the further work. Basaltic magma in this area is believed to be derived from mantle with incompatible elements which were later participated by some crustal materials. It is a partially melting product of mantle by early metasomatized fluid under lithosphere extension. Through petrogeochemical analysis of the volcanics and the contrast to the adjacent uranium-producing volcanics, it is concluded that this region has structural environment to form magma evolution series which are more favorable for volcanic hydrothermal-type uranium and polymetallic mineralization. (authors)

  6. MEVTV Workshop on Early Tectonic and Volcanic Evolution of Mars

    International Nuclear Information System (INIS)

    Frey, H.

    1988-01-01

    Although not ignored, the problems of the early tectonic and volcanic evolution of Mars have generally received less attention than those later in the evolution of the planet. Specifically, much attention was devoted to the evolution of the Tharsis region of Mars and to the planet itself at the time following the establishment of this major tectonic and volcanic province. By contrast, little attention was directed at fundamental questions, such as the conditions that led to the development of Tharsis and the cause of the basic fundamental dichotomy of the Martian crust. It was to address these and related questions of the earliest evolution of Mars that a workshop was organized under the auspices of the Mars: Evolution of Volcanism, Tectonism, and Volatiles (MEVTV) Program. Four sessions were held: crustal dichotomy; crustal differentiation/volcanism; Tharsis, Elysium, and Valles Marineris; and ridges and fault tectonics

  7. Solid State Multiwavelength LIDAR for Volcanic Ash Monitoring, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Physical Sciences Inc. proposes to develop a compact, multiwavelength LIDAR with polarization analysis capability that will be able to identify volcanic ash clouds...

  8. Global Significant Volcanic Eruptions Database, 4360 BC to present

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Significant Volcanic Eruptions Database is a global listing of over 600 eruptions from 4360 BC to the present. A significant eruption is classified as one that...

  9. eVADE: Volcanic Ash Detection Raman LIDAR, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Volcanic ash is a significant hazard to aircraft engine and electronics and has caused damage to unwary aircraft and disrupted air travel for thousands of travelers,...

  10. Volcanic Ash Detection Using Raman LIDAR: "VADER", Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Volcanic ash is a significant hazard to aircraft engine and electronics and has caused damage to unwary aircraft and disrupted air travel for thousands of travelers,...

  11. A great volcanic eruption around AD 1300 recorded in lacustrine ...

    Indian Academy of Sciences (India)

    2National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, .... Island; and (d) sampling sites of sediment cores DY6 in Cattle Pond. ..... African dust and volcanic ash inputs to terra rossa soils on.

  12. The Role of Volcanic Activity in Climate and Global Change

    KAUST Repository

    Stenchikov, Georgiy L.

    2015-01-01

    . 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

  13. Compositional Differences between Felsic Volcanic Rocks from the ...

    African Journals Online (AJOL)

    Bheema

    characteristics of the volcanic units, we describe the compositional differences ...... Geology and mineral resources of Somalia and surrounding regions. ... zone (Ethiopia) Journal of Volcanological and Geothermal Research, 80: 267-280.

  14. Impacts of a Pinatubo-size volcanic eruption on ENSO

    KAUST Repository

    Predybaylo, Evgeniya; Stenchikov, Georgiy L.; Wittenberg, Andrew T.; Zeng, Fanrong

    2017-01-01

    Observations and model simulations of the climate responses to strong explosive low-latitude volcanic eruptions suggest a significant increase in the likelihood of El Niño during the eruption and posteruption years, though model results have been

  15. Large-scale volcanism associated with coronae on Venus

    Science.gov (United States)

    Roberts, K. Magee; Head, James W.

    1993-01-01

    The formation and evolution of coronae on Venus are thought to be the result of mantle upwellings against the crust and lithosphere and subsequent gravitational relaxation. A variety of other features on Venus have been linked to processes associated with mantle upwelling, including shield volcanoes on large regional rises such as Beta, Atla and Western Eistla Regiones and extensive flow fields such as Mylitta and Kaiwan Fluctus near the Lada Terra/Lavinia Planitia boundary. Of these features, coronae appear to possess the smallest amounts of associated volcanism, although volcanism associated with coronae has only been qualitatively examined. An initial survey of coronae based on recent Magellan data indicated that only 9 percent of all coronae are associated with substantial amounts of volcanism, including interior calderas or edifices greater than 50 km in diameter and extensive, exterior radial flow fields. Sixty-eight percent of all coronae were found to have lesser amounts of volcanism, including interior flooding and associated volcanic domes and small shields; the remaining coronae were considered deficient in associated volcanism. It is possible that coronae are related to mantle plumes or diapirs that are lower in volume or in partial melt than those associated with the large shields or flow fields. Regional tectonics or variations in local crustal and thermal structure may also be significant in determining the amount of volcanism produced from an upwelling. It is also possible that flow fields associated with some coronae are sheet-like in nature and may not be readily identified. If coronae are associated with volcanic flow fields, then they may be a significant contributor to plains formation on Venus, as they number over 300 and are widely distributed across the planet. As a continuation of our analysis of large-scale volcanism on Venus, we have reexamined the known population of coronae and assessed quantitatively the scale of volcanism associated

  16. Volcanic sulfur degassing and the role of sulfides in controlling volcanic metal emissions

    Science.gov (United States)

    Edmonds, M.; Liu, E.

    2017-12-01

    Volcanoes emit prodigious quantities of sulfur and metals, their behaviour inextricably linked through pre-eruptive sulfide systematics and through degassing and speciation in the volcanic plume. Fundamental differences exist in the metal output of ocean island versus arc volcanoes, with volcanoes in Hawaii and Iceland outgassing large fluxes of gaseous and particulate chalcophiles; and arc volcanoes' plumes, in contrast, enriched in Zn, Cu, Tl and Pb. Metals and metalloids partition into a magmatic vapor phase from silicate melt at crustal pressures. Their abundance in magmatic vapor is influenced strongly by sulfide saturation and by the composition of the magmatic vapor phase, particularly with respect to chloride. These factors are highly dependent on tectonic setting. Metal outgassing is controlled by magma water content and redox: deep saturation in vapor and minimal sulfide in arc basalts yields metal-rich vapor; shallow degassing and resorption of sulfides feeds the metal content of volcanic gas in ocean islands. We present a detailed study of the sulfide systematics of the products of the 2014-2015 Holuhraun basaltic fissure eruption (Bárðarbunga volcanic system, Iceland) to illustrate the interplay between late water and sulfur outgassing; sulfide saturation and breakdown; and metal partitioning into a vapor phase. Sulfide globules, representing quenched droplets of an immiscible sulfide liquid, are preserved within erupted tephra. Sulfide globules in rapidly quenched tephra are preserved within both matrix glass and as inclusions in crystals. The stereologically-corrected 3D size distribution of sulfide globules ranges from importance in supplying sulfur and metals to the atmosphere during eruption.

  17. Optimal likelihood-based matching of volcanic sources and deposits in the Auckland Volcanic Field

    Science.gov (United States)

    Kawabata, Emily; Bebbington, Mark S.; Cronin, Shane J.; Wang, Ting

    2016-09-01

    In monogenetic volcanic fields, where each eruption forms a new volcano, focusing and migration of activity over time is a very real possibility. In order for hazard estimates to reflect future, rather than past, behavior, it is vital to assemble as much reliable age data as possible on past eruptions. Multiple swamp/lake records have been extracted from the Auckland Volcanic Field, underlying the 1.4 million-population city of Auckland. We examine here the problem of matching these dated deposits to the volcanoes that produced them. The simplest issue is separation in time, which is handled by simulating prior volcano age sequences from direct dates where known, thinned via ordering constraints between the volcanoes. The subproblem of varying deposition thicknesses (which may be zero) at five locations of known distance and azimuth is quantified using a statistical attenuation model for the volcanic ash thickness. These elements are combined with other constraints, from widespread fingerprinted ash layers that separate eruptions and time-censoring of the records, into a likelihood that was optimized via linear programming. A second linear program was used to optimize over the Monte-Carlo simulated set of prior age profiles to determine the best overall match and consequent volcano age assignments. Considering all 20 matches, and the multiple factors of age, direction, and size/distance simultaneously, results in some non-intuitive assignments which would not be produced by single factor analyses. Compared with earlier work, the results provide better age control on a number of smaller centers such as Little Rangitoto, Otuataua, Taylors Hill, Wiri Mountain, Green Hill, Otara Hill, Hampton Park and Mt Cambria. Spatio-temporal hazard estimates are updated on the basis of the new ordering, which suggest that the scale of the 'flare-up' around 30 ka, while still highly significant, was less than previously thought.

  18. Mainshock-Aftershocks Clustering Detection in Volcanic Regions

    Science.gov (United States)

    Garza Giron, R.; Brodsky, E. E.; Prejean, S. G.

    2017-12-01

    Crustal earthquakes tend to break their general Poissonean process behavior by gathering into two main kinds of seismic bursts: swarms and mainshock-aftershocks sequences. The former is commonly related to volcanic or geothermal processes whereas the latter is a characteristic feature of tectonically driven seismicity. We explore the mainshock-aftershock clustering behavior of different active volcanic regions in Japan and its comparison to non-volcanic regions. We find that aftershock production in volcanoes shows mainshock-aftershocks clustering similar to what is observed in non-volcanic areas. The ratio of volanic areas that cluster in mainshock-aftershocks sequences vs the areas that do not is comparable to the ratio of non-volcanic regions that show clustering vs the ones that do not. Furthermore, the level of production of aftershocks for most volcanic areas where clustering is present seems to be of the same order of magnitude, or slightly higher, as the median of the non-volcanic regions. An interesting example of highly aftershock-productive volcanoes emerges from the 2000 Miyakejima dike intrusion. A big seismic cluster started to build up rapidly in the south-west flank of Miyakejima to later propagate to the north-west towards the Kozushima and Niijima volcanoes. In Miyakejima the seismicity showed a swarm-like signature with a constant earthquake rate, whereas Kozushima and Niijima both had expressions of highly productive mainshock-aftershocks sequences. These findings are surprising given the alternative mechanisms available in volcanic systems for releasing deviatoric strain. We speculate that aftershock behavior might hold a relationship with the rheological properties of the rocks of each system and with the capacity of a system to accumulate or release the internal pressures caused by magmatic or hydrothermal systems.

  19. Inferring climate sensitivity from volcanic events

    Energy Technology Data Exchange (ETDEWEB)

    Boer, G.J. [Environment Canada, University of Victoria, Canadian Centre for Climate Modelling and Analysis, Victoria, BC (Canada); Stowasser, M.; Hamilton, K. [University of Hawaii, International Pacific Research Centre, Honolulu, HI (United States)

    2007-04-15

    The possibility of estimating the equilibrium climate sensitivity of the earth-system from observations following explosive volcanic eruptions is assessed in the context of a perfect model study. Two modern climate models (the CCCma CGCM3 and the NCAR CCSM2) with different equilibrium climate sensitivities are employed in the investigation. The models are perturbed with the same transient volcano-like forcing and the responses analysed to infer climate sensitivities. For volcano-like forcing the global mean surface temperature responses of the two models are very similar, despite their differing equilibrium climate sensitivities, indicating that climate sensitivity cannot be inferred from the temperature record alone even if the forcing is known. Equilibrium climate sensitivities can be reasonably determined only if both the forcing and the change in heat storage in the system are known very accurately. The geographic patterns of clear-sky atmosphere/surface and cloud feedbacks are similar for both the transient volcano-like and near-equilibrium constant forcing simulations showing that, to a considerable extent, the same feedback processes are invoked, and determine the climate sensitivity, in both cases. (orig.)

  20. CO2 flux from Javanese mud volcanism.

    Science.gov (United States)

    Queißer, M; Burton, M R; Arzilli, F; Chiarugi, A; Marliyani, G I; Anggara, F; Harijoko, A

    2017-06-01

    Studying the quantity and origin of CO 2 emitted by back-arc mud volcanoes is critical to correctly model fluid-dynamical, thermodynamical, and geochemical processes that drive their activity and to constrain their role in the global geochemical carbon cycle. We measured CO 2 fluxes of the Bledug Kuwu mud volcano on the Kendeng Fold and thrust belt in the back arc of Central Java, Indonesia, using scanning remote sensing absorption spectroscopy. The data show that the expelled gas is rich in CO 2 with a volume fraction of at least 16 vol %. A lower limit CO 2 flux of 1.4 kg s -1 (117 t d -1 ) was determined, in line with the CO 2 flux from the Javanese mud volcano LUSI. Extrapolating these results to mud volcanism from the whole of Java suggests an order of magnitude total CO 2 flux of 3 kt d -1 , comparable with the expected back-arc efflux of magmatic CO 2 . After discussing geochemical, geological, and geophysical evidence we conclude that the source of CO 2 observed at Bledug Kuwu is likely a mixture of thermogenic, biogenic, and magmatic CO 2 , with faulting controlling potential pathways for magmatic fluids. This study further demonstrates the merit of man-portable active remote sensing instruments for probing natural gas releases, enabling bottom-up quantification of CO 2 fluxes.

  1. Volcanic Eruption: Students Develop a Contingency Plan

    Science.gov (United States)

    Meisinger, Philipp; Wittlich, Christian

    2013-04-01

    Dangerous, loud, sensational, exciting - natural hazards have what it takes to get students attention around the globe. Arising interest is the first step to develop an intrinsic motivation to learn about the matter and endure the hardships that students might discover along the way of the unit. Natural hazards thereby establish a close-knit connection between physical and anthropological geography through analyzing the hazardous event and its consequences for the people living in the affected area. Following a general principle of didactics we start searching right on our doorsteps to offer students the possibility to gain knowledge on the familiar and later transfer it to the unknown example. Even in Southwest Germany - a region that is rather known for its wine than its volcanic activity - we can find a potentially hazardous region. The "Laacher See" volcano (a caldera lake) in northern Rhineland-Palatinate is according to Prof. H.U. Schminke a "potentially active volcano" . Its activity can be proven by seismic activities, or experienced when visiting the lake's southeastern shore, where carbondioxid and sulphur gases from the underlying magma chamber still bubble up. The Laacher See is part of a range of volcanoes (classified from 'potentially active' to 'no longer active') of the East Eifel Volcanic Field. Precariously the Laacher See is located closely to the densely populated agglomerations of Cologne (NE, distance: 45 km) and the former capital Bonn (NE: 35km), as well as Koblenz (E: 24km) and the Rhine river. Apart from that, the towns of Andernach (E: 8km ± 30 000 inhabitants) and Mayen (SW: 11km ±20 000 inhabitants) and many smaller towns and villages are nearby due to economic reasons. The number of people affected by a possible eruption easily exceeds two million people considering the range as prime measurement. The underlying danger, as projected in a simulation presented by Prof. Schminke, is a lava stream running down the Brohltal valley

  2. Communicating Volcanic Hazards in the North Pacific

    Science.gov (United States)

    Dehn, J.; Webley, P.; Cunningham, K. W.

    2014-12-01

    For over 25 years, effective hazard communication has been key to effective mitigation of volcanic hazards in the North Pacific. These hazards are omnipresent, with a large event happening in Alaska every few years to a decade, though in many cases can happen with little or no warning (e.g. Kasatochi and Okmok in 2008). Here a useful hazard mitigation strategy has been built on (1) a large database of historic activity from many datasets, (2) an operational alert system with graduated levels of concern, (3) scenario planning, and (4) routine checks and communication with emergency managers and the public. These baseline efforts are then enhanced in the time of crisis with coordinated talking points, targeted studies and public outreach. Scientists naturally tend to target other scientists as their audience, whereas in effective monitoring of hazards that may only occur on year to decadal timescales, details can distract from the essentially important information. Creating talking points and practice in public communications can help make hazard response a part of the culture. Promoting situational awareness and familiarity can relieve indecision and concerns at the time of a crisis.

  3. Volcanism and Subduction: The Kamchatka Region

    Science.gov (United States)

    Eichelberger, John; Gordeev, Evgenii; Izbekov, Pavel; Kasahara, Minoru; Lees, Jonathan

    The Kamchatka Peninsula and contiguous North Pacific Rim is among the most active regions in the world. Kamchatka itself contains 29 active volcanoes, 4 now in a state of semi-continuous eruption, and I has experienced 14 magnitude 7 or greater earthquakes since accurate recording began in 1962. At its heart is the uniquely acute subduction cusp where the Kamchatka and Aleutian Arcs and Emperor Seamount Chain meet. Volcanism and Subduction covers coupled magmatism and tectonics in this spectacular region, where the torn North Pacific slab dives into hot mantle. Senior Russian and American authors grapple with the dynamics of the cusp with perspectives from the west and east of it, respectively, while careful tephrostratigraphy yields a remarkably precise record of behavior of storied volcanoes such as Kliuchevskoi and Shiveluch. Towards the south, Japanese researchers elucidate subduction earthquake processes with unprecedented geodetic resolution. Looking eastward, new insights on caldera formation, monitoring, and magma ascent are presented for the Aleutians. This is one of the first books of its kind printed in the English language. Students and scientists beginning research in the region will find in this book a useful context and introduction to the region's scientific leaders. Others who wish to apply lessons learned in the North Pacific to their areas of interest will find the volume a valuable reference.

  4. Volcanism at 1.45 Ma within the Yellowstone Volcanic Field, United States

    Science.gov (United States)

    Rivera, Tiffany A.; Furlong, Ryan; Vincent, Jaime; Gardiner, Stephanie; Jicha, Brian R.; Schmitz, Mark D.; Lippert, Peter C.

    2018-05-01

    Rhyolitic volcanism in the Yellowstone Volcanic Field has spanned over two million years and consisted of both explosive caldera-forming eruptions and smaller effusive flows and domes. Effusive eruptions have been documented preceding and following caldera-forming eruptions, however the temporal and petrogenetic relationships of these magmas to the caldera-forming eruptions are relatively unknown. Here we present new 40Ar/39Ar dates for four small-volume eruptions located on the western rim of the second-cycle caldera, the source of the 1.300 ± 0.001 Ma Mesa Falls Tuff. We supplement our new eruption ages with whole rock major and trace element chemistry, Pb isotopic ratios of feldspar, and paleomagnetic and rock magnetic analyses. Eruption ages for the effusive Green Canyon Flow (1.299 ± 0.002 Ma) and Moonshine Mountain Dome (1.302 ± 0.003 Ma) are in close temporal proximity to the eruption age of the Mesa Falls Tuff. In contrast, our results indicate a period of volcanism at ca 1.45 Ma within the Yellowstone Volcanic Field, including the eruption of the Bishop Mountain Flow (1.458 ± 0.002 Ma) and Tuff of Lyle Spring (1.450 ± 0.003 Ma). These high-silica rhyolites are chemically and isotopically distinct from the Mesa Falls Tuff and related 1.3 Ma effusive eruptions. The 40Ar/39Ar data from the Tuff of Lyle Spring demonstrate significant antecrystic inheritance, prevalent within the upper welded ash-flow tuff matrix, and minimal within individual pumice. Antecrysts are up to 20 kyr older than the eruption, with subpopulations of grains occurring every few thousand years. We interpret these results as an indicator for the timing of magmatic pulses into a growing magmatic system that would ultimately erupt the Tuff of Lyle Spring, and which we more broadly interpret as the tempo of crustal accumulation associated with bimodal magmatism. We propose a system whereby chemically, isotopically, and temporally distinct, isolated small-volume magma batches are

  5. Volcanic passive margins: another way to break up continents.

    Science.gov (United States)

    Geoffroy, L; Burov, E B; Werner, P

    2015-10-07

    Two major types of passive margins are recognized, i.e. volcanic and non-volcanic, without proposing distinctive mechanisms for their formation. Volcanic passive margins are associated with the extrusion and intrusion of large volumes of magma, predominantly mafic, and represent distinctive features of Larges Igneous Provinces, in which regional fissural volcanism predates localized syn-magmatic break-up of the lithosphere. In contrast with non-volcanic margins, continentward-dipping detachment faults accommodate crustal necking at both conjugate volcanic margins. These faults root on a two-layer deformed ductile crust that appears to be partly of igneous nature. This lower crust is exhumed up to the bottom of the syn-extension extrusives at the outer parts of the margin. Our numerical modelling suggests that strengthening of deep continental crust during early magmatic stages provokes a divergent flow of the ductile lithosphere away from a central continental block, which becomes thinner with time due to the flow-induced mechanical erosion acting at its base. Crustal-scale faults dipping continentward are rooted over this flowing material, thus isolating micro-continents within the future oceanic domain. Pure-shear type deformation affects the bulk lithosphere at VPMs until continental breakup, and the geometry of the margin is closely related to the dynamics of an active and melting mantle.

  6. Volcanic Ash Data Assimilation System for Atmospheric Transport Model

    Science.gov (United States)

    Ishii, K.; Shimbori, T.; Sato, E.; Tokumoto, T.; Hayashi, Y.; Hashimoto, A.

    2017-12-01

    The Japan Meteorological Agency (JMA) has two operations for volcanic ash forecasts, which are Volcanic Ash Fall Forecast (VAFF) and Volcanic Ash Advisory (VAA). In these operations, the forecasts are calculated by atmospheric transport models including the advection process, the turbulent diffusion process, the gravitational fall process and the deposition process (wet/dry). The initial distribution of volcanic ash in the models is the most important but uncertain factor. In operations, the model of Suzuki (1983) with many empirical assumptions is adopted to the initial distribution. This adversely affects the reconstruction of actual eruption plumes.We are developing a volcanic ash data assimilation system using weather radars and meteorological satellite observation, in order to improve the initial distribution of the atmospheric transport models. Our data assimilation system is based on the three-dimensional variational data assimilation method (3D-Var). Analysis variables are ash concentration and size distribution parameters which are mutually independent. The radar observation is expected to provide three-dimensional parameters such as ash concentration and parameters of ash particle size distribution. On the other hand, the satellite observation is anticipated to provide two-dimensional parameters of ash clouds such as mass loading, top height and particle effective radius. In this study, we estimate the thickness of ash clouds using vertical wind shear of JMA numerical weather prediction, and apply for the volcanic ash data assimilation system.

  7. Topographic stress and catastrophic collapse of volcanic islands

    Science.gov (United States)

    Moon, S.; Perron, J. T.; Martel, S. J.

    2017-12-01

    Flank collapse of volcanic islands can devastate coastal environments and potentially induce tsunamis. Previous studies have suggested that factors such as volcanic eruption events, gravitational spreading, the reduction of material strength due to hydrothermal alteration, steep coastal cliffs, or sea level change may contribute to slope instability and induce catastrophic collapse of volcanic flanks. In this study, we examine the potential influence of three-dimensional topographic stress perturbations on flank collapses of volcanic islands. Using a three-dimensional boundary element model, we calculate subsurface stress fields for the Canary and Hawaiian islands to compare the effects of stratovolcano and shield volcano shapes on topographic stresses. Our model accounts for gravitational stresses from the actual shapes of volcanic islands, ambient stress in the underlying plate, and the influence of pore water pressure. We quantify the potential for slope failure of volcanic flanks using a combined model of three-dimensional topographic stress and slope stability. The results of our analysis show that subsurface stress fields vary substantially depending on the shapes of volcanoes, and can influence the size and spatial distribution of flank failures.

  8. Self-potential anomalies in some Italian volcanic areas

    Directory of Open Access Journals (Sweden)

    C. Silenziario

    1996-06-01

    Full Text Available The study of Self-Potential (SP space and time variations in volcanic areas may provide useful information on both the geometrical structure of the volcanic apparatuses and the dynamical behaviour of the feeding and uprising systems. In this paper, the results obtained on the islands of Vulcano (Eolian arc and Ponza (Pontine archipelago and on the Mt. Somma-Vesuvius complex are shown. On the island of Vulcano and on the Mt. Somma-Vesuvius apparatus areal SP surveys were performed with the aim of evidencing anomalies closely associated to the zones of major volcanic activity. On the island of Vulcano a profile across the fumaroles along the crater rim of the Fossa Cone was also carried out in order to have a direct relationship between fumarolic fracture migration and flow rate and SP anomaly space and time variations. The areal survey on the island of Ponza, which is considered an inactive area, is assumed as a reference test with which to compare the amplitude and pattern of the anomalies in the active areas. A tentative interpretation of the SP anomalies in volcanic areas is suggested in terms of electrokinetic phenomena, related to the movement of fluids of both volcanic and non-volcanic origin.

  9. 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.

  10. Volcanic hazards of the Idaho National Engineering Laboratory and adjacent areas

    International Nuclear Information System (INIS)

    Hackett, W.R.; Smith, R.P.

    1994-12-01

    Potential volcanic hazards are assessed, and hazard zone maps are developed for the Idaho National Engineering Laboratory (INEL) and adjacent areas. The basis of the hazards assessment and mapping is the past volcanic history of the INEL region, and the apparent similarity of INEL volcanism with equivalent, well-studied phenomena in other regions of active volcanism, particularly Hawaii and Iceland. The most significant hazards to INEL facilities are associated with basaltic volcanism, chiefly lava flows, which move slowly and mainly threaten property by inundation or burning. Related hazards are volcanic gases and tephra, and ground disturbance associated with the ascent of magma under the volcanic zones. Several volcanic zones are identified in the INEL area. These zones contain most of the volcanic vents and fissures of the region and are inferred to be the most probable sites of future INEL volcanism. Volcanic-recurrence estimates are given for each of the volcanic zones based on geochronology of the lavas, together with the results of field and petrographic investigations concerning the cogenetic relationships of INEL volcanic deposits and associated magma intrusion. Annual probabilities of basaltic volcanism within the INEL volcanic zones range from 6.2 x 10 -5 per year (average 16,000-year interval between eruptions) for the axial volcanic zone near the southern INEL boundary and the Arco volcanic-rift zone near the western INEL boundary, to 1 x 10 -5 per year (average 100,000-year interval between eruptions) for the Howe-East Butte volcanic rift zone, a geologically old and poorly defined feature of the central portion of INEL. Three volcanic hazard zone maps are developed for the INEL area: lava flow hazard zones, a tephra (volcanic ash) and gas hazard zone, and a ground-deformation hazard zone. The maps are useful in land-use planning, site selection, and safety analysis

  11. Structural control of monogenetic volcanism in the Garrotxa volcanic field (Northeastern Spain) from gravity and self-potential measurements

    Science.gov (United States)

    Barde-Cabusson, S.; Gottsmann, J.; Martí, J.; Bolós, X.; Camacho, A. G.; Geyer, A.; Planagumà, Ll.; Ronchin, E.; Sánchez, A.

    2014-01-01

    We report new geophysical observations on the distribution of subsurface structures associated with monogenetic volcanism in the Garrotxa volcanic field (Northern Spain). As part of the Catalan Volcanic Zone, this Quaternary volcanic field is associated with the European rifts system. It contains the most recent and best preserved volcanic edifices of the Catalan Volcanic Zone with 38 monogenetic volcanoes identified in the Garrotxa Natural Park. We conducted new gravimetric and self-potential surveys to enhance our understanding of the relationship between the local geology and the spatial distribution of the monogenetic volcanoes. The main finding of this study is that the central part of the volcanic field is dominated by a broad negative Bouguer anomaly of around -0.5 mGal, within which a series of gravity minima are found with amplitudes of up to -2.3 mGal. Inverse modelling of the Bouguer data suggests that surficial low-density material dominates the volcanic field, most likely associated with effusive and explosive surface deposits. In contrast, an arcuate cluster of gravity minima to the NW of the Croscat volcano, the youngest volcano of this zone, is modelled by vertically extended low-density bodies, which we interpret as a complex ensemble of fault damage zones and the roots of young scoria cones. A ground-water infiltration zone identified by a self-potential anomaly is associated with a steep horizontal Bouguer gravity gradient and interpreted as a fault zone and/or magmatic fissure, which fed the most recent volcanic activity in the Garrotxa. Gravimetric and self-potential data are well correlated and indicate a control on the locations of scoria cones by NNE-SSW and NNW-SSE striking tectonic features, which intersect the main structural boundaries of the study area to the north and south. Our interpretation of the data is that faults facilitated magma ascent to the surface. Our findings have major implications for understanding the relationship

  12. Monitoring diffuse volcanic degassing during volcanic unrests: the case of Campi Flegrei (Italy).

    Science.gov (United States)

    Cardellini, C; Chiodini, G; Frondini, F; Avino, R; Bagnato, E; Caliro, S; Lelli, M; Rosiello, A

    2017-07-28

    In volcanoes with active hydrothermal systems, diffuse CO 2 degassing may constitute the primary mode of volcanic degassing. The monitoring of CO 2 emissions can provide important clues in understanding the evolution of volcanic activity especially at calderas where the interpretation of unrest signals is often complex. Here, we report eighteen years of CO 2 fluxes from the soil at Solfatara of Pozzuoli, located in the restless Campi Flegrei caldera. The entire dataset, one of the largest of diffuse CO 2 degassing ever produced, is made available for the scientific community. We show that, from 2003 to 2016, the area releasing deep-sourced CO 2 tripled its extent. This expansion was accompanied by an increase of the background CO 2 flux, over most of the surveyed area (1.4 km 2 ), with increased contributions from non-biogenic source. Concurrently, the amount of diffusively released CO 2 increased up to values typical of persistently degassing active volcanoes (up to 3000 t d -1 ). These variations are consistent with the increase in the flux of magmatic fluids injected into the hydrothermal system, which cause pressure increase and, in turn, condensation within the vapor plume feeding the Solfatara emission.

  13. Across-arc versus along-arc Sr-Nd-Pb isotope variations in the Ecuadorian volcanic arc

    Science.gov (United States)

    Ancellin, Marie-Anne; Samaniego, Pablo; Vlastélic, Ivan; Nauret, François; Gannoun, Adbelmouhcine; Hidalgo, Silvana

    2017-03-01

    Previous studies of the Ecuadorian arc (1°N-2°S) have revealed across-arc geochemical trends that are consistent with a decrease in mantle melting and slab dehydration away from the trench. The aim of this work is to evaluate how these processes vary along the arc in response to small-scale changes in the age of the subducted plate, subduction angle, and continental crustal basement. We use an extensive database of 1437 samples containing 71 new analyses, of major and trace elements as well as Sr-Nd-Pb isotopes from Ecuadorian and South Colombian volcanic centers. Large geochemical variations are found to occur along the Ecuadorian arc, in particular along the front arc, which encompasses 99% and 71% of the total variations in 206Pb/204Pb and 87Sr/86Sr ratios of Quaternary Ecuadorian volcanics, respectively. The front arc volcanoes also show two major latitudinal trends: (1) the southward increase of 207Pb/204Pb and decrease of 143Nd/144Nd reflect more extensive crustal contamination of magma in the southern part (up to 14%); and (2) the increase of 206Pb/204Pb and decrease of Ba/Th away from ˜0.5°S result from the changing nature of metasomatism in the subarc mantle wedge with the aqueous fluid/siliceous slab melt ratio decreasing away from 0.5°S. Subduction of a younger and warmer oceanic crust in the Northern part of the arc might promote slab melting. Conversely, the subduction of a colder oceanic crust south of the Grijalva Fracture Zone and higher crustal assimilation lead to the reduction of slab contribution in southern part of the arc.

  14. Volcanic systems of Iceland and their magma source

    Science.gov (United States)

    Sigmarsson, Olgeir

    2017-04-01

    Several active hot-spot volcanoes produce magma from mantle sources which composition varies on decadal time scale. This is probably best demonstrated by the recent work of Pietruszka and collaborators on Kilauea, Hawaii. In marked contrast, basalt lavas from volcanic system in Iceland located above the presumed centre of the Iceland mantle plume have uniform isotope composition over the last 10 thousand years. Volcanic systems are composed of a central volcano and a fissure swarm, or a combination of both and they represent a fundamental component of the neovolcanic zones in Iceland. Four such systems, those of Askja, Bárðarbunga, Kverkfjöll and Grímsvötn in central Iceland were chosen for investigation. The last three have central volcanoes covered by the Vatnajökull ice-sheet whereas part of their fissure swarms is ice-free. Tephra produced during subglacial eruptions together with lavas from the fissure swarms of Holocene age have been collected and analysed for Sr, Nd and Th isotope ratios. Those volcanic formations that can be univocally correlated to a given volcanic system display uniform isotope ratio but different from one volcanic system to another. An exception to this regularity is that Askja products have isotope ratios indistinguishable from those of Gímsvötn, but since these volcanic systems lies far apart their lava fields do not overlap. A practical aspect of these findings was demonstrated during the rifting event of Bárðarbunga and fissure eruption forming the Holuhraun lava field. Relatively low, O isotope ratios in these basalts and heterogeneous macrocrystal composition have been ascribed to important metabasaltic crustal contamination with or without crystal mush recycling. In that case a surprisingly efficient magma mixing and melt homogenization must have occurred in the past beneath the volcanic systems. One possibility is that during the rapid deglaciation much mantle melting occurred and melts accumulated at the mantle

  15. Volcanic unrest and hazard communication in Long Valley Volcanic Region, California

    Science.gov (United States)

    Hill, David P.; Mangan, Margaret T.; McNutt, Stephen R.

    2017-01-01

    The onset of volcanic unrest in Long Valley Caldera, California, in 1980 and the subsequent fluctuations in unrest levels through May 2016 illustrate: (1) the evolving relations between scientists monitoring the unrest and studying the underlying tectonic/magmatic processes and their implications for geologic hazards, and (2) the challenges in communicating the significance of the hazards to the public and civil authorities in a mountain resort setting. Circumstances special to this case include (1) the sensitivity of an isolated resort area to media hype of potential high-impact volcanic and earthquake hazards and its impact on potential recreational visitors and the local economy, (2) a small permanent population (~8000), which facilitates face-to-face communication between scientists monitoring the hazard, civil authorities, and the public, and (3) the relatively frequent turnover of people in positions of civil authority, which requires a continuing education effort on the nature of caldera unrest and related hazards. Because of delays associated with communication protocols between the State and Federal governments during the onset of unrest, local civil authorities and the public first learned that the U.S. Geological Survey was about to release a notice of potential volcanic hazards associated with earthquake activity and 25-cm uplift of the resurgent dome in the center of the caldera through an article in the Los Angeles Times published in May 1982. The immediate reaction was outrage and denial. Gradual acceptance that the hazard was real required over a decade of frequent meetings between scientists and civil authorities together with public presentations underscored by frequently felt earthquakes and the onset of magmatic CO2 emissions in 1990 following a 11-month long earthquake swarm beneath Mammoth Mountain on the southwest rim of the caldera. Four fatalities, one on 24 May 1998 and three on 6 April 2006, underscored the hazard posed by the CO2

  16. Galileo observations of volcanic plumes on Io

    Science.gov (United States)

    Geissler, P.E.; McMillan, M.T.

    2008-01-01

    Io's volcanic plumes erupt in a dazzling variety of sizes, shapes, colors and opacities. In general, the plumes fall into two classes, representing distinct source gas temperatures. Most of the Galileo imaging observations were of the smaller, more numerous Prometheus-type plumes that are produced when hot flows of silicate lava impinge on volatile surface ices of SO2. Few detections were made of the giant, Pele-type plumes that vent high temperature, sulfur-rich gases from the interior of Io; this was partly because of the insensitivity of Galileo's camera to ultraviolet wavelengths. Both gas and dust spout from plumes of each class. Favorably located gas plumes were detected during eclipse, when Io was in Jupiter's shadow. Dense dust columns were imaged in daylight above several Prometheus-type eruptions, reaching heights typically less than 100 km. Comparisons between eclipse observations, sunlit images, and the record of surface changes show that these optically thick dust columns are much smaller in stature than the corresponding gas plumes but are adequate to produce the observed surface deposits. Mie scattering calculations suggest that these conspicuous dust plumes are made up of coarse grained “ash” particles with radii on the order of 100 nm, and total masses on the order of 106 kg per plume. Long exposure images of Thor in sunlight show a faint outer envelope apparently populated by particles small enough to be carried along with the gas flow, perhaps formed by condensation of sulfurous “snowflakes” as suggested by the plasma instrumentation aboard Galileo as it flew through Thor's plume [Frank, L.A., Paterson, W.R., 2002. J. Geophys. Res. (Space Phys.) 107, doi:10.1029/2002JA009240. 31-1]. If so, the total mass of these fine, nearly invisible particles may be comparable to the mass of the gas, and could account for much of Io's rapid resurfacing.

  17. Magma wagging and whirling in volcanic conduits

    Science.gov (United States)

    Liao, Yang; Bercovici, David; Jellinek, Mark

    2018-02-01

    Seismic tremor characterized by 0.5-7 Hz ground oscillations commonly occur before and during eruptions at silicic volcanoes with widely ranging vent geometries and edifice structures. The ubiquitous characteristics of this tremor imply that its causes are potentially common to silicic volcanoes. Here we revisit and extend to three dimensions the magma-wagging model for tremor (Jellinek and Bercovici, 2011; Bercovici et al., 2013), wherein a stiff magma column rising in a vertical conduit oscillates against a surrounding foamy annulus of bubbly magma, giving rise to tremor. While prior studies were restricted to two-dimensional lateral oscillations, here we explore three-dimensional motion and additional modes of oscillations. In the absence of viscous damping, the magma column undergoes 'whirling' motion: the center of each horizontal section of the column traces an elliptical trajectory. In the presence of viscous effect we identify new 'coiling' and 'uncoiling' column bending shapes with relatively higher and comparable rates of dissipation to the original two-dimensional magma wagging model. We also calculate the seismic P-wave response of the crustal material around the volcanic conduit to the new whirling motions and propose seismic diagnostics for different wagging patterns using the time-lag between seismic stations. We test our model by analyzing pre-eruptive seismic data from the 2009 eruption of Redoubt Volcano. In addition to suggesting that the occurrence of elliptical whirling motion more than 1 week before the eruption, our analysis of seismic time-lags also implies that the 2009 eruption was accompanied by qualitative changes in the magma wagging behavior including fluctuations in eccentricity and a reversal in the direction of elliptical whirling motion when the eruption was immediately impending.

  18. Properties of volcanic soils in cold climate conditions

    Science.gov (United States)

    Kuznetsova, Elena

    2017-04-01

    Layers of volcanic ash and the Andosol soils derived from them may play an important role in preserving snow and ice as well as developing permafrost conditions in the immediate vicinity of volcanoes of high elevation or those situated at high latitudes, and land areas, often distant from volcanic activity that are either prone to permafrost or covered by snow and ice, but are affected by the deposition of subaerial ash. The special properties of volcanic ash that are responsible are critically reviewed particularly in relation to recent research in Kamchatka in the Far East of Russia. Of particular importance are the thermal properties and the unfrozen water contents of ash layers and the rate at which the weathering of volcanic glass takes place. Volcanic glass is the most easily weathered component of volcanic ejecta (Shoji et al., 1993; Kimble et al., 2000). There are many specific environmental conditions, including paleoclimate and present-day climate, the composition of volcanic tephra and glaciation history, which cause the differences in weathering and development of volcanic ash soils (Zehetner et al., 2003). The preservation of in situ, unweathered, and unaltered surficial ash-fall deposits in the cold regions has important implications for paleoclimate and glacial history. Ash-fall deposits, which trap and preserve the soils, sediments, and landforms on which they fall, can be used to resolve local climate conditions (temperature and moisture) at the ash site during ash-fall deposition. The preservation of detailed sedimentary features (e.g. bedding in the ash, sharpness of stratigraphic contacts) can tell us about their post-depositional history, whether they have been redeposited by wind or water, or overridden by glaciers (Marchant et al., 1996). Weathering of volcanic glass results in the development of amorphous clay minerals (e.g. allophane, opal, palagonite) but this takes place much slower in cold than under warmer climate conditions. Only few

  19. Virulence evolution at the front line of spreading epidemics.

    Science.gov (United States)

    Griette, Quentin; Raoul, Gaël; Gandon, Sylvain

    2015-11-01

    Understanding and predicting the spatial spread of emerging pathogens is a major challenge for the public health management of infectious diseases. Theoretical epidemiology shows that the speed of an epidemic is governed by the life-history characteristics of the pathogen and its ability to disperse. Rapid evolution of these traits during the invasion may thus affect the speed of epidemics. Here we study the influence of virulence evolution on the spatial spread of an epidemic. At the edge of the invasion front, we show that more virulent and transmissible genotypes are expected to win the competition with other pathogens. Behind the front line, however, more prudent exploitation strategies outcompete virulent pathogens. Crucially, even when the presence of the virulent mutant is limited to the edge of the front, the invasion speed can be dramatically altered by pathogen evolution. We support our analysis with individual-based simulations and we discuss the additional effects of demographic stochasticity taking place at the front line on virulence evolution. We confirm that an increase of virulence can occur at the front, but only if the carrying capacity of the invading pathogen is large enough. These results are discussed in the light of recent empirical studies examining virulence evolution at the edge of spreading epidemics. © 2015 The Author(s). Evolution © 2015 The Society for the Study of Evolution.

  20. Self-Propagating Reactive Fronts in Compacts of Multilayered Particles

    International Nuclear Information System (INIS)

    Sraj, I.; Vohra, M.; Alawieh, L.; Weihs, T.P.; Knio, O.M.

    2013-01-01

    Reactive multilayered foils in the form of thin films have gained interest in various applications such as joining, welding, and ignition. Typically, thin film multilayers support self-propagating reaction fronts with speeds ranging from 1 to 20 m/s. In some applications, however, reaction fronts with much smaller velocities are required. This recently motivated Fritz et al. (2011) to fabricate compacts of regular sized/shaped multilayered particles and demonstrate self-sustained reaction fronts having much smaller velocities than thin films with similar layering. In this work, we develop a simplified numerical model to simulate the self-propagation of reactive fronts in an idealized compact, comprising identical Ni/Al multilayered particles in thermal contact. The evolution of the reaction in the compact is simulated using a two-dimensional transient model, based on a reduced description of mixing, heat release, and thermal transport. Computed results reveal that an advancing reaction front can be substantially delayed as it crosses from one particle to a neighboring particle, which results in a reduced mean propagation velocity. A quantitative analysis is thus conducted on the dependence of these phenomena on the contact area between the particles, the thermal contact resistance, and the arrangement of the multilayered particles.

  1. Submesoscale CO2 variability across an upwelling front off Peru

    Science.gov (United States)

    Köhn, Eike E.; Thomsen, Sören; Arévalo-Martínez, Damian L.; Kanzow, Torsten

    2017-12-01

    As a major source for atmospheric CO2, the Peruvian upwelling region exhibits strong variability in surface fCO2 on short spatial and temporal scales. Understanding the physical processes driving the strong variability is of fundamental importance for constraining the effect of marine emissions from upwelling regions on the global CO2 budget. In this study, a frontal decay on length scales of 𝒪(10 km) was observed off the Peruvian coast following a pronounced decrease in down-frontal (equatorward) wind speed with a time lag of 9 h. Simultaneously, the sea-to-air flux of CO2 on the inshore (cold) side of the front dropped from up to 80 to 10 mmol m-2 day-1, while the offshore (warm) side of the front was constantly outgassing at a rate of 10-20 mmol m-2 day-1. Based on repeated ship transects the decay of the front was observed to occur in two phases. The first phase was characterized by a development of coherent surface temperature anomalies which gained in amplitude over 6-9 h. The second phase was characterized by a disappearance of the surface temperature front within 6 h. Submesoscale mixed-layer instabilities were present but seem too slow to completely remove the temperature gradient in this short time period. Dynamics such as a pressure-driven gravity current appear to be a likely mechanism behind the evolution of the front.

  2. Self-Propagating Reactive Fronts in Compacts of Multilayered Particles

    Directory of Open Access Journals (Sweden)

    Ihab Sraj

    2013-01-01

    Full Text Available Reactive multilayered foils in the form of thin films have gained interest in various applications such as joining, welding, and ignition. Typically, thin film multilayers support self-propagating reaction fronts with speeds ranging from 1 to 20 m/s. In some applications, however, reaction fronts with much smaller velocities are required. This recently motivated Fritz et al. (2011 to fabricate compacts of regular sized/shaped multilayered particles and demonstrate self-sustained reaction fronts having much smaller velocities than thin films with similar layering. In this work, we develop a simplified numerical model to simulate the self-propagation of reactive fronts in an idealized compact, comprising identical Ni/Al multilayered particles in thermal contact. The evolution of the reaction in the compact is simulated using a two-dimensional transient model, based on a reduced description of mixing, heat release, and thermal transport. Computed results reveal that an advancing reaction front can be substantially delayed as it crosses from one particle to a neighboring particle, which results in a reduced mean propagation velocity. A quantitative analysis is thus conducted on the dependence of these phenomena on the contact area between the particles, the thermal contact resistance, and the arrangement of the multilayered particles.

  3. Light-front QCD. II. Two-component theory

    International Nuclear Information System (INIS)

    Zhang, W.; Harindranath, A.

    1993-01-01

    The light-front gauge A a + =0 is known to be a convenient gauge in practical QCD calculations for short-distance behavior, but there are persistent concerns about its use because of its ''singular'' nature. The study of nonperturbative field theory quantizing on a light-front plane for hadronic bound states requires one to gain a priori systematic control of such gauge singularities. In the second paper of this series we study the two-component old-fashioned perturbation theory and various severe infrared divergences occurring in old-fashioned light-front Hamiltonian calculations for QCD. We also analyze the ultraviolet divergences associated with a large transverse momentum and examine three currently used regulators: an explicit transverse cutoff, transverse dimensional regularization, and a global cutoff. We discuss possible difficulties caused by the light-front gauge singularity in the applications of light-front QCD to both old-fashioned perturbative calculations for short-distance physics and upcoming nonperturbative investigations for hadronic bound states

  4. Suitability of simple rheological laws for the numerical simulation of dense pyroclastic flows and long-runout volcanic avalanches

    Science.gov (United States)

    Kelfoun, Karim

    2011-08-01

    The rheology of volcanic rock avalanches and dense pyroclastic flows is complex, and it is difficult at present to constrain the physics of their processes. The problem lies in defining the most suitable parameters for simulating the behavior of these natural flows. Existing models are often based on the Coulomb rheology, sometimes with a velocity-dependent stress (e.g., Voellmy), but other laws have also been used. Here I explore the characteristics of flows, and their deposits, obtained on simplified topographies by varying source conditions and rheology. The Coulomb rheology, irrespective of whether there is a velocity-dependent stress, forms cone-shaped deposits that do not resemble those of natural long-runout events. A purely viscous or a purely turbulent flow can achieve realistic velocities and thicknesses but cannot form a deposit on slopes. The plastic rheology, with (e.g., Bingham) or without a velocity-dependent stress, is more suitable for the simulation of dense pyroclastic flows and long-runout volcanic avalanches. With this rheology, numerical flows form by pulses, which are often observed during natural flow emplacement. The flows exhibit realistic velocities and deposits of realistic thicknesses. The plastic rheology is also able to generate the frontal lobes and lateral levées which are commonly observed in the field. With the plastic rheology, levée formation occurs at the flow front due to a divergence of the driving stresses at the edges. Once formed, the levées then channel the remaining flow mass. The results should help future modelers of volcanic flows with their choice of which mechanical law corresponds best to the event they are studying.

  5. Groundwater characteristics and problems in volcanic rock terrains

    International Nuclear Information System (INIS)

    Custodio, E.

    1989-01-01

    Volcanic rock formations, each with their own particular hydrogeological characteristics, occur in circumstances that cover a multiplicity of situations. These range from permeable porous rock formations to permeable fissured formations and include all types of intermediate situation between the two. The type of volcanism, distance from the source of emission, age, alteration processes and tectonics are all factors which determine their behaviour. Volcanic formations usually constitute a single aquifer system, even though this may be very heterogeneous and may locally be separated into clearly defined subunits. At times, formations may be hundreds of metres thick and are fairly permeable almost throughout. As a rule, volcanic material does not yield directly soluble salts to the water that flows through it. Mineralization of the water is due to the concentration of rainfall and the hydrolysis of silicates as a result of CO 2 being absorbed from the atmosphere and the ground, or as a result of volcanism itself. Cationic grouping is usually closely correlated to that of the rock formation in which the chemical composition is formed. Most environmental isotope and radioisotope techniques may be used, and at times are of unquestionable value. However, the existence of evaporation in the soil with possible isotopic fractionation, the effects of marked relief, the dilution of dissolved carbon by volcanic carbon and isotopic exchange brought about by volcanic carbon, etc., should be taken into account before valid conclusions are drawn. The paper uses examples taken from existing studies, mainly those being carried out in the Canary Islands (Spain). (author). 98 refs, 18 figs, 4 tabs

  6. Pseudotachylyte formation in volcanic conduits: Montserrat vs. Mount St. Helens

    Science.gov (United States)

    Kendrick, J. E.; Lavallee, Y.; Petrakova, L.; Ferk, A.; Di Toro, G.; Hess, K.; Ferri, F.; Dingwell, D. B.

    2012-12-01

    Seismogenic fracture and faulting may result in non-equilibrium frictional melting of rock, which upon cooling and recrystallisation forms pseudotachylyte. In volcanic environments, the transition from endogenous to exogenous growth can be attributed to a shift in magma rheology into the brittle regime, and thus the ascent of high-viscosity magma can form discrete shear zones, comparable to tectonic faults, along conduit margins. Pseudotachylytes have, until now, rarely been noted in exogenous volcanic materials and seldom in active volcanic environments. This is despite the simultaneous occurrence of high pressures and differential stresses, which make high-viscosity magmas ideal candidates for the occurrence of frictional melting. Here, we compare the chemical, thermal, magnetic and structural properties of two candidate volcanic pseudotachylytes; one from Soufriere Hills (Montserrat) and one from Mount St. Helens (USA). Additionally, we present data from a set of high-velocity rotary shear experiments on the host materials of these natural pseudotachylytes in which melting was induced after just 10's of centimeters of slip at realistic extrusion velocities (0.4 - 1.6 ms-1) and low normal stresses (0.5-2 MPa). After 1-2 meters of slip a continuous melt layer formed, at which point friction decreased and the fault zone displayed slip-weakening behaviour. For volcanic conduits, this would facilitate temporarily elevated slip rates, or an increase in extrusion rate, and could cause transitions in dome morphology and eruption style. This study demonstrates that shear fracturing in magma or sliding along conduit margins can readily result in frictional melting. The conspicuous absence of pseudotachylytes in active volcanic environments is likely the result of exceptionally high background temperatures which precipitate near-equilibrium melting, thereby obviating one of the characteristic signatures of pseudotachylyte - glassy protomelts formed by selective melting of

  7. Critical review of a new volcanic eruption chronology

    Science.gov (United States)

    Neuhäuser, Dagmar L.; Neuhäuser, Ralph

    2016-04-01

    Sigl. et al. (2015, Nature) present historical evidence for 32 volcanic eruptions to evaluate their new polar ice core 10-Be chronology - 24 are dated within three years of sulfur layers in polar ice. Most of them can be interpreted as weather phenomena (Babylonia: disk of sun like moon, reported for only one day, e.g. extinction due to clouds), Chinese sunspot reports (pellet, black vapor, etc.), solar eclipses, normal ice-halos and coronae (ring, bow, etc.), one aurora (redness), red suns due to mist drops in wet fog or fire-smoke, etc. Volcanic dust may facilitate detections of sunspots and formation of Bishop's ring, but tend to inhibit ice-halos, which are otherwise often reported in chronicles. We are left with three reports possibly indicating volcanic eruptions, namely fulfilling genuine criteria for atmospheric disturbances due to volcanic dust, e.g. bluish or faint sun, orange sky, or fainting of stars for months (BCE 208, 44-42, and 32). Among the volcanic eruptions used to fix the chronology (CE 536, 626, 939, 1257), the reports cited for the 930s deal only with 1-2 days, at least one reports an eclipse. In the new chronology, there is a sulfur detection eight years after the Vesuvius eruption, but none in CE 79. It may appear surprising that, from BCE 500 to 1, all five northern sulfur peaks labeled in figure 2 in Sigl et al. are systematically later by 2-4 years than the (corresponding?) southern peaks, while all five southern peaks from CE 100 to 600 labeled in figure 2 are systematically later by 1-4 years than the (corresponding?) northern peaks. Furthermore, in most of their six strongest volcanic eruptions, temperatures decreased years before their sulfur dating - correlated with weak solar activity as seen in radiocarbon, so that volcanic climate forcing appears dubious here. Also, their 10-Be peaks at CE 775 and 994 are neither significant nor certain in dating.

  8. The volcanic rocks construction of the late paleozoic era and uranium mineralization in Beishan area of Gansu province

    International Nuclear Information System (INIS)

    An Zhengchang; Luo Xiaoqiang

    2010-01-01

    Late Paleozoic volcanic rocks in Beishan area are the favorable constructions of hydrothermal type and volcanic type deposit. From the distribution of volcanic rocks, the volcanic compositions, the volcanic facies, volcanic eruption method and rhythm, chemical and trace elements compositions, and so on, it discusses the characteristics of the Late Devonian volcanic construction in this area and its relationship with uranium mineralization, analyzes the role of volcanic ore-control mechanism, and summarizes uranium ore forming regularity of volcanic construction in Late Paleozoic. (authors)

  9. The onset of the volcanism in the Ciomadul Volcanic Dome Complex (Eastern Carpathians): Eruption chronology and magma type variation

    Science.gov (United States)

    Molnár, Kata; Harangi, Szabolcs; Lukács, Réka; Dunkl, István; Schmitt, Axel K.; Kiss, Balázs; Garamhegyi, Tamás; Seghedi, Ioan

    2018-04-01

    Combined zircon U-Th-Pb and (U-Th)/He dating was applied to refine the eruption chronology of the last 2 Myr for the andesitic and dacitic Pilişca volcano and Ciomadul Volcanic Dome Complex (CVDC), the youngest volcanic area of the Carpathian-Pannonian region, located in the southernmost Harghita, eastern-central Europe. The proposed eruption ages, which are supported also by the youngest zircon crystallization ages, are much younger than the previously determined K/Ar ages. By dating every known eruption center in the CVDC, repose times between eruptive events were also accurately determined. Eruption of the andesite at Murgul Mare (1865 ± 87 ka) and dacite of the Pilişca volcanic complex (1640 ± 37 ka) terminated an earlier pulse of volcanic activity within the southernmost Harghita region, west of the Olt valley. This was followed by the onset of the volcanism in the CVDC, which occurred after several 100s kyr of eruptive quiescence. At ca. 1 Ma a significant change in the composition of erupted magma occurred from medium-K calc-alkaline compositions to high-K dacitic (Baba-Laposa dome at 942 ± 65 ka) and shoshonitic magmas (Malnaş and Bixad domes; 964 ± 46 ka and 907 ± 66 ka, respectively). Noteworthy, eruptions of magmas with distinct chemical compositions occurred within a restricted area, a few km from one another. These oldest lava domes of the CVDC form a NNE-SSW striking tectonic lineament along the Olt valley. Following a brief (ca. 100 kyr) hiatus, extrusion of high-K andesitic magma continued at Dealul Mare (842 ± 53 ka). After another ca. 200 kyr period of quiescence two high-K dacitic lava domes extruded (Puturosul: 642 ± 44 ka and Balvanyos: 583 ± 30 ka). The Turnul Apor lava extrusion occurred after a ca. 200 kyr repose time (at 344 ± 33 ka), whereas formation of the Haramul Mic lava dome (154 ± 16 ka) represents the onset of the development of the prominent Ciomadul volcano. The accurate determination of eruption dates shows that the

  10. Division of volcanic activity cycles in the late mesozoic in South Jiangxi and North Guangdong

    International Nuclear Information System (INIS)

    Li Qinglong; Wu Jianhua

    1999-01-01

    Based on stratigraphical unconformity, rock association, fossil assemblage, isotope age and tectonic features, the volcanic activity in late Mesozoic in south Jiangxi and north Guandong can be divided into four cycles: Yutian volcanic activity cycle, Lianhuazhai volcanic activity cycle. Banshi volcanic activity cycle and Nanxiong volcanic activity cycle. Yutian volcanic cycle which occurs in middle Jurassic epoch is the bimodal rock association composed of rhyolite and basalt. Lianhuazhai volcanic cycle which occurs in late Jurassic epoch is unimodal rock association composed of rhyolite. Banshi volcanic cycle occurs from the late stage of early Cretaceous to the early stage of late Cretaceous epoch. There are two types of rock associations related to this cycle: unimodal rock association composed of rhyolite or basalt and bimodal rock association composed of rhyolite and basalt. Nanxiong volcanic activity cycle which occurred in late stage of late Cretaceous epoch is the unimodal rock association composed of basalt which is the interlayer of the red sedimentary series

  11. Recognizing subtle evidence for silicic magma derivation from petrochemically-similar arc crust: Isotopic and chemical evidence for the bimodal volcanic series of Gorely Volcanic Center, Kamchatka, Russia

    Science.gov (United States)

    Seligman, A. N.; Bindeman, I. N.; Ellis, B. S.; Ponomareva, V.; Leonov, V.

    2012-12-01

    The Kamchatka Peninsula is home to some of the most prolific subduction related volcanic activity in the world. Gorely caldera and its central volcano are located in the rear of its currently active Eastern Volcanic Front. Recent work determined the presence of explosive ignimbrite eruptions sourced from Gorely volcano during the Pleistocene. We studied 32 eruptive units, including tephrochronologically-dated Holocene tephra, stratigraphically-arranged ignimbrites, as well as pre- and post-caldera lavas. We analyzed oxygen isotope ratios of pyroxene and plagioclase grains by laser fluorination, and major and trace element compositions of whole rocks. In addition, we determined 87Sr/86Sr and 143Nd/144Nd ratios of caldera-forming ignimbrite eruptions. Chemical compositions show that Gorely eruptive units range from basalt to basaltic andesite in the "Pra-Gorely" stages prior to caldera formation and the modern Gorely stages forming its current edifice. In contrast, eruptive material from earlier ignimbrites exposed at Opasny Ravine consists primarily of dacite. Whole rock analyses for Gorely indicate that silicic rocks and ignimbrites volumetrically dominate all other products, forming separate bimodal peaks in our SiO2-frequency diagram. In addition, trace element concentrations and ratios define two trends, one for more silicic and another for more mafic material. δ18Omelt values range from a low of 4.85 up to 6.22‰, where the lowest value was found in the last caldera forming eruption, suggesting incorporation of hydrothermally-altered material from earlier eruptions. 87Sr/86Sr and 143Nd/144Nd ratios range from 0.70328 to 0.70351 and from 0.51303 to 0.51309 respectively, with higher and more diverse values being characteristic of earlier ignimbrite units; again suggesting incorporation of surrounding crustal material. In contrast to these results, MELTS modeling using a variety of likely primitive basalts from Gorely shows it is possible to obtain silicic

  12. Light-front field theory in the description of hadrons

    Directory of Open Access Journals (Sweden)

    Ji Chueng-Ryong

    2017-01-01

    Full Text Available We discuss the use of light-front field theory in the descriptions of hadrons. In particular, we clarify the confusion in the prevailing notion of the equivalence between the infinite momentum frame and the light-front dynamics and the advantage of the light-front dynamics in hadron physics. As an application, we present our recent work on the flavor asymmetry in the proton sea and identify the presence of the delta-function contributions associated with end-point singularities arising from the chiral effective theory calculation. The results pave the way for phenomenological applications of pion cloud models that are manifestly consistent with the chiral symmetry properties of QCD.

  13. Finite-time barriers to reaction front propagation

    Science.gov (United States)

    Locke, Rory; Mahoney, John; Mitchell, Kevin

    2015-11-01

    Front propagation in advection-reaction-diffusion systems gives rise to rich geometric patterns. It has been shown for time-independent and time-periodic fluid flows that invariant manifolds, termed burning invariant manifolds (BIMs), serve as one-sided dynamical barriers to the propagation of reaction front. More recently, theoretical work has suggested that one-sided barriers, termed burning Lagrangian Coherent structures (bLCSs), exist for fluid velocity data prescribed over a finite time interval, with no assumption on the time-dependence of the flow. In this presentation, we use a time-varying fluid ``wind'' in a double-vortex channel flow to demonstrate that bLCSs form the (locally) most attracting or repelling fronts.

  14. Methods for enhancing mapping of thermal fronts in oil recovery

    Science.gov (United States)

    Lee, D.O.; Montoya, P.C.; Wayland, J.R. Jr.

    1984-03-30

    A method for enhancing the resistivity contrasts of a thermal front in an oil recovery production field as measured by the controlled source audio frequency magnetotelluric (CSAMT) technique is disclosed. This method includes the steps of: (1) preparing a CSAMT-determined topological resistivity map of the production field; (2) introducing a solution of a dopant material into the production field at a concentration effective to alter the resistivity associated with the thermal front; said dopant material having a high cation exchange capacity which might be selected from the group consisting of montmorillonite, illite, and chlorite clays; said material being soluble in the conate water of the production field; (3) preparing a CSAMT-determined topological resistivity map of the production field while said dopant material is moving therethrough; and (4) mathematically comparing the maps from step (1) and step (3) to determine the location of the thermal front. This method is effective with the steam flood, fire flood and water flood techniques.

  15. General motors front wheel drive 2-mode hybrid transmission

    Energy Technology Data Exchange (ETDEWEB)

    Hendrickson, James [General Motors Corp., Pontiac, MI (United States). New Transmission Products Group.; Holmes, Alan G. [General Motors Corp., Pontiac, MI (United States). Powertrain Hybrid Architecture

    2009-07-01

    General Motors now expands the application of two-mode hybrid technology to front wheel drive vehicles with the development of a hybrid electric transmission packaged into essentially the same space as a conventional automatic transmission for front wheel drive. This was accomplished using a space-efficient arrangement based on two planetary gear sets and electric motor-generators with large internal diameters. A combination of damper and hydraulically-controlled clutch allow comfortable shutdown and restarting of large-displacement engines in front wheel drive vehicles. The hybrid system delivers electric low-speed urban driving, two continuously variable ranges of transmission speed ratios, four fixed transmission speed ratios, electric acceleration boosting, and regenerative braking. In the first vehicle application, the two-mode hybrid helps to reduce vehicle fuel consumption by approximately one-third. (orig.)

  16. Concepts for a Muon Accelerator Front-End

    Energy Technology Data Exchange (ETDEWEB)

    Stratakis, Diktys [Fermilab; Berg, Scott [Brookhaven; Neuffer, David [Fermilab

    2017-03-16

    We present a muon capture front-end scheme for muon based applications. In this Front-End design, a proton bunch strikes a target and creates secondary pions that drift into a capture channel, decaying into muons. A series of rf cavities forms the resulting muon beams into a series of bunches of differerent energies, aligns the bunches to equal central energies, and initiates ionization cooling. We also discuss the design of a chicane system for the removal of unwanted secondary particles from the muon capture region and thus reduce activation of the machine. With the aid of numerical simulations we evaluate the performance of this Front-End scheme as well as study its sensitivity against key parameters such as the type of target, the number of rf cavities and the gas pressure of the channel.

  17. FRONT AXLE OF MERCEDES AMG GT. MODELLING IN AUTODESK INVENTOR

    Directory of Open Access Journals (Sweden)

    COROLENCU Eduard – Narcis

    2017-05-01

    Full Text Available This paper analyzes the front axle of the Mercedes AMG GT model, as so as the graphical representation of the axle and of the subassemblies of suspension system and steering system, using the AutoCAD and Autodesk Inventor software. The paper include the steps for made the 3D model of the front axle in order to highlight the advantages of suspension and steering system, the function of this systems and methods for manufacturing of these. The 3D model presents a suite of complex surfaces. This type of surfaces is often designed with non-analytical means. The main commands and options used in Autodesk Inventor software were presented and explained. All the component parts of the front axle were modelled and assembled according to their functional role. Finally, the models were rendered in order to have a realistic appearance.

  18. Lithium, boron and chloride in volcanics and greywackes in Northland, Auckland and the Taupo Volcanic Zone

    International Nuclear Information System (INIS)

    Reyes, A.G.; Trompetter, W.J.

    1998-01-01

    During magmatic differentiation processes B preferentially partitions into the glassy mesostasis of rhyolite and andesite. The behaviour of Li, on the other hand, varies with the silica content of the rock. Lithium, B, Cl and water contents increase proportionally with the silica concentration of the volcanic rocks. Their relative proportions in andesites of the Taupo Volcanic Zone (TVZ) appear to reflect the nature of the underlying crust, the dip of the subducting slab and hence the depth and temperature of magma generation. The B/Li ratios of rhyolites associated with the northern Rotorua and Okataina eruptive centres yield lower B/Li ratios than those from Maroa and Taupo centres in the south, where the slab subducts at a shallower angle. Apparently, volcanics associated with a younger subduction event as in the TVZ, contain and retain more Cl, yielding lower Li/Cl ratios for the TVZ than Northland-Auckland basalts. The B/Li ratio of greywackes from the Torlesse terrane ( 1.4). In geothermal wells in Ngawha, hydrothermal alteration yields higher B/Li ratios of >2.8 for Waipapa terrane sedimentary rocks. The Li/Cl ratios for average South and North Island greywackes are similar and may reflect similar degrees of metamorphism. In general, the relative Li, B and Cl contents in greywackes are dictated by the composition of the detrital fragments, the clay fraction, the type of clays and the metamorphic grade. During hydrothermal alteration of rhyolite in the TVZ, Cl always partitions into solution while Li and B have an affinity for the rock. However, more Li remains in the rock than B at any given temperature. The distribution coefficients of Li and B between water and rock increase with increasing temperature. The partitioning of Li between rock and solution in TVZ hydrothermal systems is mainly dictated by temperature, whereas the mass distribution coefficient for B is related to the tectonic setting. An increase in relative Li of the rock is associated with the

  19. Global volcanic aerosol properties derived from emissions, 1990-2014, using CESM1(WACCM): VOLCANIC AEROSOLS DERIVED FROM EMISSIONS

    Energy Technology Data Exchange (ETDEWEB)

    Mills, Michael J. [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Schmidt, Anja [School of Earth and Environment, University of Leeds, Leeds UK; Easter, Richard [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Solomon, Susan [Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge Massachusetts USA; Kinnison, Douglas E. [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Ghan, Steven J. [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Neely, Ryan R. [School of Earth and Environment, University of Leeds, Leeds UK; National Centre for Atmospheric Science, University of Leeds, Leeds UK; Marsh, Daniel R. [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Conley, Andrew [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Bardeen, Charles G. [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Gettelman, Andrew [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA

    2016-03-06

    Accurate representation of global stratospheric aerosol properties from volcanic and non-volcanic sulfur emissions is key to understanding the cooling effects and ozone-loss enhancements of recent volcanic activity. Attribution of climate and ozone variability to volcanic activity is of particular interest in relation to the post-2000 slowing in the apparent rate of global average temperature increases, and variable recovery of the Antarctic ozone hole. We have developed a climatology of global aerosol properties from 1990 to 2014 calculated based on volcanic and non-volcanic emissions of sulfur sources. We have complied a database of volcanic SO2 emissions and plume altitudes for eruptions between 1990 and 2014, and a new prognostic capability for simulating stratospheric sulfate aerosols in version 5 of the Whole Atmosphere Community Climate Model, a component of the Community Earth System Model. Our climatology shows remarkable agreement with ground-based lidar observations of stratospheric aerosol optical depth (SAOD), and with in situ measurements of aerosol surface area density (SAD). These properties are key parameters in calculating the radiative and chemical effects of stratospheric aerosols. Our SAOD climatology represents a significant improvement over satellite-based analyses, which ignore aerosol extinction below 15 km, a region that can contain the vast majority of stratospheric aerosol extinction at mid- and high-latitudes. Our SAD climatology significantly improves on that provided for the Chemistry-Climate Model Initiative, which misses 60% of the SAD measured in situ. Our climatology of aerosol properties is publicly available on the Earth System Grid.

  20. Months between rejuvenation and volcanic eruption at Yellowstone caldera, Wyoming

    Science.gov (United States)

    Till, Christy B.; Vazquez, Jorge A.; Boyce, Jeremy W

    2015-01-01

    Rejuvenation of previously intruded silicic magma is an important process leading to effusive rhyolite, which is the most common product of volcanism at calderas with protracted histories of eruption and unrest such as Yellowstone, Long Valley, and Valles, USA. Although orders of magnitude smaller in volume than rare caldera-forming super-eruptions, these relatively frequent effusions of rhyolite are comparable to the largest eruptions of the 20th century and pose a considerable volcanic hazard. However, the physical pathway from rejuvenation to eruption of silicic magma is unclear particularly because the time between reheating of a subvolcanic intrusion and eruption is poorly quantified. This study uses geospeedometry of trace element profiles with nanometer resolution in sanidine crystals to reveal that Yellowstone’s most recent volcanic cycle began when remobilization of a near- or sub-solidus silicic magma occurred less than 10 months prior to eruption, following a 220,000 year period of volcanic repose. Our results reveal a geologically rapid timescale for rejuvenation and effusion of ~3 km3 of high-silica rhyolite lava even after protracted cooling of the subvolcanic system, which is consistent with recent physical modeling that predict a timescale of several years or less. Future renewal of rhyolitic volcanism at Yellowstone is likely to require an energetic intrusion of mafic or silicic magma into the shallow subvolcanic reservoir and could rapidly generate an eruptible rhyolite on timescales similar to those documented here.

  1. Volcanic influence on centennial to millennial Holocene Greenland temperature change.

    Science.gov (United States)

    Kobashi, Takuro; Menviel, Laurie; Jeltsch-Thömmes, Aurich; Vinther, Bo M; Box, Jason E; Muscheler, Raimund; Nakaegawa, Toshiyuki; Pfister, Patrik L; Döring, Michael; Leuenberger, Markus; Wanner, Heinz; Ohmura, Atsumu

    2017-05-03

    Solar variability has been hypothesized to be a major driver of North Atlantic millennial-scale climate variations through the Holocene along with orbitally induced insolation change. However, another important climate driver, volcanic forcing has generally been underestimated prior to the past 2,500 years partly owing to the lack of proper proxy temperature records. Here, we reconstruct seasonally unbiased and physically constrained Greenland Summit temperatures over the Holocene using argon and nitrogen isotopes within trapped air in a Greenland ice core (GISP2). We show that a series of volcanic eruptions through the Holocene played an important role in driving centennial to millennial-scale temperature changes in Greenland. The reconstructed Greenland temperature exhibits significant millennial correlations with K + and Na + ions in the GISP2 ice core (proxies for atmospheric circulation patterns), and δ 18 O of Oman and Chinese Dongge cave stalagmites (proxies for monsoon activity), indicating that the reconstructed temperature contains hemispheric signals. Climate model simulations forced with the volcanic forcing further suggest that a series of large volcanic eruptions induced hemispheric-wide centennial to millennial-scale variability through ocean/sea-ice feedbacks. Therefore, we conclude that volcanic activity played a critical role in driving centennial to millennial-scale Holocene temperature variability in Greenland and likely beyond.

  2. Monitoring the Sumatra volcanic arc with InSAR

    Science.gov (United States)

    Chaussard, E.; Hong, S.; Amelung, F.

    2009-12-01

    The Sumatra volcanic arc is the result of the subduction of the Indo-Australian plate under the Sunda plate. The arc consists of 35 known volcanic centers, subaerials on the west coast of the Sumatra and Andaman Islands and submarines between these islands. Six active centers are known in the Sumatra volcanic arc. Surface deformation in volcanic areas usually indicates movement of magma or hydrothermal fluids at depth. Here we present a satellite-based Interferometric synthetic aperture radar (InSAR) survey of the Sumatra volcanic arc using ALOS data. Spanning the years 2007 to beginning of 2009, our survey reveals the background level of activity of the 35 volcanoes. We processed data from 40 tracks (24 in descending orbit and 16 in ascending orbit) to cover the whole Sumatra arc. In the first results five of these six known active centers show no sign of activity: Dempo, Kaba, Marapi, Talang and Peuet. The remaining active volcano, Mount Kerinci, has an ambiguous signal. We used pair-wise logic and InSAR time series of the available ALOS data to determine if the observed InSAR signal is caused by ground deformation or by atmospheric delays.

  3. Radon gas as a tracer for volcanic processes

    International Nuclear Information System (INIS)

    Thomas, D.M.

    1990-01-01

    Radon emissions from volcanic systems have been under investigation for several decades. Soil gas and groundwater radon activities have been used to map faults and to characterize geothermal systems, and measurements of atmospheric radon and radon daughter concentrations have been used to estimate the volume of magma chambers feeding active eruptions. Several studies have also shown that temporal variations in radon concentration have been associated with the onset of volcanic eruptions or changes in the rates or character of an eruption. Some of these studies have been able to clearly define the cause of the radon anomalies but others have proposed models of radon emission and transport that are not well supported by the known physical and chemical processes that occur in a volcanic system. In order to better characterize the processes that control radon activities in volcanic systems, it is recommended that future radon monitoring programs attempt to maintain continuous recording of radon activities; individual radon measurements should be made over the shortest time intervals possible that are consistent with acceptable counting statistics and geophysical, meteorological, and hydrological parameters should be measured in order to better define the physical processes that affect radon activities in volcanic systems. (author). 63 refs

  4. Global monsoon precipitation responses to large volcanic eruptions

    Science.gov (United States)

    Liu, Fei; Chai, Jing; Wang, Bin; Liu, Jian; Zhang, Xiao; Wang, Zhiyuan

    2016-01-01

    Climate variation of global monsoon (GM) precipitation involves both internal feedback and external forcing. Here, we focus on strong volcanic forcing since large eruptions are known to be a dominant mechanism in natural climate change. It is not known whether large volcanoes erupted at different latitudes have distinctive effects on the monsoon in the Northern Hemisphere (NH) and the Southern Hemisphere (SH). We address this issue using a 1500-year volcanic sensitivity simulation by the Community Earth System Model version 1.0 (CESM1). Volcanoes are classified into three types based on their meridional aerosol distributions: NH volcanoes, SH volcanoes and equatorial volcanoes. Using the model simulation, we discover that the GM precipitation in one hemisphere is enhanced significantly by the remote volcanic forcing occurring in the other hemisphere. This remote volcanic forcing-induced intensification is mainly through circulation change rather than moisture content change. In addition, the NH volcanic eruptions are more efficient in reducing the NH monsoon precipitation than the equatorial ones, and so do the SH eruptions in weakening the SH monsoon, because the equatorial eruptions, despite reducing moisture content, have weaker effects in weakening the off-equatorial monsoon circulation than the subtropical-extratropical volcanoes do. PMID:27063141

  5. Lahar—River of volcanic mud and debris

    Science.gov (United States)

    Major, Jon J.; Pierson, Thomas C.; Vallance, James W.

    2018-05-09

    Lahar, an Indonesian word for volcanic mudflow, is a mixture of water, mud, and volcanic rock flowing swiftly along a channel draining a volcano. Lahars can form during or after eruptions, or even during periods of inactivity. They are among the greatest threats volcanoes pose to people and property. Lahars can occur with little to no warning, and may travel great distances at high speeds, destroying or burying everything in their paths.Lahars form in many ways. They commonly occur when eruptions melt snow and ice on snow-clad volcanoes; when rains fall on steep slopes covered with fresh volcanic ash; when crater lakes, volcano glaciers or lakes dammed by volcanic debris suddenly release water; and when volcanic landslides evolve into flowing debris. Lahars are especially likely to occur at erupting or recently active volcanoes.Because lahars are so hazardous, U.S. Geological Survey scientists pay them close attention. They study lahar deposits and limits of inundation, model flow behavior, develop lahar-hazard maps, and work with community leaders and governmental authorities to help them understand and minimize the risks of devastating lahars.

  6. Eruptive history of the Elysium volcanic province of Mars

    International Nuclear Information System (INIS)

    Tanaka, K.L.; Scott, D.H.

    1987-01-01

    New geologic mapping of the Elysium volcanic province at 1:2,000,000 scale and crater counts provide a basis for describing its overall eruptive history. Four stages are listed and described in order of their relative age. They are also distinguished by eruption style and location. Stage 1: Central volcanism at Hecates and Albor Tholi. Stage 2: Shield and complex volcanism at Elysium Mons and Elysium Fossae. Stage 3: Rille volcanism at Elysium Fossae and Utopia Planitia. Stage 4: Flood lava and pyroclastic eruptions at Hecates Tholus and Elysium Mons. Tectonic and channeling activity in the Elysium region is intimately associated with volcanism. Recent work indicates that isostatic uplift of Tharsis, loading by Elysium Mons, and flexural uplift of the Elysium rise produced the stresses responsible for the fracturing and wrinkle-ridge formation in the region. Coeval faulting and channel formation almost certainly occurred in the pertinent areas in Stages 2 to 4. Older faults east of the lava flows and channels on Hecates Tholus may be coeval with Stage 1

  7. 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.

  8. Global monsoon precipitation responses to large volcanic eruptions.

    Science.gov (United States)

    Liu, Fei; Chai, Jing; Wang, Bin; Liu, Jian; Zhang, Xiao; Wang, Zhiyuan

    2016-04-11

    Climate variation of global monsoon (GM) precipitation involves both internal feedback and external forcing. Here, we focus on strong volcanic forcing since large eruptions are known to be a dominant mechanism in natural climate change. It is not known whether large volcanoes erupted at different latitudes have distinctive effects on the monsoon in the Northern Hemisphere (NH) and the Southern Hemisphere (SH). We address this issue using a 1500-year volcanic sensitivity simulation by the Community Earth System Model version 1.0 (CESM1). Volcanoes are classified into three types based on their meridional aerosol distributions: NH volcanoes, SH volcanoes and equatorial volcanoes. Using the model simulation, we discover that the GM precipitation in one hemisphere is enhanced significantly by the remote volcanic forcing occurring in the other hemisphere. This remote volcanic forcing-induced intensification is mainly through circulation change rather than moisture content change. In addition, the NH volcanic eruptions are more efficient in reducing the NH monsoon precipitation than the equatorial ones, and so do the SH eruptions in weakening the SH monsoon, because the equatorial eruptions, despite reducing moisture content, have weaker effects in weakening the off-equatorial monsoon circulation than the subtropical-extratropical volcanoes do.

  9. Io - One of at Least Four Simultaneous Erupting Volcanic Eruptions

    Science.gov (United States)

    1979-01-01

    This photo of an active volcanic eruption on Jupiter's satellite Io was taken 1 hour, 52 minutes after the accompanying picture, late in the evening of March 4, 1979, Pacific time. On the limb of the satellite can be seen one of at least four simultaneous volcanic eruptions -- the first such activity ever observed on another celestial body. Seen against the limb are plume-like structures rising more than 60 miles (100 kilometers) above the surface. Several eruptions have been identified with volcanic structures on the surface of Io, which have also been identified by Voyager 1's infrared instrument as being abnormally hot -- several hundred degrees warmer than surrounding terrain. The fact that several eruptions appear to be occurring at the same time suggests that Io has the most active surface in the solar system and that volcanism is going on there essentially continuously. Another characteristic of the observed volcanism is that it appears to be extremely explosive, with velocities more than 2,000 miles an hour (at least 1 kilometer per second). That is more violent than terrestrial volcanoes like Etna, Vesuvius or Krakatoa.

  10. Systematic change in global patterns of streamflow following volcanic eruptions.

    Science.gov (United States)

    Iles, Carley E; Hegerl, Gabriele C

    2015-11-01

    Following large explosive volcanic eruptions precipitation decreases over much of the globe1-6, particularly in climatologically wet regions4,5. Stratospheric volcanic aerosols reflect sunlight, which reduces evaporation, whilst surface cooling stabilises the atmosphere and reduces its water-holding capacity7. Circulation changes modulate this global precipitation reduction on regional scales1,8-10. Despite the importance of rivers to people, it has been unclear whether volcanism causes detectable changes in streamflow given large natural variability. Here we analyse observational records of streamflow volume for fifty large rivers from around the world which cover between two and 6 major volcanic eruptions in the 20 th and late 19 th century. We find statistically significant reductions in flow following eruptions for the Amazon, Congo, Nile, Orange, Ob, Yenisey and Kolyma amongst others. When data from neighbouring rivers are combined - based on the areas where climate models simulate either an increase or a decrease in precipitation following eruptions - a significant (peruptions is detected in northern South American, central African and high-latitude Asian rivers, and on average across wet tropical and subtropical regions. We also detect a significant increase in southern South American and SW North American rivers. This suggests that future volcanic eruptions could substantially affect global water availability.

  11. Impact of major volcanic eruptions on stratospheric water vapour

    Directory of Open Access Journals (Sweden)

    M. Löffler

    2016-05-01

    Full Text Available Volcanic eruptions can have a significant impact on the Earth's weather and climate system. Besides the subsequent tropospheric changes, the stratosphere is also influenced by large eruptions. Here changes in stratospheric water vapour after the two major volcanic eruptions of El Chichón in Mexico in 1982 and Mount Pinatubo on the Philippines in 1991 are investigated with chemistry–climate model simulations. This study is based on two simulations with specified dynamics of the European Centre for Medium-Range Weather Forecasts Hamburg – Modular Earth Submodel System (ECHAM/MESSy Atmospheric Chemistry (EMAC model, performed within the Earth System Chemistry integrated Modelling (ESCiMo project, of which only one includes the long-wave volcanic forcing through prescribed aerosol optical properties. The results show a significant increase in stratospheric water vapour induced by the eruptions, resulting from increased heating rates and the subsequent changes in stratospheric and tropopause temperatures in the tropics. The tropical vertical advection and the South Asian summer monsoon are identified as sources for the additional water vapour in the stratosphere. Additionally, volcanic influences on tropospheric water vapour and El Niño–Southern Oscillation (ENSO are evident, if the long-wave forcing is strong enough. Our results are corroborated by additional sensitivity simulations of the Mount Pinatubo period with reduced nudging and reduced volcanic aerosol extinction.

  12. The Earth System Science Pathfinder VOLCAM Volcanic Hazard Mission

    Science.gov (United States)

    Krueger, Arlin J.

    1999-01-01

    The VOLCAM mission is planned for research on volcanic eruptions and as a demonstration of a satellite system for measuring the location and density of volcanic eruption clouds for use in mitigating hazards to aircraft by the operational air traffic control systems. A requirement for 15 minute time resolution is met by flight as payloads of opportunity on geostationary satellites. Volcanic sulfur dioxide and ash are detected using techniques that have been developed from polar orbiting TOMS (UV) and AVHRR (IR) data. Seven band UV and three band IR filter wheel cameras are designed for continuous observation of the full disk of the earth with moderate (10 - 20 km) ground resolution. This resolution can be achieved with small, low cost instruments but is adequate for discrimination of ash and sulfur dioxide in the volcanic clouds from meteorological clouds and ozone. The false alarm rate is small through use of sulfur dioxide as a unique tracer of volcanic clouds. The UV band wavelengths are optimized to detect very small sulfur dioxide amounts that are present in pre-eruptive outgassing of volcanoes. The system is also capable of tracking dust and smoke clouds, and will be used to infer winds at tropopause level from the correlation of total ozone with potential vorticity.

  13. Light-front dynamics of Chern-Simons systems

    International Nuclear Information System (INIS)

    Srivastava, P.P.

    1994-10-01

    The Chern-Simons theory coupled to complex scalars is quantized on the light-front in the local light-cone gauge by constructing the self-consistent Hamiltonian theory. It is shown that no inconsistency arises on using two local gauge-fixing conditions in the Dirac procedure. The light-front Hamiltonian turns out to be simple and the framework may be useful to construct renormalized field theory of particles with fractional statistics (anyons). The theory is shown to be relativistic and the extra term in the transformation of the matter field under space rotations, interpreted in previous works as anomaly, is argued to be gauge artefact. (author). 20 refs

  14. Reaction-diffusion fronts with inhomogeneous initial conditions

    Energy Technology Data Exchange (ETDEWEB)

    Bena, I [Departement de Physique Theorique, Universite de Geneve, CH-1211 Geneva 4 (Switzerland); Droz, M [Departement de Physique Theorique, Universite de Geneve, CH-1211 Geneva 4 (Switzerland); Martens, K [Departement de Physique Theorique, Universite de Geneve, CH-1211 Geneva 4 (Switzerland); Racz, Z [Institute for Theoretical Physics, Eoetvoes University, 1117 Budapest (Hungary)

    2007-02-14

    Properties of reaction zones resulting from A+B {yields} C type reaction-diffusion processes are investigated by analytical and numerical methods. The reagents A and B are separated initially and, in addition, there is an initial macroscopic inhomogeneity in the distribution of the B species. For simple two-dimensional geometries, exact analytical results are presented for the time evolution of the geometric shape of the front. We also show using cellular automata simulations that the fluctuations can be neglected both in the shape and in the width of the front.

  15. Front Range Forest Health Partnership Phase 1 feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    Volkin, P

    1998-09-01

    The Front Range Forest Health Partnership is an alliance of individuals, citizen groups, federal, state, private, and nonprofit organizations that formed to promote forest health restoration and reduce fire risks on Colorado's Front Range. The partnership promotes selective thinning to restore forest health and supports economically feasible end uses for wood waste materials. The Phase I study was initiated to determine the environmental and economic feasibility of using wood wastes from forested and urban areas for the production of fuel-grade ethanol.

  16. CMOS front-end electronics for radiation sensors

    CERN Document Server

    AUTHOR|(CDS)2071026

    2015-01-01

    This book offers a comprehensive treatment of front-end electronics for radiation detection. It discusses the fundamental principles of signal processing for radiation detectors and describes circuits at the level of functional building blocks, omitting transistor-level implementation. It also covers important system-level topics commonly found in the world of front-end electronics for radiation sensors. The book develops the topics in detail, with a constant focus on practical problems. It also provides real implementation examples that offer insights and stimuli for more experienced engineers already working in the field.

  17. HINS Linac front end focusing system R&D

    Energy Technology Data Exchange (ETDEWEB)

    Apollinari, G.; Carcagno, R.H.; Dimarco, J.; Huang, Y.; Kashikhin, V.V.; Orris, D.F.; Page, T.M.; Rabehl, R.; Sylvester, C.; Tartaglia, M.A.; Terechkine, I.; /Fermilab /Argonne

    2008-08-01

    This report summarizes current status of an R&D program to develop a focusing system for the front end of a superconducting RF linac. Superconducting solenoids will be used as focusing lenses in the low energy accelerating sections of the front end. The development of focusing lenses for the first accelerating section is in the production stage, and lens certification activities are in preparation at FNAL. The report contains information about the focusing lens design and performance, including solenoid, dipole corrector, and power leads, and about cryogenic system design and performance. It also describes the lens magnetic axis position measurement technique and discusses scope of an acceptance/certification process.

  18. HINS Linac front end focusing system R and D

    International Nuclear Information System (INIS)

    Apollinari, G.; Carcagno, R.H.; Dimarco, J.; Huang, Y.; Kashikhin, V.V.; Orris, D.F.; Page, T.M.; Rabehl, R.; Sylvester, C.; Tartaglia, M.A.; Terechkine, I.; Fermilab; Argonne

    2008-01-01

    This report summarizes current status of an R and D program to develop a focusing system for the front end of a superconducting RF linac. Superconducting solenoids will be used as focusing lenses in the low energy accelerating sections of the front end. The development of focusing lenses for the first accelerating section is in the production stage, and lens certification activities are in preparation at FNAL. The report contains information about the focusing lens design and performance, including solenoid, dipole corrector, and power leads, and about cryogenic system design and performance. It also describes the lens magnetic axis position measurement technique and discusses scope of an acceptance/certification process

  19. Light-front view of the axial anomaly

    International Nuclear Information System (INIS)

    Ji, C.; Rey, S.

    1996-01-01

    Motivated by an apparent puzzle of the light-front vacua incompatible with the axial anomaly, we have considered the two-dimensional massless Schwinger model for an arbitrary interpolating angle of Hornbostel close-quote s interpolating quantization surface. By examining spectral deformation of the Dirac sea under an external electric field semiclassically, we have found that the axial anomaly is quantization angle independent. This indicates an intricate nontrivial vacuum structure present even in the light-front limit. copyright 1996 The American Physical Society

  20. Differential sensor in front photopyroelectric technique: II. Experimental

    International Nuclear Information System (INIS)

    Ivanov, R; Moreno, I; Araujo-Andrade, C; MarIn, E; Cruz-Orea, A; Pichardo-Molina, J L

    2009-01-01

    We describe the differential cell design and the experimental (optical and electronic) setup for the differential front photopyroelectric technique, whose theory has been developed in the first part of this paper (Ivanov et al 2008 J. Phys. D: Appl. Phys. 41 085106). We will show first how the direct (non-differential) front photopyroelectric theory described in our previous paper reproduces well the experimental results. The usefulness of the differential technique is demonstrated by means of experimental measurements of the thermal effusivity in binary ethanol-water and glycerol-water mixtures, based on a theoretical methodology that simplifies the measurement procedure and diminishes the experimental uncertainty.

  1. Differential sensor in front photopyroelectric technique: II. Experimental

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, R; Moreno, I; Araujo-Andrade, C [Facultad de Fisica, Universidad Autonoma de Zacatecas, Calz. Solidaridad Esquina Paseo de la Bufa s/n, CP 98060, Zacatecas, Zac. (Mexico); MarIn, E [Centro de Investigacion en Ciencia Aplicada y TecnologIa Avanzada-Instituto Politecnico Nacional, Legaria 694, Col. Irrigacion, CP 11500, Mexico D.F. (Mexico); Cruz-Orea, A [Departamento de Fisica, CINVESTAV-IPN, Av. IPN No. 2508, Col. San Pedro Zacatenco, CP 07360, Mexico D.F. (Mexico); Pichardo-Molina, J L, E-mail: rumen@fisica.uaz.edu.m [Centro de Investigaciones en Optica, Loma del Bosque 115, Loma del Campestre, CP 37150, Leon, Guanajuato (Mexico)

    2009-06-21

    We describe the differential cell design and the experimental (optical and electronic) setup for the differential front photopyroelectric technique, whose theory has been developed in the first part of this paper (Ivanov et al 2008 J. Phys. D: Appl. Phys. 41 085106). We will show first how the direct (non-differential) front photopyroelectric theory described in our previous paper reproduces well the experimental results. The usefulness of the differential technique is demonstrated by means of experimental measurements of the thermal effusivity in binary ethanol-water and glycerol-water mixtures, based on a theoretical methodology that simplifies the measurement procedure and diminishes the experimental uncertainty.

  2. Rotational covariance and light-front current matrix elements

    International Nuclear Information System (INIS)

    Keister, B.D.

    1994-01-01

    Light-front current matrix elements for elastic scattering from hadrons with spin 1 or greater must satisfy a nontrivial constraint associated with the requirement of rotational covariance for the current operator. Using a model ρ meson as a prototype for hadronic quark models, this constraint and its implications are studied at both low and high momentum transfers. In the kinematic region appropriate for asymptotic QCD, helicity rules, together with the rotational covariance condition, yield an additional relation between the light-front current matrix elements

  3. Overtopping of Rubble Mound Breakwaters with Front Reservoir

    DEFF Research Database (Denmark)

    Burcharth, Hans F.; Andersen, Thomas Lykke

    2007-01-01

    The design and performance of breakwaters with front reservoir are discussed on the basis of physical 2-D model tests with a number of cross sections, in which vertopping discharge and spatial distribution, wave forces on inner parapet walls, and stability of reservoir armour were studied....... The sensitivity of these quantities to the width of the reservoir is discussed. It is demonstrated that front reservoir solutions are more economical than conventional cross section solutions, such as bermed structures and mild slope structures, in cases where low crests and small overtopping discharges...

  4. REASONING IN THE FUZZY FRONT END OF INNOVATION:

    DEFF Research Database (Denmark)

    Haase, Louise Møller; Laursen, Linda Nhu

    2018-01-01

    in the fuzzy front end is the reasoning process: innovation teams are faced with open-ended, ill-defined problems, where they need to make decisions about an unknown future but have only incomplete, ambiguous and contradicting insights available. We study the reasoning of experts, how they frame to make sense...... of all the insights and create a basis for decision-making in relation to a new project. Based on case studies of five innovative products from various industries, we propose a Product DNA model for understanding the reasoning in the fuzzy front end of innovation. The Product DNA Model explains how...... experts reason and what direct their reasoning....

  5. Observations of the Ushant tidal front in September 2007

    OpenAIRE

    Le Boyer, A.; Cambon, Gildas; Daniault, N.; Herbette, Steven; Le Cann, B.; Marie, Louis; Morin, P.

    2009-01-01

    The Ushant tidal front is the dominant feature of the summer season hydrological structure of the Iroise Sea. It separates tidally mixed coastal waters from thermally stratified open Celtic Sea waters. This article reports on observations made in September 2007 during two short cruises that took place aboard R/V "Cotes de la Manche", and gives a general account of the physical structure of the front along one cross-frontal transect. The data set comprises data from a 4 month ADCP mooring, sho...

  6. Rippled shock front solutions for testing hydrodynamic stability simulations

    International Nuclear Information System (INIS)

    Munro, D.H.

    1989-01-01

    The response of a shock front to arbitrary small perturbations can be calculated analytically. Such rippled shock front solutions are useful for determining the accuracy of hydrodynamic simulation codes such as LASNEX [Comments Plasma Phys. Controlled Fusion 2, 51 (1977)], which are used to compute perturbation growth in inertial fusion targets. The LASNEX fractional errors are of order κ 2 L 2 , where κ is the transverse wavenumber of the perturbation, and L is the largest zone dimension. Numerical errors are about 25% for a calculation using 26 zones per transverse wavelength

  7. Stability of negative ionization fronts: Regularization by electric screening?

    International Nuclear Information System (INIS)

    Arrayas, Manuel; Ebert, Ute

    2004-01-01

    We recently have proposed that a reduced interfacial model for streamer propagation is able to explain spontaneous branching. Such models require regularization. In the present paper we investigate how transversal Fourier modes of a planar ionization front are regularized by the electric screening length. For a fixed value of the electric field ahead of the front we calculate the dispersion relation numerically. These results guide the derivation of analytical asymptotes for arbitrary fields: for small wave-vector k, the growth rate s(k) grows linearly with k, for large k, it saturates at some positive plateau value. We give a physical interpretation of these results

  8. Multiple stable isotope fronts during non-isothermal fluid flow

    Science.gov (United States)

    Fekete, Szandra; Weis, Philipp; Scott, Samuel; Driesner, Thomas

    2018-02-01

    Stable isotope signatures of oxygen, hydrogen and other elements in minerals from hydrothermal veins and metasomatized host rocks are widely used to investigate fluid sources and paths. Previous theoretical studies mostly focused on analyzing stable isotope fronts developing during single-phase, isothermal fluid flow. In this study, numerical simulations were performed to assess how temperature changes, transport phenomena, kinetic vs. equilibrium isotope exchange, and isotopic source signals determine mineral oxygen isotopic compositions during fluid-rock interaction. The simulations focus on one-dimensional scenarios, with non-isothermal single- and two-phase fluid flow, and include the effects of quartz precipitation and dissolution. If isotope exchange between fluid and mineral is fast, a previously unrecognized, significant enrichment in heavy oxygen isotopes of fluids and minerals occurs at the thermal front. The maximum enrichment depends on the initial isotopic composition of fluid and mineral, the fluid-rock ratio and the maximum change in temperature, but is independent of the isotopic composition of the incoming fluid. This thermally induced isotope front propagates faster than the signal related to the initial isotopic composition of the incoming fluid, which forms a trailing front behind the zone of transient heavy oxygen isotope enrichment. Temperature-dependent kinetic rates of isotope exchange between fluid and rock strongly influence the degree of enrichment at the thermal front. In systems where initial isotope values of fluids and rocks are far from equilibrium and isotope fractionation is controlled by kinetics, the temperature increase accelerates the approach of the fluid to equilibrium conditions with the host rock. Consequently, the increase at the thermal front can be less dominant and can even generate fluid values below the initial isotopic composition of the input fluid. As kinetics limit the degree of isotope exchange, a third front may

  9. Osteoma in a blue-fronted Amazon parrot (Amazona aestiva).

    Science.gov (United States)

    Cardoso, João Felipe Rito; Levy, Marcelo Guilherme Bezerra; Liparisi, Flavia; Romão, Mario Antonio Pinto

    2013-09-01

    Osteoma is an uncommon bone formation documented in avian species and other animals. A blue-fronted Amazon parrot (Amazona aestiva) with clinical respiratory symptoms was examined because of a hard mass present on the left nostril. Radiographs suggested a bone tumor, and the mass was surgically excised. Histopathologic examination revealed features of an osteoma. To our knowledge, this is the first description of an osteoma in a blue-fronted Amazon parrot. Osteoma should be considered as a differential diagnosis in birds with respiratory distress and swelling of the nostril.

  10. General characteristics of current in front of Port Said, Egypt

    Directory of Open Access Journals (Sweden)

    Mohamed S. Elsharkawy

    2017-06-01

    Full Text Available This paper is a preliminary investigation of the general characteristics of the current in front of the coastal Mediterranean city: Port Said, Egypt. The study of the current regime in front of Port Said helps environmental engineers to tackle problems as marine port sedimentation and shoreline changes. Surface and bottom current recordings at a single offshore station of depth 104 m located at 31° 34.90′ N, 32° 30.01′ E have been subject to statistical analysis. The measurements showed unexpectedly that bottom currents were relatively stronger than surface currents during May-99.

  11. 11. El avance del Front National en Francia

    OpenAIRE

    Ferrer Sánchez, Albert

    2016-01-01

    Este artículo tiene por objeto analizar las causas del ascenso electoral de la formación ultraderechista francesa Front National (FN). En primer lugar, estudia la evolución política de dicho partido a fin de mostrar los cambios y las continuidades de su estrategia, su programa y sus discursos. Una vez analizados el contenido, la oferta política del nuevo Front National y el contexto político y social de Francia, muestra las razones por las cuales la formación ultraderechista se ha convertido ...

  12. Front-end electronics for the upgraded GMRT

    International Nuclear Information System (INIS)

    Raut, Anil N; Bhalerao, Vilas; Kumar, A Praveen

    2013-01-01

    This paper first describes briefly the existing front-end receiver in use at the GMRT observatory and then details the ongoing development of next generation receiver systems for the upgraded GMRT. It covers the design of the new, two stage, room temperature, low noise amplifiers with better noise performance and matching, and improved dynamic range that are being implemented for the 130–260 MHz, 250–500 MHz and 550–900 MHz bands of the upgraded GMRT front-end systems.

  13. Commercial helium reserves, continental rifting and volcanism

    Science.gov (United States)

    Ballentine, C. J.; Barry, P. H.; Hillegonds, D.; Fontijn, K.; Bluett, J.; Abraham-James, T.; Danabalan, D.; Gluyas, J.; Brennwald, M. S.; Pluess, B.; Seneshens, D.; Sherwood Lollar, B.

    2017-12-01

    Helium has many industrial applications, but notably provides the unique cooling medium for superconducting magnets in medical MRI scanners and high energy beam lines. In 2013 the global supply chainfailed to meet demand causing significant concern - the `Liquid Helium Crisis' [1]. The 2017 closure of Quatar borders, a major helium supplier, is likely to further disrupt helium supply, and accentuates the urgent need to diversify supply. Helium is found in very few natural gas reservoirs that have focused 4He produced by the dispersed decay (a-particle) of U and Th in the crust. We show here, using the example of the Rukwa section of the Tanzanian East African Rift, how continental rifting and local volcanism provides the combination of processes required to generate helium reserves. The ancient continental crust provides the source of 4He. Rifting and associated magmatism provides the tectonic and thermal mechanism to mobilise deep fluid circulation, focusing flow to the near surface along major basement faults. Helium-rich springs in the Tanzanian Great Rift Valley were first identified in the 1950's[2]. The isotopic compositions and major element chemistry of the gases from springs and seeps are consistent with their release from the crystalline basement during rifting [3]. Within the Rukwa Rift Valley, helium seeps occur in the vicinity of trapping structures that have the potential to store significant reserves of helium [3]. Soil gas surveys over 6 prospective trapping structures (1m depth, n=1486) show helium anomalies in 5 out of the 6 at levels similar to those observed over a known helium-rich gas reservoir at 1200m depth (7% He - Harley Dome, Utah). Detailed macroseep gas compositions collected over two days (n=17) at one site allows us to distinguish shallow gas contributions and shows the deep gas to contain between 8-10% helium, significantly increasing resource estimates based on uncorrected values (1.8-4.2%)[2,3]. The remainder of the deep gas is

  14. Study on the Effect of Straw Fiber on the Performance of Volcanic Slag Concrete

    Science.gov (United States)

    Xiao, Li-guang; Liu, Xi-xu

    2018-03-01

    In this paper, the effects of straw fiber on the working performance, mechanical properties and frost resistance of volcanic slag lightweight aggregate concrete were studied. The experimental results show that the straw fiber is subjected to surface carbonization treatment and mixed into the volcanic slag light aggregate concrete. The flexural strength and fracture pressure ratio of volcanic slag lightweight aggregate concrete are improved obviously Improved volcanic slag lightweight aggregate concrete brittleness improves toughness. Carbonized straw fiber greatly improves the frost resistance of volcanic slag lightweight aggregate concrete. So that the volcanic slag light aggregate concrete freeze-thaw cycle can reach 300 times.

  15. Volcanic tremor and local earthquakes at Copahue volcanic complex, Southern Andes, Argentina

    Science.gov (United States)

    Ibáñez, J. M.; Del Pezzo, E.; Bengoa, C.; Caselli, A.; Badi, G.; Almendros, J.

    2008-07-01

    In the present paper we describe the results of a seismic field survey carried out at Copahue Volcano, Southern Andes, Argentina, using a small-aperture, dense seismic antenna. Copahue Volcano is an active volcano that exhibited a few phreatic eruptions in the last 20 years. The aim of this experiment was to record and classify the background seismic activity of this volcanic area, and locate the sources of local earthquakes and volcanic tremor. Data consist of several volcano-tectonic (VT) earthquakes, and many samples of back-ground seismic noise. We use both ordinary spectral, and multi-spectral techniques to measure the spectral content, and an array technique [Zero Lag Cross Correlation technique] to measure the back-azimuth and apparent slowness of the signals propagating across the array. We locate VT earthquakes using a procedure based on the estimate of slowness vector components and S-P time. VT events are located mainly along the border of the Caviahue caldera lake, positioned at the South-East of Copahue volcano, in a depth interval of 1-3 km below the surface. The background noise shows the presence of many transients with high correlation among the array stations in the frequency band centered at 2.5 Hz. These transients are superimposed to an uncorrelated background seismic signal. Array solutions for these transients show a predominant slowness vector pointing to the exploited geothermal field of "Las Maquinitas" and "Copahue Village", located about 6 km north of the array site. We interpret this coherent signal as a tremor generated by the activity of the geothermal field.

  16. Volcanic Infrasound - A technical topic communicated in an entertaining way

    Science.gov (United States)

    Kerlow, Isaac

    2017-04-01

    Volcanic Infrasound is a 9-minute film about using infrasound waves to detect and measure volcanic eruptions as they unfold. The film was made by an interdisciplinary team of filmmakers and scientists for a general audience. The movie explains the basic facts of using infrasound to detect volcanic activity, and it also shows volcano researchers as they install infrasound sensors in a natural reserve in the middle of the city. This is the first in a series of films that seek to address natural hazards of relevance to Singapore, a country shielded from violent hazards. This presentation reviews the science communication techniques and assumptions used to develop and produce this entertaining scientific documentary short. Trailer: https://vimeo.com/192206460

  17. Areal and time distributions of volcanic formations on Mars

    International Nuclear Information System (INIS)

    Katterfeld, G.N.; Vityaz, V.I.

    1987-01-01

    The analysis of igneous rock distribution has been fulfilled on the basis of the geomorphological map of Mars at scale 1:5,000,000, according to data obtained from interpretation of 1:2,000,000 scale pictures of Mariner 9, Mars 4, Mars 5, Viking 1 and 2. Areological areas are listed as having been distinguished as the stratigraphic basis for a martian time scale. The area of volcanic eruptions and the number of eruptive centers are calculated on 10 x 10 deg cells and for each areological eras. The largest area of eruptive happening at different times is related with Tharsis tectonic uplift. The study of distribution of igneous rock area and volcanic centers number on 10 deg sectors and zones revealed the concentration belts of volcanic formations

  18. Areal and time distributions of volcanic formations on Mars

    Science.gov (United States)

    Katterfeld, G. N.; Vityaz, V. I.

    1987-01-01

    The analysis of igneous rock distribution has been fulfilled on the basis of the geomorphological map of Mars at scale 1:5,000,000, according to data obtained from interpretation of 1:2,000,000 scale pictures of Mariner 9, Mars 4, Mars 5, Viking 1 and 2. Areological areas are listed as having been distinguished as the stratigraphic basis for a martian time scale. The area of volcanic eruptions and the number of eruptive centers are calculated on 10 x 10 deg cells and for each areological eras. The largest area of eruptive happening at different times is related with Tharsis tectonic uplift. The study of distribution of igneous rock area and volcanic centers number on 10 deg sectors and zones revealed the concentration belts of volcanic formations.

  19. Local to global: a collaborative approach to volcanic risk assessment

    Science.gov (United States)

    Calder, Eliza; Loughlin, Sue; Barsotti, Sara; Bonadonna, Costanza; Jenkins, Susanna

    2017-04-01

    Volcanic risk assessments at all scales present challenges related to the multitude of volcanic hazards, data gaps (hazards and vulnerability in particular), model representation and resources. Volcanic hazards include lahars, pyroclastic density currents, lava flows, tephra fall, ballistics, gas dispersal and also earthquakes, debris avalanches, tsunamis and more ... they can occur in different combinations and interact in different ways throughout the unrest, eruption and post-eruption period. Volcanoes and volcanic hazards also interact with other natural hazards (e.g. intense rainfall). Currently many hazards assessments consider the hazards from a single volcano but at national to regional scales the potential impacts of multiple volcanoes over time become important. The hazards that have the greatest tendency to affect large areas up to global scale are those transported in the atmosphere: volcanic particles and gases. Volcanic ash dispersal has the greatest potential to directly or indirectly affect the largest number of people worldwide, it is currently the only volcanic hazard for which a global assessment exists. The quantitative framework used (primarily at a regional scale) considers the hazard at a given location from any volcano. Flow hazards such as lahars and floods can have devastating impacts tens of kilometres from a source volcano and lahars can be devastating decades after an eruption has ended. Quantitative assessment of impacts is increasingly undertaken after eruptions to identify thresholds for damage and reduced functionality. Some hazards such as lava flows could be considered binary (totally destructive) but others (e.g. ash fall) have varying degrees of impact. Such assessments are needed to enhance available impact and vulnerability data. Currently, most studies focus on physical vulnerability but there is a growing emphasis on social vulnerability showing that it is highly variable and dynamic with pre-eruption socio

  20. Ejection age of volcano rocks and trend of volcanic activity

    Energy Technology Data Exchange (ETDEWEB)

    Sakaguchi, Keiichi

    1987-10-01

    This report is II-7 of an interim report on research and development of the Sunshine Project for 1986. This report considers on the trend of volcanic activities in the South of Kyushu area. K-Ar age measurement was newly made and reported. Age values obtained were 1.09 plus minus 0.21 Ma for Nagaoyama andesite, 1.33 plus minus 0.18 Ma for Nozato andesite, and 0.3 plus minus 0.1 Ma for Imuta volcanos. Including these age values, from the age values and their distribution of the volcanic rocks in the South Kyushu district, the following three districts were selected to represent the volcanic activities since the Pliocene Epoch. As these districts are mutually overwrapped, verification at these overwrapped districts are necessary. (4 figs, 1 tab, 12 refs)

  1. How Did Climate and Humans Respond to Past Volcanic Eruptions?

    Science.gov (United States)

    Toohey, Matthew; Ludlow, Francis; Legrande, Allegra N.

    2016-01-01

    To predict and prepare for future climate change, scientists are striving to understand how global-scale climatic change manifests itself on regional scales and also how societies adapt or don't to sometimes subtle and complex climatic changes. In this regard, the strongest volcanic eruptions of the past are powerful test cases, showcasing how the broad climate system responds to sudden changes in radiative forcing and how societies have responded to the resulting climatic shocks. These issues were at the heart of the inaugural workshop of the Volcanic Impacts on Climate and Society (VICS) Working Group, convened in June 2016 at the Lamont-Doherty Earth Observatory of Columbia University in Palisades, N.Y. The 3-day meeting gathered approximately 50 researchers, who presented work intertwining the history of volcanic eruptions and the physical processes that connect eruptions with human and natural systems on a global scale.

  2. Smelters as Analogs for a Volcanic Eruption at Yucca Mountain

    International Nuclear Information System (INIS)

    Ross, Benjamin

    2004-01-01

    The distribution of trace radionuclides in secondary metal smelters provides an analog for spent fuel released from packages during a volcanic eruption. The fraction of the inventory of a radionuclide that would be released into the air in a volcanic eruption is called the dust partitioning factor. In consequence analyses of a volcanic eruption at Yucca Mountain, a value of one has been used for this parameter for all elements. This value is too high for the refractory elements. Reducing the dust partitioning factor for refractory elements to a value equal to the fraction of the magma that becomes ash would still yield conservative estimates of how much radioactivity would be released in an eruption

  3. Was there a volcanic eruption off Vietnam in AD 608?

    Science.gov (United States)

    Khoo, T. T.

    In the Sui-shu (Annals of the Sui Dynasty, 581-618), there is a record that returning envoys of the Chinese court to a state in northeastern Malay peninsula had in April-June AD 608 reached the state of Lin-i where for a whole day's sail the air around the vessel was yellowish and fetid. Lin-i was located at the southern end of the Annam Highlands chain and it is interpreted here that the phenominon reported could be due to a volcanic eruption in the Poulo Cecir-Ile des Cendres-Veteran volcanic islands group near the area. During the months of May to June the winds of the southwest monsoon, too, blow from the volcanic area toward the southern end of the Annam Highlands.

  4. Using Digital Cameras to Detect Warning Signs of Volcanic Eruptions

    Science.gov (United States)

    Girona, T.; Huber, C.; Trinh, K. T.; Protti, M.; Pacheco, J. F.

    2017-12-01

    Monitoring volcanic outgassing is fundamental to improve the forecasting of volcanic eruptions. Recent efforts have led to the advent of new methods to measure the concentration and flux of volcanic gases with unprecedented temporal resolution, thus allowing us to obtain reliable high-frequency (up to 1 Hz) time series of outgassing activity. These high-frequency methods have shown that volcanic outgassing can be periodic sometimes (with periodicities ranging from 101 s to 103 s), although it remains unknown whether the spectral features of outgassing reflect the processes that ultimately trigger volcanic unrest and eruptions. In this study, we explore the evolution of the spectral content of the outgassing activity of Turrialba volcano (Costa Rica) using digital images (with digital brightness as a proxy for the emissions of water vapor [Girona et al., 2015]). Images were taken at 1 km distance with 1 Hz sampling rate, and the time period analyzed (from April 2016 to April 2017) is characterized by episodes of quiescent outgassing, ash explosions, and sporadic eruptions of ballistics. Our preliminary results show that: 1) quiescent states of Turrialba volcano are characterized by outgassing frequency spectra with fractal distribution; 2) superimposed onto the fractal frequency spectra, well-defined pulses with period around 100 s emerge hours to days before some of the eruptions of ballistics. An important conclusion of this study is that digital cameras can be potentially used in real-time volcano monitoring to detect warning signs of eruptions, as well as to better understand subsurface processes and track the changing conditions below volcanic craters. Our ongoing study also explores the correlation between the evolution of the spectral content of outgassing, infrasound data, and shallow seismicity. Girona, T., F. Costa, B. Taisne, B. Aggangan, and S. Ildefonso (2015), Fractal degassing from Erebus and Mayon volcanoes revealed by a new method to monitor H2O

  5. Effects of volcanic deposit disaggregation on exposed water composition

    Science.gov (United States)

    Back, W. E.; Genareau, K. D.

    2016-12-01

    Explosive volcanic eruptions produce a variety of hazards. Pyroclastic material can be introduced to water through ash fallout, pyroclastic flows entering water bodies, and/or lahars. Remobilization of tephras can occur soon after eruption or centuries later, introducing additional pyroclastic material into the environment. Introduction of pyroclastic material may alter the dissolved element concentration and pH of exposed waters, potentially impacting drinking water supplies, agriculture, and ecology. This study focuses on the long-term impacts of volcanic deposits on water composition due to the mechanical breakup of volcanic deposits over time. Preliminary work has shown that mechanical milling of volcanic deposits will cause significant increases in dissolved element concentrations, conductivity, and pH of aqueous solutions. Pyroclastic material from seven eruptions sites was collected, mechanically milled to produce grain sizes Soufriere Hills, Ruapehu), mafic (Lathrop Wells) and ultramafic (mantle xenoliths) volcanic deposits. Lathrop Wells has an average bulk concentration of 49.15 wt.% SiO2, 6.11 wt. % MgO, and 8.39 wt. % CaO and produces leachate concentrations of 85.69 mg/kg for Ca and 37.22 mg/kg for Mg. Taupo and Valles Caldera samples have a bulk concentration of 72.9 wt.% SiO2, 0.59 wt. % MgO, and 1.48 wt. % CaO, and produces leachate concentrations of 4.08 mg/kg for Ca and 1.56 mg/kg for Mg. Similar testing will be conducted on the intermediate and ultramafic samples to test the hypothesis that bulk magma composition and mineralogy will directly relate to the increased dissolved element concentration of exposed waters. The measured effects on aqueous solutions will aid in evaluation of impacts to marine and freshwater systems exposed to volcanic deposits.

  6. Lichen Persistence and Recovery in Response to Varied Volcanic Disturbances

    Science.gov (United States)

    Nelson, P.; Wheeler, T. B.

    2015-12-01

    Volcanic eruptions produce many ecological disturbances that structure vegetation. While lichens are sensitive to disturbances, little is known about their responses to volcanic disturbances, except for colonization of lava. We examined lichen community responses through time to different disturbances produced by the May 1, 2008 eruption of Volcan Chaiten in south-central Chile. Pre-eruption vegetation near the volcano was old-growth Valdivian temperate rainforest dominated by closed-canopy Nothofagus sp... In 2012, we installed thirteen 1-acre plots across volcanic disturbance zones on which a time-constrained search was done for all macrolichen species, each of which was assigned an approximate log10 categorical abundance. We also installed a 0.2 m2 quadrat on two representative trees per plot for repeat photography of lichen cover. We remeasured at least one plot per disturbance zone in 2014 and re-photographed tree quadrats in 2013 and 2014. We then analyzed species composition and abundance differences among disturbance zones. In 2012, the blast (pyroclastic density flow), scorch (standing scorched forest at the edge of the blast) and deep tephra (>10 cm) zones had the lowest lichen species richness (5-13 species), followed by reference (unimpacted) and shallow (lichen species since 2012 while the light tephra and reference were essentially unchanged. Gravel rain, gravel rain + pumice and flooded forest plots all had about the same number of species in 2014 as 2012. Lichen colonization and growth in tree quadrats varied widely, from very little colonization in the blast to prolific colonization in the gravel rain + pumice zone. Lichen's varied responses to different volcanic disturbances were attributable to varying degrees of mortality and subsequent availability of substrate, quantity of light and removal of competitors. While sensitive to disturbance, lichens are apparently resilient to and can quickly recolonize after a variety of large, violent volcanic

  7. Evidence for volcanism in NW Ishtar Terra, Venus

    International Nuclear Information System (INIS)

    Gaddis, L.; Greeley, R.

    1989-01-01

    Venera 15/16 radar data for an area in NW Ishtar Terra, Venus, show an area with moderate radar return and a smooth textured surface which embays low lying areas of the surrounding mountainous terrain. Although this unit may be an extension of the lava plains of Lakshmi Planum to the southeast, detailed study suggests a separate volcanic center in NW Ishtar Terra. Lakshmi Planum, on the Ishtar Terra highland, exhibits major volcanic and tectonic features. On the Venera radar image radar brightness is influenced by slope and roughness; radar-facing slopes (east-facing) and rough surfaces (approx. 8 cm average relief) are bright, while west-facing slopes and smooth surfaces are dark. A series of semi-circular features, apparently topographic depressions, do not conform in orientation to major structural trends in this region of NW Ishtar Terra. The large depression in NW Ishtar Terra is similar to the calderas of Colette and Sacajawea Paterae, as all three structures are large irregular depressions. NW Ishtar Terra appears to be the site of a volcanic center with a complex caldera structure, possibly more than one eruptive vent, and associated lobed flows at lower elevations. The morphologic similarity between this volcanic center and those of Colette and Sacajawea suggests that centralized eruptions have been the dominant form of volcanism in Ishtar. The location of this volcanic center at the intersection of two major compressional mountain belts and the large size of the calders (with an inferred larg/deep magma source) support a crustal thickening/melting rather than a hot-spot origin for these magmas

  8. PACE3 - front-end chip for the CMS Preshower

    CERN Multimedia

    Aspel, Paul

    2003-01-01

    This is PACE3 which is the front-end chip for the CMS Preshower. In fact PACE3 is the combination of two ASICs called Delta3 and PACEAM3. Delta3 is on the left and PACEAM3 is on the right. The two ASICs are bonded together and then packaged within a single 196 pin fpBGA package.

  9. Iterative wave-front reconstruction in the Fourier domain.

    Science.gov (United States)

    Bond, Charlotte Z; Correia, Carlos M; Sauvage, Jean-François; Neichel, Benoit; Fusco, Thierry

    2017-05-15

    The use of Fourier methods in wave-front reconstruction can significantly reduce the computation time for large telescopes with a high number of degrees of freedom. However, Fourier algorithms for discrete data require a rectangular data set which conform to specific boundary requirements, whereas wave-front sensor data is typically defined over a circular domain (the telescope pupil). Here we present an iterative Gerchberg routine modified for the purposes of discrete wave-front reconstruction which adapts the measurement data (wave-front sensor slopes) for Fourier analysis, fulfilling the requirements of the fast Fourier transform (FFT) and providing accurate reconstruction. The routine is used in the adaptation step only and can be coupled to any other Wiener-like or least-squares method. We compare simulations using this method with previous Fourier methods and show an increase in performance in terms of Strehl ratio and a reduction in noise propagation for a 40×40 SPHERE-like adaptive optics system. For closed loop operation with minimal iterations the Gerchberg method provides an improvement in Strehl, from 95.4% to 96.9% in K-band. This corresponds to ~ 40 nm improvement in rms, and avoids the high spatial frequency errors present in other methods, providing an increase in contrast towards the edge of the correctable band.

  10. Radiation hydrodynamical instabilities in cosmological and galactic ionization fronts

    Science.gov (United States)

    Whalen, Daniel J.; Norman, Michael L.

    2011-11-01

    Ionization fronts, the sharp radiation fronts behind which H/He ionizing photons from massive stars and galaxies propagate through space, were ubiquitous in the universe from its earliest times. The cosmic dark ages ended with the formation of the first primeval stars and galaxies a few hundred Myr after the Big Bang. Numerical simulations suggest that stars in this era were very massive, 25-500 solar masses, with H(II) regions of up to 30,000 light-years in diameter. We present three-dimensional radiation hydrodynamical calculations that reveal that the I-fronts of the first stars and galaxies were prone to violent instabilities, enhancing the escape of UV photons into the early intergalactic medium (IGM) and forming clumpy media in which supernovae later exploded. The enrichment of such clumps with metals by the first supernovae may have led to the prompt formation of a second generation of low-mass stars, profoundly transforming the nature of the first protogalaxies. Cosmological radiation hydrodynamics is unique because ionizing photons coupled strongly to both gas flows and primordial chemistry at early epochs, introducing a hierarchy of disparate characteristic timescales whose relative magnitudes can vary greatly throughout a given calculation. We describe the adaptive multistep integration scheme we have developed for the self-consistent transport of both cosmological and galactic ionization fronts.

  11. Analytical Estimates of the Dispersion Curve in Planar Ionization Fronts

    International Nuclear Information System (INIS)

    Arrayas, Manuel; Trueba, Jose L.; Betelu, Santiago; Fontelos, Marco A.

    2009-01-01

    Fingers from ionization fronts for a hydrodynamic plasma model result from a balance between impact ionization and electron diffusion in a non-attaching gas. An analytical estimation of the size of the fingers and its dependence on both the electric field and electron diffusion coefficient can be done when the diffusion is low and the electric field is strong.

  12. Vacuum Polarization Tensor for QED in the Light Front Gauge

    International Nuclear Information System (INIS)

    Suzuki, A.T.; Soriano, L.A.; Bolzan, J.D.; Sales, J.H.O.

    2012-01-01

    The use of light front coordinates in quantum field theories (QFT) always brought some problems and controversies. In this work we explore some aspects of its formalism with respect to the employment of dimensional regularization in the computation of the photon's self-energy at the one-loop level and how the fermion propagator has an important role in the outcoming results. (author)

  13. On the propagation of a coupled saturation and pressure front

    Energy Technology Data Exchange (ETDEWEB)

    Vasco, D. W.

    2010-12-01

    Using an asymptotic technique, valid for a medium with smoothly varying heterogeneity, I derive an expression for the velocity of a propagating, coupled saturation and pressure front. Due to the nonlinearity of the governing equations, the velocity of the propagating front depends upon the magnitude of the saturation and pressure changes across the front in addition to the properties of the medium. Thus, the expression must be evaluated in conjunction with numerical reservoir simulation. The propagation of the two-phase front is governed by the background saturation distribution, the saturation-dependent component of the fluid mobility, the porosity, the permeability, the capillary pressure function, the medium compressibility, and the ratio of the slopes of the relative permeability curves. Numerical simulation of water injection into a porous layer saturated with a nonaqueous phase liquid indicates that two modes of propagation are important. The fastest mode of propagation is a pressure-dominated disturbance that travels through the saturated layer. This is followed, much later, by a coupled mode with a large saturation change. These two modes are also observed in a simulation using a heterogeneous porous layer. A comparison between the propagation times estimated from the results of the numerical simulation and predictions from the asymptotic expression indicates overall agreement.

  14. Front end readout electronics for the CMS hadron calorimeter

    CERN Document Server

    Shaw, Terri M

    2002-01-01

    The front-end electronics for the CMS Hadron Calorimeter provides digitized data at the beam interaction rate of 40 MHz. Analog signals provided by hybrid photodiodes (HPDs) or photomultiplier tubes (PMTs) are digitized and the data is sent off board through serialized fiber optic links running at 1600 Mbps. In order to maximize the input signal, the front-end electronics are housed on the detector in close proximity to the scintillating fibers or phototubes. To fit the electronics into available space, custom crates, backplanes and cooling methods have had to be developed. During the expected ten-year lifetime, the front-end readout electronics will exist in an environment where radiation levels approach 330 rads and the neutron fluence will be 1.3E11 n/cm sup 2. For this reason, the design approach relies heavily upon custom radiation tolerant ASICs. This paper will present the system architecture of the front-end readout crates and describe their results with early prototypes.

  15. Front End Loader Operator. Open Pit Mining Job Training Series.

    Science.gov (United States)

    Savilow, Bill

    This training outline for front end loader operators, one in a series of eight outlines, is designed primarily for company training foremen or supervisors and for trainers to use as an industry-wide guideline for heavy equipment operator training in open pit mining in British Columbia. Intended as a guide for preparation of lesson plans both for…

  16. Front-running of Mutual Fund Fire-sales

    NARCIS (Netherlands)

    Dyakov, T.C.; Verbeek, M.

    2013-01-01

    We show that a real-time trading strategy which front-runs the anticipated forced sales by mutual funds experiencing extreme capital outflows generates an alpha of 0.5% per month during the 1990-2010 period. The abnormal return stems from selling pressure among stocks that are below the NYSE mean

  17. Consumer preferences for front-of-pack calories labelling

    NARCIS (Netherlands)

    Kleef, van E.; Trijp, van J.C.M.; Paeps, F.; Fernández-Celemín, L.

    2008-01-01

    Objective In light of the emerging obesity pandemic, front-of-pack calories labels may be an important tool to assist consumers in making informed healthier food choices. However, there is little prior research to guide key decisions on whether caloric content should be expressed in absolute terms

  18. An operational map of the Polish Coastal Front 1970

    DEFF Research Database (Denmark)

    Nielsen, Thomas Theis; Svenningsen, Stig Roar; Tinning, Morten

    2016-01-01

    The map of the Operational Plan for the Coastal Front, from Poland 1970 forms the basis for this paper. The map portraits the blueprint of the combined operational war plans for the Polish military in the late 1960’s and 70’s. It details the offensive against NATO countries and their forces...

  19. A New Formula for Front Slope Recession of Berm Breakwaters

    DEFF Research Database (Denmark)

    Andersen, Thomas Lykke; Burcharth, Hans F.

    2010-01-01

    The front slope stability of breakwaters with a homogeneous berm was studied in a large number of two dimensional model tests at Aalborg University, Denmark. The results are presented together with a new formula for prediction of the berm recession which is the most important parameter...

  20. Propagating fronts in reaction-transport systems with memory

    Energy Technology Data Exchange (ETDEWEB)

    Yadav, A. [Department of Chemistry, Southern Methodist University, Dallas, TX 75275-0314 (United States)], E-mail: ayadav1@lsu.edu; Fedotov, Sergei [School of Mathematics, University of Manchester, Manchester M60 1DQ (United Kingdom)], E-mail: sergei.fedotov@manchester.ac.uk; Mendez, Vicenc [Grup de Fisica Estadistica, Departament de Fisica, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain)], E-mail: vicenc.mendez@uab.es; Horsthemke, Werner [Department of Chemistry, Southern Methodist University, Dallas, TX 75275-0314 (United States)], E-mail: whorsthe@smu.edu

    2007-11-26

    In reaction-transport systems with non-standard diffusion, the memory of the transport causes a coupling of reactions and transport. We investigate the effect of this coupling for systems with Fisher-type kinetics and obtain a general analytical expression for the front speed. We apply our results to the specific case of subdiffusion.

  1. Front and backside processed thin film electronic devices

    Science.gov (United States)

    Yuan, Hao-Chih; Wang, Guogong; Eriksson, Mark A.; Evans, Paul G.; Lagally, Max G.; Ma, Zhenqiang

    2010-10-12

    This invention provides methods for fabricating thin film electronic devices with both front- and backside processing capabilities. Using these methods, high temperature processing steps may be carried out during both frontside and backside processing. The methods are well-suited for fabricating back-gate and double-gate field effect transistors, double-sided bipolar transistors and 3D integrated circuits.

  2. Variational formulation based analysis on growth of yield front in ...

    African Journals Online (AJOL)

    The present study investigates the growth of elastic-plastic front in rotating solid disks of non-uniform thickness having exponential and parabolic geometry variation. The problem is solved through an extension of a variational method in elastoplastic regime. The formulation is based on von-Mises yield criterion and linear ...

  3. Electric field measurements in moving ionization fronts during plasma breakdown

    NARCIS (Netherlands)

    Wagenaars, E.; Bowden, M.D.; Kroesen, G.M.W.

    2006-01-01

    We have performed time-resolved, direct measurements of electric field strengths in moving ionization fronts during the breakdown phase of a pulsed plasma. Plasma breakdown, or plasma ignition, is a highly transient process marking the transition from a gas to a plasma. Some aspects of plasma

  4. Morale among French colonial troops on the Western Front during ...

    African Journals Online (AJOL)

    The traditional images of the French Army in World War I on the Western Front from Cyril Falls's to Marc Ferro's surveys (both entitled The Great War 1914– 1918) have been that of the grizzled yet determined French peasant or worker – the poilu. It is clear from recent research that this is far from accurate and that the French ...

  5. Front end readout electronics for the CMS hadron calorimeter

    International Nuclear Information System (INIS)

    Terri M. Shaw et al.

    2002-01-01

    The front-end electronics for the CMS Hadron Calorimeter provides digitized data at the beam interaction rate of 40 MHz. Analog signals provided by hybrid photodiodes (HPDs) or photomultiplier tubes (PMTs) are digitized and the data is sent off board through serialized fiber optic links running at 1600 Mbps. In order to maximize the input signal, the front-end electronics are housed on the detector in close proximity to the scintillating fibers or phototubes. To fit the electronics into available space, custom crates, backplanes and cooling methods have had to be developed. During the expected ten-year lifetime, the front-end readout electronics will exist in an environment where radiation levels approach 330 rads and the neutron fluence will be 1.3E11 n/cm 2 . For this reason, the design approach relies heavily upon custom radiation tolerant ASICs. This paper will present the system architecture of the front-end readout crates and describe their results with early prototypes

  6. Calibration method for direct conversion receiver front-ends

    Directory of Open Access Journals (Sweden)

    R. Müller

    2008-05-01

    Full Text Available Technology induced process tolerances in analog circuits cause device characteristics different from specification. For direct conversion receiver front-ends a system level calibration method is presented. The malfunctions of the devices are compensated by tuning dominant circuit parameters. Thereto optimization techniques are applied which use measurement values and special evaluation functions.

  7. Modeling beam-front dynamics at low gas pressures

    International Nuclear Information System (INIS)

    Briggs, R.J.; Yu, S.

    1982-01-01

    The dynamics of space charge neutralization at the front of an intense self-focused electron beam pulse exhibits important differences in different gas pressure regimes. At very low pressures, the beam front is in the so-called ion-focused regime (IFR) where all secondary electrons are expelled from the beam region by the radial electric field without causing significant additional ionization. We estimate the upper pressure boundary of this regime by considering the distance scale length for cascade (avalanche) ionization. Data from the FX-25 diode experiments indicate a critical transition pressure (P/sub c/) that agrees with this estimate and with its scaling among various gas types. Normal mobility-limited treatments (local conductivity models) of the secondary electrons at the beam front are not justified until the gas pressure is 10 to 50 times higher than P/sub c/, due to runaway of these secondary electrons in the strong space-charge electric field at the lower pressures. The main conclusion of this study is that a non-local phase space (Boltzmann) treatment of the secondary electrons is required to accurately describe these different beam front regimes and the transitions between them; such a code model is currently under development

  8. A socio-internactive framework for the fuzzy front end

    NARCIS (Netherlands)

    Smulders, Frido E.; van den Broek, Egon; van der Voort, Mascha C.; Fernandes, A.; Teixeira, A.; Natal Jorge, R.

    2007-01-01

    This paper aims to illustrate that the dominating rational-analytic perspective on the Fuzzy Front End (FFE) of innovation could benefit by a complementary socio-interactive perspective that addresses the social processes during the FFE. We have developed a still fledgling socio-interactive

  9. Protecting front-line survey and rescue teams during emergencies

    International Nuclear Information System (INIS)

    Tresise, H.

    1980-01-01

    Means of protecting front-line survey and rescue teams during emergencies are described. The team composition, their apparatus, the selection of the incident control point, the use of guidelines and breathing apparatus and control point trolley and equipment are discussed. (H.K.)

  10. Sulfate Formation on Mars by Volcanic Aerosols: A New Look

    Science.gov (United States)

    Blaney, D. L.

    1996-03-01

    Sulfur was measured at both Viking Lander sites in abundances of 5-9 wt % SO3. Because the sulfur was more concentrated in clumps which disintegrated and the general oxidized nature of the Martian soil, these measurements led to the assumption that a sulfate duricrust existed. Two types of models for sulfate formation have been proposed. One is a formation by upwardly migrating ground water. The other is the formation of sulfates by the precipitation of volcanic aerosols. Most investigators have tended to favor the ground water origin of sulfates on Mars. However, evidence assemble since Viking may point to a volcanic aerosol origin.

  11. Treatment of low-level radioactive waste using Volcanic ash

    International Nuclear Information System (INIS)

    Valdezco, E.M.; Marcelo, E.A.; Junio, J.B.; Caseria, E.S.; Salom, D.S.; Alamares, A.L.

    1997-01-01

    The effective application of volcanic ash, an indigenous adsorptive material abundant in the Mt. Pinatubo area, in the removal of radioiodine from radioactive waste streams was demonstrated. Factors such as availability, low cost and comparative retention capacity with respect to activated charcoal make volcanic ash an attractive alternative in the conditioning of radioactive waste containing radioiodine. Chemical precipitation was employed in the treatment of low level aqueous waste containing 137 Cs. It was shown that there exists an optimum concentration of ferric ion that promotes maximum precipitation of caesium. It was further demonstrated that complete removal of caesium can be achieved with the addition of nickel hexacyanoferrate. (author). 5 refs, 3 figs

  12. Self-potential anomalies preceding tectonic and volcanic crises

    International Nuclear Information System (INIS)

    Patella, D.

    1993-01-01

    In this paper I consider a possible physical mechanism capable of explaining self-potential anomalies, which are currently observed on the ground surface prior to tectonic and volcanic activities. A rock cracking-fluid diffusion-charge polarization model is described. The electrical charge polarization is assumed to be the electrokinetic effect due to invasion of fluid into new fissures, which open inside a stressed rock material because of dilatancy, in the case of tectonic activity, and of the rising of a magma intrusion in the case of volcanic activity. (author). 10 refs, 2 figs

  13. Treatment of low-level radioactive waste using Volcanic ash

    Energy Technology Data Exchange (ETDEWEB)

    Valdezco, E M; Marcelo, E A; Junio, J B; Caseria, E S; Salom, D S; Alamares, A L [Philippine Nuclear Research Inst., Manila (Philippines). Radiation Protection Services

    1997-02-01

    The effective application of volcanic ash, an indigenous adsorptive material abundant in the Mt. Pinatubo area, in the removal of radioiodine from radioactive waste streams was demonstrated. Factors such as availability, low cost and comparative retention capacity with respect to activated charcoal make volcanic ash an attractive alternative in the conditioning of radioactive waste containing radioiodine. Chemical precipitation was employed in the treatment of low level aqueous waste containing {sup 137}Cs. It was shown that there exists an optimum concentration of ferric ion that promotes maximum precipitation of caesium. It was further demonstrated that complete removal of caesium can be achieved with the addition of nickel hexacyanoferrate. (author). 5 refs, 3 figs.

  14. Evaluation of added phosphorus in six volcanic ash soils

    International Nuclear Information System (INIS)

    Pino N, I.; Casas G, L.; Urbinsa P, M.C.

    1984-01-01

    The behaviour of added phosphorus in six volcanic ash soils (Andepts) was studied. Two phosphate retention solution were used; one of them labeled with 32 P carrier free. The phosphate retention solution (25 ml) was added to 5 gr of air dry soil. The remainder phosphorus in solution was measured through colorimetry and liquid scintillation. Over 85% phosphorus retention was measured in five soils. A phosphate retention solution labeled with 32 P carrier free proved to be efficient for the determination of phosphorus retention rates in the volcanic ash soils studied. (Author)

  15. STABILIZATION OF GRANULAR VOLCANIC ASH IN SANA'A AREA

    Directory of Open Access Journals (Sweden)

    SUBHI A. ALI

    2014-02-01

    Full Text Available This paper presents the findings of compaction and strength characteristics of a Granular Volcanic Ash from Sana'a city center, which was mixed with various percentages of two binders to form a stabilized material namely; fine soil and Portland cement. The study showed a significant improvement of the Volcanic Ash properties. The maximum dry density and California bearing ration (CBR were considerably increased by addition of stabilizers at different rates for different binder contents. Optimum fine soil content for the maximum dry density and CBR is determined. A relationship between the optimum moisture content and the binder combination content for different fine soil percentages was established.

  16. Revised paleomagnetic pole for the Sonoma Volcanics, California

    Science.gov (United States)

    Mankinen, E.A.

    1989-01-01

    Paleomagnetic sampling of the Miocene and Pliocene Sonoma Volcanics, northern California, was undertaken to supplement an earlier collection. Data from 25 cooling units yield positive fold and reversal tests, and a paleomagnetic pole located at 80.2??N., 069.2??E., with ??95 = 6.8??. This paleopole is significantly displaced (9.6?? ?? 5.3?? of latitude) to the farside of the geographic pole. A highly elliptical distribution of the data in both direction and VGP space indicates that incomplete averaging of geomagnetic secular variation is a more likely explanation for this anomaly than is northward translation of the volcanic field. -Author

  17. Characterization of the volcanic eruption emissions using neutron activation analysis

    International Nuclear Information System (INIS)

    Pla, Rita R.; Tafuri, Victoria V.

    1997-01-01

    Characterization of the volcanic particulate material has been performed by analyzing aerosols and ashes with instrumental neutron activation analysis. Crustal enrichment factors were calculated using the elemental concentration and clustering techniques, and multivariate analysis were done. The analytical and data treatment methodologies allowed the sample differentiation from their geographical origin viewpoint, based on their chemical composition patterns, which are related to the deposit formation processes, which consist of direct deposition from the volcanic cloud, and removal by wind action after the end of the eruption, and and finally the deposition. (author). 8 refs., 5 figs

  18. Role of volcanic forcing on future global carbon cycle

    Directory of Open Access Journals (Sweden)

    J. F. Tjiputra

    2011-06-01

    Full Text Available Using a fully coupled global climate-carbon cycle model, we assess the potential role of volcanic eruptions on future projection of climate change and its associated carbon cycle feedback. The volcanic-like forcings are applied together with a business-as-usual IPCC-A2 carbon emissions scenario. We show that very large volcanic eruptions similar to Tambora lead to short-term substantial global cooling. However, over a long period, smaller eruptions similar to Pinatubo in amplitude, but set to occur frequently, would have a stronger impact on future climate change. In a scenario where the volcanic external forcings are prescribed with a five-year frequency, the induced cooling immediately lower the global temperature by more than one degree before it returns to the warming trend. Therefore, the climate change is approximately delayed by several decades, and by the end of the 21st century, the warming is still below two degrees when compared to the present day period. Our climate-carbon feedback analysis shows that future volcanic eruptions induce positive feedbacks (i.e., more carbon sink on both the terrestrial and oceanic carbon cycle. The feedback signal on the ocean is consistently smaller than the terrestrial counterpart and the feedback strength is proportionally related to the frequency of the volcanic eruption events. The cooler climate reduces the terrestrial heterotrophic respiration in the northern high latitude and increases net primary production in the tropics, which contributes to more than 45 % increase in accumulated carbon uptake over land. The increased solubility of CO2 gas in seawater associated with cooler SST is offset by a reduced CO2 partial pressure gradient between the ocean and the atmosphere, which results in small changes in net ocean carbon uptake. Similarly, there is nearly no change in the seawater buffer capacity simulated between the different volcanic scenarios. Our study shows that even

  19. Radon in active volcanic areas of Southern Italy

    International Nuclear Information System (INIS)

    Avino, R.; Capaldi, G.; Pece, R.

    1999-01-01

    The paper presents the preliminary data dealing with the variations in time of the radiogenic gas radon in soils and waters of many active volcanic areas of Southern Italy. The greatest differences in Rn content of the investigated volcanic areas are: Ischia and Campi Flegrei, which have more Rn than Vesuvio and Volcano, both in soils and in waters. The thermalized waters of Ischia are enriched in Rn 15 times with respect to soils, while in the other areas soils and underground waters have comparable Rn contents

  20. 5-D interpolation with wave-front attributes

    Science.gov (United States)

    Xie, Yujiang; Gajewski, Dirk

    2017-11-01

    Most 5-D interpolation and regularization techniques reconstruct the missing data in the frequency domain by using mathematical transforms. An alternative type of interpolation methods uses wave-front attributes, that is, quantities with a specific physical meaning like the angle of emergence and wave-front curvatures. In these attributes structural information of subsurface features like dip and strike of a reflector are included. These wave-front attributes work on 5-D data space (e.g. common-midpoint coordinates in x and y, offset, azimuth and time), leading to a 5-D interpolation technique. Since the process is based on stacking next to the interpolation a pre-stack data enhancement is achieved, improving the signal-to-noise ratio (S/N) of interpolated and recorded traces. The wave-front attributes are determined in a data-driven fashion, for example, with the Common Reflection Surface (CRS method). As one of the wave-front-attribute-based interpolation techniques, the 3-D partial CRS method was proposed to enhance the quality of 3-D pre-stack data with low S/N. In the past work on 3-D partial stacks, two potential problems were still unsolved. For high-quality wave-front attributes, we suggest a global optimization strategy instead of the so far used pragmatic search approach. In previous works, the interpolation of 3-D data was performed along a specific azimuth which is acceptable for narrow azimuth acquisition but does not exploit the potential of wide-, rich- or full-azimuth acquisitions. The conventional 3-D partial CRS method is improved in this work and we call it as a wave-front-attribute-based 5-D interpolation (5-D WABI) as the two problems mentioned above are addressed. Data examples demonstrate the improved performance by the 5-D WABI method when compared with the conventional 3-D partial CRS approach. A comparison of the rank-reduction-based 5-D seismic interpolation technique with the proposed 5-D WABI method is given. The comparison reveals that