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Sample records for hardened volcanic soils

  1. Soil properties controlling infiltration in volcanic soils

    NASA Astrophysics Data System (ADS)

    Neris, Jonay; Tejedor, Marisa; Jiménez, Concepción

    2013-04-01

    Soil water infiltration is an important process whose behaviour depends on external factors and soil properties that vary depending on the type of soil. The soil parameters affecting the infiltration capacity of six soil orders all formed on volcanic materials (andisols, vertisols, alfisols, aridisols, inceptisols, and entisols) and contribute to the differences between them were studied in this paper. A total of 108 sites were selected on the island of Tenerife (Spain). The main soil properties were analysed and the steady-state infiltration rate measured using a double-ring infiltrometer. The relationship between the soil properties and infiltration was modelled using statistical Principal Components Analysis and regressions. The research concludes that the relation between structural development and texture play a decisive role. The high structural development of non-vitric andisols, due to the high organic matter and short-range-order mineral content, leads to an extremely fast infiltration rate. The structural instability and fine texture of aridisols produce low infiltration. In less developed soils (entisols and vitric andisols) where aggregate formation is minimal or non-existent, the coarse grain size is the relevant factor determining their very fast and extremely fast infiltration. In vertisols and alfisols, which have strong aggregation but low stability, clay type and content play an important role and lead to a moderate and moderately fast steady-state infiltration rate, respectively. In the most typic inceptisols, with moderate structural development and stability, the balance of the properties is largely responsible for the intermediate infiltration rate observed.

  2. Non-volcanic andic soils - a new soil type?

    NASA Astrophysics Data System (ADS)

    Bäumler, Rupert

    2014-05-01

    Numerous sites are described all over the world with soils fulfilling all requirements of andic soil properties developed in non-volcanic and non-allophanic parent materials, and in different bioclimatic zones. Up to now these soils are mainly assigned to Andisols/Andosols or andic Inceptisols in WRB and US Soil Taxonomy. Common factors and properties of this group of soils are in general acid parent materials, advanced soil development, comparably high amounts of oxidic Fe and Al compounds, leaching environment, and a probably underestimated role of iron with respect to the specific soil properties, e.g. extremely stabile, pseudo-sand like micro-aggregates. Considering the worldwide occurrence of these soils and the specificity of their physicochemical properties, I suggest soil forming processes and a new soil type clearly different from Andosols/Andisols in a narrow sense.

  3. REGIONAL SOIL WATER RETENTION IN THE CONTIGUOUS US: SOURCES OF VARIABILITY AND VOLCANIC SOIL EFFECTS

    EPA Science Inventory

    Water retention of mineral soil is often well predicted using algorithms (pedotransfer functions) with basic soil properties but the spatial variability of these properties has not been well characterized. A further source of uncertainty is that water retention by volcanic soils...

  4. Volcanism and soil mercury on Mars - Consequences for terrestrial microorganisms

    NASA Technical Reports Server (NTRS)

    Siegel, B. Z.; Siegel, S. M.

    1978-01-01

    An earth-Mars depletion formula proposed by Anders and Owen for volatiles is used to calculate a range of putative Hg levels for Martian volcanic soils based upon analyzed samples from Hawaii. The range is about 50-150 microgram per kg. When applied either in conventional or special media (e.g., basalt powder), these levels of Hg are effective inhibitors of the growth of earth microorganisms. Taken together with other hostile chemical and physical factors, volcanic toxicants would appear to provide a further deterrent to the accidental establishment of terrestrial microbiota on Mars.

  5. Colonisation of freshly deposited volcanic tephra by soil fungi

    NASA Astrophysics Data System (ADS)

    Tarasenko, Inga; Opfergelt, Sophie; Stenuit, Benoît; Daily, Hélène; Bonneville, Steeve; Müller, Dirk; Delmelle, Pierre

    2016-04-01

    In active volcanic regions, soils are repeatedly exposed to eruption products, notably tephra emissions. Deposition of volcanic tephra on soil may modify water and gas exchanges between the soil surface and the atmosphere. Through chemical weathering, the silicate glass and mineral components of freshly deposited tephra act as a source of bioavailable potassium and phosphorus. In addition, opportunist fungi may be able to enhance access to these elements via physical and biochemical processes. Altogether, tephra deposition has the potential to affect biological activity and hence, nutrient cycling in the buried soil. Here we present the preliminary results of an ongoing investigation aimed at shedding light on the interaction of soil fungi with freshly deposited tephra. The study site (elevation - 1755 m a.s.l.) is a coniferous forest on the northeastern slope of Etna volcano, Sicily, which received about 20 cm of tephra in November 2013. Soil and tephra samples were collected in September 2014 and October 2015. A variety of biological, chemical and mineralogical analyses were carried out to determine fungal biomass, fungi species and tephra weathering stage. Colonisation of the fresh tephra by fungi is evidenced by the high fungal biomass measured in this material. DNA analyses further indicate that these fungi originate from the soil beneath the tephra layer. While chemical weathering of the tephra material has started, there is no clear indication that fungi colonisation is enhancing this process. We will continue to monitor fungi-tephra interaction on Etna during the next few years.

  6. Magnetic susceptibility properties of pesticide contaminated volcanic soil

    NASA Astrophysics Data System (ADS)

    Agustine, Eleonora; Fitriani, Dini; Safiuddin, La Ode; Tamuntuan, Gerald; Bijaksana, Satria

    2013-09-01

    Pesticides, unfortunately, are still widely used in many countries as way to eradicate agricultural pests. As they are being used continuously over a long period of time, they accumulate as residues in soils posing serious threats to the environment. In this study, we study the changes in magnetite-rich volcanic soils that were deliberately contaminated by pesticide. Such changes, in any, would be useful in the detection of pesticide residue in contaminated soils. Two different types of magnetically strong volcanic soil from the area near Lembang, West Java, Indonesia were used in this study where they were contaminated with varying concentrations of pesticide. The samples were then measured for magnetic susceptibility at two different frequencies. The measurements were then repeated after a period of three months. We found a reduction of magnetic susceptibility as well as a reduction in SP (superparamagnetic) grains proportion in contaminated soil. These might be caused by pesticide-induced magnetic dissolution as supported by SEM analyses. However the impact of pesticide concentration as well as exposure time on magnetic dissolution is still inconclusive.

  7. Volatile metal deposits on lunar soils: Relation to volcanism

    NASA Technical Reports Server (NTRS)

    Reed, G. W., Jr.; Allen, R. O., Jr.; Jovanovic, S.

    1977-01-01

    Parallel leaching and volatilization experiments conducted on lunar samples and similar experiments on sphalerite do not supply the information needed to resolve the question of the chemical nature of pb 204, Zn, Bi and Tl deposits on lunar soil surfaces. It is proposed that in Apollo 17 mare and terra soils and fractions of pb 204, Zn and Tl that are insoluble under mild, hot pH 5HNO3, leaching conditions and involatile at 600 C were originally surface deposits which became immobilized by migration into the silicate substrate or by chemisorption. Only Bi is predominantly indigenous. The implication is also that the soils over their respective times of evolution were exposed to heavy metal vapors or that an episodic exposure occurred after they had evolved. A sequence of events is proposed to account for orange 74220 and black 74001 glasses by lava fountaining and for soil 74241 as tephra from an explosive volcanic eruption.

  8. Carbon Stabilization in Wet Tropical Forest Volcanic Soils

    NASA Astrophysics Data System (ADS)

    Marin-Spiotta, E.; Chadwick, O.; Kramer, M.

    2008-12-01

    Volcanic soils, particularly Andisols, have high carbon storage capacities due to the accumulation of highly reactive, non-crystalline minerals. Previous research along a pedogenic chronosequence on volcanic lava in Hawai'i found that soils in the intermediate weathering stage, dominated by allophane, contained the largest soil C stocks with slowest turnover rates. Potential mechanisms for long-term soil C stabilization include an accumulation of chemically recalcitrant C, microenvironmental conditions unfavorable for decomposition, and strong sorption of soluble and otherwise labile C to mineral and/or metals. In well-drained soils in wet climates, dissolved organic matter (DOM) is a likely main pathway for the transport of C from the zones of highest microbial activity to deeper mineral horizons. To address the production, transformation, and fate of dissolved organic matter (DOM), we have installed tension and zero tension lysimeters throughout sequentially deeper organic and mineral horizons in an intermediate aged soil (ca. 350k years) under wet (ca. 3000 mm mean annual rainfall) native tropical forest in Hawai'i. The soils are characterized by thick O horizons and Bh horizons 20-30 cm deep, followed by mineral horizons showing redoximorphic features. Bulk soil carbon to nitrogen ratios increase with soil depth, matching that of DOM in the surface organic horizons at 40-50 cm depth. Low pH does not seem to explain this accumulation of C-rich, N-depleted OM, as soils become less acidic with depth. Soil C:N are positively correlated with alumina, oxalate-extractable Al, and dithionite citrate-extractable Al. The greatest source of DOC is the forest floor (Oie), followed by the Oa horizon, and concentrations decrease significantly in the mineral horizons. DOC concentrations increase with total dissolved Al and Fe in the Oie horizon, and with total Fe in solution in the Bg horizon. In the Bh horizon, DOM C:N are negatively correlated with total Al and Fe in

  9. Prehistoric Agriculture and Soil Fertility on Lava Flows in Northern Arizona, USA: Results from the San Francisco Volcanic Field REU

    NASA Astrophysics Data System (ADS)

    Broadman, E.; Anderson, K. C.

    2013-12-01

    The San Francisco Volcanic Field in northern Arizona is home to ~600 cinder cones, the youngest of which is Sunset Crater (erupted ~AD 1100). This study documents trends in available phosphate and nitrate content with time, testing whether lowered soil pH from the addition of Sunset cinders increased soil fertility and became a factor in Anasazi agricultural success. Soil fertility is examined both before and after Sunset's eruption in soils of different ages that have developed from eolian deposition on top of lava flows. An increase in phosphate and nitrate levels following acidification would suggest that the presence of Sunset cinders brought the soils to the optimal pH for mobilization of these nutrients. The combined effects of the cinder layer retaining nutrients and water, wetter climates, and increases in phosphate and nitrate (both limiting nutrients for plant growth), would have contributed to Anasazi agricultural success after Sunset's eruption. Samples for this study were taken from eolian-derived soils of different ages atop lava flows in the San Francisco Volcanic Field. OSL data from these soils on Strawberry and SP Craters' lava flows yielded age estimates of ~12.3 ka (Strawberry) and ~32.7 ka (SP), on which a soil chronosequence was based. Results from the chronosequence supported these OSL ages, indicating that soils on the SP flow are older than those on the Strawberry flow. Field descriptions, Harden Development Indices, particle size analysis, and nutrient content analysis were used for this aspect of the project. An experimental acid wash method will be used to simulate the addition of Sunset's acidic cinders, and will yield data for phosphate and nitrate content after Sunset erupted. Preliminary results indicate that phosphate and nitrate accumulate in upper, eolian-derived horizons (Av, Bw) and in more deeply buried carbonate horizons (Bk). Higher concentrations of phosphate and nitrate were found in older (SP) soils than younger

  10. Soil CO2 flux baseline in an urban monogenetic volcanic field: the Auckland Volcanic Field, New Zealand

    NASA Astrophysics Data System (ADS)

    Mazot, Agnès; Smid, Elaine R.; Schwendenmann, Luitgard; Delgado-Granados, Hugo; Lindsay, Jan

    2013-11-01

    The Auckland Volcanic Field (AVF) is a dormant monogenetic basaltic field located in Auckland, New Zealand. Though soil gas CO2 fluxes are routinely used to monitor volcanic regions, there have been no published studies of soil CO2 flux or soil gas CO2 concentrations in the AVF to date or many other monogenetic fields worldwide. We measured soil gas CO2 fluxes and soil gas CO2 concentrations in 2010 and 2012 in varying settings, seasons, and times of day to establish a baseline soil CO2 flux and to determine the major sources of and controlling influences on Auckland's soil CO2 flux. Soil CO2 flux measurements varied from 0 to 203 g m-2 day-1, with an average of 27.1 g m-2 day-1. Higher fluxes were attributed to varying land use properties (e.g., landfill). Using a graphical statistical approach, two populations of CO2 fluxes were identified. Isotope analyses of δ13CO2 confirmed that the source of CO2 in the AVF is biogenic with no volcanic component. These data may be used to assist with eruption forecasting in the event of precursory activity in the AVF, and highlight the importance of knowing land use history when assessing soil gas CO2 fluxes in urban environments.

  11. Volatile metal deposits on lunar soils - Relation to volcanism

    NASA Technical Reports Server (NTRS)

    Reed, G. W., Jr.; Jovanovic, S.; Allen, R. O., Jr.

    1977-01-01

    Parallel leaching and volatilization experiments conducted on lunar samples and similar experiments on sphalerite do not supply the information needed to resolve the question of the chemical nature of Pb-204, Zn, Bi, and Tl deposits on lunar soil surfaces. It is proposed that in Apollo 17 mare and terra soils the fractions of Pb-204, Zn, and Tl that are insoluble under mild, hot pH 5 HNO3, leaching conditions and involatile at 600 C were originally surface deposits which became immobilized by migration into the silicate substrate or by chemisorption. Most of the Bi does not seem to be the result of such a deposit. The implication is also that the soils, over their respective times of evolution, were exposed to heavy metal vapors or that an episodic exposure occurred after they had evolved. A sequence of events is proposed to account for orange 74220 and black 74001 glasses by lava fountaining and for soil 74241 as tephra from an explosive volcanic eruption.

  12. Soil microbial communities as suitable bioindicators of trace metal pollution in agricultural volcanic soils

    NASA Astrophysics Data System (ADS)

    Parelho, Carolina; dos Santos Rodrigues, Armindo; do Carmo Barreto, Maria; Gonçalo Ferreira, Nuno; Garcia, Patrícia

    2015-04-01

    Summary: The biological, chemical and physical properties of soil confer unique characteristics that enhance or influence its overall biodiversity. The adaptive character of soil microbial communities (SMCs) to metal pollution allows discriminating soil health, since changes in microbial populations and activities may function as excellent indicators of soil pollutants. Volcanic soils are unique naturally fertile resources, extensively used for agricultural purposes and with particular physicochemical properties that may result in accumulation of toxic substances, such as trace metals (TM). In our previous works, we identified priority TM affecting agricultural Andosols under different agricultural land uses. Within this particular context, the objectives of this study were to (i) assess the effect of soil TM pollution in different agricultural systems (conventional, traditional and organic) on the following soil properties: microbial biomass carbon, basal soil respiration, metabolic quotient, enzymatic activities (β-glucosidase, acid phosphatase and dehydrogenase) and RNA to DNA ratio; and (ii) evaluate the impact of TM in the soil ecosystem using the integrated biomarker response (IBR) based on a set of biochemical responses of SMCs. This multi-biomarker approach will support the development of the "Trace Metal Footprint" for different agricultural land uses in volcanic soils. Methods: The study was conducted in S. Miguel Island (Azores, Portugal). Microbial biomass carbon was measured by chloroform-fumigation-incubation-assay (Vance et al., 1987). Basal respiration was determined by the Jenkinson & Powlson (1976) technique. Metabolic quotient was calculated as the ratio of basal respiration to microbial biomass C (Sparkling & West, 1988). The enzymatic activities of β-glucosidase and acid phosphatase were determined by the Dick et al. (1996) method and dehydrogenase activity by the Rossel et al. (1997) method. The RNA and DNA were co-extracted from the same

  13. Selective preservation of carbohydrates in volcanic ash soils

    NASA Astrophysics Data System (ADS)

    Kaal, J.; Buurman, P.; Nierop, K. G. J.; Piccolo, A.

    2009-04-01

    Volcanic soils (Andosols) are formed in volcanic ash and depending on environmental and climatic factors they develop to two main forms, either allophanic Andosols (dominated by amorphous minerals) or non-allophanic Andosols (dominated by Al/Fe organic matter complexes). Andosols contain the largest amounts of organic carbon of all mineral soil orders. In recent studies using analytical pyrolysis techniques on the soil organic matter (SOM) of allophanic soils from the Azores Islands (Portugal) there was no indication of preservation of plant-derived organic matter by allophane or Al3+, but the presence of large amounts of (microbial) polysaccharides and chitin suggested that secondary organic matter products were stabilized. In the present study we used 13C NMR to further explore the organic matter of the Andosols of the Azores, and applied a molecular mixing model (MMM; ascribing characteristic resonances to the main biocomponent classes carbohydrate, protein, lipid, lignin and char) to the quantified NMR spectra to allow for a quantitative comparison with pyrolysis-GC/MS. The dominance of O-alkyl and di-O-alkyl C in the NMR spectra and carbohydrate contribution to the predictions made by the MMM (50 ± 8%) confirms that the majority of the SOM can still be recognised as carbohydrate. The accumulation of secondary/microbial carbohydrates (and, to a lesser extent, secondary proteinaceous matter and chitins) is thus a key characteristic of these Andosols. NMR-MMM and pyrolysis-GC/MS were in rough agreement. However, NMR does not recognise chitin (N-containing carbohydrate-like material) and chitin-associated protein, nor can it be used to estimate the degree of degradation of the carbohydrates. Therefore, NMR (as applied here) has a very limited capacity for characterisation of the SOM particularly in the Andosols studied. On the other hand, large peaks from carboxylic and amidic functional groups detected by NMR were not observed by pyrolysis-GC/MS. It is therefore

  14. Influences of Farming Management on Quality and Quantity of Soil Organic Matter in Volcanic Ash Soil

    NASA Astrophysics Data System (ADS)

    Yoshikawa, M.; Tanaka, H.; Matsumura, S.; Shimizu, T.; Zhang, M.

    2013-12-01

    Storage of soil organic matter (SOM) in terrestrial ecosystem plays a significant role in reducing carbon flux to the atmosphere and thus prevents the earth from global warming. In agricultural field, farming management, such as manure application and/or reduced tillage, are known to be effective methods to stimulate SOM storage. Volcanic ash soil, categorized into Andosols, is a major type of upland soil in Japan, and the soil contains relatively high concentration of SOM, meaning that volcanic ash soil can play an important role in carbon storage in Japan. To investigate the influences of farming management on quality and quantity of SOM, an empirical study was carried out in an upland soil field derived from volcanic ash. Surface soil samples were taken every three months from the field and fractionated physically and chemically. As for the physical fractionation, 53 μm sieving was performed. SOM in the samples were sorted into particulate organic matter (POM) denoting organic matter with particle size greater than 53 μm and less than 2 mm, and mineral-associated organic matter (MOM) denoting less than 53 μm. In addition, both POM and MOM were further fractionated chemically by extraction with pyrophosphate buffer solutions at three different pH levels. The fractionated organic matter as well as unfractionated SOM were analyzed and quantified for organic carbon, nitrogen content. This study induced the following results and findings. The manure and/or reduced tillage treatments can significantly increase the particulate organic carbon (POC) and all chemically fractionated POC contents. Especially, POC extracted with the buffer solution at pH4 (POCpH4) and the differences between POC and POC extracted with the buffer solution at pH10 (POC-POCpH10) have strong correlations with SOC, and manure application can effectively increase POC-POCpH10 fraction. The results indicate that these fractionated organic carbons would contribute storage of organic matter in

  15. Soil Properties Affecting the Reductive Capacity of Volcanic Ash Soils in Korea

    NASA Astrophysics Data System (ADS)

    Chon, C.; Ahn, J.; Kim, K.; Park, K.

    2008-12-01

    Volcanic ash soils or Andisols have distinct chemical and mineralogical properties. The unique chemical properties of Andisols are due to their Al-rich elemental composition, the highly reactive nature of their colloidal fractions, and their large surface area. The soils that developed from volcanic ash on Jeju Island, Korea, were classified as typical Andisols. The soils had an acidic pH, high water content, high organic matter, and clay-silty texture. The crystalline minerals in the samples were mainly ferromagnesian minerals, such as olivine and pyroxene, and iron oxides, such as magnetite and hematite derived from basaltic materials. A large amount of gibbsite was found in the subsurface horizon as a secondary product of the migration of excess Al. In addition, we found that considerable amounts of poorly ordered minerals like allophane and ferrihydrite were present in the Jeju soils. The SiO2 contents were lower than those of other soil orders, while the Al2O3 and Fe2O3 contents were higher. These results reflect some of the important chemical properties of Andisols. The chromium (VI/III) redox couple was used in the reductive capacity measurement. The mean reductive capacity of the Jeju soils was 6.53 mg/L reduced Cr(VI), which is 5.1 times higher than that of non-volcanic ash soils from inland Korea. The reductive capacity of the inland soils was correlated with the total carbon content. Such a high capacity for the reduction of soluble Cr(VI) must also be due to the relatively high carbon contents of the Jeju soils. Nevertheless, despite having 20 times higher total carbon contents, there was no correlation between the reductive capacity of the Jeju soils and the carbon content. These results imply that the reductive capacity of Jeju soils is not only controlled by the carbon content, but is also affected by other soil properties. Correlations of the reductive capacity with major elements showed that Al and Fe were closely connected to the reductive

  16. Interannual variations of soil organic carbon fractions in unmanaged volcanic soils (Canary Islands, Spain).

    PubMed

    Armas-Herrera, Cecilia María; Mora, Juan Luis; Arbelo, Carmen Dolores; Rodríguez-Rodríguez, Antonio

    2012-10-01

    The stability over time of the organic C stocked in soils under undisturbed ecosystems is poorly studied, despite being suitable for detecting changes related to climate fluctuations and global warming. Volcanic soils often show high organic C contents due to the stabilization of organic matter by short-range ordered minerals or Al-humus complexes. We investigated the dynamics of different organic C fractions in volcanic soils of protected natural ecosystems of the Canary Islands (Spain) to evaluate the stability of their C pools. The study was carried out in 10 plots, including both undisturbed and formerly disturbed ecosystems, over two annual periods. C inputs to (litterfall) and outputs from (respiration) the soil, root C stocks (0-30 cm), soil organic C (SOC) fractions belonging to C pools with different degrees of biogeochemical stability -total oxidisable C (TOC), microbial biomass C (MBC), water soluble C (WSC), hot-water extractable C (HWC), humic C (HSC), - and total soil N (TN) (at 0-15 and 15-30 cm) were measured seasonally.A statistically significant interannual increase in CO(2) emissions and a decrease in the SOC, mainly at the expense of the most labile organic forms, were observed, while the root C stocks and litterfall inputs remained relatively constant over the study period. The observed changes may reflect an initial increase in SOC resulting from low soil respiration rates due to drought during the first year of study. The soils of nearly mature ecosystems were more apparently affected by C losses, while those undergoing the process of active natural regeneration exhibited disguised C loss because of the C sequestration trend that is characteristic of progressive ecological succession. PMID:23145325

  17. Interannual variations of soil organic carbon fractions in unmanaged volcanic soils (Canary Islands, Spain)

    PubMed Central

    Armas-Herrera, Cecilia María; Mora, Juan Luis; Arbelo, Carmen Dolores; Rodríguez-Rodríguez, Antonio

    2012-01-01

    The stability over time of the organic C stocked in soils under undisturbed ecosystems is poorly studied, despite being suitable for detecting changes related to climate fluctuations and global warming. Volcanic soils often show high organic C contents due to the stabilization of organic matter by short-range ordered minerals or Al-humus complexes. We investigated the dynamics of different organic C fractions in volcanic soils of protected natural ecosystems of the Canary Islands (Spain) to evaluate the stability of their C pools. The study was carried out in 10 plots, including both undisturbed and formerly disturbed ecosystems, over two annual periods. C inputs to (litterfall) and outputs from (respiration) the soil, root C stocks (0–30 cm), soil organic C (SOC) fractions belonging to C pools with different degrees of biogeochemical stability –total oxidisable C (TOC), microbial biomass C (MBC), water soluble C (WSC), hot-water extractable C (HWC), humic C (HSC), – and total soil N (TN) (at 0–15 and 15–30 cm) were measured seasonally.A statistically significant interannual increase in CO2 emissions and a decrease in the SOC, mainly at the expense of the most labile organic forms, were observed, while the root C stocks and litterfall inputs remained relatively constant over the study period. The observed changes may reflect an initial increase in SOC resulting from low soil respiration rates due to drought during the first year of study. The soils of nearly mature ecosystems were more apparently affected by C losses, while those undergoing the process of active natural regeneration exhibited disguised C loss because of the C sequestration trend that is characteristic of progressive ecological succession. PMID:23145325

  18. Soils and their distribution on Bambouto volcanic mountain, West Cameroon highland, Central Africa

    NASA Astrophysics Data System (ADS)

    Tematio, P.; Kengni, L.; Bitom, D.; Hodson, M.; Fopoussi, J. C.; Leumbe, O.; Mpakam, H. G.; Tsozué, D.

    2004-06-01

    Morphological, physical and chemical studies were carried out on soils of Mount Bambouto, a volcanic mountain of the West Cameroon highland. These studies show that the soils of this region can be divided into seven groups according to Soils Taxonomy USA [Soil taxonomy: a basic system of soil classification for making and interpreting soils surveys: USDA Agriculture Handbook 436: Washington, DC, US Government Pronting Office, 1975, 754]: lithic dystrandept soils, typical dystrandept soils, oxic dystrandept soils, typical haplohumox soils, typical kandiudox soils, tropopsamment soils and umbriaquox soils. A soils map of this region at scale 1:50,000 has been drawn up, using the seven soils groups above as soil cartography units. These soils are organised into of three main categories: soils with andic characteristics in the upper region of the mountain (lithic dystrandept soils, typical dystrandept soils and oxic dystrandept soils); ferrallitic soils in the lower part of the mountain (typical haplohumox soils and typical kandiudox soils) and imperfectly developed soils (tropopsamment soils and umbraquox soils).

  19. Climatic controls on soil hydraulic properties along soil chronosequences on volcanic parent material

    NASA Astrophysics Data System (ADS)

    Beal, L. K.; Lohse, K. A.; Godsey, S.; Huber, D. P.

    2013-12-01

    . We observe that θ decreases with age, and α occurs at higher tensions. Soil horizons are developed dominantly on the cinder cones. These model estimates appear to match well with preliminary field measurements. Tropical climates enhance the weathering of basaltic parent material. The mean annual precipitation in the Hawaiian site is 2500 mm, and 310 mm at COTM. Accumulation of rainfall increases the weathering rate of the parent material. Using previous work characterizing the physical characteristics of soil across the Hawaii chronosequence to model the contrasting soils, we found that the 0.3 and 20 ka Hawaii soils had similar hydraulic properties; θ values were approximately 0.45 cm3/cm3 and Ks values were 6 cm/hr. However, these Hawaiian soils contrasted and were quantitatively lower than the entire COTM chronosequence. At the 2.1 ka COTM soil, Ks was 17 cm/hr and θ was 0.52-0.65 cm3/cm3 whereas at the 13.9 ka soil, Ks was 12 cm/hr and θ was 0.52 cm3/cm3. The 0.3 ka Hawaiian soil had a 20-30% higher silt content than the 2.1 ka COTM soil. Our models help quantify rates of soil development and hydraulic properties developed through time on volcanic parent materials.

  20. Assessing microbial activities in metal contaminated agricultural volcanic soils - An integrative approach.

    PubMed

    Parelho, C; Rodrigues, A S; Barreto, M C; Ferreira, N G C; Garcia, P

    2016-07-01

    Volcanic soils are unique naturally fertile resources, extensively used for agricultural purposes and with particular physicochemical properties that may result in accumulation of toxic substances, such as trace metals. Trace metal contaminated soils have significant effects on soil microbial activities and hence on soil quality. The aim of this study is to determine the soil microbial responses to metal contamination in volcanic soils under different agricultural land use practices (conventional, traditional and organic), based on a three-tier approach: Tier 1 - assess soil microbial activities, Tier 2 - link the microbial activity to soil trace metal contamination and, Tier 3 - integrate the microbial activity in an effect-based soil index (Integrative Biological Response) to score soil health status in metal contaminated agricultural soils. Our results showed that microbial biomass C levels and soil enzymes activities were decreased in all agricultural soils. Dehydrogenase and β-glucosidase activities, soil basal respiration and microbial biomass C were the most sensitive responses to trace metal soil contamination. The Integrative Biological Response value indicated that soil health was ranked as: organic>traditional>conventional, highlighting the importance of integrative biomarker-based strategies for the development of the trace metal "footprint" in Andosols. PMID:27057992

  1. Chemical composition of soils in the areas of volcanic ashfalls around active volcanoes in Kamchatka

    NASA Astrophysics Data System (ADS)

    Zakharikhina, L. V.; Litvinenko, Yu. S.

    2016-03-01

    The geochemical features of volcanic soils (Andosols) in the northern soil province of Kamchatka are identified. The background regional concentrations ( Cb r ) of most of chemical elements in the studied soils are lower than their average concentrations in soils of the world and in the European volcanic soils. Only Na, Ca, and Mg are present in elevated concentrations in all the studied soils in the north of Kamchatka. Regional background concentrations of elements are exceeded by 1.6 times in the area of active ashfalls of the Tolbachik volcano and by 1.3 times in the area of active ashfalls of the Shiveluch volcano. The concentrations of mobile forms of elements in these areas exceed their regional background concentrations by 2.1 and 2.6 times, respectively.

  2. Cemented Volcanic Soils, Martian Spectra and Implications for the Martian Climate

    NASA Technical Reports Server (NTRS)

    Bishop, J. L.; Schiffman, P.; Drief, A.; Southard, R. J.

    2004-01-01

    Cemented soils formed via reactions with salts are studied here and provide information about the climate when they formed. Spectroscopic and microprobe studies have been performed on cemented volcanic crusts in order to learn about the composition of these materials, how they formed, and what they can tell us about climatic interactions with surface material on Mars to form cemented soils. These crusts include carbonate, sulfate and opaline components that may all be present in cemented soil units on Mars.

  3. The use of volcanic soil as mineral landfill liner--I. Physicochemical characterization and comparison with zeolites.

    PubMed

    Navia, Rodrigo; Hafner, Georg; Raber, Georg; Lorber, Karl E; Schöffmann, Elke; Vortisch, Walter

    2005-06-01

    The main physicochemical characteristics of the volcanic soil of Southern Chile, with allophane as the main pedogenic mineral phase were analysed and compared with common zeolites (clinoptilolite) of the European market. The ultimate goal of this study was to test volcanic soil for the use as mineral landfill liner. The main results indicated that the clay and silt fractions together of the volcanic soil were between 38 and 54%. The buffering capacity of the volcanic soil was higher compared with the studied zeolites, whereas the cationic exchange capacity of the volcanic soil (between 5.2 and 6.5 cmol + kg(-1)) is of the same order of magnitude of the studied zeolites (between 9.7 and 11.4 cmol + kg(-1)). Moreover, the anionic exchange capacity of the volcanic soil was higher compared to the zeolites analysed. The hydraulic conductivity of the volcanic soil, measured in the laboratory at maximum proctor density, ranges between 5.16 x 10(-9) and 6.48 x 10(-9) m s(-1), a range that is comparable to the value of 4.51 x 10(-9) m s(-1) of the studied zeolite. The Proctor densities of the volcanic soil are in a lower range (between 1.11 and 1.15 g ml(-1)) compared with zeolites (between 1.19 and 1.34 g ml(-1)). The volcanic soil physicochemical characteristics are comparable to all the requirements established in the Austrian landfill directive (DVO, 2000). Therefore, the use as mineral landfill basal sealing of the analysed volcanic soil appears reasonable, having a pollutant adsorption capacity comparable to zeolites. It is of special interest for Southern Chile, because there are no alternative mineral raw materials for basal liners of landfills. PMID:15988944

  4. Soil radon measurements as a potential tracer of tectonic and volcanic activity

    NASA Astrophysics Data System (ADS)

    Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

    2016-04-01

    In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009–2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes.

  5. Soil radon measurements as a potential tracer of tectonic and volcanic activity.

    PubMed

    Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

    2016-01-01

    In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009-2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes. PMID:27079264

  6. Soil radon measurements as a potential tracer of tectonic and volcanic activity

    PubMed Central

    Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

    2016-01-01

    In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009–2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes. PMID:27079264

  7. Soil and geomorphic evolution within the rolling red plains using pleistocene volcanic ash deposits

    NASA Astrophysics Data System (ADS)

    Carter, Brian J.; Ward, Phil A.; Shannon, Jean T.

    1990-09-01

    Pleistocene volcanic ash deposits are found within alluvium from the Arkansas river south to the Brazos river. This drainage area includes tributaries originating in the High Plains, the Raton volcanic field and the Rocky Mountain Front Range within the states of Colorado, New Mexico, Kansas, Texas, and Oklahoma. Thirteen ash deposits are dated from within the High Plains of Kansas and Texas eastward into central Oklahoma to understand the geomorphic history and improve soil and geologic mapping. Within the study area unsolidated Tertiary and Quaternary sediments deposited in a west to east direction overlie Triassic, Permian, and Pennsylvanian bedrock. Volcanic ash deposits are predominantly Early to Middle Pleistocene age. Volcanic ash deposits were dated by the fission track method on shards. The ash deposits are contained within four land resource regions, the Southern and Central High Plains, the High Plains Breaks, the Rolling Red Plains, and the Reddish Prairies. Extensive Middle Pleistocene constructional stream terrace surfaces occur within the Rolling Red Plains. Multiple stream terrace surfaces were recognized across the study area with the highest level being dated Early Pleistocene to Pliocene and the lowest bordering the Holocene floodplains. Topographic cross-sections (100 km long at 1:24,000 scale) transecting dated ash deposits and perpendicular to major river systems were used to distinguish terrace levels. Constructional terrace surfaces dated by ash deposits range from 21 to 100 m above and 1 to 16 km distance from present river channels. Soil orders formed in Quaternary alluvium are Entisols, Inceptisols, Mollisols, Alfisols and Vertisols. Ustic and udic soil moisture regimes and a thermic (15 to 22°C mean annual temperature) soil temperature regime dominate the study area. The same soil series is often mapped on terrace surfaces spanning Early to Middle Pleistocene age because current classification does not recognize differences in deeply

  8. Irreversibility of 2,4-Dichlorophenoxyacetic Acid Sorption onto a Volcanic Ash Soil

    NASA Astrophysics Data System (ADS)

    Mon, E.; Kawamoto, K.; Komatsu, T.; Moldrup, P.

    2008-12-01

    Pesticide sorption and desorption in soils are key processes governing fate and transport of pesticides in the soil environment. The irreversibility (or hysteresis) in the processes of pesticide sorption and desorption needs to be known to accurately predict behavior of pesticides in soil systems. 2,4-dichlorophenoxyacetic acid (2,4-D) is a widely used pesticide in agriculture fields. However, only few studies of 2,4-D adsorption onto Andosols (volcanic ash soils) have been published, and the knowledge of 2,4-D desorption onto Andosols is very limited. In this study, a volcanic ash soil sampled from a pasture site in Nishi-Tokyo, Japan was used as a sorbent in order to investigate the irreversibility of 2,4-D sorption. For comparison, a pure clay mineral (kaolinite) obtained from Clay Science Society of Japan (CSSJ) was also used. 2,4-D solutions with three concentrations (0.011, 0.022 and 0.045 mmol/L) were prepared in artificial rain water (ARW= 0.085mM NaCl + 0.015mM CaCl2) to simulate field conditions. To prepare the sample solutions, the solid mass/liquid volume ratio of 1:10 was used for both sorbents (volcanic ash soil and kaolinite). The experiments were conducted in triplicate using a batch method under different pH conditions to examine the effect of pH. Desorption was measured during a equilibration procedure: After removal of 7 mL of supernatant in the sorption step, 7 mL of ARW excluding 2,4-D was added to the sample solution after which, it was equilibrated and centrifuged. The procedure was performed sequentially three or four times to obtain a desorption isotherm. Sorption and desorption generally followed Freundlich isotherms. The results showed markedly effects of pH on 2,4-D sorption and desorption in both the soil and kaolinite, with the percentage of sorption increasing with decreasing pH whereas the percentage of desorption decreased. There was a larger adsorption-desorption hysteresis in the volcanic ash soil as compared to kaolinite

  9. Radiocaesium fallout behaviour in volcanic soils in Iceland.

    PubMed

    Sigurgeirsson, M A; Arnalds, O; Palsson, S E; Howard, B J; Gudnason, K

    2005-01-01

    The retention of 137Cs in various types of Andosols in Iceland was investigated. Soils were sampled at 29 sites with varying precipitation and environmental conditions. Samples were obtained from 0 to 5, 5 to 10, and 10 to 15 cm depths. The amount of radiocaesium present was quite variable, ranging between 300 and 4800 Bq m(-2) and correlated closely to total annual precipitation (r2=0.71). The majority of 137Cs, 82.7% on average, was retained in the uppermost 5 cm of the soil. The greatest penetration of 137Cs was observed for organic Histosols (76.3% in top 5 cm). The Icelandic Vitrisols (barren, poorly developed Andosols) are coarse grained with only 2-5% clay content and contain little organic matter (<1%). Yet these soils retained 74% of 137Cs in the top 5 cm. The results indicate that radiocaesium fallout is strongly retained by colloidal materials characteristic of Andosols, such as allophane and ferrihydrite. Most soils in Iceland are subject to severe and prolonged freezing and waterlogging; despite this, 137Cs is retained in the upper soil horizons and vertical migration is negligible in Icelandic Andosols. However, erosion and aeolian activity can markedly influence the amount and vertical distribution of radiocaesium in Icelandic soils. PMID:15571875

  10. The structural-functional organization of thermotolerant complexes of actinomycetes in desert and volcanic soils

    NASA Astrophysics Data System (ADS)

    Zenova, G. M.; Kurapova, A. I.; Lysenko, A. M.; Zvyagintsev, D. G.

    2009-05-01

    It has been found that the number of thermotolerant actinomycetes in strongly heated soils of deserts and volcanic regions is comparable to or exceeds the number of mesophilic actinomycetes. Among the latter group, streptomyces usually predominate; among thermotolerant actinomycetes, representatives of the Micromonospora, Streptosporangium, Actinomadura, Saccharopolyspora, Microtetraspora, and Microbispora genera are identified. Thermotolerant actinomycetes display the full cycle of their development in these soils. The method of fluorescent in situ hybridization has made it possible to determine that mycelial forms predominate among the metabolically active representatives of Actinobacteria; their portion increases with the rise in the temperature of soil incubation.

  11. Solute Diffusivity of Repacked Volcanic Ash Soil: Effect of Changes in Pore Size Distribution due to Soil Compaction

    NASA Astrophysics Data System (ADS)

    Perera, M. S.; Resurreccion, A. C.; Kawamoto, K.; Komatsu, T.; Moldrup, P.

    2007-12-01

    Diffusion is the dominant spreading mechanism of contaminants dissolved in soil-water in the absence of soil- water flow. Solute diffusion coefficient, Ds, is a key parameter in investigating the fate and transport of contaminants from a polluted soil site. However, only a few studies on quantifying Ds as a function of soil- water content were done, especially for aggregated soils with a dual pore system such as volcanic ash soils (Andisols). In this study, we investigated the effect of bulk density on pore size distribution, and, consequently, on solute diffusivity (Ds/Do, where Do is the solute diffusion coefficient in pure water) in repacked volcanic ash soil taken at 5-10 cm depth at a pasture site in Nishi-Tokyo, Japan. Measurements of Ds were done on sieved and repacked soil at three bulk densities (0.62 g cm-3 , 0.7 g cm-3, and 0.8 g cm-3 ) and at three soil moisture conditions at pF (= log (-ψ; soil-water matric potential in cm H2O)) 1.8, 2, and 3 for each bulk density. Half-cell method was used to measure Ds where the source and sink half cells (each cell of 10-cm length and 4.9 cm in diameter) were joined together and the concentration profile was analyzed after a substantial time to determine Ds. Results showed that at a particular bulk density, Ds decreased with decreasing degree of saturation. This is expected since as the soil becomes drier, water films become disconnected resulting in a decrease in Ds. On the other hand, at a particular degree of saturation, the magnitude of Ds considerably decreases with increasing dry bulk density. As soil is compacted (and thus the increase in bulk density), the observed pore size distribution obtained from soil-water retention curve changes where the mainly inter-aggregate large pores become smaller and soil particles become closer to each other. This reduction in inter-aggregate pore size likely increases the liquid-phase tortuosity resulting in the decrease in Ds/Do at soil-water content at pF < 3. The soil

  12. Sorption kinetics of diuron on volcanic ash derived soils.

    PubMed

    Cáceres-Jensen, Lizethly; Rodríguez-Becerra, Jorge; Parra-Rivero, Joselyn; Escudey, Mauricio; Barrientos, Lorena; Castro-Castillo, Vicente

    2013-10-15

    Diuron sorption kinetic was studied in Andisols, Inceptisol and Ultisols soils in view of their distinctive physical and chemical properties: acidic pH and variable surface charge. Two types of kinetic models were used to fit the experimental dates: those that allow to establish principal kinetic parameters and modeling of sorption process (pseudo-first-order, pseudo-second-order), and some ones frequently used to describe solute transport mechanisms of organic compounds on different sorbents intended for remediation purposes (Elovich equation, intraparticle diffusion, Boyd, and two-site nonequilibrium models). The best fit was obtained with the pseudo-second-order model. The rate constant and the initial rate constant values obtained through this model demonstrated the behavior of Diuron in each soil, in Andisols were observed the highest values for both parameters. The application of the models to describe solute transport mechanisms allowed establishing that in all soils the mass transfer controls the sorption kinetic across the boundary layer and intraparticle diffusion into macropores and micropores. The slowest sorption rate was observed on Ultisols, behavior which must be taken into account when the leaching potential of Diuron is considered. PMID:23995557

  13. Risk of classic Kaposi sarcoma with residential exposure to volcanic and related soils in Sicily

    PubMed Central

    Pelser, Colleen; Dazzi, Carmelo; Graubard, Barry I.; Lauria, Carmela; Vitale, Francesco; Goedert, James J.

    2009-01-01

    Purpose Before AIDS, endemic (African) Kaposi sarcoma (KS) was noted to occur in volcanic areas and was postulated to result from dirt chronically embedded in the skin of the lower extremities. The primary cause of all KS types is KS-associated herpesvirus (KSHV) infection, but co-factors contribute to the neoplasia. We investigated whether residential exposure volcanic or related soils was associated with the risk of classic Kaposi sarcoma (cKS) in Sicily. Methods Risk of incident cKS (n=141) compared to population-based KSHV seropositive controls (n=123) was estimated for residential exposure to four types of soil, categorized with maps from the European Soil Database and direct surveying. Questionnaire data provided covariates. Results Residents in communities high in luvisols were approximately 2.7-times more likely to have cKS than those in communities with no luvisols. Risk was not specific for cKS on the limbs, but it was elevated approximately 4–5-fold with frequent bathing or tap water drinking in high luvisols communities. Risk was unrelated to communities high in andosols, tephra, or clay soils. Conclusions Iron and alumino-silicate clay, major components of luvisols, may increase cKS risk, but formal investigation and consideration of other soil types and exposures are needed. PMID:19576540

  14. Adsorption of glyphosate on variable-charge, volcanic ash-derived soils.

    PubMed

    Cáceres-Jensen, L; Gan, J; Báez, M; Fuentes, R; Escudey, M

    2009-01-01

    Glyphosate (N-phosphonometylglycine) is widely used due to its broad spectrum of activity and nonselective mode of action. In Chile it is the most used herbicide, but its adsorption behavior in the abundant and widespread variable charge soils is not well understood. In this study, three volcanic ash-derived soils were selected, including Andisols (Nueva Braunau and Diguillin) and Ultisols (Collipulli), to evaluate the adsorption kinetics, equilibrium isotherms, and the effect of pH in glyphosate adsorption. The influence of glyphosate on soil phosphorus retention was also studied. Glyphosate was rapidly and strongly adsorbed on the selected soils, and adsorption isotherms were well described by the Freundlich relationship with strong nonlinearity (n(fads) < 0.5). The n(fads) values were consistently higher than n(fdes) values, suggesting strong hysteresis. Adsorption (K(ads)) increased strongly when pH decreased. The presence of glyphosate (3200 mug mL(-1)) changed the adsorption behavior of phosphate at its maximum adsorption capacity. Andisol soils without the addition of glyphosate had similar mean K(ads) values for Nueva Braunau (5.68) and Diguillin (7.38). Collipulli had a mean K(ads) value of 31.58. During the successive desorption steps, glyphosate at the highest level increased K(ads) values for phosphate in the Andisol soils but had little effect in the Ultisol soil. This different behavior was probably due to the irreversible occupation of some adsorption sites by glyphosate in the Ultisol soil attributed to the dominant Kaolinite mineral. Results from this study suggest that in the two types of volcanic soils, different mechanisms are involved in glyphosate and phosphate adsorption and that long-term use of glyphosate may impose different effects on the retention and availability of phosphorus. Volcanic ash-derived soils have a particular environmental behavior in relation to the retention of organic contaminants, representing an environmental substrate

  15. Two pools of old carbon in a volcanic-ash soil revealed by sequential density fractionation

    NASA Astrophysics Data System (ADS)

    Wagai, R.; Shirato, Y.; Uchida, M.; Hiradate, S.

    2010-12-01

    Volcanic-ash soils are often darker and hold significantly greater amounts of organic matter (OM) than non-volcanic soils presumably because inorganic constituents unique to such soil (e.g., poorly-crystalline minerals and dissolved aluminum) have high capacity to stabilize OM. It has been shown that carbon (C) in Japanese volcanic-ash soils can be quite old (>1000 yr) even at surface horizons. Yet little information is available on how the old C is stabilized in soil matrix. Fractionation of soil according to particle density is an effective approach to distinguish the OM of different degrees of mineral associations and to elucidate SOM stabilization processes. Here we examined a surface (Ap) horizon of an allophanic Andisol in central Japan by isolating six density fractions (from F1: <1.6 g/cc to F6: >2.5 g/cc). Almost half of total C was distributed to F4 (2.0-2.25 g/cc), 26% of total C to F3 (1.8-2.0 g/cc), 10-12% to F2 (1.6-1.8 g/cc) and F5 (2.25-2.5 g/cc), and 3-4% to F1 and F6, respectively. The concentration of allophane was also highest in F4 then F3, implying that allophane-OM association is the main form of OM present in this soil. In accord with the reports on other soil types, C-14 age generally increased with particle density from F1 (modern) to F5 (1300 yr libby age) and slightly declined to F6 (1000 yr). The clear exception to this trend was the old C age (1300 yr) of 1.6-1.8 g/cc fraction. Following results suggested the presence of char in this fraction: (i) C:N ratio was the highest (22), (ii) aromatic-C:O-alkyl-C ratio nearly doubled from F1 to F2, and (iii) large numbers of small, dark fragments were microscopically observed along with plant detritus fragments. In contrast to F2, equally-old C in F5 (2.25-2.5 g/cc) appear to be strongly altered by microbial process and bound to mineral particles. F5 had lower C:N ratio of 9.7 and was more enriched in N-15 (+5 per mill) and C-13 (+2 per mill) compared to F2. The presence of contrasting forms of

  16. Methanotrophic activity and bacterial diversity in volcanic-geothermal soils at Pantelleria island (Italy)

    NASA Astrophysics Data System (ADS)

    Gagliano, A. L.; D'Alessandro, W.; Tagliavia, M.; Parello, F.; Quatrini, P.

    2014-04-01

    Volcanic and geothermal systems emit endogenous gases by widespread degassing from soils, including CH4, a greenhouse gas twenty-five times as potent as CO2. Recently, it has been demonstrated that volcanic/geothermal soils are source of methane, but also sites of methanotrophic activity. Methanotrophs are able to consume 10-40 Tg of CH4 a-1 and to trap more than 50% of the methane degassing through the soils. We report on methane microbial oxidation in the geothermally most active site of Pantelleria island (Italy), Favara Grande, whose total methane emission was previously estimated in about 2.5 t a-1. Laboratory incubation experiments with three top-soil samples from Favara Grande indicated methane consumption values up to 950 ng g-1 dry soil h-1. One of the three sites, FAV2, where the highest oxidation rate was detected, was further analysed on a vertical soil profile and the maximum methane consumption was measured in the top-soil layer but values > 100 ng g-1 h-1 were maintained up to a depth of 15 cm. The highest consumption rate was measured at 37 °C, but a still recognizable consumption at 80 °C (> 20 ng g-1 h-1) was recorded. In order to estimate the bacterial diversity, total soil DNA was extracted from Favara Grande and analysed using a Temporal Temperature Gradient gel Electrophoresis (TTGE) analysis of the amplified bacterial 16S rRNA gene. The three soil samples were probed by PCR using standard proteobacterial primers and newly designed verrucomicrobial primers targeting the unique methane monooxygenase gene pmoA; the presence of methanotrophs was detected in sites FAV2 and FAV3, but not in FAV1, where harsher chemical-physical conditions and negligible methane oxidation were detected. The pmoA gene libraries from the most active site FAV2 pointed out a high diversity of gammaproteobacterial methanotrophs distantly related to Methylococcus/Methylothermus genera and the presence of the newly discovered acido-thermophilic methanotrophs

  17. High rates of nitrogen cycling in volcanic soils from Chilean grasslands.

    PubMed

    Dixon, E R; Cardenas, L; Alfaro, M; Salazar, F; Hatch, D J

    2011-06-15

    There are over one million hectares of pasture in Chile, and 80% and 50% of the country's milk and meat comes from 72% of this area, situated in the lake region of southern Chile. The soils are volcanic and a major characteristic is that they have very high organic matter (OM) contents with the potential to support plant growth with only moderate levels of added nitrogen (N). To understand better the potential fertility of these soils in order to maximise production and minimise losses of N, we undertook studies using the stable isotope of N ((15)N) to resolve the rates of the main internal N cycling processes in three soils representing the two main volcanic soil types: Osorno and Chiloé (Andisol) and Cudico (Ultisol). We also assessed the longer-term potential of these soils to sustain N release using anaerobic incubation. Gross rates (µg N g(-1) day(-1)) of mineralisation were 27.9, 27.1 and 15.5 and rates of immobilisation were 5.9, 12.0 and 6.3 for Osorno, Chiloé and Cudico, respectively, implying high rates of net mineralisation in these soils. This was confirmed by anaerobic incubation which gave potential seasonal net mineralisation indices of 1225, 1059 and 450 kg N ha(-1) in the top 10 cm soil layers of the three soils. However, plant production may still benefit from added N, as the release of N from organic sources may not be closely synchronised with crop demand. The low rates of nitrification that we found with these acidic soils suggest that the more mobile N (viz. nitrate-N) would be in limited supply and plants would have to compete for the less mobile ammonium-N with the soil microbial biomass. Nitrogen was mineralised in appreciable amounts even down to 60 cm depth, so that leaching could become significant, particularly if the soils were limed, which could enhance nitrification and N mobility through the soil profile. PMID:21594925

  18. Linking trace metals and agricultural land use in volcanic soils--a multivariate approach.

    PubMed

    Parelho, C; Rodrigues, A S; Cruz, J V; Garcia, P

    2014-10-15

    The concern about the environmental impacts caused by agriculture intensification is growing as large amounts of nutrients and contaminants are introduced into soil ecosystems. Volcanic soils are unique naturally fertile resources extensively used for agricultural purposes, with particular physical and chemical properties that may result in possible accumulation of toxic substances, such as metals. Within this particular geological context, the present study aims to evaluate the impact of different agricultural systems (conventional, traditional and organic) in trace metal (TM) soil pollution and define the tracers for each one. Physicochemical properties and TM contents in agricultural topsoils were determined. Enrichment Factors (EF) were calculated to distinguish geogenic and anthropogenic contribution to TM contents in agricultural soils. An ensemble of multivariate statistical analyses (PCA and FDA) was performed to reduce the multidimensional space of variables and samples, thus defining a set of TM as tracers of distinct agricultural farming systems. Results show that agricultural soils have low organic matter content (<5%) compared to reference soil (>30%); in addition, electric conductivity in conventional farming soils is higher (262.3 ± 162.6 μS cm(-1)) while pH is lower (5.8 ± 0.3). Regarding metal inputs, V, Ba and Hg soil contents are mainly of geogenic origin, while Li, P, K, Cr, Mn, Ni, Cu, Zn, As, Mo, Cd and Pb result primarily from anthropogenic inputs. Li revealed to be a tracer of agricultural pollution in conventional farming soils, whereas V allowed the discrimination of traditional farming soils. This study points to agriculture as a diffuse source of anthropogenic TM soil pollution and is the first step to identify priority chemicals affecting agricultural Andosols. PMID:25093299

  19. Organic matter protection as affected by the mineral soil matrix: allophanic vs. non-allophanic volcanic ash soils

    NASA Astrophysics Data System (ADS)

    Nierop, K. G. J.; Kaal, J.; Jansen, B.; Naafs, D. F. W.

    2009-04-01

    Volcanic ash soils (Andosols) contain the largest amounts of organic carbon of all mineral soil types. Chemical (complexes of organic matter with allophane, Al/Fe) and physical (aggregation) mechanisms are protecting the carbon from decomposition. While allophanic Andosols are dominated by short range order minerals such as allophane, imogolite and ferrihydrite, organic matter-Al/Fe complexes dominate non-allophanic Andosols. Consequently, chemical interactions between the mineral soil matrix and organic matter differ between these two soil types. This difference could potentially lead to different organic matter compositions. In this study, the organic matter of Ah horizons of an allophanic Andosol with a non-allophanic Andosol from Madeira Island is compared using analytical pyrolysis. Both volcanic soil types showed a relative decrease of lignin-derived pyrolysis products with depth, but this decrease was more pronounced in the allophanic Andosol. Polysaccharides were more abundant in the allophanic Ah horizon, particularly at lower depth, and this was also the case for the non-plant-derived N-containing polysaccharide chitin. Most likely, these biopolymers are adsorbed onto short range order minerals such as allophane and therefore were better protected in the allophanic Andosol. In addition, the higher chitin contents combined with the more pronounced lignin degradation suggests a higher fungal activity. Aliphatic pyrolysis products (n-alkenes/n-alkanes, fatty acids) were relatively more enriched in the non-allophanic Andosol. Lower microbial activity caused by the more acidic pH and higher levels of (toxic) aluminium are the most plausible reasons for the accumulation of these compounds in the non-allophanic Andosol. Although the allophanic and non-allophanic Andosol resembled each other in containing biopolymer groups of the same orders of magnitudes, in particular the contents of chitin and aliphatic compounds were distinctly affected by the differences in

  20. Magnesium retention on the soil exchange complex controlling Mg isotope variations in soils, soil solutions and vegetation in volcanic soils, Iceland

    NASA Astrophysics Data System (ADS)

    Opfergelt, S.; Burton, K. W.; Georg, R. B.; West, A. J.; Guicharnaud, R. A.; Sigfusson, B.; Siebert, C.; Gislason, S. R.; Halliday, A. N.

    2014-01-01

    Understanding the biogeochemical cycle of magnesium (Mg) is not only crucial for terrestrial ecology, as this element is a key nutrient for plants, but also for quantifying chemical weathering fluxes of Mg and associated atmospheric CO2 consumption, requiring distinction of biotic from abiotic contributions to Mg fluxes exported to the hydrosphere. Here, Mg isotope compositions are reported for parent basalt, bulk soils, clay fractions, exchangeable Mg, seasonal soil solutions, and vegetation for five types of volcanic soils in Iceland in order to improve the understanding of sources and processes controlling Mg supply to vegetation and export to the hydrosphere. Bulk soils (δ26Mg = -0.40 ± 0.11‰) are isotopically similar to the parent basalt (δ26Mg = -0.31‰), whereas clay fractions (δ26Mg = -0.62 ± 0.12‰), exchangeable Mg (δ26Mg = -0.75 ± 0.14‰), and soil solutions (δ26Mg = -0.89 ± 0.16‰) are all isotopically lighter than the basalt. These compositions can be explained by a combination of mixing and isotope fractionation processes on the soil exchange complex. Successive adsorption-desorption of heavy Mg isotopes leads to the preferential loss of heavy Mg from the soil profile, leaving soils with light Mg isotope compositions relative to the parent basalt. Additionally, external contributions from sea spray and organic matter decomposition result in a mixture of Mg sources on the soil exchange complex. Vegetation preferentially takes up heavy Mg from the soil exchange complex (Δ26Mgplant-exch = +0.50 ± 0.09‰), and changes in δ26Mg in vegetation reflect changes in bioavailable Mg sources in soils. This study highlights the major role of Mg retention on the soil exchange complex amongst the factors controlling Mg isotope variations in soils and soil solutions, and demonstrates that Mg isotopes provide a valuable tool for monitoring biotic and abiotic contributions of Mg that is bioavailable for plants and is exported to the hydrosphere.

  1. Iron Oxides from Volcanic Soils as Potential Catalysts in the Water Gas Shift Reaction

    SciTech Connect

    Pizarro, C.; Escudey, M.; Moya, S.A.; Fabris, J.D.

    2005-04-26

    This study was focused on changes of the iron oxide mineralogy with temperature of two Chilean soils (Andisol and Ultisol) derived from volcanic materials and their use as iron-based catalysts in the water gas shift reaction (WGSR). Ultisol materials produced about twice as much hydrogen than did those from Andisol upon WGSR, but in both cases hydrogen yielding increased as the heating temperature of the soil materials increased from 124 deg. C to 500 deg. C. The room temperature Moessbauer spectra showed an increase of the relative proportion of the magnetically ordered components as temperature increased. Higher heating temperature produced a negative effect on the catalytic activity, whereas the organic matter destruction led to a positive effect, due to an increasing exposition of the iron oxide surfaces; heating the soil sample at 600 deg. C induced changes on the iron oxide mineralogy with a significant decrease of the catalytic activity.

  2. Iron Oxides from Volcanic Soils as Potential Catalysts in the Water Gas Shift Reaction

    NASA Astrophysics Data System (ADS)

    Pizarro, C.; Escudey, M.; Moya, S. A.; Fabris, J. D.

    2005-04-01

    This study was focused on changes of the iron oxide mineralogy with temperature of two Chilean soils (Andisol and Ultisol) derived from volcanic materials and their use as iron-based catalysts in the water gas shift reaction (WGSR). Ultisol materials produced about twice as much hydrogen than did those from Andisol upon WGSR, but in both cases hydrogen yielding increased as the heating temperature of the soil materials increased from 124°C to 500°C. The room temperature Mössbauer spectra showed an increase of the relative proportion of the magnetically ordered components as temperature increased. Higher heating temperature produced a negative effect on the catalytic activity, whereas the organic matter destruction led to a positive effect, due to an increasing exposition of the iron oxide surfaces; heating the soil sample at 600 °C induced changes on the iron oxide mineralogy with a significant decrease of the catalytic activity.

  3. Methanotrophic activity and diversity of methanotrophs in volcanic geothermal soils at Pantelleria (Italy)

    NASA Astrophysics Data System (ADS)

    Gagliano, A. L.; D'Alessandro, W.; Tagliavia, M.; Parello, F.; Quatrini, P.

    2014-10-01

    Volcanic and geothermal systems emit endogenous gases by widespread degassing from soils, including CH4, a greenhouse gas twenty-five times as potent as CO2. Recently, it has been demonstrated that volcanic or geothermal soils are not only a source of methane, but are also sites of methanotrophic activity. Methanotrophs are able to consume 10-40 Tg of CH4 a-1 and to trap more than 50% of the methane degassing through the soils. We report on methane microbial oxidation in the geothermally most active site of Pantelleria (Italy), Favara Grande, whose total methane emission was previously estimated at about 2.5 Mg a-1 (t a-1). Laboratory incubation experiments with three top-soil samples from Favara Grande indicated methane consumption values of up to 59.2 nmol g-1 soil d.w. h-1. One of the three sites, FAV2, where the highest oxidation rate was detected, was further analysed on a vertical soil profile, the maximum methane consumption was measured in the top-soil layer, and values greater than 6.23 nmol g-1 h-1 were still detected up to a depth of 13 cm. The highest consumption rate was measured at 37 °C, but a still detectable consumption at 80 °C (> 1.25 nmol g-1 h-1) was recorded. The soil total DNA extracted from the three samples was probed by Polymerase Chain Reaction (PCR) using standard proteobacterial primers and newly designed verrucomicrobial primers, targeting the unique methane monooxygenase gene pmoA; the presence of methanotrophs was detected at sites FAV2 and FAV3, but not at FAV1, where harsher chemical-physical conditions and negligible methane oxidation were detected. The pmoA gene libraries from the most active site (FAV2) pointed to a high diversity of gammaproteobacterial methanotrophs, distantly related to Methylocaldum-Metylococcus genera, and the presence of the newly discovered acido-thermophilic Verrucomicrobia methanotrophs. Alphaproteobacteria of the genus Methylocystis were isolated from enrichment cultures under a methane

  4. Influence of management practices on C stabilization pathways in agricultural volcanic ash soils (Canary Islands, Spain)

    NASA Astrophysics Data System (ADS)

    Hernandez, Zulimar; María Álvarez, Ana; Carral, Pilar; de Figueiredo, Tomas; Almendros, Gonzalo

    2014-05-01

    Although C stabilization mechanisms in agricultural soils are still controversial [1], a series of overlapped pathways has been suggested [2] such as: i) insolubilization of low molecular weight precursors of soil organic matter (SOM) with reactive minerals through physical and chemical bonding, ii) selective accumulation of biosynthetic substances which are recalcitrant because of its inherent chemical composition, and iii) preservation and furter diagenetic transformation of particulate SOM entrapped within resistant microaggregates, where diffusion of soil enzymes is largely hampered. In some environments where carbohydrate and N compounds are not readily biodegraded, e.g., with water saturated micropores, an ill-known C stabilization pathway may involve the formation of Maillard's reaction products [3]. In all cases, these pathways converge in the formation of recalcitrant macromolecular substances, sharing several properties with the humic acid (HA) fraction [4]. In template forests, the selective preservation and further microbial reworking of plant biomass has been identified as a prevailing mechanism in the accumulation of recalcitrant SOM forms [5]. However, in volcanic ash soils with intense organomineral interactions, condensation reactions of low molecular weight precursors with short-range minerals may be the main mechanism [6]. In order to shed some light about the effect of agricultural management on soil C stabilization processes on volcanic ash soils, the chemical composition of HA and some structural proxies of SOM informing on its origin and potential resistance to biodegradation, were examined in 30 soils from Canary Islands (Spain) by visible, infrared (IR) and 13C nuclear magnetic resonance (NMR) spectroscopies, elementary analysis and pyrolytic techniques. The results of multivariate treatments, suggested at least three simultaneous C stabilization biogeochemical trends: i) diagenetic alteration of plant biomacromolecules in soils receiving

  5. Ammonia emissions from urea application to permanent pasture on a volcanic soil

    NASA Astrophysics Data System (ADS)

    Salazar, F.; Martínez-Lagos, J.; Alfaro, M.; Misselbrook, T.

    2012-12-01

    Agriculture is the largest source of ammonia (NH3) emission to the atmosphere, deriving mainly from livestock urine and manures, but fertilizer applications to pastures and crops also represent an important source. In Chile, where agriculture and cattle production are important activities (accounting for 4.5% of GDP along with the forestry sector), there are very few published data regarding NH3 emissions from pasture and crop fertilization. This study aimed to provide the first empirical field data for Chile on N losses due to NH3 volatilization following urea application to permanent pasture on a volcanic soil and to assess the influence of environmental conditions on emissions. Four field experiments were carried out on a volcanic acid soil using the micrometeorological integrated horizontal flux (IHF) mass balance method. Measurements were made in winter 2005 and 2007, and spring 2007 and 2008 following urea N fertilization to a permanent pasture at a rate equivalent to 100 kg N ha-1. Cumulative NH3 emissions over the measurement period were 1.4 and 7.7 kg N ha-1 for winter applications, and 12.2 and 26.7 kg N ha-1 for spring dressings. These N losses due to NH3 volatilization are within the range of emissions reported elsewhere. Consideration of urea application timing in Chile, with regards to weather and soil conditions, could have important consequences on minimising potential N losses via volatilization with associated financial benefits to farmers.

  6. Influence of Organic Matter on the Iron Oxide Mineralogy of Volcanic Soils

    NASA Astrophysics Data System (ADS)

    Pizarro, C.; Escudey, M.; Fabris, J. D.

    2003-06-01

    Samples of soils developing on volcanic materials that represent about 70% of the agriculture land area in Chile were studied by chemical methods, powder X-ray diffractometry (XRD) and Mössbauer spectroscopy. The soil samples were collected from native areas of Ultisols, Andisols, and Andisols presenting seasonal cycles of poor drainage, at depths between 0-15 cm and 15-30 cm from the top of the profile. The degree of crystallinity of iron oxides was evaluated from the ratio of amounts of Fe extracted with oxalate-oxalic acid (FeOX) and with bicarbonate-citrate-dithionite mixtures (FeDBC), FeOX/FeDBC. Results show that the specific saturation magnetization of soils and crystallinity of iron-rich minerals increase with decreasing organic matter contents of soils. From XRD and Mössbauer data, ferrihydrite (ideal formula, Fe5HO8ṡ4H2O) could be the precursor either of the soil magnetite (Fe3O4) or hematite (αFe2O3). Older soils were found to be in an intermediate stage regarding the transformation of magnetite to maghemite (γFe2O3).

  7. The Natural Terrestrial Carbon Sequestration Potential of Rocky Mountain Soils Derived From Volcanic Bedrock

    NASA Astrophysics Data System (ADS)

    Yager, D. B.; Burchell, A.; Johnson, R. H.

    2008-12-01

    The possible economic and environmental ramifications of climate change have stimulated a range of atmospheric carbon mitigation actions, as well as, studies to understand and quantify potential carbon sinks. However, current carbon management strategies for reducing atmospheric emissions underestimate a critical component. Soils represent between 18 - 30% of the terrestrial carbon sink needed to prevent atmospheric doubling of CO2 by 2050 and a crucial element in mitigating climate change, natural terrestrial sequestration (NTS), is required. NTS includes all naturally occurring, cumulative, biologic and geologic processes that either remove CO2 from the atmosphere or prevent net CO2 emissions through photosynthesis and microbial fixation, soil formation, weathering and adsorption or chemical reactions involving principally alumino- ferromagnesium minerals, volcanic glass and clays. Additionally, NTS supports ecosystem services by improving soil productivity, moisture retention, water purification and reducing erosion. Thus, 'global climate triage' must include the protection of high NTS areas, purposeful enhancement of NTS processes and reclamation of disturbed and mined lands. To better understand NTS, we analyzed soil-cores from Colorado, Rocky Mountain Cordillera sites. North-facing, high-plains to alpine sites in non-wetland environments were selected to represent temperate soils that may be less susceptible to carbon pool declines due to global warming than soils in warmer regions. Undisturbed soils sampled have 2 to 6 times greater total organic soil carbon (TOSC) than global TOSC averages (4 - 5 Wt. %). Forest soils derived from weathering of intermediate to mafic volcanic bedrock have the highest C (34.15 Wt. %), C:N (43) and arylsulfatase (ave. 278, high 461 μg p-nitrophenol/g/h). Intermediate TOSC was identified in soils derived from Cretaceous shale (7.2 Wt. %) and Precambrian, felsic gneiss (6.2 Wt. %). Unreclaimed mine-sites have the lowest C (0

  8. Relations among soil radon, environmental parameters, volcanic and seismic events at Mt. Etna (Italy)

    NASA Astrophysics Data System (ADS)

    Giammanco, S.; Ferrera, E.; Cannata, A.; Montalto, P.; Neri, M.

    2013-12-01

    From November 2009 to April 2011 soil radon activity was continuously monitored using a Barasol probe located on the upper NE flank of Mt. Etna volcano (Italy), close both to the Piano Provenzana fault and to the NE-Rift. Seismic, volcanological and radon data were analysed together with data on environmental parameters, such as air and soil temperature, barometric pressure, snow and rain fall. In order to find possible correlations among the above parameters, and hence to reveal possible anomalous trends in the radon time-series, we used different statistical methods: i) multivariate linear regression; ii) cross-correlation; iii) coherence analysis through wavelet transform. Multivariate regression indicated a modest influence on soil radon from environmental parameters (R2 = 0.31). When using 100-day time windows, the R2 values showed wide variations in time, reaching their maxima (~0.63-0.66) during summer. Cross-correlation analysis over 100-day moving averages showed that, similar to multivariate linear regression analysis, the summer period was characterised by the best correlation between radon data and environmental parameters. Lastly, the wavelet coherence analysis allowed a multi-resolution coherence analysis of the time series acquired. This approach allowed to study the relations among different signals either in the time or in the frequency domain. It confirmed the results of the previous methods, but also allowed to recognize correlations between radon and environmental parameters at different observation scales (e.g., radon activity changed during strong precipitations, but also during anomalous variations of soil temperature uncorrelated with seasonal fluctuations). Using the above analysis, two periods were recognized when radon variations were significantly correlated with marked soil temperature changes and also with local seismic or volcanic activity. This allowed to produce two different physical models of soil gas transport that explain the

  9. Sulfate adsorption and surface precipitation on a volcanic ash soil (allophanic andisol).

    PubMed

    Ishiguro, Munehide; Makino, Tomoyuki; Hattori, Yasunobu

    2006-08-15

    Sulfate strongly adsorbs on metal oxides and soils with variable charges. However, its surface precipitation has not been clearly evaluated and its adsorption mechanism has been in dispute. In the present study, an allophanic andisol, a typical volcanic ash soil having both negative and positive variable charges, was used to identify the adsorption mechanism of sulfate. Sulfate adsorption isotherms were obtained by a batch method at pH values of 4, 5, 6, and 7 in a wide range of concentrations in an Na-H-SO(4)-OH system. Theoretical isotherms were applied to the measured values for the evaluation. The surface precipitation was detected by the measured adsorption isotherms, and the BET isotherm confirmed the presence of multilayer adsorption. Stronger and weaker adsorption sites were suggested by using the Langmuir isotherm for the monolayer adsorption. The adsorption energies obtained from the Langmuir equation and recent spectroscopic analysis suggested that the stronger adsorption corresponded to an inner-sphere surface complex and that the weaker adsorption corresponded to outer-sphere surface complexation. The BET and Langmuir equations showed three types of adsorption mechanisms for the sulfate adsorption on the soil. PMID:16750540

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

    NASA Astrophysics Data System (ADS)

    Ersoy, Hakan; Karsli, Melek Betül; Çellek, Seda; Kul, Bilgehan; Baykan, İdris; Parsons, Robert L.

    2013-12-01

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

  11. Laboratory scale of rainfall's pattern and threshold in volcanic soil slope failure

    NASA Astrophysics Data System (ADS)

    Kartiko, R. D.; Sadisun, I. A.; Tohari, A.; Sumintadiredja, P.

    2016-05-01

    Relationship between rainfall pattern, threshold and landslide process have widely developed. However, real-time observation in real landslide event is time consuming and has high degree of uncertainty. Therefore more analysis is usually developed in regional data scale with correlation between regional rainfall dataset and landslide inventory mapping. In this study, another approach is developed with a physical laboratory scale model. This research developed correlation between simulated rainfall pattern with mechanism and process of landslide. Rainfall with specific intensity and duration are given in residual volcanic soil in laboratory scale. Rainfall threshold observed between laboratory and regional model is highly correlated. There also occurred clear relationships between intensity, duration, antecedent rainfall, with rainfall's initiation and morphology.

  12. Impacts of Dust on Tropical Volcanic Soil Formation: Insights from Strontium and Uranium-Series Isotopes in Soils from Basse-Terre Island, French Guadeloupe

    NASA Astrophysics Data System (ADS)

    Pereyra, Y.; Ma, L.; Sak, P. B.; Gaillardet, J.; Buss, H. L.; Brantley, S. L.

    2015-12-01

    Dust inputs play an important role in soil formation, especially for thick soils developed on tropical volcanic islands. In these regions, soils are highly depleted due to intensive chemical weathering, and mineral nutrients from dusts have been known to be important in sustaining soil fertility and productivity. Tropical volcanic soils are an ideal system to study the impacts of dust inputs on the ecosystem. Sr and U-series isotopes are excellent tracers to identify sources of materials in an open system if the end-members have distinctive isotope signatures. These two isotope systems are particularly useful to trace the origin of atmospheric inputs into soils and to determine rates and timescales of soil formation. This study analyzes major elemental concentrations, Sr and U-series isotope ratios in highly depleted soils in the tropical volcanic island of Basse-Terre in French Guadeloupe to determine atmospheric input sources and identify key soil formation processes. We focus on three soil profiles (8 to 12 m thick) from the Bras-David, Moustique Petit-Bourg, and Deshaies watersheds; and on the adjacent rivers to these sites. Results have shown a significant depletion of U, Sr, and major elements in the deep profile (12 to 4 m) attributed to rapid chemical weathering. The top soil profiles (4 m to the surface) all show addition of elements such as Ca, Mg, U, and Sr due to atmospheric dust. More importantly, the topsoil profiles have distinct Sr and U-series isotope compositions from the deep soils. Sr and U-series isotope ratios of the top soils and sequential extraction fractions confirm that the sources of the dust are from the Saharan dessert, through long distance transport from Africa to the Caribbean region across the Atlantic Ocean. During the transport, some dust isotope signatures may also have been modified by local volcanic ashes and marine aerosols. Our study highlights that dusts and marine aerosols play important roles in element cycles and

  13. Soil gas radon and volcanic activity at El Hierro (Canary Islands) before and after the 2011-2012 submarine eruption

    NASA Astrophysics Data System (ADS)

    Barrancos, J.; Padilla, G.; Hernandez Perez, P. A.; Padron, E.; Perez, N.; Melian Rodriguez, G.; Nolasco, D.; Dionis, S.; Rodriguez, F.; Calvo, D.; Hernandez, I.

    2012-12-01

    El Hierro is the youngest and southernmost island of the Canarian archipelago and represents the summit of a volcanic shield elevating from the surrounding seafloor at depth of 4000 m to up to 1501 m above sea level. The island is believed to be near the present hotspot location in the Canaries with the oldest subaerial rocks dated at 1.12 Ma. The subaerial parts of the El Hierro rift zones (NE, NW and S Ridges) are characterized by tightly aligned dyke complexes with clusters of cinder cones as their surface expressions. Since July 16, 2011, an anomalous seismicity at El Hierro Island was recorded by IGN seismic network. Volcanic tremor started at 05:15 hours on October 10, followed on the afternoon of October 12 by a green discolouration of seawater, strong bubbling and degassing indicating the initial stage of submarine volcanic eruption at approximately 2 km off the coast of La Restinga, El Hierro. Soil gas 222Rn and 220Rn activities were continuously measured during the period of the recent volcanic unrest occurred at El Hierro, at two different geochemical stations, HIE02 and HIE03. Significant increases in soil 222Rn activity and 222Rn/220Rn ratio from the soil were observed at both stations prior the submarine eruption off the coast of El Hierro, showing the highest increases before the eruption onset and the occurrence of the strongest seismic event (M=4.6). A statistical analysis showed that the long-term trend of the filtered data corresponded closely to the seismic energy released during the volcanic unrest. The observed increases of 222Rn are related to the rock fracturing processes (seismic activity) and the magmatic CO2 outflow increase, as observed in HIE03 station. Under these results, we find that continuous soil radon studies are important for evaluating the volcanic activity of El Hierro and they demonstrate the potential of applying continuous monitoring of soil radon to improve and optimize the detection of early warning signals of future

  14. Ammonia oxidizers are pioneer microorganisms in the colonization of new acidic volcanic soils from South of Chile.

    PubMed

    Hernández, Marcela; Dumont, Marc G; Calabi, Marcela; Basualto, Daniel; Conrad, Ralf

    2014-02-01

    Ammonia oxidation, performed by specialized microorganisms belonging to the Bacteria and Archaea, is the first and most limiting step of soil nitrification. Nitrification has not yet been examined in young volcanic soils. The aim of the present work was to evaluate the abundance and diversity of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in acidic volcanic soils (andisols) of different defined ages to determine their relative contribution to nitrification and soil colonization. Soil was collected from three vegetated sites on Llaima Volcano (Chile) recolonized after lava eruptions in 1640, 1751 and 1957. Quantitative polymerase chain reaction, terminal restriction fragment length polymorphism and clone sequence analyses of the amoA gene were performed for the AOA and AOB communities. All soils showed high nitrification potentials, but they were highest in the younger soils. Archaeal amoA genes outnumbered bacterial amoA genes at all sites, and AOA abundances were found to be proportional to the nitrification potentials. Sequencing indicated the presence of AOA related to Nitrososphaera and Nitrosotalea, and AOB related primarily to Nitrosospira and sporadically to Nitrosomonas. The study showed that both AOA and AOB are early colonizers of andisols, but that AOA outnumber AOB and play an important role in nitrification. PMID:24596264

  15. Microbial life in volcanic/geothermal areas: how soil geochemistry shapes microbial communities

    NASA Astrophysics Data System (ADS)

    Gagliano, Antonina Lisa; D'Alessandro, Walter; Franzetti, Andrea; Parello, Francesco; Tagliavia, Marcello; Quatrini, Paola

    2015-04-01

    Extreme environments, such as volcanic/geothermal areas, are sites of complex interactions between geosphere and biosphere. Although biotic and abiotic components are strictly related, they were separately studied for long time. Nowadays, innovative and interdisciplinary approaches are available to explore microbial life thriving in these environments. Pantelleria island (Italy) hosts a high enthalpy geothermal system characterized by high CH4 and low H2S fluxes. Two selected sites, FAV1 and FAV2, located at Favara Grande, the main exhalative area of the island, show similar physical conditions with a surface temperature close to 60° C and a soil gas composition enriched in CH4, H2 and CO2. FAV1 soil is characterized by harsher conditions (pH 3.4 and 12% of H2O content); conversely, milder conditions were recorded at site FAV2 (pH 5.8 and 4% of H2O content). High methanotrophic activity (59.2 nmol g-1 h-1) and wide diversity of methanotrophic bacteria were preliminary detected at FAV2, while no activity was detected at FAV1(1). Our aim was to investigate how the soil microbial communities of these two close geothermal sites at Pantelleria island respond to different geochemical conditions. Bacterial and Archaeal communities of the sites were investigated by MiSeq Illumina sequencing of hypervariable regions of the 16S rRNA gene. More than 33,000 reads were obtained for Bacteria and Archaea from soil samples of the two sites. At FAV1 99% of the bacterial sequences were assigned to four main phyla (Proteobacteria, Firmicutes, Actinobacteria and Chloroflexi). FAV2 sequences were distributed in the same phyla with the exception of Chloroflexi that was represented below 1%. Results indicate a high abundance of thermo-acidophilic chemolithotrophs in site FAV1 dominated by Acidithiobacillus ferrooxidans (25%), Nitrosococcus halophilus (10%), Alicyclobacillus spp. (7%) and the rare species Ktedonobacter racemifer (11%). The bacterial community at FAV2 soil is dominated by

  16. A preliminary evaluation of volcanic rock powder for application in agriculture as soil a remineralizer.

    PubMed

    Ramos, Claudete G; Querol, Xavier; Oliveira, Marcos L S; Pires, Karen; Kautzmann, Rubens M; Oliveira, Luis F S

    2015-04-15

    Mineralogical and geochemical characteristics of volcanic rock residue, from a crushing plant in the Nova Prata Mining District, State of Rio Grande do Sul (RS), Brazil, in this work named rock powder, were investigated in view of its potential application as soil ammendment in agriculture. Abaut 52,400 m(3) of mining waste is generated annually in the city of Nova Prata without a proper disposal. The nutrients potentially available to plants were evaluated through leaching laboratory tests. Nutrient leaching tests were performed in Milli-Q water; citric acid solution 1% and 2% (AC); and oxalic acid solution 1% and 5% (AO). The bulk and leachable contents of 57 elements were determined by inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Mining waste were made up by CaO, K2O, SiO2, Al2O3, Fe2O3, and P2O5. The analysis by X-ray diffraction (XRD) showed the major occurence of quartz, anorthite, cristobalite, sanidine, and augite. The water leachable concentrations of all elements studied were lower than 1.0mg/kg, indicating their low solubility. Leaching tests in acidic media yield larger leachable fractions for all elements being studied are in the leachate of the AO 1%. These date usefulness of volcanic rock powder as potential natural fertilizer in agriculture in the mining district in Nova Prata, Rio Grande do Sul, Brazil to reduce the use of chemical fertilizers. PMID:25638652

  17. Radon levels in groundwaters and natural radioactivity in soils of the volcanic region of La Garrotxa, Spain.

    PubMed

    Moreno, V; Bach, J; Baixeras, C; Font, Ll

    2014-02-01

    Groundwater radon level and soil radionuclide concentration have been measured in the volcanic region of La Garrotxa (Catalonia, Spain) to further research on the origin and dynamics of high radon levels over volcanic materials found in this region. Water samples from different aquifers have been collected from wells and springs and the water radon levels obtained have been lower than 30 Bq l(-1). Soil samples have been collected from different geological formations (volcanic and non-volcanic), being Quaternary sedimentary deposits those that have presented the highest mean values of (40)K, (226)Ra and (232)Th concentrations (448 ± 70 Bq kg(-1), 35 ± 5 Bq kg(-1) and 38 ± 5 Bq kg(-1), respectively). Additionally, indoor/outdoor terrestrial radiation absorbed dose rate in air have been measured to better characterize the region from the radiological point of view. Terrestrial radiation absorbed dose rates measurement points have been chosen on the basis of geological and demographical considerations and the results obtained, from 27 to 91 nGy h(-1), show a clear relation with geological formation materials. The highest terrestrial gamma absorbed dose rate is observed over Quaternary sedimentary deposits as well. All these results help to better understand previous surveys related with indoor and outdoor radon levels and to reinforce the hypotheses of a radon transport through the fissure network. PMID:24239577

  18. Impact of river overflowing on trace element contamination of volcanic soils in south Italy: part I. Trace element speciation in relation to soil properties.

    PubMed

    Adamo, P; Zampella, M; Gianfreda, L; Renella, G; Rutigliano, F A; Terribile, F

    2006-11-01

    Volcanic soils affected by different numbers of polluted river flooding events were investigated. Chromium and Cu were the major soil contaminants. Nickel, Fe, Zn and Mn total content never exceeded the Italian mandatory limits. The distribution of Cr and Cu total contents among studied soils indicated that only Cr contamination was related to overflowing events. In polluted soils, sequential chemical extractions revealed a preferential association of Cr and Cu with organic forms. A progressive Cr insolubilization with ageing was observed. Significant amounts of Cr and Cu were extracted by NH(4)-oxalate, suggesting metals association with short-range-order aluminosilicates and organo-mineral complexes. Possible methodological drawbacks in the use of the EU-BCR chemical speciation protocol on volcanic soils are discussed. Micromorphology and SEM/WDS analyses revealed Cr and Cu enriched silt and clay coatings in surface and subsurface soil horizons, suggesting a transfer of metal-rich sediments along the soil pore network with water movement. PMID:16777304

  19. Susceptibility of volcanic ash-influenced soil in Northern Idaho to mechanical compaction. Forest Service research note

    SciTech Connect

    Page-Dumroese, D.S.

    1993-02-01

    Timber harvesting and mechanical site preparation can reduce site productivity if they excessively disturb or compact the soil. Volcanic ash-influenced soils with low undisturbed bulk densities and rock content are particularly susceptible. The study evaluates the effects of harvesting and site preparation on changes in the bulk density of ash-influenced forest soils in northern Idaho. Three different levels of surface organic matter were studied. Soil samples were taken before and after harvesting to determine the extent and depth of compaction. Soil bulk densities increased significantly after extensive compaction from site preparation, especially when little logging slash and surface organic matter were left on the soil surface. As site preparation intensity increased, bulk density increased significantly at greater depths in the soil profile. Although ash-influenced soils have naturally low bulk densities, they can easily be compacted to levels that limit growth. The experimental site has been designated as part of the Forest Service's national long-term site productivity study into the impacts of organic matter depletion and soil compaction on stand development.

  20. The interaction between parent material, climate and volcanism as the major soil forming factor in the Ecuadorian high Andes region

    NASA Astrophysics Data System (ADS)

    Buytaert, W.; Duyck, H.; Dercon, G.; Deckers, J.; Wyseure, G.

    2003-04-01

    The high Andes region of Ecuador and Colombia (>3500m a.s.l.) is covered by the so-called páramo ecosystem, characterised by a cold climate, a typical grass or small shrub vegetation and volcanic soils. Soil profiles of the paramo in the Austro Ecuatoriano, South Ecuador, were studied in order to reveal genetic relationships with geology, volcanic ash deposits, climate and land use. A gradual diminuation of Andic properties was found, related to the distance of the pedon to the active volcanoes of the Northern Volcanic Zone of the Andes. Pedons in the north of the region, closer to these volcanoes (Sangay, Tungurahua) are classified as non-allophanic Histic Andosols. The influence of the vicinity of the volcanoes leads to a higher oxalate extractable aluminium and iron. The genesis of the Andosols seems to be strongly related to the presence and thickness of volcanic ash depositions. The limit of these depositions is situated south of the city of Cuenca. Pedons further to the south are classified as Histosols. However, they also have clear Andic properties. Several differences in chemical properties between the Western and Eastern cordilleras where found, that are most probable related with a difference in mother material, and maybe also a different climatic regime. Correlation of the chemical properties with land use reveals that no chemical differences can be found that are invoked by occupying natural Andosols for agricultural purposes, within the first five years of cultivation. At last, the conclusions were used to revisit the World Reference Base for Soil Resources in order to sharpen up differenciation between Andosols and Histosols.

  1. Distinct bacterial community structure of 3 tropical volcanic soils from banana plantations contaminated with chlordecone in Guadeloupe (French West Indies).

    PubMed

    Mercier, Anne; Dictor, Marie-Christine; Harris-Hellal, Jennifer; Breeze, Dominique; Mouvet, Christophe

    2013-08-01

    In the French West Indies (FWI), the soil, andosols, ferralsols and nitisols, is highly polluted by chlordecone, although this organochlorine insecticide extensively applied to banana crops has been banned for 20years. This contamination has led to a major human health concern inducing the need for remediation of the contaminated soils. Work was conducted to help to evaluate the impact of remediation processes on the microbial communities from these soils. Microbial biomass was estimated after direct DNA extraction from three chlordecone-contaminated soils (an andosol, a ferralsol and a nitisol) and the bacterial community analyzed using t-RFLP. The FWI volcanic andosol was particularly recalcitrant to usual direct DNA extraction protocols hampering analysis of soil microbial communities until now, in contrast with the 2 other soils. For the first time, DNA was directly extracted from a FWI andosol based on yeast RNA addition at the lysis step. Differences in microbial biomass were thus observed between the 3 FWI soils. Moreover, the bacterial community structure was significantly distinct from each other's and related to soil physico-chemical characteristics. Interestingly, differences in bacterial diversity could not be exclusively attributed to the level of chlordecone contamination. PMID:23706897

  2. Influences of quaternary climatic changes on processes of soil development on desert loess deposits of the Cima volcanic field, California

    USGS Publications Warehouse

    McFadden, L.D.; Wells, S.G.; Dohrenwend, J.C.

    1986-01-01

    Soils formed in loess are evidence of both relict and buried landscapes developed on Pliocene-to-latest Pleistocene basalt flows of the Cima volcanic field in the eastern Mojave Desert, California. The characteristics of these soils change systematically and as functions of the age and surface morphology of the lava flow. Four distinct phases of soil development are recognized: phase 1 - weakly developed soils on flows less than 0.18 M.y. old; phase 2 - strongly developed soils with thick argillic horizons on 0.18 - 0.7 M.y. old flows; phase 3 - strongly developed soils with truncated argillic horizons massively impregnated by carbonate on 0.7 to 1.1 M.y. old flows; and phase 4 - degraded soils with petrocalcic rubble on Pliocene flows. A critical aspect of the development of stage 1 soils is the evolution of a vesicular A horizon which profoundly affects the infiltration characteristics of the loess parent materials. Laboratory studies show that secondary gypsum and possibly other salt accumulation probably occurred during the period of phase 1 soil development. Slight reddening of the interiors of peds from vesicular-A horizons of phase 1 soils and presence of weakly developed B horizons indicates a slight degree of in situ chemical alteration. However, clay and Fe oxide contents of these soils show that these constituents, as well as carbonates and soluble salts, are incorporated as eolian dust. In contrast to phase 1 soils, chemical and mineralogical analysis of argillic horizons of phase 2 soils indicate proportionally greater degrees of in-situ chemical alteration. These data, the abundant clay films, and the strong reddening in the thick argillic horizons suggest that phase 2 and phase 3 soils formed during long periods of time and periodically were subjected to leaching regimes more intense than those that now exist. Flow-age data and soil-stratigraphic evidence also indicate that several major loess-deposition events occurred during the past ??? 1.0 M

  3. Impact of river overflowing on trace element contamination of volcanic soils in south Italy: part II. Soil biological and biochemical properties in relation to trace element speciation.

    PubMed

    D'Ascoli, R; Rao, M A; Adamo, P; Renella, G; Landi, L; Rutigliano, F A; Terribile, F; Gianfreda, L

    2006-11-01

    The effect of heavy metal contamination on biological and biochemical properties of Italian volcanic soils was evaluated in a multidisciplinary study, involving pedoenvironmental, micromorphological, physical, chemical, biological and biochemical analyses. Soils affected by recurring river overflowing, with Cr(III)-contaminated water and sediments, and a non-flooded control soil were analysed for microbial biomass, total and active fungal mycelium, enzyme activities (i.e., FDA hydrolase, dehydrogenase, beta-glucosidase, urease, arylsulphatase, acid phosphatase) and bacterial diversity (DGGE characterisation). Biological and biochemical data were related with both total and selected fractions of Cr and Cu (the latter deriving from agricultural chemical products) as well as with total and extractable organic C. The growth and activity of soil microbial community were influenced by soil organic C content rather than Cu or Cr contents. In fact, positive correlations between all studied parameters and organic C content were found. On the contrary, negative correlations were observed only between total fungal mycelium, dehydrogenase, arylsulphatase and acid phosphatase activities and only one Cr fraction (the soluble, exchangeable and carbonate bound). However, total Cr content negatively affected the eubacterial diversity but it did not determine changes in soil activity, probably because of the redundancy of functions within species of soil microbial community. On the other hand, expressing biological and biochemical parameters per unit of total organic C, Cu pollution negatively influenced microbial biomass, fungal mycelium and several enzyme activities, confirming soil organic matter is able to mask the negative effects of Cu on microbial community. PMID:16406624

  4. Radiocarbon-based residence time estimates of soil organic carbon in a temperate forest: Case study for the density fractionation for Japanese volcanic ash soil

    NASA Astrophysics Data System (ADS)

    Kondo, Miyuki; Uchida, Masao; Shibata, Yasuyuki

    2010-04-01

    The world's soils store significantly more carbon than that is present in the atmosphere. To understand the distribution and dynamics of the soil organic carbon (SOC) reservoir and make a prediction about the response of the soil carbon pool to climate change, it is necessary to quantitatively constrain rate of soil carbon cycling. Following previous studies [24], we investigated the method for physically preparation of Japanese volcanic ash soil for the mean residence time (MRT) estimates in a cool-temperate deciduous forest in Japan, at one of Asia Flux monitoring sites. Sequentially isolated density fractions clearly differed in C contents and C/N ratios in soil surface (3-8 cm) and deep soil layer (38-43 cm). In soil surface layer, the light fractions (1.6-1.8, 1.6-1.8, 1.8-2.1 g cm -3) accounted for nearly 90% of SOC and their MRT ranged from 6 to 150 year. In deep layer, the 2.1-2.4 g cm -3 fraction accounted for more than 60% of SOC and its MRT was 3100 year. The lighter fractions (1.6-1.8, 1.8-2.1) comprised small portion of total SOC and were significantly slowly MRT (2038-2335 year), although it seems to consist of labile carbon.

  5. Soil microbial structure and function post-volcanic eruption on Kasatochi Island and regional controls on microbial heterogeneity

    NASA Astrophysics Data System (ADS)

    Zeglin, L. H.; Rainey, F.; Wang, B.; Waythomas, C.; Talbot, S. L.

    2013-12-01

    Microorganisms are abundant and diverse in soil and their integrated activity drives nutrient cycling on the ecosystem scale. Organic matter (OM) inputs from plant production support microbial heterotrophic life, and soil geochemistry constrains microbial activity and diversity. As vegetation and soil develops over time, these factors change, modifying the controls on microbial heterogeneity. Following a volcanic eruption, ash deposition creates new surfaces where both organismal growth and weathering processes are effectively reset. The trajectory of microbial community development following this disturbance depends on both organic matter accumulation and geochemical constraints. Also, dispersal of microbial cells to the sterile ash surface may determine microbial community succession. The Aleutian Islands (Alaska, USA) are a dynamic volcanic region, with active and dormant volcanoes distributed across the volcanic arc. One of these volcanoes, Kasatochi, erupted violently in August 2008, burying a small lush island in pryoclastic flows and fine ash. Since, plants and birds are beginning to re-establish on developing surfaces, including legacy soils exposed by rapid erosion of pyroclastic deposits, suggesting that recovery of microbial life is also proceeding. However, soil microbial diversity and function has not been examined on Kasatochi Island or across the greater Aleutian region. The project goal is to address these questions: How is soil microbial community structure and function developing following the Kasatochi eruption? What is the relative importance of dispersal, soil OM and geochemistry to microbial community heterogeneity across the Aleutians? Surface mineral soil (20-cm depth) samples were collected from Kasatochi Island in summer 2013, five years after the 2008 eruption, and from eight additional Aleutian islands. On Kasatochi, pryoclastic deposits, exposed legacy soils supporting regrowth of remnant dune wild-rye (Leymus mollis) and mesic meadow

  6. Long-term reactivity of lung and mediastinal lymph nodes following intratracheal instillation of sandy loam soil or Mount St. Helens volcanic ash

    SciTech Connect

    Sanders, C.L.; Rhoads, K.; Mahaffey, J.A.

    1983-01-01

    The effects of Ritzville sandy loam soil and Mount St. Helens volcanic ash particles on the lung and mediastinal lymph nodes of Fischer rats were studied about 400 days after intratracheal instillation. A total of 22 or 77 mg of soil or ash was given in two or seven equally divided, consecutive, weekly intervals as a suspension in 0.5 ml saline. Significantly elevated levels of lipid-phosphorus and protein were found in lung lavages of rats given ash compared to those given soil. An enhanced histological degree of granulomatous reactivity, lipoproteinosis, fibrosis, and bronchiolar hyperplasia was seen in ash-exposed rats as compared to soil-exposed rats. Mediastinal lymph nodes of ash-exposed rats were 8-18 times larger than those of soil-exposed rats due to abundant cellular microgranuloma formation and early fibrosis. Mount St. Helens volcanic ash is apparently more biologically reactive than soil particles commonly found in eastern Washington.

  7. Long-term reactivity of lung and mediastinal lymph nodes following intratracheal instillation of sandy loam soil or Mount St. Helens volcanic ash.

    PubMed

    Sanders, C L; Rhoads, K; Mahaffey, J A

    1983-10-01

    The effects of Ritzville sandy loam soil and Mount St. Helens volcanic ash particles on the lung and mediastinal lymph nodes of Fischer rats were studied about 400 days after intratracheal instillation. A total of 22 or 77 mg of soil or ash was given in two or seven equally divided, consecutive, weekly intervals as a suspension in 0.5 ml saline. Significantly elevated levels of lipid-phosphorus and protein were found in lung lavages of rats given ash compared to those given soil. An enhanced histological degree of granulomatous reactivity, lipoproteinosis, fibrosis, and bronchiolar hyperplasia was seen in ash-exposed rats as compared to soil-exposed rats. Mediastinal lymph nodes of ash-exposed rats were 8-18 times larger than those of soil-exposed rats due to abundant cellular microgranuloma formation and early fibrosis. Mount St. Helens volcanic ash is apparently more biologically reactive than soil particles commonly found in eastern Washington. PMID:6617611

  8. Effect of long-term different fertilization on bacterial community structures and diversity in citrus orchard soil of volcanic ash.

    PubMed

    Joa, Jae Ho; Weon, Hang Yeon; Hyun, Hae Nam; Jeun, Young Chull; Koh, Sang Wook

    2014-12-01

    This study was conducted to assess bacterial species richness, diversity and community distribution according to different fertilization regimes for 16 years in citrus orchard soil of volcanic ash. Soil samples were collected and analyzed from Compost (cattle manure, 2,000 kg/10a), 1/2 NPK+compost (14-20-14+2,000 kg/10a), NPK+compost (28-40-28+2,000 kg/10a), NPK (28-40-28 kg/10a), 3 NPK (84-120-84 kg/10a), and Control (no fertilization) plot which have been managed in the same manners with compost and different amount of chemical fertilization. The range of pyrosequencing reads and OTUs were 4,687-7,330 and 1,790-3,695, respectively. Species richness estimates such as Ace, Chao1, and Shannon index were higher in 1/2 NPK+compost than other treatments, which were 15,202, 9,112, 7.7, respectively. Dominant bacterial groups at level of phylum were Proteobacteria, Acidobacteria, and Actinobacteria. Those were occupied at 70.9% in 1/2 NPK+compost. Dominant bacterial groups at level of genus were Pseudolabrys, Bradyrhizobium, and Acidobacteria. Those were distributed at 14.4% of a total of bacteria in Compost. Soil pH displayed significantly closely related to bacterial species richness estimates such as Ace, Chao1 (p<0.05) and Shannon index (p<0.01). However, it showed the negative correlation with exchangeable aluminum contents (p<0.05). In conclusion, diversity of bacterial community in citrus orchard soil was affected by fertilization management, soil pH changes and characteristics of volcanic ash. PMID:25467117

  9. Volcanic soils and landslides: the case study of the Ischia island (southern Italy) and relationship with other Campania events

    NASA Astrophysics Data System (ADS)

    Vingiani, S.; Mele, G.; De Mascellis, R.; Terribile, F.; Basile, A.

    2015-01-01

    An integrated investigation has been carried out over the soils involved in the landslide phenomena occurred in the 2006 at Mt. Vezzi in the Ischia island (southern Italy). Chemical, physical (i.e. particle size distribution, hydrological analyses and direct measurements of soil porosity), mineralogical and micromorphological properties of three soil profiles selected in two of the main detachment crowns were analysed. The studied soils, having a volcanic origin, showed a substantial abrupt discontinuity of all the studied properties in correspondence of the 2C horizon, also identified as sliding surface of the landslide phenomena. With respect to the above horizons, the 2C showed (i) as a grey fine ash, almost pumices free, with a silt content increased by the 20%, (ii) ks values one order of magnitude lower, (iii) a porosity concentrated in the small size (15 to 30 μm modal class) pores characterized by very low percolation threshold (around 15-25 μm), (iv) occurrence of expandable clay minerals and (v) higher Na content in the exchange complex. Therefore, most of these properties indicated 2C as a lower permeability horizon than the above. Nevertheless, only the identification of a thin (6.5 mm) finely stratified ash layer on the top of 2C enabled to assume this interface as an impeding layer to vertical and horizontal water fluxes, as testified by the hydromorphic features (e.g. Fe / Mn concretions) within and on the top of the layer. Despite the Mt. Vezzi soil environment has many properties (high gradient northern facing slope, similar forestry, volcanic origin of the parent material) in common with those of many Campania debris-mud flows, the results of this study did not support the found relationship between Andosols and debris-mudflows, but emphasize the role of vertical discontinuities as landslide predisposing factor.

  10. Lichen-rock interaction in volcanic environments: evidences of soil-precursor formation

    NASA Astrophysics Data System (ADS)

    Vingiani, S.; Adamo, P.; Terribile, F.

    2012-04-01

    The weathering action of the lichens Lecidea fuscoatra (L.) Ach. and Stereocaulon vesuvianum Pers. on basaltic rock collected on the slopes of Mt. Etna (Sicily) at 1550 m a.s.l. has been studied using optical (OM) and electron (SEM) microscopy equipped with microanalytical device (EDS). Biological factors associated with lichen growth play a major role in the weathering of minerals on bare rocks and contribute to the preliminary phases of soil formation. The present work investigates the biogeophysical and biogeochemical weathering associated to the growth of epilithic lichens on lava flows from Mt. Etna (Sicily) and Mt. Vesuvius (Campania). The chosen lichen species were the crustose Lecidea fuscoatra (L.) Ach., the foliose Xanthoparmelia conspersa and the fructicose Stereocaulon vesuvianum Pers. An integrated approach based on the study of both disturbed and undisturbed samples of lichenized rock was applied in order to appreciate the complexity of the rock-lichen interface environment in terms of micromorphological, mineralogical and chemical properties. XRD and XRF analyses coupled to microscopical (OM), submicroscopical (SEM) and microanalitical (EDS) observations were the used techniques. In both study environments, the chemical, mineralogical and micromorphological properties of the uncoherent materials found at the lichen-rock interface suggest they consist of rock fragments eroded from the surroundings and accumulated in cavities and fissures of the rough lava flows. According to the thallus morphology, the lichens colonizing the lava preserve the interface materials from further aeolic and water erosion, provide these materials of organic matter and moisture, entrap allochtonous quartz and clay minerals. The calcium oxalate production by L. fuscoatra and X. conspersa, the Al enrichment around S. vesuvianum hyphae and the occurrence of Fe-oxide phases at the rock-lichen interface are evidences of lichens interaction with the underlying sediments. Indeed

  11. Effects of seagulls on ecosystem respiration, soil nitrogen and vegetation cover on a pristine volcanic island, Surtsey, Iceland

    NASA Astrophysics Data System (ADS)

    Sigurdsson, B. D.; Magnusson, B.

    2010-03-01

    When Surtsey rose from the North Atlantic Ocean south of Iceland in 1963, it became a unique natural laboratory on how organisms colonize volcanic islands and form ecosystems with contrasting structures and functions. In July, 2004, ecosystem respiration rate (Re), soil properties and surface cover of vascular plants were measured in 21 permanent research plots distributed among the juvenile communities of the island. The plots were divided into two main groups, inside and outside a seagull (Larus spp.) colony established on the island. Vegetation cover of the plots was strongly related to the density of gull nests. Occurrence of nests and increased vegetation cover also coincided with significant increases in Re, soil carbon, nitrogen and C:N ratio, and with significant reductions in soil pH and soil temperatures. Temperature sensitivity (Q10 value) of Re was determined as 5.3. When compared at constant temperature the Re was found to be 59 times higher within the seagull colony, similar to the highest fluxes measured in drained wetlands or agricultural fields in Iceland. The amount of soil nitrogen, mainly brought onto the island by the seagulls, was the critical factor that most influenced ecosystem fluxes and vegetation development on Surtsey. The present study shows how ecosystem activity can be enhanced by colonization of animals that transfer resources from a nearby ecosystem.

  12. Land use and Hydrological Characteristics of Volcanic Urban Soils for Flood Susceptibility Modeling, Ciudad de Colima (Mexico)

    NASA Astrophysics Data System (ADS)

    Perez Gonzalez, M. L.; Capra, L.; Borselli, L.; Ortiz, A.

    2015-12-01

    The fast population rate growth and the unplanned urban development has created an increase of urban floods in the City of Colima. Land use change has transformed the hydrological behavior of the watersheds that participates on the runoff-infiltration processes that governs the pluvial concentrations. After the urban areas enlargement, 13% from 2010 to 2015, rainfall has caused significant damages to the downtown community. Therefore it is important to define the main hydraulic properties of the soils surrounding the city. The soil of the region is derived from the debris avalanche deposits of the Volcano of Colima. The volcanic soil cover is only 10 to 15 cm depth. To test the soils of the region, sampling locations were chosen after making a land use map from a Landsat image. The map was done by selecting and dividing similar surface images patterns into three main classifications: Natural (N1), Agricultural (N5) and Urban (N4) surfaces. Thirty-Three soil samples were collected and grouped in nine out of ten land use subdivisions. The 10thsubdivision, represents the completed urbanized area. The land use model is made using spot 4 1A images from the year 2010 up to year 2015. This land use evolutionary analysis will be a base to evaluate the change of the runoff-infiltration rate, direction, and concentration areas for the future flood susceptibility model. To get the parameters above, several soil analysis were performed. The results were that all the soil samples tested were classified as sandy soils. The water content values were from 7% (N4) to 45% (N1) while bulk density values for the same sample were form 0.65 (N1) to 1.50 (N4) g/cm3. The particle density and the porosity values were from 1.65 g/cm3 /5.5% (N4) - 2.65 g/cm3/ 75.40% (N1). The organic matter content was around 0.1% for urban soils and up to 6% on natural and agricultural soils. Some other test like electric conductivity and pH were performed. The obtained parameters were used to get other

  13. Evaluation of Drainage from Passive Suction and Nonsuction Flux Meters in a Volcanic Clay Soil under Tropical Conditions

    SciTech Connect

    van der Velde, M; Green, S R.; Gee, Glendon W.; Vanclooster, M; Clothier, B E.

    2005-11-30

    Root zone drainage measurements are needed to improve fertilizer management in areas where agriculture may be impacting groundwater supplies. We present results of field tests where drainage was measured with two types of suction (resolution of 0.16 and 1.6 mm -1) and a nonsuction (resolution of 0.22 mm tip-1) water flux meter (WFM). The soil was a microstructured weathered volcanic ash located on a coral atoll subject to intense rainfall and located in the Kingdom of Tonga. Our objectives were to evaluate water flux measurements by comparing them with (i) simple water balance estimates of cumulative fluxes deduced from soil moisture content changes, and (iii) simulated fluxes using HYDRUS-1D. Soil hydraulic properties were obtained at five soil depths. During the 60-d evaluation period rainfall totaled 340 mm. The WFMs were installed in duplicate using disturbed soil. The consistency of the shape of the drainage curves measured with the WFMs, those derived from soil moisture changes, and those obtained with modeling led us to conclude that soil disturbance during WFM installation did not severely influence measurements. This was attributed to the strong microaggregation and disturbance introduced by plowing. Water balance and HYDRUS model estimates of drainage corresponded well with the measurement by nonsuction WFMs. Suction WFMs overestimated drainage, possibly due to flow convergence created by wick and divergence barrier lengths being not properly sized for the observed flow conditions. After the evaluation period some of the WFMs failed to respond. Nevertheless, flux meters are seen as promising tools to provide remote and continuous measurement of root zone drainage.

  14. Metsulfuron-methyl sorption/desorption behavior on volcanic ash-derived soils. effect of phosphate and pH.

    PubMed

    Cáceres, Lizethly; Fuentes, Roxana; Escudey, Mauricio; Fuentes, Edwar; Báez, María E

    2010-06-01

    Metsulfuron-methyl sorption/desorption behavior was studied through batch sorption experiments in three typical volcanic ash-derived soils belonging to Andisol and Ultisol orders. Their distinctive physical and chemical properties are acidic pH and variable surface charge. Organic matter content and mineral composition affected in different ways sorption of metsulfuron-methyl (K(OC) ranging from 113 to 646 mL g(-1)): organic matter and iron and aluminum oxides mainly through hydrophilic rather than hydrophobic interactions in Andisols, and Kaolinite group minerals, as major constituents of Ultisols, and iron and aluminum oxides only through hydrophilic interactions. The Freundlich model described metsulfuron-methyl behavior in all cases (R(2) > 0.992). K(f) values (3.1-14.4 microg(1-1/n) mL(1/n) g(-1)) were higher than those reported for different class of soils including some with variable charge. Hysteresis was more significant in Ultisols. A strong influence of pH and phosphate was established for both kinds of soil, intensive soil fertilization and liming being the most probable scenario for leaching of metsulfuron-methyl, particularly in Ultisols. PMID:20455566

  15. [Hardening of dental instruments].

    PubMed

    Gerasev, G P

    1981-01-01

    The possibility of prolonging the service life of stomatological instruments by the local hardening of their working parts is discussed. Such hardening should be achieved by using hard and wear-resistant materials. The examples of hardening dental elevators and hard-alloy dental drills are given. New trends in the local hardening of instruments are the treatment of their working parts with laser beams, the application of coating on their surface by the gas-detonation method. The results of research work and trials are presented. PMID:7300627

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  17. Ammonia emission from a permanent grassland on volcanic soil after the treatment with dairy slurry and urea

    NASA Astrophysics Data System (ADS)

    Salazar, F.; Martínez-Lagos, J.; Alfaro, M.; Misselbrook, T.

    2014-10-01

    Ammonia (NH3) is an air pollutant largely emitted from agricultural activities including the application of livestock manures and fertilizers to grassland. This gas has been linked with important negative impacts on natural ecosystems. In southern Chile, the use of inorganic and organic fertilizers (e.g. slurries) has increased in cattle production systems over recent years, heightening the risk of N losses to the wider environment. The objectives of this study were to evaluate on permanent grasslands on a volcanic ash soil in southern Chile: 1) the N loss due to NH3 volatilization following surface application of dairy slurry and urea fertilizer; and 2) the effect of a urease inhibitor on NH3 emissions from urea fertilizer application. Small plot field experiments were conducted over spring, fall, winter and summer seasons, using a system of wind tunnels to measure ammonia emissions. Ammonia losses ranged from 1.8 (winter) to 26.0% (fall) and 3.1 (winter) to 20.5% (summer) of total N applied for urea and slurry, respectively. Based on the readily available N applied (ammoniacal N for dairy slurry and urea N for urea fertilizer), losses from dairy slurry were much greater, at 16.1 and 82.0%, for winter and summer, respectively. The use of a urease inhibitor proved to be an effective option to minimize the N loss due NH3 volatilization from urea fertilizer, with an average reduction of 71% across all seasons. The results of this and other recent studies regarding N losses suggest that ammonia volatilization is the main pathway of N loss from grassland systems in southern Chile on volcanic ash soils when urea and slurry are used as an N source. The use of good management practices, such as the inclusion of a urease inhibitor with urea fertilizer could have a beneficial impact on reducing N losses due NH3 volatilization and the environmental and economic impact of these emissions.

  18. Volcanic soil formation in Calabria (southern Italy): The Cecita Lake geosol in the late Quaternary geomorphological evolution of the Sila uplands

    NASA Astrophysics Data System (ADS)

    Scarciglia, Fabio; De Rosa, Rosanna; Vecchio, Giuseppe; Apollaro, Carmine; Robustelli, Gaetano; Terrasi, Filippo

    2008-10-01

    This paper focuses on the main morphological, physical, chemical and mineralogical features of an andic-like soil, widely outcropping in the Sila upland plateau of Calabria (southern Italy), and its potential role in tephrostratigraphy. A multidisciplinary and multiscale approach allowed identification of this soil as a "masked" distal archive of volcanic products, developed on granite rocks and sediments with a coeval pyroclastic input during pedogenesis. The study demonstrates that the contribution of volcanic parent materials can be successfully hypothesized and assessed even in the absence, limited extent or poor preservation of primary eruptive products. The soil has an Andisol-like appearance, despite laboratory data that do not match the entire suite of diagnostic criteria for the Andisol taxonomic order. Geomorphological, stratigraphic and pedologic results, coupled with tephrostratigraphic and radiometric data, concur to suggest a Late Pleistocene(?) to Holocene age of the Andisol-like soil. In particular, the rhyolitic chemical composition of small-sized glass fragments (identified by SEM-EDS analyses) indicates soil genesis contributed by volcanic ash, probably sourced from Aeolian Arc explosive activity spanning the last 30 ka. Accordingly, the evidence of limited relict clay illuviation and the specific type of pedogenesis allowing the development of andic properties (in turn related to the neoformation of clay minerals from the weathering of volcanic glass) are consistent with a climatic shift from a seasonally-contrasted to a constantly humid pedoenvironment. This change can be ascribed to the Lateglacial(?) or Early-Middle Holocene to Late Holocene transition. Calibrated AMS 14C dates performed on charcoal fragments sampled from three representative soil profiles, provide Late Holocene ages (3136 ± 19, 343 ± 16 and 92 ± 24 yr BP), in accord with archaeological finds. On the basis of the consistent stratigraphic position, lateral continuity and

  19. Effects of Inter- and Intra-aggregate Pore Space on the Soil-Gas Diffusivity Behavior in Unsaturated, Undisturbed Volcanic Ash Soils

    NASA Astrophysics Data System (ADS)

    Resurreccion, A. C.; Kawamoto, K.; Komatsu, T.; Moldrup, P.

    2006-12-01

    Volcanic ash soils (Andisols) have a unique dual porosity structure that results in good drainage and high soil- water retention. Despite of the complicated and highly developed soil structure, recent studies have reported a simple, highly linear relation between the soil-gas diffusion coefficient, Dp, and the soil-air content, ɛ, for several Japanese Andisols. In this study, we explain the linear Dp(ɛ) behavior from the effects of the inter- and intra-aggregate pore-size distributions. We couple the bimodal van Genuchten soil-water retention model with a general Dp(ɛ) model, ɛ^{X}, allowing the tortuosity- connectivity factor X to vary with pF (= log(-ψ; the soil-water matric potential in cm H2O)). Measured data suggest that the tortuosity-connectivity parameter X is at the minimum at pF 3 (where X ~ 2, following Buckingham, 1904), equal to the water retention point where a separation of inter- and intra-aggregate effects on Dp is observed. At pF < 3, the X values increased as pF decreased because of inactive/remote air-filled pore space entrapped by the inter-connected water films between inter-aggregate pore spaces. At pF > 3, X increased to a high value at very dry conditions due to remote air-filled space inside the intra-aggregate pores. By combining the complex dual porosity soil-water retention model with the power- law gas diffusivity model using a parabolic X(pF) function, the surprisingly simple linear behavior of Dp with ɛ was captured while the variation of Dp with pF followed a dual s-shaped curve similar to the water retention curve. A simple linear model to predict Dp(ɛ) is suggested, with slope C and threshold soil-air content, ɛth, calculated from the power-law model ɛ^{X} at pF 2 (near field capacity) and at pF 4.1 (near wilting point) using the same X value (= 2.3) at both pF in agreement with measured data. This linear Dp(ɛ) model performed better, especially at dry conditions, compared to the traditionally-used predictive models when

  20. Carbon flow from volcanic CO2 into soil microbial communities of a wetland mofette.

    PubMed

    Beulig, Felix; Heuer, Verena B; Akob, Denise M; Viehweger, Bernhard; Elvert, Marcus; Herrmann, Martina; Hinrichs, Kai-Uwe; Küsel, Kirsten

    2015-03-01

    Effects of extremely high carbon dioxide (CO2) concentrations on soil microbial communities and associated processes are largely unknown. We studied a wetland area affected by spots of subcrustal CO2 degassing (mofettes) with focus on anaerobic autotrophic methanogenesis and acetogenesis because the pore gas phase was largely hypoxic. Compared with a reference soil, the mofette was more acidic (ΔpH ∼0.8), strongly enriched in organic carbon (up to 10 times), and exhibited lower prokaryotic diversity. It was dominated by methanogens and subdivision 1 Acidobacteria, which likely thrived under stable hypoxia and acidic pH. Anoxic incubations revealed enhanced formation of acetate and methane (CH4) from hydrogen (H2) and CO2 consistent with elevated CH4 and acetate levels in the mofette soil. (13)CO2 mofette soil incubations showed high label incorporations with ∼512 ng (13)C g (dry weight (dw)) soil(-1) d(-1) into the bulk soil and up to 10.7 ng (13)C g (dw) soil(-1) d(-1) into almost all analyzed bacterial lipids. Incorporation of CO2-derived carbon into archaeal lipids was much lower and restricted to the first 10 cm of the soil. DNA-SIP analysis revealed that acidophilic methanogens affiliated with Methanoregulaceae and hitherto unknown acetogens appeared to be involved in the chemolithoautotrophic utilization of (13)CO2. Subdivision 1 Acidobacteriaceae assimilated (13)CO2 likely via anaplerotic reactions because Acidobacteriaceae are not known to harbor enzymatic pathways for autotrophic CO2 assimilation. We conclude that CO2-induced geochemical changes promoted anaerobic and acidophilic organisms and altered carbon turnover in affected soils. PMID:25216086

  1. Exploring a long-lasting volcanic eruption by means of in-soil radon measurements and seismic activity

    NASA Astrophysics Data System (ADS)

    Falsaperla, Susanna; Neri, Marco; Di Grazia, Giuseppe; Langer, Horst; Spampinato, Salvatore

    2016-04-01

    We analyze in-soil radon (Rn) emission and ambient parameters (barometric pressure and air temperature measurements) along with seismic activity during the longest flank eruption of this century at Mt. Etna, Italy. This eruption occurred between 14 May 2008 and 6 July 2009, from a N120-140°E eruptive fissure extending between 3050 and 2620 m above sea level. It was heralded by a short-lived (~5 hours) episode of lava fountaining three days before a dike-forming intrusion fed a lava emission, which affected the summit area of the volcano over ~15 months. The peculiar position of the station for the Rn measurement, which was at an altitude of 2950 m above sea level and near (~1 km) the summit active craters, offered us the uncommon chance: i) to explore the temporal development of the gas emission close (<2 km) to the 2008-2009 eruptive vents in the long term, and ii) to analyze the relationship between in-soil Rn fluxes and seismic signals (in particular, local earthquakes and volcanic tremor) during the uninterrupted lava emission. This approach reveals important details about the recharging phases characterizing the 2008-2009 eruption, which are not visible with other methods of investigation. Our study benefitted from the application of methods of pattern classification developed in the framework of the European MEDiterrranean Supersite Volcanoes (MED­SUV) project.

  2. Carbon flow from volcanic CO2 into soil microbial communities of a wetland mofette

    USGS Publications Warehouse

    Beulig, Felix; Heuer, Verena B.; Akob, Denise M.; Viehweger, Bernhard; Elvert, Marcus; Herrmann, Martina; Hinrichs, Kai-Uwe; Küsel, Kirsten

    2015-01-01

    Effects of extremely high carbon dioxide (CO2) concentrations on soil microbial communities and associated processes are largely unknown. We studied a wetland area affected by spots of subcrustal CO2 degassing (mofettes) with focus on anaerobic autotrophic methanogenesis and acetogenesis because the pore gas phase was largely hypoxic. Compared with a reference soil, the mofette was more acidic (ΔpH ~0.8), strongly enriched in organic carbon (up to 10 times), and exhibited lower prokaryotic diversity. It was dominated by methanogens and subdivision 1Acidobacteria, which likely thrived under stable hypoxia and acidic pH. Anoxic incubations revealed enhanced formation of acetate and methane (CH4) from hydrogen (H2) and CO2 consistent with elevated CH4 and acetate levels in the mofette soil. 13CO2 mofette soil incubations showed high label incorporations with ~512 ng13C g (dry weight (dw)) soil−1 d−1 into the bulk soil and up to 10.7 ng 13C g (dw) soil−1 d−1 into almost all analyzed bacterial lipids. Incorporation of CO2-derived carbon into archaeal lipids was much lower and restricted to the first 10 cm of the soil. DNA-SIP analysis revealed that acidophilic methanogens affiliated withMethanoregulaceae and hitherto unknown acetogens appeared to be involved in the chemolithoautotrophic utilization of 13CO2. Subdivision 1 Acidobacteriaceae assimilated 13CO2 likely via anaplerotic reactions because Acidobacteriaceae are not known to harbor enzymatic pathways for autotrophic CO2 assimilation. We conclude that CO2-induced geochemical changes promoted anaerobic and acidophilic organisms and altered carbon turnover in affected soils.

  3. Carbon flow from volcanic CO2 into soil microbial communities of a wetland mofette

    PubMed Central

    Beulig, Felix; Heuer, Verena B; Akob, Denise M; Viehweger, Bernhard; Elvert, Marcus; Herrmann, Martina; Hinrichs, Kai-Uwe; Küsel, Kirsten

    2015-01-01

    Effects of extremely high carbon dioxide (CO2) concentrations on soil microbial communities and associated processes are largely unknown. We studied a wetland area affected by spots of subcrustal CO2 degassing (mofettes) with focus on anaerobic autotrophic methanogenesis and acetogenesis because the pore gas phase was largely hypoxic. Compared with a reference soil, the mofette was more acidic (ΔpH ∼0.8), strongly enriched in organic carbon (up to 10 times), and exhibited lower prokaryotic diversity. It was dominated by methanogens and subdivision 1 Acidobacteria, which likely thrived under stable hypoxia and acidic pH. Anoxic incubations revealed enhanced formation of acetate and methane (CH4) from hydrogen (H2) and CO2 consistent with elevated CH4 and acetate levels in the mofette soil. 13CO2 mofette soil incubations showed high label incorporations with ∼512 ng 13C g (dry weight (dw)) soil−1 d−1 into the bulk soil and up to 10.7 ng 13C g (dw) soil−1 d−1 into almost all analyzed bacterial lipids. Incorporation of CO2-derived carbon into archaeal lipids was much lower and restricted to the first 10 cm of the soil. DNA-SIP analysis revealed that acidophilic methanogens affiliated with Methanoregulaceae and hitherto unknown acetogens appeared to be involved in the chemolithoautotrophic utilization of 13CO2. Subdivision 1 Acidobacteriaceae assimilated 13CO2 likely via anaplerotic reactions because Acidobacteriaceae are not known to harbor enzymatic pathways for autotrophic CO2 assimilation. We conclude that CO2-induced geochemical changes promoted anaerobic and acidophilic organisms and altered carbon turnover in affected soils. PMID:25216086

  4. Construction procedures using self hardening fly ash

    NASA Astrophysics Data System (ADS)

    Thornton, S. I.; Parker, D. G.

    1980-07-01

    Fly ash produced in Arkansas from burning Wyoming low sulfur coal is self-hardening and can be effective as a soil stabilizing agent for clays and sands. The strength of soil-self hardening fly ash develops rapidly when compacted immediately after mixing. Seven day unconfined compressive strengths up to 1800 psi were obtained from 20% fly ash and 80% sand mixtures. A time delay between mixing the fly ash with the soil and compaction of the mixture reduced the strength. With two hours delay, over a third of the strength was lost and with four hours delay, the loss was over half. Gypsum and some commercial concrete retarders were effective in reducing the detrimental effect of delayed compaction. Adequate mixing of the soil and fly ash and rapid compaction of the mixtures were found to be important parameters in field construction of stabilized bases.

  5. Dissolved Organic Matter as a Mechanism for Carbon Stabilization at Depth in Wet Tropical Forest Volcanic Soils

    NASA Astrophysics Data System (ADS)

    Marin-Spiotta, E.; Kramer, M. G.; Chadwick, O. A.

    2007-12-01

    Dissolved organic matter (DOM) plays an important role in many biological and chemical processes in soils. Our understanding of the types of plant and microbially-derived organic matter that accumulate in soils and the mechanisms responsible for their transformation and stabilization is still limited. In particular, we know very little about how microbial activity and water movement contribute to the production of DOM and the formation of stable C in soils. In well-drained soils under wet climates, DOM is potentially a primary pathway for the transport of C from the surface litter layers and the zones of highest microbial activity to deeper horizons in the soil profile where the potential for long-term storage increases. The mechanisms for long-term stabilization of organic C in deep mineral horizons include an accumulation of chemically recalcitrant C, strong sorption of soluble and otherwise labile C to mineral and/or metals making them inaccessible to decomposers, and microenvironmental conditions (low pH, low O2) which result in incomplete decomposition and persistence of labile C. Although most work to date has focused on the role of dissolved organic C and N (DOC and DON) in the C and N cycles of temperate forests, DOM fluxes may be even more important in forests in the wet tropics, where high rainfall and high primary productivity could lead to greater DOM production. In order to address the role of DOC in the transport and stabilization of C in mineral horizons, we are studying DOC production, transformation, and loss pathways in volcanic soils dominated by highly reactive, non-crystalline minerals (allophane). We are quantifying flux and solute concentrations (C, N, cations, anions) in rainwater, throughfall, and in soil water. We have installed tension and zero tension lysimeters throughout sequentially deeper organic and mineral horizons in an intermediate aged soil (ca. 350k years) under wet (ca. 3000 mm mean annual rainfall) native tropical forest

  6. The emissions and soil concentrations of N2O and CH4 from natural soil temperature gradients in a volcanic area in southwest Iceland

    NASA Astrophysics Data System (ADS)

    Maljanen, Marja; Yli-Moijala, Heli; Leblans, Niki I. W.; De Boeck, Hans J.; Bjarnadóttir, Brynhildur; Sigurdsson, Bjarni D.

    2016-04-01

    We studied nitrous oxide (N2O) and methane (CH4) emissions along three natural geothermal soil temperature (Ts) gradients in a volcanic area in southwest Iceland. Two of the gradients (on a grassland and a forest site, respectively) were recently formed (in May 2008). The third gradient, a grassland site, had been subjected to long-term soil warming (over 30 years, and probably centuries). Nitrous oxide and methane emissions were measured along the temperature gradients using the static chamber method and also soil gas concentrations were studied. With a moderate soil temperature increase (up to +5 °C) there were no significant increase in gas flux rates in any of the sites but an increase of 20 to 45 °C induced an increase in both N2O and CH4 emissions. The measured N2O emissions (up to 2600 μg N2O m-2 h-1) from the warmest plots were about two magnitudes higher compared with the coolest plots (less than 20 μg N2O m-2 h-1). While a net uptake of CH4 was measured in the coolest plots (up to -0.15 mg CH4 m-2 h-1), a net emission of CH4 was measured from the warmest plots (up to 1.3 mg CH4 m-2 h-1). Soil CH4 concentrations decreased first with a moderate (up to +5 °C) increase in Ts, but above that threshold increased significantly. The soil N2O concentration at depths from 5 to 20 cm increased with increasing Ts, indicating enhanced N-turnover. Further, there was a clear decrease in soil organic matter (SOM), C- and N concentration with increasing Ts at all sites. One should note, however, that a part of the N2O emitted from the warmest plots may be partly geothermally derived, as was revealed by 15N2O isotope studies. These natural Ts gradients show that the emission of N2O and CH4 can increase significantly when Ts increases considerably. This implies that these geothermally active sites can act as local hot spots for CH4 and N2O emissions.

  7. Runoff and erosion effects after prescribed fire and wildfire on volcanic ash-cap soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    AFTER PRESCRIBED BURNS AT THREE LOCATIONS AND ONE WILDFIRE, RAINFALL SIMULATIONS STUDIES WERE COMPLETED TO COMPARE POSTFIRE RUNOFF RATES AND SEDIMENT YIELDS ON ASH-CAP SOIL IN CONIFER FOREST REGIONS OF NOTHERN IDAHO AND WESTERN MONTANA. THE MEASURED FIRE EFFECTS WERE DIFFERENTIATED BY BURN SEVERITY ...

  8. Hardening of the arteries

    MedlinePlus

    Atherosclerosis; Arteriosclerosis; Plaque buildup - arteries; Hyperlipidemia - atherosclerosis; Cholesterol - atherosclerosis ... Hardening of the arteries often occurs with aging. As you grow older, ... narrows your arteries and makes them stiffer. These changes ...

  9. Volcanic Gas

    MedlinePlus

    ... Hazards Tephra/Ash Lava Flows Lahars Volcanic Gas Climate Change Pyroclastic Flows Volcanic Landslides Preparedness Volcano Hazard Zones ... Please see our discussion of volcanic gases and climate change for additional information. Hydrogen sulfide (H 2 S) is ...

  10. Nitrogen transformations following tropical forest felling and burning on a volcanic soil

    SciTech Connect

    Matson, P.A.; Vitousek, P.M.; Ewel, J.J.; Mazzarino, M.J.; Robertson, G.P.

    1987-06-01

    The authors measured nitrogen transformations and loss following forest clearing in a relatively fertile tropical forest site. Nitrogen mineralization, nitrification, and amounts of ammonium and nitrate increased substantially in surface soils during the 6 mo following burning, then returned to background levels. The nitrogen content of microbial biomass declined to half its original value 6 mo after clearing and remained low in the cleared sites. Plant uptake of nitrogen was substantial on cleared plots (50 g/m/sup 2/), but it accounted for only 18% of /sup 15/N label added to field plots. Microbial immobilization of /sup 15/N was small relative to that in a cleared temperature site, and measurements of dinitrification potentials suggested that relatively little mineralized nitrogen was lost to the atmosphere. Substantial amounts of nitrogen (40-70 g/m/sup 2/) were retained as exchangeably bound nitrate deep in the soils of a cleared plot on which revegetation was prevented; this process accounted for 12% of the /sup 15/N label added to field plots.

  11. Nitrogen transformations following tropical forest felling and burning on a volcanic soil

    NASA Technical Reports Server (NTRS)

    Matson, Pamela A.; Vitousek, Peter M.; Ewel, John J.; Mazzarino, Maria Julia; Robertson, G. Philip

    1987-01-01

    Nitrogen transformations and loss were measured following forest clearing in a relatively fertile tropical forest site. Nitrogen mineralization, nitrification, and amounts of ammonium and nitrate increased substantially in surface soils during the 6 mo following burning, then returned to background levels. The nitrogen content of microbial biomass declined to half its original value 6 mo after clearing and remained low in the cleared sites. Plant uptake of nitrogen was substantial on cleared plots (50 g/sq m), but it accounted for only 18 percent of N-15 label added to field plots. MIcrobial immobilization of N-15 was small relative to that in a cleared temperate site, and measurements of denitrification potentials suggested that relatively little mineralized nitrogen was lost to the atmosphere. Substantial amounts of nitrogen (40-70 g/sq m) were retained as exchangeably bound nitrate deep in the soils of a cleared plot on which revegetation was prevented; this process accounted for 12 percent of the N-15 label added to field plots.

  12. Late Pleistocene to Holocene soil development and environments in the Long Gang Volcanic Field area, Jilin Province, NE China

    NASA Astrophysics Data System (ADS)

    Sauer, Daniela; Zhang, Xinrong; Knöbel, Jette; Maerker, Lutz

    2014-05-01

    Late Pleistocene to Holocene shifts of climate and vegetation in the Long Gang Volcanic Field in NE China have been reconstructed, e. g. by Steblich et al. (2009), based on Maar lake sediment cores. In this study, we investigated soil development during the Late Pleistocene and Holocene and linked it to the climate and vegetation reported in the literature. Three pedons were described and analyzed on a crater wall surrounding a maar. The lower part of the slope is covered by basic pyroclastics that are obviously younger than the maar itself. Pedon 1 is located on the upper slope, where the younger pyroclastics are not present; thus it developed over the entire Holocene and part of the Late Pleistocene. Pedon 2 is on the toe slope and developed from the young basic pyroclastics. Vegetation remains, charred by fire that was caused by the volcanic ash fall, were found in the lowermost part of the pyroclastics layer, on top of a paleosol. Charcoal fragments were dated to 18950-18830 cal BP (using INTCAL 09). Thus, pedon 2 developed since around 18.9 ka BP, whereas the development of the paleosol that was buried under the pyroclastics (pedon 3), was stopped at this time. Pedons 1 and 2 are Vitric Andosols, developed mainly from basic pyroclastics, as evidenced by the composition of rock fragments in the soils, comprising 78 / 81 mass % lapilli and 22 / 19 mass % gneiss fragments, respectively. Pedon 3 is a Cutanic Luvisol (Chromic) that developed entirely from gneiss fragments produced by the maar explosion. Lab data suggest increasing intensity of pedogenesis in the direction: Pedon 3 (paleosol) < Pedon 2 < Pedon 1, reflected e. g. in increasing Fed/Fet ratios, decreasing molar ratios of (Ca+K+Na)/Al, and decreasing pH. However, it needs to be considered that lapilli are more readily weatherable than gneiss fragments. The profile morphology of the paleosol, characterized by reddish-brown color (7.5YR), strong angular blocky structure and well-expressed illuvial clay

  13. Ammonia volatilization following dairy slurry application to a permanent grassland on a volcanic soil

    NASA Astrophysics Data System (ADS)

    Martínez-Lagos, J.; Salazar, F.; Alfaro, M.; Misselbrook, T.

    2013-12-01

    Agriculture is the largest source of ammonia (NH3) emission to the atmosphere. Within the agricultural sector, the application of slurry to grasslands as fertilizer is one of the main emission sources. This is a common practice in southern Chile, where most dairy production systems are grazing-based. In Chile, there are few published data of gaseous emissions following slurry application to grassland. The aim of this study was to evaluate NH3 volatilization following dairy slurry application to a permanent grassland on an Andosol soil. Ammonia volatilization was measured in four field experiments (winters of 2009 and 2011 and early and late springs of 2011) using a micrometeorological mass balance method with passive flux samplers following dairy slurry application at a target rate of 100 kg total N ha-1. The accumulated N loss was equivalent to 7, 8, 16 and 21% of the total N applied and 22, 34, 88 and 74% of total ammoniacal nitrogen (TAN) applied for winters 2009 and 2011, and early and late spring 2011, respectively. Ammonia emission rates were high immediately after application and declined rapidly with time, with more than 50% of the total emissions within the first 24 h. Losses were highly influenced by environmental conditions, increasing with temperature and lack of rainfall. Taking into consideration the low N losses via leaching and nitrous oxide emissions reported for the study area, results indicate that NH3 volatilization is the main pathway of N loss in fertilized grasslands of southern Chile. However, dairy slurry application could be an important source of nutrients, if applied at a suitable time, rate and using an appropriate technique, and if soil and climate conditions are taken into consideration. This could improve N use efficiency and reduce N losses to the wider environment.

  14. 42. INTERIOR VIEW OF THE NAIL HARDENER USED TO HARDEN ...

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

    42. INTERIOR VIEW OF THE NAIL HARDENER USED TO HARDEN AND TEMPER THE NAILS; WEST TUBES IN FOREGRPUND AND DRAWBACK TUBE IN THE CENTER - LaBelle Iron Works, Thirtieth & Wood Streets, Wheeling, Ohio County, WV

  15. Volcanism on Mars

    NASA Astrophysics Data System (ADS)

    Greeley, R.; Spudis, P. D.

    1981-02-01

    In situ chemical analyses of Martian soil by the Viking lander indicate mafic to ultramafic source rocks, consistent with both remote sensing data indicating the presence of pyroxene and olivine and with petrologic modeling which suggests that Martian lavas are iron-rich and ultramafic. Photogeological analysis of the Martian surface reveals two types of volcanic morphology: (1) central volcanoes, developed by continued and prolonged eruption from a point source vent; and (2) volcanic plains, recognized by mare ridges and flow lobes. When these volcanic morphologies are combined with relative age data, a volcanic history may be derived that is consistent with a moonlike thermal history involving a lithosphere of increasing thickness with time which gradually suppresses the volcanism.

  16. Ecosystem respiration, vegetation development and soil nitrogen in relation to breeding density of seagulls on a pristine volcanic island, Surtsey, Iceland

    NASA Astrophysics Data System (ADS)

    Sigurdsson, B. D.; Magnusson, B.

    2009-08-01

    Since its birth in 1963 by volcanic eruption in the North Atlantic Ocean off Iceland, Surtsey has been a unique natural laboratory on how organisms colonize volcanic islands and form ecosystems with contrasting structure and function. In July, 2004, ecosystem respiration rate, soil properties and surface cover of vascular plants were measured on 21 plots distributed among the main plant communities found 40 years after the primary succession started. The plots could be divided into two groups, inside and outside seagull (Larus sp.) colonies found on the island. Vegetation cover of the plots was strongly related to the density of seagull nests within and around them. The occurrence of seagull nests and increased vegetation also coincided with significant increase in ecosystem respiration, soil carbon and nitrogen, and with significantly lower soil pH and soil temperatures. The ecosystem respiration was high inside the gull colonies, similar to the highest fluxes measured in drained wetlands or agricultural fields in Iceland. The most important factor for vegetation succession and ecosystem function on Surtsey seems to be the amount of nitrogen, which was mainly brought in by the seagulls.

  17. Sorption-desorption behavior of pesticides and their degradation products in volcanic and nonvolcanic soils: interpretation of interactions through two-way principal component analysis.

    PubMed

    Báez, María E; Espinoza, Jeannette; Silva, Ricardo; Fuentes, Edwar

    2015-06-01

    Sorption-desorption behavior of six pesticides and some degradation products was assessed on seven agricultural volcanic and nonvolcanic soils belonging to Andisol, Ultisol, Mollisol, and Alfisol orders. The global interpretation of sorption data was performed by principal component analysis. Results showed exceptionally high sorption of glyphosate and aminomethylphosphonic acid (AMPA) (the breakdown product) on volcanic soils (K f > 1500 μg(1 - 1 / n) mL(1 / n) g(-1)) related mainly to contents of amorphous aluminum oxides (Andisols) and crystalline minerals (Ultisols). The lower sorption on nonvolcanic soils was associated to low organic matter contents and lack of significant minerals. Metsulfuron-methyl and 3,5,6-trichloro-2-pyridinol (metabolite of chlorpyrifos) were weakly to substantially sorbed on Andisols and Ultisols, but the first one was not sorbed at pH > 6.4, including nonvolcanic soils. The metabolite of diazinon, 2-isopropyl-4-methyl-6-hydroxypyrimidine, was weakly sorbed on all soils (K f = 0.4 to 3.6 μg(1 - 1 / n) mL(1 / n) g(-1)). Acidic compounds would be lixiviated in Mollisols and Alfisols, but they could leach also in Andisols and Ultisols if they reach greater depths. Atrazine and deethylatrazine sorption was related to organic carbon content; therefore, they were weakly retained on nonvolcanic soils (K f = 0.7 to 2.2 μg(1 - 1 / n) mL(1 / n) g(-1)). Chlorpyrifos was highly sorbed on all soils reaching K OC values of >8000. Finally, the significant retention of chlorothalonil and diazinon on Mollisols and Alfisols in spite of their low OC contents showed the contribution of clay minerals in the sorption process. PMID:25561264

  18. Application of Spectroscopic Techniques (FT-IR, 13C NMR) to the analysis of humic substances in volcanic soils along an environmental gradient (Tenerife, Canary Islands, Spain)

    NASA Astrophysics Data System (ADS)

    Rodriguez Rodriguez, Antonio; María Armas Herrera, Cecilia; González Pérez, José Antonio; González-Vila, Francisco Javier; Arbelo Rodríguez, Carmen Dolores; Mora Hernández, Juan Luis; Polvillo Polo, Oliva

    2010-05-01

    Andosols and andic soils are considered as efficient C-sinks in terms of C sequestration. These soils are usually developed from volcanic materials, and are characterized by a predominance of short-range ordered minerals like allophanes, imogolite and other Fe and Al oxyhydroxides. Such materials occur commonly associated with organic compounds, thus generating highly stable organo-mineral complexes and leading to the accumulation of a high amount of organic carbon. Spectroscopic methods like FT-IR and 13C NMR are suitable for the analysis of the chemical structure of soil humic substances, and allow identifying distinct functional groups and protein, lipids, lignin, carbohydrate-derived fragments. In this work we study the structural features of four soils developed on Pleistocene basaltic lavae in Tenerife (Canary Island, Spain), distributed along an altitudinal climatic gradient. The soil sequence comprises soils with different degree of geochemical evolution and andic character, including a mineral ‘Hypersalic Solonchak' (Tabaibal de Rasca), a slightly vitric ‘Luvic Phaeozem' (Los Frailes), a degraded and shallow ‘Endoleptic, fulvic, silandic Andosol' (Siete Lomas), and a well-developed and deep ‘Fulvic, silandic, Andosol' (Ravelo). Samples of the raw soil and humic and fulvic acids isolated from the surface horizons were analyzed. The results show a low content of organic carbon in the mineral soil, the inherited humin predominating, and a very high content of humic and fulvic acids in Andosols. The FT-IR and 13C NMR spectra of the raw soil samples show a low resolution, related to interferences from mineral complexes signals, particularly in soils with lower organic carbon content. 13C NMR shows a predominance of O-alkyl carbon (derived of carbohydrates) in andic soils, whereas O-alkyl and aromatic fractions are most evident in the mineral soil. The humic acids spectra are characterized by a dominance of alkyl and aromatic fractions with a high degree

  19. Spatial variability in depth and landscape of heavy metal contents of volcanic soils of the National Cajas Park in the Azuay Andes (Ecuador)

    NASA Astrophysics Data System (ADS)

    Bech, Jaume; Roca, Núria; Boluda, Rafael; Gil, Carlos; Ramos-Miras, Joaquín; Rodríguez, Jose A.

    2015-04-01

    Although the soils in the Azuay Andes are thought to be generally non-contaminated, it is necessary to preserve them from anthropogenic pollution. This area supplies drinking water to Cuenca, the third city of Ecuador. At present, very little information is available on baseline metal concentrations in Latin American soils. Therefore, it is important to establish the baseline of elements in soils as reference values for evaluating potential changes in their concentrations and to be able to define their origins. The objectives of this study are: (1) to show morphological, physical and chemical characteristics of Andisols in the Azuay Andes (Ecuador); (2) to determine the concentrations of six heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) and (3) to evaluate the relationship between metal concentration and soil properties. The study area is located in National Cajas Park in the Paramo area of the Andes at Azuay Province (Ecuador). The geological origin of the National Cajas Park dates back to the Quaternary age. This area is a U-shaped glaciated valley formed over a pre-existing volcanic basement which consists of rhyolite and andesite volcanic tuff. The moraines are covered by discontinuous patches of volcanic ash. The climate is characterized by rather high rainfall, between 1200 to 2000 mm per year, regularly distributed and generally of a low intensity with a yearly average constant temperature (7°C) with high diurnal amplitudes. The paramo is a high altitude neotropical grassland ecosystem, located between the continuous forest border (~3500 m) and the eternal snow line (~5000 m). Seven representative volcanic soil pedons of a toposequence were studied and sampled. All horizons were analysed for physical and chemical properties by standard and specific methods for volcanic soils. Total metal concentrations in soil horizons were determined by ICP-MS spectrometer. The background values were calculated using the 4σ-outlier test. This requires the elimination of

  20. Spatial variability in depth and landscape of heavy metal contents of volcanic soils of the National Cajas Park in the Azuay Andes (Ecuador)

    NASA Astrophysics Data System (ADS)

    Bech, Jaume; Roca, Núria; Boluda, Rafael; Gil, Carlos; Ramos-Miras, Joaquín; Rodríguez, Jose A.

    2015-04-01

    Although the soils in the Azuay Andes are thought to be generally non-contaminated, it is necessary to preserve them from anthropogenic pollution. This area supplies drinking water to Cuenca, the third city of Ecuador. At present, very little information is available on baseline metal concentrations in Latin American soils. Therefore, it is important to establish the baseline of elements in soils as reference values for evaluating potential changes in their concentrations and to be able to define their origins. The objectives of this study are: (1) to show morphological, physical and chemical characteristics of Andisols in the Azuay Andes (Ecuador); (2) to determine the concentrations of six heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) and (3) to evaluate the relationship between metal concentration and soil properties. The study area is located in National Cajas Park in the Paramo area of the Andes at Azuay Province (Ecuador). The geological origin of the National Cajas Park dates back to the Quaternary age. This area is a U-shaped glaciated valley formed over a pre-existing volcanic basement which consists of rhyolite and andesite volcanic tuff. The moraines are covered by discontinuous patches of volcanic ash. The climate is characterized by rather high rainfall, between 1200 to 2000 mm per year, regularly distributed and generally of a low intensity with a yearly average constant temperature (7°C) with high diurnal amplitudes. The paramo is a high altitude neotropical grassland ecosystem, located between the continuous forest border (~3500 m) and the eternal snow line (~5000 m). Seven representative volcanic soil pedons of a toposequence were studied and sampled. All horizons were analysed for physical and chemical properties by standard and specific methods for volcanic soils. Total metal concentrations in soil horizons were determined by ICP-MS spectrometer. The background values were calculated using the 4σ-outlier test. This requires the elimination of

  1. RHOBOT: Radiation hardened robotics

    SciTech Connect

    Bennett, P.C.; Posey, L.D.

    1997-10-01

    A survey of robotic applications in radioactive environments has been conducted, and analysis of robotic system components and their response to the varying types and strengths of radiation has been completed. Two specific robotic systems for accident recovery and nuclear fuel movement have been analyzed in detail for radiation hardness. Finally, a general design approach for radiation-hardened robotics systems has been developed and is presented. This report completes this project which was funded under the Laboratory Directed Research and Development program.

  2. Precipitation hardening austenitic superalloys

    DOEpatents

    Korenko, Michael K.

    1985-01-01

    Precipitation hardening, austenitic type superalloys are described. These alloys contain 0.5 to 1.5 weight percent silicon in combination with about 0.05 to 0.5 weight percent of a post irradiation ductility enhancing agent selected from the group of hafnium, yttrium, lanthanum and scandium, alone or in combination with each other. In addition, when hafnium or yttrium are selected, reductions in irradiation induced swelling have been noted.

  3. Natural Terrestrial Sequestration Potential of Highplains Prairie to Subalpine Forest and Mined-Lands Soils Derived from Weathering of Tertiary Volcanics

    NASA Astrophysics Data System (ADS)

    Yager, D. B.; Burchell, A.; Robinson, R.; Odell, S.; Dick, R. P.; Johnson, C. A.; Hidinger, J.; Rathke, D.

    2007-12-01

    There is now widespread agreement that, if the climate is to be stabilized, then net greenhouse gas emissions must be greatly reduced (IPCC, 2007). The need to reduce net CO2 emissions plus the possible economic and environmental ramifications of not addressing climate change have stimulated important atmospheric carbon mitigation actions, as well as, studies to understand and quantify potential carbon sinks. Soils represent a potentially large and environmentally significant natural carbon reservoir. Increasing the natural terrestrial sequestration potential (NTS) of soils is among the seven, "Sokolow CO2 stabilization wedges' or carbon management strategies needed to thwart doubling of atmospheric CO2. Additionally, high plains to subalpine temperate soils tend to be less susceptible to baseline C pool declines due to global warming than are warmer regions and are important ecosystems in which to quantify soil carbon storage capacity. To examine the potential of magnesium silicate-bearing soils to sequester additional carbon, we sampled 60 high plains prairie to subalpine forest soil horizons derived from weathering of Tertiary-age dacite-andesite- basalt compositions in Colorado, U.S.A.: the San Luis Valley, San Juan Volcanic Field, Grand Mesa, White River- Roan Plateau (Flat Tops), Rocky Mountain National Park, Front Range and propylitically-altered terrain in the western San Juan Volcanic field containing secondary magnesium silicates (chlorite-species). Data for C, N, O (total conc., isotopes), metals, major and trace elements, Hg, S, microbial enzymes (β-glucosidase, arylsulfatase, acid neutralizing capacity (ANC), and 14C radiocarbon dates are reported. Samples demonstrate variable but elevated C relative to average global soil C. In particular, the propylitically-altered rocks have a high instantaneous ANC in laboratory tests (> 20 kg/ton CaCO3 equivalent) and derivative forest soils containing low-temperature charcoal "burn" horizons have high total

  4. Nuclear effects hardened shelters

    NASA Astrophysics Data System (ADS)

    Lindke, Paul

    1990-11-01

    The Houston Fearless 76 Government Projects Group has been actively engaged for more than twenty-five years as a sub-contractor and currently as a prime contractor in the design, manufacture, repair and logistics support of custom mobile ground stations and their equipment accommodations. Other associated products include environmental control units (ECU's), mobilizers for shelters and a variety of mobile power generation units (MPU's). Since 1984, Houston Fearless 76 has designed and manufactured four 8' x 8' x 22' nuclear hardened mobile shelters. These shelters were designed to contain electronic data processing/reduction equipment. One shelter is currently being operated by the Air Force as a Defense Intelligence Agency (DIA) approved and certified Special Corrpartmented Information Facility (SCIF). During the development and manufacturing process of the shelters, we received continual technical assistance and design concept evaluations from Science Applications International Corporation (SAIC) Operations Analysis and Logistics Engineering Division and the Nondestructive Inspection Lab at McClellan AFB. SAIC was originally employed by the Air Force to design the nuclear hardening specifications applied to these shelters. The specific levels of hardening to which the shelters were designed are classified and will not be mentioned during this presentation.

  5. Catastrophic volcanism

    NASA Technical Reports Server (NTRS)

    Lipman, Peter W.

    1988-01-01

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

  6. Nature of organo-mineral particles across density fractions in a volcanic-ash soil: air-drying and sonication effect

    NASA Astrophysics Data System (ADS)

    Wagai, R.; Kajiura, M.; Shirato, Y.; Uchida, M.

    2011-12-01

    Interactions of plant- and microbially-derived organic matter with mineral phases exert significant controls on the stabilization of organic matter (OM) as well as other biogeochemical processes in soil. Density fractionation techniques have been successful in distinguishing soil organo-mineral particles of different degrees of microbial alteration, turnover rate of C, mineral associations. A major methodological difference among the density fractionation studies is the choice of sample pre-treatment. Presence or absence of sonication to disrupt and disperse soil particles and aggregates is a particularly important choice which could significantly alter the nature and distribution of organo-mineral particle and thus the resultant elemental concentration in each density fraction. Soil moisture condition (air-dry vs. field-moist) may also have strong impact especially for soils rich in Fe oxides/hydroxides and/or poorly-crystalline minerals that are prone for (possibly irreversible) aggregation. We thus tested these two effects on the concentration and distribution of C, N, and extractable phases of Fe and Al (by pyrophosphate and acid oxalate) across six density fractions (from <1.6 to >2.5 g/cm^3) using a surface-horizon of volcanic-ash soil which contained large amounts of poorly-crystalline minerals and organo-metal complexes. Compared to field-moist sample, air-drying had little effects on the elemental concentration or distribution across the fractions. In contrast, sonication on air-dried sample at each density cutoff during fractionation process caused significant changes. In addition to well-known increase in low-density material due to the liberation of plant detritus upon aggregate disruption, we found clear increase in C, N, and metals in 2.0-2.3 g/cm^3 fraction, which was largely compensated by the reduction in 1.8-2.0 g/cm^3 and, to a less extent, 2.3-2.5 g/cm^3 particles. Overall, sonication led to the redistribution of C and N by 15-20% and that of

  7. Volcanic soils and landslides: a case study of the island of Ischia (southern Italy) and its relationship with other Campania events

    NASA Astrophysics Data System (ADS)

    Vingiani, S.; Mele, G.; De Mascellis, R.; Terribile, F.; Basile, A.

    2015-06-01

    An integrated investigation was carried out on the volcanic soils involved in the landslide phenomena that occurred in 2006 at Mt. Vezzi on the island of Ischia (southern Italy). Chemical (soil pH, organic carbon content, exchangeable cations and cation exchange capacity, electrical conductivity, Na adsorption ratio and Al, Fe and Si forms), physical (particle and pore size distribution, pore structure), hydrological (soil water retention, saturated and unsaturated hydraulic conductivity), mineralogical and micromorphological analyses were carried out for three soil profiles selected in two of the main head scarps. The studied soils showed a substantial abrupt discontinuity in all the studied properties at the interface with a buried fine ash layer (namely, the 2C horizon), that was only marginally involved in the sliding surface of the landslide phenomena. When compared to the overlying horizons, 2C showed (i) fine grey ash that is almost pumice free, with the silt content increasing by 20 %; (ii) ks values 1 order of magnitude lower; (iii) a pore distribution concentrated into small (15-30 μm modal class) pores characterised by a very low percolation threshold (approximately 15-25 μm); (iv) the presence of expandable clay minerals; and (v) increasing Na content in the exchange complex. Most of these properties indicated that 2C was a lower permeability horizon compared to the overlying ones. Nevertheless, it was possible to assume this interface to be an impeding layer to vertical water fluxes only by the identification of a thin (6.5 mm) finely stratified ash layer, on top of 2C, and of the hydromorphic features (e.g. Fe / Mn concretions) within and on top of the layer. Although Mt. Vezzi's soil environment has many properties in common with those of other Campania debris-mudflows (e.g. high gradient, north-facing slope, similar forestry, and volcanic origin of the parent material), the results of this study suggest a more complex relationship between soil

  8. Practical aspects of systems hardening

    SciTech Connect

    Shepherd, W.J.

    1989-01-01

    Applications of hardening technology in a practical system require a balance between the factors governing affordability, producibility, and survivability of the finished design. Without careful consideration of the top-level system operating constraints, a design engineer may find himself with a survivable but overweight, unproductive, expensive design. This paper explores some lessons learned in applying hardening techniques to several laser communications programs and is intended as an introductory guide to novice designers faced with the task of hardening a space system.

  9. Detection of an organic-non volatile compound in variable-contaminated volcanic soil samples via Time Domain Reflectometry (TDR) technique: Preliminary results

    NASA Astrophysics Data System (ADS)

    comegna, alessandro; coppola, antonio; dragonetti, giovanna; chaali, nesrine; sommella, angelo

    2014-05-01

    Hydrocarbons may be present in soils as non-aqueous phase liquids (NAPLs), which means that these organic compounds, exist as a separate and immiscible phase with respect to water and air commonly present in the soil. NAPLs, which can be accidentally introduced in the environment (for example by waste disposal sites, industrial spills, gasoline stations, etc), constitutes a serious geo-environmental problem, given the toxicity level and the high mobility. Time domain reflectometry (TDR) has became, over several decades, an important technique for water estimation in soils. In order to expand the potentiality of the TDR technique, the main objective of this study is to explore the capacity of dielectric response to detect the presence of NAPLs in volcanic soils. In laboratory, soil samples were oven dried at 105° C and passed through a 2 mm sieve. Known quantities of soil, water and NAPL (corn oil, a non-volatile and non-toxic organic compound) were mixed and repacked into plastic cylinders (16 cm high and 9.5 cm in diameter); in order to obtain forty different volumetric combinations of water and oil (i.e. θfg = θwater + θNAPL), with θNAPL varying from 0.05 to 0.40 by 0.05 cm3/cm3 increments. Data collected were employed to implement a multiphase mixing model which permitted conversion from a dielectric permittivity domain into a θf domain and vice versa. The results of this study show that, the TDR device is NAPL-sensitive, especially for θf values greater than 0.20. Further works will be built on this initial study, concentrating on improving the dielectric response-database, in order to: i) enhancing the model efficiency in terms of NAPL capability detention, and ii) validating the developed TDR interpretation tool with field results.

  10. The surface of Syrtis Major - Composition of the volcanic substrate and mixing with altered dust and soil

    NASA Astrophysics Data System (ADS)

    Mustard, J. F.; Erard, S.; Bibring, J.-P.; Head, J. W.; Hurtrez, S.; Langevin, Y.; Pieters, C. M.; Sotin, C. J.

    1993-02-01

    The study characterizes Syrtis Major, an old, low relief volcanic plateau near the equatorial regions of Mars, on the basis of ISM data in order to characterize the spectral properties of the surface, to identify the major mafic mineralogy of the volcanic materials, and to derive estimates of the chemistry of these minerals. The value and spatial distribution of four primary spectral variables (albedo, continuum slope, wavelength of the ferric-ferrous band minimum, and area of the ferric-ferrous absorption) are mapped and coregistered to Viking digital photomosaics. It is shown that although there is a high degree of overall spectral variability on the plateau, the key indicators of mafic mineralogy are relatively homogeneous.

  11. Multipurpose hardened spacecraft insulation

    NASA Technical Reports Server (NTRS)

    Steimer, Carlos H.

    1990-01-01

    A Multipurpose Hardened Spacecraft Multilayer Insulation (MLI) system was developed and implemented to meet diverse survivability and performance requirements. Within the definition and confines of a MLI assembly (blanket), the design: (1) provides environmental protection from natural and induced nuclear, thermal, and electromagnetic radiation; (2) provides adequate electrostatic discharge protection for a geosynchronous satellite; (3) provides adequate shielding to meet radiated emission needs; and (4) will survive ascent differential pressure loads between enclosed volume and space. The MLI design is described which meets these requirements and design evolution and verification is discussed. The application is for MLI blankets which closeout the area between the laser crosslink subsystem (LCS) equipment and the DSP spacecraft cabin. Ancillary needs were implemented to ease installation at launch facility and to survive ascent acoustic and vibration loads. Directional venting accommodations were also incorporated to avoid contamination of LCS telescope, spacecraft sensors, and second surface mirrors (SSMs).

  12. The fate and transport of RDX, HMX, TNT and DNT in the volcanic soils of Hawaii: a laboratory and modeling study.

    PubMed

    Alavi, Ghasem; Chung, Mel; Lichwa, Joseph; D'Alessio, Matteo; Ray, Chittaranjan

    2011-01-30

    The adsorption and degradation behavior of RDX, HMX, TNT and DNT and the impact of pH, ionic strength and dissolved organic matter on sorption were examined for two volcanic soils of a former military training area on Hawaii Island, Hawaii, USA. The transport of these chemicals in the soil was also studied in small packed columns and simulated using a water-flow and solute-transport model, HYDRUS_1D. The results show that HMX and RDX are both significantly more mobile than TNT and DNT. The adsorbability of the four chemicals was ranked as: RDXRDX>DNT>TNT. No significant trend was observed for the effect of ionic strength, pH and dissolved organic carbon (DOC) on the adsorption of explosive compounds within the concentrations and pH ranges evaluated. The simulation results show that TNT and DNT would not leach beyond a depth of 30cm soil profile whereas a significant amount of HMX and RDX would pass the 30cm depth. It seems that the risk for contamination of groundwater is much higher for both HMX and RDX than for DNT and TNT as the substratum in this area consists of highly permeable lavas. PMID:21087822

  13. Volcanic Ash on Slopes of Karymsky

    NASA Technical Reports Server (NTRS)

    2007-01-01

    A volcanic eruption can produce gases, lava, bombs of rock, volcanic ash, or any combination of these elements. Of the volcanic products that linger on the land, most of us think of hardened lava flows, but volcanic ash can also persist on the landscape. One example of that persistence appeared on Siberia's Kamchatka Peninsula in spring 2007. On March 25, 2007, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite captured this image of the area around the Karymsky Volcano. In this image, volcanic ash from earlier eruptions has settled onto the snowy landscape, leaving dark gray swaths. The ash stains are confined to the south of the volcano's summit, one large stain fanning out toward the southwest, and another toward the east. At first glance, the ash stain toward the east appears to form a semicircle north of the volcano and sweep back east. Only part of this dark shape, however, is actually volcanic ash. Near the coast, the darker color may result from thicker vegetation. Similar darker coloring appears to the south. Volcanic ash is not really ash at all, but tiny, jagged bits of rock and glass. These jagged particles pose serious health risks to humans and animals who might inhale them. Likewise, the ash poses hazards to animals eating plants that have been coated with ash. Because wind can carry volcanic ash thousands of kilometers, it poses a more far-reaching hazard than other volcanic ejecta. Substantial amounts of ash can even affect climate by blocking sunlight. Karymsky is a stratovolcano composed of alternating layers of solidified ash, hardened lava, and volcanic rocks. It is one of many active volcanoes on Russia's Kamchatka Peninsula, which is part of the 'Ring of Fire' around the Pacific Rim. NASA image created by Jesse Allen, using data provided courtesy of the NASA/GSFC/MITI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team.

  14. Assessment of organic matter resistance to biodegradation in volcanic ash soils assisted by automated interpretation of infrared spectra from humic acid and whole soil samples by using partial least squares

    NASA Astrophysics Data System (ADS)

    Hernández, Zulimar; Pérez Trujillo, Juan Pedro; Hernández-Hernández, Sergio Alexander; Almendros, Gonzalo; Sanz, Jesús

    2014-05-01

    From a practical viewpoint, the most interesting possibilities of applying infrared (IR) spectroscopy to soil studies lie on processing IR spectra of whole soil (WS) samples [1] in order to forecast functional descriptors at high organizational levels of the soil system, such as soil C resilience. Currently, there is a discussion on whether the resistance to biodegradation of soil organic matter (SOM) depends on its molecular composition or on environmental interactions between SOM and mineral components, such could be the case with physical encapsulation of particulate SOM or organo-mineral derivatives, e.g., those formed with amorphous oxides [2]. A set of about 200 dependent variables from WS and isolated, ash free, humic acids (HA) [3] was obtained in 30 volcanic ash soils from Tenerife Island (Spain). Soil biogeochemical properties such as SOM, allophane (Alo + 1 /2 Feo), total mineralization coefficient (TMC) or aggregate stability were determined in WS. In addition, structural information on SOM was obtained from the isolated HA fractions by visible spectroscopy and analytical pyrolysis (Py-GC/MS). Aiming to explore the potential of partial least squares regression (PLS) in forecasting soil dependent variables, exclusively using the information extracted from WS and HA IR spectral profiles, data were processed by using ParLeS [4] and Unscrambler programs. Data pre-treatments should be carefully chosen: the most significant PLS models from IR spectra of HA were obtained after second derivative pre-treatment, which prevented effects of intrinsically broadband spectral profiles typical in macromolecular heterogeneous material such as HA. Conversely, when using IR spectra of WS, the best forecasting models were obtained using linear baseline correction and maximum normalization pre-treatment. With WS spectra, the most successful prediction models were obtained for SOM, magnetite, allophane, aggregate stability, clay and total aromatic compounds, whereas the PLS

  15. Wavelet analysis for the study of the relations among soil radon anomalies, volcanic and seismic events: the case of Mt. Etna (Italy)

    NASA Astrophysics Data System (ADS)

    Ferrera, Elisabetta; Giammanco, Salvatore; Cannata, Andrea; Montalto, Placido

    2013-04-01

    From November 2009 to April 2011 soil radon activity was continuously monitored using a Barasol® probe located on the upper NE flank of Mt. Etna volcano, close either to the Piano Provenzana fault or to the NE-Rift. Seismic and volcanological data have been analyzed together with radon data. We also analyzed air and soil temperature, barometric pressure, snow and rain fall data. In order to find possible correlations among the above parameters, and hence to reveal possible anomalies in the radon time-series, we used different statistical methods: i) multivariate linear regression; ii) cross-correlation; iii) coherence analysis through wavelet transform. Multivariate regression indicated a modest influence on soil radon from environmental parameters (R2 = 0.31). When using 100-days time windows, the R2 values showed wide variations in time, reaching their maxima (~0.63-0.66) during summer. Cross-correlation analysis over 100-days moving averages showed that, similar to multivariate linear regression analysis, the summer period is characterised by the best correlation between radon data and environmental parameters. Lastly, the wavelet coherence analysis allowed a multi-resolution coherence analysis of the time series acquired. This approach allows to study the relations among different signals either in time or frequency domain. It confirmed the results of the previous methods, but also allowed to recognize correlations between radon and environmental parameters at different observation scales (e.g., radon activity changed during strong precipitations, but also during anomalous variations of soil temperature uncorrelated with seasonal fluctuations). Our work suggests that in order to make an accurate analysis of the relations among distinct signals it is necessary to use different techniques that give complementary analytical information. In particular, the wavelet analysis showed to be very effective in discriminating radon changes due to environmental influences

  16. Volcanic mesocyclones.

    PubMed

    Chakraborty, Pinaki; Gioia, Gustavo; Kieffer, Susan W

    2009-03-26

    A strong volcanic plume consists of a vertical column of hot gases and dust topped with a horizontal 'umbrella'. The column rises, buoyed by entrained and heated ambient air, reaches the neutral-buoyancy level, then spreads radially to form the umbrella. In classical models of strong volcanic plumes, the plume is assumed to remain always axisymmetric and non-rotating. Here we show that the updraught of the rising column induces a hydrodynamic effect not addressed to date-a 'volcanic mesocyclone'. This volcanic mesocyclone sets the entire plume rotating about its axis, as confirmed by an unprecedented analysis of satellite images from the 1991 eruption of Mount Pinatubo. Destabilized by the rotation, the umbrella loses axial symmetry and becomes lobate in plan view, in accord with satellite records of recent eruptions on Mounts Pinatubo, Manam, Reventador, Okmok, Chaiten and Ruang. The volcanic mesocyclone spawns waterspouts or dust devils, as seen in numerous eruptions, and groups the electric charges about the plume to form the 'lightning sheath' that was so prominent in the recent eruption of Mount Chaiten. The concept of a volcanic mesocyclone provides a unified explanation for a disparate set of poorly understood phenomena in strong volcanic plumes. PMID:19325632

  17. Volcanic Mesocyclones

    NASA Astrophysics Data System (ADS)

    Chakraborty, P.; Gioia, G.; Kieffer, S. W.

    2008-12-01

    A strong volcanic plume is customarily modeled as a cylindrical, rising column topped with an axisymmetric, radially spreading umbrella. In this talk we argue that standard models of strong volcanic plumes are missing a crucial component: a "volcanic mesocyclone" that sets the column rotating about its axis. We show theoretically that the volcanic mesocyclone is induced by the entrainment of air into the rising column, which is set rotating about its vertical axis. The umbrella inherits the rotation of the column, and we show that the rotation of the umbrella can be verified directly for the 1991 eruption of Mount Pinatubo and indirectly for several other eruptions. Once rotating, the umbrella becomes destabilized by centrifugal forces and undergoes an hitherto unknown form of the Rayleigh-Taylor instability. As a result, the edge of the umbrella becomes lobate, as has been observed in numerous satellite records. We also show that the volcanic mesocyclone spawns tornadoes in the form of waterspouts or dustdevils, as seen in numerous eruptions, and modifies the distribution of electric charges about the plume, leading to the formation of lightning sheaths, as seen in the recent eruption of Chaitén. The concept of volcanic mesocyclone allows us to give a unified explanation to a broad set of disparate, poorly understood phenomena in volcanic plumes.

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

    NASA Astrophysics Data System (ADS)

    Ma, Lin

    2015-04-01

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

  19. Planetary Volcanism

    NASA Technical Reports Server (NTRS)

    Antonenko, I.; Head, J. W.; Pieters, C. W.

    1998-01-01

    The final report consists of 10 journal articles concerning Planetary Volcanism. The articles discuss the following topics: (1) lunar stratigraphy; (2) cryptomare thickness measurements; (3) spherical harmonic spectra; (4) late stage activity of volcanoes on Venus; (5) stresses and calderas on Mars; (6) magma reservoir failure; (7) lunar mare basalt volcanism; (8) impact and volcanic glasses in the 79001/2 Core; (9) geology of the lunar regional dark mantle deposits; and (10) factors controlling the depths and sizes of magma reservoirs in Martian volcanoes.

  20. System-Level Radiation Hardening

    NASA Technical Reports Server (NTRS)

    Ladbury, Ray

    2014-01-01

    Although system-level radiation hardening can enable the use of high-performance components and enhance the capabilities of a spacecraft, hardening techniques can be costly and can compromise the very performance designers sought from the high-performance components. Moreover, such techniques often result in a complicated design, especially if several complex commercial microcircuits are used, each posing its own hardening challenges. The latter risk is particularly acute for Commercial-Off-The-Shelf components since high-performance parts (e.g. double-data-rate synchronous dynamic random access memories - DDR SDRAMs) may require other high-performance commercial parts (e.g. processors) to support their operation. For these reasons, it is essential that system-level radiation hardening be a coordinated effort, from setting requirements through testing up to and including validation.

  1. Specific activities of natural rocks and soils at quaternary intraplate volcanism north of Sana’a, Yemen

    PubMed Central

    Harb, Shaban; El-Kamel, Abd El-Hadi; Abbady, Abd El-Bast; Saleh, Imran Issa; El-Mageed, Abdallah Ibrahim Abd

    2012-01-01

    The level of natural radioactivity in rocks and soil of 32 samples collected from locations at North Sana′a in Yemen was measured. Concentrations of radionuclides in rocks and soils samples were determined by gamma-ray spectrometer using high purity germanium (HPGe) detector with specially designed shield. The average radioactivity concentrations of 226Ra, 232Th, 40K were determined and expressed in Bq/kg. The results showed that these radionuclides were present in concentrations of 21.79 ± 3.1, 19.5 ± 2.6 and 399.3 ± 16 Bq/kg, respectively, for rocks. For soil, the corresponding values were 48.2 ± 4.4, 41.7 ± 4.5 and 939.1 ± 36 Bq/kg, respectively. Also, the radiological hazard of the natural radionuclide content, radium equivalent activity, total dose rates, external hazard index and gamma activity concentration index of the (rocks/soils) samples in the area under consideration were calculated. The dose rates at 1 m above the ground from terrestrial sources were 38.39 and 86.89 nGy/h for rocks and surface soil, respectively, which present no significant health hazards to humans. PMID:22363113

  2. Explosive Surface Hardening of Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Kovacs-Coskun, T.

    2016-04-01

    In this study, the effects of explosion hardening on the microstructure and the hardness of austenitic stainless steel have been studied. The optimum explosion hardening technology of austenitic stainless steel was researched. In case of the explosive hardening used new idea mean indirect hardening setup. Austenitic stainless steels have high plasticity and can be easily cold formed. However, during cold processing the hardening phenomena always occurs. Upon the explosion impact, the deformation mechanism indicates a plastic deformation and this deformation induces a phase transformation (martensite). The explosion hardening enhances the mechanical properties of the material, includes the wear resistance and hardness. In case of indirect hardening as function of the setup parameters specifically the flayer plate position the hardening increased differently. It was find a relationship between the explosion hardening setup and the hardening level.

  3. Cyclic Aggradation and Downcutting, Fluvial Response to Volcanic Activity, and Calibration of Soil-Carbonate Stages in the Western Grand Canyon, Arizona

    NASA Astrophysics Data System (ADS)

    Lucchitta, Ivo; Curtis, Garniss H.; Davis, Marie E.; Davis, Sidney W.; Turrin, Brent

    2000-01-01

    In the western Grand Canyon, fluvial terraces and pediment surfaces, both associated with a Pleistocene basalt flow, document Quaternary aggradation and downcutting by the Colorado River, illuminate the river's response to overload and the end of overload, and allow calibration of soil-carbonate stages and determination of downcutting rates. Four downcutting-aggradation cycles are present. Each begins with erosion of older deposits to form a new river channel in which a characteristic suite of deposits is laid down. The current cycle (I) started ∼700 yr B.P. The oldest (IV) includes the 603,000 ± 8000 to 524,000 ± 7000 yr Black Ledge basalt flow, emplaced when the river channel was ∼30 m higher than it is now. The flow is overlain by basalt-cobble gravel and basalt sand. Soils reach the stage V level of carbonate development. Calibrated ages for soil stages are Stage V, ∼525,000 yr; stage IV, <525,000 yr, ≥250,000 yr; stage III, <250,000 yr, ≥100,000 yr. The monolithologic basalt sand beds represent overloading by volcanic ash produced by an eruption 30-50 km upstream. The basalt-cobble beds signal breaching and rapid destruction of lava dams and erosion of flows. These deposits show that the Colorado River responds to overload by aggrading vigorously during the overload and then downcutting equally vigorously when the overload ends. The overall downcutting rate for the interval studied is 1.6 cm/1000 yr, much lower than rates upstream. The current downcutting rate, 11-14 m/1000 yr, likely is a response both to the end of late Pleistocene and early Holocene overload and to the reduction of sediment supply caused by Glen Canyon Dam.

  4. Cyclic aggradation and downcutting, fluvial response to volcanic activity, and calibration of soil-carbonate stages in the western Grand Canyon, Arizona

    USGS Publications Warehouse

    Lucchitta, Ivo; Curtis, Garniss H.; Davis, Marie E.; Davis, Sidney W.; Turrin, Brent

    2000-01-01

    In the western Grand Canyon, fluvial terraces and pediment surfaces, both associated with a Pleistocene basalt flow, document Quaternary aggradation and downcutting by the Colorado River, illuminate the river's response to overload and the end of overload, and allow calibration of soil-carbonate stages and determination of downcutting rates. Four downcutting-aggradation cycles are present. Each begins with erosion of older deposits to form a new river channel in which a characteristic suite of deposits is laid down. The current cycle (I) started ~700 yr B.P. The oldest (IV) includes the 603,000 ± 8000 to 524,000 ± 7000 yr Black Ledge basalt flow, emplaced when the river channel was ~30 m higher than it is now. The flow is overlain by basalt-cobble gravel and basalt sand. Soils reach the stage V level of carbonate development. Calibrated ages for soil stages are Stage V, ~525,000 yr; stage IV, <525,000 yr, ≥250,000 yr; stage III, <250,000 yr, ≥100,000 yr. The monolithologic basalt sand beds represent overloading by volcanic ash produced by an eruption 30-50 km upstream. The basalt-cobble beds signal breaching and rapid destruction of lava dams and erosion of flows. These deposits show that the Colorado River responds to overload by aggrading vigorously during the overload and then downcutting equally vigorously when the overload ends. The overall downcutting rate for the interval studied is 1.6 cm/1000 yr, much lower than rates upstream. The current downcutting rate, 11-14 m/1000 yr, likely is a response both to the end of late Pleistocene and early Holocene overload and to the reduction of sediment supply caused by Glen Canyon Dam.

  5. Sensitivity to volcanic field boundary

    NASA Astrophysics Data System (ADS)

    Runge, Melody; Bebbington, Mark; Cronin, Shane; Lindsay, Jan; Rashad Moufti, Mohammed

    2016-04-01

    Volcanic hazard analyses are desirable where there is potential for future volcanic activity to affect a proximal population. This is frequently the case for volcanic fields (regions of distributed volcanism) where low eruption rates, fertile soil, and attractive landscapes draw populations to live close by. Forecasting future activity in volcanic fields almost invariably uses spatial or spatio-temporal point processes with model selection and development based on exploratory analyses of previous eruption data. For identifiability reasons, spatio-temporal processes, and practically also spatial processes, the definition of a spatial region is required to which volcanism is confined. However, due to the complex and predominantly unknown sub-surface processes driving volcanic eruptions, definition of a region based solely on geological information is currently impossible. Thus, the current approach is to fit a shape to the known previous eruption sites. The class of boundary shape is an unavoidable subjective decision taken by the forecaster that is often overlooked during subsequent analysis of results. This study shows the substantial effect that this choice may have on even the simplest exploratory methods for hazard forecasting, illustrated using four commonly used exploratory statistical methods and two very different regions: the Auckland Volcanic Field, New Zealand, and Harrat Rahat, Kingdom of Saudi Arabia. For Harrat Rahat, sensitivity of results to boundary definition is substantial. For the Auckland Volcanic Field, the range of options resulted in similar shapes, nevertheless, some of the statistical tests still showed substantial variation in results. This work highlights the fact that when carrying out any hazard analysis on volcanic fields, it is vital to specify how the volcanic field boundary has been defined, assess the sensitivity of boundary choice, and to carry these assumptions and related uncertainties through to estimates of future activity and

  6. Using Uranium-Series Isotopes to Quantify Volcanic Soil Formation Rates Under a Tropical Climate: Basse-Terre, Guadeloupe

    NASA Astrophysics Data System (ADS)

    Pereyra, Y.; Ma, L.; Sak, P. B.; Gaillardet, J.; Buss, H. L.; Brantley, S. L.

    2014-12-01

    U-series isotopes fractionate during chemical weathering and their activity ratios have been used to determine timescales and rates of soil formation. Such soil formation rates are measured at soil profile scale and provide an important link to compare chemical weathering rates measured across different spatial scales. We analyzed U-series isotope compositions in a ~12m deep soil profile in Basse-Terre Island of French Guadeloupe. The tropical Bras David watershed is developed on andesitic pyroclastic flows. Field observations have shown heterogeneity in color and texture in this profile. However, major element chemistry and mineralogy show some general depth trends. First, Al, Fe, and Ti show a depletion profile relative to Th from 12m to 4m depth, an addition from 4m to 2m, and depletion from 2m to the surface. Second, mobile elements such as Ca, Mg, and Sr have undergone intensive weathering, therefore show almost complete depletion even in the deep profile, and an addition profile near the surface. This addition trend is most likely related to atmospheric dust and marine aerosol signatures. Finally, K, Mn, and Si show a partial depletion profile at depth. The main minerals present throughout the soil profile are halloysite and gibbsite. 238U/232Th ratios in this profile ranged from 0.374 to 1.696, while the 230Th/232Th ratios ranged from 0.367 to 1.701. A decrease of (238U/232Th) in the deep soil profile from 12m to 4m depth is observed, and an increase in the shallow profile from 4m to the surface. The (230Th /232Th) ratios showed a similar trend as (238U/232Th). Marine aerosols and atmospheric dust are responsible for the addition of U in shallow soils while intensive chemical weathering is responsible for the loss of U at depth. U-series chemical weathering model suggests that the weathering duration from 12m to 4m depth is about 250kyr, with a weathering advancing rate of ~30 m/Ma. The rate is also about one order of magnitude lower than the weathering rate

  7. Soil and river contamination patterns of chlordecone in a tropical volcanic catchment in the French West Indies (Guadeloupe).

    PubMed

    Crabit, A; Cattan, P; Colin, F; Voltz, M

    2016-05-01

    The aim of this study was to identify primary flow paths involved in the chlordecone (CLD) river contamination and quantify the CLD fluxes to assess CLD pollution levels and duration according to a typical catchment of the banana cropping area in the French Indies (Guadeloupe): the Pérou Catchment (12 km(2)) characterized by heavy rainfall (5686 mm year(-1)). Three sub-catchments (SC1, SC2 and SC3) were studied during the hydrological year 2009-2010: a pedological survey combined with a spatialized hydrochemical approach was conducted. The average soil concentration is higher in the Pérou Catchment (3400 μg kg(-1)) than in the entire banana cropping area in Guadeloupe (2100 μg kg(-1)). The results showed that CLD stocks in soils vary largely among soil types and farming systems: the weakest stocks are located upstream in SC1 (5 kg ha(-1)), where a majority of the area is non-cultivated; medium stocks are located in Nitisols downstream in SC3 (9 kg ha(-1)); and the greatest stocks are observed in SC2 on Andosols (12 kg ha(-1)) characterized by large farms. The annual water balance and the hydro-chemical analysis revealed that the three sub-catchments exhibited different behaviors. Pérou River contamination was high during low flows, which highlighted that contamination primarily originated from groundwater contributions. The results showed that only a small part of the catchment (SC2), contributing little to the water flow, comprises a major CLD contribution, which is in agreement with the highly contaminated andosol soils observed there. Another significant result considers that at least 50 years would be required to export the totality of the actual CLD soil stocks retained in the topsoil layer. The actual time for soil remediation will however be much longer considering (i) the necessary time for the chlordecone to percolate and be stored in the shallow aquifers and (ii) its travel time to reach the river. PMID:27039897

  8. High-silica /greater than 60%/ lunar glasses in an Apollo 14 soil sample - Evidence for silicic lunar volcanism

    NASA Technical Reports Server (NTRS)

    Glass, B. P.

    1976-01-01

    The major-element compositions of 93 low-specific-gravity (less than 2.60) high-silica (greater than 60%) glass particles from a sample of lunar fines (14259,20) were determined by electron microprobe analyses. The size, shape, abundance, mineralogy, and major-element composition of more than 60% of the high-silica glasses is consistent with their being fragments of interstitial glass from mare basalts. However, one group of 30 glasses with between 72% and 78% SiO2 and an average of approximately 2.6% FeO can be distinguished from other high-silica glasses both chemically and petrographically. Glass particles with this composition do not contain crystalline inclusions and are fairly homogeneous not only within a single particle but also from particle to particle. The chemistry and petrology of these glasses suggest that they are not fragments of interstitial glass or shock-melted particles from a 'granitic' source rock. Rather, the homogeneity and lack of crystalline inclusions suggest that this group of high-silica glasses was the product of lunar acidic volcanism.

  9. Effect of dissolved organic carbon on the transport and attachment behaviors of Cryptosporidium parvum oocysts and carboxylate-modified microspheres advected through temperate humic and tropical volcanic agricultural soil.

    PubMed

    Mohanram, Arvind; Ray, Chittaranjan; Metge, David W; Barber, Larry B; Ryan, Joseph N; Harvey, Ronald W

    2012-02-21

    Transport of Cryptosporidium parvum oocysts and microspheres in two disparate (a clay- and Fe-rich, volcanic and a temperate, humic) agricultural soils were studied in the presence and absence of 100 mg L(-1) of sodium dodecyl benzene sulfonate (SDBS), and Suwannee River Humic Acid (SRHA) at pH 5.0-6.0. Transport of carboxylate-modified, 1.8 μm microspheres in soil columns was highly sensitive to the nature of the dissolved organic carbon (DOC), whereas oocysts transport was more affected by soil mineralogy. SDBS increased transport of microspheres from 48% to 87% through the tropical soil and from 43% to 93% in temperate soil. In contrast, SRHA reduced transport of microspheres from 48% to 28% in tropical soil and from 43% to 16% in temperate soil. SDBS also increased oocysts transport through the temperate soil 5-fold, whereas no oocyst transport was detected in tropical soil. SRHA had only a nominal effect in increasing oocysts transport in tropical soil, but caused a 6-fold increase in transport through the temperate soil. Amendments of only 4 mg L(-1) SRHA and SDBS decreased oocyst hydrophobicity from 66% to 20% and from 66% to 5%, respectively. However, SDBS increased microsphere hydrophobicity from 16% to 33%. Soil fines, which includes clays, and SRHA, both caused the oocysts zeta potential (ζ) to become more negative, but caused the highly hydrophilic microspheres to become less negatively charged. The disparate behaviors of the two colloids in the presence of an ionic surfactant and natural organic matter suggest that microspheres may not be suitable surrogates for oocysts in certain types of soils. These results indicate that whether or not DOC inhibits or promotes transport of oocysts and microspheres in agricultural soils and by how much, depends not only on the surface characteristics of the colloid, but the nature of the DOC and the soil mineralogy. PMID:21711011

  10. Erosion Rates of Volcanic-ash Derived Soils in the Blue Mountains of Eastern Oregon, USA: A Comparison Across Sales in Space and Time.

    NASA Astrophysics Data System (ADS)

    Wondzell, S. M.; Clifton, C. F.; Harris, R. M.; Ritchie, J. C.

    2007-12-01

    We examined present day rates of erosion in the Blue Mountains of eastern Oregon to quantify background erosion rates to provide standards for assessing possible accelerated rates of erosion resulting from wild fire or from land-management activities such as prescribed fire. The Skookum Creek watersheds, where stream discharge and sediment yield have been recorded continuously since the watersheds were gauged in 1992, provided a watershed-scale estimate of erosion rates. We installed hillslope erosion plots on north- and south- facing slopes within the watersheds in 2002 and collected data for three years to estimate short-term, hillslope- scale erosion rates. We also collected soil samples and analyzed them for 137Cs to get a 40-yr time- integrated estimate of hillslope erosion rates. Our results showed large differences between whole-watershed sediment yields and hillslope erosion rates measured from plots, suggesting that episodic processes dominated sediment production and transport and therefore controlled watershed-scale sediment budgets. At the hillslope-scale, short-term erosion resulted primarily from digging by small mammals and trampling by elk. Visual observations at the plots suggested that annual down-slope sediment movement was usually less than one meter. There were no significant difference among slope positions, but erosion rates were significantly higher on south-facing aspects and positively correlated to the amount of bare ground. In contrast, the 137Cs data suggested that erosion rates differed with slope position. Higher erosion rates were measured in toe- and mid-slope positions, with little erosion occurring on upper slopes and ridge tops. We examine these results in light of the present-day pattern of surface soils resulting from redistribution of volcanic ash from upper- slope to lower-slope positions and the effects of disturbance, including wildfire and the preferential grazing of riparian and lower-slope positions by domestic livestock.

  11. The chemical structure of highly aromatic humic acids in three volcanic ash soils as determined by dipolar dephasing NMR studies

    USGS Publications Warehouse

    Hatcher, P.G.; Schnitzer, M.; Vassallo, A.M.; Wilson, M.A.

    1989-01-01

    Dipolar dephasing 13C NMR studies of three highly aromatic humic acids, one from a modern soil and two from paleosols, have permitted the determination of the degree of aromatic substitution. From these data and the normal solid-state 13C NMR data we have been able to develop a model for the average chemical structure of these humic acids that generally correlates well with permanganate oxidation data. The models depict these humic acids as benzene di- and tricarboxylic acids interconnected by biphenyl linkages. An increasing degree of substitution is observed with increasing geologic age. These structures may be characteristic of the resistant aromatic part of the "core" of humic substances that survives degradation. ?? 1989.

  12. Experiments and Spectral Studies of Martian Volcanic Rocks: Implications for the Origin of Pathfinder Rocks and Soils

    NASA Technical Reports Server (NTRS)

    Rutherford, Malcolm J.; Mustard, Jack; Weitz, Catherine

    2002-01-01

    The composition and spectral properties of the Mars Pathfinder rocks and soils together with the identification of basaltic and andesitic Mars terrains based on Thermal Emission Spectrometer (TES) data raised interesting questions regarding the nature and origin of Mars surface rocks. We have investigated the following questions: (1) are the Pathfinder rocks igneous and is it possible these rocks could have formed by known igneous processes, such as equilibrium or fractional crystallization, operating within SNC magmas known to exist on Mars? If it is possible, what P (depth) and PH2O conditions are required? (2) whether TES-based interpretations of plagioclase-rich basalt and andesitic terrains in the south and north regions of Mars respectively are unique. Are the surface compositions of these regions plagioclase-rich, possibly indicating the presence of old AI-rich crust of Mars, or are the spectra being affected by something like surface weathering processes that might determine the spectral pyroxene to plagioclase ratio?

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

    PubMed

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

    2016-01-01

    The aim of this study was to evaluate the influence of urea fertilizer and pH on the sorption process of two acidic herbicides, flumetsulam (2',6'-difluoro-5-methyl[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonanilide) and MCPA (4-chloro--tolyloxyacetic acid), on an Andisol. Urea reduced the adsorption of MCPA but not that of flumetsulam. The Freundlich parameter of MCPA decreased from 8.5 to 5.1 mg L kg. This finding could be attributed to an increase in dissolved organic C due to an initial increase in soil pH for urea application. The higher acidic character of MCPA compared with that of flumetsulam produced a greater hydrolysis of urea, leading to a further pH increase. A marked effect of pH on the adsorption of both herbicides was observed. The organic C distribution coefficient () values for flumetsulam were in the range of 74 to 10 L kg, while those of MCPA were in the range of 208 to 45 L kg. In the kinetic studies, the pseudo-second-order model appeared to fit the data best ( > 0.994). The initial adsorption rates () ranged from 20.00 to 4.59 mg kg h for flumetsulam and from 125.00 to 25.60 mg kg hfor MCPA. Both herbicides were adsorbed rapidly during the first stage of the sorption process, and the rates of sorption were dependent on pH. The application of the Elovich and Weber-Morris models led us to conclude that mass transfer through the boundary layer and, to a lesser degree, intraparticle diffusion were influenced by the chemical character of the herbicide. These results suggest that urea application could increase leaching of acid herbicides in soils. PMID:26828188

  14. Life on the Hardened Border

    ERIC Educational Resources Information Center

    Miller, Bruce Granville

    2012-01-01

    The many Coast Salish groups distributed on both sides of the United States-Canada border on the Pacific coast today face significant obstacles to cross the international border, and in some cases are denied passage or intimidated into not attempting to cross. The current situation regarding travel by Aboriginal people reflects the "hardening" of…

  15. Onycholysis induced by nail hardener.

    PubMed

    Helsing, Per; Austad, Joar; Talberg, Hans Jørgen

    2007-10-01

    Nail hardeners appeared in the market during the 1960s. They were basically solutions of formaldehyde. The first adverse effects were published in 1966 (1). Reactions were onycholysis, chromonychia, subungual haemorrhage, and hyperkeratosis. Onycholysis may be non-inflammatory or inflammatory, and is accompanied by throbbing pain. Inflammatory reactions are followed by paronychia and occasional dermatitis on the digital pulpa. PMID:17868227

  16. Herbaspirillum canariense sp. nov., Herbaspirillum aurantiacum sp. nov. and Herbaspirillum soli sp. nov., isolated from volcanic mountain soil, and emended description of the genus Herbaspirillum.

    PubMed

    Carro, Lorena; Rivas, Raúl; León-Barrios, Milagros; González-Tirante, María; Velázquez, Encarna; Valverde, Angel

    2012-06-01

    Three Gram-negative, motile and slightly curved rod-shaped bacteria, strains SUEMI03(T), SUEMI08(T) and SUEMI10(T), were isolated from an old volcanic mountain soil on Tenerife (Canary Islands). The three strains were related phylogenetically to Herbaspirillum seropedicae. 16S rRNA gene sequence similarity was 99.2-99.6 % among strains SUEMI03(T), SUEMI08(T) and SUEMI10(T), which presented 97.5, 97.8 and 97.7 % identity, respectively, with respect to H. seropedicae DSM 6445(T). The three strains grew optimally in TSB at 28 °C and contained summed features 3 (C(16:1)ω6c and/or C(16:1)ω7c) and 8 (C(18:1)ω6c and/or C(18:1)ω7c) and C(16:0) as major cellular fatty acids. The DNA G+C contents of strains SUEMI03(T), SUEMI08(T) and SUEMI10(T) were 61.6, 60.4 and 61.9 mol%, respectively. Strains SUEMI03(T), SUEMI08(T) and SUEMI10(T) presented less than 60 % interstrain DNA relatedness and less than 30 % relatedness with respect to H. seropedicae DSM 6445(T). In spite of their common geographical origin, the three strains isolated in this study presented several phenotypic differences, presenting phenotypic profiles highly divergent from that of H. seropedicae. Therefore, we propose that the strains isolated in this study represent three novel species of the genus Herbaspirillum, named Herbaspirillum canariense sp. nov. (type strain SUEMI03(T) = LMG 26151(T) = CECT 7838(T)), Herbaspirillum aurantiacum sp. nov. (type strain SUEMI08(T) = LMG 26150(T) = CECT 7839(T)) and Herbaspirillum soli sp. nov. (type strain SUEMI10(T) = LMG 26149(T) = CECT 7840(T)). PMID:21788228

  17. Scintillation-Hardened GPS Receiver

    NASA Technical Reports Server (NTRS)

    Stephens, Donald R.

    2015-01-01

    CommLargo, Inc., has developed a scintillation-hardened Global Positioning System (GPS) receiver that improves reliability for low-orbit missions and complies with NASA's Space Telecommunications Radio System (STRS) architecture standards. A software-defined radio (SDR) implementation allows a single hardware element to function as either a conventional radio or as a GPS receiver, providing backup and redundancy for platforms such as the International Space Station (ISS) and high-value remote sensing platforms. The innovation's flexible SDR implementation reduces cost, weight, and power requirements. Scintillation hardening improves mission reliability and variability. In Phase I, CommLargo refactored an open-source GPS software package with Kalman filter-based tracking loops to improve performance during scintillation and also demonstrated improved navigation during a geomagnetic storm. In Phase II, the company generated a new field-programmable gate array (FPGA)-based GPS waveform to demonstrate on NASA's Space Communication and Navigation (SCaN) test bed.

  18. Surface Fatigue Resistance with Induction Hardening

    NASA Technical Reports Server (NTRS)

    Townsend, Dennis; Turza, Alan; Chapman, Mike

    1996-01-01

    Induction hardening has been used for some years to harden the surface and improve the strength and service life of gears and other components. Many applications that employ induction hardening require a relatively long time to finish the hardening process and controlling the hardness of the surface layer and its depth often was a problem. Other surface hardening methods, ie., carbonizing, take a very long time and tend to cause deformations of the toothing, whose elimination requires supplementary finishing work. In double-frequency induction hardening, one uses a low frequency for the preheating of the toothed wheel and a much higher frequency for the purpose of rapidly heating the surface by way of surface hardening.

  19. Volcanic Catastrophes

    NASA Astrophysics Data System (ADS)

    Eichelberger, J. C.

    2003-12-01

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

  20. Volcanic features of Io

    USGS Publications Warehouse

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

    1979-01-01

    Volcanic activity is apparently higher on Io than on any other body in the Solar System. Its volcanic landforms can be compared with features on Earth to indicate the type of volcanism present on Io. ?? 1979 Nature Publishing Group.

  1. DISPERSION HARDENING OF URANIUM METAL

    DOEpatents

    Arbiter, W.

    1963-01-15

    A method of hardening U metal involves the forming of a fine dispersion of UO/sub 2/. This method consists of first hydriding the U to form a finely divided powder and then exposing the powder to a very dilute O gas in an inert atmosphere under such pressure and temperature conditions as to cause a thin oxide film to coat each particle of the U hydride, The oxide skin prevents agglomeration of the particles as the remaining H is removed, thus preserving the small particle size. The oxide skin coatings remain as an oxide dispersion. The resulting product may be workhardened to improve its physical characteristics. (AEC)

  2. Kimberlite Volcanism

    NASA Astrophysics Data System (ADS)

    Sparks, R. S. J.

    2013-05-01

    Kimberlite magmas are volatile-rich, silica-poor ultrabasic magmas originating as small-degree mantle melts at depths of 150 km or greater. Alteration and entrained xenoliths obscure their original magma chemistry and properties. Kimberlite magmas decrease temperature by a few hundred degrees during ascent. Changes of melt composition can result as a function of assimilation. Stalling of kimberlite can result in fractional crystallization, loss of xenocrysts, and loss of volatiles. Multiple pulses of kimberlite magmas form several distinct geological units in the same pipe or intrusion. Kimberlite pipes form by explosive disruption and deformation of country rocks. Confinement in a pipe introduces new processes such as fluidization, dynamic sintering, and intense mixing between volcanic jets and concentrated trapped mixtures. Occurrences of extravent and crater-fill lithofacies indicate that kimberlite eruptions generate eruptive products that are similar to those produced by common magma types. Alteration is largely attributed to hydrothermal systems, diagenesis, and weathering involving external water.

  3. Energy-Efficient Thermomagnetic and Induction Hardening

    SciTech Connect

    2009-02-01

    This factsheet describes a research project that will develop and test a hybrid thermomagnetic and induction hardening technology to replace conventional heat treatment processes in forging applications.

  4. Radiation Hardened Electronics for Extreme Environments

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Watson, Michael D.

    2007-01-01

    The Radiation Hardened Electronics for Space Environments (RHESE) project consists of a series of tasks designed to develop and mature a broad spectrum of radiation hardened and low temperature electronics technologies. Three approaches are being taken to address radiation hardening: improved material hardness, design techniques to improve radiation tolerance, and software methods to improve radiation tolerance. Within these approaches various technology products are being addressed including Field Programmable Gate Arrays (FPGA), Field Programmable Analog Arrays (FPAA), MEMS Serial Processors, Reconfigurable Processors, and Parallel Processors. In addition to radiation hardening, low temperature extremes are addressed with a focus on material and design approaches.

  5. COSMIC-RAY HELIUM HARDENING

    SciTech Connect

    Ohira, Yutaka; Ioka, Kunihito

    2011-03-01

    Recent observations by the CREAM and ATIC-2 experiments suggest that (1) the spectrum of cosmic-ray (CR) helium is harder than that of CR protons below the knee energy, 10{sup 15}eV, and (2) all CR spectra become hard at {approx}>10{sup 11}eV nucleon{sup -1}. We propose a new idea, that higher energy CRs are generated in a more helium-rich region, to explain the hardening without introducing different sources for CR helium. The helium-to-proton ratio at {approx}100 TeV exceeds the Big Bang abundance Y = 0.25 by several times, and the different spectrum is not reproduced within the diffusive shock acceleration theory. We argue that CRs are produced in a chemically enriched region, such as a superbubble, and the outward-decreasing abundance naturally leads to the hard spectrum of CR helium if CRs escape from the supernova remnant shock in an energy-dependent way. We provide a simple analytical spectrum that also fits well the hardening due to the decreasing Mach number in the hot superbubble with {approx}10{sup 6} K. Our model predicts hard and concave spectra for heavier CR elements.

  6. Synopsis of volcanic stratigraphy

    NASA Technical Reports Server (NTRS)

    Hammond, P. E.

    1974-01-01

    Volcanic stratigraphic units are mappable layered units composed of volcanic rocks that are formed on land (subaerially) or under water (subaqueously) by volcanic processes. At least ten different types of volcanic stratigraphic units are recognized. The characteristics for each are discussed briefly and some typical examples are illustrated by diagrams to show their salient features.

  7. Improved hardening theory for cyclic plasticity.

    NASA Technical Reports Server (NTRS)

    Vos, R. G.; Armstrong, W. H.

    1973-01-01

    A temperature-dependent version of a combined hardening theory, including isotropic and kinematic hardening, is presented within the framework of recent plasticity formulations. This theory has been found to be especially useful in finite-element analysis of aerospace vehicle engines under conditions of large plastic strain and low-cycle fatigue.

  8. Volcanic sulfur

    NASA Astrophysics Data System (ADS)

    Hobbs, Peter V.

    Although I may be overly demanding in expecting a member of the Eos staff to be familiar with recent articles in AGU journals, I am moved to make a mild protest concerning attribution in the “Volcanic Sulfur Dynamics” news item by Mario E. Godinez (Eos, June 14, 1983, p. 411).Since the news story stated that an important result of the RAVE experiment was to estimate the SO2 flux from Mount St. Helens on just one day, I must point out that both my research group and USGS scientists have monitored the emissions from Mount St. Helens and estimated SO2 (and other) fluxes over extended periods of time. Our results, which were based on in situ airborne measurements carried out over a period of a year, include estimates of the flux rates of SO2, H2S, H2O, sulfates, halides, and various other particles, prior to, during, and after the explosive eruption of Mount St. Helens on May 18, 1980 [Hobbs et al., 1983]. The USGS measurements, which are made remotely through use of an airborne correlation spectrometer, also commenced in 1980 a n d have provided data several times a week since that time [Casadevall et al., 1981]. We have also estimated the fluxes of various materials (including SO2) from eight other volcanos [Radke et al.., 1976; Stith et al.., 1978; Radke, 1982].

  9. Kinematic hardening of a porous limestone

    NASA Astrophysics Data System (ADS)

    Cheatham, J. B.; Allen, M. B.; Celle, C. C.

    1984-10-01

    A concept for a kinematic hardening yield surface in stress space for Cordova Cream limestone (Austin Chalk) developed by Celle and Cheatham (1981) has been improved using Ziegler's modification of Prager's hardening rule (Ziegler, 1959). Data to date agree with the formulated concepts. It is shown how kinematic hardening can be used to approximate the yield surface for a wide range of stress states past the initial yield surface. The particular difficulty of identifying the yield surface under conditions of unloading or extension is noted. A yield condition and hardening rule which account for the strain induced anisotropy in Cordova Cream Limestone were developed. Although the actual yield surface appears to involve some change of size and shape, it is concluded that true kinematic hardening provides a basis for engineering calculations.

  10. Challenges in hardening technologies using shallow-trench isolation

    SciTech Connect

    Shaneyfelt, M.R.; Dodd, P.E.; Draper, B.L.; Flores, R.S.

    1998-02-01

    Challenges related to radiation hardening CMOS technologies with shallow-trench isolation are explored. Results show that trench hardening can be more difficult than simply replacing the trench isolation oxide with a hardened field oxide.

  11. Volcanic hazard management in dispersed volcanism areas

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  12. Cyclic hardening mechanisms in Nimonic 80A

    NASA Technical Reports Server (NTRS)

    Lerch, B. A.; Gerold, V.

    1987-01-01

    A nickel base superalloy was fatigued under constant plastic strain range control. The hardening response was investigated as a function of plastic strain range and particle size of the gamma prime phase. Hardening was found to be a function of the slip band spacing. Numerous measurements of the slip band spacing and other statistical data on the slip band structures were obtained. Interactions between intersecting slip systems were shown to influence hardening. A Petch-Hall model was found to describe best this relationship between the response stress and the slip band spacing.

  13. Fatigue hardening in niobium single crystals.

    NASA Technical Reports Server (NTRS)

    Doner, M.; Diprimio, J. C.; Salkovitz, E. I.

    1973-01-01

    Nb single crystals of various orientations were cyclically deformed in tension-compression under strain control. At low strain amplitudes all crystals oriented for single slip and some oriented for multiple slip showed a two stage hardening. When present, the first stage was characterized with almost no cyclic work hardening. The rate of hardening in the second stage increased with strain amplitude and the amount of secondary slip. In crystals oriented for single slip kink bands developed on their side faces during rapid hardening stage which resulted in considerable amount of asterism in Laue spots. A cyclic stress-strain curve independent of prior history was found to exist which was also independent of crystal orientation. Furthermore, this curve differed only slightly from that of polycrystalline Nb obtained from data in literature.

  14. Alloy solution hardening with solute pairs

    DOEpatents

    Mitchell, John W.

    1976-08-24

    Solution hardened alloys are formed by using at least two solutes which form associated solute pairs in the solvent metal lattice. Copper containing equal atomic percentages of aluminum and palladium is an example.

  15. Process for hardening the surface of polymers

    DOEpatents

    Mansur, L.K.; Lee, E.H.

    1992-07-14

    Hard surfaced polymers and the method for making them is generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface and improved wear resistance. 1 figure.

  16. Process for hardening the surface of polymers

    DOEpatents

    Mansur, Louis K.; Lee, Eal H.

    1992-01-01

    Hard surfaced polymers and the method for making them is generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface and improved wear resistance.

  17. Electrification of volcanic plumes

    NASA Astrophysics Data System (ADS)

    Mather, T. A.; Harrison, R. G.

    We present a review of our current understanding of the electrification of volcanic plumes on Earth and discuss the possible implications both in terms of the volcanic monitoring, early Earth evolution and planetary exploration. Volcanic lightning is perhaps the most spectacular consequence of the electrification of volcanic plumes. Recent years have seen volcanic lightning detection used as part of a portfolio of developing techniques to monitor volcanic eruptions. Remote sensing measurement techniques have been used to monitor volcanic lightning, but surface observations of the atmospheric electric Potential Gradient (PG) and the charge carried on volcanic ash also show that many volcanic plumes, whilst not sufficiently electrified to produce lightning, have detectable electrification exceeding that of their surrounding environment. Electrification has only been observed associated with ash-rich explosive plumes, but there is little evidence that the composition of the ash is critical to its occurrence. Different conceptual theories for charge generation and separation in volcanic plumes have been developed to explain the disparate observations obtained, but the ash fragmentation mechanism appears to be a key parameter. It is unclear which mechanisms or combinations of electrification mechanisms dominate in different circumstances. Electrostatic forces play an important role in modulating the dry fall-out of ash from a volcanic plume. Beyond the local electrification of plumes, the higher stratospheric particle concentrations following a large explosive eruption may affect the global atmospheric electrical circuit. It is possible that this might present another, if minor, way by which large volcanic eruptions affect global climate. Volcanic lightning has been implicated in a number of ways in the origin of life on Earth, and may also exist in other planetary atmospheres where measurements of its occurrence might give clues about the nature of volcanism on other

  18. Decline in Radiation Hardened Microcircuit Infrastructure

    NASA Technical Reports Server (NTRS)

    LaBel, Kenneth A.

    2015-01-01

    Two areas of radiation hardened microcircuit infrastructure will be discussed: 1) The availability and performance of radiation hardened microcircuits, and, and 2) The access to radiation test facilities primarily for proton single event effects (SEE) testing. Other areas not discussed, but are a concern include: The challenge for maintaining radiation effects tool access for assurance purposes, and, the access to radiation test facilities primarily for heavy ion single event effects (SEE) testing. Status and implications will be discussed for each area.

  19. Experience in calibrating the double-hardening constitutive model Monot

    NASA Astrophysics Data System (ADS)

    Hicks, M. A.

    2003-11-01

    The Monot double-hardening soil model has previously been implemented within a general purpose finite element algorithm, and used in the analysis of numerous practical problems. This paper reviews experience gained in calibrating Monot to laboratory data and demonstrates how the calibration process may be simplified without detriment to the range of behaviours modelled. It describes Monot's principal features, important governing equations and various calibration methods, including strategies for overconsolidated, cemented and cohesive soils. Based on a critical review of over 30 previous Monot calibrations, for sands and other geomaterials, trends in parameter values have been identified, enabling parameters to be categorized according to their relative importance. It is shown that, for most practical purposes, a maximum of only 5 parameters is needed; for the remaining parameters, standard default values are suggested. Hence, the advanced stress-strain modelling offered by Monot is attainable with a similar number of parameters as would be needed for some simpler, less versatile, models. Copyright

  20. Long-term pollution by chlordecone of tropical volcanic soils in the French West Indies: a simple leaching model accounts for current residue.

    PubMed

    Cabidoche, Y-M; Achard, R; Cattan, P; Clermont-Dauphin, C; Massat, F; Sansoulet, J

    2009-05-01

    Chlordecone was applied between 1972 and 1993 in banana fields of the French West Indies. This resulted in long-term pollution of soils and contamination of waters, aquatic biota, and crops. To assess pollution level and duration according to soil type, WISORCH, a leaching model based on first-order desorption kinetics, was developed and run. Its input parameters are soil organic carbon content (SOC) and SOC/water partitioning coefficient (K(oc)). It accounts for current chlordecone soil contents and drainage water concentrations. The model was valid for andosol, which indicates that neither physico-chemical nor microbial degradation occurred. Dilution by previous deep tillages makes soil scrapping unrealistic. Lixiviation appeared the main way to reduce pollution. Besides the SOC and rainfall increases, K(oc) increased from nitisol to ferralsol and then andosol while lixiviation efficiency decreased. Consequently, pollution is bound to last for several decades for nitisol, centuries for ferralsol, and half a millennium for andosol. PMID:19167793

  1. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  2. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  3. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  4. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  5. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  6. Electrification of volcanic plumes

    NASA Astrophysics Data System (ADS)

    Mather, T. A.; Harrison, R. G.

    2006-07-01

    Volcanic lightning, perhaps the most spectacular consequence of the electrification of volcanic plumes, has been implicated in the origin of life on Earth, and may also exist in other planetary atmospheres. Recent years have seen volcanic lightning detection used as part of a portfolio of developing techniques to monitor volcanic eruptions. Remote sensing measurement techniques have been used to monitor volcanic lightning, but surface observations of the atmospheric electric Potential Gradient (PG) and the charge carried on volcanic ash also show that many volcanic plumes, whilst not sufficiently electrified to produce lightning, have detectable electrification exceeding that of their surrounding environment. Electrification has only been observed associated with ash-rich explosive plumes, but there is little evidence that the composition of the ash is critical to its occurrence. Different conceptual theories for charge generation and separation in volcanic plumes have been developed to explain the disparate observations obtained, but the ash fragmentation mechanism appears to be a key parameter. It is unclear which mechanisms or combinations of electrification mechanisms dominate in different circumstances. Electrostatic forces play an important role in modulating the dry fall-out of ash from a volcanic plume. Beyond the local electrification of plumes, the higher stratospheric particle concentrations following a large explosive eruption may affect the global atmospheric electrical circuit. It is possible that this might present another, if minor, way by which large volcanic eruptions affect global climate. The direct hazard of volcanic lightning to communities is generally low compared to other aspects of volcanic activity.

  7. Laser Surface Hardening of AISI 1045 Steel

    NASA Astrophysics Data System (ADS)

    Li, Ruifeng; Jin, Yajuan; Li, Zhuguo; Qi, Kai

    2014-09-01

    The study investigates laser surface hardening in the AISI 1045 steel using two different types of industrial laser: a high-power diode laser (HPDL) and a CO2 laser, respectively. The effect of process parameters such as beam power, travel speed on structure, case depth, and microhardness was examined. In most cases, a heat-affected zone (HAZ) formed below the surface; a substantial increase in surface hardness was achieved. In addition, big differences were found between the hardened specimens after HPDL surface hardening and CO2 laser surface hardening. For HPDL, depths of the HAZ were almost equal in total HAZ o, without surface melting. For CO2 laser, the depths changed a lot in the HAZ, with surface melting in the center. To better understand the difference of laser hardening results when use these two types of laser, numerical (ANSYS) analysis of the heat conduction involved in the process was also studied. For HPDL method, a rectangular beam spot and uniform energy distribution across the spot were assumed, while for CO2 laser, a circular beam spot and Gaussian energy distribution were assumed. The results showed that the energy distribution variety altered the thermal cycles of the HAZ dramatically. The rectangular HPDL laser beam spot with uniform energy distribution is much more feasible for laser surface hardening.

  8. Geochemical evidence for African dust and volcanic ash inputs to terra rossa soils on carbonate reef terraces, northern Jamaica, West Indies

    USGS Publications Warehouse

    Muhs, D.R.; Budahn, J.R.

    2009-01-01

    The origin of red or reddish-brown, clay-rich, "terra rossa" soils on limestone has been debated for decades. A traditional qualitative explanation for their formation has been the accumulation of insoluble residues as the limestone is progressively dissolved over time. However, this mode of formation often requires unrealistic or impossible amounts of carbonate dissolution. Therefore, where this mechanism is not viable and where local fluvial or colluvial inputs can be ruled out, an external source or sources must be involved in soil formation. On the north coast of the Caribbean island of Jamaica, we studied a sequence of terra rossa soils developed on emergent limestones thought to be of Quaternary age. The soils become progressively thicker, redder, more Fe- and Al-rich and Si-poor with elevation. Furthermore, although kaolinite is found in all the soils, the highest and oldest soils also contain boehmite. Major and trace element geochemistry shows that the host limestones and local igneous rocks are not likely source materials for the soils. Other trace elements, including the rare earth elements (REE), show that tephra from Central American volcanoes is not a likely source either. However, trace element geochemistry shows that airborne dust from Africa plus tephra from the Lesser Antilles island arc are possible source materials for the clay-rich soils. A third, as yet unidentified, source may also contribute to the soils. We hypothesize that older, more chemically mature Jamaican bauxites may have had a similar origin. The results add to the growing body of evidence of the importance of multiple parent materials, including far-traveled dust, to soil genesis.

  9. California's potential volcanic hazards

    SciTech Connect

    Jorgenson, P. )

    1989-01-01

    Although volcanic eruptions have occurred infrequently in California during the last few thousand years, the potential danger to life and property from volcanoes in the state is great enough to be of concern, according to a recent U.S. Geological Survey (USGS) publication. The 17-page bulletin, Potential Hazards from Future Volcanic Eruptions in California, gives a brief history of volcanic activity in California during the past 100,000 years, descriptions of the types of volcanoes in the state, the types of potentially hazardous volcanic events that could occur, and hazard-zonation maps and tables depicting six areas of the state where volcanic eruptions might occur. The six areas and brief descriptions of their past volcanic history and potential for future volcanic hazards are briefly summarized here.

  10. Influence of slip system hardening assumptions on modeling stress dependence of work hardening

    NASA Astrophysics Data System (ADS)

    Miller, Matthew; Dawson, Paul

    1997-11-01

    Due to the discrete directional nature of processes such as crystallographic slip, the orientation of slip planes relative to a fixed set of loading axes has a direct effect on the magnitude of the external load necessary to induce dislocation motion (yielding). The effect such geometric or textural hardening has on the macroscopic flow stress can be quantified in a polycrystal by the average Taylor factor M¯. Sources of resistance to dislocation motion such as interaction with dislocation structures, precipitates, and grain boundaries, contribute to the elevation of the critically resolved shear strength τcrss. In continuum slip polycrystal formulations, material hardening phenomena are reflected in the slip system hardness equations. Depending on the model, the hardening equations and the mean field assumption can both affect geometric hardening through texture evolution. In this paper, we examine continuum slip models and focus on how the slip system hardening model and the mean field assumption affect the stress-strain response. Texture results are also presented within the context of how the texture affects geometric hardening. We explore the effect of employing slip system hardnesses averaged over different size scales. We first compare a polycrystal simulation employing a single hardness per crystal to one using a latent hardening formulation producing distinct slip system hardnesses. We find little difference between the amplitude of the single hardness and a crystal-average of the latent hardening values. The geometric hardening is different due to the differences in the textures predicted by each model. We also find that due to the high degree of symmetry in an fcc crystal, macroscopic stress-strain predictions using simulations employing crystal- and aggregateaveraged hardnesses are nearly identical. We find this to be true for several different mean field assumptions. An aggregate-averaged hardness may be preferred in light of the difficulty

  11. Modeling of Irradiation Hardening of Polycrystalline Materials

    SciTech Connect

    Li, Dongsheng; Zbib, Hussein M.; Garmestani, Hamid; Sun, Xin; Khaleel, Mohammad A.

    2011-09-14

    High energy particle irradiation of structural polycrystalline materials usually produces irradiation hardening and embrittlement. The development of predict capability for the influence of irradiation on mechanical behavior is very important in materials design for next generation reactors. In this work a multiscale approach was implemented to predict irradiation hardening of body centered cubic (bcc) alpha-iron. The effect of defect density, texture and grain boundary was investigated. In the microscale, dislocation dynamics models were used to predict the critical resolved shear stress from the evolution of local dislocation and defects. In the macroscale, a viscoplastic self-consistent model was applied to predict the irradiation hardening in samples with changes in texture and grain boundary. This multiscale modeling can guide performance evaluation of structural materials used in next generation nuclear reactors.

  12. Modeling of anisotropic hardening of sheet metals

    NASA Astrophysics Data System (ADS)

    Yoshida, Fusahito; Hamasaki, Hiroshi; Uemori, Takeshi

    2013-12-01

    To describe the evolution of anisotropy of sheet metals, in terms of both r-values and stresses, the present paper proposes anisotropic hardening models, where the shape of yield surface changes with increasing plastic strain. In this framework of modeling, any types of yield functions are able to be used. The evolution of anisotropy is expressed by updating the yield function as an interpolation between two yield functions defined at two different effective plastic strains. In this paper, two types of interpolation models, i.e., nonlinear interpolation model and piecewise interpolation model are presented. These models are validated by comparing the experimental data on 3003-O aluminum sheet (after Hu, Int J Plasticity 23, 620-639, 2007). To describe the Bauschinger effect, the combined anisotropic-kinematic hardening model is formulated based on Yoshida-Uemori kinematic hardening model.

  13. The geothermal system of Caviahue-Copahue Volcanic Complex (Chile-Argentina): New insights from self-potential, soil CO2 degassing, temperature measurements and helium isotopes, with structural and fluid circulation implications.

    NASA Astrophysics Data System (ADS)

    Roulleau, Emilie; Bravo, Francisco; Barde-Cabusson, Stephanie; Pizarro, Marcela; Muños, Carlos; Sanchez, Juan; Tardani, Daniele; Sano, Yuji; Takahata, Naoto; de Cal, Federico; Esteban, Carlos

    2016-04-01

    Geothermal systems represent natural heat transfer engines in a confined volume of rock which are strongly influenced by the regional volcano-tectonic setting controlling the formation of shallow magmatic reservoirs, and by the local faults/fracture network, that permits the development of hydrothermal circulation cells and promote the vertical migration of fluids and heat. In the Southern Volcanic Zone of Chile-Argentina, geothermal resources occur in close spatial relationship with active volcanism along the Cordillera which is primarily controlled by the 1000 km long, NNE Liquiñe-Ofqui Fault Zone (LOFZ), an intra-arc dextral strike-slip fault system, associated with second-order intra-arc anisotropy of overall NE-SW (extensional) and NW-SE orientation (compressional). However there is still a lack of information on how fault network (NE and WNW strinking faults) and lithology control the fluid circulation. In this study, we propose new data of dense self-potential (SP), soil CO2 emanation and temperature (T) measurements within the geothermal area from Caviahue-Copahue Volcanic Complex (CCVC), coupled with helium isotopes ratios measured in fumaroles and thermal springs. We observe that inside the geothermal system the NE-striking faults, characterized by a combination of SP-CO2 and T maxima with high 3He/4He ratios (7.86Ra), promote the formation of high vertical permeability pathways for fluid circulation. Whereas, the WNW-striking faults represent low permeability pathways for hydrothermal fluids ascent associated with moderate 3He/4He ratios (5.34Ra), promoting the infiltration of meteoric water at shallow depth. These active zones are interspersed by SP-CO2- T minima, which represent self-sealed zones (e.g. impermeable altered rocks) at depth, creating a barrier inhibiting fluids rise. The NE-striking faults seem to be associated with the upflow zones of the geothermal system, where the boiling process produces a high vapor-dominated zone close to the

  14. Phenomenological modeling of hardening and thermal recovery in metals

    NASA Technical Reports Server (NTRS)

    Chan, K. S.; Lindholm, U. S.; Bodner, S. R.

    1988-01-01

    Modeling of hardening and thermal recovery in metals is considered within the context of unified elastic-viscoplastic theories. Specifically, the choices of internal variables and hardening measures, and the resulting hardening response obtained by incorporating saturation-type evolution equations into two general forms of the flow law are examined. Based on the analytical considerations, a procedure for delineating directional and isotropic hardening from uniaxial hardening data has been developed for the Bodner-Partom model and applied to a nickel-base superalloy, B1900 + Hf. Predictions based on the directional hardening properties deduced from the monotonic loading data are shown to be in good agreement with results of cyclic tests.

  15. Thermoelastic constitutive equations for chemically hardening materials

    NASA Technical Reports Server (NTRS)

    Shaffer, B. W.; Levitsky, M.

    1974-01-01

    Thermoelastic constitutive equations are derived for a material undergoing solidification or hardening as the result of a chemical reaction. The derivation is based upon a two component model whose composition is determined by the degree of hardening, and makes use of strain-energy considerations. Constitutive equations take the form of stress rate-strain rate relations, in which the coefficients are time-dependent functions of the composition. Specific results are developed for the case of a material of constant bulk modulus which undergoes a transition from an initial liquidlike state into an isotropic elastic solid. Potential applications are discussed.

  16. 'Work-Hardenable' Ductile Bulk Metallic Glass

    SciTech Connect

    Das, Jayanta; Eckert, Juergen; Tang Meibo; Wang Weihua; Kim, Ki Buem; Baier, Falko; Theissmann, Ralf

    2005-05-27

    Usually, monolithic bulk metallic glasses undergo inhomogeneous plastic deformation and exhibit poor ductility (<1%) at room temperature. We present a new class of bulk metallic glass, which exhibits high strength of up to 2265 MPa together with extensive 'work hardening' and large ductility of 18%. Significant increase in the flow stress was observed during deformation. The 'work-hardening' capability and ductility of this class of metallic glass is attributed to a unique structure correlated with atomic-scale inhomogeneity, leading to an inherent capability of extensive shear band formation, interactions, and multiplication of shear bands.

  17. Radiation Hardened Electronics for Space Environments (RHESE)

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Adams, James H.; Frazier, Donald O.; Patrick, Marshall C.; Watson, Michael D.; Johnson, Michael A.; Cressler, John D.; Kolawa, Elizabeth A.

    2007-01-01

    Radiation Environmental Modeling is crucial to proper predictive modeling and electronic response to the radiation environment. When compared to on-orbit data, CREME96 has been shown to be inaccurate in predicting the radiation environment. The NEDD bases much of its radiation environment data on CREME96 output. Close coordination and partnership with DoD radiation-hardened efforts will result in leveraged - not duplicated or independently developed - technology capabilities of: a) Radiation-hardened, reconfigurable FPGA-based electronics; and b) High Performance Processors (NOT duplication or independent development).

  18. Silicate volcanism on Io

    NASA Technical Reports Server (NTRS)

    Carr, M. H.

    1986-01-01

    This paper is mainly concerned with the nature of volcanic eruptions on Io, taking into account questions regarding the presence of silicates or sulfur as principal component. Attention is given to the generation of silicate magma, the viscous dissipation in the melt zone, thermal anomalies at eruption sites, and Ionian volcanism. According to the information available about Io, it appears that its volcanism and hence its surface materials are dominantly silicic. Several percent of volatile materials such as sulfur, but also including sodium- and potassium-rich materials, may also be present. The volatile materials at the surface are continually vaporized and melted as a result of the high rates of silicate volcanism.

  19. Modeling the sorption kinetic of metsulfuron-methyl on Andisols and Ultisols volcanic ash-derived soils: kinetics parameters and solute transport mechanisms.

    PubMed

    Cáceres, Lizethly; Escudey, Mauricio; Fuentes, Edwar; Báez, María E

    2010-07-15

    Metsulfuron-methyl sorption kinetic was studied in Andisol and Ultisol soils in view of their distinctive physical and chemical properties: acidic pH and variable surface charge. Different kinetic models were applied to the experimental results. The pseudo-second-order model fitted sorption kinetics data better than the pseudo-first-order model. The rate constant and the initial rate constant values obtained through this model demonstrated the different behavior of metsulfuron-methyl in both kinds of soils, both parameters being the highest for Andisol. The application of Elovich equation, intraparticle diffusion model and a two-site nonequilibrium model (TSNE) allowed to conclude that: (i) the high organic matter content is the governing factor for Andisols where mass transfer across the boundary layer, and in a lesser degree, intraparticle diffusion were the two processes controlling sorption kinetic and (ii) the mineral composition was more relevant in Ultisols where rate was controlled almost exclusively by intraparticle diffusion into macropores and micropores. The slower sorption rate on Ultisols, the mechanism involved and the lower sorption capacity of this kind of soils must be taken into account to assess leaching behavior of this herbicide. PMID:20399011

  20. Irradiation hardening of reduced activation martensitic steels

    NASA Astrophysics Data System (ADS)

    Kimura, A.; Morimura, T.; Narui, M.; Matsui, H.

    1996-10-01

    Irradiation response on the tensile properties of 9Cr2W steels has been investigated following FFTF/MOTA irradiations at temperatures between 646 and 873 K up to doses between 10 and 59 dpa. The largest irradiation hardening accompanied by the largest decrease in the elongation is observed for the specimens irradiated at 646 K at doses between 10 and 15 dpa. The irradiation hardening appears to saturate at a dose of around 10 dpa at the irradiation temperature. No hardening but softening was observed in the specimens irradiated at above 703 K to doses of 40 and 59 dpa. Microstructural observation by transmission electron microscope (TEM) revealed that the dislocation loops with the a<100> type Burgers vector and small precipitates which were identified to be M 6C type carbides existed after the irradiation at below 703 K. As for the void formation, the average size of voids increased with increasing irradiation temperature from 646 to 703 K. No voids were observed above 703 K. Irradiation softening was attributed to the enhanced recovery of martensitic structure under the irradiation. Post-irradiation annealing resulted in hardening by the annealing at 673 K and softening by the annealing at 873 K.

  1. SEU hardening of CMOS memory circuit

    NASA Technical Reports Server (NTRS)

    Whitaker, S.; Canaris, J.; Liu, K.

    1990-01-01

    This paper reports a design technique to harden CMOS memory circuits against Single Event Upset (SEU) in the space environment. A RAM cell and Flip Flop design are presented to demonstrate the method. The Flip Flop was used in the control circuitry for a Reed Solomon encoder designed for the Space Station.

  2. Extraordinary strain hardening by gradient structure

    PubMed Central

    Wu, XiaoLei; Jiang, Ping; Chen, Liu; Yuan, Fuping; Zhu, Yuntian T.

    2014-01-01

    Gradient structures have evolved over millions of years through natural selection and optimization in many biological systems such as bones and plant stems, where the structures change gradually from the surface to interior. The advantage of gradient structures is their maximization of physical and mechanical performance while minimizing material cost. Here we report that the gradient structure in engineering materials such as metals renders a unique extra strain hardening, which leads to high ductility. The grain-size gradient under uniaxial tension induces a macroscopic strain gradient and converts the applied uniaxial stress to multiaxial stresses due to the evolution of incompatible deformation along the gradient depth. Thereby the accumulation and interaction of dislocations are promoted, resulting in an extra strain hardening and an obvious strain hardening rate up-turn. Such extraordinary strain hardening, which is inherent to gradient structures and does not exist in homogeneous materials, provides a hitherto unknown strategy to develop strong and ductile materials by architecting heterogeneous nanostructures. PMID:24799688

  3. 'Fire hardening' spear wood does slightly harden it, but makes it much weaker and more brittle.

    PubMed

    Ennos, Antony Roland; Chan, Tak Lok

    2016-05-01

    It is usually assumed that 'fire hardening' the tips of spears, as practised by hunter-gatherers and early Homo spp., makes them harder and better suited for hunting. This suggestion was tested by subjecting coppiced poles of hazel to a fire-hardening process and comparing their mechanical properties to those of naturally seasoned poles. A Shore D hardness test showed that fire treatment slightly increased the hardness of the wood, but flexural and impact tests showed that it reduced the strength and work of fracture by 30% and 36%, respectively. These results suggest that though potentially slightly sharper and more durable, fire-hardened tips would actually be more likely to break off when used, as may have been the case with the earliest known wooden tool, the Clacton spear. Fire might first have been used to help sharpen the tips of spears, and fire-hardening would have been a mostly negative side effect, not its primary purpose. PMID:27194289

  4. Volcanism on Io

    NASA Astrophysics Data System (ADS)

    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.

  5. Deformation in metals after low temperature irradiation: Part II - Irradiation hardening, strain hardening, and stress ratios

    SciTech Connect

    Byun, Thak Sang; Li, Meimei

    2008-03-01

    Effects of irradiation at temperatures 200oC on tensile stress parameters are analyzed for dozens of bcc, fcc, and hcp pure metals and alloys, focusing on irradiation hardening, strain hardening, and relationships between the true stress parameters. Similar irradiation-hardening rates are observed for all the metals irrespective of crystal type; typically, the irradiation-hardening rates are large, in the range 100 - 1000 GPa/dpa, at the lowest dose of <0.0001 dpa and decrease with dose to a few tens of MPa/dpa or less at about 10 dpa. However, average irradiation-hardening rates over the dose range of 0 dpa − (the dose to plastic instability at yield) are considerably lower for stainless steels due to their high uniform ductility. It is shown that whereas low temperature irradiation increases the yield stress, it does not significantly change the strain-hardening rate of metallic materials; it decreases the fracture stress only when non-ductile failure occurs. Such dose independence in strain hardening behavior results in strong linear relationships between the true stress parameters. Average ratios of plastic instability stress to unirradiated yield stress are about 1.4, 3.9, and 1.3 for bcc metals (and precipitation hardened IN718 alloy), annealed fcc metals (and pure Zr), and Zr-4 alloy, respectively. Ratios of fracture stress to plastic instability stress are calculated to be 2.2, 1.7, and 2.1, respectively. Comparison of these values confirms that the annealed fcc metals and other soft metals have larger uniform ductility but smaller necking ductility when compared to other materials.

  6. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  7. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  8. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  9. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  10. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  11. The Potential of Low-Frequency (16-80 MHz) Ground Penetrating Radar to Investigate the Shallow Subsurface in the Arid, Volcanic, and Conductive Soils Near Yucca Mountain: Implications for MARSIS and SHARAD

    NASA Astrophysics Data System (ADS)

    Heggy, E.; Clifford, S.; Grimm, R.; Dinwiddie, C. L.

    2004-05-01

    In March 2004, the MARSIS radar sounder aboard the Mars Express spacecraft will begin acquiring the first of what will eventually be a global data set of the radar properties of the Martian subsurface within the frequency range of 0.5-5 MHz. Because no MARSIS prototype was ever built, and only limited GPR investigations of the Earth have been made within this frequency range, we plan to conduct a comprehensive radar investigation of a number of well-characterized terrestrial analog sites over the range of frequencies that will be employed by MARSIS and future Mars radars. The ability of these radars to determine the subsurface stratigraphy, structure, and distribution and aqueous history of water on Mars will be strongly dependent on the physical properties, mineralogy, and thermal structure of the subsurface-properties that will define the electrical and magnetic characteristics and ultimately determine the propagation, scattering and reflective properties of the crust. The arid volcanic environment around Yucca Mountain, Nevada has many similarities to the geologic environment of Mars. For example, the soil mineralogy is dominated by the presence of iron oxides, materials that can result in significant electrical and magnetic losses to the radar signal, thus affecting the maximum sounding depth and depth at which any subsurface feature can be identified. In order to evaluate and quantify the magnitude of these losses, we performed a 16 - 80 MHz GPR survey at several well-characterized areas in a region to the southwest of Yucca Mountain. A principal goal of this survey is to determine the extent to which these adverse soil properties influence the identification of subsurface stratigraphy, structure, and a water table at depths ranging from several tens to hundreds of meters.. We will present a summary of the field and laboratory data acquired during this survey and discuss its implications for radar sounding investigations of Mars

  12. Tellurium in active volcanic environments: Preliminary results

    NASA Astrophysics Data System (ADS)

    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

  13. Continuous in situ measurements of volcanic gases with a diode-laser-based spectrometer: CO2 and H2O concentration and soil degassing at Vulcano (Aeolian islands: Italy)

    PubMed Central

    De Rosa, Maurizio; Gagliardi, Gianluca; Rocco, Alessandra; Somma, Renato; De Natale, Paolo; De Natale, Giuseppe

    2007-01-01

    We report on a continuous-measurement campaign carried out in Vulcano (Aeolian islands, Sicily), devoted to the simultaneous monitoring of CO2 and H2O concentrations. The measurements were performed with an absorption spectrometer based on a semiconductor laser source emitting around a 2-μm wavelength. The emitted radiation was selectively absorbed by two molecular ro-vibrational transitions specific of the investigated species. Data for CO2 and H2O concentrations, and CO2 soil diffusive flux using an accumulation chamber configuration, were collected at several interesting sampling points on the island (Porto Levante beach- PLB, Fossa Grande Crater – FOG- and Valley of Palizzi, PAL). CO2/H2O values, measured on the ground, are very similar (around 0.019 (± 0.006)) and comparable to the previous discrete detected values of 0.213 (Fumarole F5-La Fossa crater rim) and 0.012 (Fumarole VFS – Baia Levante beach) obtaid during the 1977–1993 heating phase of the crater fumaroles. In this work much more homogeneous values are found in different points of the three sites investigated. The field work, although carried out in a limited time window (25th–28th August 2004), pointed out the new apparatus is suitable for continuous gas monitoring of the two species and their ratios, which are important geochemical indicators of volcanic activity, for which other reliable continuous monitoring systems are not yet available. PMID:17448243

  14. Characterization of the atrazine sorption process on Andisol and Ultisol volcanic ash-derived soils: kinetic parameters and the contribution of humic fractions.

    PubMed

    Báez, María E; Fuentes, Edwar; Espinoza, Jeannette

    2013-07-01

    Atrazine sorption was studied in six Andisol and Ultisol soils. Humic and fulvic acids and humin contributions were established. Sorption on soils was well described by the Freundlich model. Kf values ranged from 2.2-15.6 μg(1-1/n)mL(1/n)g⁻¹. The relevance of humic acid and humin was deduced from isotherm and kinetics experiments. KOC values varied between 221 and 679 mLg⁻¹ for these fractions. Fulvic acid presented low binding capacity. Sorption was controlled by instantaneous equilibrium followed by a time-dependent phase. The Elovich equation, intraparticle diffusion model, and a two-site nonequilibrium model allowed us to conclude that (i) there are two rate-limited phases in Andisols related to intrasorbent diffusion in organic matter and retarded intraparticle diffusion in the organo-mineral complex and that (ii) there is one rate-limited phase in Ultisols attributed to the mineral composition. The lower organic matter content of Ultisols and the slower sorption rate and mechanisms involved must be considered to assess the leaching behavior of atrazine. PMID:23711282

  15. Sorption behavior of bensulfuron-methyl on andisols and ultisols volcanic ash-derived soils: contribution of humic fractions and mineral-organic complexes.

    PubMed

    Espinoza, Jeannette; Fuentes, Edwar; Báez, María E

    2009-12-01

    Bensulfuron-methyl sorption was studied in Andisol and Ultisol soils in view of their characteristic physical and chemical properties, presenting acidic pH and variable charge. Humic and fulvic acids (HA and FA) and humin (HUM) contributions were established. Sorption was studied by using two synthetic sorbents, an aluminum-silicate with iron oxide coverage and the same sorbent coated with humic acid. Freundlich model described Bensulfuron-methyl behavior in all sorbents (R(2) 0.969-0.998). K(f) for soils (8.3-20.7 microg(1-1/n) mL(1/n) g(-1)) were higher than those reported in the literature. Organic matter, halloysite or kaolinite, and specific surface area contributed to the global process. The highest K(f) for HA, FA and HUM were 539.5, 82.9, and 98.7 microg(1-1/n) mL(1/n) g(-1). Model sorbents described the participation of variable charge materials with high adsorption capacity. The constant capacitance model was used to assess effects of Bensulfuron-methyl adsorption on the distribution of SOH, SOH(2)(+) and SO(-) sites of sorbents. PMID:19608318

  16. Effectiveness of hardening threaded parts by plastic deformation

    SciTech Connect

    Pyshkin, V.A.; Belai, S.V.; Dyad'kova, I.G.

    1983-03-01

    The rules of hardening threaded parts by roller burning the root of the inner diameter of a thread are studied. The effectiveness of hardening increases where the allowance for the inner diameter increases. By equations, a change in the inner diameter can be used to determine the depth of work hardening residual compressive stress, fatigue limit, and the mechanical properties of the threaded part. The effective stress concentration factor, increase in transmission load, and average tensile stress in cyclic loading, are also calculated. Equations help to determine the depth of hardening necessary; the optimum conditions of burnishing; and the maximum increase in fatigue strength, with optimum hardening conditions.

  17. Modeling the Case Hardening of Automotive Components

    NASA Astrophysics Data System (ADS)

    Munikamal, Tiruttani; Sundarraj, Suresh

    2013-04-01

    A generalized framework has been developed within ABAQUS to model the surface hardening heat treatment processes for automotive steel components. The macro-scale heat transfer and stress calculations during the heating and quenching are coupled with the microstructural phase calculations, defined through a user routine, to estimate key process parameters such as case depth and surface hardness. This model has been applied to predict these parameters in two key industrial processes, i.e., case hardening of crankshafts and case carburization of gears. The results of the case depth and hardness calculations have been validated with the literature and in-house plant data. The effect of varying quench conditions on the overall stress distribution changes within the component has been outlined.

  18. Radiation-hardened transistor and integrated circuit

    DOEpatents

    Ma, Kwok K.

    2007-11-20

    A composite transistor is disclosed for use in radiation hardening a CMOS IC formed on an SOI or bulk semiconductor substrate. The composite transistor has a circuit transistor and a blocking transistor connected in series with a common gate connection. A body terminal of the blocking transistor is connected only to a source terminal thereof, and to no other connection point. The blocking transistor acts to prevent a single-event transient (SET) occurring in the circuit transistor from being coupled outside the composite transistor. Similarly, when a SET occurs in the blocking transistor, the circuit transistor prevents the SET from being coupled outside the composite transistor. N-type and P-type composite transistors can be used for each and every transistor in the CMOS IC to radiation harden the IC, and can be used to form inverters and transmission gates which are the building blocks of CMOS ICs.

  19. Work hardening: occupational therapy in industrial rehabilitation.

    PubMed

    Matheson, L N; Ogden, L D; Violette, K; Schultz, K

    1985-05-01

    Work hardening, presented in this paper as a "new" service for the industrially injured, is actually well grounded in the traditional models and practices of occupational therapy. From the profession's early roots in industrial therapy to the development of a variety of programs for the industrially injured through the 1950s and 1960s, the historical and philosophical bases of occupational therapy support the use of work as an evaluative and therapeutic medium. What is actually new is the adoption of terminology, technology, and a program format that fits in with the needs of consumers in the 1980s. Recent developments that created the need for the specialized services that occupational therapists are uniquely qualified to provide include growth of private sector vocational rehabilitation, changes in workers' compensation laws, and increasing costs of vocational rehabilitation. This paper describes work hardening in its present form. A case example is given that demonstrates how work hardening can be a cost-effective and time-saving bridge which spans the gap between curative medicine and the return to work. PMID:4014411

  20. Dislocation Multi-junctions and Strain Hardening

    SciTech Connect

    Bulatov, V; Hsiung, L; Tang, M; Arsenlis, A; Bartelt, M; Cai, W; Florando, J; Hiratani, M; Rhee, M; Hommes, G; Pierce, T; Diaz de la Rubia, T

    2006-06-20

    At the microscopic scale, the strength of a crystal derives from the motion, multiplication and interaction of distinctive line defects--dislocations. First theorized in 1934 to explain low magnitudes of crystal strength observed experimentally, the existence of dislocations was confirmed only two decades later. Much of the research in dislocation physics has since focused on dislocation interactions and their role in strain hardening: a common phenomenon in which continued deformation increases a crystal's strength. The existing theory relates strain hardening to pair-wise dislocation reactions in which two intersecting dislocations form junctions tying dislocations together. Here we report that interactions among three dislocations result in the formation of unusual elements of dislocation network topology, termed hereafter multi-junctions. The existence of multi-junctions is first predicted by Dislocation Dynamics (DD) and atomistic simulations and then confirmed by the transmission electron microscopy (TEM) experiments in single crystal molybdenum. In large-scale Dislocation Dynamics simulations, multi-junctions present very strong, nearly indestructible, obstacles to dislocation motion and furnish new sources for dislocation multiplication thereby playing an essential role in the evolution of dislocation microstructure and strength of deforming crystals. Simulation analyses conclude that multi-junctions are responsible for the strong orientation dependence of strain hardening in BCC crystals.

  1. Stage IV work hardening in cubic metals

    SciTech Connect

    Rollett, A.D.; Kocks, U.F.; Doherty, R.D.

    1986-01-01

    The work hardening of fcc metals at large strains is discussed with reference to the linear stress-strain behavior often observed at large strains and known as Stage IV. The experimental evidence shows that Stage IV is a work hardening phenomenon that is found quite generally, even in pure fcc metals subjected to homogeneous deformation. A simple model for Stage IV in pure metals is presented, based on the accumulation of dislocation debris. Experiments are described for large strain torsion tests on four aluminum alloys. The level and extent of Stage IV scaled with the saturation stress that would represent the end of Stage III in the absence of a Stage IV. Reversing the torsion after large prestrains produced transient reductions in the work hardening. The strain rate sensitivity was also measured before and during the transient and found not to vary significantly. The microstructure observed at large strains in an Mg alloy suggest that Stage IV can occur in the absence of microband formation. Previous proposals for the cause of Stage IV are reviewed and found to be not supported by recent experimental data.

  2. Pulsed laser surface hardening of ferrous alloys.

    SciTech Connect

    Xu, Z.; Reed, C. B.; Leong, K. H.; Hunter, B. V.

    1999-09-30

    A high power pulsed Nd:YAG laser and special optics were used to produce surface hardening on 1045 steel and gray cast iron by varying the process parameters. Unlike CO{sub 2} lasers, where absorptive coatings are required, the higher absorptivity of ferrous alloys at the Nd:YAG laser wavelength eliminates the necessity of applying a coating before processing. Metallurgical analysis of the treated tracks showed that very fine and hard martensitic microstructure (1045 steel) or inhomogeneous martensite (gray cast iron) were obtained without surface melting, giving maximum hardness of HRC 61 and HRC 40 for 1045 steel and gray cast iron respectively. The corresponding maximum case depths for both alloys at the above hardness are 0.6 mm. Gray cast iron was more difficult to harden without surface melting because of its lower melting temperature and a significantly longer time-at-temperature required to diffuse carbon atoms from the graphite flakes into the austenite matrix during laser heating. The thermal distortion was characterized in term of flatness changes after surface hardening.

  3. Volcanic Aerosol Radiative Properties

    NASA Technical Reports Server (NTRS)

    Lacis, Andrew

    2015-01-01

    Large sporadic volcanic eruptions inject large amounts of sulfur bearing gases into the stratosphere which then get photochemically converted to sulfuric acid aerosol droplets that exert a radiative cooling effect on the global climate system lasting for several years.

  4. Modeling volcanic ash dispersal

    ScienceCinema

    None

    2011-10-06

    Explosive volcanic eruptions inject into the atmosphere large amounts of volcanic material (ash, blocks and lapilli). Blocks and larger lapilli follow ballistic and non-ballistic trajectories and fall rapidly close to the volcano. In contrast, very fine ashes can remain entrapped in the atmosphere for months to years, and may affect the global climate in the case of large eruptions. Particles having sizes between these two end-members remain airborne from hours to days and can cover wide areas downwind. Such volcanic fallout entails a serious threat to aircraft safety and can create many undesirable effects to the communities located around the volcano. 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 scenarios and/or to give short-term forecasts during emergency situations. This talk will be focused on the main aspects related to modeling volcanic ash dispersal and fallout with application to the well known problem created by the Eyjafjöll volcano in Iceland. Moreover, a short description of the main volcanic monitoring techniques is presented.

  5. Modeling volcanic ash dispersal

    SciTech Connect

    2010-10-22

    Explosive volcanic eruptions inject into the atmosphere large amounts of volcanic material (ash, blocks and lapilli). Blocks and larger lapilli follow ballistic and non-ballistic trajectories and fall rapidly close to the volcano. In contrast, very fine ashes can remain entrapped in the atmosphere for months to years, and may affect the global climate in the case of large eruptions. Particles having sizes between these two end-members remain airborne from hours to days and can cover wide areas downwind. Such volcanic fallout entails a serious threat to aircraft safety and can create many undesirable effects to the communities located around the volcano. 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 scenarios and/or to give short-term forecasts during emergency situations. This talk will be focused on the main aspects related to modeling volcanic ash dispersal and fallout with application to the well known problem created by the Eyjafjöll volcano in Iceland. Moreover, a short description of the main volcanic monitoring techniques is presented.

  6. Empirical beam hardening correction (EBHC) for CT

    SciTech Connect

    Kyriakou, Yiannis; Meyer, Esther; Prell, Daniel; Kachelriess, Marc

    2010-10-15

    Purpose: Due to x-ray beam polychromaticity and scattered radiation, attenuation measurements tend to be underestimated. Cupping and beam hardening artifacts become apparent in the reconstructed CT images. If only one material such as water, for example, is present, these artifacts can be reduced by precorrecting the rawdata. Higher order beam hardening artifacts, as they result when a mixture of materials such as water and bone, or water and bone and iodine is present, require an iterative beam hardening correction where the image is segmented into different materials and those are forward projected to obtain new rawdata. Typically, the forward projection must correctly model the beam polychromaticity and account for all physical effects, including the energy dependence of the assumed materials in the patient, the detector response, and others. We propose a new algorithm that does not require any knowledge about spectra or attenuation coefficients and that does not need to be calibrated. The proposed method corrects beam hardening in single energy CT data. Methods: The only a priori knowledge entering EBHC is the segmentation of the object into different materials. Materials other than water are segmented from the original image, e.g., by using simple thresholding. Then, a (monochromatic) forward projection of these other materials is performed. The measured rawdata and the forward projected material-specific rawdata are monomially combined (e.g., multiplied or squared) and reconstructed to yield a set of correction volumes. These are then linearly combined and added to the original volume. The combination weights are determined to maximize the flatness of the new and corrected volume. EBHC is evaluated using data acquired with a modern cone-beam dual-source spiral CT scanner (Somatom Definition Flash, Siemens Healthcare, Forchheim, Germany), with a modern dual-source micro-CT scanner (TomoScope Synergy Twin, CT Imaging GmbH, Erlangen, Germany), and with a modern

  7. Characterization of chlordecone-tolerant fungal populations isolated from long-term polluted tropical volcanic soil in the French West Indies.

    PubMed

    Merlin, Chloé; Devers, Marion; Crouzet, Olivier; Heraud, Cécile; Steinberg, Christian; Mougin, Christian; Martin-Laurent, Fabrice

    2014-04-01

    The insecticide chlordecone is a contaminant found in most of the banana plantations in the French West Indies. This study aims to search for fungal populations able to grow on it. An Andosol heavily contaminated with chlordecone, perfused for 1 year in a soil-charcoal system, was used to conduct enrichment cultures. A total of 103 fungal strains able to grow on chlordecone-mineral salt medium were isolated, purified, and deposited in the MIAE collection (Microorganismes d'Intérêt Agro-Environnemental, UMR Agroécologie, Institut National de la Recherche Agronomique, Dijon, France). Internal transcribed spacer sequencing revealed that all isolated strains belonged to the Ascomycota phylum and gathered in 11 genera: Metacordyceps, Cordyceps, Pochonia, Acremonium, Fusarium, Paecilomyces, Ophiocordyceps, Purpureocillium, Bionectria, Penicillium, and Aspergillus. Among predominant species, only one isolate, Fusarium oxysporum MIAE01197, was able to grow in a liquid culture medium that contained chlordecone as sole carbon source. Chlordecone increased F. oxysporum MIAE01197 growth rate, attesting for its tolerance to this organochlorine. Moreover, F. oxysporum MIAE01197 exhibited a higher EC50 value than the reference strain F. oxysporum MIAE00047. This further suggests its adaptation to chlordecone tolerance up to 29.2 mg l(-1). Gas chromatography-mass spectrometry (GC-MS) analysis revealed that 40 % of chlordecone was dissipated in F. oxysporum MIAE01197 suspension culture. No chlordecone metabolite was detected by GC-MS. However, weak amount of (14)CO2 evolved from (14)C10-chlordecone and (14)C10-metabolites were observed. Sorption of (14)C10-chlordecone onto fungal biomass followed a linear relationship (r (2) = 0.99) suggesting that it may also account for chlordecone dissipation in F. oxysporum MIAE01197 culture. PMID:23872892

  8. Volcanic Eruptions in Kamchatka

    NASA Technical Reports Server (NTRS)

    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

  9. Surface Coatings on Lunar Volcanic Glasses

    NASA Technical Reports Server (NTRS)

    Wentworth, Susan J.; McKay, D. S.; Thomas,-Keprta, K. L.; Clemett, S. J.

    2007-01-01

    We are undertaking a detailed study of surface deposits on lunar volcanic glass beads. These tiny deposits formed by vapor condensation during cooling of the gases that drove the fire fountain eruptions responsible for the formation of the beads. Volcanic glass beads are present in most lunar soil samples in the returned lunar collection. The mare-composition beads formed as a result of fire-fountaining approx.3.4-3.7 Ga ago, within the age range of large-scale mare volcanism. Some samples from the Apollo 15 and Apollo 17 landing sites are enriched in volcanic spherules. Three major types of volcanic glass bead have been identified: Apollo 15 green glass, Apollo 17 orange glass, and Apollo 17 "black" glass. The Apollo 15 green glass has a primitive composition with low Ti. The high-Ti compositions of the orange and black glasses are essentially identical to each other but the black glasses are opaque because of quench crystallization. A poorly understood feature common to the Apollo 15 and 17 volcanic glasses is the presence of small deposits of unusual materials on their exterior surfaces. For example, early studies indicated that the Apollo 17 orange glasses had surface enrichments of In, Cd, Zn, Ga, Ge, Au, and Na, and possible Pb- and Zn-sulfides, but it was not possible to characterize the surface features in detail. Technological advances now permit us to examine such features in detail. Preliminary FE-TEM/X-ray studies of ultramicrotome sections of Apollo 15 green glass indicate that the surface deposits are heterogeneous and layered, with an inner layer consisting of Fe with minor S and an outer layer of Fe and no S, and scattered Zn enrichments. Layering in surface deposits has not been identified previously; it will be key to defining the history of lunar fire fountaining.

  10. Radiogeochemistry of Kamchatka soils

    NASA Astrophysics Data System (ADS)

    Zakharikhina, L. V.; Litvinenko, Yu. S.

    2016-01-01

    Background concentrations of Th and U in volcanic soils (Andosols) of Kamchatka are much lower than their clarkes in continental soils. The dose rate of gamma radiation above the soil surface (10-11.5 µR/h in the south and 8-9.5 [m]R/h in the north of Kamchatka Peninsula) is lower than the natural level of this index for the mountainous areas in the boreal zone of Russia. The natural radiogeochemical background of Kamchatka soils is controlled by the petrochemical composition of volcanic ash composing the mineral basis of Kamchatka soils. It is higher in the southern soil province, where soils develop from acidic ashes, in comparison with the northern province, with a predominance of soils developing from ashes of basic and intermediate composition. This agrees with Th and U clarkes for the corresponding types of volcanic rocks and explains the natural origin of the elevated radiogeochemical background in the southern part of Kamchatka as compared with its northern part. The soils of the northern province developing from relatively fresh volcanic ashes show a lower Th/U ratio as compared to the soils of southern Kamchatka because of higher uranium content in the newly deposited ashes.

  11. Constitutive modelling of evolving flow anisotropy including distortional hardening

    SciTech Connect

    Pietryga, Michael P.; Vladimirov, Ivaylo N.; Reese, Stefanie

    2011-05-04

    The paper presents a new constitutive model for anisotropic metal plasticity that takes into account the expansion or contraction (isotropic hardening), translation (kinematic hardening) and change of shape (distortional hardening) of the yield surface. The experimentally observed region of high curvature ('nose') on the yield surface in the loading direction and flattened shape in the reverse loading direction are modelled here by means of the concept of directional distortional hardening. The modelling of directional distortional hardening is accomplished by means of an evolving fourth-order tensor. The applicability of the model is illustrated by fitting experimental subsequent yield surfaces at finite plastic deformation. Comparisons with test data for aluminium low and high work hardening alloys display a good agreement between the simulation results and the experimental data.

  12. Volcanism in Eastern Africa

    NASA Technical Reports Server (NTRS)

    Cauthen, Clay; Coombs, Cassandra R.

    1996-01-01

    In 1891, the Virunga Mountains of Eastern Zaire were first acknowledged as volcanoes, and since then, the Virunga Mountain chain has demonstrated its potentially violent volcanic nature. The Virunga Mountains lie across the Eastern African Rift in an E-W direction located north of Lake Kivu. Mt. Nyamuragira and Mt. Nyiragongo present the most hazard of the eight mountains making up Virunga volcanic field, with the most recent activity during the 1970-90's. In 1977, after almost eighty years of moderate activity and periods of quiescence, Mt. Nyamuragira became highly active with lava flows that extruded from fissures on flanks circumscribing the volcano. The flows destroyed vast areas of vegetation and Zairian National Park areas, but no casualties were reported. Mt. Nyiragongo exhibited the same type volcanic activity, in association with regional tectonics that effected Mt. Nyamuragira, with variations of lava lake levels, lava fountains, and lava flows that resided in Lake Kivu. Mt. Nyiragongo, recently named a Decade volcano, presents both a direct and an indirect hazard to the inhabitants and properties located near the volcano. The Virunga volcanoes pose four major threats: volcanic eruptions, lava flows, toxic gas emission (CH4 and CO2), and earthquakes. Thus, the volcanoes of the Eastern African volcanic field emanate harm to the surrounding area by the forecast of volcanic eruptions. During the JSC Summer Fellowship program, we will acquire and collate remote sensing, photographic (Space Shuttle images), topographic and field data. In addition, maps of the extent and morphology(ies) of the features will be constructed using digital image information. The database generated will serve to create a Geographic Information System for easy access of information of the Eastem African volcanic field. The analysis of volcanism in Eastern Africa will permit a comparison for those areas from which we have field data. Results from this summer's work will permit

  13. Volcanism in Kamchatka, Russia

    NASA Astrophysics Data System (ADS)

    Eichelberger, J. C.; Eichelberger, L. G.

    2008-12-01

    The diverse and robust volcanism of Kamchatka challenges our understanding of subduction zone volcanism on both local volcanic and regional tectonic scales (e.g., AGU Geophysics Monograph 172). One might expect the two North Pacific peninsula/ island arc pairs, Kamchatka Peninsula/ Kuriles and Alaska Peninsula/ Aleutians, to be twins, but there are some important differences as well as similarities. In both cases, the continental margin largely controls the position of the volcanic front on the peninsulas and the associated island arcs are pinned to the peninsula tips. The unusually acute Aleutian-Kamchatka subduction cusp may have formed by jamming and outboard (southeastward) jumping of Bering subduction at about 50 Ma to form the Aleutians, with capture of the Bering microplate by the North American plate. Perhaps the acuteness was augmented by convergence of the Emperor Seamount Chain with the junction. Another outboard (eastward) jump may explain the two lines of volcanoes in Kamchatka, which are partially separated by the rift-like Central Kamchatka Depression. This is thought to have occurred at 7 - 10 Ma when 3 seamounts were accreted as capes to the eastern edge of Kamchatka. But other workers, pointing to east-west chemical trends and persistence of volcanism in the inboard Sredinny Range, prefer to postulate two depths of volatile release from the same intact slab. On the Alaska Peninsula, Quaternary volcanic deposits are discontinuous and even famous Mount Katmai is a volumetric dwarf. The opposite is the case in Kamchatka, where pre-volcanic basement under the young eastern volcanic front is sparsely exposed and Holocene stratovolcanoes rise as high as 4,835 m. Calderas are so numerous they sometimes overlap. Some exhibit repeated andesitic stratovolcano - silicic caldera cycles over remarkably short time frames. Remoteness, international politics, and challenging weather have conspired to make Kamchatka's volcanoes less appreciated by non

  14. Volcanic Glasses: Construction Materials

    NASA Astrophysics Data System (ADS)

    Moskowitz, Samuel E.

    1998-01-01

    Natural glass is the product of rapidly cooled molten rock. Two natural sources of the melt are volcanic eruption and meteoritic impact. Pure glass is an amorphous aggregate. Volcanic glass is a material that could be utilized in the construction of extraterrestrial outposts. Pumice and perlite are volcanic glasses currently used in the building industry. Samples of natural volcanic glass found in the lunar regolith were returned to Earth as part of the Apollo and Luna programs. An alpha proton X-ray spectrometer onboard the Pathfinder recently examined martian rocks located in the vicinity of the lander craft. Preliminary results of chemical composition by weight of SiO2 50-55%, Al203 11-13%, K20 1-2%, Na20 2-5%, CaO 4-6%, MgO 3-7%, FeO 12-14%, S03 2-5%, and MnO <1% were given for two rocks. Parenthetically, the values for K and Mn were perhaps too high, and the analysis was based on X-ray data only. The appreciable amount of silica already found on Mars and empirical evidence to support the hypothesis that the planet once had water sufficient to rapidly cool magma imply the possibility of discovering natural glass of volcanic origin in subsequent missions.

  15. Volcanic passive margins

    NASA Astrophysics Data System (ADS)

    Geoffroy, Laurent

    2005-12-01

    Compared to non-volcanic ones, volcanic passive margins mark continental break-up over a hotter mantle, probably subject to small-scale convection. They present distinctive genetic and structural features. High-rate extension of the lithosphere is associated with catastrophic mantle melting responsible for the accretion of a thick igneous crust. Distinctive structural features of volcanic margins are syn-magmatic and continentward-dipping crustal faults accommodating the seaward flexure of the igneous crust. Volcanic margins present along-axis a magmatic and tectonic segmentation with wavelength similar to adjacent slow-spreading ridges. Their 3D organisation suggests a connection between loci of mantle melting at depths and zones of strain concentration within the lithosphere. Break-up would start and propagate from localized thermally-softened lithospheric zones. These 'soft points' could be localized over small-scale convection cells found at the bottom of the lithosphere, where adiabatic mantle melting would specifically occur. The particular structure of the brittle crust at volcanic passive margins could be interpreted by active and sudden oceanward flow of both the unstable hot mantle and the ductile part of the lithosphere during the break-up stage. To cite this article: L. Geoffroy, C. R. Geoscience 337 (2005).

  16. Radiation hardening of diagnostics for fusion reactors

    SciTech Connect

    Baur, J.F.; Engholm, B.A.; Hacker, M.P.; Maya, I.; Miller, P.H.; Toffolo, W.E.; Wojtowicz, S.S.

    1981-12-01

    A list of the diagnostic systems presently used in magnetic confinement fusion experiments is compiled herein. The radiation-sensitive components are identified, and their locations in zones around the machine are indicated. A table of radiation sensitivities of components is included to indicate the data available from previous work in fission reactor, space probe, and defense-related programs. Extrapolation and application to hardening of fusion diagnostic systems requires additional data that are more specific to the fusion radiation environment and fusion components. A list is also given of present radiation-producing facilities where near-term screening tests of materials and components can be performed.

  17. Expecting the Unexpected: Radiation Hardened Software

    NASA Technical Reports Server (NTRS)

    Penix, John; Mehlitz, Peter C.

    2005-01-01

    Radiation induced Single Event Effects (SEEs) are a serious problem for spacecraft flight software, potentially leading to a complete loss of mission. Conventional risk mitigation has been focused on hardware, leading to slow, expensive and outdated on-board computing devices, increased power consumption and launch mass. Our approach is to look at SEEs from a software perspective, and to explicitly design flight software so that it can detect and correct the majority of SEES. Radiation hardened flight software will reduce the significant residual residual risk for critical missions and flight phases, and enable more use of inexpensive and fast COTS hardware.

  18. Strain hardening of steel EP836

    SciTech Connect

    Lyadskaya, A.A.; Lappa, R.M.; Spuskanyuk, V.Z.

    1986-03-01

    The authors investigate the effect of different combinations of cold hydraulic pressing and heat treatment on the physical and mechanical properties of steel EP836 (03N17K10V10MT), containing 0.03% C, 16-17% Ni, 10-11.5% Co, 9.5-11.5% W, 1% Ti, 1% Mo, and 0.15% A1. Deformation of the unaged steel resulted in insignificant hardening without a decrease in plasticity; this agrees with the results of investigations of other steels of this class.

  19. Organic Entrainment and Preservation in Volcanic Glasses

    NASA Technical Reports Server (NTRS)

    Wilhelm, Mary Beth; Ojha, Lujendra; Brunner, Anna E.; Dufek, Josef D.; Wray, James Joseph

    2014-01-01

    Unaltered pyroclastic deposits have previously been deemed to have "low" potential for the formation, concentration and preservation of organic material on the Martian surface. Yet volcanic glasses that have solidified very quickly after an eruption may be good candidates for containment and preservation of refractory organic material that existed in a biologic system pre-eruption due to their impermeability and ability to attenuate UV radiation. Analysis using NanoSIMS of volcanic glass could then be performed to both deduce carbon isotope ratios that indicate biologic origin and confirm entrainment during eruption. Terrestrial contamination is one of the biggest barriers to definitive Martian organic identification in soil and rock samples. While there is a greater potential to concentrate organics in sedimentary strata, volcanic glasses may better encapsulate and preserve organics over long time scales, and are widespread on Mars. If volcanic glass from many sites on Earth could be shown to contain biologically derived organics from the original environment, there could be significant implications for the search for biomarkers in ancient Martian environments.

  20. Technology Developments in Radiation-Hardened Electronics for Space Environments

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Howell, Joe T.

    2008-01-01

    The Radiation Hardened Electronics for Space Environments (RHESE) project consists of a series of tasks designed to develop and mature a broad spectrum of radiation hardened and low temperature electronics technologies. Three approaches are being taken to address radiation hardening: improved material hardness, design techniques to improve radiation tolerance, and software methods to improve radiation tolerance. Within these approaches various technology products are being addressed including Field Programmable Gate Arrays (FPGA), Field Programmable Analog Arrays (FPAA), MEMS, Serial Processors, Reconfigurable Processors, and Parallel Processors. In addition to radiation hardening, low temperature extremes are addressed with a focus on material and design approaches. System level applications for the RHESE technology products are discussed.

  1. Seasonality of volcanic eruptions

    NASA Astrophysics Data System (ADS)

    Mason, B. G.; Pyle, D. M.; Dade, W. B.; Jupp, T.

    2004-04-01

    An analysis of volcanic activity during the last three hundred years reveals that volcanic eruptions exhibit seasonality to a statistically significant degree. This remarkable pattern is observed primarily along the Pacific "Ring of Fire" and locally at some individual volcanoes. Globally, seasonal fluctuations amount to 18% of the historical average monthly eruption rate. In some regions, seasonal fluctuations amount to as much as 50% of the average eruption rate. Seasonality principally reflects the temporal distribution of the smaller, dated eruptions (volcanic explosivity index of 0-2) that dominate the eruption catalog. We suggest that the pattern of seasonality correlates with the annual Earth surface deformation that accompanies the movement of surface water mass during the annual hydrological cycle and illustrate this with respect to global models of surface deformation and regional measurements of annual sea level change. For example, seasonal peaks in the eruption rate of volcanoes in Central America, the Alaskan Peninsula, and Kamchatka coincide with periods of falling regional sea level. In Melanesia, in contrast, peak numbers of volcanic eruptions occur during months of maximal regional sea level and falling regional atmospheric pressure. We suggest that the well-documented slow deformation of Earth's surface that accompanies the annual movements of water mass from oceans to continents acts to impose a fluctuating boundary condition on volcanoes, such that volcanic eruptions tend to be concentrated during periods of local or regional surface change rather than simply being distributed randomly throughout the year. Our findings have important ramifications for volcanic risk assessment and volcanoclimate feedback mechanisms.

  2. The electrification of volcanic plumes and volcanic lightning

    NASA Astrophysics Data System (ADS)

    Harrison, R. G.; Mather, T. A.

    2006-12-01

    We present a review of our current understanding of the electrification of volcanic plumes on Earth and discuss the possible implications both in terms of the volcanic monitoring, early Earth evolution and planetary exploration. We also present simple calculations to show how the global electrical circuit might be modified following a large volcanic eruption reaching the stratosphere. Volcanic lightning is perhaps the most spectacular consequence of the electrification of volcanic plumes. Recent years have seen remote-sensing measurements of volcanic lightning used as part of a portfolio of techniques to monitor volcanic eruptions. Surface observations of the atmospheric electric Potential Gradient (PG) and the charge carried on volcanic ash also show that many volcanic plumes, whilst not sufficiently electrified to produce lightning, have detectable electrification exceeding that of their surrounding environment. Electrification has only been observed associated with ash-rich explosive plumes, but there is little evidence that the composition of the ash is critical to its occurrence. Different conceptual theories for charge generation and separation in volcanic plumes have been developed to explain the disparate observations obtained, but the ash fragmentation mechanism appears to be key. It is unclear which mechanisms or combinations of electrification mechanisms dominate in different circumstances. Electrostatic forces play an important role in modulating dry fall-out of ash from a volcanic plume. Beyond the local electrification of plumes, the higher stratospheric particle concentrations following a large explosive eruption may affect the global atmospheric electrical circuit. It is possible that this might present another, if minor, way by which large volcanic eruptions affect global climate. Volcanic lightning has been implicated in a number of ways in the origin of life on Earth, and may also exist in other planetary atmospheres where measurements of its

  3. Precambrian lunar volcanic protolife.

    PubMed

    Green, Jack

    2009-06-01

    Five representative terrestrial analogs of lunar craters are detailed relevant to Precambrian fumarolic activity. Fumarolic fluids contain the ingredients for protolife. Energy sources to derive formaldehyde, amino acids and related compounds could be by flow charging, charge separation and volcanic shock. With no photodecomposition in shadow, most fumarolic fluids at 40 K would persist over geologically long time periods. Relatively abundant tungsten would permit creation of critical enzymes, Fischer-Tropsch reactions could form polycyclic aromatic hydrocarbons and soluble volcanic polyphosphates would enable assembly of nucleic acids. Fumarolic stimuli factors are described. Orbital and lander sensors specific to protolife exploration including combined Raman/laser-induced breakdown spectrocsopy are evaluated. PMID:19582224

  4. Precambrian Lunar Volcanic Protolife

    PubMed Central

    Green, Jack

    2009-01-01

    Five representative terrestrial analogs of lunar craters are detailed relevant to Precambrian fumarolic activity. Fumarolic fluids contain the ingredients for protolife. Energy sources to derive formaldehyde, amino acids and related compounds could be by flow charging, charge separation and volcanic shock. With no photodecomposition in shadow, most fumarolic fluids at 40 K would persist over geologically long time periods. Relatively abundant tungsten would permit creation of critical enzymes, Fischer-Tropsch reactions could form polycyclic aromatic hydrocarbons and soluble volcanic polyphosphates would enable assembly of nucleic acids. Fumarolic stimuli factors are described. Orbital and lander sensors specific to protolife exploration including combined Raman/laser-induced breakdown spectrocsopy are evaluated. PMID:19582224

  5. Mercurian volcanism questioned

    USGS Publications Warehouse

    Wilhelms, D.E.

    1976-01-01

    The Mariner 10 television team has argued that extensive plains on Mercury were formed by volcanism and compared them with the demonstrably lunar maria. I believe, however, that in stratigraphic relations, surface morphology, and albedo contrast, the Mercurian plains more closely resemble the lunar light plains. These lunar plains were interpreted as volcanic on the basis of data comparable to that available to the Mariner 10 investigators but have been shown by the Apollo missions to be of impact origin. The plains on Mercury might also be formed of impact materials, perhaps of impact melt or other basin ejecta that behaved more like a fluid when emplaced that did lunar basin ejecta. ?? 1976.

  6. Hardened Client Platforms for Secure Internet Banking

    NASA Astrophysics Data System (ADS)

    Ronchi, C.; Zakhidov, S.

    We review the security of e-banking platforms with particular attention to the exploitable attack vectors of three main attack categories: Man-in-the-Middle, Man-in-the-PC and Man-in-the-Browser. It will be shown that the most serious threats come from combination attacks capable of hacking any transaction without the need to control the authentication process. Using this approach, the security of any authentication system can be bypassed, including those using SecureID Tokens, OTP Tokens, Biometric Sensors and Smart Cards. We will describe and compare two recently proposed e-banking platforms, the ZTIC and the USPD, both of which are based on the use of dedicated client devices, but with diverging approaches with respect to the need of hardening the Web client application. It will be shown that the use of a Hardened Browser (or H-Browser) component is critical to force attackers to employ complex and expensive techniques and to reduce the strength and variety of social engineering attacks down to physiological fraud levels.

  7. Hardness variability in commercial and hardened technologies

    SciTech Connect

    Shaneyfelt, M.R.; Winokur, P.S.; Meisenheimer, T.L.; Sexton, F.W.; Roeske, S.B.; Knoll, M.G.

    1994-03-01

    Over the past 10 years, there have been a number of advances in methods to assess and assure the radiation hardness of microelectronics in military and space applications. At the forefront of these is the Qualified Manufacturers List (QML) methodology, in which the hardness of product is ``built-in`` through statistical process control (SPC) of technology parameters relevant to the radiation response, test structure to integrated circuit (IC) correlations, and techniques for extrapolating laboratory test results to varying radiation scenarios. At the same time, there has been renewed interest in the use of commercial technology -- with its enhanced performance, reduced cost, and higher reliability -- in military and space systems. In this paper, we initially demonstrate the application of QML techniques to assure and control the radiation response of hardened technologies. Through several examples, we demonstrate intra-die, wafer-to-wafer, and lot-to-lot variations in a hardened technology. We observe 10 to 30% variations in key technology parameters that result from variability in geometry, process, and design layout. Radiation-induced degradation is seen to mirror preirradiation characteristics. We then evaluate commercial technologies and report considerably higher variability in radiation hardness, i.e., variations by a factor of two to five. This variability is shown to arise from a lack of control of technology parameters relevant to the radiation response, which a commercial manufacturer has no interest in controlling in a normal process flow.

  8. Hardness variability in commercial and hardened technologies

    NASA Astrophysics Data System (ADS)

    Shaneyfelt, M. R.; Winokur, P. S.; Meisenheimer, T. L.; Sexton, F. W.; Roeske, S. B.; Knoll, M. G.

    1994-01-01

    Over the past 10 years, there have been a number of advances in methods to assess and assure the radiation hardness of microelectronics in military and space applications. At the forefront of these is the Qualified Manufacturers List (QML) methodology, in which the hardness of product is 'built-in' through statistical process control (SPC) of technology parameters relevant to the radiation response, test structure to integrated circuit (IC) correlations, and techniques for extrapolating laboratory test results to varying radiation scenarios. At the same time, there has been renewed interest in the use of commercial technology -- with its enhanced performance, reduced cost, and higher reliability -- in military and space systems. In this paper, we initially demonstrate the application of QML techniques to assure and control the radiation response of hardened technologies. Through several examples, we demonstrate intra-die, wafer-to-wafer, and lot-to-lot variations in a hardened technology. We observe 10 to 30% variations in key technology parameters that result from variability in geometry, process, and design layout. Radiation-induced degradation is seen to mirror preirradiation characteristics. We then evaluate commercial technologies and report considerably higher variability in radiation hardness, i.e., variations by a factor of two to five. This variability is shown to arise from a lack of control of technology parameters relevant to the radiation response, which a commercial manufacturer has no interest in controlling in a normal process flow.

  9. Volcanic Hazards Survey in the Trans Mexican Volcanic Belt

    NASA Technical Reports Server (NTRS)

    Abrams, Michael; Siebe, Claus; Macias, Jose Luis

    1996-01-01

    We have assembled a digital mosaic of 11 Landsat Thematic images to serve as a mapping base for reconnaissance activities within the Trans Mexican Volcanic Belt. This will aid us in interpretation and in the evaluation of potential activity of all the volcanic centers there. One result is a volcanic hazards map of the area.

  10. Lung problems and volcanic smog

    MedlinePlus

    ... smog forms. This smog is a type of air pollution. Volcanic smog also contains highly acidic aerosols (tiny ... www.ncbi.nlm.nih.gov/pubmed/17650330 . Volcanic Air Pollution -- A Hazard in Hawai'i. U.S. Geological Survey. ...

  11. Lung problems and volcanic smog

    MedlinePlus

    ... a volcano erupts and releases gases into the atmosphere. Volcanic smog can irritate the lungs and make ... react with oxygen, moisture, and sunlight in the atmosphere, volcanic smog forms. This smog is a type ...

  12. Volcanism in the Classroom.

    ERIC Educational Resources Information Center

    Albin, Edward F.

    1993-01-01

    Presents activities to familiarize junior high school students with the processes behind and reasons for volcanism, which is generally a planet's way of releasing excessive internal heat and pressure. Students participate in the creation of four important volcano-related simulations: a lava flow, a shield volcano, a cinder-cone volcano, and a…

  13. Radiation-Hardened Electronics for Space Environments (RHESE)

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Adams, James H.; Patrick, Marshall C.; Johnson, Michael; Cressler, John D.

    2008-01-01

    This conference poster explores NASA's Radiation-Hardened Electronics for Space Environments project. This project aims to advance the state of the art in high performance, radiation-hardened electronics that enable the long-term, reliable operation of a spacecraft in extreme radiation and temperature of space and the lunar surface.

  14. Hardening treatment of friction surfaces of ball journal bearings

    NASA Astrophysics Data System (ADS)

    Gorlenko, A. O.; Davidov, S. V.

    2016-04-01

    The article presents the technology of finishing plasma hardening by the application of the multi-layer nanocoating Si-O-C-N system to harden the friction surfaces of the ball journal bearings. The authors of the paper have studied the applied wear-resistant anti-friction coating tribological characteristics, which determine the increase in wear resistance of the ball journal bearings.

  15. Radiation-Hardened Electronics for the Space Environment

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Watson, Michael D.

    2007-01-01

    RHESE covers a broad range of technology areas and products. - Radiation Hardened Electronics - High Performance Processing - Reconfigurable Computing - Radiation Environmental Effects Modeling - Low Temperature Radiation Hardened Electronics. RHESE has aligned with currently defined customer needs. RHESE is leveraging/advancing SOA space electronics, not duplicating. - Awareness of radiation-related activities through out government and industry allow advancement rather than duplication of capabilities.

  16. New analytical approach for neutron beam-hardening correction.

    PubMed

    Hachouf, N; Kharfi, F; Hachouf, M; Boucenna, A

    2016-01-01

    In neutron imaging, the beam-hardening effect has a significant effect on quantitative and qualitative image interpretation. This study aims to propose a linearization method for beam-hardening correction. The proposed method is based on a new analytical approach establishing the attenuation coefficient as a function of neutron energy. Spectrum energy shift due to beam hardening is studied on the basis of Monte Carlo N-Particle (MCNP) simulated data and the analytical data. Good agreement between MCNP and analytical values has been found. Indeed, the beam-hardening effect is well supported in the proposed method. A correction procedure is developed to correct the errors of beam-hardening effect in neutron transmission, and therefore for projection data correction. The effectiveness of this procedure is determined by its application in correcting reconstructed images. PMID:26609685

  17. The Zuni-Bandera Volcanic Field, NM: An Analog for Exploring Planetary Volcanic Terrains

    NASA Astrophysics Data System (ADS)

    Bleacher, J. E.; Garry, W. B.; Zimbelman, J. R.; Crumpler, L. S.; Aubele, J. C.

    2010-12-01

    The Zuni-Bandera volcanic field, near Grants, New Mexico, is comprised of volcanic deposits from several basaltic eruptions during the last million years. This vent field exhibits a diverse group of coalesced lava flows and displays well-preserved volcanic features including a’a and pahoehoe flows, collapsed lava tubes, cinder cones and low shields. The McCartys flow is a 48-km long inflated basalt flow and is the youngest in the field at around 3000 years old. Over the last three years we have used the Zuni-Bandera volcanic field, and the McCartys flow in particular, as a terrestrial analog for exploring planetary volcanic fields, and understanding the role of lava sheet inflation in flow field development. We have conducted three different styles of analog tests, 1) basic field science focused on understanding lava sheet inflation, 2) mission operations tests related to EVA design and real-time modification of traverse plans, and 3) science enabling technology tests. The Zuni-Bandera field is an ideal location for each style of analog test because it provides easy access to a diverse set of volcanic features with variable quality of preservation. However, many limitations must also be considered in order to maximize lessons learned. The McCartys flow displays well-preserved inflation plateaus that rise up to 15 m above the surrounding field. The preservation state enables textures and morphologies indicative of this process to be characterized. However, the pristine nature of the flow does not compare well with the much older and heavily modified inflated flows of Mars and the Moon. Older flows west of McCartys add value to this aspect of analog work because of their degraded surfaces, development of soil horizons, loose float, and limited exposure of outcrops, similar to what might be observed on the Moon or Mars. EVA design tests and science enabling technology tests at the Zuni-Bandera field provide the opportunity to document and interpret the relationships

  18. Hardening and yielding in colloidal gels

    NASA Astrophysics Data System (ADS)

    Del Gado, Emanuela; Colombo, Jader; Bouzid, Mehdi

    Attractive colloidal gel networks are disordered elastic solids that can form even in extremely dilute particle suspensions. With interaction strengths comparable to the thermal energy, their stress-bearing network can locally restructure via breaking and reforming inter-particle bonds. We use molecular dynamics simulations of a model system to investigate the strain hardening and the yielding process. During shear start up protocol, the system exhibits strong localization of tensile stresses that may be released through the breaking and formation of new bonds. In this regime, the small amplitude oscillatory shear analysis shows that the storage and the loss modulus follow a power law behavior that are closely reminiscent of experimental observations. At large accumulated strains, the strain-induced reorganization of the gel may trigger flow heterogeneities and eventually lead to the yielding of the gel via a quasi brittle damage of its structure.

  19. Keystroke Dynamics-Based Credential Hardening Systems

    NASA Astrophysics Data System (ADS)

    Bartlow, Nick; Cukic, Bojan

    abstract Keystroke dynamics are becoming a well-known method for strengthening username- and password-based credential sets. The familiarity and ease of use of these traditional authentication schemes combined with the increased trustworthiness associated with biometrics makes them prime candidates for application in many web-based scenarios. Our keystroke dynamics system uses Breiman’s random forests algorithm to classify keystroke input sequences as genuine or imposter. The system is capable of operating at various points on a traditional ROC curve depending on application-specific security needs. As a username/password authentication scheme, our approach decreases the system penetration rate associated with compromised passwords up to 99.15%. Beyond presenting results demonstrating the credential hardening effect of our scheme, we look into the notion that a user’s familiarity to components of a credential set can non-trivially impact error rates.

  20. Laser hardening process simulation for mechanical parts

    NASA Astrophysics Data System (ADS)

    Tani, G.; Orazi, L.; Fortunato, A.; Campana, G.; Cuccolini, G.

    2007-02-01

    In this paper a numerical simulation of laser hardening process is presented. The Finite Difference Method (FDM) was used to solve the heat transfer and the carbon diffusion equations for a defined workpiece geometry. The model is able to predict the thermal cycle into the target material, the phase transformations and the resulting micro-structures according to the laser parameters, the workpiece dimensions and the physical properties of the workpiece. The effects of the overlapping tracks of the laser beam on the resulting micro-structures is also considered. The initial workpiece micro-structure is taken into account in the simulation by a digitized photomicrograph of the ferrite perlite distribution before the thermal cycle. Experimental tests were realized on a C43 plate and the good agreement between the theoretical and experimental results is shown.

  1. Jerky loads on surface-hardened gears

    NASA Technical Reports Server (NTRS)

    Rettig, H.; Wirth, X.

    1978-01-01

    Damage occurs again and again in practice in the form of transmissions with surface hardened gears which break after a very long operating time (explained by seldom occurring jerky loads). Gear drives are frequently exposed to jerky stresses which are greater than their fatigue limit. These stresses are considered in gear calculations, first, by shock factors when the transmission is to be designed as high endurance with regard to overloads and, second, in the form of operating ratios when the design is to be time enduring with regard to overloads. The size of the operating ratio depends not only on torque characteristics, drive and processing machine, but also on the material and heat treatment.

  2. Dilatant hardening of fluid-saturated sandstone

    NASA Astrophysics Data System (ADS)

    Makhnenko, Roman Y.; Labuz, Joseph F.

    2015-02-01

    The presence of pore fluid in rock affects both the elastic and inelastic deformation processes, yet laboratory testing is typically performed on dry material even though in situ the rock is often saturated. Techniques were developed for testing fluid-saturated porous rock under the limiting conditions of drained, undrained, and unjacketed response. Confined compression experiments, both conventional triaxial and plane strain, were performed on water-saturated Berea sandstone to investigate poroelastic and inelastic behavior. Measured drained response was used to calibrate an elasto-plastic constitutive model that predicts undrained inelastic deformation. The experimental data show good agreement with the model: dilatant hardening in undrained triaxial and plane strain compression tests under constant mean stress was predicted and observed.

  3. Precipitation hardening in 350 grade maraging steel

    SciTech Connect

    Viswanathan, U.K. . Radiometallurgy Div.); Dey, G.K. . Metallurgy Division); Asundi, M.K. )

    1993-11-01

    Evolution of microstructure in 350 grade commercial maraging steel has been examined. In the earlier stages of aging, the strengthening phases are formed by the heterogeneous precipitation, and these phases have been identified as intermetallic compounds of the Ni[sub 3] (Ti, Mo) and Fe[sub 2]Mo types. The kinetics of precipitation are studied in terms of the activation energy by carrying out isothermal hardness measurements of aged material. The mechanical properties in the peak-aged and overaged conditions were evaluated and the flow behavior examined. The overaging behavior of the steel has been studied and the formation of austenite of different morphologies identified. The crystallography of the austenite has been examined in detail. From the microstructural examination of peak-aged and deformed samples, it could be inferred that the dislocation-precipitate interaction is by precipitate shearing. Increased work hardening of the material in the overaged condition was suggestive of looping of precipitates by dislocations.

  4. Volcanic CO2 as a major agent of weathering in volcanic regions

    NASA Astrophysics Data System (ADS)

    Rive, K.; Gaillardet, J.; Agrinier, P.; Rad, S.

    2007-12-01

    According to high erosion rates, weathering of volcanic areas is one of the main processes controlling the atmospheric CO2 levels (e.g. Louvat, 1997, Dessert et al., 2003). So far, the origin of CO2 was assumed to be mainly atmospheric. The origin and consumption rates of CO2 can be estimated using concentration of Dissolved Inorganic Carbon (DIC ~ bicarbonates) in the rivers and carbon stable isotopes. The processes governing the CO2 consumption by chemical weathering were studied in four volcanic areas, with climates from tropical to sub-polar, in different geodynamic contexts. Lesser Antilles, Reunion, Iceland and French Massif Central are ideal sites for the study of weathering due to the gradients of rainfall (up to 14m/yr), rock ages (tertiary to subactual) and volcanic activities, inducing variable weathering rates (50- 400t/km\\2/yr). δ13CDIC and major elements chemistry were studied in streams, springs and soil solutions of these four areas. The δ13CDIC and major elements concentrations are highly variable, and allow us to identify the origin of DIC as a mixing between biogenic CO2 (average value of δ13C ~ - 29.1±2.0‰ in tropical areas, -26‰ in temperate to sub-polar climate) and volcanic CO2 (δ13CDIC = -5 to 3‰). We found that volcanic CO2 is a major source of carbon, the highest contribution being for zones with high infiltration of water (up to 100\\percent of DIC for Piton de la Fournaise in Reunion). As inferred by Rad et al. (2007) from major elements, this isotopic study of the DIC cycling in the river demonstrates the importance of the volcanic fluids on chemical weathering processes.

  5. 1992-93 Results of geomorphological and field studies Volcanic Studies Program, Yucca Mountain Project

    SciTech Connect

    Wells, S.G.

    1993-10-01

    Field mapping and stratigraphic studies were completed of the Black Tank volcanic center, which represents the southwestern most eruptive center in the Cima volcanic field of California. The results of this mapping are presented. Contacts between volcanic units and geomorphic features were field checked, incorporating data from eight field trenches as well as several exposures along Black Tank Wash. Within each of the eight trenches, logs were measured and stratigraphic sections were described. These data indicate that three, temporally separate volcanic eruptions occurred at the Black Tank center. The field evidence for significant time breaks between each stratigraphic unit is the presence of soil and pavement-bounded unconformities.

  6. Exploring Hawaiian volcanism

    USGS Publications Warehouse

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

    2013-01-01

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

  7. Volcanism-Climate Interactions

    NASA Technical Reports Server (NTRS)

    Walter, Louis S. (Editor); Desilva, Shanaka (Editor)

    1991-01-01

    The range of disciplines in the study of volcanism-climate interactions includes paleoclimate, volcanology, petrology, tectonics, cloud physics and chemistry, and climate and radiation modeling. Questions encountered in understanding the interactions include: the source and evolution of sulfur and sulfur-gaseous species in magmas; their entrainment in volcanic plumes and injection into the stratosphere; their dissipation rates; and their radiative effects. Other issues include modeling and measuring regional and global effects of such large, dense clouds. A broad-range plan of research designed to answer these questions was defined. The plan includes observations of volcanoes, rocks, trees, and ice cores, as well as satellite and aircraft observations of erupting volcanoes and resulting lumes and clouds.

  8. Volcanic effects on climate

    NASA Technical Reports Server (NTRS)

    Robock, Alan

    1991-01-01

    Volcanic eruptions which inject large amounts of sulfur-rich gas into the stratosphere produce dust veils which last years and cool the earth's surface. At the same time, these dust veils absorb enough solar radiation to warm the stratosphere. Since these temperature changes at the earth's surface and in the stratosphere are both in the opposite direction of hypothesized effects from greenhouse gases, they act to delay and mask the detection of greenhouse effects on the climate system. Tantalizing recent research results have suggested regional effects of volcanic eruptions, including effects on El Nino/Southern Oscillation (ENSO). In addition, a large portion of the global climate change of the past 100 years may be due to the effects of volcanoes, but a definite answer is not yet clear. While effects of several years were demonstrated with both data studies and numerical models, long-term effects, while found in climate model calculations, await confirmation with more realistic models. Extremely large explosive prehistoric eruptions may have produced severe weather and climate effects, sometimes called a 'volcanic winter'. Complete understanding of the above effects of volcanoes is hampered by inadequacies of data sets on volcanic dust veils and on climate change. Space observations can play an increasingly important role in an observing program in the future. The effects of volcanoes are not adequately separated from ENSO events, and climate modeling of the effects of volcanoes is in its infancy. Specific suggestions are made for future work to improve the knowledge of this important component of the climate system.

  9. Reducing volcanic risk

    USGS Publications Warehouse

    Decker, R.; Decker, B.

    1991-01-01

    The last two decades have brought major advances in research on how volcanoes work and how to monitor their changing habits. Geologic mapping as well as studies of earthquake patterns and surface deformation associated with underground movement of magma have given scientists a better view of the inner structure and dynamics of active volcanoes. With the next decade, the time has come to focuses more on applying this knowledge toward reducing the risk from volcanic activity on a worldwide basis. 

  10. Properties of modified anhydride hardener and its cured resin

    NASA Astrophysics Data System (ADS)

    Qiang, Chen; Bingjun, Gao; Jinglin, Chen; Tongzhao, Xu

    2000-01-01

    Methyl-nadic-tetrahydric-methylanhydride (MNA), nadic-tetrahydric-methylanhydride (NA), anhydride hardener was modified by solid diol molecule to improve the impregnation resin fracture toughness in cryogenic temperature. The lap-shear strength, transverse tension as well as the thermal shock test showed that the resin cured by the modified anhydride hardener had higher bond strength and more toughness at 77 K. After the experiment of vacuum pressure impregnation (VPI) processing, it was found that this resin had a longer usable life, better impregnating properties, but higher initial viscosity than the resin hybrid HY925 as hardener.

  11. Strain hardening of metal parts with use of impulse wave

    NASA Astrophysics Data System (ADS)

    Kirichek, A. V.; Soloviev, D. L.

    2016-04-01

    This work describes a strain hardening method with the use of impulse waves. This method increases energy transfer to the strained material extending its technological capabilities with development of a deep strengthened layer and allowing formation of a heterogeneous hardened structure using plastic deformation. This structure has specified distribution of the hard and soft (visco-plastic) areas. Due to development of the heterogeneous structure in the surface layer created by strain hardening with impulse wave, durability of parts that suffer contact fatigue loading is significantly increased.

  12. Do volcanic earthquake swarms relate to their volcanic setting?

    NASA Astrophysics Data System (ADS)

    Buurman, H.; West, M. E.; De Angelis, S.

    2013-12-01

    Determining whether a volcanic earthquake swarm will culminate in an eruption is arguably one of the most important unanswered questions in volcano seismology. Although swarms are generally thought to result when magma ascends through the crust, they do not always result in volcanic eruptions and are not always accompanied by significant crustal deformation, suggesting that magma ascent may not always be the source of the activity. We examine whether the volcanic setting influences the behavior of volcanic seismic swarms by comparing the characteristics of seismic swarms recorded in a wide variety of provenances. Our dataset comprises swarms recorded at volcanoes in continental and oceanic arcs, including the Cascade and Aleutian arcs, and hot spot settings such as Iceland and Yellowstone. We begin by defining a number of metrics such as hypocentral distribution, magnitude distribution, earthquake rates and swarm duration to place the different swarms in a context across which comparisons can be made. We then search for correlations between these swarm parameters that can be related to their volcanic setting. Grouping swarms according to their volcanic setting allows us to relate the earthquake sources more directly to the movement of magma in the crust, since magma properties such as viscosity are known to vary substantially between different volcanic regions. Understanding how the behavior of swarms changes according to the volcanic provenance is a crucial step towards understanding how magma is transported through the crust, and consequently with our ability to assess the eruptive potential of volcanic seismic swarms.

  13. Acidic volatiles and the Mars Soil

    NASA Astrophysics Data System (ADS)

    Banin, A.; Han, F. X.; Kan, I.; Cicelsky, A.

    1997-06-01

    Large portions of Mars' surface are covered with deposits of fine, homogeneous, weathered dusty-soil material. Nanophase iron oxides, silicate mineraloids, and salts prevail in the soil. The mode of formation of this somewhat peculiar type of soil is still far from being clear. One scenario suggests that weathering took place during early epochs when Mars may have been ``warm and wet.'' The properties of the soil are not easily reconciled with this scenario. We propose another possible scenario that attributes, in part, the peculiar nature of the Martian dust and soil to a relatively ``young'' weathering product formed during the last few hundreds of millions of years in a process that involves acidic volatiles. We tested this hypothesis in an experimental study of the first step of acidolytic weathering of a partly palagonitized volcanic tephra of hawaiitic lava origin, using sulfuric, hydrochloric and nitric acids and their mixtures. The tephra effectively ``neutralize'' the added acidity. The protonic acidity added to the tephra attacks the primary minerals, releasing Fe, Al, and Mg, which control the pH, acting as Lewis-acid species of varying acid strengths. The full amount of acidity added to the tephra is stored in it, but only a very small fraction is preserved as the original protonic acidity. The majority of the added sulfate and chloride were present as salts and easily solubilized minerals. Well-crystallized sulfate salt minerals of aluminum and calcium were detected by powder X ray diffractometry, whereas secondary magnesium and iron minerals were not detected, due probably to lack of crystallinity. The presence of gypsum (CaSO4.2H2O) and alunogen (Al2(SO4)3.17H2O) is probably responsible for the observed increased hygroscopicity of the acidified tephra and their tendency to form hardened crusts. We suggest that if this mechanism is of importance on Mars, then the chemically weathered component of the Martian soil consists of a salt-rich mineral

  14. Beam Hardening Corrections in Quantitative Computed Tomography

    SciTech Connect

    Vedula, Venumadhav; Venugopal, Manoharan; Raghu, C.; Pandey, Pramod

    2007-03-21

    Volumetric computed tomography (VCT) is the emerging 3D NDE inspection technique that gives highest throughput and better image quality. Industrial components in general demands higher x-ray energy for inspection for which polychromatic x-ray sources are used in common. Polychromatic nature of the x-rays gives rise to non-linear effects in the VCT projection data measurements called to be the beam hardening (BH) effects. BH produces prominent artifacts in the reconstructed images thereby deteriorating the image quality. Quantitative analysis such as density quantification, dimensional analysis etc., becomes difficult with the presence of these artifacts. This paper describes the BH correction using preprocessing technique for the homogeneous materials. Selection of effective energy at which the monoenergetic linear attenuation coefficient of a particular material equals to that of the polyenergetic beam is critical for BH correction. Various methods to determine the effective energy and their consequence in the quantitative measurements have been investigated in the present study. In this paper, BH corrections for heterogeneous materials have also been explored.

  15. Design concepts for hardened communications structures

    NASA Astrophysics Data System (ADS)

    Flathau, William J.; Smith, William G.

    1990-03-01

    An important component of any hardened command and control structure is the antenna system that provides communication with the outside world. Two types of antennae were considered; i.e., the whip type and the directional. The whip type is for short range communication and the directional is for use primarily with satellites. In the super high frequency range, the use of directional antennae having parabolic dishes greater than 8 feet in diameter are common. In the very extra high frequency range, dishes that are 2 to 3 feet in diameter are used. The whip type antenna should extend up to, say, 60 feet in the air. Based on this background, a family of structures was designed that can protect whip and directional antennae from the blast and shock effects from a 1-MT device for ground surface overpressure ranging from 15,000 to 500 psi. As the antennae, transmitters, receivers, power supplies, and lifting mechanisms will be located within such structures, appropriate shock spectra plots were developed to determine if the fragility level of pertinent equipment will be exceeded and for use in designing shock isolation systems. Button up periods of 1 and 4 weeks were considered.

  16. Weldable, age hardenable, austenitic stainless steel

    DOEpatents

    Brooks, J.A.; Krenzer, R.W.

    1975-07-22

    An age hardenable, austenitic stainless steel having superior weldability properties as well as resistance to degradation of properties in a hydrogen atmosphere is described. It has a composition of from about 24.0 to about 34.0 weight percent (w/o) nickel, from about 13.5 to about 16.0 w/o chromium, from about 1.9 to about 2.3 w/o titanium, from about 1.0 to about 1.5 w/ o molybdenum, from about 0.01 to about 0.05 w/o carbon, from about 0 to about 0.25 w/o manganese, from about 0 to about 0.01 w/o phosphorous and preferably about 0.005 w/o maximum, from about 0 to about 0.010 w/o sulfur and preferably about 0.005 w/o maximum, from about 0 to about 0.25 w/o silicon, from about 0.1 to about 0.35 w/o aluminum, from about 0.10 to about 0.50 w/o vanadium, from about 0 to about 0.0015 w/o boron, and the balance essentially iron. (auth)

  17. Cyber situational awareness and differential hardening

    NASA Astrophysics Data System (ADS)

    Dwivedi, Anurag; Tebben, Dan

    2012-06-01

    The advent of cyber threats has created a need for a new network planning, design, architecture, operations, control, situational awareness, management, and maintenance paradigms. Primary considerations include the ability to assess cyber attack resiliency of the network, and rapidly detect, isolate, and operate during deliberate simultaneous attacks against the network nodes and links. Legacy network planning relied on automatic protection of a network in the event of a single fault or a very few simultaneous faults in mesh networks, but in the future it must be augmented to include improved network resiliency and vulnerability awareness to cyber attacks. Ability to design a resilient network requires the development of methods to define, and quantify the network resiliency to attacks, and to be able to develop new optimization strategies for maintaining operations in the midst of these newly emerging cyber threats. Ways to quantify resiliency, and its use in visualizing cyber vulnerability awareness and in identifying node or link criticality, are presented in the current work, as well as a methodology of differential network hardening based on the criticality profile of cyber network components.

  18. Quantitative Studies in Planetary Volcanism

    NASA Technical Reports Server (NTRS)

    Baloga, Stephen M.

    2004-01-01

    Proxemy Research has a research grant to perform scientific investigations of volcanism and volcanic-related process on other planets. Part of this research involves mathematical modeling of specific volcanic transport processes and the use of terrestrial analogs. This report contains a summary of activities conducted over the time period indicated. In addition, a synopsis of science research conducted during the period is given. A complete listing of publications and scientific abstracts that were presented at scientific conferences is contained in the report.

  19. Volcanism on Mars. Chapter 41

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

  20. Planetary volcanism - A study of volcanic activity in the solar system

    NASA Technical Reports Server (NTRS)

    Cattermole, Peter

    1989-01-01

    The nature of volcanic activity, theoretical models of its role in planetary evolution, and the evidence for volcanism on the planets and planetary satellites are examined in an introductory overview for advanced undergraduate and graduate students. Chapters are devoted to volcanism as a planetary process, the generation and evolution of magmas, magma ascent and eruption, the properties and behavior of volcanic flows, volcanic landforms, the distribution of volcanic rocks in the solar system, and volcanic plains and their development. Consideration is given to lunar volcanism, shield volcanoes and paterae, volcanism on Io, volcanism on icy satellites, and the rheological analysis of volcanic flows.

  1. Microscopic Origin of Strain Hardening in Methane Hydrate

    PubMed Central

    Jia, Jihui; Liang, Yunfeng; Tsuji, Takeshi; Murata, Sumihiko; Matsuoka, Toshifumi

    2016-01-01

    It has been reported for a long time that methane hydrate presents strain hardening, whereas the strength of normal ice weakens with increasing strain after an ultimate strength. However, the microscopic origin of these differences is not known. Here, we investigated the mechanical characteristics of methane hydrate and normal ice by compressive deformation test using molecular dynamics simulations. It is shown that methane hydrate exhibits strain hardening only if the hydrate is confined to a certain finite cross-sectional area that is normal to the compression direction. For normal ice, it does not present strain hardening under the same conditions. We show that hydrate guest methane molecules exhibit no long-distance diffusion when confined to a finite-size area. They appear to serve as non-deformable units that prevent hydrate structure failure, and thus are responsible for the strain-hardening phenomenon. PMID:27009239

  2. Possible correlation between work-hardening and fatigue-failure

    NASA Technical Reports Server (NTRS)

    Kettunen, P. O.; Kocks, U. F.

    1969-01-01

    Conceptual theory proposes that cyclic hardening due to non-uniform strain and stress amplitudes during testing, especially during the initial application of stress to a specimen, may correlate positively with the ultimate strength of the specimen under test.

  3. Stress corrosion cracking evaluation of precipitation-hardening stainless steel

    NASA Technical Reports Server (NTRS)

    Humphries, T. S.; Nelson, E. E.

    1970-01-01

    Accelerated test program results show which precipitation hardening stainless steels are resistant to stress corrosion cracking. In certain cases stress corrosion susceptibility was found to be associated with the process procedure.

  4. Microscopic Origin of Strain Hardening in Methane Hydrate.

    PubMed

    Jia, Jihui; Liang, Yunfeng; Tsuji, Takeshi; Murata, Sumihiko; Matsuoka, Toshifumi

    2016-01-01

    It has been reported for a long time that methane hydrate presents strain hardening, whereas the strength of normal ice weakens with increasing strain after an ultimate strength. However, the microscopic origin of these differences is not known. Here, we investigated the mechanical characteristics of methane hydrate and normal ice by compressive deformation test using molecular dynamics simulations. It is shown that methane hydrate exhibits strain hardening only if the hydrate is confined to a certain finite cross-sectional area that is normal to the compression direction. For normal ice, it does not present strain hardening under the same conditions. We show that hydrate guest methane molecules exhibit no long-distance diffusion when confined to a finite-size area. They appear to serve as non-deformable units that prevent hydrate structure failure, and thus are responsible for the strain-hardening phenomenon. PMID:27009239

  5. Ultimate bending capacity of strain hardening steel pipes

    NASA Astrophysics Data System (ADS)

    Chen, Yan-fei; Zhang, Juan; Zhang, Hong; Li, Xin; Zhou, Jing; Cao, Jing

    2016-04-01

    Based on Hencky's total strain theory of plasticity, ultimate bending capacity of steel pipes can be determined analytically assuming an elastic-linear strain hardening material, the simplified analytical solution is proposed as well. Good agreement is observed when ultimate bending capacities obtained from analytical solutions are compared with experimental results from full-size tests of steel pipes. Parametric study conducted as part of this paper indicates that the strain hardening effect has significant influence on the ultimate bending capacity of steel pipes. It is shown that pipe considering strain hardening yields higher bending capacity than that of pipe assumed as elastic-perfectly plastic material. Thus, the ignorance of strain hardening effect, as commonly assumed in current codes, may underestimate the ultimate bending capacity of steel pipes. The solutions proposed in this paper are applicable in the design of offshore/onshore steel pipes, supports of offshore platforms and other tubular structural steel members.

  6. Computed tomographic beam-hardening artefacts: mathematical characterization and analysis

    PubMed Central

    Park, Hyoung Suk; Chung, Yong Eun; Seo, Jin Keun

    2015-01-01

    This paper presents a mathematical characterization and analysis of beam-hardening artefacts in X-ray computed tomography (CT). In the field of dental and medical radiography, metal artefact reduction in CT is becoming increasingly important as artificial prostheses and metallic implants become more widespread in ageing populations. Metal artefacts are mainly caused by the beam-hardening of polychromatic X-ray photon beams, which causes mismatch between the actual sinogram data and the data model being the Radon transform of the unknown attenuation distribution in the CT reconstruction algorithm. We investigate the beam-hardening factor through a mathematical analysis of the discrepancy between the data and the Radon transform of the attenuation distribution at a fixed energy level. Separation of cupping artefacts from beam-hardening artefacts allows causes and effects of streaking artefacts to be analysed. Various computer simulations and experiments are performed to support our mathematical analysis. PMID:25939628

  7. Computed tomographic beam-hardening artefacts: mathematical characterization and analysis.

    PubMed

    Park, Hyoung Suk; Chung, Yong Eun; Seo, Jin Keun

    2015-06-13

    This paper presents a mathematical characterization and analysis of beam-hardening artefacts in X-ray computed tomography (CT). In the field of dental and medical radiography, metal artefact reduction in CT is becoming increasingly important as artificial prostheses and metallic implants become more widespread in ageing populations. Metal artefacts are mainly caused by the beam-hardening of polychromatic X-ray photon beams, which causes mismatch between the actual sinogram data and the data model being the Radon transform of the unknown attenuation distribution in the CT reconstruction algorithm. We investigate the beam-hardening factor through a mathematical analysis of the discrepancy between the data and the Radon transform of the attenuation distribution at a fixed energy level. Separation of cupping artefacts from beam-hardening artefacts allows causes and effects of streaking artefacts to be analysed. Various computer simulations and experiments are performed to support our mathematical analysis. PMID:25939628

  8. Formation and deposition of volcanic sulfate aerosols on Mars

    NASA Technical Reports Server (NTRS)

    Settle, M.

    1979-01-01

    The paper considers the formation and deposition of volcanic sulfate aerosols on Mars. The rate limiting step in sulfate aerosol formation on Mars is the gas phase oxidation of SO2 by chemical reactions with O, OH, and HO2; submicron aerosol particles would circuit Mars and then be removed from the atmosphere by gravitational forces, globally dispersed, and deposited over a range of equatorial and mid-latitudes. Volcanic sulfate aerosols on Mars consist of liquid droplets and slurries containing sulfuric acid; aerosol deposition on a global or hemispheric scale could account for the similar concentrations of sulfur within surficial soils at the two Viking lander sites.

  9. Volcanic Eruptions and Climate

    NASA Astrophysics Data System (ADS)

    Robock, A.

    2012-12-01

    Large volcanic eruptions inject sulfur gases into the stratosphere, which convert to sulfate aerosols with an e-folding residence time of about one year. The radiative and chemical effects of these aerosol clouds produce responses in the climate system. Observations and numerical models of the climate system show that volcanic eruptions produce global cooling and were the dominant natural cause of climate change for the past millennium, on timescales from annual to century. Major tropical eruptions produce winter warming of Northern Hemisphere continents for one or two years, while high latitude eruptions in the Northern Hemisphere weaken the Asian and African summer monsoon. The Toba supereruption 74,000 years ago caused very large climate changes, affecting human evolution. However, the effects did not last long enough to produce widespread glaciation. An episode of four large decadally-spaced eruptions at the end of the 13th century C.E. started the Little Ice Age. Since the Mt. Pinatubo eruption in the Philippines in 1991, there have been no large eruptions that affected climate, but the cumulative effects of small eruptions over the past decade had a small effect on global temperature trends. The June 13, 2011 Nabro eruption in Eritrea produced the largest stratospheric aerosol cloud since Pinatubo, and the most of the sulfur entered the stratosphere not by direct injection, but by slow lofting in the Asian summer monsoon circulation. Volcanic eruptions warn us that while stratospheric geoengineering could cool the surface, reducing ice melt and sea level rise, producing pretty sunsets, and increasing the CO2 sink, it could also reduce summer monsoon precipitation, destroy ozone, allowing more harmful UV at the surface, produce rapid warming when stopped, make the sky white, reduce solar power, perturb the ecology with more diffuse radiation, damage airplanes flying in the stratosphere, degrade astronomical observations, affect remote sensing, and affect

  10. Strain hardening of fcc metal surfaces induced by microploughing

    SciTech Connect

    Day, R.D.; Dickerson, R.M.; Russell, P.E.

    1998-12-01

    Microploughing experiments were used as a method for better understanding the ploughing mechanism in gold and iridium single crystals. The plough depths ranged from 20 nm in iridium to 1,600 nm in gold. Yield stress profiles and TEM analyses indicate that both materials strain harden even when very small volumes of material are involved. Strain hardening theory, as applied to bulk material, is useful in analyzing the results.

  11. Recurrence rates of volcanism in basaltic volcanic fields: An example from the Springerville volcanic field, Arizona

    SciTech Connect

    Condit, C.D.; Connor, C.B.

    1996-10-01

    A spatio-temporal near-neighbor model is used to identify and map variations in the recurrence rate of volcanism in the Springerville volcanic field, Arizona, a large field on the Colorado Plateau boundary. Detailed mapping of individual lava flows and their associated vents, together with radiometric and paleomagnetic dating, demonstrates that 366 volcanic events have formed the Springerville volcanic field. A near-neighbor spatio-temporal recurrence-rate model using seven near-neighbor volcanoes and a 0.5 m.y. time window reveals that (1) areas of waxing and waning magmatism in the Springerville volcanic field are much more localized and (2) volcanic activity within these areas is much more intense than implied by field-wide temporal trends. Because volcanic activity is spatially and temporally clustered, forecasting subsequent activity is more successful if the spatio-temporal recurrence-rate model is used, rather than the average recurrence rates. This success indicates that spatio-temporal recurrence-rate models are useful tools for the quantification of long-term volcanic hazards in basaltic volcanic fields. 61 refs., 13 figs., 2 tabs.

  12. Zinc coated sheet steel for press hardening

    NASA Astrophysics Data System (ADS)

    Ghanbari, Zahra N.

    Galvanized steels are of interest to enhance corrosion resistance of press-hardened steels, but concerns related to liquid metal embrittlement have been raised. The objective of this study was to assess the soak time and temperature conditions relevant to the hot-stamping process during which Zn penetration did or did not occur in galvanized 22MnB5 press-hardening steel. A GleebleRTM 3500 was used to heat treat samples using hold times and temperatures similar to those used in industrial hot-stamping. Deformation at both elevated temperature and room temperature were conducted to assess the coating and substrate behavior related to forming (at high temperature) and service (at room temperature). The extent of alloying between the coating and substrate was assessed on undeformed samples heat treated under similar conditions to the deformed samples. The coating transitioned from an α + Gamma1 composition to an α (bcc Fe-Zn) phase with increased soak time. This transition likely corresponded to a decrease in availability of Zn-rich liquid in the coating during elevated temperature deformation. Penetration of Zn into the substrate sheet in the undeformed condition was not observed for any of the processing conditions examined. The number and depth of cracks in the coating and substrate steel was also measured in the hot-ductility samples. The number of cracks appeared to increase, while the depth of cracks appeared to decrease, with increasing soak time and increasing soak temperature. The crack depth appeared to be minimized in the sample soaked at the highest soak temperature (900 °C) for intermediate and extended soak times (300 s or 600 s). Zn penetration into the substrate steel was observed in the hot-ductility samples soaked at each hold temperature for the shortest soak time (10 s) before being deformed at elevated temperature. Reduction of area and elongation measurements showed that the coated sample soaked at the highest temperature and longest soak time

  13. Volcanic Eruptions and Climate

    NASA Technical Reports Server (NTRS)

    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.

  14. Extracting material response from simple mechanical tests on hardening-softening-hardening viscoplastic solids

    NASA Astrophysics Data System (ADS)

    Mohan, Nisha

    Compliant foams are usually characterized by a wide range of desirable mechanical properties. These properties include viscoelasticity at different temperatures, energy absorption, recoverability under cyclic loading, impact resistance, and thermal, electrical, acoustic and radiation-resistance. Some foams contain nano-sized features and are used in small-scale devices. This implies that the characteristic dimensions of foams span multiple length scales, rendering modeling their mechanical properties difficult. Continuum mechanics-based models capture some salient experimental features like the linear elastic regime, followed by non-linear plateau stress regime. However, they lack mesostructural physical details. This makes them incapable of accurately predicting local peaks in stress and strain distributions, which significantly affect the deformation paths. Atomistic methods are capable of capturing the physical origins of deformation at smaller scales, but suffer from impractical computational intensity. Capturing deformation at the so-called meso-scale, which is capable of describing the phenomenon at a continuum level, but with some physical insights, requires developing new theoretical approaches. A fundamental question that motivates the modeling of foams is `how to extract the intrinsic material response from simple mechanical test data, such as stress vs. strain response?' A 3D model was developed to simulate the mechanical response of foam-type materials. The novelty of this model includes unique features such as the hardening-softening-hardening material response, strain rate-dependence, and plastically compressible solids with plastic non-normality. Suggestive links from atomistic simulations of foams were borrowed to formulate a physically informed hardening material input function. Motivated by a model that qualitatively captured the response of foam-type vertically aligned carbon nanotube (VACNT) pillars under uniaxial compression [2011,"Analysis of

  15. Terrestrial volcanism in space and time

    NASA Technical Reports Server (NTRS)

    Simkin, Tom

    1993-01-01

    A survey is presented of current volcanic activity around the world and of dated volcanism over the past 10,000 yrs. The patterns in the data are described. The hazard presented by volcanism is briefly examined.

  16. Rapid response of a hydrologic system to volcanic activity: Masaya volcano, Nicaragua

    USGS Publications Warehouse

    Pearson, S.C.P.; Connor, C.B.; Sanford, W.E.

    2008-01-01

    Hydrologic systems change in response to volcanic activity, and in turn may be sensitive indicators of volcanic activity. Here we investigate the coupled nature of magmatic and hydrologic systems using continuous multichannel time series of soil temperature collected on the flanks of Masaya volcano, Nicaragua, one of the most active volcanoes in Central America. The soil temperatures were measured in a low-temperature fumarole field located 3.5 km down the flanks of the volcano. Analysis of these time series reveals that they respond extremely rapidly, on a time scale of minutes, to changes in volcanic activity also manifested at the summit vent. These rapid temperature changes are caused by increased flow of water vapor through flank fumaroles during volcanism. The soil temperature response, ~5 °C, is repetitive and complex, with as many as 13 pulses during a single volcanic episode. Analysis of the frequency spectrum of these temperature time series shows that these anomalies are characterized by broad frequency content during volcanic activity. They are thus easily distinguished from seasonal trends, diurnal variations, or individual rainfall events, which triggered rapid transient increases in temperature during 5% of events. We suggest that the mechanism responsible for the distinctive temperature signals is rapid change in pore pressure in response to magmatism, a response that can be enhanced by meteoric water infiltration. Monitoring of distal fumaroles can therefore provide insight into coupled volcanic-hydrologic-meteorologic systems, and has potential as an inexpensive monitoring tool.

  17. High-Performance, Radiation-Hardened Electronics for Space Environments

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Watson, Michael D.; Frazier, Donald O.; Adams, James H.; Johnson, Michael A.; Kolawa, Elizabeth A.

    2007-01-01

    The Radiation Hardened Electronics for Space Environments (RHESE) project endeavors to advance the current state-of-the-art in high-performance, radiation-hardened electronics and processors, ensuring successful performance of space systems required to operate within extreme radiation and temperature environments. Because RHESE is a project within the Exploration Technology Development Program (ETDP), RHESE's primary customers will be the human and robotic missions being developed by NASA's Exploration Systems Mission Directorate (ESMD) in partial fulfillment of the Vision for Space Exploration. Benefits are also anticipated for NASA's science missions to planetary and deep-space destinations. As a technology development effort, RHESE provides a broad-scoped, full spectrum of approaches to environmentally harden space electronics, including new materials, advanced design processes, reconfigurable hardware techniques, and software modeling of the radiation environment. The RHESE sub-project tasks are: SelfReconfigurable Electronics for Extreme Environments, Radiation Effects Predictive Modeling, Radiation Hardened Memory, Single Event Effects (SEE) Immune Reconfigurable Field Programmable Gate Array (FPGA) (SIRF), Radiation Hardening by Software, Radiation Hardened High Performance Processors (HPP), Reconfigurable Computing, Low Temperature Tolerant MEMS by Design, and Silicon-Germanium (SiGe) Integrated Electronics for Extreme Environments. These nine sub-project tasks are managed by technical leads as located across five different NASA field centers, including Ames Research Center, Goddard Space Flight Center, the Jet Propulsion Laboratory, Langley Research Center, and Marshall Space Flight Center. The overall RHESE integrated project management responsibility resides with NASA's Marshall Space Flight Center (MSFC). Initial technology development emphasis within RHESE focuses on the hardening of Field Programmable Gate Arrays (FPGA)s and Field Programmable Analog

  18. Process design of press hardening with gradient material property influence

    SciTech Connect

    Neugebauer, R.; Schieck, F.; Rautenstrauch, A.

    2011-05-04

    Press hardening is currently used in the production of automotive structures that require very high strength and controlled deformation during crash tests. Press hardening can achieve significant reductions of sheet thickness at constant strength and is therefore a promising technology for the production of lightweight and energy-efficient automobiles. The manganese-boron steel 22MnB5 have been implemented in sheet press hardening owing to their excellent hot formability, high hardenability, and good temperability even at low cooling rates. However, press-hardened components have shown poor ductility and cracking at relatively small strains. A possible solution to this problem is a selective increase of steel sheet ductility by press hardening process design in areas where the component is required to deform plastically during crash tests. To this end, process designers require information about microstructure and mechanical properties as a function of the wide spectrum of cooling rates and sequences and austenitizing treatment conditions that can be encountered in production environments. In the present work, a Continuous Cooling Transformation (CCT) diagram with corresponding material properties of sheet steel 22MnB5 was determined for a wide spectrum of cooling rates. Heating and cooling programs were conducted in a quenching dilatometer. Motivated by the importance of residual elasticity in crash test performance, this property was measured using a micro-bending test and the results were integrated into the CCT diagrams to complement the hardness testing results. This information is essential for the process design of press hardening of sheet components with gradient material properties.

  19. Process design of press hardening with gradient material property influence

    NASA Astrophysics Data System (ADS)

    Neugebauer, R.; Schieck, F.; Rautenstrauch, A.

    2011-05-01

    Press hardening is currently used in the production of automotive structures that require very high strength and controlled deformation during crash tests. Press hardening can achieve significant reductions of sheet thickness at constant strength and is therefore a promising technology for the production of lightweight and energy-efficient automobiles. The manganese-boron steel 22MnB5 have been implemented in sheet press hardening owing to their excellent hot formability, high hardenability, and good temperability even at low cooling rates. However, press-hardened components have shown poor ductility and cracking at relatively small strains. A possible solution to this problem is a selective increase of steel sheet ductility by press hardening process design in areas where the component is required to deform plastically during crash tests. To this end, process designers require information about microstructure and mechanical properties as a function of the wide spectrum of cooling rates and sequences and austenitizing treatment conditions that can be encountered in production environments. In the present work, a Continuous Cooling Transformation (CCT) diagram with corresponding material properties of sheet steel 22MnB5 was determined for a wide spectrum of cooling rates. Heating and cooling programs were conducted in a quenching dilatometer. Motivated by the importance of residual elasticity in crash test performance, this property was measured using a micro-bending test and the results were integrated into the CCT diagrams to complement the hardness testing results. This information is essential for the process design of press hardening of sheet components with gradient material properties.

  20. Elysium Mons Volcanic Region

    NASA Technical Reports Server (NTRS)

    1998-01-01

    On July 4, 1998--the first anniversary of the Mars Pathfinder landing--Mars Global Surveyor's latest images were radioed to Earth with little fanfare. The images received on July 4, 1998, however, were very exciting because they included a rare crossing of the summit caldera of a major martian volcano. Elysium Mons is located at 25oN, 213oW, in the martian eastern hemisphere. Elysium Mons is one of three large volcanoes that occur on the Elysium Rise-- the others are Hecates Tholus (northeast of Elysium Mons) and Albor Tholus (southeast of Elysium Mons). The volcano rises about 12.5 kilometers (7.8 miles) above the surrounding plain, or about 16 kilometers (9.9 miles) above the martian datum-- the 'zero' elevation defined by average martian atmospheric pressure and the planet's radius.

    Elysium Mons was discovered by Mariner 9 in 1972. It differs in a number of ways from the familiar Olympus Mons and other large volcanoes in the Tharsis region. In particular, there are no obvious lava flows visible on the volcano's flanks. The lack of lava flows was apparent from the Mariner 9 images, but the new MOC high resolution image--obtained at 5.24 meters (17.2 feet) per pixel--illustrates that this is true even when viewed at higher spatial resolution.

    Elysium Mons has many craters on its surface. Some of these probably formed by meteor impact, but many show no ejecta pattern characteristic of meteor impact. Some of the craters are aligned in linear patterns that are radial to the summit caldera--these most likely formed by collapse as lava was withdrawn from beneath the surface, rather than by meteor impact. Other craters may have formed by explosive volcanism. Evidence for explosive volcanism on Mars has been very difficult to identify from previous Mars spacecraft images. This and other MOC data are being examined closely to better understand the nature and origin of volcanic features on Mars.

    The three MOC images, 40301 (red wide angle), 40302 (blue wide angle

  1. Volcanic studies at Katmai

    SciTech Connect

    Not Available

    1989-12-31

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

  2. Biogeochemistry and nitrogen cycling in an Arctic, volcanic ecosystem

    NASA Astrophysics Data System (ADS)

    Fogel, M. L.; Benning, L.; Conrad, P. G.; Eigenbrode, J.; Starke, V.

    2007-12-01

    As part of a study on Mars Analogue environments, the biogeochemistry of Sverrefjellet Volcano, Bocfjorden, Svalbard, was conducted and compared to surrounding glacial, thermal spring, and sedimentary environments. An understanding of how nitrogen might be distributed in a landscape that had extinct or very cold adapted, slow- growing extant organisms should be useful for detecting unknown life forms. From high elevations (900 m) to the base of the volcano (sea level), soil and rock ammonium concentrations were uniformly low, typically less than 1- 3 micrograms per gm of rock or soil. In weathered volcanic soils, reduced nitrogen concentrations were higher, and oxidized nitrogen concentrations lower. The opposite was found in a weathered Devonian sedimentary soil. Plants and lichens growing on volcanic soils have an unusually wide range in N isotopic compositions from -5 to +12‰, a range rarely measured in temperate ecosystems. Nitrogen contents and isotopic compositions of volcanic soils and rocks were strongly influenced by the presence or absence of terrestrial herbivores or marine avifauna with higher concentrations of N and elevated N isotopic compositions occurring as patches in areas immediately influenced by reindeer, Arctic fox ( Alopex lagopus), and marine birds. Because of the extreme conditions in this area, ephemeral deposition of herbivore feces results in a direct and immediate N pulses into the ecosystem. The lateral extent and distribution of marine- derived nitrogen was measured on a landscape scale surrounding an active fox den. Nitrogen was tracked from the bones of marine birds to soil to vegetation. Because of extreme cold, slow biological rates and nitrogen cycling, a mosaic of N patterns develops on the landscape scale.

  3. Anisotropic hardening model based on non-associated flow rule and combined nonlinear kinematic hardening for sheet materials

    NASA Astrophysics Data System (ADS)

    Taherizadeh, Aboozar; Green, Daniel E.; Yoon, Jeong W.

    2013-12-01

    A material model for more effective analysis of plastic deformation of sheet materials is presented in this paper. The model is capable of considering the following aspects of plastic deformation behavior of sheet materials: the anisotropy in yielding stresses in different directions by using a quadratic yield function (based on Hill's 1948 model and stress ratios), the anisotropy in work hardening by introducing non-constant flow stress hardening in different directions, the anisotropy in plastic strains in different directions by using a quadratic plastic potential function and non-associated flow rule (based on Hill's 1948 model and plastic strain ratios, r-values), and finally some of the cyclic hardening phenomena such as Bauschinger's effect and transient behavior for reverse loading by using a coupled nonlinear kinematic hardening (so-called Armstrong-Frederick-Chaboche model). Basic fundamentals of the plasticity of the model are presented in a general framework. Then, the model adjustment procedure is derived for the plasticity formulations. Also, a generic numerical stress integration procedure is developed based on backward-Euler method (so-called multi-stage return mapping algorithm). Different aspects of the model are verified for DP600 steel sheet. Results show that the new model is able to predict the sheet material behavior in both anisotropic hardening and cyclic hardening regimes more accurately. By featuring the above-mentioned facts in the presented constitutive model, it is expected that more accurate results can be obtained by implementing this model in computational simulations of sheet material forming processes. For instance, more precise results of springback prediction of the parts formed from highly anisotropic hardened materials or that of determining the forming limit diagrams is highly expected by using the developed material model.

  4. Volcanics oil bearing in Indonesia

    SciTech Connect

    Lukman, K.A.; Nyak, B.R.; Anditya, I.M. )

    1996-01-01

    The volcanic rock is seldom considered as good reservoir rocks. However, in Indonesia there is a volcanic layer called the Jatibarang Formation in Jatibarang Field, West Java, that has proven to be a producer of oil and gas of adequate amount. The lateral development of this rock extent along the whole of the basin, about 400 km over a Tertiary block-faulting system of the North West Java Basin. It is estimated that the volume of the spread is about 2360 km[sup 3]. Beside from the primary volcanic rock, the developing reservoir rock could also resulted from rework of massive volcanics or agglomerate, and other volcanic product resedimented as clastic deposits. The hydrocarbon is sourced from the younger Talang Aker Formation that is in direct contact with the reservoir rock. It migrated through the faults. Present cumulative production has reached 1.2 BBC and 2.7 TCFG, while speculative reserve is estimated at 4.0 BBO and 3 TCFG. Regionally, the volcanic rock of the Jatibarang Formation where the hydrocarbon is found is the result of eruptions along the magmatic trend during Late Cretaceous. In North West Java Basin, the trapping system includes both the structural and stratigraphic traps. Reservoir analysis yields pororsity values of around 16-25% and permeability of around 10 Darcies. It is concluded that there are good opportunities still left for hydrocarbon exploration in volcanic rocks. The study is discussed in detail, supported by data from cores and laboratories.

  5. Solute hardening and softening effects in B2 nickel aluminides

    SciTech Connect

    Pike, L.M.; Liu, C.T.; Anderson, I.M.; Chang, Y.A.

    1998-11-01

    The effect of substitutional solute additions including Fe, Mn, and Pd on the hardness of B2-ordered NiAl alloys was investigated. The solid solution hardening behavior of intermetallics is more complex than that of typical metallic solid solutions because of complications arising from the site preference of the solute as well as the effects of the solute on the concentrations of other point defects, e.g., vacancies and anti-site defects. For this reason, care was taken to experimentally establish solute site preferences and point defect concentrations in the NiAl alloys before analyzing the hardness data. By taking these factors into account it was possible to rationalize the observed unusual hardening effects. Three distinct categories of solid solution hardening behavior were encountered. The first was hardening by the solute addition itself. This was observed in the case of Pd additions to Al-poor NiAl. However, when fe or Mn is added to Al-poor NiAl a second category is observed; these elements are seen to soften the material. The third category of behavior is observed when Fe is added to NiAl with a constant Al concentration of 50 at. %. In this case it is vacancies, rather than solute atoms, which harden the material.

  6. Dynamic bake hardening of interstitial-free steels

    SciTech Connect

    Dehghani, K.; Jonas, J.J.

    2000-05-01

    Two types of dynamic strain aging (DSA) strengthening methods were investigated to determine their potentials for industrial use. They are referred to here as dynamic-static bake hardening (DSBH) and dynamic bake hardening (DBH). For this purpose, a 0.06 pct Ti interstitial-free (IF) steel was reheated to 900 C and cooled at 12 C/s to room temperature. It was then dynamically bake hardened in the temperature range 100 C to 250 C to strains of 2 to 8 pct at a strain rate of 10{sup {minus}3} s{sup {minus}1}. The tensile properties were determined before and after these treatments. It was found that the occurrence of DSA during dynamic baking led to significant increases in work-hardening rate as well as in the final strength. The results indicate that, for a given solute carbon level, the dynamically and then statically aged samples have higher strengths than those that are bake hardened in the conventional way.

  7. General analytical shakedown solution for structures with kinematic hardening materials

    NASA Astrophysics Data System (ADS)

    Guo, Baofeng; Zou, Zongyuan; Jin, Miao

    2016-04-01

    The effect of kinematic hardening behavior on the shakedown behaviors of structure has been investigated by performing shakedown analysis for some specific problems. The results obtained only show that the shakedown limit loads of structures with kinematic hardening model are larger than or equal to those with perfectly plastic model of the same initial yield stress. To further investigate the rules governing the different shakedown behaviors of kinematic hardening structures, the extended shakedown theorem for limited kinematic hardening is applied, the shakedown condition is then proposed, and a general analytical solution for the structural shakedown limit load is thus derived. The analytical shakedown limit loads for fully reversed cyclic loading and non-fully reversed cyclic loading are then given based on the general solution. The resulting analytical solution is applied to some specific problems: a hollow specimen subjected to tension and torsion, a flanged pipe subjected to pressure and axial force and a square plate with small central hole subjected to biaxial tension. The results obtained are compared with those in literatures, they are consistent with each other. Based on the resulting general analytical solution, rules governing the general effects of kinematic hardening behavior on the shakedown behavior of structure are clearly.

  8. Hazardous indoor CO2 concentrations in volcanic environments.

    PubMed

    Viveiros, Fátima; Gaspar, João L; Ferreira, Teresa; Silva, Catarina

    2016-07-01

    Carbon dioxide is one of the main soil gases released silently and permanently in diffuse degassing areas, both in volcanic and non-volcanic zones. In the volcanic islands of the Azores (Portugal) several villages are located over diffuse degassing areas. Lethal indoor CO2 concentrations (higher than 10 vol %) were measured in a shelter located at Furnas village, inside the caldera of the quiescent Furnas Volcano (S. Miguel Island). Hazardous CO2 concentrations were detected not only underground, but also at the ground floor level. Multivariate regression analysis was applied to the CO2 and environmental time series recorded between April 2008 and March 2010 at Furnas village. The results show that about 30% of the indoor CO2 variation is explained by environmental variables, namely barometric pressure, soil water content and wind speed. The highest indoor CO2 concentrations were recorded during bad weather conditions, characterized by low barometric pressure together with rainfall periods and high wind speed. In addition to the spike-like changes observed on the CO2 time series, long-term oscillations were also identified and appeared to represent seasonal variations. In fact, indoor CO2 concentrations were higher during winter period when compared to the dry summer months. Considering the permanent emission of CO2 in various volcanic regions of the world, CO2 hazard maps are crucial and need to be accounted by the land-use planners and authorities. PMID:27155095

  9. Closer look at lunar volcanism

    SciTech Connect

    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.

  10. Io. [theories concerning volcanic activity

    NASA Technical Reports Server (NTRS)

    Johnson, T. V.; Soderblom, L. A.

    1983-01-01

    A report on the continuing investigation of Io is presented. Gravitational resonance is discussed as the cause of Io's volcanism, and the volcanic activity is explained in terms of sulfur chemistry. Theories concerning the reasons for the two main types of volcanic eruptions on Io are advanced and correlated with geographical features of the satellite. The sulfur and silicate models of the calderas are presented, citing the strengths and weaknesses of each. Problems of the gravitational resonance theory of Io's heat source are then described. Finally, observations of Io planned for the Galileo mission are summarized.

  11. Quantitative Studies in Planetary Volcanism

    NASA Technical Reports Server (NTRS)

    Baloga, Stephen M.

    2001-01-01

    Scientific research was conducted on volcanic processes on Mars, Venus, Io, the moon, and the Earth. The achievements led to scientific advances in the understanding of volcanic plumes, lava flow emplacements, coronae, and regoliths on the solid surfaces. This research led to multiple publications on each of the main topics of the proposal. Research was also presented at the annual Lunar and Planetary Science Conference at Houston. Typically, this grant contributed to 3-4 presentations each year. This grant demonstrated, numerous times, the usefulness of NASA mission data for advancing the understanding of volcanic processes on other planetary surfaces and the Earth.

  12. Late Quaternary geology of small basaltic volcanic centers, SW USA: Disparity among dating methods and implications for volcanic and geomorphic studies

    SciTech Connect

    Wells, S.; McFadden, L.; Perry, F.; Forman, S.; Crowe, B.; Pothis, J.; Olinger, C.

    1992-12-31

    Evaluation of volcanic hazards near the proposed high-level radioactive waste repository at Yucca Mountain provides the impetus for a series of detailed field and geochronologic studies of selected small late Quaternary basaltic scoria cones and lava flows in Nevada and California. Two of the most significant results of these studies are: the presence of chronostratigraphic units which indicate multiple eruptions with significant intervals of no activity between events (polycyclic volcanism); and a marked difference between conventional, numerical ages derived from K-Ar and Ar-40/Ar-39 methods and numerical, calibrated, and relative ages derived from thermoluminescence, cosmogenic He-3, the degree of soil development, and geomorphology of these volcanic landforms. Soil-bounded unconformities and buried stone pavements define the boundaries of chronostratigraphic units within these small volume basaltic centers. Volcanic centers displaying this type of stratigraphy may appear morphological simple but cannot be considered mongenetic. Recent studies by Perry and Crowe demonstrate that geochemical variations within a single basaltic volcanic center in NV are consistent with several magma batches forming a complex polycyclic volcano. The K-Ar and Ar-40/Ar-39 ages are 1--2 orders of magnitude older than either TL or cosmogenic He-3 and appear to have insufficient precision to constrain the ages of chronostratigraphic units within polycyclic volcanoes. In contrast, preliminary data indicate the TL and cosmogenic He-3 dating methods have the ability to resolve the late Quaternary volcanic stratigraphy, and results from these dating methods are consistent with the degree of soil development and geomorphic modification of the volcanic units. K-Ar and Ar-40/Ar-39 dates from these small basaltic volcanic centers have been used to calibrate new Quaternary dating methods, e.g. rock varnish, which in turn have been used to interpret landscape evolution in the SW US.

  13. Secondary hardening steel having improved combination of hardness and toughness

    DOEpatents

    Parker, Earl R.; Zackay, Victor F.; Bhat, Manjeshwar S.; Garrison, Jr., Warren M.

    1979-01-01

    A secondary hardening alloy steel composition consisting essentially of about 0.25-0.5% carbon, about 0.5-1.0% manganese, about 1.5-3.0% nickel, about 0-1.0% chromium, about 1.75-2.5% molybdenum, about 0-0.4% vanadium, and an additive selected from about 1-3% aluminum and a combination of at least about 1% aluminum and at least about 1% silicon for a combined Al+Si content of about 2-4%, the balance being iron and impurity elements. The present steel composition has the following characteristics: it exhibits a flat tempering response, it is hardenable upon tempering to a Rockwell C hardness of at least 50, and it has an improved combination of hardness vs. toughness properties after tempering in the secondary hardening range. A method of preparation is also described.

  14. Crack resistance of tungsten hardened by dispersed refractory oxides

    SciTech Connect

    Babak, A.V.; Uskov, E.I.

    1985-05-01

    The authors present the results of an investigation of the crack resistance in a wide temperature range of the production types of tungsten VMP-S (conditionally designated technical purity tungsten with a higher degree of deformation than type VMP tungsten), VMP-3 (hardened with refractory oxides), and VMP-4 (with the addition of copper and hardened with refractory oxides) produced using the same method. It is reported that hardening of technical purity tungsten with refractory oxides increases the resistance of the material to crack development in the 20-2000C range, but the upper boundary of the temperature area of the ductile-to-brittle transition is shifted in the direction of higher temperatures, which must be taken into consideration in the use of the investigated alloys as structural materials for objects of new technology.

  15. Oxide dispersion hardened mechanically alloyed materials for high temperatures

    NASA Technical Reports Server (NTRS)

    Benjamin, J. S.; Strassburg, F. W.

    1982-01-01

    The procedure of mechanical alloying makes it possible to obtain, with the aid of powder-metallurgy techniques, alloys that consist of a metallic matrix in which very fine oxide particles are dispersed. Mechanically alloyed compound powders can be used for making either forged or hot-rolled semifinished products. For these products, dispersion strengthening and precipitation hardening has been combined. At high temperatures, the strength characteristics of the alloy are determined by both dispersion hardening and by precipitation hardening processes. The effect produced by each process is independent of that due to the other. Attention is given to the principle of mechanical alloying developed by Benjamin (1970, 1976), the strength characteristics of mechanically alloyed materials, the corrosion resistance of mechanically alloyed material at high temperatures, and the preparation and characteristics of the alloy MA 6000 E.

  16. Engineering design guidelines for electromagnetic pulse hardening of naval equipment

    NASA Astrophysics Data System (ADS)

    Rogers, S. R.; Perala, R. A.; Rosich, R. K.; Cook, R. B.; Rudolph, T. H.

    1981-07-01

    This document is intended to be used by engineers who design and manufacture shipboard equipment. It is complete in the sense that both the EMP hazard and the means of mitigating the hazard (hardening) are presented. The hazard is described, which not only discusses EMP generation in a general sense, but it also presents specific threat levels for EMP fields and transient currents and voltages included on cables and antennas which are connected to electronic equipment. This specific threat constitutes an EMP survivability criteria which must be met by the mission critical equipment. The necessary hardening technology areas include volume shielding, cable shielding and connectors, interface susceptibility analysis, terminal protective devices, upset and upset hardening, common mode rejection techniques, optical isolation, and grounding/bonding techniques. Test techniques which can verify equipment hardness are presented along with methods to observe the equipment's hardness and maintain the hardness.

  17. Coevolution of volcanic catchments in Japan

    NASA Astrophysics Data System (ADS)

    Yoshida, Takeo; Troch, Peter A.

    2016-03-01

    Present-day landscapes have evolved over time through interactions between the prevailing climates and geological settings. Understanding the linkage between spatial patterns of landforms, soils, and vegetation in landscapes and their hydrological response is critical to make quantitative predictions in ungaged basins. Catchment coevolution is a theoretical framework that seeks to formulate hypotheses about the mechanisms and conditions that determine the historical development of catchments and how such evolution affects their hydrological response. In this study, we selected 14 volcanic catchments of different ages (from 0.225 to 82.2 Ma) in Japan. We derived indices of landscape properties (drainage density and slope-area relationship) as well as hydrological response (annual water balance, baseflow index, and flow-duration curves) and examined their relation with catchment age and climate (through the aridity index). We found a significant correlation between drainage density and baseflow index with age, but not with climate. The intra-annual flow variability was also significantly related to catchments age. Younger catchments tended to have lower peak flows and higher low flows, while older catchments exhibited more flashy runoff. The decrease in baseflow with catchment age is consistent with the existing hypothesis that in volcanic landscapes the major flow pathways change over time from deep groundwater flow to shallow subsurface flow. The drainage density of our catchments decreased with age, contrary to previous findings in a set of similar, but younger volcanic catchments in the Oregon Cascades, in which drainage density increased with age. In that case, older catchments were thought to show more landscape incision due to increasing near-surface lateral flow paths. Our results suggests two competing hypotheses on the evolution of drainage density in mature catchments. One is that as catchments continue to age, the hydrologically active channels retreat

  18. Cenozoic volcanic rocks of Saudi Arabia

    USGS Publications Warehouse

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

    2016-01-01

    The historical record of volcanic activity in Saudi Arabia suggests that volcanism is dormant. The harrats should be evaluated for their potential as volcanic hazards and as sources of geothermal energy. The volcanic rocks are natural traps for groundwater; thus water resources for agriculture may be significant and should be investigated.

  19. Felsic Volcanics on the Moon

    NASA Astrophysics Data System (ADS)

    Jolliff, B. L.; Clegg-Watkins, R. N.; Zanetti, M. R.; Lawrence, S. J.; Stopar, J. D.; Shirley, K. A.; Glitch, T. D.; Greenhagen, B. T.

    2016-05-01

    LRO data sets have been used to characterize sites of red-spot volcanism on the Moon, confirming that they are composed of silica-rich materials and establishing key morphometric parameters including shape, slopes, boulder contents, and photometry.

  20. Volcanology: Volcanic bipolar disorder explained

    NASA Astrophysics Data System (ADS)

    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.

  1. Lidar sounding of volcanic plumes

    NASA Astrophysics Data System (ADS)

    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.

  2. Hardenability of austenite in a dual-phase steel

    SciTech Connect

    Sarwar, M.; Priestner, R.

    1999-06-01

    A low-carbon, low-alloy steel was intercritically heat treated and thermomechanically processed to study the martensitic hardenability of austenite present. Rolling of the two-phase ({alpha} + {gamma}) microstructure elongated austenite particles and reduced their martensitic hardenability because the {alpha}/{gamma} interface where new ferrite forms during cooling was increased by the particle elongation. The martensite particles obtained in rolled material were also elongated or fibered in the rolling direction. Therefore, the thermomechanical processing of a two-phase ({alpha} + {gamma}) mixture has the detrimental effect of increasing the quenching power needed to yield a specific amount of martensite.

  3. Temperature influence on water transport in hardened cement pastes

    SciTech Connect

    Drouet, Emeline; Poyet, Stéphane; Torrenti, Jean-Michel

    2015-10-15

    Describing water transport in concrete is an important issue for the durability assessment of radioactive waste management reinforced concrete structures. Due to the waste thermal output such structures would be submitted to moderate temperatures (up to 80 °C). We have then studied the influence of temperature on water transport within hardened cement pastes of four different formulations. Using a simplified approach (describing only the permeation of liquid water) we characterized the properties needed to describe water transport (up to 80 °C) using dedicated experiments. For each hardened cement paste the results are presented and discussed.

  4. Statistical thermodynamics of strain hardening in polycrystalline solids

    SciTech Connect

    Langer, James S.

    2015-09-18

    This paper starts with a systematic rederivation of the statistical thermodynamic equations of motion for dislocation-mediated plasticity proposed in 2010 by Langer, Bouchbinder, and Lookman. The paper then uses that theory to explain the anomalous rate-hardening behavior reported in 1988 by Follansbee and Kocks and to explore the relation between hardening rate and grain size reported in 1995 by Meyers et al. A central theme is the need for physics-based, nonequilibrium analyses in developing predictive theories of the strength of polycrystalline materials.

  5. Impact of Scaled Technology on Radiation Testing and Hardening

    NASA Technical Reports Server (NTRS)

    LaBel, Kenneth A.; Cohn, Lewis M.

    2005-01-01

    This presentation gives a brief overview of some of the radiation challenges facing emerging scaled digital technologies with implications on using consumer grade electronics and next generation hardening schemes. Commercial semiconductor manufacturers are recognizing some of these issues as issues for terrestrial performance. Looking at means of dealing with soft errors. The thinned oxide has indicated improved TID tolerance of commercial products hardened by "serendipity" which does not guarantee hardness or say if the trend will continue. This presentation also focuses one reliability implications of thinned oxides.

  6. Statistical thermodynamics of strain hardening in polycrystalline solids

    SciTech Connect

    Langer, James S.

    2015-01-01

    This paper starts with a systematic rederivation of the statistical thermodynamic equations of motion for dislocation-mediated plasticity proposed in 2010 by Langer, Bouchbinder, and Lookman. The paper then uses that theory to explain the anomalous rate-hardening behavior reported in 1988 by Follansbee and Kocks and to explore the relation between hardening rate and grain size reported in 1995 by Meyers et al. A central theme is the need for physics-based, nonequilibrium analyses in developing predictive theories of the strength of polycrystalline materials.

  7. Method and apparatus for welding precipitation hardenable materials

    DOEpatents

    Murray, Jr., Holt; Harris, Ian D.; Ratka, John O.; Spiegelberg, William D.

    1994-01-01

    A method for welding together members consisting of precipitation age hardened materials includes the steps of selecting a weld filler material that has substantially the same composition as the materials being joined, and an age hardening characteristic temperature age threshold below that of the aging kinetic temperature range of the materials being joined, whereby after welding the members together, the resulting weld and heat affected zone (HAZ) are heat treated at a temperature below that of the kinetic temperature range of the materials joined, for obtaining substantially the same mechanical characteristics for the weld and HAZ, as for the parent material of the members joined.

  8. Method and apparatus for welding precipitation hardenable materials

    DOEpatents

    Murray, H. Jr.; Harris, I.D.; Ratka, J.O.; Spiegelberg, W.D.

    1994-06-28

    A method for welding together members consisting of precipitation age hardened materials includes the steps of selecting a weld filler material that has substantially the same composition as the materials being joined, and an age hardening characteristic temperature age threshold below that of the aging kinetic temperature range of the materials being joined, whereby after welding the members together, the resulting weld and heat affected zone (HAZ) are heat treated at a temperature below that of the kinetic temperature range of the materials joined, for obtaining substantially the same mechanical characteristics for the weld and HAZ, as for the parent material of the members joined. 5 figures.

  9. Laser hardening techniques on steam turbine blade and application

    NASA Astrophysics Data System (ADS)

    Yao, Jianhua; Zhang, Qunli; Kong, Fanzhi; Ding, Qingming

    Different laser surface hardening techniques, such as laser alloying and laser solution strengthening were adopted to perform modification treatment on the local region of inset edge for 2Cr13 and 17-4PH steam turbine blades to prolong the life of the blades. The microstructures, microhardness and anti-cavitation properties were investigated on the blades after laser treatment. The hardening mechanism and technique adaptability were researched. Large scale installation practices confirmed that the laser surface modification techniques are safe and reliable, which can improve the properties of blades greatly with advantages of high automation, high quality, little distortion and simple procedure.

  10. Why semiconductors must be hardened when used in space

    SciTech Connect

    Winokur, P. S.

    2000-01-04

    The natural space radiation environment presents a great challenge to present and future satellite systems with significant assets in space. Defining requirements for such systems demands knowledge about the space radiation environment and its effects on electronics and optoelectronics technologies, as well as suitable risk assessment of the uncertainties involved. For mission of high radiation levels, radiation-hardened integrated circuits will be required to preform critical mission functions. The most successful systems in space will be those that are best able to blend standard commercial electronics with custom radiation-hardened electronics in a mix that is suitable for the system of interest.

  11. Statistical thermodynamics of strain hardening in polycrystalline solids

    NASA Astrophysics Data System (ADS)

    Langer, J. S.

    2015-09-01

    This paper starts with a systematic rederivation of the statistical thermodynamic equations of motion for dislocation-mediated plasticity proposed in 2010 by Langer, Bouchbinder, and Lookman [Acta Mat. 58, 3718 (2010), 10.1016/j.actamat.2010.03.009]. It then uses that theory to explain the anomalous rate-hardening behavior reported in 1988 by Follansbee and Kocks and to explore the relation between hardening rate and grain size reported in 1995 by Meyers et al. A central theme is the need for physics-based, nonequilibrium analyses in developing predictive theories of the strength of polycrystalline materials.

  12. Modelling work hardening of aluminium alloys containing dispersoids

    NASA Astrophysics Data System (ADS)

    Zhao, Qinglong; Holmedal, Bjørn

    2013-08-01

    The influence of dispersoids on tensile deformation behaviour has been studied by comparison of aluminium alloys containing different dispersoid densities. It was found that a fine dispersion of non-shearable particles led to an increased work hardening at the initial plastic deformation, but the effect was opposite at higher strains. The reason has been attributed to the generation of geometrically necessary dislocations (GNDs). A new model has been proposed for the evolution of GNDs based on a balance of storage and dynamic recovery of GNDs. The model predicts a rapid saturation of GNDs and a reduced work hardening at small strains, consistent with the experimental results.

  13. On the hardening and softening of nanocrystalline materials

    SciTech Connect

    Fougere, G.E.; Weertman, J.R. . Dept. of Materials Science and Engineering); Siegel, R.W. . Materials Science Div.)

    1993-04-01

    Nanocrystalline Pd and Cu samples have been thermally treated to determine whether the relation between hardness and grain size depend on the method used to vary the grain sizes. Previous reports indicate that hardening with decreasing grain size resulted from data obtained using individual samples, while softening with decreasing grain size resulted from data from a given sample that had been thermally treated. Hardening and softening regimes were evident for the nanocrystalline cu, and the hardness improvements over the original as-consolidated state were maintained throughout the thermal treatments. This review examines our hardness results for Cu and Pd and those for other nanocrystalline materials.

  14. Monogenetic volcanic hazards and assessment

    NASA Astrophysics Data System (ADS)

    Connor, C.; Connor, L. J.; Richardson, J. A.

    2012-12-01

    Many of the Earth's major cities are build on the products of monogenetic volcanic eruptions and within geologically active basaltic volcanic fields. These cities include Mexico City (Mexico), Auckland (New Zealand), Melbourne (Australia), and Portland (USA) to name a few. Volcanic hazards in these areas are complex, and involve the potential formation of new volcanic vents and associated hazards, such as lava flows, tephra fallout, and ballistic hazards. Hazard assessment is complicated by the low recurrence rate of volcanism in most volcanic fields. We have developed a two-stage process for probabilistic modeling monogenetic volcanic hazards. The first step is an estimation of the possible locations of future eruptive vents based on kernel density estimation and recurrence rate of volcanism using Monte Carlo simulation and accounting for uncertainties in age determinations. The second step is convolution of this spatial density / recurrence rate model with hazard codes for modeling lava inundation, tephra fallout, and ballistic impacts. A methodology is presented using this two-stage approach to estimate lava flow hazard in several monogenetic volcanic fields, including at a nuclear power plant site near the Shamiram Plateau, a Quaternary volcanic field in Armenia. The location of possible future vents is determined by estimating spatial density from a distribution of 18 mapped vents using a 2-D elliptical Gaussian kernel function. The SAMSE method, a modified asymptotic mean squared error approach, uses the distribution of known eruptive vents to optimally determine a smoothing bandwidth for the Gaussian kernel function. The result is a probability map of vent density. A large random sample (N=10000) of vent locations is drawn from this probability map. For each randomly sampled vent location, a lava flow inundation model is executed. Lava flow input parameters (volume and average thickness) are determined from distributions fit to field observations of the low

  15. Volcanic hazards and aviation safety

    USGS Publications Warehouse

    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.

  16. Bioindication of volcanic mercury (Hg) deposition around Mt Etna (Sicily)

    NASA Astrophysics Data System (ADS)

    Martin, R.; Witt, M. L.; Sawyer, G. M.; Watt, S.; Bagnato, E.; Calabrese, S.; Aiuppa, A.; Delmelle, P.; Pyle, D. M.; Mather, T. A.

    2012-12-01

    Mt. Etna is a major natural source of Hg to the Mediterranean region. Total mercury concentrations, [Hg]tot, in Castanea sativa (sweet chestnut) leaves sampled 7-13 km from Etna's vents (during six campaigns in 2005-2011) were determined using atomic absorption spectroscopy. [Hg]tot in C. sativa was greatest on Etna's SE flank reflecting Hg deposition from the typically overhead volcanic plume. When adjusted for leaf age, [Hg]tot in C. sativa also increased with recent eruptive activity. [Hg]tot in C. sativa was not controlled by [Hg]tot in soils, which instead was greatest on the (upwind) NW flank and correlated strongly with soil organic matter (% Org). Our results suggest that at least ~1% of Hg emitted from Etna is deposited proximally, supporting recent measurement and model results which indicate that GEM (Hg0; the dominant form of Hg in high temperature magmatic gases) is oxidised rapidly to RGM and Hgp in ambient temperature volcanic plumes. Samples of C. sativa and soils were also collected in July and September 2012 alongside SO2 and acid gas diffusion tube samples. These new samples will enable us to investigate Hg accumulation over a single growth season with reference to the exposure of vegetation to volcanic gases and particles.

  17. Pulmonary toxicity of Mount St. Helens volcanic ash

    SciTech Connect

    Sanders, C.L.; Conklin, A.W.; Gelman, R.A.; Adee, R.R.; Rhoads, K.

    1982-02-01

    The effects of Mount St. Helens volcanic ash, a sandy loam soil, and quartz particles on the lung and mediastinal lymph nodes of Fischer rats were studied at time intervals of up to 109 days after in tratracheal instillation of 40 mg ash, soil, or quartz in a single dose or after multiple doses of ash instilled in seven consecutive weekly doses for a total deposition of 77 mg. Quartz caused early granuloma formation, later fibrosis was also seen in lymph nodes. Volcanic ash caused an ill-defined inflammatory reaction with a few rats showing granuloma formulation, a very limited linear fibrosis, and a moderate lipoproteinosis, and lymph nodes were enlarged with numerous microgranulomas but without reticulin and collagen formation. Pulmonary reactions to soil particles were less intense but similar to those in ash- exposed animals; lymph nodes were not enlarged. No significant clearance of ash was found at 3 months after instillation. Volcanic ash produced a simple pneumoconiosis similar to what has been described for animals and humans living for prolonged periods of time in dusty desert areas of the United States.

  18. Are Axial Volcanic Ridges where all the (volcanic) action is?

    NASA Astrophysics Data System (ADS)

    Searle, R. C.

    2012-12-01

    Although axial volcanic ridges (AVRs) are generally recognised as the main loci for lithospheric generation at slow-spreading mid-ocean ridges, various recent studies have suggested that axial volcanism is not confined to them. Here I present evidence from three studies for significant amounts of off-AVR volcanism at three slow-spreading ridges. 1) Near-bottom side-scan sonar (TOBI) images of the Mid-Atlantic Ridge near 13°N show a complex pattern of closely-spaced, active oceanic core complexes (OCCs) where plate separation is largely a-volcanic, separated by short segments of vigorous volcanic spreading. In one such volcanic segment, the brightest sea floor and therefore inferred youngest volcanism occurs not on the topographic axis (an apparently 'old' AVR) but at the edge of a broad axial valley. 2) A similar TOBI survey of the Mid-Cayman Spreading Centre reveals AVRs in the north and south flanking an OCC (Mt. Dent) and a non-volcanic ridge interpreted as tectonically extruded peridotite ('smooth' sea floor). In both AVR segments there are clear, young lava flows that have erupted from perched sources part way up the median valley walls and have partly flowed down into the valley. 3) The third case is from the Mid-Atlantic Ridge at 45°N, where we conducted a detailed geophysical and geological study of an AVR and surrounding median valley floor. The AVR is largely surrounded by flat sea floor composed mainly of lobate and sheet flows, whereas the AVR comprises predominantly pillow lavas. Although we have no firm dates, various indicators suggest most lavas on the AVR are around 10ka old or somewhat less. The apparently youngest (brightest acoustic returns, thinnest sediment cover) of the flat-lying lava flows appears to have a similar age from its degree of sediment cover. Contact relations between these lavas and the AVR flanks show no evidence of a clear age difference between the two, and we think both types of eruption may have occurred roughly

  19. Volcanic Surface Textures

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 16 June 2003

    The platy surface texture observed in this THEMIS image of the vast plains southeast of the volcano Elysium Mons likely formed by very fluid cooling lava. Variations in the surface texture may reflect different cooling or flow rates of the lava. The lack of any large impact craters also points to a relatively young age for these volcanic materials. The two largest impact craters occur in the higher plateau unit indicating that these materials are older.

    Image information: VIS instrument. Latitude 11.6, Longitude 182.4 East (177.6 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  20. A radiation-hardened 16/32-bit microprocessor

    SciTech Connect

    Hass, K.J.; Treece, R.K.; Giddings, A.E.

    1989-01-01

    A radiation-hardened 16/32-bit microprocessor has been fabricated and tested. Our initial evaluation has demonstrated that it is functional after a total gamma dose of 5Mrad(Si) and is immune to SEU from Krypton ions. 3 refs., 2 figs.

  1. 49. INTERIOR VIEW OF HARDENER AREA SHOWING GAUGE THAT MEASURES ...

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

    49. INTERIOR VIEW OF HARDENER AREA SHOWING GAUGE THAT MEASURES HARDNESS, THE NAIL MUST BREAK IN THE CENTER RANGE OF THE CURVED BAR TO HAVE THE CORRECT HARDNESS (THE NAIL WILL BREAK TOO EASILY IF TOO HARD AND WILL BEND TOO MUCH IF TOO SOFT) - LaBelle Iron Works, Thirtieth & Wood Streets, Wheeling, Ohio County, WV

  2. Iterative Beam Hardening Correction for Multi-Material Objects

    PubMed Central

    Zhao, Yunsong; Li, Mengfei

    2015-01-01

    In this paper, we propose an iterative beam hardening correction method that is applicable for the case with multiple materials. By assuming that the materials composing scanned object are known and that they are distinguishable by their linear attenuation coefficients at some given energy, the beam hardening correction problem is converted into a nonlinear system problem, which is then solved iteratively. The reconstructed image is the distribution of linear attenuation coefficient of the scanned object at a given energy. So there are no beam hardening artifacts in the image theoretically. The proposed iterative scheme combines an accurate polychromatic forward projection with a linearized backprojection. Both forward projection and backprojection have high degree of parallelism, and are suitable for acceleration on parallel systems. Numerical experiments with both simulated data and real data verifies the validity of the proposed method. The beam hardening artifacts are alleviated effectively. In addition, the proposed method has a good tolerance on the error of the estimated x-ray spectrum. PMID:26659554

  3. Iterative Beam Hardening Correction for Multi-Material Objects.

    PubMed

    Zhao, Yunsong; Li, Mengfei

    2015-01-01

    In this paper, we propose an iterative beam hardening correction method that is applicable for the case with multiple materials. By assuming that the materials composing scanned object are known and that they are distinguishable by their linear attenuation coefficients at some given energy, the beam hardening correction problem is converted into a nonlinear system problem, which is then solved iteratively. The reconstructed image is the distribution of linear attenuation coefficient of the scanned object at a given energy. So there are no beam hardening artifacts in the image theoretically. The proposed iterative scheme combines an accurate polychromatic forward projection with a linearized backprojection. Both forward projection and backprojection have high degree of parallelism, and are suitable for acceleration on parallel systems. Numerical experiments with both simulated data and real data verifies the validity of the proposed method. The beam hardening artifacts are alleviated effectively. In addition, the proposed method has a good tolerance on the error of the estimated x-ray spectrum. PMID:26659554

  4. An SEU-hardened CMOS data latch design

    SciTech Connect

    Rockett, L.R. Jr.

    1988-12-01

    A Single Event Upset (SEU)-hardened Complementary Metal-Oxide Semiconductor (CMOS) data latch design is described. The hardness is achieved by virtue of the latch design, thus no fabrication process or design groundrule development is required. Hardness is gained with comparatively little adverse impact on performance. Cyclotron tests provided hardness verification.

  5. SEU-hardened storage cell validation using a pulsed laser

    SciTech Connect

    Velazco, R.

    1996-12-01

    Laser tests performed on a prototype chip to validate new SEU-hardened storage cell designs revealed unexpected latch-up and single-event upset phenomena. The investigations that identified their location show the existence of a topology-dependent dual node upset mechanism. Design solutions are suggested to avoid its occurrence.

  6. Overcoming scaling concerns in a radiation-hardening CMOS technology

    SciTech Connect

    Maimon, J.; Haddad, N.

    1999-12-01

    Scaling efforts to develop an advanced radiation-hardened CMOS process to support a 4M SRAM are described. Issues encountered during scaling of transistor, isolation, and resistor elements are discussed, as well as the solutions used to overcome these issues. Transistor data, total dose radiation results, and the performance of novel resistors for prevention of single event upsets (SEU) are presented.

  7. Hardening digital systems with distributed functionality: robust networks

    NASA Astrophysics Data System (ADS)

    Vaskova, Anna; Portela-Garcia, Marta; Garcia-Valderas, Mario; López-Ongil, Celia; Portilla, Jorge; Valverde, Juan; de la Torre, Eduardo; Riesgo, Teresa

    2013-05-01

    Collaborative hardening and hardware redundancy are nowadays the most interesting solutions in terms of fault tolerance achieved and low extra cost imposed to the project budget. Thanks to the powerful and cheap digital devices that are available in the market, extra processing capabilities can be used for redundant tasks, not only in early data processing (sensed data) but also in routing and interfacing1

  8. Beam hardening correction for sparse-view CT reconstruction

    NASA Astrophysics Data System (ADS)

    Liu, Wenlei; Rong, Junyan; Gao, Peng; Liao, Qimei; Lu, HongBing

    2015-03-01

    Beam hardening, which is caused by spectrum polychromatism of the X-ray beam, may result in various artifacts in the reconstructed image and degrade image quality. The artifacts would be further aggravated for the sparse-view reconstruction due to insufficient sampling data. Considering the advantages of the total-variation (TV) minimization in CT reconstruction with sparse-view data, in this paper, we propose a beam hardening correction method for sparse-view CT reconstruction based on Brabant's modeling. In this correction model for beam hardening, the attenuation coefficient of each voxel at the effective energy is modeled and estimated linearly, and can be applied in an iterative framework, such as simultaneous algebraic reconstruction technique (SART). By integrating the correction model into the forward projector of the algebraic reconstruction technique (ART), the TV minimization can recover images when only a limited number of projections are available. The proposed method does not need prior information about the beam spectrum. Preliminary validation using Monte Carlo simulations indicates that the proposed method can provide better reconstructed images from sparse-view projection data, with effective suppression of artifacts caused by beam hardening. With appropriate modeling of other degrading effects such as photon scattering, the proposed framework may provide a new way for low-dose CT imaging.

  9. Review of radiation hardening techniques for EDFAs in space environment

    NASA Astrophysics Data System (ADS)

    Wang, Qian; Tian, CuiPing; Wang, YingYing; Wang, Pu

    2015-03-01

    The damage mechanism and test technology of space radiation environment to space equipment was classified and the radiation protection demand of active fiber for space application was analyzed. The radiation hardening techniques of Ce doping, hydrogen loading and pre-radiation exposure and thermal annealing for Er:Yb co-doped fiber was surveyed.

  10. Total dose performance of radiation hardened voltage regulators and references

    NASA Technical Reports Server (NTRS)

    McClure, S.; Gorelick, J.; Pease, R.; Rax, B.; Ladbury, R.

    2001-01-01

    Total dose test of commercially available radiation hardened bipolar voltage regulators and references show reduced sensitivity to dose rate and varying sensitivity to bias under pressure. Behavior of critical parameters in different dose rate and bias conditions is compared and the impact to hardness assurance methodology is discussed.

  11. SEGR response of a radiation-hardened power MOSFET technology

    SciTech Connect

    Wheatley, C.F.; Titus, J.L.; Burton, D.I.; Carley, D.R.

    1996-12-01

    SEGR response curves are presented for eighteen different device types of radiation-hardened power MOSFETs. Comparisons are made to demonstrate the technology`s insensitivity to die size, rated blocking voltage, channel conductivity, and temperature. From this data, SEGR cross-sectional area curves are inferred.

  12. Aurorae and Volcanic Eruptions

    NASA Astrophysics Data System (ADS)

    2001-06-01

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

  13. Nanoscale characterization of the biomechanical hardening of bovine zona pellucida.

    PubMed

    Boccaccio, Antonio; Frassanito, Maria Cristina; Lamberti, Luciano; Brunelli, Roberto; Maulucci, Giuseppe; Monaci, Maurizio; Papi, Massimiliano; Pappalettere, Carmine; Parasassi, Tiziana; Sylla, Lakamy; Ursini, Fulvio; De Spirito, Marco

    2012-11-01

    The zona pellucida (ZP) is an extracellular membrane surrounding mammalian oocytes. The so-called zona hardening plays a key role in fertilization process, as it blocks polyspermy, which may also be caused by an increase in the mechanical stiffness of the ZP membrane. However, structural reorganization mechanisms leading to ZP's biomechanical hardening are not fully understood yet. Furthermore, a correct estimate of the elastic properties of the ZP is still lacking. Therefore, the aim of the present study was to investigate the biomechanical behaviour of ZP membranes extracted from mature and fertilized bovine oocytes to better understand the mechanisms involved in the structural reorganization of the ZP that may lead to the biomechanical hardening of the ZP. For that purpose, a hybrid procedure is developed by combining atomic force microscopy nanoindentation measurements, nonlinear finite element analysis and nonlinear optimization. The proposed approach allows us to determine the biomechanical properties of the ZP more realistically than the classical analysis based on Hertz's contact theory, as it accounts for the nonlinearity of finite indentation process, hyperelastic behaviour and material heterogeneity. Experimental results show the presence of significant biomechanical hardening induced by the fertilization process. By comparing various hyperelastic constitutive models, it is found that the Arruda-Boyce eight-chain model best describes the biomechanical response of the ZP. Fertilization leads to an increase in the degree of heterogeneity of membrane elastic properties. The Young modulus changes sharply within a superficial layer whose thickness is related to the characteristic distance between cross-links in the ZP filamentous network. These findings support the hypothesis that biomechanical hardening of bovine ZP is caused by an increase in the number of inter-filaments cross-links whose density should be higher in the ZP inner side. PMID:22675161

  14. Forming an age hardenable aluminum alloy with intermediate annealing

    NASA Astrophysics Data System (ADS)

    Wang, Kaifeng; Carsley, John E.; Stoughton, Thomas B.; Li, Jingjing; Zhang, Lianhong; He, Baiyan

    2013-12-01

    A method to improve formability of aluminum sheet alloys by a two-stage stamping process with intermediate annealing was developed for a non-age hardenable Al-Mg alloy where the annealing heat treatment provided recovery of cold work from the initial stamping and recrystallization of the microstructure to enhance the forming limits of the material. This method was extended to an age hardenable, Al-Mg-Si alloy, which is complicated by the competing metallurgical effects during heat treatment including recovery (softening effect) vs. precipitation (hardening effect). An annealing heat treatment process condition was discovered wherein the stored strain energy from an initial plastic deformation can be sufficiently recovered to enhance formability in a second deformation; however, there is a deleterious effect on subsequent precipitation hardening. The improvement in formability was quantified with uniaxial tensile tests as well as with the forming limit diagram. Since strain-based forming limit curves (FLC) are sensitive to pre-strain history, both stress-based FLCs and polar-effective-plastic-strain (PEPS) FLCs, which are path-independent, were used to evaluate the forming limits after preform annealing. A technique was developed to calculate the stress-based FLC in which a residual-effective-plastic-strain (REPS) was determined by overlapping the hardening curve of the pre-strained and annealed material with that of the simply-annealed- material. After converting the strain-based FLCs using the constant REPS method, it was found that the stress-based FLCs and the PEPS FLCs of the post-annealed materials were quite similar and both tools are applicable for evaluating the forming limits of Al-Mg-Si alloys for a two-step stamping process with intermediate annealing.

  15. On water in volcanic clouds

    NASA Astrophysics Data System (ADS)

    Durant, Adam J.

    2007-12-01

    Volcanic clouds and tephra fallout present a hazard to aviation, human and animal health (direct inhalation or ingestion, contamination of water supplies), and infrastructure (building collapse, burial of roads and railways, agriculture, abrasive and chemical effects on machinery). Understanding sedimentation processes is a fundamental component in the prediction of volcanic cloud lifetime and fallout at the ground, essential in the mitigation of these hazards. The majority of classical volcanic ash transport and dispersion models (VATDM) are based solely on fluid dynamics. The non-agreement between VATDM and observed regional-scale tephra deposit characteristics is especially obvious at large distances from the source volcano. In meteorology, the processes of hydrometeor nucleation, growth and collection have been long-established as playing a central role in sedimentation and precipitation. Taking this as motivation, the hypothesis that hydrometeor formation drives sedimentation from volcanic clouds was tested. The research objectives of this dissertation are: (1) To determine the effectiveness of tephra particles in the catalysis of the liquid water to ice phase transformation, with application to ice hydrometeor formation in volcanic clouds. (2) To determine the sedimentological characteristics of distal (100s km) tephra fallout from recent volcanic clouds. (3) To assess particle fallout rates from recent volcanic clouds in the context of observed deposit characteristics. (4) To assess the implications of hydrometeor formation on the enhancement of volcanic sedimentation and the potential for cloud destabilization from volcanic hydrometeor sublimation. Dissertation Overview. The following chapters present the analysis, results and conclusions of heterogeneous ice nucleation experiments and sedimentological characterization of several recent tephra deposits. The dissertation is organized in three chapters, each prepared in journal article format. In Chapter 1

  16. Climatic impact of volcanic eruptions

    NASA Technical Reports Server (NTRS)

    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.

  17. Atmospheric chemistry in volcanic plumes.

    PubMed

    von Glasow, Roland

    2010-04-13

    Recent field observations have shown that the atmospheric plumes of quiescently degassing volcanoes are chemically very active, pointing to the role of chemical cycles involving halogen species and heterogeneous reactions on aerosol particles that have previously been unexplored for this type of volcanic plumes. Key features of these measurements can be reproduced by numerical models such as the one employed in this study. The model shows sustained high levels of reactive bromine in the plume, leading to extensive ozone destruction, that, depending on plume dispersal, can be maintained for several days. The very high concentrations of sulfur dioxide in the volcanic plume reduces the lifetime of the OH radical drastically, so that it is virtually absent in the volcanic plume. This would imply an increased lifetime of methane in volcanic plumes, unless reactive chlorine chemistry in the plume is strong enough to offset the lack of OH chemistry. A further effect of bromine chemistry in addition to ozone destruction shown by the model studies presented here, is the oxidation of mercury. This relates to mercury that has been coemitted with bromine from the volcano but also to background atmospheric mercury. The rapid oxidation of mercury implies a drastically reduced atmospheric lifetime of mercury so that the contribution of volcanic mercury to the atmospheric background might be less than previously thought. However, the implications, especially health and environmental effects due to deposition, might be substantial and warrant further studies, especially field measurements to test this hypothesis. PMID:20368458

  18. Atmospheric chemistry in volcanic plumes

    PubMed Central

    von Glasow, Roland

    2010-01-01

    Recent field observations have shown that the atmospheric plumes of quiescently degassing volcanoes are chemically very active, pointing to the role of chemical cycles involving halogen species and heterogeneous reactions on aerosol particles that have previously been unexplored for this type of volcanic plumes. Key features of these measurements can be reproduced by numerical models such as the one employed in this study. The model shows sustained high levels of reactive bromine in the plume, leading to extensive ozone destruction, that, depending on plume dispersal, can be maintained for several days. The very high concentrations of sulfur dioxide in the volcanic plume reduces the lifetime of the OH radical drastically, so that it is virtually absent in the volcanic plume. This would imply an increased lifetime of methane in volcanic plumes, unless reactive chlorine chemistry in the plume is strong enough to offset the lack of OH chemistry. A further effect of bromine chemistry in addition to ozone destruction shown by the model studies presented here, is the oxidation of mercury. This relates to mercury that has been coemitted with bromine from the volcano but also to background atmospheric mercury. The rapid oxidation of mercury implies a drastically reduced atmospheric lifetime of mercury so that the contribution of volcanic mercury to the atmospheric background might be less than previously thought. However, the implications, especially health and environmental effects due to deposition, might be substantial and warrant further studies, especially field measurements to test this hypothesis. PMID:20368458

  19. Bacterial diversity of weathered terrestrial Icelandic volcanic glasses.

    PubMed

    Kelly, Laura C; Cockell, Charles S; Piceno, Yvette M; Andersen, Gary L; Thorsteinsson, Thorsteinn; Marteinsson, Viggo

    2010-11-01

    The diversity of microbial communities inhabiting two terrestrial volcanic glasses of contrasting mineralogy and age was characterised. Basaltic glass from a <0.8 Ma hyaloclastite deposit (Valafell) harboured a more diverse Bacteria community than the younger rhyolitic glass from ∼150-300 AD (Dόmadalshraun lava flow). Actinobacteria dominated 16S rRNA gene clone libraries from both sites, however, Proteobacteria, Acidobacteria and Cyanobacteria were also numerically abundant in each. A significant proportion (15-34%) of the sequenced clones displayed <85% sequence similarities with current database sequences, thus suggesting the presence of novel microbial diversity in each volcanic glass. The majority of clone sequences shared the greatest similarity to uncultured organisms, mainly from soil environments, among these clones from Antarctic environments and Hawaiian and Andean volcanic deposits. Additionally, a large number of clones within the Cyanobacteria and Proteobacteria were more similar to sequences from other lithic environments, included among these Icelandic clones from crystalline basalt and rhyolite, however, no similarities to sequences reported from marine volcanic glasses were observed. PhyloChip analysis detected substantially greater numbers of phylotypes at both sites than the corresponding clone libraries, but nonetheless also identified the basaltic glass community as the richer, containing approximately 29% unique phylotypes compared to rhyolitic glass. PMID:20473490

  20. Aurorae and Volcanic Eruptions

    NASA Astrophysics Data System (ADS)

    2001-06-01

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

  1. Volcanic eruption detection with TOMS

    NASA Technical Reports Server (NTRS)

    Krueger, Arlin J.

    1987-01-01

    The Nimbus 7 Total Ozone Mapping Spectrometer (TOMS) is designed for mapping of the atmospheric ozone distribution. Absorption by sulfur dioxide at the same ultraviolet spectral wavelengths makes it possible to observe and resolve the size of volcanic clouds. The sulfur dioxide absorption is discriminated from ozone and water clouds in the data processing by their spectral signatures. Thus, the sulfur dioxide can serve as a tracer which appears in volcanic eruption clouds because it is not present in other clouds. The detection limit with TOMS is close to the theoretical limit due to telemetry signal quantization of 1000 metric tons (5-sigma threshold) within the instrument field of view (50 by 50 km near the nadir). Requirements concerning the use of TOMS in detection of eruptions, geochemical cycles, and volcanic climatic effects are discussed.

  2. Volcanic eruptions and solar activity

    NASA Technical Reports Server (NTRS)

    Stothers, Richard B.

    1989-01-01

    The historical record of large volcanic eruptions from 1500 to 1980 is subjected to detailed time series analysis. In two weak but probably statistically significant periodicities of about 11 and 80 yr, the frequency of volcanic eruptions increases (decreases) slightly around the times of solar minimum (maximum). Time series analysis of the volcanogenic acidities in a deep ice core from Greenland reveals several very long periods ranging from about 80 to about 350 yr which are similar to the very slow solar cycles previously detected in auroral and C-14 records. Solar flares may cause changes in atmospheric circulation patterns that abruptly alter the earth's spin. The resulting jolt probably triggers small earthquakes which affect volcanism.

  3. Models of volcanic eruption hazards

    SciTech Connect

    Wohletz, K.H.

    1992-01-01

    Volcanic eruptions pose an ever present but poorly constrained hazard to life and property for geothermal installations in volcanic areas. Because eruptions occur sporadically and may limit field access, quantitative and systematic field studies of eruptions are difficult to complete. Circumventing this difficulty, laboratory models and numerical simulations are pivotal in building our understanding of eruptions. For example, the results of fuel-coolant interaction experiments show that magma-water interaction controls many eruption styles. Applying these results, increasing numbers of field studies now document and interpret the role of external water eruptions. Similarly, numerical simulations solve the fundamental physics of high-speed fluid flow and give quantitative predictions that elucidate the complexities of pyroclastic flows and surges. A primary goal of these models is to guide geologists in searching for critical field relationships and making their interpretations. Coupled with field work, modeling is beginning to allow more quantitative and predictive volcanic hazard assessments.

  4. Volcanism in southern Guinevere Planitia, Venus: Regional volcanic history and morphology of volcanic domes

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    Guinevere Planitia is a low-lying region located between the highlands of Beta Regio and Eistla Regio. Analyses of Pioneer Venus, Goldstone, and Arecibo radar data suggested that the surface of Guinevere Planitia is dominated by volcanism, primarily in the form of bright, dark, and mottled plains units. Also identified in this region was the Beta-Eistla Deformation Zone, composed of ovoids and discontinuous segments of lineament belts that have been embayed by the surrounding plains. The resolution of Magellan SAR images allows detailed investigations of the volcanic deposits found in the area in order to determine the types of eruptive activity which have occurred and to constrain the regional volcanic history. Analyses of an area of southern Guinevere Planitia between 0-25 deg N and 300-330 deg indicate the presence of a wide variety of volcanic land forms, including large shield volcanoes, widespread plains, lava flow fields, and small domes, cones, and shields as well as coronae and other circular structures that have associated volcanic deposits.

  5. Additional evidence of Mercurian volcanism

    USGS Publications Warehouse

    Trask, N.J.; Strom, R.G.

    1976-01-01

    Evidence concerned with (1) the character and distribution of terrain surrounding fresh basins, (2) albedo, color and temporal differences between a basin rim and smooth plains on its floor, and (3) the stratigraphic relations and local distribution of smooth plains in the hilly and lineated terrain are cited as additional evidence for an internal origin of much of the Mercurian smooth plains. Altough the question of Mercurian volcanism should be kept open, this evidence together with that presented in an earlier paper suggests that volcanism occurred on Mercury early in its history. ?? 1976.

  6. Air Pollution by Hydrothermal Volcanism and Human Pulmonary Function.

    PubMed

    Linhares, Diana; Ventura Garcia, Patrícia; Viveiros, Fátima; Ferreira, Teresa; dos Santos Rodrigues, Armindo

    2015-01-01

    The aim of this study was to assess whether chronic exposure to volcanogenic air pollution by hydrothermal soil diffuse degassing is associated with respiratory defects in humans. This study was carried in the archipelago of the Azores, an area with active volcanism located in the Atlantic Ocean where Eurasian, African, and American lithospheric plates meet. A cross-sectional study was performed on a study group of 146 individuals inhabiting an area where volcanic activity is marked by active fumarolic fields and soil degassing (hydrothermal area) and a reference group of 359 individuals inhabiting an area without these secondary manifestations of volcanism (nonhydrothermal area). Odds ratio (OR) and 95% confidence intervals (CIs) were adjusted for age, gender, fatigue, asthma, and smoking. The OR for restrictive defects and for exacerbation of obstructive defects (COPD) in the hydrothermal area was 4.4 (95% CI 1.78-10.69) and 3.2 (95% CI 1.82-5.58), respectively. Increased prevalence of restrictions and all COPD severity ranks (mild, moderate, and severe) was observed in the population from the hydrothermal area. These findings may assist health officials in advising and keeping up with these populations to prevent and minimize the risk of respiratory diseases. PMID:26301247

  7. Air Pollution by Hydrothermal Volcanism and Human Pulmonary Function

    PubMed Central

    Linhares, Diana; Garcia, Patrícia Ventura; Viveiros, Fátima; Ferreira, Teresa; Rodrigues, Armindo dos Santos

    2015-01-01

    The aim of this study was to assess whether chronic exposure to volcanogenic air pollution by hydrothermal soil diffuse degassing is associated with respiratory defects in humans. This study was carried in the archipelago of the Azores, an area with active volcanism located in the Atlantic Ocean where Eurasian, African, and American lithospheric plates meet. A cross-sectional study was performed on a study group of 146 individuals inhabiting an area where volcanic activity is marked by active fumarolic fields and soil degassing (hydrothermal area) and a reference group of 359 individuals inhabiting an area without these secondary manifestations of volcanism (nonhydrothermal area). Odds ratio (OR) and 95% confidence intervals (CIs) were adjusted for age, gender, fatigue, asthma, and smoking. The OR for restrictive defects and for exacerbation of obstructive defects (COPD) in the hydrothermal area was 4.4 (95% CI 1.78–10.69) and 3.2 (95% CI 1.82–5.58), respectively. Increased prevalence of restrictions and all COPD severity ranks (mild, moderate, and severe) was observed in the population from the hydrothermal area. These findings may assist health officials in advising and keeping up with these populations to prevent and minimize the risk of respiratory diseases. PMID:26301247

  8. Using Volcanic Ash to Remove Dissolved Uranium and Lead

    NASA Technical Reports Server (NTRS)

    McKay, David S.; Cuero, Raul G.

    2009-01-01

    Experiments have shown that significant fractions of uranium, lead, and possibly other toxic and/or radioactive substances can be removed from an aqueous solution by simply exposing the solution, at ambient temperature, to a treatment medium that includes weathered volcanic ash from Pu'u Nene, which is a cinder cone on the Island of Hawaii. Heretofore, this specific volcanic ash has been used for an entirely different purpose: simulating the spectral properties of Martian soil. The treatment medium can consist of the volcanic ash alone or in combination with chitosan, which is a natural polymer that can be produced from seafood waste or easily extracted from fungi, some bacteria, and some algae. The medium is harmless to plants and animals and, because of the abundance and natural origin of its ingredient( s), is inexpensive. The medium can be used in a variety of ways and settings: it can be incorporated into water-filtration systems; placed in contact or mixed with water-containing solids (e.g., soils and sludges); immersed in bodies of water (e.g., reservoirs, lakes, rivers, or wells); or placed in and around nuclear power plants, mines, and farm fields.

  9. Migration of volcanism in the San Francisco volcanic field, Arizona.

    USGS Publications Warehouse

    Tanaka, K.L.; Shoemaker, E.M.; Ulrich, G.E.; Wolfe, E.W.

    1986-01-01

    The remanent magnetization of volcanic rocks has been determined at 650 sites in this volcanic field in the S part of the Colorado plateau. The polarity of remanent magnetization, combined with K/Ar age determinations, spatial and petrographic association, stratigraphic relations and state of preservation of the cinder cones, provides a basis of assignment to a known magnetic polarity epoch of 610 mafic vents and >100 intermediate to silicic flows, flow sequences and vents. Basaltic volcanism migrated NE before Matoyama time (2.48-5.0 m.y.) at a rate of approx 1.2 cm/yr and eastward over the past 2.5 m.y. at a rate of 2.9 cm/yr. Total magma production and frequency of basaltic eruption accelerated between 5 and 0.25 m.y. and have decreased thereafter; this evolutionary sequence, coupled with the Sr-isotopic composition of the rocks, can be explained by magmatism caused by shear heating at the base of the lithosphere. The eastward drift of volcanism represents the absolute westward motion of the North America plate.-L.C.H.

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

    SciTech Connect

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

    1992-03-01

    An assessment of the risk of future volcanism has been conducted for isolation of high-level radioactive waste at the potential Yucca Mountain site in southern Nevada. Risk used in this context refers to a combined assessment of the probability and consequences of future volcanic activity. Past studies established bounds on the probability of magmatic disruption of a repository. These bounds were revised as additional data were gathered from site characterization studies. The probability of direct intersection of a potential repository located in an eight km{sup 2} area of Yucca Mountain by ascending basalt magma was bounded by the range of 10{sup {minus}8} to 10{sup {minus}10} yr{sup {minus}1 2}. The consequences of magmatic disruption of a repository were estimated in previous studies to be limited. The exact releases from such an event are dependent on the strike of an intruding basalt dike relative to the repository geometry, the timing of the basaltic event relative to the age of the radioactive waste and the mechanisms of release and dispersal of the waste radionuclides in the accessible environment. The combined low probability of repository disruption and the limited releases associated with this event established the basis for the judgement that the risk of future volcanism was relatively low. It was reasoned that that risk of future volcanism was not likely to result in disqualification of the potential Yucca Mountain site.

  11. Testing hypotheses for the use of Icelandic volcanic ashes as low cost, natural fertilizers

    NASA Astrophysics Data System (ADS)

    Seward, W.; Edwards, B.

    2012-04-01

    Andisols are soils derived from tephra/volcanic bedrock and are generally considered to be fertile for plant growth (cf. University of Hawaii at Manoa, CTAHR). However, few studies have been published examining the immediate effects of the addition of volcanic ash to soils immediately after an eruption. Our research is motivated by unpublished accounts from Icelandic farmers that the growing season following the 2010 Eyjafjallajökull eruption ended with unusually high yields in areas that were covered by ash from the eruption early in the spring. To test the hypothesis that addition of volcanic ash to soil would have no immediate effect on plant growth, we conducted a ~6 week growth experiment in at controlled environment at the Dickinson College Farm. The experiment used relatively fast growing grain seeds as a test crop, controlled watering, known quantities of peat as an organic base, and the following general experimental design: peat was mixed in known but systematically differing proportions with 1) commercial quartz sand, 2) basaltic ash from the 2004 Grimsvötn eruption, and 3) trachyandesite ash from the 2010 Eyjafjallajökull eruption. For all experiments, the seeds growing in the simulated soil created with the two different composition volcanic ash had higher germination rates, higher growth rates, and produced plants that were healthier in appearance than the soil made from peat mixed with quartz sand. Some differences were also noted between the germination and grow rates between the basaltic and trachyandesitic ash experiments as well. Working hypotheses to explain these results include (1) shard shapes and vesicles from volcanic ash provide better water retention than quartz, allowing water to be stored longer and increasing average soil moisture, and (2) chemical nutrients from the ash facilitate germination and growth of plants. Documenting the potential benefits of fresh volcanic ash as a fertilizer is important as use of fresh ash fertlizer

  12. Age hardening of 6061/alumina-silica fiber composite

    SciTech Connect

    Khangaonkar, P.R.; Shamsul, J.B.; Azmi, R.

    1994-12-31

    Continuous alumina-silica fiber (Altex of Sumitomo) which yields high performance composites with some aluminium alloys was tried for squeeze cast 6061 based composites with volume fractions of 0.5 and 0.32, and the matrix microhardness and resistivity changes during age hardening were studied. The matrix in the composites hardened much more than the unreinforced alloy. Microhardness increases of up to 70 VPN above the solution treated condition at various aging temperatures were observed. The resistivity variation indicated an appreciable state of internal stress which continued to persist even when hardness fell by overaging. Energy dispersive X-ray analysis indicated that the regions close to the fibers had a higher silicon content than the matrix, and amorphous silica in the fiber may have a role in the formation of an enriched layer which may help the bonding and strength in the composite.

  13. ORIGIN OF THE COSMIC-RAY SPECTRAL HARDENING

    SciTech Connect

    Tomassetti, Nicola

    2012-06-10

    Recent data from ATIC, CREAM, and PAMELA indicate that the cosmic-ray energy spectra of protons and nuclei exhibit a remarkable hardening at energies above 100 GeV nucleon{sup -1}. We propose that the hardening is an interstellar propagation effect that originates from a spatial change of the cosmic-ray transport properties in different regions of the Galaxy. The key hypothesis is that the diffusion coefficient is not separable into energy and space variables as usually assumed. Under this scenario, we can reproduce the observational data well. Our model has several implications for cosmic-ray acceleration/propagation physics and can be tested by ongoing experiments such as the Alpha Magnetic Spectrometer or Fermi-LAT.

  14. Hardening electronic devices against very high total dose radiation environments

    NASA Technical Reports Server (NTRS)

    Buchanan, B.; Shedd, W.; Roosild, S.; Dolan, R.

    1972-01-01

    The possibilities and limitations of hardening silicon semiconductor devices to the high neutron and gamma radiation levels and greater than 10 to the eighth power rads required for the NERVA nuclear engine development are discussed. A comparison is made of the high dose neutron and gamma hardening potential of bipolar, metal insulator semiconductors and junction field effect transistors. Experimental data is presented on device degradation for the high neutron and gamma doses. Previous data and comparisons indicate that the JFET is much more immune to the combined neutron displacement and gamma ionizing effects than other transistor types. Experimental evidence is also presented which indicates that p channel MOS devices may be able to meet the requirements.

  15. Stress and Distortion Evolution During Induction Case Hardening of Tube

    NASA Astrophysics Data System (ADS)

    Nemkov, Valentin; Goldstein, Robert; Jackowski, John; Ferguson, Lynn; Li, Zhichao

    2013-07-01

    Simulation of stresses during heat treatment relates usually to furnace heating. Induction heating provides a very different evolution of temperature in the part and therefore different stresses. This may be positive for service properties or negative, reducing component strength or even causing cracks. A method of coupled simulation between electromagnetic, thermal, structural, stress, and deformation phenomena during induction tube hardening is described. Commercial software package ELTA is used to calculate the power density distribution in the load resulting from the induction heating process. The program DANTE is used to predict temperature distribution, phase transformations, stress state, and deformation during heating and quenching. Analyses of stress and deformation evolution were made on a simple case of induction hardening of external (1st case) and internal (2nd case) surfaces of a thick-walled tubular body.

  16. A Brief Discussion of Radiation Hardening of CMOS Microelectronics

    SciTech Connect

    Myers, D.R.

    1998-12-18

    Commercial microchips work well in their intended environments. However, generic microchips will not fimction correctly if exposed to sufficient amounts of ionizing radiation, the kind that satellites encounter in outer space. Modern CMOS circuits must overcome three specific concerns from ionizing radiation: total-dose, single-event, and dose-rate effects. Minority-carrier devices such as bipolar transistors, optical receivers, and solar cells must also deal with recombination-generation centers caused by displacement damage, which are not major concerns for majority-carrier CMOS devices. There are ways to make the chips themselves more resistant to radiation. This extra protection, called radiation hardening, has been called both a science and an art. Radiation hardening requires both changing the designs of the chips and altering the ways that the chips are manufactured.

  17. Segmentation-free empirical beam hardening correction for CT

    SciTech Connect

    Schüller, Sören; Sawall, Stefan; Stannigel, Kai; Hülsbusch, Markus; Ulrici, Johannes; Hell, Erich; Kachelrieß, Marc

    2015-02-15

    Purpose: The polychromatic nature of the x-ray beams and their effects on the reconstructed image are often disregarded during standard image reconstruction. This leads to cupping and beam hardening artifacts inside the reconstructed volume. To correct for a general cupping, methods like water precorrection exist. They correct the hardening of the spectrum during the penetration of the measured object only for the major tissue class. In contrast, more complex artifacts like streaks between dense objects need other techniques of correction. If using only the information of one single energy scan, there are two types of corrections. The first one is a physical approach. Thereby, artifacts can be reproduced and corrected within the original reconstruction by using assumptions in a polychromatic forward projector. These assumptions could be the used spectrum, the detector response, the physical attenuation and scatter properties of the intersected materials. A second method is an empirical approach, which does not rely on much prior knowledge. This so-called empirical beam hardening correction (EBHC) and the previously mentioned physical-based technique are both relying on a segmentation of the present tissues inside the patient. The difficulty thereby is that beam hardening by itself, scatter, and other effects, which diminish the image quality also disturb the correct tissue classification and thereby reduce the accuracy of the two known classes of correction techniques. The herein proposed method works similar to the empirical beam hardening correction but does not require a tissue segmentation and therefore shows improvements on image data, which are highly degraded by noise and artifacts. Furthermore, the new algorithm is designed in a way that no additional calibration or parameter fitting is needed. Methods: To overcome the segmentation of tissues, the authors propose a histogram deformation of their primary reconstructed CT image. This step is essential for the

  18. Precipitation hardening in a dental low-gold alloy.

    PubMed

    Kim, Hyung-Il; Park, Young-Hwan; Lee, Hee-Kyung; Seol, Hyo-Joung; Shiraishi, Takanobu; Hisatsune, Kunihiro

    2003-03-01

    Age-hardening characteristics in a dental low-gold alloy composed of 40.0 wt% Au-35.0 wt% Ag-7.9 wt% Pd-7.0 wt% Cu-5.0 wt% In-3.5 wt% Zn-1.5 wt% Sn, were investigated by means of the hardness test, XRD study, SEM observations and EPMA. The following results were obtained. The age-hardening was characterized by a precipitation of Cu-rich alpha2 phase in the a phase. The softening that occurred following prolonged ageing was due to the heterogeneous formation of the fine nodular precipitates composed of the Ag-rich alpha1 phase and the Cu-rich alpha2 phase at the grain boundaries of the a phase. PMID:12790292

  19. Magnetic hardening in FePt nanostructured films

    SciTech Connect

    Liu, J.P.; Liu, Y.; Luo, C.P.; Shan, Z.S.; Sellmyer, D.J.

    1997-04-01

    FePt films have been prepared by sputtering Fe/Pt multilayers onto glass or silicon substrates. The thickness of the Fe and Pt layers was adjusted with the Fe:Pt atomic ratio from about 1:1 to 2:1. Magnetic hardening is observed after heat treatment at elevated temperatures, which led to coercivity values exceeding 20 kOe in samples with an Fe:Pt ratio around 1.2:1. The hardening originates from the formation of the tetragonal FePt phase with high magnetocrystalline anisotropy and a favorable microstructure. Two-phase composite films containing hard and soft phases were obtained when the Fe:Pt ratio increased. Under optimized processing conditions, composite films with energy products larger than 30 MGOe at room temperature have been successfully produced. {copyright} {ital 1997 American Institute of Physics.}

  20. Magnetic hardening in FePt nanostructured films

    NASA Astrophysics Data System (ADS)

    Liu, J. P.; Liu, Y.; Luo, C. P.; Shan, Z. S.; Sellmyer, D. J.

    1997-04-01

    FePt films have been prepared by sputtering Fe/Pt multilayers onto glass or silicon substrates. The thickness of the Fe and Pt layers was adjusted with the Fe:Pt atomic ratio from about 1:1 to 2:1. Magnetic hardening is observed after heat treatment at elevated temperatures, which led to coercivity values exceeding 20 kOe in samples with an Fe:Pt ratio around 1.2:1. The hardening originates from the formation of the tetragonal FePt phase with high magnetocrystalline anisotropy and a favorable microstructure. Two-phase composite films containing hard and soft phases were obtained when the Fe:Pt ratio increased. Under optimized processing conditions, composite films with energy products larger than 30 MG Oe at room temperature have been successfully produced.

  1. CMOS inverter design-hardened to the total dose effect

    SciTech Connect

    Roche, F.M.; Salager, L.

    1996-12-01

    This paper reports and discusses the experimental behavior of two inverter structures Rad-Hardened by Design to {sup 60}Co irradiation. The authors use the results on a set of basic circuits and transistors exposed to the same total doses as these structures to establish the effective formation conditions of the parasitic channel. Then this leakage evolution is related to the gate voltage history under irradiation. Finally, they take advantage of this intrinsic degradation property to propose a new Design Rad Hardened (DRH) cell. This structure considerably limits the Low Noise Margin degradation, helps to maintain the logic functionality with a High Output level and improves both the rad-tolerance and the static power consumption.

  2. Springback After the Lateral Bending of T-Section Rails of Work-Hardening Materials

    NASA Astrophysics Data System (ADS)

    Song, Youshuo; Yu, Zhonghua

    2013-11-01

    This paper studies the springback after the lateral bending of T-section rails, considering the work-hardening materials. A linear-hardening model and an elastic-plastic power-exponent hardening model of the material are adopted and compared with the real experimental stress-strain curve obtained from the uniaxial tension tests. The analytical formulas for the springback and residual curvatures are given. The numerical results indicate that the material hardening directly affects the accuracy of springback prediction compared with the experimental results. Besides, springback prediction is not sensitive to hardening parameters in the beginning of elastic-plastic bending deformation. Although there is an apparent yield stage in the true stress-strain curve, the adopted hardening models can achieve an allowable relative error, if hardening parameters are properly selected.

  3. Surface hardening of titanium alloys with melting depth controlled by heat sink

    DOEpatents

    Oden, Laurance L.; Turner, Paul C.

    1995-01-01

    A process for forming a hard surface coating on titanium alloys includes providing a piece of material containing titanium having at least a portion of one surface to be hardened. The piece having a portion of a surface to be hardened is contacted on the backside by a suitable heat sink such that the melting depth of said surface to be hardened may be controlled. A hardening material is then deposited as a slurry. Alternate methods of deposition include flame, arc, or plasma spraying, electrodeposition, vapor deposition, or any other deposition method known by those skilled in the art. The surface to be hardened is then selectively melted to the desired depth, dependent on the desired coating thickness, such that a molten pool is formed of the piece surface and the deposited hardening material. Upon cooling a hardened surface is formed.

  4. A beam hardening correction method based on HL consistency

    NASA Astrophysics Data System (ADS)

    Mou, Xuanqin; Tang, Shaojie; Yu, Hengyong

    2006-08-01

    XCT with polychromatic tube spectrum causes artifact called beam hardening effect. The current correction in CT device is carried by apriori polynomial from water phantom experiment. This paper proposes a new beam hardening correction algorithm that the correction polynomial depends on the relativity of projection data in angles, which obeys Helgasson-Ludwig Consistency (HL Consistency). Firstly, a bi-polynomial is constructed to characterize the beam hardening effect based on the physical model of medical x-ray imaging. In this bi-polynomial, a factor r(γ,β) represents the ratio of the attenuation contributions caused by high density mass (bone, etc.) to low density mass (muscle, vessel, blood, soft tissue, fat, etc.) respectively in the projection angle β and fan angle γ. Secondly, let r(γ,β)=0, the bi-polynomial is degraded as a sole-polynomial. The coefficient of this polynomial can be calculated based on HL Consistency. Then, the primary correction is reached, which is also more efficient in theoretical than the correction method in current CT devices. Thirdly, based on the result of a normal CT reconstruction from the corrected projection data, r(γ,β) can be estimated. Fourthly, the coefficient of bi-polynomial can also be calculated based HL Consistency and the final correction are achieved. Experiments of circular cone beam CT indicate this method an excellent property. Correcting beam hardening effect based on HL Consistency, not only achieving a self-adaptive and more precise correction, but also getting rid of regular inconvenient water phantom experiments, will renovate the correction technique of current CT devices.

  5. Mechanism and technological particular features of thermomagnetic hardening

    NASA Astrophysics Data System (ADS)

    Borovskij, S. M.; Mukhin, V. S.

    1993-10-01

    The particular features of mechanism associated with piece hardening of gas-turbine engines are analyzed. This mechanism is connected with the change of conditions for phase equilibrium and kinetics of transformations. It is important to estimate the nature of the formation of new ferromagnetic centers at phase transitions, when permanent, pulsed, or periodic magnetic fields act. Two factors should be taken into account: the power effect of the magnetic field and the increase of 'magnetic segregation' of a source nonferromagnetic matrix.

  6. Hardening of commercial CMOS PROMs with polysilicon fusible links

    NASA Technical Reports Server (NTRS)

    Newman, W. H.; Rauchfuss, J. E.

    1985-01-01

    The method by which a commercial 4K CMOS PROM with polysilicon fuses was hardened and the feasibility of applying this method to a 16K PROM are presented. A description of the process and the necessary minor modifications to the original layout are given. The PROM circuit and discrete device characteristics over radiation to 1000K rad-Si are summarized. The dose rate sensitivity of the 4K PROMs is also presented.

  7. Structural influences on the work hardening behavior of aluminum

    SciTech Connect

    Chu, D.

    1994-12-01

    Effects of various grain and subgrain morphologies on low temperature work hardening of pure Al is studied using tensile tests. Plotting the work hardening rate as a function of true stress, the work hardening is separable into two distinct regimes. Both regimes are approximated by a line {Theta} = {Theta}{sub 0} {minus} K{sub 2}{sigma}, where {Theta}{sub 0} is theoretical work hardening rate at zero stress and K{sub 2} is related to dynamic recovery rate. The first or early deformation regime exhibits greater values of {Theta}{sub 0} and K{sub 2} and can extend up to the first 10% strain of tensile deformation. This early deformation regime is contingent on the existence of a pre-existent dislocation substructure from previous straining. The {Theta}{sub 0} and K{sub 2} associated with the early deformation regime are dependent on the strength and orientation of the pre-existent dislocation substructure relative to the new strain path. At high enough temperatures, this pre-existent dislocation substructure is annealed out, resulting in the near elimination of the early deformation regime. In comparison, the latter regime is dominated by the initial grain and/or subgrain morphology and exhibit lower values of {Theta}{sub 0} and K{sub 2}. The actual value of K{sub 2} in the latter regime is strongly dependent on the existence of a subgrain morphology. Recrystallized or well-annealed microstructures exhibit greater values of K{sub 2} than microstructures that remain partially or fully unrecrystallized. The higher K{sub 2} value is indicative of a more rapid dynamic recovery rate and a greater degree of strain relaxation. The ability to achieve a more relaxed state produces a low-energy cellular dislocation substructure upon deformation. The introduction of subgrains hinders the evolution of a low-energy dislocation cell network, giving way to a more random distribution of the dislocation density.

  8. Sequential circuit design for radiation hardened multiple voltage integrated circuits

    DOEpatents

    Clark, Lawrence T.; McIver, III, John K.

    2009-11-24

    The present invention includes a radiation hardened sequential circuit, such as a bistable circuit, flip-flop or other suitable design that presents substantial immunity to ionizing radiation while simultaneously maintaining a low operating voltage. In one embodiment, the circuit includes a plurality of logic elements that operate on relatively low voltage, and a master and slave latches each having storage elements that operate on a relatively high voltage.

  9. Single cell mechanics: stress stiffening and kinematic hardening.

    PubMed

    Fernández, Pablo; Ott, Albrecht

    2008-06-13

    Cell mechanical properties are fundamental to the organism but remain poorly understood. We report a comprehensive phenomenological framework for the complex rheology of single fibroblast cells: a superposition of elastic stiffening and viscoplastic kinematic hardening. Despite the complexity of the living cell, its mechanical properties can be cast into simple, well-defined rules. Our results reveal the key role of crosslink slippage in determining mechanical cell strength and robustness. PMID:18643547

  10. The Technology of Mould Steel for Online Pre-hardening

    NASA Astrophysics Data System (ADS)

    Zhu, Dongmei; Liu, Guoyong; Li, Mouwei; Zhang, Shaojun; Bian, Xinxiao; Wanglin; Quan, Wang; Dai, Jinguo; Xubin; Wei, Chaocheng; Cai, Lijuan; Liu, Zuofeng; Gong, Shichuang; An, Zhengang

    This article describes a production method of mould steel pre-hardening, and focus on the advantage of this method, The technical core of method is the variable frequency and variable amplitude pulse uniform high-precision temperature control, which achieved by using strong-medium-weak water cooling, gas-water cooling and gas mist cooling composite cooling control technology. Optimizing the cooling rate path is a good method of optimizing quenched organization and structure.

  11. Reduction of metal artifacts: beam hardening and photon starvation effects

    NASA Astrophysics Data System (ADS)

    Yadava, Girijesh K.; Pal, Debashish; Hsieh, Jiang

    2014-03-01

    The presence of metal-artifacts in CT imaging can obscure relevant anatomy and interfere with disease diagnosis. The cause and occurrence of metal-artifacts are primarily due to beam hardening, scatter, partial volume and photon starvation; however, the contribution to the artifacts from each of them depends on the type of hardware. A comparison of CT images obtained with different metallic hardware in various applications, along with acquisition and reconstruction parameters, helps understand methods for reducing or overcoming such artifacts. In this work, a metal beam hardening correction (BHC) and a projection-completion based metal artifact reduction (MAR) algorithms were developed, and applied on phantom and clinical CT scans with various metallic implants. Stainless-steel and Titanium were used to model and correct for metal beam hardening effect. In the MAR algorithm, the corrupted projection samples are replaced by the combination of original projections and in-painted data obtained by forward projecting a prior image. The data included spine fixation screws, hip-implants, dental-filling, and body extremity fixations, covering range of clinically used metal implants. Comparison of BHC and MAR on different metallic implants was used to characterize dominant source of the artifacts, and conceivable methods to overcome those. Results of the study indicate that beam hardening could be a dominant source of artifact in many spine and extremity fixations, whereas dental and hip implants could be dominant source of photon starvation. The BHC algorithm could significantly improve image quality in CT scans with metallic screws, whereas MAR algorithm could alleviate artifacts in hip-implants and dentalfillings.

  12. Elastic constant versus temperature behavior of three hardened maraging steels

    NASA Technical Reports Server (NTRS)

    Ledbetter, H. M.; Austin, M. W.

    1985-01-01

    Elastic constants of three maraging steels were determined by measuring ultrasonic velocities. Annealed steels show slightly lower bulk moduli and considerably lower shear moduli than hardened steels. All the elastic constants (Young's modulus, shear modulus, bulk modulus and Poisson's ratio) show regular temperature behavior between 76 and 400 K. Young's modulus and the shear modulus increase with increasing yield strength, but the bulk modulus and Poisson's ratio are relatively unchanged. Elastic anisotropy is quite small.

  13. Control technology for surface treatment of materials using induction hardening

    SciTech Connect

    Kelley, J.B.; Skocypec, R.D.

    1997-04-01

    In the industrial and automotive industries, induction case hardening is widely used to provide enhanced strength, wear resistance, and toughness in components made from medium and high carbon steels. The process uses significantly less energy than competing batch process, is environmentally benign, and is a very flexible in-line manufacturing process. As such, it can directly contribute to improved component reliability, and the manufacture of high-performance lightweight parts. However, induction hardening is not as widely used as it could be. Input material and unexplained process variations produce significant variation in product case depth and quality. This necessitates frequent inspection of product quality by destructive examination, creates higher than desired scrap rates, and causes de-rating of load stress sensitive components. In addition, process and tooling development are experience-based activities, accomplished by trial and error. This inhibits the use of induction hardening for new applications, and the resultant increase in energy efficiency in the industrial sectors. In FY96, a Cooperative Research and Development Agreement under the auspices of the Technology Transfer Initiative and the Partnership for a New Generation of Vehicles was completed. A multidisciplinary team from Sandia National Labs and Delphi Saginaw Steering Systems investigated the induction hardening by conducting research in the areas of process characterization, computational modeling, materials characterization, and high speed data acquisition and controller development. The goal was to demonstrate the feasibility of closed-loop control for a specific material, geometry, and process. Delphi Steering estimated annual savings of $2-3 million per year due to reduced scrap losses, inspection costs, and machine down time if reliable closed-loop control could be achieved. A factor of five improvement in process precision was demonstrated and is now operational on the factory floor.

  14. Geochemical evidence for waning magmatism and polycyclic volcanism at Crater Flat, Nevada

    NASA Astrophysics Data System (ADS)

    Perry, F. V.; Crowe, B. M.

    Petrologic and geochemical studies of basaltic rocks in the Yucca Mountain region are currently focused on understanding the evolution of volcanism in the Crater Flat volcanic field and the mechanisms of polycyclic volcanism at the Lathrop Wells volcanic center, the youngest center in the Crater Flat volcanic field. Geochemical and petrologic data indicate that the magma chambers which supplied the volcanic centers in Crater Flat became situated at greater crustal depths as the field evolved. Deep magma chambers may be related to a waning magma flux that was unable to sustain upper crystal magma conduits and chambers. Geochemical data from the Lathrop Wells volcanic center indicate that eruptive units identified from field and geomorphic relationships are geochemically distinct. The geochemical variations cannot be explained by fractional crystallization of a single magma batch, indicating that several magma batches were involved in the formation of the Lathrop Wells center. Considering the low magma flux in the Yucca Mountain region in the Quaternary, the probability of several magma batches erupting essentially simultaneously at Lathrop Wells in considered remote. It is more likely that the Lathrop Wells center was formed by a series of eruptions that took place over many thousands of years. The geochemical data from Lathrop Wells is consistent with the concept of a complex, polycyclic volcano, which was originally proposed based on geomorphic and soil-development data.

  15. Geochemical evidence for waning magmatism and polycyclic volcanism at Crater Flat, Nevada

    SciTech Connect

    Perry, F.V.; Crowe, B.M.

    1991-12-31

    Petrologic and geochemical studies of basaltic rocks in the Yucca Mountain region are currently focused on understanding the evolution of volcanism in the Crater Flat volcanic field and the mechanisms of polycyclic volcanism at the Lathrop Wells volcanic center, the youngest center in the Crater Flat volcanic field. Geochemical and petrologic data indicate that the magma chambers which supplied the volcanic centers in Crater Flat became situated at greater crustal depths as the field evolved. Deep magma chambers may be related to a waning magma flux that was unable to sustain upper crystal magma conduits and chambers. Geochemical data from the Lathrop Wells volcanic center indicate that eruptive units identified from field and geomorphic relationships are geochemically distinct. The geochemical variations cannot be explained by fractional crystallization of a single magma batch, indicating that several magma batches were involved in the formation of the Lathrop Wells center. Considering the low magma flux in the Yucca Mountain region in the Quaternary, the probability of several magma batches erupting essentially simultaneously at Lathrop Wells in considered remote. It is more likely that the Lathrop Wells center was formed by a series of eruptions that took place over many thousands of years. The geochemical data from Lathrop Wells is consistent with the concept of a complex, polycyclic volcano, which was originally proposed based on geomorphic and soil-development data.

  16. Diffuse Helium Emission as a Precursory Sign of Volcanic Unrest

    NASA Astrophysics Data System (ADS)

    Padron, E.; Perez, N.; Hernandez Perez, P. A.; Sumino, H.; Melian Rodriguez, G.; Barrancos, J.; Nolasco, D.; Padilla, G.; Dionis, S.; Rodriguez, F.; Hernandez, I.; Calvo, D.; Peraza, M.; Nagao, K.

    2012-12-01

    Since July 16, 2011, an anomalous seismicity at El Hierro island, the youngest and smallest of the Canary Islands, was recorded by IGN seismic network. After the occurrence of more than 10,000 seismic events, volcanic tremor was recorded since 05:15 of the October 10, by all of the seismic stations on the island, with highest amplitudes recorded in the southernmost station. During the afternoon of October 12 a large light-green coloured area was observed in the sea to the souht of La Restinga village (at the southernmost part of El Hierro island), suggesting the existence of a submarine eruption. Since October 12, frequent episodes of, turbulent gas emission and foaming, and the appearance of steamy lava fragments has been observed on the sea surface. As part of the volcanic surveillance of the island, the Instituto Volcanologico de Canarias (INVOLCAN) geochemical monitoring program is carrying out diffuse helium surveys on the surface environment of El Hierro (soil atmosphere). This nobel gas has been investigated because it has been considered an almost ideal geochemical indicator because it is chemically inert, physically stable, nonbiogenic, sparingly soluble in water under ambient conditions and almost non-adsorbable. At each survey, 600 sampling sites covering the whole island and following an homogeneous distribution are selected for helium measurements in the soil gases, The helium concentration gradients with respect to its value on air (5.24 ppm) allow us to estimate a pure diffusive emission rate of helium throughout the island. The first survey was carried out on the summer of 2003, when the island was on a quiescence period. At this survey, the amount of helium released by the volcanic system of El Hierro was estimated in 6 kg/d. Since the beginning of the seismic unrest, 13 helium emission surveys have been carried out. The helium emission rate has shown an excellent agreement with the evolution of the volcanic crisis of the island, reaching 30 kg

  17. Volcanic Island Appears Near Tonga

    NASA Astrophysics Data System (ADS)

    Zielinski, Sarah

    2006-11-01

    A volcano known as Home Reef is now believed to be the source of a small island that appeared recently in Tonga, accordingto scientists from the Smithsonian Institution's Global Volcanism Program who had initially placed the location of the eruption and resulting island at nearby Metis Shoal. Mariners onboard the yacht Maiken

  18. Volcanic ash - Terrestrial versus extraterrestrial

    NASA Technical Reports Server (NTRS)

    Okeefe, J. A.

    1976-01-01

    A principal difference between terrestrial and extraterrestrial lavas may consist in the greater ability of terrestrial lavas to form thin films (like those of soap bubbles) and hence foams. It would follow that, in place of the pumice and spiny shards found in terrestrial volcanic ash, an extraterrestrial ash should contain minute spherules. This hypothesis may help to explain lunar microspherules.

  19. DETECTING VOLCANISM ON EXTRASOLAR PLANETS

    SciTech Connect

    Kaltenegger, L.; Sasselov, D. D.; Henning, W. G.

    2010-11-15

    The search for extrasolar rocky planets has already found the first transiting rocky super-Earth, Corot 7b, with a surface temperature that allows for magma oceans. Here, we investigate whether we could distinguish rocky planets with recent major volcanism by remote observation. We develop a model for volcanic eruptions on an Earth-like exoplanet based on the present-day Earth and derive the observable features in emergent and transmission spectra for multiple scenarios of gas distribution and cloud cover. We calculate the observation time needed to detect explosive volcanism on exoplanets in primary as well as secondary eclipse and discuss the likelihood of observing volcanism on transiting Earth-sized to super-Earth-sized exoplanets. We find that sulfur dioxide from large explosive eruptions does present a spectral signal that is remotely detectable especially for secondary eclipse measurements around the closest stars and ground-based telescopes, and report the frequency and magnitude of the expected signatures. The transit probability of a planet in the habitable zone decreases with distance from the host star, making small, nearby host stars the best targets.

  20. Infrasound research of volcanic eruptions

    NASA Astrophysics Data System (ADS)

    Marchetti, Emanuele; Ripepe, Maurizio

    2016-04-01

    Volcanic eruptions are efficient sources of infrasound produced by the rapid perturbation of the atmosphere by the explosive source. Being able to propagate up to large distances from the source, infrasonic waves from major (VEI 4 or larger) volcanic eruptions have been recorded for many decades with analogue micro-barometers at large regional distances. In late 1980s, near-field observations became progressively more common and started to have direct impact on the understanding and modeling of explosive source dynamics, to eventually play a primary role in volcano research. Nowadays, infrasound observation from a large variety of volcanic eruptions, spanning from VEI 0 to VEI 5 events, has shown a dramatic variability in terms of signature, excess pressure and frequency content of radiated infrasound and has been used to infer complex eruptive source mechanisms for the different kinds of events. Improved processing capability and sensors has allowed unprecedented precise locations of the explosive source and is progressively increasing the possibility to monitor volcanoes from distant records. Very broadband infrasound observations is also showing the relation between volcanic eruptions and the atmosphere, with the eruptive mass injection in the atmosphere triggering acoustic-gravity waves which eventually might control the ash dispersal and fallout.

  1. Descartes region - Evidence for Copernican-age volcanism.

    NASA Technical Reports Server (NTRS)

    Head, J. W., III; Goetz, A. F. H.

    1972-01-01

    A model that suggests that the high-albedo central region of the Descartes Formation was formed by Copernican-age volcanism was developed from Orbiter photography, Apollo 12 multispectral photography, earth-based spectrophotometry, and thermal IR and radar data. The bright surface either is abundant in centimeter-sized rocks or is formed from an insulating debris layer overlying a surface with an abundance of rocks in the 1- to 20-cm size range. On the basis of these data, the bright unit is thought to be a young pyroclastic deposit mantling older volcanic units of the Descartes Formation. Since the Apollo 16 target point is only 50 km NW of the central part of this unit, evidence for material associated with this unique highland formation should be searched for in returned soil and rock samples.

  2. Description of full-range strain hardening behavior of steels.

    PubMed

    Li, Tao; Zheng, Jinyang; Chen, Zhiwei

    2016-01-01

    Mathematical expression describing plastic behavior of steels allows the execution of parametric studies for many purposes. Various formulas have been developed to characterize stress strain curves of steels. However, most of those formulas failed to describe accurately the strain hardening behavior of steels in the full range which shows various distinct stages. For this purpose, a new formula is developed based on the well-known Ramberg-Osgood formula to describe the full range strain hardening behavior of steels. Test results of all the six types of steels show a three-stage strain hardening behavior. The proposed formula can describe such behavior accurately in the full range using a single expression. The parameters of the formula can be obtained directly and easily through linear regression analysis. Excellent agreements with the test data are observed for all the steels tested. Furthermore, other formulas such as Ludwigson formula, Gardner formula, UGent formula are also applied for comparison. Finally, the proposed formula is considered to have wide suitability and high accuracy for all the steels tested. PMID:27563511

  3. Study on boring hardened materials dryly by ultrasonic vibration cutter

    NASA Astrophysics Data System (ADS)

    Zhang, Jiangzhong; Zhang, Heng; Zhang, Yue

    2011-05-01

    It has been one of the difficulties that high-precision hole on hardened materials is machined. The supersonic vibration boring acoustic system in the lathe in which supersonic wave energy is applied on tool is introduced to create pulse power on the cutting process. The separation vibration cutting is achieved by the pulse force. The comparative tests on boring accuracy and surface quality are carried. The quality of surface machined by this method is compared to that by grinding. This cutting is the green cutting. The boring process system is stability. Under the condition that the cutting speed is less than or equal to 1/3 the tool vibration speed, the cutting force is pulse force and the Cutting energy is of high concentration in time, space and direction. The pulse energy effects on the cutting unit in less than one ten-thousandth second. Traditional cutting of irregular movement elastic compression are eliminated. The cutting force is greatly reduced. The cutting temperature is at room temperature. The tool life is greatly increased. Shape precision and surface quality is greatly improved. The regulations of the ultrasonic vibration boring dry cutting of hardened material are also summarized. The test results show that the ultrasonic vibration cutting tool boring is of very superior cutting mechanism and is a high-precision deep-hole machining of hardened materials, efficient cutting methods.

  4. Study on boring hardened materials dryly by ultrasonic vibration cutter

    NASA Astrophysics Data System (ADS)

    Zhang, Jiangzhong; Zhang, Heng; Zhang, Yue

    2010-12-01

    It has been one of the difficulties that high-precision hole on hardened materials is machined. The supersonic vibration boring acoustic system in the lathe in which supersonic wave energy is applied on tool is introduced to create pulse power on the cutting process. The separation vibration cutting is achieved by the pulse force. The comparative tests on boring accuracy and surface quality are carried. The quality of surface machined by this method is compared to that by grinding. This cutting is the green cutting. The boring process system is stability. Under the condition that the cutting speed is less than or equal to 1/3 the tool vibration speed, the cutting force is pulse force and the Cutting energy is of high concentration in time, space and direction. The pulse energy effects on the cutting unit in less than one ten-thousandth second. Traditional cutting of irregular movement elastic compression are eliminated. The cutting force is greatly reduced. The cutting temperature is at room temperature. The tool life is greatly increased. Shape precision and surface quality is greatly improved. The regulations of the ultrasonic vibration boring dry cutting of hardened material are also summarized. The test results show that the ultrasonic vibration cutting tool boring is of very superior cutting mechanism and is a high-precision deep-hole machining of hardened materials, efficient cutting methods.

  5. Hardening of smooth pulsed laser deposited PMMA films by heating

    NASA Astrophysics Data System (ADS)

    Fuchs, Britta; Schlenkrich, Felix; Seyffarth, Susanne; Meschede, Andreas; Rotzoll, Robert; Vana, Philipp; Großmann, Peter; Mann, Klaus; Krebs, Hans-Ulrich

    2010-03-01

    Smooth poly(methyl methacrylate) (PMMA) films without any droplets were pulsed laser deposited at a wavelength of 248 nm and a laser fluence of 125 mJ/cm2. After deposition at room temperature, the films possess low universal hardness of only 3 N/mm2. Thermal treatments up to 200°C, either during deposition or afterwards, lead to film hardening up to values of 200 N/mm2. Using a combination of complementary methods, two main mechanisms could be made responsible for this temperature induced hardening effect well above the glass transition temperature of 102°C. The first process is induced by the evaporation of chain fragments and low molecular mass material, which are present in the film due to the ablation process, leading to an increase of the average molecular mass and thus to hardening. The second mechanism can be seen in partial cross-linking of the polymer film as soon as chain scission occurs at higher temperatures and the mobility and reactivity of the polymer material is high enough.

  6. Obtaining strong zirconia ceramic by hardening and tempering

    SciTech Connect

    Pliner, S.Y.; Dabizha, A.A.; Komolikov, Y.I.; Rutman, D.S.; Toropov, Y.S.

    1985-07-01

    To determine whether it is possible to strengthen ceramics by means of hardening and tempering, the authors selected a solid solution pf 3.4% of Y/sub 2/O/sub 3/ (molar fraction) in ZrO/sub 2/. The solution was synthesized by combined precipitation of the compounds from an aqueous solution of chlorides. The filtered residue of hydroxides was dried and calcined at about 900/sup 0/C. The calcined material was milled for 80 h in an iron ball mill by the wet method with a ratio of materials: balls: water of 1:2:1. The material was then purified to remove tramp iron by treatment with HC1 with an addition of hydrogen peroxide, followed by decantation with distilled water. The specimens were heated to 2250-2300/sup 0/C in a furnace with a straight-through vertical channel of diameter 20 mm, a heating element made of stabilized zirconia, and high-temperature heat insulation made of porous ceramic-concrete based on ZrO/sub 2/. The hardening of the specimens at this temperature was done at a rate ensuring practically complete preservation of the cubic phase of ZrO/sub 2/. The tempering of the hardened specimens was done by the furnace with a silit heaters at 1400/sup 0/C over different times (0-85 h).

  7. Experimental generation of volcanic lightning

    NASA Astrophysics Data System (ADS)

    Cimarelli, Corrado; Alatorre-Ibargüengoitia, Miguel; Kueppers, Ulrich; Scheu, Bettina; Dingwell, Donald B.

    2014-05-01

    Ash-rich volcanic plumes that are responsible for injecting large quantities of aerosols into the atmosphere are often associated with intense electrical activity. Direct measurement of the electric potential at the crater, where the electric activity in the volcanic plume is first observed, is severely impeded, limiting progress in its investigation. We have achieved volcanic lightning in the laboratory during rapid decompression experiments of gas-particle mixtures under controlled conditions. Upon decompression (from ~100 bar argon pressure to atmospheric pressure), loose particles are vertically accelerated and ejected through a nozzle of 2.8 cm diameter into a large tank filled with air at atmospheric conditions. Because of their impulsive character, our experiments most closely represent the conditions encountered in the gas-thrust region of the plume, when ash is first ejected from the crater. We used sieved natural ash with different grain sizes from Popocatépetl (Mexico), Eyjafjallajökull (Iceland), and Soufrière Hills (Montserrat) volcanoes, as well as micrometric glass beads to constrain the influence of material properties on lightning. We monitored the dynamics of the particle-laden jets with a high-speed camera and the pressure and electric potential at the nozzle using a pressure transducer and two copper ring antennas connected to a high-impedance data acquisition system, respectively. We find that lightning is controlled by the dynamics of the particle-laden jet and by the abundance of fine particles. Two main conditions are required to generate lightning: 1) self-electrification of the particles and 2) clustering of the particles driven by the jet fluid dynamics. The relative movement of clusters of charged particles within the plume generates the gradient in electrical potential, which is necessary for lightning. In this manner it is the gas-particle dynamics together with the evolving particle-density distribution within different regions of

  8. Sustaining volcanism in Central Kamchatka

    NASA Astrophysics Data System (ADS)

    Nikulin, Alex

    Flux-induced melting in the mantle wedge acts as the driving mechanism of arc volcanism in subduction zone environments. The primary control on the geographical position of arc volcanic centers is the depth of the subducting plate beneath the overriding plate. Globally, the average depth to the subducting plate beneath volcanic arcs is estimated at ˜100km. Volcanoes of the Central Kamchatka Depression in Eastern Russia comprise the most active volcanic arc system in the world with the depth of the subducting Pacific plate beneath the arc estimated at 180-200km, greatly in excess of the global average. In my research I attempt to describe the special tectonic circumstances that explain the deviation of the subduction depth constraint on arc volcanism in Central Kamchatka. In my study I rely on geophysical and geochemical data and petrological modeling to propose a new geodynamic model to explain voluminous volcanic activity in Central Kamchatka. In the initial stage of the study I conducted a geophysical investigation using receiver function methodology to map and describe the contact of the subducting Juan de Fuca Plate in the well-instrumented Cascadia subduction zone. I calculated and compiled a database of receiver function profiles from stations along the extent of the Cascadia forearc and mapped a low velocity anisotropic zone proposed to be serpentinized material along the forearc axis. In the second stage of my study I applied a similar methodology to describe the sub-crustal structure of Central Kamchatka. Results of this effort suggested presence of a low-velocity zone in the upper mantle separate from the subducting Pacific plate. I proceeded to investigate the tectonic origin of this feature in the final stage of my dissertation work with the use of receiver function migration, geochemical analysis and petrological modeling. I was able to further constrain the position of the low velocity anomaly and derive geochemical and petrological evidence linking

  9. Hydrological Disturbances Caused By Explosive Volcanic Eruptions

    NASA Astrophysics Data System (ADS)

    Major, J. J.; Pierson, T. C.; Spicer, K. R.; Mark, L.; Yamakoshi, T.; Suwa, H.

    2014-12-01

    Explosive eruptions can drastically alter hydrogeomorphic regimes of drainage basins. The extent and degree of eruption-induced alteration scale with eruption magnitude, volcanic process, and basin proximity to a volcano. The most important effects of explosive eruptions on basin hydrology are ones that alter production and routing of runoff: (a) vegetation damage, which decreases (or eliminates) interception and evapotranspiration (ET); (b) reduction of surface infiltration owing to tephra deposition, which increases overland flow; (c) alteration of stream-channel hydraulics, which enables efficient transport of water and sediment; and (d) alterations to drainage networks, which accelerate or delay geomorphic response. In combination, these effects alter flood magnitude and frequency and rates of sediment transport. Vegetation loss allows more water to fall directly to the ground surface and reduces ET, which affects soil moisture, water storage and runoff pathways. Tephra fall, which typically paves the landscape with nearly impervious sediment, can reduce infiltration by as much as 2 orders of magnitude compared to pre-eruption rates and can increase direct runoff from near zero to as much as 90%. Even very thin layers (2-5 mm) of extremely fine tephra can increase runoff and decrease lag times between peak rainfall and peak runoff. Volcanic sedimentation in river valleys can increase channel gradient, reduce planform resistance, and smooth channel hydraulics, allowing for more efficient flow routing and producing larger, flashier flows. Hydrological effects of eruptive disturbance can linger for decades, but the most extreme effects typically last but a few years. However, lake formation through tributary blockage by thick deposits can delay response and extend the hydrologic legacy of eruptive disturbances. Failures of lake-impounding dams can produce large floods that renew downstream channel instability and rejuvenate headwater erosion.

  10. Intraglacial volcanism in the Western Volcanic Zone, Iceland

    NASA Astrophysics Data System (ADS)

    Jakobsson, S. P.; Johnson, G. L.

    2012-07-01

    The Western Volcanic Zone in Iceland (64.19° to 65.22° N) has the morphological characteristics of a distinct Mid-Atlantic ridge segment. This volcanic zone was mapped at a scale of 1:36.000, and 258 intraglacial monogenetic volcanoes from the Late Pleistocene (0.01-0.78 Ma) were identified and investigated. The zone is characterized by infrequent comparatively large volcanic eruptions and the overall volcanic activity appears to have been low throughout the Late Pleistocene. Tholeiitic basaltic rocks dominate in the Western Volcanic Zone with about 0.5 vol. % of intermediate and silicic rocks. The basalts divide into picrites, olivine tholeiites, and tholeiites. Three main eruptive phases can be distinguished in the intraglacial volcanoes: an effusive deep-water lava phase producing basal pillow lavas, an explosive shallow-water phase producing hyaloclastites and an effusive subaerial capping lava phase. Three evolutionary stages therefore charcterize these volcanoes; late dykes and irregular minor intrusions could be added as the fourth main stage. These intrusions are potential heat sources for short-lived hydrothermal systems and may play an important role in the final shaping of the volcanoes. Substantial parts of the hyaloclastites of each unit are proximal sedimentary deposits. The intraglacial volcanoes divide into two main morphological groups, ridge-shaped volcanoes, i.e., tindars (including pillow lava ridges) and subrectangular volcanoes, i.e., tuyas and hyaloclastite or pillow lava mounds. The volume of the tuyas is generally much larger than that of the tindars. The largest tuya, Eiríksjökull, is about 48 km3 and therefore the largest known monogenetic volcano in Iceland. Many of the large volcanoes, both tuyas and tindars, show a similar, systematic range in geochemistry. The most primitive compositions were erupted first and the magmas then changed to more differentiated compositions. The ridge-shaped tindars clearly erupted from volcanic

  11. Lead isotopes tracing weathering and atmospheric deposition in a small volcanic catchment

    NASA Astrophysics Data System (ADS)

    Négrel, Philippe; Petelet-Giraud, Emmanuelle; Guerrot, Catherine; Millot, Romain

    2015-09-01

    Lead isotopes were studied in soil and sediments of the small volcanic catchment in the Massif Central (France), a large area of Tertiary to Recent continental alkaline volcanism. The comparison of Pb and K (normalized to Zr) shows a linear evolution of weathering processes, whereby lead enrichment from atmospheric deposition is a major contributor explaining the deviation of several points from this line. A box model simulates the lead evolution in sediments from soil production on the hillslopes due to bedrock weathering and from anthropogenic input through atmospheric deposition and constrains the dynamics of sediment transfer. Lead isotope ratios decrease from bedrock to sediment and soil without any clear relationship when compared to lead contents. Pb isotopic compositions showed that most of the lead budget in sediment and soil results from bedrock weathering with influence of gasoline-additive-lead and past mining activities derived inputs, but no lead input from agricultural activity.

  12. Development of airblast and soil strength instrumentation

    NASA Astrophysics Data System (ADS)

    Coleman, P. L.; Groethe, M. A.

    1980-02-01

    The development and testing of airblast and soil strength gauges are presented. The airblast sensors include an accelerometer instrumented drag sphere to measure dynamic pressure and bar gauge probes to measure static, stagnation and reflected pressures at levels to 10 to the 8th power Pa (1 kilobar). The soil strength gauge is a shock hardened dynamic cone penetrator. An analysis of a slug type heat flux sensor is given.

  13. How Volcanism Controls Climate Change

    NASA Astrophysics Data System (ADS)

    Ward, P. L.

    2013-12-01

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

  14. An extension of the Kocks-Mecking model of work hardening to include kinematic hardening and its application to solutes in ferrite

    NASA Astrophysics Data System (ADS)

    Bouaziz, O.; Barbier, D.; Embury, J. D.; Badinier, G.

    2013-01-01

    It is well known that the addition of a solute can change both work-hardening characteristics and yield stress; however, there are few available models which describe the role of a solute in relation to both the isotropic and kinematic aspects of work hardening. The current work extends the well-established approach of Kocks and Mecking to include the occurrence of cross slip and its dependence on solute content. The proposed model is compared with experimental data for the system Fe-Al by reference both to the observed work hardening in monotonic loading and the Bauschinger effect measured in reverse shear tests. The agreement between the model and the experimental data is satisfactory and suggests a new description of work hardening which includes a prediction of the ratio of isotropic and kinematic hardening for a given solute content.

  15. Initial development of the Banda Volcanic Arc

    SciTech Connect

    Hartono, H.M.S. )

    1990-06-01

    The initial development of the Banda Volcanic Arc can be determined by obtaining absolute ages of granites or volcanics, stratigraphy of the Eocene Metan Volcanics of Timor as the oldest formation containing Banda Volcanic Arc extrusives, and tectonic analysis. Banda Arc volcanism is the result of subduction of oceanic crust under the volcanic arc. The time of initial subduction is related to initial seafloor spreading between Australia and Antarctica, which is identical to geomagnetic polarity time 34 (82 mybp). Therefore, 82 mybp can be used as one of the criteria to determine the birth of the Banda Volcanic Arc. With present available time data for determining the birth of the Banda Volcanic Arc, the minimum age coincides with the age of the Metan Volcanics (Eocene, 39-56 mybp) and the maximum age coincides with initial seafloor spreading between Australia and Antarctica (82 mybp). This time span is too long. With the assumption that it needs some time to develop from transcurrent faulting to subduction and volcanism, it is proposed that the initial development of Banda Arc volcanism was during early Tertiary.

  16. An Evaluation of the Corrosion and Mechanical Performance of Interstitially Surface-Hardened Stainless Steel

    NASA Astrophysics Data System (ADS)

    Jones, Jennifer L.; Koul, Michelle G.; Schubbe, Joel J.

    2014-06-01

    A surface hardening technique called "interstitial hardening" is commercially available, whereby interstitial carbon atoms are introduced into stainless steel surfaces without the formation of carbides. Surface hardening of machine elements such as impellors or fasteners would improve performance regarding cavitation and galling resistance, and has intensified interest in this process. However, there remains a need to characterize and validate the specific performance characteristics of the hardened materials. This paper describes experimental testing conducted on 316L stainless steel that has been surface hardened using available commercial techniques, using carbon as the interstitial atom. The corrosion performance of the hardened surface is assessed using electrochemical potentiodynamic testing to determine the breakdown potential in 3.5 wt.% NaCl solution to identify the most promising method. The hardness and thickness of the surface-hardened layer is characterized and compared using metallography and microhardness profiling. Corrosion fatigue and slow strain rate testing of untreated, hardened, and damaged, hardened surfaces exposed to ASTM seawater is conducted. Finally, critical galling stresses are determined and compared. Post-test examination of damage attempts to identify mechanisms of material failure and characterize how corrosion-assisted cracks initiate and grow in surface-hardened materials.

  17. Disruptive event analysis: Volcanism and igneous intrusion

    NASA Astrophysics Data System (ADS)

    Crowe, B. M.

    1980-08-01

    An evaluation was made of the disruptive effects of volcanic activity with respect to long term isolation of radioactive waste through deep geologic storage. Three major questions were 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 were the geometry of the magma repository intersection (partly controlled by depth of burial) and the nature of volcanism. Simplified probability calculations were attempted for areas of past volcanic activity.

  18. Influence of Mount St. Helens volcanic ash on alfalfa growth and nutrient uptake

    SciTech Connect

    Mahler, R.L.

    1984-01-01

    Concern has been expressed that large amounts of volcanic ash from the May 18, 1980 eruption of Mount St. Helens may have created potential nutritional problems associated with forage production in northern Idaho and eastern Washington to the extent that adjustments need to be made in soil test correlation data. The objectives of this greenhouse study were to : (1) determine the effect of varying amounts of volcanic ash mixed into soils of northern Idaho on total alfalfa biomass production, and (2) to determine the effect of various soil/ash mixtures on the nutrient concentrations of P, K, S, Ca, Mg, Mn and Zn in alfalfa. Alfalfa was grown in eight different northern Idaho soils amended with differing levels of volcanic ash (0, 20, 35, 50 and 75%) in the greenhouse. The alfalfa seeds were inoculated and fertilizer P and S were added to all treatments. Total plant biomass and P, K, S, Ca, Mg, Mn and Zn plant concentrations were measured. The eight were pooled for analysis and it was found that increasing amounts of volcanic ash increased alfalfa biomass production. Plant P, S, Ca, Mg and Zn concentrations also increased with increasing levels of ash. Conversely, increasing levels of ash resulted in lower alfalfa tissue K and Mn concentrations. 13 references, 7 figures.

  19. Preliminary geologic map of the Sleeping Butte volcanic centers

    SciTech Connect

    Crowe, B.M.; Perry, F.V.

    1991-07-01

    The Sleeping Butte volcanic centers comprise two, spatially separate, small-volume (<0.1 km{sup 3}) basaltic centers. The centers were formed by mildly explosive Strombolian eruptions. The Little Black Peak cone consists of a main scoria cone, two small satellitic scoria mounds, and associated lobate lava flows that vented from sites at the base of the scoria cone. The Hidden Cone center consists of a main scoria cone that developed on the north-facing slope of Sleeping Butte. The center formed during two episodes. The first included the formation of the main scoria cone, and venting of aa lava flows from radial dikes at the northeast base of the cone. The second included eruption of scoria-fall deposits from the summit crater. The ages of the Little Black Peak and the Hidden Cone are estimated to be between 200 to 400 ka based on the whole-rock K-Ar age determinations with large analytical undertainty. This age assignment is consistent with qualitative observations of the degree of soil development and geomorphic degradation of volcanic landforms. The younger episode of the Hidden Cone is inferred to be significantly younger and probably of Late Pleistocene or Holocene age. This is based on the absence of cone slope rilling, the absence of cone-slope apron deposits, and erosional unconformity between the two episodes, the poor horizon- development of soils, and the presence of fall deposits on modern alluvial surfaces. Paleomagnetic data show that the centers record similar but not identical directions of remanent magnetization. Paleomagnetic data have not been obtained for the youngest deposits of the Hidden Cone center. Further geochronology, soils, geomorphic, and petrology studies are planned of the Sleeping Butte volcanic centers 20 refs., 3 figs.

  20. Can rain cause volcanic eruptions?

    USGS Publications Warehouse

    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.

  1. Source mechanisms of volcanic tsunamis.

    PubMed

    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. PMID:26392617

  2. Hygroscopic properties of volcanic ash

    NASA Astrophysics Data System (ADS)

    Lathem, T. L.; Kumar, P.; Nenes, A.; Dufek, J.; Sokolik, I. N.; Trail, M.; Russell, A.

    2011-06-01

    Limited observational data exists on the physical interactions between volcanic ash particles and water vapor; yet it is thought that these interactions can strongly impact the microphysical evolution of ash, with implications for its atmospheric lifetime and transport, as well as formation of water and ice clouds. In this study, we investigate for the first time, the hygroscopic properties of ultra-fine volcanic ash (<125 μm diameter) from the eruptions of Mt. St. Helens in 1980, El Chichón in 1982, Tungurahua in 2006, Chaitén in 2008, Mt. Redoubt in 2009, and Eyjafjallajökull in 2010. The hygroscopicity of the ash particles is quantified by their ability to uptake water and nucleate into cloud drops under controlled levels of water vapor supersaturation. Evidence presented strongly suggests that ash uptakes water efficiently via adsorption and a simple parameterization of ash hygroscopicity is developed for use in ash plume and atmospheric models.

  3. Amazonian volcanic activity at the Syrtis volcanic province, Mars

    NASA Astrophysics Data System (ADS)

    Platz, Thomas; Jodlowski, Piotr; Fawdon, Peter; Michael, Greg; Tanaka, Kenneth

    2014-05-01

    The Syrtis Major volcanic province, including the entire Syrtis Major Planum, is located near the Martian highland/lowland transitional zone west of Isidis Planitia. It covers ≡7.4×105 km2 and contains two low-shield volcanic edifices with N-S elongated calderas named Nili and Meroe Paterae. The estimated thickness of erupted material in the province ranges from approximately 0.5 km to 1.0 km with a total volume of about 1.6-3.2×105 km3 [1]. The timing of volcanic activity in the Syrtis Major volcanic province has been suggested to be restricted to the Hesperian Period [1-4]. In the geological map of Greeley and Guest [2], volcanic material of Syrtis Major was assigned an Hesperian age based on the density of observed craters larger than 5 km in diameter. Using the same crater density range, recent studies of Hiesinger et al. [1] and Tanaka et al. [3] and Tanaka et al. [4] assigned an Early Hesperian and Early to Late Hesperian age, respectively, for the entire province. In this study we mapped lava flows, lava channels, and major lava-flow margins and report model ages for lava-flow formation and caldera segments of Nili and Meroe Paterae. The objective of this ongoing survey is to better understand the eruption frequency of this volcanic province. In total, we mapped 67 lava flows, caldera segments, and intra-crater fillings of which 55 were dated. Crater size-frequency distributions (CSFD) were mapped on HRSC and CTX imagery using CraterTools [5]. CSFDs were analyzed and model ages determined in Craterstats [6] using the production and chronology functions of Ivanov [7] and Hartmann and Neukum [8], respectively. A detailed description of the utilization of the crater-counting technique and its limitations with respect to small-scale mapping is given in Platz et al. [9]. Model ages range between 838 Ma (Middle Amazonian) to 3.6 Ga (Late Hesperian). In our survey, a broad age peak occurs between 2 to 2.6 Ga, continuously declining thereafter. We note that

  4. Understanding Volcanic Conduit Dynamics: from Experimental Fragmentation to Volcanic Eruptions

    NASA Astrophysics Data System (ADS)

    Arciniega-Ceballos, A.; Alatorre-Ibarguengoitia, M. A.; Scheu, B.; Dingwell, D. B.

    2011-12-01

    The investigation of conduit dynamics at high pressure, under controlled laboratory conditions is a powerful tool to understand the physics behind volcanic processes before an eruption. In this work, we analyze the characteristics of the seismic response of an "experimental volcano" focusing on the dynamics of the conduit behavior during the fragmentation process of volcanic rocks. The "experimental volcano" is represented by a shock tube apparatus, which consists of a low-pressure voluminous tank (3 x 0.40 m), for sample recovery; and a high-pressure pipe-like conduit (16.5 x 2,5 cm), which represents the volcanic source mechanism, where rock samples are pressurized and fragmented. These two serial steel pipes are connected and sealed by a set of diaphragms that bear pressures in a range of 4 to 20 MPa. The history of the overall process of an explosion consists of four steps: 1) the slow pressurization of the pipe-like conduit filled with solid pumice and gas, 2) the sudden removal of the diaphragms, 3) the rapid decompression of the system and 4) the ejection of the gas-particle mixture. Each step imprints distinctive features on the microseismic records, reflecting the conduit dynamics during the explosion. In this work we show how features such as waveform characteristics, the three components of the force system acting on the conduit, the independent components of the moment tensor, the volumetric change of the source mechanism, the arrival time of the shock wave and its velocity, are quantified from the experimental microseismic data. Knowing these features, each step of the eruptive process, the conduit conditions and the source mechanism characteristics can be determined. The procedure applied in this experimental approach allows the use of seismic field data to estimate volcanic conduit conditions before an eruption takes place. We state on the hypothesis that the physics behind the pressurization and depressurization process of any conduit is the same

  5. Io's surface, atmosphere and volcanism

    NASA Astrophysics Data System (ADS)

    Laver, Conor Murray

    Io's colorful appearance and unusual thermal emission have made it an object of interest for solar system astronomers for decades. Only recently have we become aware of the intimate connections between the tenuous atmosphere, the vibrant surface and the violent volcanic eruptions on this small moon. This work presents a series of studies which illuminate these three areas. Specifically, we found that there is a substantial time variability to the sulfur monoxide content of Io's atmosphere, and that the measured rotational temperature of the gas (550-1000K) implies a volcanic origin. We then focused on Io's volcanism during a serendipitous discovery of a major volcanic outburst at Tvashtar Catena. The OSIRIS instrument allowed us unprecedented spatial and spectral resolution, which we used to pinpoint the location of the outburst to 59 ° 1N, 121 ° 1W. With the H and K band spectra we determined a temperature of 1240 ° 4K with a surface emitting area of 57 ° 6km 2 . Finally we studied Io's surface through mapping the coverage of sulfur dioxide ice. Both low and high spatial resolution data displayed a largely equatorial distribution of ice, consistent with early studies by the Voyager and Galileo spacecraft. Importantly these results differ from some of the recent findings. We present, however, a potential unifying theory to explain this discrepancy, which may answer the long-standing question of the location of Io's ice. Included in the final chapter is further discussion of some of the technical challenges faced in this research, specifically with the OSIRIS instrument and the solid surface models used to interpret the sulfur dioxide ice data.

  6. Recalibrated Mariner 10 Color Mosaics: Implications for Mercurian Volcanism

    PubMed

    Robinson; Lucey

    1997-01-10

    Recalibration of Mariner 10 color image data allows the identification of distinct color units on the mercurian surface. We analyze these data in terms of opaque mineral abundance, iron content, and soil maturity and find color units consistent with the presence of volcanic deposits on Mercury's surface. Additionally, materials associated with some impact craters have been excavated from a layer interpreted to be deficient in opaque minerals within the crust, possibly analogous to the lunar anorthosite crust. These observations suggest that Mercury has undergone complex differentiation like the other terrestrial planets and the Earth's moon. PMID:8985010

  7. Volcanic mercury in Pinus canariensis.

    PubMed

    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. PMID:23760570

  8. Volcanism in Elysium Planitia, Mars

    NASA Technical Reports Server (NTRS)

    Mouginis-Mark, P. J.

    1984-01-01

    Geomorphic mapping revealed that the three volcanic constructs within Elysium Planitia (Hecates Tholus, elysium Mons and Albor Tholus) are very different in their overall morphology and represent three distinct types of martian volcano. Hecates Tholus was found to possess the most likely possible example of a young, explosively generated, air fall deposit, while the volume of magma erupted from Elysium Mons appears to have been orders of magnitude larger than that erupted from Albor Tholus. A primary aim of the regional geological analysis of Elysium Planitia is to further understand the volcanic and tectonic evolution of the area by the identification and interpretation of individual lava flows and their source vents. Lava flow size, spatial distribution, flow direction and the stratigraphic relationships of these lava flows to adjacent structural features were all measured. The topographic form of Elysium Mons has totally controlled the flow direction of lava flows within Elysium Planitia. Lava flows from Elysium Mons can be traced for distances of 150 to 250 km in a radial direction from the volcano. Parasitic vents located beyond the recognizable volcanic construct also conform to this radial pattern. A second unusual characteristic of the Elysium Planitia region is the high frequency of occurrence of sinuous channels that are morphologically similar to lunar sinuous rilles.

  9. Volcanic mercury in Pinus canariensis

    NASA Astrophysics Data System (ADS)

    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.

  10. Bayesian analysis of volcanic eruptions

    NASA Astrophysics Data System (ADS)

    Ho, Chih-Hsiang

    1990-10-01

    The simple Poisson model generally gives a good fit to many volcanoes for volcanic eruption forecasting. Nonetheless, empirical evidence suggests that volcanic activity in successive equal time-periods tends to be more variable than a simple Poisson with constant eruptive rate. An alternative model is therefore examined in which eruptive rate(λ) for a given volcano or cluster(s) of volcanoes is described by a gamma distribution (prior) rather than treated as a constant value as in the assumptions of a simple Poisson model. Bayesian analysis is performed to link two distributions together to give the aggregate behavior of the volcanic activity. When the Poisson process is expanded to accomodate a gamma mixing distribution on λ, a consequence of this mixed (or compound) Poisson model is that the frequency distribution of eruptions in any given time-period of equal length follows the negative binomial distribution (NBD). Applications of the proposed model and comparisons between the generalized model and simple Poisson model are discussed based on the historical eruptive count data of volcanoes Mauna Loa (Hawaii) and Etna (Italy). Several relevant facts lead to the conclusion that the generalized model is preferable for practical use both in space and time.

  11. Source mechanism of volcanic tremor

    SciTech Connect

    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.

  12. Volcanism in Elysium Planitia, Mars

    NASA Astrophysics Data System (ADS)

    Mouginis-Mark, P. J.

    1984-04-01

    Geomorphic mapping revealed that the three volcanic constructs within Elysium Planitia (Hecates Tholus, elysium Mons and Albor Tholus) are very different in their overall morphology and represent three distinct types of martian volcano. Hecates Tholus was found to possess the most likely possible example of a young, explosively generated, air fall deposit, while the volume of magma erupted from Elysium Mons appears to have been orders of magnitude larger than that erupted from Albor Tholus. A primary aim of the regional geological analysis of Elysium Planitia is to further understand the volcanic and tectonic evolution of the area by the identification and interpretation of individual lava flows and their source vents. Lava flow size, spatial distribution, flow direction and the stratigraphic relationships of these lava flows to adjacent structural features were all measured. The topographic form of Elysium Mons has totally controlled the flow direction of lava flows within Elysium Planitia. Lava flows from Elysium Mons can be traced for distances of 150 to 250 km in a radial direction from the volcano. Parasitic vents located beyond the recognizable volcanic construct also conform to this radial pattern. A second unusual characteristic of the Elysium Planitia region is the high frequency of occurrence of sinuous channels that are morphologically similar to lunar sinuous rilles.

  13. Quiescent Diffusive and Fumarolic Volcanic Bromocarbon Emissions

    NASA Astrophysics Data System (ADS)

    Schwandner, F. M.; Giźe, A. P.; Seward, T. M.; Hall, P. A.; Dietrich, V. J.

    2002-12-01

    volcanic "soil" close to high-temperature fumaroles. Other ODS found significantly above air, field and analytical system blanks include CH3Cl, CH3I, chlorophenols and chlorobenzenes. Abundances range from upper pptv to ppmv (e.g. CFC-11: max. 1200 pptv diffusive, 3700 pptv fumarolic/dry gas, dry air: 268 pptv). References\\ Bureau H. et al. (2000), EPSL 183 (1-2):51-60.\\Butler J.H. (2000), Nature 403:560-261.\\Gan J. Y. et al. (1995), J. Agric. Food Chem. 43:1361-1367.\\Gribble G. W. (2000), Environ. Sci. Pollut. Res. 7(1), 37-49.\\Isidorov V. A. et al. (1990), J. Atmos. Chem. 10(3):329-340.\\Jordan A. et al.(2000), ES&T 34:1122-1124.\\Rasmussen R. A. et al. (1980), EOS Transact. 61(6):67.\\Schwandner F. M. et al. (2000), J. Conf. Abs. 5(2):898.\\Schwandner F. M. et al. (2001), Chimia 55(7-8):590.\\Schwandner F.M. et al. (2002), Geoch. Soc. Spec. Publ. 8 (subm.).\\Solomon S. et al. (1992), JGR-A. 97:825-842.\\Stoiber R. E. (1995), In: A handbook of physical constants, AGU Reference Shelf 1:308-319.\\Wahrenberger C. et al. (1996), EOS Trans. 77(46):804.\\WMO (1998) Scientific assessment of ozone depletion. WMO Rep. No. 44, World Meteorological Organisation (WMO), Geneva.

  14. Method for increasing the rate of compressive strength gain in hardenable mixtures containing fly ash

    DOEpatents

    Liskowitz, John W.; Wecharatana, Methi; Jaturapitakkul, Chai; Cerkanowicz, deceased, Anthony E.

    1997-01-01

    The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction. The invention provides a method for increasing the rate of strength gain of a hardenable mixture containing fly ash by exposing the fly ash to an aqueous slurry of calcium oxide (lime) prior to its incorporation into the hardenable mixture. The invention further relates to such hardenable mixtures, e.g., concrete and mortar, that contain fly ash pre-reacted with calcium oxide. In particular, the fly ash is added to a slurry of calcium oxide in water, prior to incorporating the fly ash in a hardenable mixture. The hardenable mixture may be concrete or mortar. In a specific embodiment, mortar containing fly ash treated by exposure to an aqueous lime slurry are prepared and tested for compressive strength at early time points.

  15. Method for increasing the rate of compressive strength gain in hardenable mixtures containing fly ash

    DOEpatents

    Liskowitz, J.W.; Wecharatana, M.; Jaturapitakkul, C.; Cerkanowicz, A.E.

    1997-10-28

    The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction. The invention provides a method for increasing the rate of strength gain of a hardenable mixture containing fly ash by exposing the fly ash to an aqueous slurry of calcium oxide (lime) prior to its incorporation into the hardenable mixture. The invention further relates to such hardenable mixtures, e.g., concrete and mortar, that contain fly ash pre-reacted with calcium oxide. In particular, the fly ash is added to a slurry of calcium oxide in water, prior to incorporating the fly ash in a hardenable mixture. The hardenable mixture may be concrete or mortar. In a specific embodiment, mortar containing fly ash treated by exposure to an aqueous lime slurry are prepared and tested for compressive strength at early time points. 2 figs.

  16. Fatigue resistance of titanium alloy VT3-1 connection with surface work-hardening

    SciTech Connect

    Stepnov, M.N.; Agamirov, L.V.; Giatsintov, E.V.; Gus'kova, L.N.; Veitsman, M.G.

    1985-11-01

    The authors describe how surface work-hardening increases the endurance limit of smooth specimens of titanium alloy VT3-1 cut from bars by 25-30%. The range of the efficiency of strain-hardening by vibrational treatment and burnishing is 3-7%, the exact percentage depending on processing factors in each form of work-hardening. Work-hardening reduces scatter of fatigue characteristics, which enhances the effectiveness of the resulting strain-hardening with a decrease in the probability of fracture. Surface strain-hardening is recommended for alloy VT3-1, since it increases resistance to fatigue and reduces scatter of fatigue characteristics used in design.

  17. Case depth verification of hardened samples with Barkhausen noise sweeps

    SciTech Connect

    Santa-aho, Suvi; Vippola, Minnamari; Lepistö, Toivo; Hakanen, Merja; Sorsa, Aki; Leiviskä, Kauko

    2014-02-18

    An interesting topic of recent Barkhausen noise (BN) method studies is the application of the method to case depth evaluation of hardened components. The utilization of BN method for this purpose is based on the difference in the magnetic properties between the hardened case and the soft core. Thus, the detection of case depth with BN can be achieved. The measurements typically have been carried out by using low magnetizing frequencies which have deeper penetration to the ferromagnetic samples than the conventional BN measurement. However, the penetration depth is limited due to eddy current damping of the signal. We introduce here a newly found sweep measurement concept for the case depth evaluation. In this study sweep measurements were carried out with various magnetizing frequencies and magnetizing voltages to detect the effect of different frequency and voltage and their correspondence to the actual case depth values verified from destructive characterization. Also a BN measurement device that has an implemented sweep analysis option was utilised. The samples were either induction or case-hardened samples and sample geometry contained both rod samples and gear axle samples with different case depth values. Samples were also further characterized with Xray diffraction to study the residual stress state of the surface. The detailed data processing revealed that also other calculated features than the maximum slope division of the 1st derivative of the BN signal could hold the information about the case depth value of the samples. The sweep method was able to arrange the axles into correct order according to the case depth value even though the axles were used.

  18. Case depth verification of hardened samples with Barkhausen noise sweeps

    NASA Astrophysics Data System (ADS)

    Santa-aho, Suvi; Hakanen, Merja; Sorsa, Aki; Vippola, Minnamari; Leiviskä, Kauko; Lepistö, Toivo

    2014-02-01

    An interesting topic of recent Barkhausen noise (BN) method studies is the application of the method to case depth evaluation of hardened components. The utilization of BN method for this purpose is based on the difference in the magnetic properties between the hardened case and the soft core. Thus, the detection of case depth with BN can be achieved. The measurements typically have been carried out by using low magnetizing frequencies which have deeper penetration to the ferromagnetic samples than the conventional BN measurement. However, the penetration depth is limited due to eddy current damping of the signal. We introduce here a newly found sweep measurement concept for the case depth evaluation. In this study sweep measurements were carried out with various magnetizing frequencies and magnetizing voltages to detect the effect of different frequency and voltage and their correspondence to the actual case depth values verified from destructive characterization. Also a BN measurement device that has an implemented sweep analysis option was utilised. The samples were either induction or case-hardened samples and sample geometry contained both rod samples and gear axle samples with different case depth values. Samples were also further characterized with Xray diffraction to study the residual stress state of the surface. The detailed data processing revealed that also other calculated features than the maximum slope division of the 1st derivative of the BN signal could hold the information about the case depth value of the samples. The sweep method was able to arrange the axles into correct order according to the case depth value even though the axles were used.

  19. Radiation-Hardened Software for Space Flight Science Applications

    NASA Astrophysics Data System (ADS)

    Mehlitz, P. C.; Penix, J. J.; Markosian, L. Z.

    2005-12-01

    Hardware faults caused by radiation-induced Single Event Effects (SEEs) are a serious issue in space flight, especially affecting scientific missions in earth orbits crossing the poles or the South Atlantic Anomaly. Traditionally, SEEs are treated as a hardware problem, for example mitigated by radiation-hardened processors and shielding. Rad-hardened processors are expensive, exhibit a decade performance gap compared to COTS technology, have a larger form factor and require more power. Shielding is ineffective for high energy particles and increases launch weight. Hardware approaches cannot dynamically adapt protection levels for different radiation scenarios depending on solar activity and flight phase. Future hardware will exacerbate the problem due to higher chip densities and lower power levels. An alternative approach is to use software to mitigate SEEs. This "Radiation Hardened Software" (RHS) approach has two components: (1) RHS library and application design guidelines To increase robustness, we combine SEE countermeasures in three areas: prevention and detection; recovery; and reconfiguration. Prevention and detection includes an application- and heap-aware memory scanner, and dynamically adapted software Error Correction Codes to handle cache and multi-bit errors. Recovery mechanisms include exception firewalls and transaction-based software design patterns, to minimize data loss. Reconfiguration includes a heap manager to avoid damaged memory areas. (2) Software-based SEE Simulation Probabilistic effects require extensive simulation, with test environments that do not require original flight hardware and can simulate various SEE profiles. We use processor emulation software, interfaced to a debugger, to analyze SEE propagation and optimize RHS mechanisms. The simulator runs unmodified binary flight code, enables injecting randomized transient and permanent memory errors, providing execution traces and precise failure reproduction. The goal of RHS is to

  20. Reappraisal of the significance of volcanic fields

    NASA Astrophysics Data System (ADS)

    Cañón-Tapia, Edgardo

    2016-01-01

    "Volcanic field" is a term commonly used to loosely describe a group of volcanoes. Often, it is implicitly assumed that the volcanoes on a volcanic field are small, monogenetic and dominantly basaltic, but none of those attributes is indispensable on some definitions of the term. Actually, the term "volcanic field" can be used to describe a group of purely monogenetic edifices, a group of mixed monogenetic and polygenetic edifices, or even a group formed only by purely polygenetic edifices. Differences between each of those alternatives might be important, but the extent to which those differences are truly relevant remains still to be explored. Furthermore, there are several limitations on the current knowledge of this type of volcanic activity that explain the lack of a comprehensive effort to study volcanic fields in global contexts. In this work, issues concerning current definitions of a volcanic field are examined, and some criteria that can be used to distinguish volcanic fields from non-field volcanoes are suggested. Special attention is given to the role played by spatial scale on such a distinction. Also, the tectonic implications of their spatial distribution are explored. In particular, it is shown that volcanic fields are an important component of volcanic activity at a global scale that is closely associated to diffuse plate boundaries, and might well be considered the archetypical volcanic form of such tectonic scenarios.

  1. Disruptive event analysis: volcanism and igneous intrusion

    SciTech Connect

    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.

  2. Ductility and work hardening in nano-sized metallic glasses

    SciTech Connect

    Chen, D. Z.; Gu, X. W.; An, Q.; Goddard, W. A.; Greer, J. R.

    2015-02-09

    In-situ nano-tensile experiments on 70 nm-diameter free-standing electroplated NiP metallic glass nanostructures reveal tensile true strains of ∼18%, an amount comparable to compositionally identical 100 nm-diameter focused ion beam samples and ∼3 times greater than 100 nm-diameter electroplated samples. Simultaneous in-situ observations and stress-strain data during post-elastic deformation reveal necking and work hardening, features uncharacteristic for metallic glasses. The evolution of free volume within molecular dynamics-simulated samples suggests a free surface-mediated relaxation mechanism in nano-sized metallic glasses.

  3. Substorm effects in auroral spectra. [electron spectrum hardening

    NASA Technical Reports Server (NTRS)

    Eather, R. H.; Mende, S. B.

    1973-01-01

    A substorm time parameter is defined and used to order a large body of photometric data obtained on aircraft expeditions at high latitudes. The statistical analysis demonstrates hardening of the electron spectrum at the time of substorm, and it is consistent with the accepted picture of poleward expansion of aurora at the time of substorm and curvature drift of substorm-injected electrons. These features are not evident from a similar analysis in terms of magnetic time. We conclude that the substorm time concept is a useful ordering parameter for auroral data.

  4. Hardening communication ports for survival in electrical overstress environments

    NASA Technical Reports Server (NTRS)

    Clark, O. Melville

    1991-01-01

    Greater attention is being focused on the protection of data I/O ports since both experience and lab tests have shown that components at these locations are extremely vulnerable to electrical overstress (EOS) in the form of transient voltages. Lightning and electrostatic discharge (ESD) are the major contributors to these failures; however, these losses can be prevented. Hardening against transient voltages at both the board level and system level has a proven record of improving reliability by orders of magnitude. The EOS threats, typical failure modes, and transient voltage mitigation techniques are reviewed. Case histories are also reviewed.

  5. Action Of Cement Hardening On Artificial Hip Joint Components

    NASA Astrophysics Data System (ADS)

    Roder, U.; Niess, N.; Plitz, W.

    1981-05-01

    Artificial acetabular cups loose their original shape and undergo deformations during implantation, caused by the polymerization shrinkage of the bone cement. In laboratory experiments, two acetabula of different material - both common in clinical use - were studied by holographic real-time interferometry during cement hardening. This method picks up characteristic features in the transient behaviour of the form changes. It is shown, that temperature, porosity and shrinkage of the cement has a large influence on the form of a polyethylene acetabulum, whereas there is only little effect on an acetabulum, made of alumina ceramic.

  6. Surface hardening of cutting elements agricultural machinery vibro arc plasma

    NASA Astrophysics Data System (ADS)

    Sharifullin, S. N.; Adigamov, N. R.; Adigamov, N. N.; Solovev, R. Y.; Arakcheeva, K. S.

    2016-01-01

    At present, the state technical policy aimed at the modernization of worn equipment, including agriculture, based on the use of high-performance technology called nanotechnology. By upgrading worn-out equipment meant restoring it with the achievement of the above parameters passport. The existing traditional technologies are not suitable for the repair of worn-out equipment modernization. This is especially true of imported equipment. Out here alone - is the use of high-performance technologies. In this paper, we consider the use of vibro arc plasma for surface hardening of cutting elements of agricultural machinery.

  7. Active radiation hardening technology for fiber-optic source

    NASA Astrophysics Data System (ADS)

    Yang, Yuanhong; Suo, Xinxin; Yang, Mingwei

    2013-09-01

    We demonstrated an active radiation hardening technology for fiber optic source developed for high performance fiber optic gyroscope. The radiation characteristic of erbium-doped fiber was studied experimentally. The radiation induced attenuation (RIA) at 980nm pump light was identified to be the main reason for the degradation and there was photo-bleaching effect in EDF too. A variable parameters control technology was proposed and taken to keep the 980nm and 1550nm light energy stable and high stability and radiation-resistance fiber source with gauss profile spectrum was realized .The source can stand against more than 50 krad (Si) total radiation dose.

  8. An improved effective microorganism (EM) soil ball-making method for water quality restoration.

    PubMed

    Park, Gun-Seok; Khan, Abdur Rahim; Kwak, Yunyoung; Hong, Sung-Jun; Jung, ByungKwon; Ullah, Ihsan; Kim, Jong-Guk; Shin, Jae-Ho

    2016-01-01

    Soil balls containing the so-called effective microorganisms (EM) have been applied to improve water quality of small ponds, lakes, and streams worldwide. However, neither the physical conditions facilitating their proper application nor the diversity of microbial community in such soil balls have been investigated. In this study, the application of 0.75% of hardener to the soil balls exerted almost neutral pH (pH 7.3) which caused up to a fourfold increased hardness of the soil ball. Moreover, the 0.75% of hardener in the soil ball also improved the water quality due to a significant reduction in dissolved oxygen, total phosphorus, and total nitrogen contents. Metagenomic analysis of the microbial community in the soil ball with 0.75% hardener was compared with control (traditional soil ball) through next-generation sequencing. The traditional soil ball microbial community comprised 96.1% bacteria, 2.7% eukaryota, and 1% archaea, whereas the soil ball with 0.75% hardener comprised 71.4% bacteria, 27.9% eukaryota, and 0.2% viruses. Additionally, metagenomic profiles for both traditional and improved soil balls revealed that the various xenobiotic biodegradation, such as those for caprolactam, atrazine, xylene, toluene, styrene, bisphenol, and chlorocyclohexane might be responsible for organic waste cleanup. PMID:26498821

  9. Development of a Pressure-Dependent Constitutive Model with Combined Multilinear Kinematic and Isotropic Hardening

    NASA Technical Reports Server (NTRS)

    Allen Phillip A.; Wilson, Christopher D.

    2003-01-01

    The development of a pressure-dependent constitutive model with combined multilinear kinematic and isotropic hardening is presented. The constitutive model is developed using the ABAQUS user material subroutine (UMAT). First the pressure-dependent plasticity model is derived. Following this, the combined bilinear and combined multilinear hardening equations are developed for von Mises plasticity theory. The hardening rule equations are then modified to include pressure dependency. The method for implementing the new constitutive model into ABAQUS is given.

  10. Surface hardening of steel by laser and electron beam. (Latest citations from Metadex). Published Search

    SciTech Connect

    1996-08-01

    The bibliography contains citations concerning electron beam hardening of steels and alloys. Among the materials surface hardened are carbon and alloy steels, aircraft spur gears, nitrocarburized steel, turbine blades, titanium-carbon steel, titanium, and rolling bearings. Effect of transformation plasticity on residual stress fields in laser surface hardening treatment is also examined.(Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  11. Surface hardening of steel by laser and electron beam. (Latest citations from METADEX). Published Search

    SciTech Connect

    Not Available

    1994-09-01

    The bibliography contains citations concerning electron beam hardening of steels and alloys. Among the materials surface hardened are carbon and alloy steels, aircraft spur gears, nitrocarburized steel, turbine blades, titanium-carbon steel, titanium, and rolling bearings. Effect of transformation plasticity on residual stress fields in laser surface hardening treatment is also examined. (Contains a minimum of 93 citations and includes a subject term index and title list.)

  12. Hardening mechanisms in a dynamic strain aging alloy, Hastelloy X, during isothermal and thermomechanical cyclic deformation

    NASA Technical Reports Server (NTRS)

    Miner, R. V.; Castelli, M. G.

    1992-01-01

    The relative contributions of the hardening mechanisms in Hastelloy X during cyclic deformation were investigated by conducting isothermal cyclic deformation tests within a total strain range of +/-0.3 pct and at several temperatures and strain rates, and thermomechanical tests within several different temperature limits. The results of the TEM examinations and special constant structure tests showed that the precipitation on dislocations of Cr23C6 contributed to hardening, but only after sufficient time above 500 C. Solute drag alone produced very considerable cyclic hardening. Heat dislocation densities, peaking around 10 exp 11 per sq cm, were found to develop at temperatures producing the greatest cyclic hardening.

  13. Global CO2 Emission from Volcanic Lakes

    NASA Astrophysics Data System (ADS)

    Perez, N.; Hernandez Perez, P. A.; Padilla, G.; Melian Rodriguez, G.; Padron, E.; Barrancos, J.; Calvo, D.; Kusukabe, M.; Mori, T.; Nolasco, D.

    2009-12-01

    During the last two decades, scientists have paid attention to CO2 volcanic emissions and its contribution to the global C budget. Excluding MORBs as a net source of CO2 to the atmosphere, the global CO2 discharge from subaerial volcanism has been estimated about 300 Mt y-1 and this rate accounts for both visible (plume & fumaroles) and non-visible (diffuse) volcanic gas emanations (Mörner & Etíope, 2002). However, CO2 emissions from volcanic lakes have not been considered to estimate the global CO2 discharge from subaerial volcanoes. In order to improve this global CO2 emission rate and estimate the global CO2 emission from volcanic lakes, an extensive research on CO2 emission of volcanic lakes from Phillipines, Nicaragua, Guatemala, Mexico, Indonesia, Germany, France, Cameroon, Costa Rica, El Salvador and Ecuador had been recently carried out. In-situ measurements of CO2 efflux from the surface environment of volcanic lakes were performed by means of a modified floating device of the accumulation chamber method. To quantify the total CO2 emission from each volcanic lake, CO2 efflux maps were constructed using sequential Gaussian simulations (sGs). CO2 emission rates were normalized by the lake area (km2), and volcanic lakes were grouped following classification in acid, alkaline and neutral lakes. The observed average normalized CO2 emission rate values increase from alkaline (5.5 t km-2 d-1), neutral (210.0 t km-2 d-1), to acid (676.8 t km-2 d-1) volcanic lakes. Taking into account (i) these normalized CO2 emission rates from 31 volcanic lakes, (ii) the number of volcanic lakes in the world (~ 1100), (iii) the fraction of the investigated alkaline (45%), neutral (39%), and acid (16%) volcanic lakes, and (iv) the average areas of the investigated alkaline (36,8 km2), neutral (3,7 km2), and acid (0,5 km2) volcanic lakes; the global CO2 emission from volcanic lakes is about ~ 182 Mt year-1. This estimated value is about ~ 50% of the actual estimated global CO2

  14. Do volcanic emissions affect carbon gas fluxes in peatlands?

    NASA Astrophysics Data System (ADS)

    Harrison, Nicola; Delmelle, Pierre; Toet, Sylvia; Gauci, Vincent; Ineson, Phil

    2010-05-01

    Recently, a link has been suggested between volcanic deposition of SO4 and the suppression of CH4 emissions in northern peatlands (Gauci et al., 2008). This link stems from the widely accepted idea that acid rain SO4 additions to peatlands can cause a shift in microbial communities as SO4 reducing bacteria out-compete methanogens for substrates, which results in a suppression of CH4 emission. However, volcanic emissions contain besides S other chemically reactive species that are potentially harmful to the environment. In particular, gaseous and particulate F emissions from volcanoes constitute a steady or intermittent source of F emission and deposition into the environment both close to the source and within fallout range of large eruptions. The objective of this study was to investigate the effect of volcanic depositions of SO4, both alone and in combination with F, on CH4 emission in peatlands. Peat mesocosms collected from Pennine uplands in the UK were treated with weekly pulses of Na2SO4 and NaF over 20 weeks in doses of 74 kg SO4/ ha and 13.5 and 135 kg F /ha. CH4 emissions were measured at regular intervals by taking headspace samples, which were analysed by GC-FID. CO2 fluxes were also measured using a portable Infra Red Gas Analyser (IRGA). No significant differences in CH4 and CO2 emissions were observed for any of the treatments when compared to the controls, which had only received deionised water. These findings are in contrast with previous studies where SO4 reduces CH4 emission in peatlands. The reason for this is unclear but may be due to the heterogeneous nature of peat soils. An alternative explanation relates to the previous history of the soils used in the mesocosms which are known to have been previously exposed to large volumes of anthropogenic S pollution. This may have caused microbial communities to evolve and become acclimatised to high levels of S addition. In either case, the assumption that CH4 suppression in peatlands occurs upon

  15. Volcanic processes in the solar system

    USGS Publications Warehouse

    Carr, M.H.

    1987-01-01

    Eruptions of ammonia, water, and sulfur. These have become some of the concerns of planetary volcanologists as they try to understand volcanic processes on other planetary bodies. As exploration of the Solar System has continues, we have been confronted with more and more exotic forms of volcanism and have come to realize that the types of volcanic activity observed on Earth represent only a fraction of the array of volcanic phenomena that are possible. Some volcanic features of other planets have close terrestrial counterparts and appear to have been formed by similar mechanisms and from similar magmas to those on the Earth. but other features are totally different and appear to have been formed from materials that are not normally associated with volcanism on Earth.

  16. Volcanic processes in the Solar System

    USGS Publications Warehouse

    Carr, M.H.

    1987-01-01

    This article stresses that terrestrial volcanism represents only part of the range of volcanism in the solar system. Earth processes of volcanicity are dominated by plate tectonics, which does not seem to operate on other planets, except possibly on Venus. Lunar volcanicity is dominated by lava effusion at enormous rates. Mars is similar, with the addition to huge shield volcanoes developed over fixed hotspots. Io, the moon closest to Jupiter, is the most active body in the Solar System and, for example, much sulphur and silicates are emitted. The eruptions of Io are generated by heating caused by tides induced by Jupiter. Europa nearby seems to emit water from fractures and Ganymede is similar. The satellites of Saturn and Uranus are also marked by volcanic craters, but they are of very low temperature melts, possibly of ammonia and water. The volcanism of the solar system is generally more exotic, the greater the distance from Earth. -A.Scarth

  17. Geomorphic assessment of late Quaternary volcanism in the Yucca Mountain area, southern Nevada: Implications for the proposed high-level radioactive waste repository

    SciTech Connect

    Wells, S.G.; McFadden, L.D.; Renault, C.E.; Crowe, B.M.

    1991-03-01

    Volcanic hazard studies for high-level radioactive waste isolation in the Yucca Mountain area, Nevada, require a detailed understanding of Quaternary volcanism to forecast rates of volcanic processes. Recent studies of the Quaternary Cima volcanic fields in southern California have demonstrated that K-Ar dates of volcanic landforms are consistent with their geomorphic and pedologic properties. The systematic change of these properties with time may be used to provide age estimates of undated or questionably dated volcanic features. The reliability of radiometric age determinations of the youngest volcanic center, Lathrop Wells, near the proposed Yucca Mountain site in Nevada has been problematic. In this study, a comparison of morphometric, pedogenic, and stratigraphic data establishes that correlation of geomorphic and soil properties between the Cima volcanic field and the Yucca Mountain area is valid. Comparison of the Lathrop Wells cinder cone to a 15-20 ka cinder cone in California shows that their geomorphic-pedogenic properties are similar and implies that the two cones are of similar age. The authors of ca. 0.27 Ma for the latest volcanic activity at Lathrop Wells, approximately 20 km from the proposed repository, may be in error by as much as an order of magnitude and that the most recent volcanic activity is no older than 20 ka.

  18. Geomorphic assessment of late Quarternary volcanism in the Yucca Mountain area, southern Nevada: Implication for the proposed high-level radiocative waste repository

    SciTech Connect

    Wells, S.G.; McFadden, L.D.; Renault, C.E.; Crowe, B.M.

    1990-06-01

    Volcanic hazard studies for high-level radioactive waste isolation in the Yucca Mountain area, Nevada, require a detailed understanding of Quaternary volcanism to forecast rates of volcanic processes. Recent studies of the Quaternary Cima volcanic field in southern California have demonstrated that K-Ar dates of volcanic landforms are consistent with their geomorphic and pedologic properties. The systematic change of these properties with time may be used to provide age estimates of undated or questionably dated volcanic features. The reliability of radiometric age determinations of the youngest volcanic center, Lathrop Wells, near the proposed Yucca Mountain site in Nevada has been problematic. In this study, a comparison of morphometric, pedogenic, and stratigraphic data establishes that correlation of geomorphic and soil properties between the Cima volcanic field and the Yucca Mountain area is valid. Comparison of the Lathrop Wells cinder cone to a 15-20 ka cinder cone in California shows that their geomorphic-pedogenic properties are similar and implies that the two cones are of similar age. We conclude that previous determinations of ca. 0.27 Ma for the latest volcanic activity at Lathrop Wells, approximately 20 km from the proposed repository, may be in error by as much as an order of magnitude and that the most recent volcanic activity is no older than 20ka.

  19. Geomorphic assessment of late Quaternary volcanism in the Yucca Mountain area, southern Nevada: Implications for the proposed high-level radioactive waste repository

    NASA Astrophysics Data System (ADS)

    Wells, S. G.; McFadden, L. D.; Renault, C. E.; Crowe, B. M.

    1990-06-01

    Volcanic hazard studies for high-level radioactive waste isolation in the Yucca Mountain area, Nevada, require a detailed understanding of Quaternary volcanism to forecast rates of volcanic processes. Recent studies of the Quaternary Cima volcanic field in southern California have demonstrated that K-Ar dates of volcanic landforms are consistent with their geomorphic and pedologic properties. The systematic change of these properties with time may be used to provide age estimates of undated or questionably dated volcanic features. The reliability off radiometric age determinations of the youngest volcanic center, Lathrop Wells, near the proposed Yucca Mountain site in Nevada has been problematic. In this study, a comparison of morphometric, pedogenic, and stratigraphic data establishes that correlation of geomorphic and soil properties between the Cima volcanic field and the Yucca Mountain area is valid. Comparison of the Lathrop Wells cinder cone to a 15-20 ka cinder cone in California shows that their geomorphic-pedogenic properties are similar and implies that the two cones are of similar age. We conclude that previous determinations of ca. 0.27 Ma for the latest volcanic activity at Lathrop Wells, approximately 20 km from the proposed repository, may be in error by as much as an order of magnitude and that the most recent volcanic activity is no older than 20 ka.

  20. A radiation-hardened, computer for satellite applications

    SciTech Connect

    Gaona, J.I. Jr.

    1996-08-01

    This paper describes high reliability radiation hardened computers built by Sandia for application aboard DOE satellite programs requiring 32 bit processing. The computers highlight a radiation hardened (10 kGy(Si)) R3000 executing up to 10 million reduced instruction set instructions (RISC) per second (MIPS), a dual purpose module control bus used for real-time default and power management which allows for extended mission operation on as little as 1.2 watts, and a local area network capable of 480 Mbits/s. The central processing unit (CPU) is the NASA Goddard R3000 nicknamed the ``Mongoose or Mongoose 1``. The Sandia Satellite Computer (SSC) uses Rational`s Ada compiler, debugger, operating system kernel, and enhanced floating point emulation library targeted at the Mongoose. The SSC gives Sandia the capability of processing complex types of spacecraft attitude determination and control algorithms and of modifying programmed control laws via ground command. And in general, SSC offers end users the ability to process data onboard the spacecraft that would normally have been sent to the ground which allows reconsideration of traditional space-grounded partitioning options.

  1. DISCREPANT HARDENING OBSERVED IN COSMIC-RAY ELEMENTAL SPECTRA

    SciTech Connect

    Ahn, H. S.; Ganel, O.; Han, J. H.; Kim, K. C.; Lee, M. H.; Lutz, L.; Malinin, A.; Allison, P.; Beatty, J. J.; Bagliesi, M. G.; Bigongiari, G.; Maestro, P.; Marrocchesi, P. S.; Childers, J. T.; DuVernois, M. A.; Conklin, N. B.; Coutu, S.; Mognet, S. I.; Jeon, J. A.; Minnick, S.

    2010-05-01

    The balloon-borne Cosmic Ray Energetics And Mass experiment launched five times from Antarctica has achieved a cumulative flight duration of about 156 days above 99.5% of the atmosphere. The instrument is configured with complementary and redundant particle detectors designed to extend direct measurements of cosmic-ray composition to the highest energies practical with balloon flights. All elements from protons to iron nuclei are separated with excellent charge resolution. Here, we report results from the first two flights of {approx}70 days, which indicate hardening of the elemental spectra above {approx}200 GeV/nucleon and a spectral difference between the two most abundant species, protons and helium nuclei. These results challenge the view that cosmic-ray spectra are simple power laws below the so-called knee at {approx}10{sup 15} eV. This discrepant hardening may result from a relatively nearby source, or it could represent spectral concavity caused by interactions of cosmic rays with the accelerating shock. Other possible explanations should also be investigated.

  2. Dislocation Starvation and Exhaustion Hardening in Mo-alloy Nanofibers

    SciTech Connect

    Chisholm, Claire; Bei, Hongbin; Lowry, M. B.; Oh, Jason; Asif, S.A. Syed; Warren, O.; Shan, Zhiwei; George, Easo P; Minor, Andrew

    2012-01-01

    The evolution of defects in Mo alloy nanofibers with initial dislocation densities ranging from 0 to 1.6 1014 m2 were studied using an in situ push-to-pull device in conjunction with a nanoindenter in a transmission electron microscope. Digital image correlation was used to determine stress and strain in local areas of deformation. When they had no initial dislocations the Mo alloy nanofibers suffered sudden catastrophic elongation following elastic deformation to ultrahigh stresses. At the other extreme fibers with a high dislocation density underwent sustained homogeneous deformation after yielding at much lower stresses. Between these two extremes nanofibers with intermediate dislocation densities demonstrated a clear exhaustion hardening behavior, where the progressive exhaustion of dislocations and dislocation sources increases the stress required to drive plasticity. This is consistent with the idea that mechanical size effects ( smaller is stronger ) are due to the fact that nanostructures usually have fewer defects that can operate at lower stresses. By monitoring the evolution of stress locally we find that exhaustion hardening causes the stress in the nanofibers to surpass the critical stress predicted for self-multiplication, supporting a plasticity mechanism that has been hypothesized to account for the rapid strain softening observed in nanoscale bcc materials at high stresses.

  3. Folding and faulting of strain-hardening sedimentary rocks

    USGS Publications Warehouse

    Johnson, A.M.

    1980-01-01

    The question of whether single- or multi-layers of sedimentary rocks will fault or fold when subjected to layer-parallel shortening is investigated by means of the theory of elastic-plastic, strain-hardening materials, which should closely describe the properties of sedimentary rocks at high levels in the Earth's crust. The most attractive feature of the theory is that folding and faulting, intimately related in nature, are different responses of the same idealized material to different conditions. When single-layers of sedimentary rock behave much as strain-hardening materials they are unlikely to fold, rather they tend to fault, because contrasts in elasticity and strength properties of sedimentary rocks are low. Amplifications of folds in such materials are negligible whether contacts between layer and media are bonded or free to slip for single layers of dolomite, limestone, sandstone, or siltstone in media of shale. Multilayers of these same rocks fault rather than fold if contacts are bonded, but they fold readily if contacts between layers are frictionless, or have low yield strengths, for example due to high pore-water pressure. Faults may accompany the folds, occurring where compression is increased in cores of folds. Where there is predominant reverse faulting in sedimentary sequences, there probably were few structural units. ?? 1980.

  4. Analysis on sheet cyclic plastic deformation using mixed hardening model

    NASA Astrophysics Data System (ADS)

    Li, Qun; Jin, Miao; Yuxin, Zhu

    2013-05-01

    Treating the cyclic deformation problem of sheet flowing through drawbead as the object of the research, using HILL anisotropy yield criterion and mixed hardening model, the cyclic plastic deformation mechanism of sheet was studied, the deformation characteristics of sheet subjected to cyclic loads were revealed, and the influence of Bauschinger effect on stress-strain circulating relationship and the influence of bending neutral layer migration on the stress of sheet's intermediate integral point were analyzed as well. The effectiveness of the model was verified by experiments. The results of analysis were showed that the stress values influenced by Bauschinger effect were different at the yield point of reverse loading and the point of unloading during the cyclic deformation. The stress rate at the yield point of reverse loading and the point of unloading in different loading branches was also different. The stress-strain circulating relationship in different loading branches can be approximately treated as bilinear. The tangent modulus of each loading branch showed a significant downward trend as the times of the reverse loading increased. The tangent modulus calculated by the mixed hardening model after the second loading branch reduced to less than 21% of the first loading tangent modulus. Effected by the neutral layer migration, the stress-strain curve of integral point of sheet's intermediate layer showed alternating transition phenomenon of the tensile stress and compressive stress.

  5. Effects of residual stress on irradiation hardening in stainless steels

    NASA Astrophysics Data System (ADS)

    Okubo, N.; Miwa, Y.; Kondo, K.; Kaji, Y.

    2009-04-01

    Effects of residual stress on irradiation hardening were studied in advance for predicting irradiation assisted stress corrosion cracking. The specimens of SUS316 and SUS316L with several % plastic strains, which correspond to weld residual stress, were prepared by bending and keeping deformation under irradiation. Ion irradiations of 12 MeV Ni 3+ were performed at 330, 400 and 550 oC to 45 dpa. No bended specimen was simultaneously irradiated with the bended specimen. The residual stress was estimated by X-ray residual stress measurements before and after the irradiation. The micro-hardness was measured by using nanoindenter. The residual stress did not relax even for the case of the higher temperature aging at 500 oC for the same time of irradiation. The residual stress after ion irradiation up to high dpa, however, relaxed at these experimental temperatures. The irradiation hardening of stressed specimen was obviously lower than that of un-stressed one in case of SUS316L irradiated at 300 oC to 12 dpa.

  6. idRHa+ProMod - Rail Hardening Control System

    NASA Astrophysics Data System (ADS)

    Ferro, L.

    2016-03-01

    idRHa+ProMod is the process control system developed by Primetals Technologies to foresee the thermo-mechanical evolution and micro-structural composition of rail steels subjected to slack quenching into idRHa+ Rail Hardening equipments in a simulation environment. This tool can be used both off-line or in-line, giving the user the chance to test and study the best cooling strategies or letting the automatic control system free to adjust the proper cooling recipe. Optimization criteria have been tailored in order to determine the best cooling conditions according to the metallurgical requirements imposed by the main rail standards and also taking into account the elastoplastic bending phenomena occurring during all stages of the head hardening process. The computational core of idRHa+ProMod is a thermal finite element procedure coupled with special algorithms developed to work out the main thermo-physical properties of steel, to predict the non-isothermal austenite decomposition into all the relevant phases and subsequently to evaluate the amount of latent heat of transformation released, the compound thermal expansion coefficient and the amount of plastic deformation in the material. Air mist and air blades boundary conditions have been carefully investigated by means of pilot plant tests aimed to study the jet impingement on rail surfaces and the cooling efficiency at all working conditions. Heat transfer coefficients have been further checked and adjusted directly on field during commissioning. idRHa+ is a trademark of Primetals Technologies Italy Srl

  7. Assessing the volcanic probability of Martian landforms

    NASA Technical Reports Server (NTRS)

    Otoole, M.

    1982-01-01

    A table for use in identifying Martian land forms that may be volcanic in nature is presented. Eight types of known volcanic features and associations are described and each assigned a point value based on the degree to which it is thought to be characteristic of volcanoes. The system is applied to four well known Martian volcanoes and to other Martian features which may or may not be volcanic in origin.

  8. Hydrothermal activity and subsurface soil complexity: implication for outgassing processes at Solfatara crater, Campi Flegrei caldera

    NASA Astrophysics Data System (ADS)

    Montanaro, Cristian; Mayer, Klaus; Scheu, Bettina; Isaia, Roberto; Mangiacapra, Annarita; Gresse, Marceau; Vandemeulebrouck, Jean; Moretti, Roberto; Dingwell, Donald B.

    2016-04-01

    The Solfatara area and its fumaroles are the main surface phenomena of the vigorous hydrothermal activity within the active Campi Flegrei caldera system. The existing fault system appears to have a major control on outgassing which in turn leads to a strong alteration of the volcanic products. Moreover the maar-nature of the crater, and its filling by more recent volcanic deposits, resulted in a complex fractured and multilayered cap to the rising gases. As a consequence the hydrothermal alteration differently affects the rocks within the crater, including pyroclastic fallout ash beds, pyroclastic density current deposits, breccias and lavas. The induced changes in both original microstructure and physical and mechanical properties of the rocks control the outgassing behavior. Here, we report results from a measurement survey conducted in July 2015, and aimed to characterize the in-situ physical (temperature, humidity) and mechanical (permeability, strength, stiffness) properties. The survey also included a mapping of the surficial hydrothermal features and their distributions. Chemical analyses and laboratory measurements (porosity, granulometry) of selected samples were additionally performed. Results show that the crater floor area comprises very different kinds of soils, from fine grained, thin laminated deposits around the two bubbling Fangaia mud pools, to crusted hummock formations along the SE and NE border of the crater. Dry and solid alunite-rich deposits are present in the western and southern part. Furthermore we observed evidences of a beginning of crust formation within the central part of the crater. A large range of surface temperatures, from boiling point to ambient temperature, were measured throughout the surveyed area. Outgassing occurs mainly along the crack system, which has also generated the crusted hummocks. Elsewhere the fluid circulation in the subsoil is favored by the presence of coarse and highly porous sulfur-hardened levels, whereas

  9. The intensities and magnitudes of volcanic eruptions

    USGS Publications Warehouse

    Sigurdsson, H.

    1991-01-01

    Ever since 1935, when C.F Richter devised the earthquake magnitude scale that bears his name, seismologists have been able to view energy release from earthquakes in a systematic and quantitative manner. The benefits have been obvious in terms of assessing seismic gaps and the spatial and temporal trends of earthquake energy release. A similar quantitative treatment of volcanic activity is of course equally desirable, both for gaining a further understanding of the physical principles of volcanic eruptions and for volcanic-hazard assessment. A systematic volcanologic data base would be of great value in evaluating such features as volcanic gaps, and regional and temporal trends in energy release.  

  10. Episodes of Aleutian Ridge explosive volcanism

    USGS Publications Warehouse

    Hein, J.R.; Scholl, D. W.; Miller, J.

    1978-01-01

    Earlier workers have overlooked deep-sea bentonite beds when unraveling the Cenozoic volcanic history of an area. In the North Pacific, identification of Miocene and older volcanic episodes is possible only if both altered (bentonite) and unaltered ash beds are recognized. Our study, which includes bentonite beds, shows that volcanism on the Aleutian Ridge and Kamchatka Peninsula has been cyclic. Volcanic activity seems to have increased every 2.5 ?? 10 6 years for the past 10 ?? 106 years and every 5.0 ?? 106 years for the time span from 10 to 20 ?? 10 6 years ago. The middle and late Miocene and the Quaternary were times of greatly increased volcanic activity in the North Pacific and elsewhere around the Pacific Basin. The apparent absence of a volcanic record before the late Miocene at Deep Sea Drilling Project site 192 is the result not of plate motion, as suggested by Stewart and by Ninkovich and Donn, but rather of the diagenesis of ash layers. Major, apparently global volcanic episodes occurred at least twice in the last 20 ?? 106 years. Yet, only one major glacial epoch (the Pleistocene) has occurred. Therefore, even though glaciation coincided with an increase in Quaternary volcanism, the increased volcanism itself may not have been the primary cause of global cooling. Copyright ?? 1978 AAAS.

  11. Laboratory studies of volcanic jets

    NASA Astrophysics Data System (ADS)

    Kieffer, Susan Werner; Sturtevant, Bradford

    1984-09-01

    The study of the fluid dynamics of violent volcanic eruptions by laboratory experiment is described, and the important fluid-dynamic processes that can be examined in laboratory models are discussed in detail. In preliminary experiments, pure gases are erupted from small reservoirs. The gases used are Freon 12 and Freon 22, two gases of high molecular weight and high density that are good analogs of heavy and particulate-laden volcanic gases; nitrogen, a moderate molecular weight, moderate density gas for which the thermodynamic properties are well known; and helium, a low molecular weight, lowdensity gas that is used as a basis for comparison with the behavior of the heavier gases and as an analog of steam, the gas that dominates many volcanic eruptions. Transient jets erupt from the reservoir into the laboratory upon rupture of a thin diaphragm at the exit of a convergent nozzle. The gas accelerates from rest in the reservoir to high velocity in the jet. Reservoir pressures and geometries are such that the fluid velocity in the jets is initially supersonic and later decays to subsonic. The measured reservoir pressure decreases as the fluid expands through repetitively reflecting rarefaction waves, but for the conditions of these experiments, a simple steady-discharge model is sufficient to explain the pressure decay and to predict the duration of the flow. Density variations in the flow field have been visualized with schlieren and shadowgraph photography. The observed structure of the jet is correlated with the measured pressure history. The starting vortex generated when the diaphragm ruptures becomes the head of the jet. Though the exit velocity is sonic, the flow head in the helium jet decelerates to about one-third of sonic velocity in the first few nozzle diameters, the nitrogen head decelerates to about three-fourths of sonic velocity, while Freon maintains nearly sonic velocity. The impulsive acceleration of reservoir fluid into the surrounding atmosphere

  12. Volcanically Active Regions on Io

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Shown here is a portion of one of the highest-resolution images of Io (Latitude: +10 to +60 degrees, Longitude: 180 to 225 degrees) acquired by the Galileo spacecraft, revealing immense lava flows and other volcanic landforms. Several high-temperature volcanic hot spots have been detected in this region by both the Near Infrared Mapping Spectrometer and the imaging system of Galileo. The temperatures are consistent with active silicate volcanism in lava flows or lava lakes (which reside inside irregular depressions called calderas). The large dark lava flow in the upper left region of the image is more than 400 km long, similar to ancient flood basalts on Earth and mare lavas on the Moon.

    North is to the top of the picture and the sun illuminates the surface from the left. The image covers an area 1230 kilometers wide and the smallest features that can be discerned are 2.5 kilometers in size. This image was taken on November 6th, 1996, at a range of 245,719 kilometers by the Solid State Imaging (CCD) system on the Galileo Spacecraft.

    Launched in October 1989, Galileo entered orbit around Jupiter on December 7, 1995. The spacecraft's mission is to conduct detailed studies of the giant planet, its largest moons and the Jovian magnetic environment. The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the Galileo mission home page on the World Wide Web at http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  13. Thermal vesiculation during volcanic eruptions

    NASA Astrophysics Data System (ADS)

    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

    2015-12-01

    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

  14. Thermal vesiculation during volcanic eruptions.

    PubMed

    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

  15. Sub-glacial volcanic eruptions

    USGS Publications Warehouse

    White, Donald Edward

    1956-01-01

    The literature on sub-glacial volcanic eruptions and the related flood phenomena has been reviewed as a minor part of the larger problem of convective and conductive heat transfer from intrusive magma. (See Lovering, 1955, for a review of the extensive literature on this subject.) This summary of data on sub-glacial eruptions is part of a program that the U.S. Geological Survey is conducting in connection with its Investigations of Geologic Processes project on behalf of the Division of Research, U.S. Atomic Energy Commission.

  16. Continuous Hardening During Isothermal Aging at 723 K (450 °C) of a Precipitation Hardening Stainless Steel

    NASA Astrophysics Data System (ADS)

    Celada-Casero, Carola; Chao, Jesús; Urones-Garrote, Esteban; San Martin, David

    2016-06-01

    The isothermal aging behavior of a cold-rolled precipitation hardening stainless steel has been studied at 723 K (450 °C) for holding times up to 72 hours. The precipitation hardening has been investigated using microhardness Vickers (Hv), thermoelectric power (TEP) measurements, and tensile testing. Microhardness compared to TEP measurements is more sensitive to detect the initial stages of aging. Two precipitation regimes have been observed: the first one related to the formation of Cu-clusters for aging times below 1 hour and a second one associated with formation of Ni-rich precipitates. The results show that the material exhibits an outstanding continuous age strengthening response over the aging time investigated, reaching a hardness of 710 ± 4 HV1 and an ultimate tensile strength (σ UTS) of 2.65 ± 0.02 GPa after 72 hours. Engineering stress-plastic strain curves reveal that the strength increases and the ductility decreases as the aging time increases. However, after prolonged holding times (24-72 hours) and, although small, a rise in both the strength and the total elongation is observed. The precipitation kinetics can be well predicted over the entire range of aging times by the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. Finally, a reliable linear hardness-yield strength correlation has been found, which enables a rapid evaluation of the strength from bulk hardness measurements.

  17. Chemical transport during formation and alteration of Martian impact and volcanic deposits

    NASA Technical Reports Server (NTRS)

    Newsom, H. E.

    1992-01-01

    Much of the surface of Mars, including volcanic and cratered terrains, probably experienced alteration and degassing processes. These processes may have depleted or enriched many important elements in surface materials, including bedrock, dust, and soils. The composition of the martian soil may represent the best estimate, for some elements, of the average composition of the martian crust, similar to the composition of loess created by glacial action on the Earth. The martian soil may represent the only convenient, globally or regionally averaged sample of the martian crust. In order to understand the composition of the source material for the soil, however, we need to understand the contributions of volcanic vs. impact sources for this material and the chemical fractionations involved in its production. The processes to be addressed include degassing of volcanic deposits, as observed in the Valley of Ten Thousand Smokes at Katmai, Alaska, and degassing of meltbearing impact ejecta as inferred for suevite ejecta sheets at the Ries Crater, and alteration or palagonitization of volcanic deposits, as documented for volcanos in British Columbia and many other volcanic terrains, and impact crater deposits. The process of palagonitization has been the subject of several studies with reference to Mars, and palagonite is a good analogue for the spectroscopic properties of the martian dust. The role of impact in cratering has not been as well studied, although other researchers have established that both degassing and alteration are common features of impact crater deposits. Other relevant sources of experimental data include the extensive literature on the corrosion of nuclear waste glass and leaching of shocked materials.

  18. Volcanism and associated hazards: the Andean perspective

    NASA Astrophysics Data System (ADS)

    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 (<0.05 km3) in 1985 of Nevado del Ruiz (Colombia) killed about 25 000 people - the worst volcanic disaster in the Andean region as well as the second worst in the world in the 20th century. The Ruiz tragedy has been attributed largely to ineffective communications of hazards information and indecisiveness by government officials, rather than any major deficiencies in scientific data. Ruiz's disastrous outcome, however, together with responses to subsequent hazardous eruptions in Chile, Colombia, Ecuador, and

  19. Experimental study of self-compacted concrete in hardened state

    NASA Astrophysics Data System (ADS)

    Parra Costa, Carlos Jose

    The main aim of this work is to investigate the hardened behaviour of Self-Compacting Concrete (SCC). Self compacting Concrete is a special concrete that can flow in its gravity and fill in the formwork alone to its self-weight, passing through the bars and congested sections without the need of any internal or external vibration, while maintaining adequate homogeneity. SCC avoids most of the materials defects due to bleeding or segregation. With regard to its composition, SCC consists of the same components as traditional vibrated concrete (TC), but in different proportions. Thus, the high amount of superplasticizer and high powder content have to taken into account. The high workability of SCC does not allow to use traditional methods for measuring the fresh state properties, so new tests has developed (slump-flow, V-funnel, L-box, and others). The properties of the hardened SCC, which depend on the mix design, should be different from traditional concrete. In order to study the possible modifications of SCC hardened state properties, a review of the bibliography was done. The state of art was focused on the mechanical behaviour (compressive strength, tension strength and elastic modulus), on bond strength of reinforcement steel, and on material durability. The experimental program consisted in the production of two types of concretes: Self-Compacting Concrete and Traditional Concrete. Four different dosages was made with three different water/cement ratio and two strength types of Portland cement, in order to cover the ordinary strength used in construction. Based on this study it can be concluded that compressive strength of SCC and TC are similar (the differences are lesser than 10%), whereas the tensile strength of TC are up to 18% higher. The values of elastic modulus of both concrete are similar. On the other hand, in the ultimate state the bond strength of SCC and TC is similar, although SCC shows higher bond stiffness in the serviceability state (initial

  20. Automatic semi-continuous accumulation chamber for diffuse gas emissions monitoring in volcanic and non-volcanic areas

    NASA Astrophysics Data System (ADS)

    Lelli, Matteo; Raco, Brunella; Norelli, Francesco; Virgili, Giorgio; Continanza, Davide

    2016-04-01

    Since various decades the accumulation chamber method is intensively used in monitoring activities of diffuse gas emissions in volcanic areas. Although some improvements have been performed in terms of sensitivity and reproducibility of the detectors, the equipment used for measurement of gas emissions temporal variation usually requires expensive and bulky equipment. The unit described in this work is a low cost, easy to install-and-manage instrument that will make possible the creation of low-cost monitoring networks. The Non-Dispersive Infrared detector used has a concentration range of 0-5% CO2, but the substitution with other detector (range 0-5000 ppm) is possible and very easy. Power supply unit has a 12V, 7Ah battery, which is recharged by a 35W solar panel (equipped with charge regulator). The control unit contains a custom programmed CPU and the remote transmission is assured by a GPRS modem. The chamber is activated by DataLogger unit, using a linear actuator between the closed position (sampling) and closed position (idle). A probe for the measure of soil temperature, soil electrical conductivity, soil volumetric water content, air pressure and air temperature is assembled on the device, which is already arranged for the connection of others external sensors, including an automatic weather station. The automatic station has been tested on the field at Lipari island (Sicily, Italy) during a period of three months, performing CO2 flux measurement (and also weather parameters), each 1 hour. The possibility to measure in semi-continuous mode, and at the same time, the gas fluxes from soil and many external parameters, helps the time series analysis aimed to the identification of gas flux anomalies due to variations in deep system (e.g. onset of volcanic crises) from those triggered by external conditions.

  1. GOSAT/TANSO-FTS Measurement of Volcanic and Geothermal CO2 Emissions

    NASA Astrophysics Data System (ADS)

    Schwandner, Florian M.; Carn, Simon A.; Newhall, Christopher G.

    2010-05-01

    Approximately one tenth of the Earth's human population lives in direct reach of volcanic hazards. Being able to provide sufficiently early and scientifically sound warning is a key to volcanic hazard mitigation. Quantitative time-series monitoring of volcanic CO2 emissions will likely play a key role in such early warning activities in the future. Impending volcanic eruptions or any potentially disastrous activity that involves movement of magma in the subsurface, is often preceded by an early increase of CO2 emissions. Conventionally, volcanic CO2 monitoring is done either in campaigns of soil emission measurements (grid of one-time measuring points) that are labor intensive and slow, or by ground-based remote FTIR measurements in emission plumes. These methods are not easily available at all sites of potential activity and prohibitively costly to employ on a large number of volcanoes. In addition, both of these ground-based approaches pose a significant risk to the workers conducting these measurements. Some aircraft-based measurements have been conducted as well in the past, however these are limited by the usually meager funding situation of individual observatories, the hazard such flights pose to equipment and crew, and by the inaccessibility of parts of the plume due to ash hazards. The core motivation for this study is therefore to develop a method for volcanic CO2 monitoring from space that will provide sufficient coverage, resolution, and data quality for an application to quantitative time series monitoring and correlation with other available datasets, from a safe distance and with potentially global reach. In summary, the purpose of the proposed research is to quantify volcanic CO2 emissions using satellite-borne observations. Quantitative estimates will be useful for warning of impending volcanic eruptions, and assessing the contribution of volcanic CO2 to global GHG. Our approach encompasses method development and testing for the detection of

  2. Corrosion in volcanic hot springs

    SciTech Connect

    Lichti, K.A.; Swann, S.J.; Sanada, N.

    1997-12-31

    Volcanic hot pool environments on White Island, New Zealand have been used to study the corrosion properties of materials which might be used for engineering plant for energy production from deep-seated and magma-ambient geothermal systems. The corrosion chemistry of hot pools encountered in natural volcanic features varies, from being of near neutral pH- or alkalie pH-chloride type waters to acidic-chloride/sulfate waters which are more aggressive to metals and alloys. Potential-pH (Pourbaix) diagram models of corrosion product phase stability for common alloy elements contained in engineering alloys have been developed for hot pool environments using thermodynamic principles and conventional corrosion theory. These diagramatic models give reasons for the observed corrosion kinetics and can be used to help to predict the performance of other alloys in similar environments. Deficiencies in the knowledge base for selection of materials for aggressive geothermal environments are identified, and directions for future research on materials having suitable corrosion resistance for deep-seated and magma-ambient production fluids which have acidic properties are proposed.

  3. Volcanic eruptions; energy and size

    USGS Publications Warehouse

    de la Cruz-Reyna, S.

    1991-01-01

    The Earth is a dynamic planet. Many different processes are continuously developing, creating a delicate balance between the energy stored and generated in its interior and the heat lost into space. The heat in continuously transferred through complex self-regulating convection mechanisms on a planetary scale. The distribution of terrestrial heat flow reveals some of the fine structure of the energy transport mechanisms in the outer layers of the Earth. Of these mechanisms in the outer layers of the Earth. Of these mechanisms, volcanism is indeed the most remarkable, for it allows energy to be transported in rapid bursts to the surface. In order to maintain the subtle balance of the terrestrial heat machine, one may expect that some law or principle restricts the ways in which these volcanic bursts affect the overall energy transfer of the Earth. For instance, we know that the geothermal flux of the planet amounts to 1028 erg/year. On the other hand, a single large event like the Lava Creek Tuff eruption that formed Yellowstone caldera over half a million years ago may release the same amount of energy in a very small area, over a short period of time. 

  4. Some new results on irradiation characteristics of synthetic quartz crystals and their application to radiation hardening

    NASA Technical Reports Server (NTRS)

    Bahadur, H.; Parshad, R.

    1983-01-01

    The paper reports some new results on irradiation characteristics of synthetic quartz crystals and their application to radiation hardening. The present results show how the frequency shift in quartz crystals can be influenced by heat processing prior to irradiation and how this procedure can lead to radiation hardening for obtaining precise frequencies and time intervals from quartz oscillators in space.

  5. Strain hardening during mechanical twining and dislocation channeling in irradiated 316 stainless steels

    SciTech Connect

    Byun, Thak Sang; Hashimoto, Naoyuki

    2007-01-01

    Localized deformation mechanisms and strain-hardening behaviors in irradiated 316 and 316LN stainless steels were investigated, and a theoretical model was proposed to explain the linear strain-hardening behavior during the localized deformation. After low temperature irradiation to significant doses the deformation microstructure changed from dislocation tangles to channels or to mechanical twins. It was also observed that irradiation hardening straightened gliding dislocations and increased the tendency for forming pileups. Regardless of these microstructural changes, the strain-hardening behavior was relatively insensitive to the irradiation. This dose-independent strain-hardening rate resulted in dose independence of the true stress parameters such as the plastic instability stress and true fracture stress. In the proposed model, the long-range back stress was formulated as a function of the number of pileup dislocations per slip band and the number of slip bands in a grain. The calculation results confirmed the experimental observation that strain-hardening rate was insensitive to the change in deformation mechanism because the long-range back stress hardening became as high as the hardening by tangled dislocations.

  6. The Effect of Hardenability Variation on Phase Transformation of Spiral Bevel Gear in Quenching Process

    NASA Astrophysics Data System (ADS)

    Zhang, Yingtao; Shi, Wankai; Yang, Lin; Gu, Zhifei; Li, Zhichao

    2016-05-01

    The hardenability of gear steel is dependent on the composition of alloying elements and is one of important criteria to assess process of phase transformation. The variation of hardenability has to be considered in control of the microstructures and distortion during gear quenching. In this paper, the quantitative effect of hardenability has been investigated on phase transformations of spiral bevel gears in die quenching. The hardenability deviation of 22CrMoH steel was assessed by using Jominy test. The dilatometry experiments were conducted to build phase transformation kinetic models for steels with low and high hardenability, respectively. The complete die quenching process of spiral bevel gear was modeled to reveal the significant difference on microstructures and temperature history with variation of hardenability. The final microstructures of the gear are martensite in surface layer after quenching process. There are bainite inside the gear tooth and the mixture of bainite and ferrite inside gear for the gear with low hardenability. The microstructure is bainite inside the gear with high hardenability.

  7. Consistency condition for isotropic-kinematic hardening of anisotropic yield functions

    NASA Astrophysics Data System (ADS)

    Chung, Kwansoo

    2013-05-01

    For the combined type isotropic-kinematic hardening law to account for the Bauschinger, transient and permanent softening behaviors observed in reverse loading, formulations have been initially developed for isotropic yield functions, mainly based on the von Mises criterion, and then later extended for anisotropic yield functions. Among the efforts to introduce anisotropic yield functions to the combined type hardening formulation, however, some inconsistency has been encountered in manipulating the kinematic hardening law, especially for the nonlinear type law, even though their von Mises yield function versions have been consistent. Therefore, theoretical clarification and clearance of such inconsistency were attempted in this work by imposing the following (consistency) condition: the combined type hardening law is expected to behave the same as the full isotropic hardening for monotonously proportional loading, regardless of (anisotropic) yield functions coupled with the combined type hardening law. An example to account for the anisotropic hardening of an anisotropic yield function utilizing the combined type hardening law, but for which the consistency condition was partially released, was also demonstrated.

  8. The Effect of Hardenability Variation on Phase Transformation of Spiral Bevel Gear in Quenching Process

    NASA Astrophysics Data System (ADS)

    Zhang, Yingtao; Shi, Wankai; Yang, Lin; Gu, Zhifei; Li, Zhichao

    2016-07-01

    The hardenability of gear steel is dependent on the composition of alloying elements and is one of important criteria to assess process of phase transformation. The variation of hardenability has to be considered in control of the microstructures and distortion during gear quenching. In this paper, the quantitative effect of hardenability has been investigated on phase transformations of spiral bevel gears in die quenching. The hardenability deviation of 22CrMoH steel was assessed by using Jominy test. The dilatometry experiments were conducted to build phase transformation kinetic models for steels with low and high hardenability, respectively. The complete die quenching process of spiral bevel gear was modeled to reveal the significant difference on microstructures and temperature history with variation of hardenability. The final microstructures of the gear are martensite in surface layer after quenching process. There are bainite inside the gear tooth and the mixture of bainite and ferrite inside gear for the gear with low hardenability. The microstructure is bainite inside the gear with high hardenability.

  9. New distortional hardening model capable of predicting eight ears for textured aluminum sheet

    SciTech Connect

    Yoon, J. H.; Cazacu, O.; Yoon, J. W.; Dick, R. E.

    2011-05-04

    The effects of the anisotropy evolution and of the directionality in hardening on the predictions of the earing profile of a strongly textured aluminum alloy are investigated using a new distortional hardening model that incorporates multiple hardening curves corresponding to uniaxial tension along several orientations with respect to the rolling direction, and to biaxial tension. Yielding is described using a form of CPB06ex2 yield function (Plunkett et al. (2008)) which is tailored for metals with no tension-compression asymmetry. It is shown that even if directional hardening and its evolution are neglected, this yield function predicts a cup with eight ears as was observed experimentally. However, directional hardening can be of considerable importance for improved accuracy in prediction of the non-uniformity of the cup height profile.

  10. Evaluation of Springback for DP980 S Rail Using Anisotropic Hardening Models

    NASA Astrophysics Data System (ADS)

    Choi, Jisik; Lee, Jinwoo; Bae, Gihyun; Barlat, Frederic; Lee, Myoung-Gyu

    2016-07-01

    The effect of anisotropic hardening models on springback of an S-rail part was investigated. Two advanced constitutive models based on distortional and kinematic hardening, which captured the Bauschinger effect, transient hardening, and permanent softening during strain path change, were implemented in a finite element (FE) code. In-plane compression-tension tests were performed to identify the model parameters. The springback of the S-rail after forming a 980 MPa dual-phase steel sheet sample was measured and analyzed using different hardening models. The comparison between experimental and FE results demonstrated that the advanced anisotropic hardening models, which are particularly suitable for non-proportional loading, significantly improved the springback prediction capability of an advanced high strength steel.

  11. A radiation-hardened 16/32-bit microprocessor

    SciTech Connect

    Hass, K.J.; Treece, R.K.; Giddings, A.E. )

    1989-12-01

    This paper reports on the development of single chip radiation-hardened 16/32-bit microprocessor. This device, the SA3300, is an emulation of National Semiconductor's NS32C016. The SA3300 is designed to withstand high levels of ionizing radiation and is resistant to single event upset (SEU) caused by heavy ions. New techniques were used to improve immunity to SEU effects in combinational logic. The authors' testing has demonstrated that the SA3300 is functional after a total gamma dose of 5 Mrad(Si). The device does not latch up from SEU, and parts without SEU resistors have an SEU linear energy transfer (LET) upset threshold greater than 28 MeV/mg/cm{sup 2}.

  12. Method of forming a hardened surface on a substrate

    DOEpatents

    Branagan, Daniel J.

    2010-08-31

    The invention includes a method of producing a hard metallic material by forming a mixture containing at least 55% iron and at least one of B, C, Si and P. The mixture is formed into an alloy and cooled to form a metallic material having a hardness of greater than about 9.2 GPa. The invention includes a method of forming a wire by combining a metal strip and a powder. The metal strip and the powder are rolled to form a wire containing at least 55% iron and from two to seven additional elements including at least one of C, Si and B. The invention also includes a method of forming a hardened surface on a substrate by processing a solid mass to form a powder, applying the powder to a surface to form a layer containing metallic glass, and converting the glass to a crystalline material having a nanocrystalline grain size.

  13. Hydrogen effects on the age hardening behavior of 2024 aluminum

    NASA Technical Reports Server (NTRS)

    Wagner, J. A.; Louthan, M. R., Jr.; Sisson, R. D., Jr.

    1986-01-01

    It has been found that the fatigue crack growth rate in aluminum alloys increases significantly in the presence of moisture. This phenomenon along with a moisture effect observed in another context has been attributed to 'embrittlement' of the aluminum by absorbed hydrogen generated by the reaction of moisture with freshly exposed aluminum. A description is given of a number of age hardening experiments involving 2024 aluminum. These experiments show that a mechanism related to the segregation of absorbed hydrogen to the coherent theta-double-prime interfaces may account for the observed reduction in fatigue life. It is pointed out that this segregation promotes a loss of coherency in the hydrogen rich region at a fatigue crack tip. Subsequently, the loss of coherency causes local softening and reduces fatigue life.

  14. Modelling of temperature evolution on metals during laser hardening process

    NASA Astrophysics Data System (ADS)

    Yánez, A.; Álvarez, J. C.; López, A. J.; Nicolás, G.; Pérez, J. A.; Ramil, A.; Saavedra, E.

    2002-01-01

    To achieve a precise and controlled laser process, an exhaustive analysis of the thermal behaviour of the material is necessary. In the present paper, a numerical simulation of the laser hardening process has been developed using both analytical solutions and the finite element code ANSYS™ to solve the heat transfer equation inside the treated material. The knowledge of the thermal cycles has enabled suitable processing parameters to be ascertained thus improving surface properties when metallic alloys have been irradiated. A simpler analytical method is also used to determine the mentioned parameters more quickly. This general purpose method has been applied to a specific experimental situation, namely the treatment of cylindrical pieces used in a multistage pump rotary jacket.

  15. Dislocation mean free paths and strain hardening of crystals.

    PubMed

    Devincre, B; Hoc, T; Kubin, L

    2008-06-27

    Predicting the strain hardening properties of crystals constitutes a long-standing challenge for dislocation theory. The main difficulty resides in the integration of dislocation processes through a wide range of time and length scales, up to macroscopic dimensions. In the present multiscale approach, dislocation dynamics simulations are used to establish a dislocation-based continuum model incorporating discrete and intermittent aspects of plastic flow. This is performed through the modeling of a key quantity, the mean free path of dislocations. The model is then integrated at the scale of bulk crystals, which allows for the detailed reproduction of the complex deformation curves of face-centered cubic crystals. Because of its predictive ability, the proposed framework has a large potential for further applications. PMID:18583605

  16. Theoretical Study of the Oxidation Behavior of Precipitation Hardening Steel

    SciTech Connect

    Pistofidis, N.; Vourlias, G.; Chrissafis, K.; Psyllaki, P.

    2010-01-21

    The oxidation of precipitation hardening (PH) steels is a rather unexplored area. In the present work an attempt is made is made to estimate the kinetics of a PH steel. For this purpose specimens of the material under examination were isothermally heated at 850, 900 and 950 deg. C for 15 hr. Kinetics was based on TGA results. During heating a thick scale is formed on the substrate surface, which is composed by different oxides. The layer close to the substrate is compact and as a result it impedes corrosion. The mathematical analysis of the collected data shows that the change of the mass of the substrate per unit area versus time is described by a parabolic law.

  17. Topographies of plasma-hardened surfaces of poly(dimethylsiloxane)

    SciTech Connect

    Goerrn, Patrick; Wagner, Sigurd

    2010-11-15

    We studied the formation of surface layers hardened by plasma-enhanced oxidation of the silicone elastomer poly(dimethylsiloxane). We explored the largest parameter space surveyed to date. The surface layers may wrinkle, crack, or both, under conditions that at times are controlled by design, but more often have been discovered by trial-and-error. We find four distinct topographies: flat/wrinkled/cracked/cracked and wrinkled. Each topography is clearly separated in the space of plasma dose versus plasma pressure. We analyzed wrinkle amplitude and wavelength by atomic force microscopy in the tapping mode. From these dimensions we calculated the elastic modulus and thickness of the hard surface layer, and inferred a graded hardness, by employing a modified theoretical model. Our main result is the identification of the parameters under which the technologically important pure wrinkled, crack-free topography is obtained.

  18. Gamma prime hardened nickel-iron based superalloy

    DOEpatents

    Korenko, Michael K.

    1978-01-01

    A low swelling, gamma prime hardened nickel-iron base superalloy useful for fast reactor duct and cladding applications is described having from about 7.0 to about 10.5 weight percent (wt%) chromium, from about 24 to about 35 wt% nickel, from about 1.7 to about 2.5 wt% titanium, from about 0.3 to about 1.0 wt% aluminum, from about 2.0 to about 3.3 wt% molybdenum, from about 0.05 to about 1.0 wt% silicon, from about 0.03 to about 0.06 wt% carbon, a maximum of about 2 wt% manganese, and the balance iron.

  19. A phenomenological model for bake hardening in minimal carbon steels

    NASA Astrophysics Data System (ADS)

    Das, Sourav; Nath Mohanty, Omkar; Brat Singh, Shiv

    2014-06-01

    The essence of bake hardening is to exploit the classical strain ageing in a positive way to increase the strength of the formed steel sheets used in outer body panel of a passenger car during the paint-baking operation. A new model that takes into account the strengthening contributions from Cottrell atmosphere and precipitate formation has been developed in the present work. The model predicts the increase in strength as a function of the amount of free solute C (calculated as a function of the annealing temperature), the amount of deformation, ageing temperature and time. The model predictions have been found to agree quite well with the experimental results; the individual contributions of Cottrell atmosphere and precipitation strengthening have been quantified.

  20. Analysis of fracture toughness of explosion-hardened martensitic steel

    NASA Astrophysics Data System (ADS)

    Moskvitina, L. V.

    2015-10-01

    In this work we study a shift of the following nonlinear states: tempering + abatement + 10 GPa shock loading + welding thermocycle. As a result the self-organized HAZ metal structure with elements of self-similarity on different scales is found. The fractal analysis shows how formed defects affect the HAZ metal hardness of 14H2GMR steel with the martensitic structure of static fracture. The statistical analysis of stereometric parameters of fracture shows a higher energy intensity of static fracture in specimens treated by explosion. The multifractal analysis reveals hardness of the grid dislocation structure induced by explosion in the air-hardening zone. The homogeneity of the dislocation structure related to carbides increases the resistance of HAZ metal of static fracture.

  1. Optical moments and the art of dispersion hardening

    NASA Astrophysics Data System (ADS)

    Sievers, A. J.; Noh, T. W.; Page, J. B.

    1994-06-01

    For many years composite structures have been the building blocks of materials with specialized mechanical properties, but only recently have related ideas been used successfully to develop new optical materials. A particularly simple example, hot pressed zinc sulfide dispersion hardened with diamond particles, has turned out to be extremely useful for identifying the important optical moments underlying the dynamical properties of all transparent composites and complex dielectrics. One result has been the discovery of a generalized Lyddane-Sachs-Teller relation for solids and liquids. When the characteristic frequencies of small disordered dielectric particles are described in terms of optical moments of the appropriate response functions, generalized Szigeti and Clausius-Mossotti expressions follow.

  2. Effective mineral coatings for hardening the surface of metallic materials

    NASA Astrophysics Data System (ADS)

    Kislov, S. V.; Kislov, V. G.; Skazochkin, A. V.; Bondarenko, G. G.; Tikhonov, A. N.

    2015-07-01

    The structural changes that occur in the surface and surface layers of steel 20Kh13 and titanium alloy PT-3V (Russian designation) samples after each stage of hardening due to a formed mineral surface layer are studied by optical microscopy, transmission electron microscopy, and scanning electron microscopy. Electric spark alloying, pressing, and ultrasonic processing are used to reach the effect of volume compression of the base metal and the mineral in the plastic deformation zone. As a result, applied mineral particles concentrate in preliminarily created microvoids in a thin surface layer. The surface layer thus modified acquires a high hardness and wear resistance. Durometry shows that the hardness of the processed sample surfaces increases more than twofold. Therefore, the developed technology of creating a mineral coating can be used to increase the tribological properties of the surfaces of the parts, units, and mechanisms of turbine, pump, and mining equipment, which undergo intense wear during operation.

  3. Large Scale Impacts and Triggered Volcanism

    NASA Technical Reports Server (NTRS)

    Ivanov, B. A.; Melosh, H. J.

    2003-01-01

    The idea of impact induced volcanism continues to blossom ([1-3] and other references). However, this appealing idea is seldom supported with an appropriate physical mechanism. The aim of this publication is to critically examine some frequently cited mechanisms of impact energy transformation into a trigger for terrestrial volcanism and magmatism.

  4. [Hardened anodized aluminum as a replacement material for bracket manufacture].

    PubMed

    Fischer-Brandies, H; Bönhoff, M

    1994-12-01

    Attention has been repeatedly drawn to the problem of corrosion and the risk of allergic reaction to nickel resulting from the use of stainless steel brackets. In the search for a suitable alternative, manufacturers have turned to thin coating technology using hardened anodized aluminium. Applying resistance to corrosion and abrasion as the criteria to be met, they have selected aluminium alloy type 6082 as the material of choice. Purpose of this study is to examine the physical suitability of this material. Using the above noted alloy, 60 prototype brackets were made with a hardened anodized surface. They were then subjected to the following 3 stress tests: first an abrasion test using a tooth polishing machine, second, a deformation test using a device designed to simulate torque movement, and, third, a corrosion test. The effects on the brackets resulting from the three types of stress were evaluated by light microscopy. A quantitative analysis of the corrosion test was performed by ICP spectrometry. The control group consisted of conventional stainless steel brackets. The light microscopic analysis revealed no evidence of surface damage or signs of deformation in the prototype brackets. The steel brackets, on the other hand, showed clear signs of wear and corrosion. The quantitative analysis of the corrosion solution revealed metallic ion wear of 1.75 ng x mm-2 x h-1 for the prototypes subjected to abrasion. The steel brackets showed at a factor of around 104.6 metallic ion wear of 183 ng x mm-2 x h-1. In addition to this, no Ni ions were found in the corrosion solution of the prototype brackets.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7851828

  5. Radiation Effects and Hardening Techniques for Spacecraft Microelectronics

    NASA Astrophysics Data System (ADS)

    Gambles, J. W.; Maki, G. K.

    2002-01-01

    The natural radiation from the Van Allen belts, solar flares, and cosmic rays found outside of the protection of the earth's atmosphere can produce deleterious effects on microelectronics used in space systems. Historically civil space agencies and the commercial satellite industry have been able to utilize components produced in special radiation hardened fabrication process foundries that were developed during the 1970s and 1980s under sponsorship of the Departments of Defense (DoD) and Energy (DoE). In the post--cold war world the DoD and DoE push to advance the rad--hard processes has waned. Today the available rad--hard components lag two-plus technology node generations behind state- of-the-art commercial technologies. As a result space craft designers face a large performance gap when trying to utilize available rad--hard components. Compounding the performance gap problems, rad--hard components are becoming increasingly harder to get. Faced with the economic pitfalls associated with low demand versus the ever increasing investment required for integrated circuit manufacturing equipment most sources of rad--hard parts have simply exited this market in recent years, leaving only two domestic US suppliers of digital rad--hard components. This paper summarizes the radiation induced mechanisms that can cause digital microelectronics to fail in space, techniques that can be applied to mitigate these failure mechanisms, and ground based testing used to validate radiation hardness/tolerance. The radiation hardening techniques can be broken down into two classes, Hardness By Process (HBP) and Hardness By Design (HBD). Fortunately many HBD techniques can be applied to commercial fabrication processes providing space craft designer with radiation tolerant Application Specific Integrated Circuits (ASICs) that can bridge the performance gap between the special HBP foundries and the commercial state-of-the-art performance.

  6. Development of a Press-Hardened Steel Suitable for Thin Slab Direct Rolling Processing

    NASA Astrophysics Data System (ADS)

    Lee, Jewoong; De Cooman, Bruno C.

    2015-01-01

    The thin slab casting and direct rolling process is a hot-rolled strip production method which has maintained commercial quality steel grades as a major material in many industrial applications due to its low processing cost. Few innovative products have however been developed specifically for production by thin slab direct rolling. Press hardening or hot press forming steel grades which are now widely used to produce structural automotive steel parts requiring ultra-high strength and formability may however offer an opportunity for thin slab direct rolling-specific ultra-high strength products. In this work, a newly designed press hardening steel grade developed specifically for thin slab direct rolling processing is presented. The press hardening steel has a high nitrogen content compared with press hardening steel grades produced by conventional steelmaking routes. Boron and titanium which are key alloying additions in conventional press hardening steel such as the 22MnB5 press hardening steel grade are not utilized. Cr is added in the press hardening steel to obtain the required hardenability. The properties of the new thin slab direct rolling-specific 22MnCrN5 press hardening steel grade are reviewed. The evolution of the microstructure and mechanical properties with increasing amounts of Cr additions from 0.6 to 1.4 wt pct and the effect of the cooling rate during die-quenching were studied by means of laboratory simulations. The selection of the optimum chemical composition range for the thin slab direct rolling-specific 22MnCrN5 steel in press hardening heat treatment conditions is discussed.

  7. Potential role of strain hardening in the cessation of rifting at constant tectonic force

    NASA Astrophysics Data System (ADS)

    Yamasaki, Tadashi; Stephenson, Randell

    2009-01-01

    In this study the cessation of rifting at constant tectonic force is discussed from the viewpoint of lithospheric rheology using a simple one-dimensional numerical model. The behaviour of the conventionally adopted constant force model re-examined in this study contradicts some general features in the development of sedimentary basins. Strain hardening is implemented to explain the contradictions, in which the viscosity of the mantle is a function of not only the strain rate and temperature but also the total strain. The roles of various strain hardening parameters in rifting dynamics are examined, including the strain required for the onset of hardening, the strain interval required for the completion of hardening and the factor controlling the increase in mantle viscosity. It is shown that a model with strain hardening can explain many characteristic features of sedimentary basin formation better than the conventional constant force model. There are a variety of ways in which rifting can be terminated by the strain hardening model, depending on the initial lithospheric structure, magnitude of tectonic force and the hardening process. One possible strain hardening mechanism involves the switch from wet to dry rheology associated with decompressional melting, though the implemented strain hardening formula could be generally applicable to any hardening phenomenon and could therefore be physically interpreted as such. The results of this study also provide important insights into sedimentary basin subsidence in relation to rifting dynamics. The end of an initial rapid ("syn-rift" like) subsidence phase is not necessarily equivalent to the end of actual rifting as in the constant force model. The transition from initial rapid subsidence to long-term, more subdued ("post-rift" like), subsidence is actually marked by the onset of deceleration of rifting. Since significant extension still continues for some time thereafter, the subsequent long-term subsidence includes

  8. Lakshmi Planum: A distinctive highland volcanic province

    NASA Technical Reports Server (NTRS)

    Roberts, Kari M.; Head, James W.

    1989-01-01

    Lakshmi Planum, a broad smooth plain located in western Ishtar Terra and containing two large oval depressions (Colette and Sacajawea), has been interpreted as a highland plain of volcanic origin. Lakshmi is situated 3 to 5 km above the mean planetary radius and is surrounded on all sides by bands of mountains interpreted to be of compressional tectonic origin. Four primary characteristics distinguish Lakshmi from other volcanic regions known on the planet, such as Beta Regio: (1) high altitude, (2) plateau-like nature, (3) the presence of very large, low volcanic constructs with distinctive central calderas, and (4) its compressional tectonic surroundings. Building on the previous work of Pronin, the objective is to establish the detailed nature of the volcanic deposits on Lakshmi, interpret eruption styles and conditions, sketch out an eruption history, and determine the relationship between volcanism and the tectonic environment of the region.

  9. Hydrogeology of the Azores volcanic archipelago (Portugal)

    NASA Astrophysics Data System (ADS)

    Cruz, J.; Coutinho, R.; Antunes, P.; Freire, P.

    2009-04-01

    The archipelago of the Azores is made of nine islands of volcanic origin located in the North Atlantic Ocean, with an area of 2333 km2 and approximately 237500 inhabitants, which are 98% dependant from groundwater sources for their water consumption. Therefore, groundwater is a resource that plays a vital role as drinking water source and as ecosystem support matrix. Nevertheless, besides the environmental, social and economical value of groundwater, this resource is subject to an increase pressure and in several islands water quality deterioration is shown by monitoring data. This pressure is also shown by the 42.7% increase expected for domestic use until the year 2020 at the Azores, with higher groundwater abstraction. The Azores climate can be considered as marine temperate, which is reflected by the low thermal amplitude and high precipitation. A well-established difference between a dry season and a colder and wet season occurs, as from October to March about 75% of the annual precipitation is registered. The average annual precipitation at the Azores is 1930 mm, exceeding by far the average annual actual evapotranspiration, which is 581 mm. Recharge rates range from 8.5% to 62.1%, and the highest values are observed at Pico, Terceira, Faial, São Miguel and Graciosa islands, especially in areas where the terrain is covered by recent basaltic lava flows and the soil cover is sparse. Groundwater resources estimates point to a total volume of about 1600x106 m3/yr. Values above the recharge median, equal to 101.3x106 m3/yr. were estimated for the São Miguel, São Jorge, Terceira and Flores islands. Despite differences in the islands growth, as a result of successive volcanic eruptions of various types, groundwater occurrence can be described in function of two main aquifers systems: (1) the basal aquifer system, which corresponds to fresh-water lenses floating on underlying salt water, and (2) perched-water bodies, which are usually drained by springs spread in

  10. A preliminary evaluation of ERTS-1 images on the volcanic areas of Southern Italy

    NASA Technical Reports Server (NTRS)

    Cassinis, R.; Lechi, G. M.

    1973-01-01

    The test site selected for the investigation covers nearly all the regions of active and quiescent volcanism in southern Italy, i.e. the eastern part of the island of Sicily, the Aeolian Islands and the area of Naples. The three active European volcanoes (Etna, Stromboli and Vesuvius) are included. The investigation is in the frame of a program for the surveillance of active volcanoes by geophysical (including remote sensing thermal methods) and geochemical methods. By the multispectral analysis of ERTS-1 data it is intended to study the spectral behavior of the volcanic materials as well as the major geological lineaments with special reference to those associated with the volcanic region. Secondary objectives are also the determination of the hydrographic network seasonal behavior and the relationship between the vegetation cover and the different type of soils and rocks.

  11. Sulfate, chloride and fluoride retention in Andosols exposed to volcanic acid emissions.

    PubMed

    Delmelle, Pierre; Delfosse, Thomas; Delvaux, Bruno

    2003-01-01

    The continuous emissions of SO(2), HCl and HF by Masaya volcano, Nicaragua, represent a substantial source of atmospheric S-, Cl- and F-containing acid inputs for local ecosystems. We report on the effects of such acid depositions on the sulfate, chloride and fluoride contents in soils (0-40 cm) from two distinct transects located downwind from the volcano. The first transect corresponds to relatively undifferentiated Vitric Andosols, and the second transect to more weathered Eutric Andosols. These soils are exposed to various rates of volcanogenic acid addition, with the Vitric sites being generally more affected. Prolonged acid inputs have led to a general pH decrease and reduced exchangeable base cation concentrations in the Andosols. The concentrations of 0.5 M NH(4)F- and 0.016 M KH(2)PO(4)-extractable sulfate (NH(4)F-S and KH(2)PO(4)-S, respectively) indicate that volcanic S addition has increased the inorganic sulfate content of the Vitric and Eutric soils at all depths. In this process, the rate of sulfate accumulation is also dependent on soil allophane contents. For all soils, NH(4)F extracted systematically more (up to 40 times) sulfate than KH(2)PO(4). This difference suggests sulfate incorporation into an aluminum hydroxy sulfate phase, whose contribution to total inorganic sulfate in the Vitric and Eutric Andosols is estimated from approximately 34 to 95% and approximately 65 to 98%, respectively. The distribution of KH(2)PO(4)-extractable chloride in the Vitric and Eutric Andosols exposed to volcanic Cl inputs reveals that added chloride readily migrates through the soil profiles. In contrast, reaction of fluoride with Al and Fe oxyhydroxides and allophanes is an important sink mechanism in the Masaya Andosols exposed to airborne volcanic F. Fluoride dominates the anion distribution in all soil horizons, although F is the least concentrated element in the volcanic emissions and depositions. The soil anion distribution reflects preferential retention

  12. Io Eclipse/Volcanic Eruption

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This image was acquired while Io was in eclipse (in Jupiter's shadow) during Galileo's eighth orbit, and reveals several dynamic processes. The most intense features are red, while glows of lesser intensity are yellow or green, and very faint glows appear blue in this color-coded image. The small red or yellow spots mark the sites of high-temperature magma erupting onto the surface in lava flows or lava lakes.

    This image reveals a field of bright spots near Io's sub-Jupiter point (right-hand side of image). The sub-Jupiter hemisphere always faces Jupiter just as the Moon's nearside always faces Earth. There are extended diffuse glows on the equatorial limbs or edges of the planet (right and left sides). The glow on the left is over the active volcanic plume Prometheus, but whereas Prometheus appears to be 75 kilometers (46.6 miles) high in reflected light, here the diffuse glow extends about 800 kilometers (497 miles) from Io's limb. This extended glow indicates that gas or small particles reach much greater heights than the dense inner plume. The diffuse glow on the right side reaches a height of 400 kilometers (249 miles), and includes a prominence with a plume-like shape. However, no volcanic plume has been seen at this location in reflected light. This type of observation is revealing the relationships between Io's volcanism, atmosphere and exosphere.

    Taken on May 6, 1997, north is toward the top. The image was taken with the clear filter of the solid state imaging (CCD) system on NASA's Galileo spacecraft at a range of 1.8 million kilometers (1.1 million miles).

    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

  13. Large Volcanic Rises on Venus

    NASA Technical Reports Server (NTRS)

    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

  14. Frictional processes in volcanic conduits

    NASA Astrophysics Data System (ADS)

    Lavallee, Y.; Kendrick, J. E.; Petrakova, L.; Mitchell, T. M.; Heap, M. J.; Hirose, T.; Di Toro, G.; Hess, K.; Dingwell, D. B.

    2012-12-01

    The ascent of high-viscosity magma in upper conduits proceeds via the development of shear zones, which commonly fracture, producing fault surfaces that control the last hundreds of meters of ascent by frictional slip. Frictional slip in conduits may occur along magma-rock, rock-rock and magma-magma interfaces, with or without the presence of gouge material. During slip, frictional work is converted to heat, which may result in strong geochemical disequilibria as well as rheological variations, with important consequences on the dynamics of magma ascent. Here, we present a thermo-mechanical study on the ability of volcanic rocks (with different proportions of interstitial glass, crystals and vesicles) to sustain friction, and in some cases to melt, using a high-velocity rotary apparatus. The friction experiments were conducted at a range of slip velocities (1.3 mm/s to 1.3 m/s) along a (fault) plane subjected to different normal stresses (0.5-10 MPa). We observe that the behaviour of volcanic rocks during slip events varies remarkably. Frictional slip along dense crystal-rich rocks is characterized by the occurrence of comminution, commonly followed by melting. In contrast, slip along dense glass rocks rarely proceeds along a discrete plane - a glass subjected to slip tends to shatter as temperature enters the glass transition interval. Alternatively, glass can be slipped against a crystalline material. In the case of porous material, slip generally results in rapid abrasion of the porous material, producing a high amount of ash particles. The inability of the material to preserve its slip surface inhibits the generation of significant heat. Finally, during experiments in which ash gouge occupies the slip zone, friction generates a modest amount of heat and does not induce significant comminution along the slip plane. Mechanically, the frictional coefficients of the tested volcanic material vary significantly, depending whether the material may sustain slip (and

  15. Assessing volcanic hazards with Vhub

    NASA Astrophysics Data System (ADS)

    Palma, J. L.; Charbonnier, S.; Courtland, L.; Valentine, G.; Connor, C.; Connor, L.

    2012-04-01

    Vhub (online at vhub.org) is a virtual organization and community cyberinfrastructure designed for collaboration in volcanology research, education, and outreach. One of the core objectives of this project is to accelerate the transfer of research tools to organizations and stakeholders charged with volcano hazard and risk mitigation (such as volcano observatories). Vhub offers a clearinghouse for computational models of volcanic processes and data analysis, documentation of those models, and capabilities for online collaborative groups focused on issues such as code development, configuration management, benchmarking, and validation. Vhub supports computer simulations and numerical modeling at two levels: (1) some models can be executed online via Vhub, without needing to download code and compile on the user's local machine; (2) other models are not available for online execution but for offline use in the user's computer. VHub also has wikis, blogs and group functions around specific topics to encourage collaboration, communication and discussion. Some of the simulation tools currently available to Vhub users are: Energy Cone (rapid delineation of the impact zone by pyroclastic density currents), Tephra2 (tephra dispersion forecast tool), Bent (atmospheric plume analysis), Hazmap (simulate sedimentation of volcanic particles) and TITAN2D (mass flow simulation tool). The list of online simulations available on Vhub is expected to expand considerably as the volcanological community becomes more involved in the project. This presentation focuses on the implementation of online simulation tools, and other Vhub's features, for assessing volcanic hazards following approaches similar to those reported in the literature. Attention is drawn to the minimum computational resources needed by the user to carry out such analyses, and to the tools and media provided to facilitate the effective use of Vhub's infrastructure for hazard and risk assessment. Currently the project

  16. Petrogenetic modeling of 74220 high-Ti orange volcanic glasses and the Apollo 11 and 17 high-Ti mare basalts

    NASA Technical Reports Server (NTRS)

    Hughes, S. S.; Schmitt, R. A.; Delano, J. W.

    1989-01-01

    An INAA analysis of 16 individual spherules of orange volcanic glass extracted from the 74220,680 soil was performed in order to determine trace element signatures in a primary high-Ti mare magma. The composition of these glasses is shown to be nearly identical to that of 74220 bulk soil, indicating a general absence of constituents other than volcanic glass in the soil. The results suggest that the evolving lunar mantle included processes of cumulate-mass transport and/or segregation of the primordial lunar magma ocean into separate differentiating zones, allowing commingling of early and late components.

  17. An atlas of volcanic ash

    NASA Technical Reports Server (NTRS)

    Heiken, G.

    1974-01-01

    Volcanic ash samples collected from a variety of recent eruptions were studied, using petrography, chemical analyses, and scanning electron microscopy to characterize each ash type and to relate ash morphology to magma composition and eruption type. The ashes are best placed into two broad genetic categories: magnetic and hydrovolcanic (phreatomagmatic). Ashes from magmatic eruptions are formed when expanding gases in the magma form a froth that loses its coherence as it approaches the ground surface. During hydrovolcanic eruptions, the magma is chilled on contact with ground or surface waters, resulting in violent steam eruptions. Within these two genetic categories, ashes from different magma types can be characterized. The pigeon hole classification used here is for convenience; there are eruptions which are driven by both phreatic and magmatic gases.

  18. Tradeoffs in Flight Design Upset Mitigation in State of the Art FPGAs: Hardened by Design vs. Design Level Hardening

    NASA Technical Reports Server (NTRS)

    Swift, Gary M.; Roosta, Ramin

    2004-01-01

    This presentation compares and contrasts the effectiveness and the system/designer impacts of the two main approaches to upset hardening: the Actel approach (RTSX-S and RTAX-S) of low-level (inside each flip-flop) triplication and the Xilinx approach (Virtex and Virtex2) of design-level triplication of both functional blocks and voters. The effectiveness of these approaches is compared using measurements made in conjunction with each of the FPGAs' manufacturer: for Actel, published data [1] and for Xilinx, recent results from the Xilinx SEE Test Consortium (note that the author is an active and founding member). The impacts involve Actel advantages in the areas of transistor-utilization efficiency and minimizing designer involvement in the triplication while the Xilinx advantages relate to the ability to custom tailor upset hardness and the flexibility of re-configurability. Additionally, there are currently clear Xilinx advantages in available features such as the number of I/O's, logic cells, and RAM blocks as well as speed. However, the advantage of the Actel anti-fuses for configuration over the Xilinx SRAM cells is that the latter need additional functionality and external circuitry (PROMs and, at least a watchdog timer) for configuration and configuration scrubbing. Further, although effectively mitigated if done correctly, the proton upset-ability of the Xilinx FPGAs is a concern in severe proton-rich environments. Ultimately, both manufacturers' upset hardening is limited by SEFI (single-event functional interrupt) rates where it appears the Actel results are better although the Xilinx Virtex2-family result of about one SEFI in 65 device-years in solar-min GCR (the more intense part of the galactic cosmic-ray background) should be acceptable to most missions

  19. Spatial distribution and alignments of volcanic centers: Clues to the formation of monogenetic volcanic fields

    NASA Astrophysics Data System (ADS)

    Le Corvec, Nicolas; Spörli, K. Bernhard; Rowland, Julie; Lindsay, Jan

    2013-09-01

    Monogenetic basaltic volcanic fields occur worldwide in tectonic environments ranging from extensional to convergent. Understanding similarities and differences between these fields may help to characterize key controls on their generation. Such volcanic fields consist of numerous volcanic centers, each of which represents a pathway of magma from its source to the surface. We analyzed the spatial distribution of volcanic centers in 37 monogenetic volcanic fields, and assuming that the distribution of volcanic centers relative to each other is matched by a similar source pattern within the mantle, applied the following methods for each: (1) the Poisson Nearest Neighbor (PNN) analysis, representing the degree to which the distribution of the volcanic centers departs from a predicted Poisson distribution, and (2) a volcanic alignment analysis to ascertain the preferential pathways, if any, used by the magma to reach the surface. This is the first comprehensive global comparison of such analyses. Magma pathways within the brittle upper crust are influenced to various degrees by two end-member situations: (1) formation of new extension fractures perpendicular to the least compressive stress (σ3) and (2) re-activation of pre-existing fractures that are near-parallel to the maximum principal stress (σ1). The results of the PNN analysis show that, independently of the tectonic environment, most volcanic fields display a clustered distribution of their volcanic centers. Alignment analysis shows that either the ambient tectonic environment exerts a strong influence on the preferential orientations of the volcanic alignments, or that it is in competition with other factors (e.g., pre-existing structures, local stress changes due to older intrusions). Overall, these results indicate that the propagation of the magma (and therefore the spatial distribution of the volcanic centers within volcanic fields) is the product of an interplay between deep level influences (i

  20. Biotic effects of impacts and volcanism

    NASA Astrophysics Data System (ADS)

    Keller, Gerta

    2003-10-01

    The biotic effects of late Maastrichtian mantle plume volcanism on Ninetyeast Ridge and Deccan volcanism mirror those of the Cretaceous-Tertiary (KT) mass extinction and impact event. Planktonic foraminifera responded to high stress conditions with the same impoverished and small-sized species assemblages dominated by the disaster/opportunists Guembelitria cretacea, which characterize the KT mass extinction worldwide. Similar high stress late Maastrichtian assemblages have recently been documented from Madagascar, Israel and Egypt. Biotic effects of volcanism cannot be differentiated from those of impacts, though every period of intense volcanism is associated with high stress assemblages, this is not the case with every impact. The most catastrophic biotic effects occurred at the KT boundary (65.0 Ma) when intense Deccan volcanism coincided with a major impact and caused the mass extinction of all tropical and subtropical species. The Chicxulub impact, which now appears to have predated the KT boundary by about 300 kyr, coincided with intense Deccan volcanism that resulted in high biotic stress and greenhouse warming, but no major extinctions. The unequivocal connection between intense volcanism and high stress assemblages during the late Maastrichtian to early Danian, and the evidence of multiple impacts, necessitates revision of current impact and mass extinction theories.