WorldWideScience

Sample records for siliceous microfossils diatoms

  1. Environmental investigations using diatom microfossils

    Science.gov (United States)

    Smith, Kathryn E.L.; Flocks, James G.

    2010-01-01

    Diatoms are unicellular phytoplankton (microscopic plant-like organisms) with cell walls made of silica (called a frustule). They live in both freshwater and saltwater and can be found in just about every place on Earth that is wet. The shape and morphology of the diatom frustule unique to each species are used for identification. Due to the microscopic size of diatoms, high-power microscopy is required for diatom identification. Diatoms are vital to life on Earth. They are photosynthetic primary producers, using sunlight to create oxygen and organic carbon from carbon dioxide and water. They are a significant source of the oxygen we breathe, have a major impact on the global carbon cycle (Smetacek, 1999), and are a food source for many aquatic organisms (Mann, 1993). Diatom abundance has even been demonstrated to have an influence on the diversity of larger marine mammals, including whales (Marx and Uhen, 2010). Data on diatom abundance and diversity are extremely useful in environmental studies.

  2. Selective silicate-directed motility in diatoms

    DEFF Research Database (Denmark)

    Bondoc, Karen Grace V.; Heuschele, Jan; Gillard, Jeroen

    2016-01-01

    the major sink in the global Si cycle. Dissolved silicic acid (dSi) availability frequently limits diatom productivity and influences species composition of communities. We show that benthic diatoms selectively perceive and behaviourally react to gradients of dSi. Cell speed increases under d...

  3. Temperature affects the silicate morphology in a diatom

    NARCIS (Netherlands)

    Javaheri, N.; Dries, R; Burson, A.; Stal, L.J.; Sloot, P.M.A.; Kaandorp, J.A.

    2015-01-01

    Silica deposition by diatoms, a common component of the phytoplankton, has attracted considerable interest given the importance in ecology and materials science. There has recently been a great deal of research into the biological control of biosilicifcation, yet the in vivo physical and chemical

  4. Temperature affects the silicate morphology in a diatom

    NARCIS (Netherlands)

    Javaheri, N.; Dries, R.; Burson, A.; Stal, L.J.; Sloot, P.M.A.; Kaandorp, J.A.

    2015-01-01

    Silica deposition by diatoms, a common component of the phytoplankton, has attracted considerable interest given the importance in ecology and materials science. There has recently been a great deal of research into the biological control of biosilicifcation, yet the in vivo physical and

  5. Oxygen isotopic ratio of the diatom siliceous valves: development of a new method in quantitative paleoclimatology

    International Nuclear Information System (INIS)

    Labeyrie, Laurent.

    1979-07-01

    This paper describes a new method allowing the measurement of the 18 O/ 16 O ratio of the biogenic silica oxygen, which takes into account the effects due to the organic matter and hydration water associated with this type of silica. By isotopic exchange with enriched water, we have been able to fix a treatment which eliminate all contamination and memory effects. This has permitted us to study the temperature dependance of the hydrated silica-water oxygen isotopic fractionation. As application, we present a study of the variations of the delta 18 O of fossil diatoms valves along an Equatorial Pacific sediment core covering the last 20.000 years. The results demonstrate the usefulness of the delta 18 O of the diatom silica for paleoclimatic investigations [fr

  6. Oxygen and silicon stable isotopes of diatom silica. Reconstructing changes in surface water hydrography and silicic acid utilization in the late Pleistocene subarctic Pacific

    Energy Technology Data Exchange (ETDEWEB)

    Maier, Edith

    2014-03-05

    Deglacial variations in upper ocean nutrient dynamics and stratification in high latitudes, as well as associated changes in thermohaline overturning circulation, are thought to have played a key role in changing atmospheric CO{sub 2} concentrations. This thesis examines the relationship between past changes in subarctic Pacific upper ocean stratification and nutrient (silicic acid) utilization, using oxygen and silicon stable isotopes of diatom silica, for the first time at millennial-scale resolution and analyzed with a new and efficient instrumentation set-up. The isotopic data, presented in three manuscripts, show a consistent picture of millennial-scale variability in upper ocean stratification and silicic acid utilization during the last ∝50 ka BP, e.g. indicating that the subarctic Pacific was a source region for atmospheric CO{sub 2} during the last deglaciation (late Heinrich Stadial 1 and the Boelling/Alleroed). The presented results demonstrate the high potential of combined diatom oxygen and silicon stable isotope analysis especially for, but not restricted to, marine regions characterized by a low biogenic carbonate content like the subarctic Pacific and the Southern Ocean.

  7. Oxygen and silicon stable isotopes of diatom silica. Reconstructing changes in surface water hydrography and silicic acid utilization in the late Pleistocene subarctic Pacific

    International Nuclear Information System (INIS)

    Maier, Edith

    2014-01-01

    Deglacial variations in upper ocean nutrient dynamics and stratification in high latitudes, as well as associated changes in thermohaline overturning circulation, are thought to have played a key role in changing atmospheric CO 2 concentrations. This thesis examines the relationship between past changes in subarctic Pacific upper ocean stratification and nutrient (silicic acid) utilization, using oxygen and silicon stable isotopes of diatom silica, for the first time at millennial-scale resolution and analyzed with a new and efficient instrumentation set-up. The isotopic data, presented in three manuscripts, show a consistent picture of millennial-scale variability in upper ocean stratification and silicic acid utilization during the last ∝50 ka BP, e.g. indicating that the subarctic Pacific was a source region for atmospheric CO 2 during the last deglaciation (late Heinrich Stadial 1 and the Boelling/Alleroed). The presented results demonstrate the high potential of combined diatom oxygen and silicon stable isotope analysis especially for, but not restricted to, marine regions characterized by a low biogenic carbonate content like the subarctic Pacific and the Southern Ocean.

  8. Evidence for marine microfossils from amber.

    Science.gov (United States)

    Girard, Vincent; Schmidt, Alexander R; Saint Martin, Simona; Struwe, Steffi; Perrichot, Vincent; Saint Martin, Jean-Paul; Grosheny, Danièle; Breton, Gérard; Néraudeau, Didier

    2008-11-11

    Amber usually contains inclusions of terrestrial and rarely limnetic organisms that were embedded in the places were they lived in the amber forests. Therefore, it has been supposed that amber could not have preserved marine organisms. Here, we report the discovery amber-preserved marine microfossils. Diverse marine diatoms as well as radiolarians, sponge spicules, a foraminifer, and a spine of a larval echinoderm were found in Late Albian and Early Cenomanian amber samples of southwestern France. The highly fossiliferous resin samples solidified approximately 100 million years ago on the floor of coastal mixed forests dominated by conifers. The amber forests of southwestern France grew directly along the coast of the Atlantic Ocean and were influenced by the nearby sea: shells and remnants of marine organisms were probably introduced by wind, spray, or high tide from the beach or the sea onto the resin flows.

  9. Eruptive and environmental processes recorded by diatoms in volcanically-dispersed lake sediments from the Taupo Volcanic Zone, New Zealand

    Science.gov (United States)

    Harper, Margaret A.; Pledger, Shirley A.; Smith, Euan G. C.; Van Eaton, Alexa; Wilson, Colin J. N.

    2015-01-01

    Late Pleistocene diatomaceous sediment was widely dispersed along with volcanic ash (tephra) across and beyond New Zealand by the 25.4 ka Oruanui supereruption from Taupo volcano. We present a detailed analysis of the diatom populations in the Oruanui tephra and the newly discovered floras in two other eruptions from the same volcano: the 28.6 ka Okaia and 1.8 ka Taupo eruptions. For comparison, the diatoms were also examined in Late Pleistocene and Holocene lake sediments from the Taupo Volcanic Zone (TVZ). Our study demonstrates how these microfossils provide insights into the lake history of the TVZ since the Last Glacial Maximum. Morphometric analysis of Aulacoseira valve dimensions provides a useful quantitative tool to distinguish environmental and eruptive processes within and between individual tephras. The Oruanui and Okaia diatom species and valve dimensions are highly consistent with a shared volcanic source, paleolake and eruption style (involving large-scale magma-water interaction). They are distinct from lacustrine sediments sourced elsewhere in the TVZ. Correspondence analysis shows that small, intact samples of erupted lake sediment (i.e., lithic clasts in ignimbrite) contain heterogeneous diatom populations, reflecting local variability in species composition of the paleolake and its shallowly-buried sediments. Our analysis also shows a dramatic post-Oruanui supereruption decline in Cyclostephanos novaezelandiae, which likely reflects a combination of (1) reorganisation of the watershed in the aftermath of the eruption, and (2) overall climate warming following the Last Glacial Maximum. This decline is reflected in substantially lower proportions of C. novaezelandiae in the 1.8 ka Taupo eruption deposits, and even fewer in post-1.8 ka sediments from modern (Holocene) Lake Taupo. Our analysis highlights how the excellent preservation of siliceous microfossils in volcanic tephra may fingerprint the volcanic source region and retain a valuable record

  10. Microfossil measures of rapid sea-level rise: Timing of response of two microfossil groups to a sudden tidal-flooding experiment in Cascadia

    Science.gov (United States)

    Horton, B.P.; Milker, Yvonne; Dura, T.; Wang, Kelin; Bridgeland, W.T.; Brophy, Laura S.; Ewald, M.; Khan, Nicole; Engelhart, S.E.; Nelson, Alan R.; Witter, Robert C.

    2017-01-01

    Comparisons of pre-earthquake and post-earthquake microfossils in tidal sequences are accurate means to measure coastal subsidence during past subduction earthquakes, but the amount of subsidence is uncertain, because the response times of fossil taxa to coseismic relative sea-level (RSL) rise are unknown. We measured the response of diatoms and foraminifera to restoration of a salt marsh in southern Oregon, USA. Tidal flooding following dike removal caused an RSL rise of ∼1 m, as might occur by coseismic subsidence during momentum magnitude (Mw) 8.1–8.8 earthquakes on this section of the Cascadia subduction zone. Less than two weeks after dike removal, diatoms colonized low marsh and tidal flats in large numbers, showing that they can record seismically induced subsidence soon after earthquakes. In contrast, low-marsh foraminifera took at least 11 months to appear in sizeable numbers. Where subsidence measured with diatoms and foraminifera differs, their different response times may provide an estimate of postseismic vertical deformation in the months following past megathrust earthquakes.

  11. A Southern Ocean Diatom Record of the Mid-Pleistocene Transition from the Amundsen Sea, Antarctica

    Science.gov (United States)

    Konfirst, M. A.; Scherer, R. P.

    2010-12-01

    In 2001 an 18.49m core was collected aboard Polarstern (cruise ANT-XVIII/5a) from the upper continental rise offshore from Pine Island Bay in the Amundsen Sea (69°19’S, 108°27’W) at 4014 m water depth. This location is important because it is one of the three main discharge locations for the WAIS and it is expected that IRD from melting icebergs would be concentrated in this region. Hillenbrand et al. (2009) collected data on magnetic susceptibility, wet bulk density, water content, biogenic opal, Ba/Al ratios (as a proxy for paleoproductivity), clay mineral content, and sand/ gravel fractions. To complement this data set, a high-resolution record (sample spacing 10cm) of the siliceous microfossil assemblages (diatoms and silicoflagellates) present in the core has been generated. Data include both relative abundance of individual diatom species and genera and absolute diatom abundance. Species composition in the upper 1004 cm is dominated by Fragilariopsis kerguelensis, which consistently composes 80-90% of the assemblage. Below 1004 cm the assemblage is more diverse, with Actinocyclus ingens, Thalassiothrix antarctica and F. kerguelensis consistently comprising the bulk of the assemblage. Additionally, the occurrence of A. ingens, Thalassiosira elliptipora and T. fasciculata can be used to confirm and further refine the age model established by Hillenbrand et al. (2009). Absolute abundance of diatom frustules varies from samples completely barren fossils to those with concentrations >4 x 107 valves/ g sediment and follows the biogenic opal measurements of Hillenbrand et al. (2009). A clear relationship between diatom abundance and glacial/interglacial variability is apparent in the upper 1004 cm and has been documented in the geochemical measurements of Hillenbrand et al. (2009). Significantly lower absolute abundance is observed below ~1004 cm; however, intervals with samples barren of fossils continue to alternate with those containing low concentrations

  12. Identifying early Earth microfossils in unsilicified sediments

    Science.gov (United States)

    Javaux, Emmanuelle J.; Asael, Dan; Bekker, Andrey; Debaille, Vinciane; Derenne, Sylvie; Hofmann, Axel; Mattielli, Nadine; Poulton, Simon

    2013-04-01

    The search for life on the early Earth or beyond Earth requires the definition of biosignatures, or "indices of life". These traditionally include fossil molecules, isotopic fractionations, biosedimentary structures and morphological fossils interpreted as remnants of life preserved in rocks. This research focuses on traces of life preserved in unsilicified siliciclastic sediments. Indeed, these deposits preserve well sedimentary structures indicative of past aqueous environments and organic matter, including the original organic walls of microscopic organisms. They also do not form in hydrothermal conditions which may be source of abiotic organics. At our knowledge, the only reported occurrence of microfossils preserved in unsilicified Archean sediments is a population of large organic-walled vesicles discovered in shales and siltstones of the 3.2 Ga Moodies Group, South Africa. (Javaux et al, Nature 2010). These have been interpreted as microfossils based on petrographic and geochemical evidence for their endogenicity and syngeneity, their carbonaceous composition, cellular morphology and ultrastructure, occurrence in populations, taphonomic features of soft wall deformation, and the geological context plausible for life, as well as lack of abiotic explanation falsifying a biological origin. Demonstrating that carbonaceous objects from Archaean rocks are truly old and truly biological is the subject of considerable debate. Abiotic processes are known to produce organics and isotopic signatures similar to life. Spheroidal pseudofossils may form as self-assembling vesicles from abiotic CM, e.g. in prebiotic chemistry experiments (Shoztak et al, 2001), from meteoritic lipids (Deamer et al, 2006), or hydrothermal fluids (Akashi et al, 1996); by artifact of maceration; by migration of abiotic or biotic CM along microfractures (VanZuilen et al, 2007) or along mineral casts (Brasier et al, 2005), or around silica spheres formed in silica-saturated water (Jones and

  13. Fossil diatoms imply common cometary origin of space-dust and the Polonnaruwa meteorite

    Science.gov (United States)

    Miyake, N.; Wallis, M. K.; Wickramasinghe, N. C.

    2013-09-01

    IDPs collected in 2001 at 40km altitude by cryosamplers studied via scanning electron microscopy and EDX were found to contain siliceous fibres and whiskers, some isolated but often embedded in a mineral matrix. The newly-arrived Polonnaruwa meteorite gives strong evidence for the hypothesis that they are fragments of diatoms agglomerating on solar system icy bodies. Diatom frustules and even whole diatom skeletons are identifiable within the meteorite. Specimens of a siliceous exoskeleton with multiple spines/whiskers have also been found, thought to be freshwater diatoms. As diatoms are dependent on a source of nitrogenous organics, the siliceous whiskers within IDPs would be an indicator of a photosynthesizing ecosystem, probably on a comet.

  14. Biophotonics of diatoms

    DEFF Research Database (Denmark)

    Gössling, Johannes Wilhelm

    Diatoms are unicellular microalgae present in all aquatic environments on earth. Due to their high photosynthetic productivity and abundance, diatoms are main components of aquatic food webs and among the main contributors of global photosynthetic carbon fixation. A unique feature of diatoms...

  15. Historical trends of hypoxia in Changjiang River estuary: Applications of chemical biomarkers and microfossils

    Science.gov (United States)

    Li, X.; Bianchi, T.S.; Yang, Z.; Osterman, L.E.; Allison, M.A.; DiMarco, Steven F.; Yang, G.

    2011-01-01

    Over the past two decades China has become the largest global consumer of fertilizers, which has enhanced river nutrient fluxes and caused eutrophication and hypoxia in the Yangtze (Changjiang) large river delta-front estuary (LDE). In this study, we utilized plant pigments, lignin-phenols, stable isotopes (δ13C and δ15N) and foraminiferal microfossils in 210Pb dated cores to examine the history of hypoxia in the Changjiang LDE. Two sediment cores were collected onboard R/V Dong Fang Hong 2 using a stainless-steel box-corer; one at a water depth of 24.7 m on Jun. 15, 2006 and the other at 52 m on Nov. 20, 2007, both in the hypoxic region off the Changjiang LDE. There has been a significant increase in the abundance of plant pigments after 1979 that are indicators of enhanced diatom and cyanobacterial abundance, which agrees with post-1980 record of increasing nutrient loads in the Changjiang River. The increased inputs of terrestrially derived materials to the LDE are largely woody plant sources and most likely due to deforestation that began in the early 1950s. However, post-1960 lignin data did not reflect enhanced loading of woody materials despite continued deforestation possibly due to increased trapping from greater dam construction, a reduction of deforestation in the drainage basin since the last 1990s, and soil conservation practices. The lack of linkages between bulk indices (stable isotopes, % OC, molar C/N ratios) and microfossil/chemical biomarkers may reflect relative differences in the amount of carbon tracked by these different proxies. Although NO3− is likely responsible for most of the changes in phytoplankton production (post 1970s), historical changes in N loading from the watershed and hypoxia on the LDE shelf may not be as well linked in East China Sea (ECS) sediments due to possible denitrification/ammonification processes; finally, increases in low-oxygen tolerant foraminiferal microfossils indicate there has been an increase in the

  16. Compaction of microfossil and clay-rich chalk sediments

    DEFF Research Database (Denmark)

    Fabricius, Ida Lykke

    2001-01-01

    The aim of this study was to evaluate the role of microfossils and clay in the compaction of chalk facies sediments. To meet this aim, chalk sediments with varying micro texture were studied. The sediments have been tested uniaxially confined in a stainless-steel compaction cell. The sediments are......: 1) Pure carbonate chalk with mudstone texture from Stevns Klint (Denmark), 2) Relatively pure chalk sediments with varying content of microfossils from the Ontong Java Plateau (Western Pacific), 3) Clay-rich chalk and mixed sediments from the Caribbean. The tested samples were characterised...

  17. Late Maastrichtian foraminiferids and diatoms from the Polish Carpathians (Ropianka Formation, Skole Nappe): a case study from the Chmielnik-Grabówka composite section

    Science.gov (United States)

    Gasiński, M. Adam; Olshtynska, Alexandra; Uchman, Alfred

    2013-12-01

    Gasiński, M.A., Olshtynska, A. and Uchman, A. 2013. Late Maastrichtian foraminiferids and diatoms from the Polish Carpathians (Ropianka Formation, Skole Nappe): a case study from the Chmielnik-Grabowka composite section. Acta Geologica Polonica, 63(4), 515-525. Warszawa. Well-preserved foraminiferids have been found in the Chmielnik-Grabowka section (Skole Nappe, Polish Carpathians). The Abathomphalus mayaroensis (late Maastrichtian) and Racemiguembelina fructicosa (earlylate Maastrichtian) standard planktonic foraminiferal biozones have been recognized, based on the occurrence of their respective index species. Sediments of the R. fructicosa Zone contain diatoms, which are a rare component of Cretaceous flysch microfossil assemblages in the Carpathians. The diatom frustules and some foraminiferid tests are pyritized, probably after burial in the sediment, below the redox boundary or in the oxygen- deficient microenvironment inside the frustules or tests of microfossils; the presence of trace fossils and bioturbational structures in the same bed indicate an oxygenated sea floor.

  18. Diatoms - nature materials with great potential for bioapplications

    Directory of Open Access Journals (Sweden)

    Medarević Đorđe P.

    2016-01-01

    Full Text Available Diatoms are widespread unicellular photosynthetic algae that produce unique highly ordered siliceous cell wall, called frustule. Micro- to nanoporous structure with high surface area that can be easily modified, high mechanical resistance, unique optical features (light focusing and luminescence and biocompatibility make diatom frustule as a suitable raw material for the development of devices such as bio- and gas sensors, microfluidic particle sorting devices, supercapacitors, batteries, solar cells, electroluminescent devices and drug delivery systems. Their wide availability in the form of fossil remains (diatomite or diatomaceous earth as well as easy cultivation in the artificial conditions further supports use of diatoms in many different fields of application. This review focused on the recent achievements in the diatom bioapplications such as drug delivery, biomolecules immobilization, bio- and gas sensing, since great progress was made in this field over the last several years.

  19. Acidification counteracts negative effects of warming on diatom silicification

    KAUST Repository

    Coello-Camba, Alexandra

    2016-10-24

    Diatoms are a significant group contributing up to 40 % of annual primary production in the oceans. They have a special siliceous cell wall that, acting as a ballast, plays a key role in the sequestration of global carbon and silica. Diatoms dominate primary production in the Arctic Ocean, where global climate change is causing increases in water temperature and in the partial pressure of CO2 (pCO2). Here we show that as water temperature increases diatoms become stressed, grow to smaller sizes, and decrease their silicification rates. But at higher pCO2, as the pH of seawater decreases, silica incorporation rates are increased. In a future warmer Arctic ocean diatoms may have a competitive advantage under increased ocean acidification, as increased pCO2 counteracts the adverse effects of increasing temperature on silicification and buffers its consequences in the biogeochemical cycles of carbon and silica.

  20. Acidification counteracts negative effects of warming on diatom silicification

    KAUST Repository

    Coello-Camba, Alexandra; Agusti, Susana

    2016-01-01

    Diatoms are a significant group contributing up to 40 % of annual primary production in the oceans. They have a special siliceous cell wall that, acting as a ballast, plays a key role in the sequestration of global carbon and silica. Diatoms dominate primary production in the Arctic Ocean, where global climate change is causing increases in water temperature and in the partial pressure of CO2 (pCO2). Here we show that as water temperature increases diatoms become stressed, grow to smaller sizes, and decrease their silicification rates. But at higher pCO2, as the pH of seawater decreases, silica incorporation rates are increased. In a future warmer Arctic ocean diatoms may have a competitive advantage under increased ocean acidification, as increased pCO2 counteracts the adverse effects of increasing temperature on silicification and buffers its consequences in the biogeochemical cycles of carbon and silica.

  1. Cenozoic planktonic marine diatom diversity and correlation to climate change

    Science.gov (United States)

    Lazarus, David; Barron, John; Renaudie, Johan; Diver, Patrick; Türke, Andreas

    2014-01-01

    Marine planktonic diatoms export carbon to the deep ocean, playing a key role in the global carbon cycle. Although commonly thought to have diversified over the Cenozoic as global oceans cooled, only two conflicting quantitative reconstructions exist, both from the Neptune deep-sea microfossil occurrences database. Total diversity shows Cenozoic increase but is sample size biased; conventional subsampling shows little net change. We calculate diversity from a separately compiled new diatom species range catalog, and recalculate Neptune subsampled-in-bin diversity using new methods to correct for increasing Cenozoic geographic endemism and decreasing Cenozoic evenness. We find coherent, substantial Cenozoic diversification in both datasets. Many living cold water species, including species important for export productivity, originate only in the latest Miocene or younger. We make a first quantitative comparison of diatom diversity to the global Cenozoic benthic ∂18O (climate) and carbon cycle records (∂13C, and 20-0 Ma pCO2). Warmer climates are strongly correlated with lower diatom diversity (raw: rho = .92, p2 were only moderately higher than today. Diversity is strongly correlated to both ∂13C and pCO2 over the last 15 my (for both: r>.9, detrended r>.6, all p<.001), but only weakly over the earlier Cenozoic, suggesting increasingly strong linkage of diatom and climate evolution in the Neogene. Our results suggest that many living marine planktonic diatom species may be at risk of extinction in future warm oceans, with an unknown but potentially substantial negative impact on the ocean biologic pump and oceanic carbon sequestration. We cannot however extrapolate our my-scale correlations with generic climate proxies to anthropogenic time-scales of warming without additional species-specific information on proximate ecologic controls.

  2. Cenozoic planktonic marine diatom diversity and correlation to climate change.

    Directory of Open Access Journals (Sweden)

    David Lazarus

    Full Text Available Marine planktonic diatoms export carbon to the deep ocean, playing a key role in the global carbon cycle. Although commonly thought to have diversified over the Cenozoic as global oceans cooled, only two conflicting quantitative reconstructions exist, both from the Neptune deep-sea microfossil occurrences database. Total diversity shows Cenozoic increase but is sample size biased; conventional subsampling shows little net change. We calculate diversity from a separately compiled new diatom species range catalog, and recalculate Neptune subsampled-in-bin diversity using new methods to correct for increasing Cenozoic geographic endemism and decreasing Cenozoic evenness. We find coherent, substantial Cenozoic diversification in both datasets. Many living cold water species, including species important for export productivity, originate only in the latest Miocene or younger. We make a first quantitative comparison of diatom diversity to the global Cenozoic benthic ∂(18O (climate and carbon cycle records (∂(13C, and 20-0 Ma pCO2. Warmer climates are strongly correlated with lower diatom diversity (raw: rho = .92, p.9, detrended r>.6, all p<.001, but only weakly over the earlier Cenozoic, suggesting increasingly strong linkage of diatom and climate evolution in the Neogene. Our results suggest that many living marine planktonic diatom species may be at risk of extinction in future warm oceans, with an unknown but potentially substantial negative impact on the ocean biologic pump and oceanic carbon sequestration. We cannot however extrapolate our my-scale correlations with generic climate proxies to anthropogenic time-scales of warming without additional species-specific information on proximate ecologic controls.

  3. Microfossils' diversity from the Proterozoic Taoudeni Basin, Mauritania

    Science.gov (United States)

    Beghin, Jérémie; Houzay, Jean-Pierre; Blanpied, Christian; Javaux, Emmanuelle

    2014-05-01

    Prokaryotes and microscopic eukaryotes are known to have appeared well before the Cambrian's adaptative radiation which flourished perceptibly as a generalized macroscopic world. What do we know about the trigger events which stimulated eukaryotic diversification during the Proterozoic? Biological innovations or environmental changes, and indeed probably both (Knoll et al., 2006), played a fundamental role controlling this important step of life's evolution on Earth. Javaux (2011), proposed a diversification pattern of early eukaryotes divided into three steps and focusing on different taxonomic levels, from stem group to within crown group, of the domain Eukarya. Here, we present a new, exquisitely preserved and morphologically diverse assemblage of organic-walled microfossils from the 1.1 Ga El Mreiti Group of the Taoudeni Basin (Mauritania). The assemblage includes beautifully preserved microbial mats comprising pyritized filaments, prokaryotic filamentous sheaths and filaments, microfossils of uncertain biological affinity including smooth isolated and colonial sphaeromorphs (eukaryotes and/or prokaryotes), diverse protists (ornamented and process-bearing acritarchs), as well multicellular microfossils interpreted in the literature as possible xanthophyte algae. Several taxa are reported for the first time in Africa, but are known worldwide. This study improves microfossil diversity previously reported by Amard (1986) and shows purported xanthophyte algae contrary to a previous biomarker study suggesting the absence of eukaryotic algae, other than acritarchs, in the basin (Blumenberg et al., 2012). This new microfossil assemblage and others provide, all together, evidences of early and worldwide diversification of eukaryotes. Thereby, those first qualitative results also provide a basis for further and larger quantitative studies on the Taoudeni Basin. To better understand the palaeobiology (stem or crown group, aerobic or anaerobic metabolism) and

  4. New Mesozoic and Cenozoic fossils from Ecuador: Invertebrates, vertebrates, plants, and microfossils

    Science.gov (United States)

    Cadena, Edwin A.; Mejia-Molina, Alejandra; Brito, Carla M.; Peñafiel, Sofia; Sanmartin, Kleber J.; Sarmiento, Luis B.

    2018-04-01

    Ecuador is well known for its extensive extant biodiversity, however, its paleobiodiversity is still poorly explored. Here we report seven new Mesozoic and Cenozoic fossil localities from the Pacific coast, inter-Andean depression and Napo basin of Ecuador, including vertebrates, invertebrates, plants, and microfossils. The first of these localities is called El Refugio, located near the small town of Chota, Imbabura Province, from where we report several morphotypes of fossil leaves and a mycetopodid freshwater mussel of the Upper Miocene Chota Formation. A second site is also located near the town of Chota, corresponding to potentially Pleistocene to Holocene lake deposits from which we report the occurrence of leaves and fossil diatoms. A third locality is at the Pacific coast of the country, near Rocafuerte, a town in Esmeraldas Province, from which we report a late Miocene palm leaf. We also report the first partially articulated skull with teeth from a Miocene scombridid (Mackerels) fish from El Cruce locality, and completely preserved seeds from La Pila locality, both sites from Manabí Province. Two late Cretaceous fossil sites from the Napo Province, one near Puerto Napo showing a good record of fossil shrimps and a second near the town of Loreto shows the occurrence of granular amber and small gymnosperms seeds and cuticles. All these new sites and fossils show the high potential of the sedimentary sequences and basins of Ecuador for paleontological studies and for a better understanding of the fossil record of the country and northern South America.

  5. Silicate glasses

    International Nuclear Information System (INIS)

    Lutze, W.

    1988-01-01

    Vitrification of liquid high-level radioactive wastes has received the greatest attention, world-wide, compared to any other HLW solidification process. The waste form is a borosilicate-based glass. The production of phosphate-based glass has been abandoned in the western world. Only in the Soviet Union are phosphate-based glasses still being developed. Vitrification techniques, equipment and processes and their remote operation have been developed and studied for almost thirty years and have reached a high degree of technical maturity. Industrial demonstration of the vitrification process has been in progress since 1978. This chapter is a survey of world-wide research and development efforts in nuclear waste glasses and its production technology. The principal glasses considered are silicate glasses which contain boron, i.e., borosilicate glasses

  6. Diatoms and the nanotechnology

    International Nuclear Information System (INIS)

    Toekesi, K.; Bereczky, R.J.; Lakatos, Gy.; Cserhati, C.

    2004-01-01

    Complete text of publication follows. During the last decade studies of interactions between highly charged ions (HCI) and solid surfaces are at the center of interest which is partly stimulated by potential future technical application such as nanofabrication. The investigation of the interactions of highly charged ions with internal surfaces recently become available due to the advances in the fabrication of micro- and nanocapillaries. These target materials offer the opportunity to observe 'hollow atom' formation in free space. Hollow atoms are an exotic form of matter where the atomic charge cloud resides in shells with large diameters while the core is virtually empty. In the past there has been an increasing amount of indirect evidence for the existence of this atomic state. Microcapillary transmission promises to provide direct evidence for the hollow atom formation for the first time. Our earlier theoretical descriptions rely on metallic microcapillaries which have proven to be quite successful in comparison with experimental data. However, since very detailed measurements have recently become available for insulator nanocapillaries, critical and precise tests of theory are only now being possible. We note, that the theoretical description of the interaction between the HCI and insulator nanocapillaries is far from being well understood. One of the key point of the experimental investigations is the preparation of the nanocapillaries. In this work we propose an alternative way to prepare insulator nanocapillaries. We take an advantage of the nature that during the evolution the cylindrical shape nanostructure was developed as a truss of diatoms. The truss of the diatoms contains roughly 99 % SiO 2 and in some cases of diatoms it form almost ideal cylindrical shape. As an example Fig. 1 shows the scanning electron micrograph of the diatom. The size of the holes in the truss are in the nanometer range (see Fig. 1a). On the basis of these properties the

  7. Photosynthetic Pigments in Diatoms

    OpenAIRE

    Kuczynska, Paulina; Jemiola-Rzeminska, Malgorzata; Strzalka, Kazimierz

    2015-01-01

    Photosynthetic pigments are bioactive compounds of great importance for the food, cosmetic, and pharmaceutical industries. They are not only responsible for capturing solar energy to carry out photosynthesis, but also play a role in photoprotective processes and display antioxidant activity, all of which contribute to effective biomass and oxygen production. Diatoms are organisms of a distinct pigment composition, substantially different from that present in plants. Apart from light-harvestin...

  8. Photosynthetic Pigments in Diatoms.

    Science.gov (United States)

    Kuczynska, Paulina; Jemiola-Rzeminska, Malgorzata; Strzalka, Kazimierz

    2015-09-16

    Photosynthetic pigments are bioactive compounds of great importance for the food, cosmetic, and pharmaceutical industries. They are not only responsible for capturing solar energy to carry out photosynthesis, but also play a role in photoprotective processes and display antioxidant activity, all of which contribute to effective biomass and oxygen production. Diatoms are organisms of a distinct pigment composition, substantially different from that present in plants. Apart from light-harvesting pigments such as chlorophyll a, chlorophyll c, and fucoxanthin, there is a group of photoprotective carotenoids which includes β-carotene and the xanthophylls, diatoxanthin, diadinoxanthin, violaxanthin, antheraxanthin, and zeaxanthin, which are engaged in the xanthophyll cycle. Additionally, some intermediate products of biosynthetic pathways have been identified in diatoms as well as unusual pigments, e.g., marennine. Marine algae have become widely recognized as a source of unique bioactive compounds for potential industrial, pharmaceutical, and medical applications. In this review, we summarize current knowledge on diatom photosynthetic pigments complemented by some new insights regarding their physico-chemical properties, biological role, and biosynthetic pathways, as well as the regulation of pigment level in the cell, methods of purification, and significance in industries.

  9. Photosynthetic Pigments in Diatoms

    Directory of Open Access Journals (Sweden)

    Paulina Kuczynska

    2015-09-01

    Full Text Available Photosynthetic pigments are bioactive compounds of great importance for the food, cosmetic, and pharmaceutical industries. They are not only responsible for capturing solar energy to carry out photosynthesis, but also play a role in photoprotective processes and display antioxidant activity, all of which contribute to effective biomass and oxygen production. Diatoms are organisms of a distinct pigment composition, substantially different from that present in plants. Apart from light-harvesting pigments such as chlorophyll a, chlorophyll c, and fucoxanthin, there is a group of photoprotective carotenoids which includes β-carotene and the xanthophylls, diatoxanthin, diadinoxanthin, violaxanthin, antheraxanthin, and zeaxanthin, which are engaged in the xanthophyll cycle. Additionally, some intermediate products of biosynthetic pathways have been identified in diatoms as well as unusual pigments, e.g., marennine. Marine algae have become widely recognized as a source of unique bioactive compounds for potential industrial, pharmaceutical, and medical applications. In this review, we summarize current knowledge on diatom photosynthetic pigments complemented by some new insights regarding their physico-chemical properties, biological role, and biosynthetic pathways, as well as the regulation of pigment level in the cell, methods of purification, and significance in industries.

  10. Diatomic gasdynamic lasers.

    Science.gov (United States)

    Mckenzie, R. L.

    1972-01-01

    Predictions from a numerical model of the vibrational relaxation of anharmonic diatomic oscillators in supersonic expansions are used to show the extent to which the small anharmonicity of gases like CO can cause significant overpopulations of upper vibrational states. When mixtures of CO and N2 are considered, radiative gain on many of the vibration-rotation transitions of CO is predicted. Experiments are described that qualitatively verify the predictions by demonstrating laser oscillation in CO-N2 expansions. The resulting CO-N2 gasdynamic laser displays performance characteristics that equal or exceed those of similar CO2 lasers.

  11. Diatomic gasdynamic lasers

    International Nuclear Information System (INIS)

    McKenzie, R.L.

    1971-12-01

    Predictions from a numerical model of the vibrational relaxation of anharmonic diatomic oscillators in supersonic expansions are used to show the extent to which the small anharmonicity of gases like CO can cause significant over-populations of upper vibrational states. When mixtures of CO and N 2 are considered, radiative gain on many of the vibration-rotation transitions of CO is predicted. Experiments are described that qualitatively verify the predictions by demonstrating laser oscillation in CO-N 2 expansions. The resulting CO-N 2 gasdynamic laser displays performance characteristics that equal or exceed those of similar CO 2 lasers

  12. Controlling dynamics in diatomic systems

    Indian Academy of Sciences (India)

    WINTEC

    Abstract. Controlling molecular energetics using laser pulses is exemplified for nuclear motion in two different diatomic systems. The problem of finding the optimized field for maximizing a desired quantum dynamical target is formulated using an iterative method. The method is applied for two diatomic sys- tems, HF and OH.

  13. Diatom. A potential bio-accumulator of gold

    International Nuclear Information System (INIS)

    Chakraborty, N.; Pal, R.; Ramaswami, A.; Nayak, D.; Lahiri, S.

    2006-01-01

    The bioaccumulation of gold in trace concentration by Nitzschia obtusa and Navicula minima, two members of bacillariophyceae, has been studied. It has been observed that Nitzschia obtusa showed better accumulation of gold in acidic pH in comparison to neutral and basic pH. Maximum accumulation was observed with 1 mg x kg -1 or less gold concentration. However, the accumulation by the living cells was reduced when the matrix concentration was higher. Navicula minima, on the other hand, found to be a better accumulator of gold in wide ranges of pH and substrate concentration of the media. It was also inferred that the gold accumulation by diatom was mainly due to adsorption by biosilica (siliceous frustules of dead diatom cells). Accumulated gold was recovered with conc. HNO 3 . (author)

  14. Biomarkers and Microfossils in the Murchison, Rainbow, and Tagish Lake meteorites

    Science.gov (United States)

    Hoover, Richard B.; Jerman, Gregory A.; Rozanov, Alexei Y.; Davies, Paul C.

    2003-02-01

    During the past six years, we have conducted extensive scanning electron and optical microscopy investigations and x-ray analysis to determine the morphology, life cycle processes, and elemental distributions in living and fossil cyanobacteria, bacteria, archaea, fungi, and algae sampled from terrestrial environments relevant to Astrobiology. Biominerals, pseudomorphs and microfossils have been studied for diverse microbial groups in various states of preservation in many types of rocks (e.g., oil shales, graphites, shungites, bauxites, limestones, pyrites, phosphorites, and hydrothermal vent chimneys). Results of these studies have been applied to the search for biosignatures in carbonaceous chondrites, stony, and nickel iron meteorites. We review important biomarkers found in terrestrial rocks and meteorites and present additional evidence for the existence of indigenous bacterial microfossils in-situ in freshly fractured surfaces of the Murchison, Rainbow and Tagish Lake carbonaceous meteorites. We provide secondary and backscatter electron images and spectral data obtained with Field Emission and Environmental Scanning Electron Microscopes of biominerals and microfossils. We discuss techniques for discriminating indigenous microfossils from recent terrestrial contaminants. Images are provided of framboidal magnetites in oil shales and meteorites and images and 2D x-ray maps are shown of bacterial microfossils embedded in the mineral matrix of the Murchison, Rainbow and Tagish Lake Carbonaceous Meteorites. These microfossils exhibit characteristics that preclude their interpretation as post-arrival contaminants and we interpret them as indigenous biogenic remains.

  15. A synthesis of post-glacial diatom records from Lake Baikal

    Science.gov (United States)

    Bradbury, J. Platt; Bezrukova, E.; Chernyaeva, G.; Colman, S.M.; Khursevich, G.; King, J.W.; Likoshway, Ye. V.

    1994-01-01

    The biostratigraphy of fossil diatoms contributes important chronologic, paleolimnologic, and paleoclimatic information from Lake Baikal in southeastern Siberia. Diatoms are the dominant and best preserved microfossils in the sediments, and distinctive assemblages and species provide inter-core correlations throughout the basin at millennial to centennial scales, in both high and low sedimentation-rate environments. Distributions of unique species, once dated by radiocarbon, allow diatoms to be used as dating tools for the Holocene history of the lake.Diatom, pollen, and organic geochemical records from site 305, at the foot of the Selenga Delta, provide a history of paleolimnologic and paleoclimatic changes from the late glacial (15 ka) through the Holocene. Before 14 ka diatoms were very rare, probably because excessive turbidity from glacial meltwater entering the lake impeded productivity. Between 14 and 12 ka, lake productivity increased, perhaps as strong winds promoted deep mixing and nutrient regeneration. Pollen evidence suggests a cold shrub — steppe landscape dominated the central Baikal depression at this time. As summer insolation increased, conifers replaced steppe taxa, but diatom productivity declined between 11 and 9 ka perhaps as a result of increased summer turbidity resulting from violent storm runoff entering the lake via short, steep drainages. After 8 ka, drier, but more continental climates prevailed, and the modern diatom flora of Lake Baikal came to prominence.On Academician Ridge, a site of slow sedimentation rates, Holocene diatom assemblages at the top of 10-m cores reappear at deeper levels suggesting that such cores record at least two previous interglacial (or interstadial?) periods. Nevertheless, distinctive species that developed prior to the last glacial period indicate that the dynamics of nutrient cycling in Baikal and the responsible regional climatic environments were not entirely analogous to Holocene conditions. During

  16. Calcareous microfossil-based orbital cyclostratigraphy in the Arctic Ocean

    Science.gov (United States)

    Marzen, Rachel; DeNinno, Lauren H.; Cronin, Thomas M.

    2016-01-01

    Microfaunal and geochemical proxies from marine sediment records from central Arctic Ocean (CAO) submarine ridges suggest a close relationship over the last 550 thousand years (kyr) between orbital-scale climatic oscillations, sea-ice cover, marine biological productivity and other parameters. Multiple paleoclimate proxies record glacial to interglacial cycles. To understand the climate-cryosphere-productivity relationship, we examined the cyclostratigraphy of calcareous microfossils and constructed a composite Arctic Paleoclimate Index (API) "stack" from benthic foraminiferal and ostracode density from 14 sediment cores. Following the hypothesis that API is driven mainly by changes in sea-ice related productivity, the API stack shows the Arctic experienced a series of highly productive interglacials and interstadials every ∼20 kyr. These periods signify minimal ice shelf and sea-ice cover and maximum marine productivity. Rapid transitions in productivity are seen during shifts from interglacial to glacial climate states. Discrepancies between the Arctic API curves and various global climatic, sea-level and ice-volume curves suggest abrupt growth and decay of Arctic ice shelves related to climatic and sea level oscillations.

  17. Towards a representative periphytic diatom sample

    Directory of Open Access Journals (Sweden)

    2007-01-01

    Full Text Available The need to acquire a representative periphytic diatom sample for river water quality monitoring has been recognised in the development of existing diatom indices, important in the development and employment of diatom monitoring tools for the Water Framework Directive. In this study, a nested design with replication is employed to investigate the magnitude of variation in diatom biomass, composition and Trophic Diatom Index at varying scales within a small chalk river. The study shows that the use of artificial substrates may not result in diatom communities that are typical of the surrounding natural substrates. Periphytic diatom biomass and composition varies between artificial and natural substrates, riffles and glides and between two stretches of the river channel. The study also highlights the existence of high variation in diatom frustule frequency and biovolume at the individual replicate scale which may have implications for the use of diatoms in routine monitoring.

  18. Nature engineered diatom biosilica as drug delivery systems.

    Science.gov (United States)

    Uthappa, U T; Brahmkhatri, Varsha; Sriram, G; Jung, Ho-Young; Yu, Jingxian; Kurkuri, Nikita; Aminabhavi, Tejraj M; Altalhi, Tariq; Neelgund, Gururaj M; Kurkuri, Mahaveer D

    2018-05-14

    Diatoms, unicellular photosynthetic algae covered with siliceous cell wall, are also called frustule. These are the most potential naturally available materials for the development of cost-effective drug delivery systems because of their excellent biocompatibility, high surface area, low cost and ease of surface modification. Mesoporous silica materials such as MCM-41 and SBA-15 have been extensively used in drug delivery area. Their synthesis is challenging, time consuming, requires toxic chemicals and are energy intensive, making the entire process expensive and non-viable. Therefore, it is necessary to explore alternative materials. Surprisingly, nature has provided some exciting materials called diatoms; biosilica is one such a material that can be potentially used as a drug delivery vehicle. The present review focuses on different types of diatom species used in drug delivery with respect to their structural properties, morphology, purification process and surface functionalization. In this review, recent advances along with their limitations as well as the future scope to develop them as potential drug delivery vehicles are discussed. Copyright © 2018. Published by Elsevier B.V.

  19. Structure-based optics of centric diatom frustules: modulation of the in vivo light field for efficient diatom photosynthesis.

    Science.gov (United States)

    Goessling, Johannes W; Su, Yanyan; Cartaxana, Paulo; Maibohm, Christian; Rickelt, Lars F; Trampe, Erik C L; Walby, Sandra L; Wangpraseurt, Daniel; Wu, Xia; Ellegaard, Marianne; Kühl, Michael

    2018-07-01

    The optical properties of diatom silicate frustules inspire photonics and nanotechnology research. Whether light interaction with the nano-structure of the frustule also affects diatom photosynthesis has remained unclear due to lack of information on frustule optical properties under more natural conditions. Here we demonstrate that the optical properties of the frustule valves in water affect light harvesting and photosynthesis in live cells of centric diatoms (Coscinodiscus granii). Microscale cellular mapping of photosynthesis around localized spot illumination demonstrated optical coupling of chloroplasts to the valve wall. Photonic structures of the three-layered C. granii valve facilitated light redistribution and efficient photosynthesis in cell regions distant from the directly illuminated area. The different porous structure of the two sides of the valve exhibited photon trapping and forward scattering of blue light enhancing photosynthetic active radiation inside the cell. Photonic structures of diatom frustules thus alter the cellular light field with implications on diatom photobiology. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

  20. Nanostructured silicate polymer concrete

    Directory of Open Access Journals (Sweden)

    Figovskiy Oleg L'vovich

    2014-03-01

    Full Text Available It has been known that acid-resistant concretes on the liquid glass basis have high porosity (up to 18~20 %, low strength and insufficient water resistance. Significant increasing of silicate matrix strength and density was carried out by incorporation of special liquid organic alkali-soluble silicate additives, which block superficial pores and reduce concrete shrinkage deformation. It was demonstrated that introduction of tetrafurfuryloxisilane additive sharply increases strength, durability and shock resistance of silicate polymer concrete in aggressive media. The experiments showed, that the strength and density of silicate polymer concrete increase in case of decreasing liquid glass content. The authors obtained optimal content of silicate polymer concrete, which possesses increased strength, durability, density and crack-resistance. Diffusive permeability of concrete and its chemical resistance has been investigated in various corroding media.

  1. Dynamics of late spring and summer phytoplankton communities on Georges Bank, with emphasis on diatoms, Alexandrium spp., and other dinoflagellates

    Science.gov (United States)

    Gettings, Rachel M.; Townsend, David W.; Thomas, Maura A.; Karp-Boss, Lee

    2014-05-01

    We analyzed the distribution, abundance, and succession patterns of major phytoplankton taxa on Georges Bank in relation to hydrography, nutrients, and size-fractionated chlorophyll concentrations (>20 μm; Gymnodinium spp., and Prorocentrum spp., had become more abundant. Patches of regenerated silicate during the June-July period appeared to support a post-spring-bloom diatom community on the central crest of the Bank (total diatom cell densities >180,000 cellsl-1) of Leptocylindrus spp., Dactyliosolen spp., and Guinardia flaccida. Multivariate statistical analyses of phytoplankton taxa and station locations revealed distinct assemblages of diatom and dinoflagellate taxa on the Bank throughout the late spring and summer. Results are interpreted in the ecological context of earlier-reported laboratory culture experiments on the competitive interactions between Alexandrium fundyense and diatoms.

  2. The effect of antibiotics on diatom communities

    Digital Repository Service at National Institute of Oceanography (India)

    DeCosta, P.M.; Anil, A.C.

    Effect of antibiotics (penicillin (P), streptomycin (S) and chloramphenicol (C)) on benthic diatom communities was evaluated using a modified extinction–dilution method. The high antibiotic combinations (2PSC and PSC) reduced diatoms by 99...

  3. Diatom genomics: genetic acquisitions and mergers.

    Science.gov (United States)

    Nisbet, R Ellen R; Kilian, Oliver; McFadden, Geoffrey I

    2004-12-29

    Diatom algae arose by two-step endosymbiosis. The complete genome of the diatom Thalassiosira pseudonana has now been sequenced, allowing us to reconstruct the remarkable intracellular gene transfers that occurred during this convoluted cellular evolution.

  4. Diatomic interaction potential theory applications

    CERN Document Server

    Goodisman, Jerry

    2013-01-01

    Diatomic Interaction Potential Theory, Volume 2: Applications discusses the variety of applicable theoretical material and approaches in the calculations for diatomic systems in their ground states. The volume covers the descriptions and illustrations of modern calculations. Chapter I discusses the calculation of the interaction potential for large and small values of the internuclear distance R (separated and united atom limits). Chapter II covers the methods used for intermediate values of R, which in principle means any values of R. The Hartree-Fock and configuration interaction schemes des

  5. Biogenic silica microfossils in sediments of the Permian - Carboniferous Unayzah Formation, Saudi Arabia

    NARCIS (Netherlands)

    Garming, J.F.L.; Franks, S.G.; Cremer, H.; Abbink, O.A.

    2010-01-01

    Biogenic silica particles (BSPs) have been discovered in sediments of the Permian - Carboniferous Unayzah Formation of Saudi Arabia. The BSPs are extracted from sediments that are generally barren of macro- or microfossils. BSPs have been found in the Basal Khuff Clastics (BKC), and the Unayzah A,

  6. Automated measurement of diatom size

    Science.gov (United States)

    Spaulding, Sarah A.; Jewson, David H.; Bixby, Rebecca J.; Nelson, Harry; McKnight, Diane M.

    2012-01-01

    Size analysis of diatom populations has not been widely considered, but it is a potentially powerful tool for understanding diatom life histories, population dynamics, and phylogenetic relationships. However, measuring cell dimensions on a light microscope is a time-consuming process. An alternative technique has been developed using digital flow cytometry on a FlowCAM® (Fluid Imaging Technologies) to capture hundreds, or even thousands, of images of a chosen taxon from a single sample in a matter of minutes. Up to 30 morphological measures may be quantified through post-processing of the high resolution images. We evaluated FlowCAM size measurements, comparing them against measurements from a light microscope. We found good agreement between measurement of apical cell length in species with elongated, straight valves, including small Achnanthidium minutissimum (11-21 µm) and largeDidymosphenia geminata (87–137 µm) forms. However, a taxon with curved cells, Hannaea baicalensis (37–96 µm), showed differences of ~ 4 µm between the two methods. Discrepancies appear to be influenced by the choice of feret or geodesic measurement for asymmetric cells. We describe the operating conditions necessary for analysis of size distributions and present suggestions for optimal instrument conditions for size analysis of diatom samples using the FlowCAM. The increased speed of data acquisition through use of imaging flow cytometers like the FlowCAM is an essential step for advancing studies of diatom populations.

  7. Spatio-temporal distribution of the dominant Diatom and Dinoflagellate species in the Bay of Tunis (SW Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    O. DALY YAHIA-KEFI

    2005-06-01

    Full Text Available Microphytoplankton composition and its relationships with hydrology and nutrient distributions were investigated over 24 months (December 1993 - November 1995 in the Bay of Tunis ( SW Mediterranean Sea. A new index, the ‘Specific Preference Index’ (SPI obtained by computing the median value of each parameter weighed by the numerical value of each species density was developed. Using this index, the relationships between each species and temperature, salinity and major nutrients were analysed. The distribution of chlorophyll a did not show a clear correlation with microplankton abundance suggesting that other factors contribute to chlorophyll concentration, such as smaller phytoplankton size fractions or detritus. The winter-spring diatom blooms did not show a regular pattern during both years. High nutrient inputs in late summer, associated with mild meteorological conditions, contributed to the development of a large diatom bloom in autumn 1995 where significant silicate depletion was witnessed. Generally, diatoms were more stenotherm than dinoflagellates in the Bay, whereas dinoflagellates were more stenohaline than diatoms. The statistical analyses showed that the two species, Bellerochea horologicalis , and Lithodesmioides polymorpha, var., tunisiense, appeared in a wide range of environmental conditions. An excess of phosphateversus nitrate appeared to be associated with red tides of, Gymnodinium spp, whereas Peridinium quinquecorne, showed the opposite. Phosphate concentrations appear to be crucial in this coastal environment, where diatom blooms are often limited by low silicate availability.

  8. Composite nanoparticles: A new way to siliceous materials and a model of biosilica synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Annenkov, Vadim V., E-mail: annenkov@lin.irk.ru [Limnological Institute, Siberian Branch of the Russian Academy of Sciences, Irkutsk 664033 (Russian Federation); Pal' shin, Viktor A.; Verkhozina, Olga N. [Limnological Institute, Siberian Branch of the Russian Academy of Sciences, Irkutsk 664033 (Russian Federation); Larina, Lyudmila I. [A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk 664033 (Russian Federation); Danilovtseva, Elena N. [Limnological Institute, Siberian Branch of the Russian Academy of Sciences, Irkutsk 664033 (Russian Federation)

    2015-09-01

    A new polyampholyte based on poly (acrylic acid) which bears pendant polyamine oligomeric chains (average number of the nitrogen atoms is 11.2) is obtained. This polymer is a model of silaffins – proteins playing important role in formation of siliceous structures in diatom algae and sponges. The polymer catalyses condensation of silicic acid. The obtained solutions contain oligosilicates coordinated with the polymer chains. The action of 50,000 g gravity on this solution results in concentrating-induced condensation of the pre-condensed siliceous oligomers. The obtained solid silica contains 4% admixture of the organic polymer which is close to the silica from diatom frustules. These results confirm the hypothesis about formation of biosilica under the action of desiccation agent, e.g. aquaporins. The formation of solid substances during centrifugation of solutions containing soluble oligomers is a new promising approach to inorganic and composite materials which allows to work in aqueous medium and to reuse the organic polymer. - Highlights: • A polyampholyte with pendant polyamine chains is obtained. • The polymer catalyses condensation of silicic acid giving stable solutions. • Gravity-induced (50,000 g) formation of solid silica was observed in these solutions. • The obtained silica is close to biosilica from diatom frustules. • A new approach to inorganic and composite materials is proposed.

  9. Composite nanoparticles: A new way to siliceous materials and a model of biosilica synthesis

    International Nuclear Information System (INIS)

    Annenkov, Vadim V.; Pal'shin, Viktor A.; Verkhozina, Olga N.; Larina, Lyudmila I.; Danilovtseva, Elena N.

    2015-01-01

    A new polyampholyte based on poly (acrylic acid) which bears pendant polyamine oligomeric chains (average number of the nitrogen atoms is 11.2) is obtained. This polymer is a model of silaffins – proteins playing important role in formation of siliceous structures in diatom algae and sponges. The polymer catalyses condensation of silicic acid. The obtained solutions contain oligosilicates coordinated with the polymer chains. The action of 50,000 g gravity on this solution results in concentrating-induced condensation of the pre-condensed siliceous oligomers. The obtained solid silica contains 4% admixture of the organic polymer which is close to the silica from diatom frustules. These results confirm the hypothesis about formation of biosilica under the action of desiccation agent, e.g. aquaporins. The formation of solid substances during centrifugation of solutions containing soluble oligomers is a new promising approach to inorganic and composite materials which allows to work in aqueous medium and to reuse the organic polymer. - Highlights: • A polyampholyte with pendant polyamine chains is obtained. • The polymer catalyses condensation of silicic acid giving stable solutions. • Gravity-induced (50,000 g) formation of solid silica was observed in these solutions. • The obtained silica is close to biosilica from diatom frustules. • A new approach to inorganic and composite materials is proposed.

  10. Molecular Tools for the Selective Detection of Nine Diatom Species Biomarkers of Various Water Quality Levels

    Directory of Open Access Journals (Sweden)

    Lucia Cimarelli

    2015-05-01

    Full Text Available Our understanding of the composition of diatom communities and their response to environmental changes is currently limited by laborious taxonomic identification procedures. Advances in molecular technologies are expected to contribute more efficient, robust and sensitive tools for the detection of these ecologically relevant microorganisms. There is a need to explore and test phylogenetic markers as an alternative to the use of rRNA genes, whose limited sequence divergence does not allow the accurate discrimination of diatoms at the species level. In this work, nine diatom species belonging to eight genera, isolated from epylithic environmental samples collected in central Italy, were chosen to implement a panel of diatoms covering the full range of ecological status of freshwaters. The procedure described in this work relies on the PCR amplification of specific regions in two conserved diatom genes, elongation factor 1-a (eEF1-a and silicic acid transporter (SIT, as a first step to narrow down the complexity of the targets, followed by microarray hybridization experiments. Oligonucleotide probes with the potential to discriminate closely related species were designed taking into account the genetic polymorphisms found in target genes. These probes were tested, refined and validated on a small-scale prototype DNA chip. Overall, we obtained 17 highly specific probes targeting eEF1-a and SIT, along with 19 probes having lower discriminatory power recognizing at the same time two or three species. This basic array was validated in a laboratory setting and is ready for tests with crude environmental samples eventually to be scaled-up to include a larger panel of diatoms. Its possible use for the simultaneous detection of diatoms selected from the classes of water quality identified by the European Water Framework Directive is discussed.

  11. Luminescence properties of a nanoporous freshwater diatom.

    Science.gov (United States)

    Goswami, Bondita; Choudhury, Amarjyoti; Buragohain, Alak K

    2012-01-01

    Freshwater diatom frustules show special optical properties. In this paper we observed luminescence properties of the freshwater diatom Cyclotella meneghiniana. To confirm the morphological properties we present scanning electron microscopy (SEM) images. X-ray diffraction (XRD) studies were carried out to visualize the structural properties of the frustules, confirming that silica present in diatom frustules crystallizes in an α-quartz structure. Study of the optical properties of the silica frustules of diatoms using ultra-violet-visible (UV-vis) spectroscopy and photoluminescence spectroscopy confirmed that the diatom C. meneghiniana shows luminescence in the blue region of the electromagnetic spectrum when irradiated with UV light. This property of diatoms can be exploited to obtain many applications in day-to-day life. Also, using time-resolved photoluminescence spectroscopy (TRPL) it was confirmed that this species of diatom shows bi-exponential decay. Copyright © 2011 John Wiley & Sons, Ltd.

  12. Iron Availability Influences Silicon Isotope Fractionation in Two Southern Ocean Diatoms (Proboscia inermis and Eucampia antarctica and a Coastal Diatom (Thalassiosira pseudonana

    Directory of Open Access Journals (Sweden)

    Scott Meyerink

    2017-07-01

    Full Text Available The fractionation of silicon (Si isotopes was measured in two Southern Ocean diatoms (Proboscia inermis and Eucampia Antarctica and a coastal diatom (Thalassiosira pseudonana that were grown under varying iron (Fe concentrations. Varying Fe concentrations had no effect on the Si isotope enrichment factor (ε in T. pseudonana, whilst E. Antarctica and P. inermis exhibited significant variations in the value of ε between Fe-replete and Fe-limited conditions. Mean ε values in P. inermis and E. Antarctica decreased from (± 1SD −1.11 ± 0.15‰ and −1.42 ± 0.41 ‰ (respectively under Fe-replete conditions, to −1.38 ± 0.27 ‰ and −1.57 ± 0.5 ‰ (respectively under Fe-limiting conditions. These variations likely arise from adaptations in diatoms arising from the nutrient status of their environment. T. pseudonana is a coastal clone typically accustomed to low Si but high Fe conditions whereas E. Antarctica and P. inermis are typically accustomed to High Si, High nitrate low Fe conditions. Growth induced variations in silicic acid (Si(OH4 uptake arising from Fe-limitation is the likely mechanism leading to Si-isotope variability in E. Antarctica and P. inermis. The multiplicative effects of species diversity and resource limitation (e.g., Fe on Si-isotope fractionation in diatoms can potentially alter the Si-isotope composition of diatom opal in diatamaceous sediments and sea surface Si(OH4. This work highlights the need for further in vitro studies into intracellular mechanisms involved in Si(OH4 uptake, and the associated pathways for Si-isotope fractionation in diatoms.

  13. Digital database of microfossil localities in Alameda and Contra Costa Counties, California

    Science.gov (United States)

    McDougall, Kristin; Block, Debra L.

    2014-01-01

    The eastern San Francisco Bay region (Contra Costa and Alameda Counties, California) is a geologically complex area divided by faults into a suite of tectonic blocks. Each block contains a unique stratigraphic sequence of Tertiary sediments that in most blocks unconformably overlie Mesozoic sediments. Age and environmental interpretations based on analysis of microfossil assemblages are key factors in interpreting geologic history, structure, and correlation of each block. Much of this data, however, is distributed in unpublished internal reports and memos, and is generally unavailable to the geologic community. In this report the U.S. Geological Survey microfossil data from the Tertiary sediments of Alameda and Contra Costa counties are analyzed and presented in a digital database, which provides a user-friendly summary of the micropaleontologic data, locality information, and biostratigraphic and ecologic interpretations.

  14. Search for supernova {sup 60}Fe in the Earth's microfossil record

    Energy Technology Data Exchange (ETDEWEB)

    Bishop, S.; Ludwig, P.; Egli, R.; Faestermann, T.; Korschinek, G.; Rugel, G. [Technische Universitaet Muenchen, James Franck Str. 1, D-85748 Garching (Germany); Department of Earth and Environmental Sciences, Ludwig-Maximilians University, Theresienstrasse 41 80333 Munich (Germany); Technische Universitaet Muenchen, James Franck Str. 1, D-85748 Garching (Germany); Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstra. 400, D-01328 Dresden (Germany)

    2012-11-12

    Approximately 2.8 Myr before the present our planet was subjected to the debris of a supernova explosion. The terrestrial proxy for this event was the discovery of live atoms of {sup 60}Fe in a deep-sea ferromanganese crust. The signature for this supernova event should also reside in magnetite (Fe{sub 3}O{sub 4}) microfossils produced by magnetotactic bacteria extant at the time of the Earth-supernova interaction, provided the bacteria preferentially uptake iron from fine-grained iron oxides and ferric hydroxides. Using empirically derived microfossil concentrations in a deep-sea drill core, we deduce a conservative estimate of the {sup 60}Fe fraction as {sup 60}Fe/Fe Almost-Equal-To 3.6 Multiplication-Sign 10{sup -15}. This value sits comfortably within the sensitivity limit of present accelerator mass spectrometry capabilities.

  15. Using Soft Sculpture Microfossils and Other Crafted Models to Teach Geoscience

    Science.gov (United States)

    Spinak, N. R.

    2017-12-01

    For the past 5 years, the International Ocean Discovery Program (IODP) has been using the author's sewn models of microfossils to help learners understand the shapes and design of these tiny fossils. These tactile objects make the study of ancient underwater life more tangible. Multiple studies have shown that interactive models can help many learners understand science. The Montessori and Waldorf education programs are based in large part on earlier insights into meeting these needs. The act of drawing has been an essential part of medical education. The STEAM (Science, Technology, Engineering, Arts and Math) movement has advocated for STEM supporters to recognize the inseparability of science and art. This presentation describes how the author's knitted or sewn models of microfossils incorporate art and design into geoscience education. The geoscience research and art processes used in developing and creating these educational soft sculptures will be described. In multiple entry points to science study, specific reciprocal benefits to boundary crossing among the arts and sciences for those who have primary talents in a particular area of study will be discussed. Geoscience education can benefit from using art and craft items such as models. Many websites now offer soft sculptures for biology study such as organs and germs (e.g. (https://www.giantmicrobes.com/us/main/nasty-germs). The Wortheim project involving community and crochet is another approach (http://crochetcoralreef.org/). These tactile artifacts give learners an entry-level experience with biology. Three dimensional models are multisensory. The enlarged manipulative microfossil models invite learners to make comparisons and gain insights when microscopes are not available or appropriate for the audience. Adding the physical involvement of creating a microfossil yourself increases the multi-sensory experience even further. Learning craft skills extends the cross-cutting concepts of the NGSS to a mutual

  16. Sampler collection gadget for epilithic diatoms.

    Science.gov (United States)

    Salomoni, S E; Torgan, L C; Rocha, O

    2007-11-01

    This work present a new gadget for sampling epilithic diatoms from both lentic and lotic enviroments. The sampler consists of a polystyrene cylinder, left to float on the surface of the water, to which stone substrates are attached. This epilithic diatom sampler (EDS) can be used to detect spatial and temporal richness and density variation in the study of the diatom community, as well as in water quality monitoring.

  17. Sampler collection gadget for epilithic diatoms

    Directory of Open Access Journals (Sweden)

    SE. Salomoni

    Full Text Available This work present a new gadget for sampling epilithic diatoms from both lentic and lotic enviroments. The sampler consists of a polystyrene cylinder, left to float on the surface of the water, to which stone substrates are attached. This epilithic diatom sampler (EDS can be used to detect spatial and temporal richness and density variation in the study of the diatom community, as well as in water quality monitoring.

  18. Thick-shelled, grazer-protected diatoms decouple ocean carbon and silicon cycles in the iron-limited Antarctic Circumpolar Current

    Science.gov (United States)

    Assmy, Philipp; Smetacek, Victor; Montresor, Marina; Klaas, Christine; Henjes, Joachim; Strass, Volker H.; Arrieta, Jesús M.; Bathmann, Ulrich; Berg, Gry M.; Breitbarth, Eike; Cisewski, Boris; Friedrichs, Lars; Fuchs, Nike; Herndl, Gerhard J.; Jansen, Sandra; Krägefsky, Sören; Latasa, Mikel; Peeken, Ilka; Röttgers, Rüdiger; Scharek, Renate; Schüller, Susanne E.; Steigenberger, Sebastian; Webb, Adrian; Wolf-Gladrow, Dieter

    2013-01-01

    Diatoms of the iron-replete continental margins and North Atlantic are key exporters of organic carbon. In contrast, diatoms of the iron-limited Antarctic Circumpolar Current sequester silicon, but comparatively little carbon, in the underlying deep ocean and sediments. Because the Southern Ocean is the major hub of oceanic nutrient distribution, selective silicon sequestration there limits diatom blooms elsewhere and consequently the biotic carbon sequestration potential of the entire ocean. We investigated this paradox in an in situ iron fertilization experiment by comparing accumulation and sinking of diatom populations inside and outside the iron-fertilized patch over 5 wk. A bloom comprising various thin- and thick-shelled diatom species developed inside the patch despite the presence of large grazer populations. After the third week, most of the thinner-shelled diatom species underwent mass mortality, formed large, mucous aggregates, and sank out en masse (carbon sinkers). In contrast, thicker-shelled species, in particular Fragilariopsis kerguelensis, persisted in the surface layers, sank mainly empty shells continuously, and reduced silicate concentrations to similar levels both inside and outside the patch (silica sinkers). These patterns imply that thick-shelled, hence grazer-protected, diatom species evolved in response to heavy copepod grazing pressure in the presence of an abundant silicate supply. The ecology of these silica-sinking species decouples silicon and carbon cycles in the iron-limited Southern Ocean, whereas carbon-sinking species, when stimulated by iron fertilization, export more carbon per silicon. Our results suggest that large-scale iron fertilization of the silicate-rich Southern Ocean will not change silicon sequestration but will add carbon to the sinking silica flux. PMID:24248337

  19. Stratigraphic and microfossil evidence for a 4500-year history of Cascadia subduction zone earthquakes and tsunamis at Yaquina River estuary, Oregon, USA

    Science.gov (United States)

    Graehl, Nicholas A; Kelsey, Harvey M.; Witter, Robert C.; Hemphill-Haley, Eileen; Engelhart, Simon E.

    2015-01-01

    The Sallys Bend swamp and marsh area on the central Oregon coast onshore of the Cascadia subduction zone contains a sequence of buried coastal wetland soils that extends back ∼4500 yr B.P. The upper 10 of the 12 soils are represented in multiple cores. Each soil is abruptly overlain by a sandy deposit and then, in most cases, by greater than 10 cm of mud. For eight of the 10 buried soils, times of soil burial are constrained through radiocarbon ages on fine, delicate detritus from the top of the buried soil; for two of the buried soils, diatom and foraminifera data constrain paleoenvironment at the time of soil burial.We infer that each buried soil represents a Cascadia subduction zone earthquake because the soils are laterally extensive and abruptly overlain by sandy deposits and mud. Preservation of coseismically buried soils occurred from 4500 yr ago until ∼500–600 yr ago, after which preservation was compromised by cessation of gradual relative sea-level rise, which in turn precluded drowning of marsh soils during instances of coseismic subsidence. Based on grain-size and microfossil data, sandy deposits overlying buried soils accumulated immediately after a subduction zone earthquake, during tsunami incursion into Sallys Bend. The possibility that the sandy deposits were sourced directly from landslides triggered upstream in the Yaquina River basin by seismic shaking was discounted based on sedimentologic, microfossil, and depositional site characteristics of the sandy deposits, which were inconsistent with a fluvial origin. Biostratigraphic analyses of sediment above two buried soils—in the case of two earthquakes, one occurring shortly after 1541–1708 cal. yr B.P. and the other occurring shortly after 3227–3444 cal. yr B.P.—provide estimates that coseismic subsidence was a minimum of 0.4 m. The average recurrence interval of subduction zone earthquakes is 420–580 yr, based on an ∼3750–4050-yr-long record and seven to nine interearthquake

  20. Diatom-inspired templates for 3D replication: natural diatoms versus laser written artificial diatoms

    International Nuclear Information System (INIS)

    Belegratis, M R; Schmidt, V; Nees, D; Stadlober, B; Hartmann, P

    2014-01-01

    The diatoms are ubiquitous, exist in large numbers and show a great diversity of features on their porous silica structures. Therefore, they inspire the fabrication of nanostructured templates for nanoimprint processes (NIL), where large structured areas with nanometer precision are required. In this study, two approaches regarding the respective challenges and potential exploitations are followed and discussed: the first one takes advantage of a template that is directly made of natural occurring diatoms. Here, two replication steps via soft lithography are needed to obtain a template which is subsequently used for NIL. The second approach exploits the technical capabilities of the precise 3D laser lithography (3DLL) based on two-photon polymerization of organic materials. This method enables the fabrication of arbitrary artificial diatom-inspired micro- and nanostructures and the design of an inverse structure. Therefore, only one replication step is needed to obtain a template for NIL. In both approaches, a replication technique for true 3D structures is shown. (paper)

  1. The genome of the diatom Thalassiosira pseudonana: Ecology,evolution, and metabolism

    Energy Technology Data Exchange (ETDEWEB)

    Ambrust, E.V.; Berges, J.; Bowler, C.; Green, B.; Martinez, D.; Putnam, N.; Zhou, S.; Allen, A.; Apt, K.; Bechner, M.; Brzezinski, M.; Chaal, B.; Chiovitti, A.; Davis, A.; Goodstein, D.; Hadi, M.; Hellsten,U.; Hildebrand, M.; Jenkins, B.; Jurka, J.; Kapitonov, V.; Kroger, N.; Lau, W.; Lane, T.; Larimer, F.; Lippmeier, J.; Lucas, S.; Medina, M.; Montsant, A.; Obornik, M.; Parker, M. Schnitzler; Palenik, B.; Pazour,G.; Richardson, P.; Rynearson, T.; Saito, M.; Schwartz, D.; Thamatrakoln,K.; Valentin, K.; Vardi, A.; Wilkerson, F.; Rokhsar, D.; Vardi, A.; Wilkerson, F.P.; Rokhsar, D.S.

    2004-09-01

    Diatoms are unicellular algae with plastids acquired by secondary endosymbiosis. They are responsible for {approx}20% of global carbon fixation. We report the 34 Mbp draft nuclear genome of the marine diatom, Thalassiosira pseudonana and its 129 Kbp plastid and 44 Kbp mitochondrial genomes. Sequence and optical restriction mapping revealed 24 diploid nuclear chromosomes. We identified novel genes for silicic acid transport and formation of silica-based cell walls, high-affinity iron uptake, biosynthetic enzymes for several types of polyunsaturated fatty acids, utilization of a range of nitrogenous compounds and a complete urea cycle, all attributes that allow diatoms to prosper in the marine environment. Diatoms are unicellular, photosynthetic, eukaryotic algae found throughout the world's oceans and freshwater systems. They form the base of short, energetically-efficient food webs that support large-scale coastal fisheries. Photosynthesis by marine diatoms generates as much as 40% of the 45-50 billion tonnes of organic carbon produced each year in the sea (1), and their role in global carbon cycling is predicted to be comparable to that of all terrestrial rainforests combined (2, 3). Over geological time, diatoms may have influenced global climate by changing the flux of atmospheric carbon dioxide into the oceans (4). A defining feature of diatoms is their ornately patterned silicified cell wall or frustule, which displays species-specific nano-structures of such fine detail that diatoms have long been used to test the resolution of optical microscopes. Recent attention has focused on biosynthesis of these nano-structures as a paradigm for future silica nanotechnology (5). The long history (over 180 million years) and dominance of diatoms in the oceans is reflected by their contributions to vast deposits of diatomite, most cherts and a significant fraction of current petroleum reserves (6). As photosynthetic heterokonts, diatoms reflect a fundamentally

  2. The influence of environmental variability on the biogeography of coccolithophores and diatoms in the Great Calcite Belt

    Science.gov (United States)

    Smith, Helen E. K.; Poulton, Alex J.; Garley, Rebecca; Hopkins, Jason; Lubelczyk, Laura C.; Drapeau, Dave T.; Rauschenberg, Sara; Twining, Ben S.; Bates, Nicholas R.; Balch, William M.

    2017-11-01

    The Great Calcite Belt (GCB) of the Southern Ocean is a region of elevated summertime upper ocean calcite concentration derived from coccolithophores, despite the region being known for its diatom predominance. The overlap of two major phytoplankton groups, coccolithophores and diatoms, in the dynamic frontal systems characteristic of this region provides an ideal setting to study environmental influences on the distribution of different species within these taxonomic groups. Samples for phytoplankton enumeration were collected from the upper mixed layer (30 m) during two cruises, the first to the South Atlantic sector (January-February 2011; 60° W-15° E and 36-60° S) and the second in the South Indian sector (February-March 2012; 40-120° E and 36-60° S). The species composition of coccolithophores and diatoms was examined using scanning electron microscopy at 27 stations across the Subtropical, Polar, and Subantarctic fronts. The influence of environmental parameters, such as sea surface temperature (SST), salinity, carbonate chemistry (pH, partial pressure of CO2 (pCO2), alkalinity, dissolved inorganic carbon), macronutrients (nitrate + nitrite, phosphate, silicic acid, ammonia), and mixed layer average irradiance, on species composition across the GCB was assessed statistically. Nanophytoplankton (cells 2-20 µm) were the numerically abundant size group of biomineralizing phytoplankton across the GCB, with the coccolithophore Emiliania huxleyi and diatoms Fragilariopsis nana, F. pseudonana, and Pseudo-nitzschia spp. as the most numerically dominant and widely distributed. A combination of SST, macronutrient concentrations, and pCO2 provided the best statistical descriptors of the biogeographic variability in biomineralizing species composition between stations. Emiliania huxleyi occurred in silicic acid-depleted waters between the Subantarctic Front and the Polar Front, a favorable environment for this species after spring diatom blooms remove silicic acid

  3. Cellular metabolic responses of the marine diatom Pseudo-nitzschia multiseries associated with cell wall formation.

    Science.gov (United States)

    Xu, Bin; Luo, Chun-Shan; Liang, Jun-Rong; Chen, Dan-Dan; Zhuo, Wen-Hao; Gao, Ya-Hui; Chen, Chang-Ping; Song, Si-Si

    2014-08-01

    In this study a comparative proteomics approach involving a mass spectrometric analysis of synchronized cells was employed to investigate the cellular-level metabolic mechanisms associated with siliceous cell wall formation in the pennate diatom Pseudo-nitzschia multiseries. Cultures of P. multiseries were synchronized using the silicate limitation method. Approximately 75% of cells were arrested at the G2+M phase of the cell cycle after 48 h of silicate starvation. The majority of cells progressed to new valve synthesis within 5h of silicon replenishment. We compared the proteome of P. multiseries at 0, 4, 5, and 6h of synchronization progress upon silicon replenishment using two-dimensional gel electrophoresis. Forty-eight differentially expressed protein spots were identified in abundance (greater than two-fold change; Pwall formation. The proteomic profile analysis suggests that P. multiseries most likely employs multiple synergistic biochemical mechanisms for cell wall formation. These results improve our understanding of the molecular mechanisms underlying silicon cell wall formation and enhance our understanding of the important role played by diatoms in silicon biogeochemical cycling. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. Silicates in Alien Asteroids

    Science.gov (United States)

    2009-01-01

    This plot of data from NASA's Spitzer Space Telescopes shows that asteroid dust around a dead 'white dwarf' star contains silicates a common mineral on Earth. The data were taken primarily by Spitzer's infrared spectrograph, an instrument that breaks light apart into its basic constituents. The yellow dots show averaged data from the spectrograph, while the orange triangles show older data from Spitzer's infrared array camera. The white dwarf is called GD 40.

  5. Relationship between diatom communities and environmental ...

    African Journals Online (AJOL)

    ajl yemi

    2011-11-30

    Nov 30, 2011 ... The relationship between diatom species and measured environmental variables was explored at different sites of Honghe wetland region located in northeastern China. Planktonic and epiphytic diatom assemblages in the wetland were identified from May to October of 2007 and 2008. Their relationships.

  6. Colloquium on diatom-copepod interactions

    DEFF Research Database (Denmark)

    Paffenhofer, G.A.; Ianora, A.; Miralto, A.

    2005-01-01

    in situ were also addressed. During the plenary session, the most recent advances on this topic were presented. The plenary session was followed by 3 working groups on (1) production of aldehydes by phytoplankton, (2) toxic and nutritional effects of diatoms on zooplankton, and (3) the chemistry of diatom...

  7. Relationship between diatom communities and environmental ...

    African Journals Online (AJOL)

    Abstract. The relationship between diatom species and measured environmental variables was explored at different sites of Honghe wetland region located in northeastern China. Planktonic and epiphytic diatom assemblages in the wetland were identified from May to October of 2007 and 2008. Their relationships with ...

  8. Displacement functions for diatomic materials

    International Nuclear Information System (INIS)

    Panrkin, D.M.; Coulter, C.A.

    1979-01-01

    An extension of the methods of Lindhard et at. was used to calculate the total displacement function n/sub ij/(E) for a number of diatomic materials, where n/sub ij/(E) is defined to be the average number of atoms of type j which are displaced from their sites in a displacement cascade initiated by a PKA of type i and energy E. From the n/sub ij/(E) one can calculate the fraction n/sub ij/(E) of the displacements produced by a type i PKA with energy E which are of type j. Values of the n/sub ij/ for MgO, CaO, Al 2 O 3 , and TaO are presented. It is shown that for diatomic materials with mass ratios reasonably near one (e.g., MgO, Al 2 O 3 ) and equal displacement thresholds for the two species the n/sub ij/ become independent of the PKA type i at energies only a few times threshold. However, for larger mass ratios the n/sub ij/ do not become independent of i until much larger, energies are reached - e.g. > 10 5 eV for TaO. In addition, it is found that the n/sub ij/ depend sensitively on the displacement thresholds, with very dramatic charges occuring when the two thresholds become significantly different from one another

  9. Thermal maturity of Tasmanites microfossils from confocal laser scanning fluorescence microscopy

    Science.gov (United States)

    Hackley, Paul C.; Kus, Jolanta

    2015-01-01

    We report here, for the first time, spectral properties of Tasmanites microfossils determined by confocal laser scanning fluorescence microscopy (CLSM, using Ar 458 nm excitation). The Tasmanites occur in a well-characterized natural maturation sequence (Ro 0.48–0.74%) of Devonian shale (n = 3 samples) from the Appalachian Basin. Spectral property λmax shows excellent agreement (r2 = 0.99) with extant spectra from interlaboratory studies which used conventional fluorescence microscopy techniques. This result suggests spectral measurements from CLSM can be used to infer thermal maturity of fluorescent organic materials in geologic samples. Spectra of regions with high fluorescence intensity at fold apices and flanks in individual Tasmanites are blue-shifted relative to less-deformed areas in the same body that have lower fluorescence intensity. This is interpreted to result from decreased quenching moiety concentration at these locations, and indicates caution is needed in the selection of measurement regions in conventional fluorescence microscopy, where it is common practice to select high intensity regions for improved signal intensity and better signal to noise ratios. This study also documents application of CLSM to microstructural characterization of Tasmanites microfossils. Finally, based on an extant empirical relation between conventional λmax values and bitumen reflectance, λmax values from CLSM of Tasmanites microfossils can be used to calculate a bitumen reflectance equivalent value. The results presented herein can be used as a basis to broaden the future application of CLSM in the geological sciences into hydrocarbon prospecting and basin analysis.

  10. Formation of Calcium Silicates during Ignition of Marine Sediments and its Implication on the State of Silica on the Sea Floor

    International Nuclear Information System (INIS)

    Duursma, E.K.; Bosch, C.J.; Eisma, D.

    1976-01-01

    Anomalies in the formation of calcium silicates in various marine sediment samples were observed on ignition at 800°C. The hypothesis is put forward that silica, originating from the land and from marine diatoms, undergoes a slow hydrolysis in the seabed and becomes more reactive. (author)

  11. Reproductive cyst and operculum formation in the Cambrian-Ordovician galeate-plexus microfossils

    DEFF Research Database (Denmark)

    Agic, Heda; Moczydlowska, Malgorzata; Canfield, Donald Eugene

    2016-01-01

    Unicellular organic-walled microfossils from the Cambrian-Ordovician transition in Estonia (ca. 490-480million years ago) exhibit rare characters reflecting their function as reproductive algal cysts. The studied assemblages record the evolutionary history of phytoplankton in the early Palaeozoic...... alga Acetabularia (Chlorophyta), which possesses an intrinsic lid-forming apparatus used during the organism's reproductive stage. Based on the observations on the fossil material and studies on the Acetabularia lid formation, we propose a model of operculum formation in the galeate plexus micro-organisms...

  12. Microfossils in the Ordovician erratic boulders from South-western Finland

    Directory of Open Access Journals (Sweden)

    Nõlvak, J.

    1995-12-01

    Full Text Available Chitinozoans, ostracods and acritarchs found in four glacially transported limestone boulders from the south-western coast of Finland have been studied in order to test the usefulness of these microfossil groups in age determinations. Also rare specimens of conodonts, inarticulated brachiopods and foraminifers were found. Baltic limestone (or Östersjö limestone was the most problematic, because only fossils with calcitic or phosphatic shells are preserved. It is concluded that the boulders identified correlate with the Uhaku and Rakvere stages of the Middle Ordovician.

  13. 21 CFR 573.260 - Calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium silicate. 573.260 Section 573.260 Food and... Listing § 573.260 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely used as an anticaking agent in animal feed, provided that the amount of calcium silicate does not...

  14. Picocyanobacteria Dominance in Deep Biomass Layers: Relation to Diatom Presence and Episodic Events.

    Science.gov (United States)

    Aguilar, C.; Cuhel, R. L.

    2016-02-01

    In Offshore Marine and Large Lake Waters, most of the biomass and the productivity of phytoplankton occur below surface observation capabilities. Sub-mixed layer phytoplankton populations develop, increase, persist, and decay in relation to physical structure such as pycnocline density gradients interacting with progressively changing light fields. Basin-scale meteorological events and persistence of major invasive species have also left marks on biogeochemical cycling and ecosystem function in Lake Michigan. Among the former are precipitation and turbulence alterations brought on by unusual winter ice cover and a century-scale flood during 2008. Dampened seasonal silicate cycling indicated a basin-wide reduction of diatom production following mussel establishment. Communities in Lake Michigan shifted from diatom and big cell-dominated to small cell picocyanobacteria-dominated phytoplankton. Picocyanobacteria were beneficiaries of profound oligotrophication of the ecosystem starting in 2003. Photosynthetic parameters of pre-2003 Deep Biomass populations dominated by diatoms were systematically different from the cyanobacterial epoch following quagga mussel establishment and increase in depth of 1% incident light to 50-60m. Deep cyanobacterial production has now often been on the same scale as overlying waters. Photophysiology changes in a smooth depth gradient in this clear water as opposed to previous abrupt transition to shade adaptation. Among these many physicochemical permutations, community structure has consistently been a tradeoff between diatoms and picocyanobacteria. Opposing fluctuations of biomass favor one or the other on seasonal time frames of sequential years, with a complete system reset between each (winter mixing). For the Great Flood example, diatom surface blooms increased light extinction and drove the deep biomass maximum up - as populations settled into the pycnocline they had already outcompeted the picocyanobacteria. The opposite was true

  15. Diatomic Metasurface for Vectorial Holography.

    Science.gov (United States)

    Deng, Zi-Lan; Deng, Junhong; Zhuang, Xin; Wang, Shuai; Li, Kingfai; Wang, Yao; Chi, Yihui; Ye, Xuan; Xu, Jian; Wang, Guo Ping; Zhao, Rongkuo; Wang, Xiaolei; Cao, Yaoyu; Cheng, Xing; Li, Guixin; Li, Xiangping

    2018-05-09

    The emerging metasurfaces with the exceptional capability of manipulating an arbitrary wavefront have revived the holography with unprecedented prospects. However, most of the reported metaholograms suffer from limited polarization controls for a restrained bandwidth in addition to their complicated meta-atom designs with spatially variant dimensions. Here, we demonstrate a new concept of vectorial holography based on diatomic metasurfaces consisting of metamolecules formed by two orthogonal meta-atoms. On the basis of a simply linear relationship between phase and polarization modulations with displacements and orientations of identical meta-atoms, active diffraction of multiple polarization states and reconstruction of holographic images are simultaneously achieved, which is robust against both incident angles and wavelengths. Leveraging this appealing feature, broadband vectorial holographic images with spatially varying polarization states and dual-way polarization switching functionalities have been demonstrated, suggesting a new route to achromatic diffractive elements, polarization optics, and ultrasecure anticounterfeiting.

  16. Paleobiology of a microfossil of Bambui group (Proterozoico Superior) from Unai region

    International Nuclear Information System (INIS)

    Simonetti, C.; Fairchild, T.R.

    1989-01-01

    A moderately well-preserved and abundant assemblage of coccoidal, bacilliform, and filamentous organic-walled microfossils is here described from black chert colleted near the top of a 30 m-thick expossure of predominantly microbially laminated dolostone from the lower part of the Upper Proterozoic Bambui Group, 12,5 Km NW of Unai, Minas Gerais, south-central Brazil. Of the 11 morphotypes described in this study, small colonies of coccoidal cells (3 species of Myxococcoides; Glenobotrydion aenigmatis Schopf; Form A) are most abundant, followed by tubular filaments (Siphonophycus sp.; 2 species of Eomycetopsis), and, finally, rare, solitary, large (20-40 μ) coccoidal forms (Form C) and a single colony of bacilliform cells (Eosynechococcus moorei Hofmann). The assemblage is dominated by apparently planktonic, small-celled (rarely exceeding 13 μ), colonial coccoidal forms, although filamentous forms may have played a significant role in the local benthos, as suggested by faintly preserved, palimpsestic (or 'ghost') filamentous fabrics and by the presence of poorly preserved tubes of Siphonophycus up to 32 μ in diameter. A single, large pair of thick-walled coccoidal cells (Form B) is here interpreted as a possible acritarch of as yet undetermined biostratigraphic value. The generally small, simple microfossils of this assemblage are similar to elements of the five other Known Bambui assemblages and apparently rather typical of many other late Proterozoic microfloras. (author) [pt

  17. Diatom algae of the Guni river (Pamir)

    International Nuclear Information System (INIS)

    Kurbonova, P.A.; Hisoriev, H.H.

    2006-01-01

    There are presented the dates of the results of diatom algae (Bacillariophyta) of the Gunt river. There was found 107 species and 9 subspecies which belong to 3 classics, 12 ordos, 13 families and 28 genus

  18. Importance of sampling frequency when collecting diatoms

    KAUST Repository

    Wu, Naicheng; Faber, Claas; Sun, Xiuming; Qu, Yueming; Wang, Chao; Ivetic, Snjezana; Riis, Tenna; Ulrich, Uta; Fohrer, Nicola

    2016-01-01

    There has been increasing interest in diatom-based bio-assessment but we still lack a comprehensive understanding of how to capture diatoms’ temporal dynamics with an appropriate sampling frequency (ASF). To cover this research gap, we collected

  19. Analytic vibrational matrix elements for diatomic molecules

    International Nuclear Information System (INIS)

    Bouanich, J.P.; Ogilvie, J.F.; Tipping, R.H.

    1986-01-01

    The vibrational matrix elements and expectation values for a diatomic molecule, including the rotational dependence, are calculated for powers of the reduced displacement in terms of the parameters of the Dunham potential-energy function. (orig.)

  20. Oceanographic and Biogeochemical Insights from Diatom Genomes

    Science.gov (United States)

    Bowler, Chris; Vardi, Assaf; Allen, Andrew E.

    2010-01-01

    Diatoms are the most successful group of eukaryotic phytoplankton in the modern ocean and have risen to dominance relatively quickly over the last 100 million years. Recently completed whole genome sequences from two species of diatom, Thalassiosira pseudonana and Phaeodactylum tricornutum, have revealed a wealth of information about the evolutionary origins and metabolic adaptations that have led to their ecological success. A major finding is that they have incorporated genes both from their endosymbiotic ancestors and by horizontal gene transfer from marine bacteria. This unique melting pot of genes encodes novel capacities for metabolic management, for example, allowing the integration of a urea cycle into a photosynthetic cell. In this review we show how genome-enabled approaches are being leveraged to explore major phenomena of oceanographic and biogeochemical relevance, such as nutrient assimilation and life histories in diatoms. We also discuss how diatoms may be affected by climate change-induced alterations in ocean processes.

  1. An unusual early Holocene diatom event north of the Getz Ice Shelf (Amundsen Sea): Implications for West Antarctic Ice Sheet development

    Science.gov (United States)

    Esper, O.; Gersonde, R.; Hillenbrand, C.; Kuhn, G.; Smith, J.

    2011-12-01

    Modern global change affects not only the polar north but also, and to increasing extent, the southern high latitudes, especially the Antarctic regions covered by the West Antarctic Ice Sheet (WAIS). Consequently, knowledge of the mechanisms controlling past WAIS dynamics and WAIS behaviour at the last deglaciation is critical to predict its development in a future warming world. Geological and palaeobiological information from major drainage areas of the WAIS, like the Amundsen Sea Embayment, shed light on the history of the WAIS glaciers. Sediment records obtained from a deep inner shelf basin north of Getz Ice Shelf document a deglacial warming in three phases. Above a glacial diamicton and a sediment package barren of microfossils that document sediment deposition by grounded ice and below an ice shelf or perennial sea ice cover (possibly fast ice), respectively, a sediment section with diatom assemblages dominated by sea ice taxa indicates ice shelf retreat and seasonal ice-free conditions. This conclusion is supported by diatom-based summer temperature reconstructions. The early retreat was followed by a phase, when exceptional diatom ooze was deposited around 12,500 cal. years B.P. [1]. Microscopical inspection of this ooze revealed excellent preservation of diatom frustules of the species Corethron pennatum together with vegetative Chaetoceros, thus an assemblage usually not preserved in the sedimentary record. Sediments succeeding this section contain diatom assemblages indicating rather constant Holocene cold water conditions with seasonal sea ice. The deposition of the diatom ooze can be related to changes in hydrographic conditions including strong advection of nutrients. However, sediment focussing in the partly steep inner shelf basins cannot be excluded as a factor enhancing the thickness of the ooze deposits. It is not only the presence of the diatom ooze but also the exceptional preservation and the species composition of the diatom assemblage

  2. Soliton solutions in a diatomic lattice system

    International Nuclear Information System (INIS)

    Yajima, Nobuo; Satsuma, Junkichi.

    1979-04-01

    A continuum limit is considered for a diatomic lattice system with a cubic nonlinearity. A long wave equation describing the interaction of acoustic and optical modes is obtained. It reduces, in certain approximations, to equations having coupled wave solutions. The solutions exhibit trapping of an optical mode by an acoustic soliton. The form of the trapped optical wave depends on the mass ratio of adjacent particles in the diatomic lattice. (author)

  3. Late Silurian fish microfossils from an East Baltic-derived erratic from Oosterhaule, with a description of new acanthodian taxa

    NARCIS (Netherlands)

    Vergoossen, JMJ

    1999-01-01

    Fish microfossils were extracted from an erratic. The taxa from the rich microvertebrate fauna of late Pridolian (latest Silurian) age ( P. punctatus Zone) are listed. A full description is given of two new Gomphonchus taxa, G. mediocostatus and G. boekschoteni. On the basis of old and new material,

  4. Cytoplasmic inheritance of parent-offspring cell structure in the clonal diatom Cyclotella meneghiniana.

    Science.gov (United States)

    Shirokawa, Yuka; Shimada, Masakazu

    2016-11-16

    In cytoplasmic inheritance, structural states of a parent cell could be transmitted to offspring cells via two mechanisms. The first is referred to as the hangover of parent structure, where the structure itself remains and faithfully transmits within offspring cells; the second is structural inheritance, wherein the parent structure functions as a template for development of new offspring structure. We estimated to what extent the parent structure affects the development of offspring structure by structural inheritance, using a clone of the diatom Cyclotella meneghiniana The cell has two siliceous valves (a cell wall part at both cell poles): one is inherited from the parent and the other is newly formed. We estimated cytoplasmic heritability by comparing valve traits (central fultoportulae (CTFP), striae, central area, and cell diameter) of parent and new offspring valves, using single-cell isolation and valve labelling. Parent-offspring valve trait regressions showed that all traits, except CTFP, were significantly correlated. We formulated a quantitative genetic model considering the diatom inheritance system and revealed short-term rapid evolution compared with other inheritance systems. Diatom structural inheritance will have evolved to enable clonal populations to rapidly acquire and maintain suitable structures for temporal changes in environments and life-cycle stages. © 2016 The Author(s).

  5. Remarkably preserved tephra from the 3430 Ma Strelley Pool Formation, Western Australia: Implications for the interpretation of Precambrian microfossils

    Science.gov (United States)

    Wacey, David; Saunders, Martin; Kong, Charlie

    2018-04-01

    The ∼3430 Ma Strelley Pool Formation (SPF), Pilbara, Western Australia contains some of the most diverse microfossil evidence for early life on Earth. Here we report an assemblage of tephra (scoria, tubular pumice, plus vesicular and non-vesicular volcanic glass shards) from two stratigraphic levels in the SPF, including morphotypes that closely resemble previously described microfossils from this unit and elsewhere. Clasts of scoria are characterised by numerous spheroidal vesicles, with subordinate eye- and lens-shaped morphotypes, commonly lined with anatase (TiO2) and small amounts of organic material. Their diameters range from 5-180 μm with 80% in the 10-50 μm range. Fragments of tubular pumice are also lined with anatase + / - carbon and have tube diameters of 5-15 μm. Other volcanic ejecta particles include a multitude of sub-angular shard particles with or without vesicles, plus more rounded vase-shaped, eye-shaped, and hair-like morphologies; once again, most of these are coated by anatase + / - carbon and are several tens of micrometres in size. Many of the tephra fragments are now entirely silicified with no compositional difference between the former volcanic glass, the vesicle infill and the clast matrix. However, some examples retain a partial aluminosilicate composition, either as a vesicle infilling phase or as isolated lath-like grains within the formerly glassy groundmass. Isolated occurrences of some of these tephra morphotypes strongly resemble simple microbial morphologies including pairs and clusters of cells (cf. scoria), filamentous microbes (cf. tubular pumice) and larger sheaths/cysts (cf. sub-rounded glass shards). Furthermore, some tephra-containing clasts occur in a SPF sandstone unit that hosts previously described microfossils, while others are interbedded with chert layers from which microfossils have also been described. In light of our new volcanogenic data, we evaluate the robustness of previous microfossil evidence from the

  6. Diatom-Specific Oligosaccharide and Polysaccharide Structures Help to Unravel Biosynthetic Capabilities in Diatoms

    Directory of Open Access Journals (Sweden)

    Bruno Gügi

    2015-09-01

    Full Text Available Diatoms are marine organisms that represent one of the most important sources of biomass in the ocean, accounting for about 40% of marine primary production, and in the biosphere, contributing up to 20% of global CO2 fixation. There has been a recent surge in developing the use of diatoms as a source of bioactive compounds in the food and cosmetic industries. In addition, the potential of diatoms such as Phaeodactylum tricornutum as cell factories for the production of biopharmaceuticals is currently under evaluation. These biotechnological applications require a comprehensive understanding of the sugar biosynthesis pathways that operate in diatoms. Here, we review diatom glycan and polysaccharide structures, thus revealing their sugar biosynthesis capabilities.

  7. Energy transfer in diatom/diatom molecular collisions

    International Nuclear Information System (INIS)

    Sohlberg, K.W.

    1992-01-01

    In a collision of two molecules, the translational energy of the collision may be redistributed into internal energy of rotation, vibration, or electron motion, in one or both of the colliding partners. In addition, internal energy in one or more of these modes may be open-quotes quenchedclose quotes into translation, leading to a superelastic collision. Such energy transfer may take place by a number of mechanisms. This energy transfer is of fundamental importance in understanding chemical reaction dynamics. Nearly all chemical reactions take place through a bimolecular collision process (or multiple bimolecular collisions) and the quantum state specificity of the reaction can have a major role in determining the kinetics of the reaction, In particular, the author has investigated vibrational energy transfer in collisions between two diatomic molecules. In addition to serving as models for all molecular collision process, gas phase collisions of these species are ubiquitous in atmospheric phenomena which are of critical importance in answering the current questions about the human induced degradation of the earth's atmospheric. Classical trajectory methods have been used to explore the excitation of vibrations in gas-phase collisions of the nitrogen molecular ion with its parent molecule. The near symmetry of the reactants is shown to result in a high probability that the two molecules are excited by an equal amount of energy. This provides a possible explanation of the molecular beam measurements which show that the total number of vibrational energy quanta excited in the collision is, with a high probability that the two molecules are excited by an equal amount of energy. This provides a possible explanation of the molecular beam measurements which show that the total number of vibrational energy quanta excited in the collision is, with a high probability, even

  8. Vibracore, Radiocarbon, Microfossil, and Grain-Size Data from Apalachicola Bay, Florida

    Science.gov (United States)

    Twichell, D.C.; Pendleton, E.A.; Poore, R.Z.; Osterman, L.E.; Kelso, K.W.

    2009-01-01

    In 2007, the U.S. Geological Survey collected 24 vibracores within Apalachicola Bay, Florida. The vibracores were collected by using a Rossfelder electric percussive (P-3) vibracore system during a cruise on the Research Vessel (R/V) G.K. Gilbert. Selection of the core sites was based on a geophysical survey that was conducted during 2005 and 2006 in collaboration with the National Oceanic and Atmospheric Administration's (NOAA) Coastal Services Center (CSC) and the Apalachicola Bay National Estuarine Research Reserve. This report contains the vibracore data logs, photographs, and core-derived data including grain-size analyses, radiocarbon ages, microfossil counts, and sedimentological interpretations. The long-term goal of this study is to provide maps, data, and assistance to the Apalachicola Bay National Estuarine Research Reserve in their effort to monitor and understand the geology and ecology of Apalachicola Bay Estuary. These data will inform coastal managers charged with the responsibility for resource preservation.

  9. The nature and origin of nucleus-like intracellular inclusions in Paleoproterozoic eukaryote microfossils.

    Science.gov (United States)

    Pang, K; Tang, Q; Schiffbauer, J D; Yao, J; Yuan, X; Wan, B; Chen, L; Ou, Z; Xiao, S

    2013-11-01

    The well-known debate on the nature and origin of intracellular inclusions (ICIs) in silicified microfossils from the early Neoproterozoic Bitter Springs Formation has recently been revived by reports of possible fossilized nuclei in phosphatized animal embryo-like fossils from the Ediacaran Doushantuo Formation of South China. The revisitation of this discussion prompted a critical and comprehensive investigation of ICIs in some of the oldest indisputable eukaryote microfossils-the ornamented acritarchs Dictyosphaera delicata and Shuiyousphaeridium macroreticulatum from the Paleoproterozoic Ruyang Group of North China-using a suite of characterization approaches: scanning electron microscopy (SEM), transmission electron microscopy (TEM), and focused ion beam scanning electron microscopy (FIB-SEM). Although the Ruyang acritarchs must have had nuclei when alive, our data suggest that their ICIs represent neither fossilized nuclei nor taphonomically condensed cytoplasm. We instead propose that these ICIs likely represent biologically contracted and consolidated eukaryotic protoplasts (the combination of the nucleus, surrounding cytoplasm, and plasma membrane). As opposed to degradational contraction of prokaryotic cells within a mucoidal sheath-a model proposed to explain the Bitter Springs ICIs-our model implies that protoplast condensation in the Ruyang acritarchs was an in vivo biologically programmed response to adverse conditions in preparation for encystment. While the discovery of bona fide nuclei in Paleoproterozoic acritarchs would be a substantial landmark in our understanding of eukaryote evolution, the various processes (such as degradational and biological condensation of protoplasts) capable of producing nuclei-mimicking structures require that interpretation of ICIs as fossilized nuclei be based on comprehensive investigations. © 2013 John Wiley & Sons Ltd.

  10. An Ecometric Study of Recent Microfossils using High-throughput Imaging

    Science.gov (United States)

    Elder, L. E.; Hull, P. M.; Hsiang, A. Y.; Kahanamoku, S.

    2016-02-01

    The era of Big Data has ushered in the potential to collect population level information in a manageable time frame. Taxon-free morphological trait analysis, referred to as ecometrics, can be used to examine and compare ecological dynamics between communities with entirely different species compositions. Until recently population level studies of morphology were difficult because of the time intensive task of collecting measurements. To overcome this, we implemented advances in imaging technology and created software to automate measurements. This high-throughput set of methods collects assemblage-scale data, with methods tuned to foraminiferal samples (e.g., light objects on a dark background). Methods include serial focused dark-field microscopy, custom software (Automorph) to batch process images, extract 2D and 3D shape parameters and frames, and implement landmark-free geometric morphometric analyses. Informatics pipelines were created to store, catalog and share images through the Yale Peabody Museum(YPM; peabody.yale.edu). We openly share software and images to enhance future data discovery. In less than a year we have generated over 25TB of high resolution semi 3D images for this initial study. Here, we take the first step towards developing ecometric approaches for open ocean microfossil communities with a calibration study of community shape in recent sediments. We will present an overview of the `shape' of modern planktonic foraminiferal communities from 25 Atlantic core top samples (23 sites in the North and Equatorial Atlantic; 2 sites in the South Atlantic). In total, more than 100,000 microfossils and fragments were imaged from these sites' sediment cores, an unprecedented morphometric sample set. Correlates of community shape, including diversity, temperature, and latitude, will be discussed. These methods have also been applied to images of limpets and fish teeth to date, and have the potential to be used on modern taxa to extract meaningful

  11. Silicate glasses. Chapter 1

    International Nuclear Information System (INIS)

    Lutze, W.

    1988-01-01

    This chapter is a survey of world-wide research and development efforts in nuclear waste glasses and its production technology. The principal glasses considered are silicate glasses which contain boron, i.e. borosilicate glass. A historical overview of waste form development programs in nine countries is followed by a summary of the design criteria for borosilicate glass compositions glass compositions. In the sections on glass properties the waste form is characterized in terms of potential alterations under the influence of heat, thermal gradients, radiation, aqueous solutions and combinations thereof. The topics are phase transformations, mechanical properties, radiation effects and chemical durability. The results from studies of volcanic glasses, as natural analogues for borosilicate nuclear waste glasses in order to verify predictions obtained from short-term tests in the laboratory, have been compiled in a special section on natural analogues. A special section on advanced vitrification techniques summarizes the various actual and potential processing schemes and describes the facilities. The literature has been considered until 1985. (author). 430 refs.; 68 figs.; 29 tabs

  12. Radioanalysis of siliceous materials

    International Nuclear Information System (INIS)

    Das, H.A.

    2003-01-01

    Both natural and induced radioactivity as well as man-made radiotracers may be applied to assess quality and its maintenance a widely varying range of siliceous materials. One example of industrial application is given for each of these three branches. Natural Radioactivity: The measurement of 222-Rn emanation from building material components serves the determination of the internal diffusion and thus of the effective porosity as well as the usual environmental control. Radiotracers: The specific surface area of silica components can be obtained from measurements of the chemisorptions of fluoride and its kinetics, using acid fluoride solutions and carrier-free 18-F, Tl/2 = 110 min, as the radiotracer. This also enables the determination of fluoride in drinking water at the (sub-) ppm level by spiking isotope dilution and substoichiometric adsorption to small glass beads. Neutron activation analysis (NAA): Concentration profiles down to the micro m-range of trace elements in small electronic components of irregular shape are derived from combination of NAA with controlled sequential etching flux in dilute HF-solutions. The cases of Na, Mn, Co and Se by instrumental NAA and that of W by chemical isolation from the reagent solution are considered. (author)

  13. Environmental silicate nano-biocomposites

    CERN Document Server

    Pollet, Eric

    2012-01-01

    Environmental Silicate Nano-Biocomposites focuses on nano-biocomposites, which are obtained by the association of silicates such as bioclays with biopolymers. By highlighting recent developments and findings, green and biodegradable nano-composites from both renewable and biodegradable polymers are explored. This includes coverage of potential markets such as packaging, agricultures, leisure and the fast food industry. The knowledge and experience of more than twenty international experts in diverse fields, from chemical and biochemical engineering to applications, is brought together in four different sections covering: Biodegradable polymers and Silicates, Clay/Polyesters Nano-biocomposites, Clay/Agropolymers Nano-biocomposites, and Applications and biodegradation of Nano-biocomposites. By exploring the relationships between the biopolymer structures, the processes, and the final properties Environmental Silicate Nano-Biocomposites explains how to design nano-materials to develop new, valuable, environmenta...

  14. 21 CFR 172.410 - Calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely...

  15. Fabrication of insulator nanocapillaries from diatoms

    International Nuclear Information System (INIS)

    Bereczky, R.J.; Tokesi, K.

    2006-01-01

    Complete text of publication follows. Diatoms are unicellular microscopic organisms with silicon-dioxide based skeleton enveloped with an organic material, which composes essentially polysaccharides and proteins (see Fig. 1a.). As it was shown, the valva of the diatoms build up almost from clean silicondioxide [1]. Therefore, removing the organic compounds from the diatom, we can have in our hand an ideal, about 100 μ m-sized, and almost cylindrical shaped insulating nanostructure. There are various techniques available to disembarrass the diatom from its organic compounds. We used the so called hydrogen peroxide method. The advantageous properties of this method are the followings: a) this is one of the fastest procedures among the possible methods, b) do not require special equipment, c) cheap, and last but not least it is less harmful for health compared to other methods. This procedure can be an alternative way of the fabrication of insulator nanocapillaries. In this case the preparation of the nanocapillaries is simple and quick. Moreover, we do not need to invest expensive special techniques, (like micromachining-, electrochemical etching technique, moulding process etc) as it was necessary for the case of previously developed method producing insulator nanocapillaries [2,3]. Fig. 1b and Fig. 1c. show the scanning electron micrograph of the skeleton of the diatoms. The size of the cylindrical holes are roughly 200 nm (see Fig. 1c). (author)

  16. Biogenic silica dissolution in diatom aggregates: insights from reactive transport modelling

    KAUST Repository

    Moriceau, B

    2014-12-15

    © Inter-Research 2014. Diatom aggregates contribute significantly to the vertical sinking flux of particulate matter in the ocean. These fragile structures form a specific microhabitat for the aggregated cells, but their internal chemical and physical characteristics remain largely unknown. Studies on the impact of aggregation on the Si cycle led to apparent inconsistency. Despite a lower biogenic silica (bSiO2) dissolution rate and diffusion of the silicic acid (dSi) being similar in aggregates and in sea-water, dSi surprisingly accumulates in aggregates. A reaction-diffusion model helps to clarify this incoherence by reconstructing dSi accumulation measured during batch experiments with aggregated and non-aggregated Skeletonema marinoi and Chaetoceros decipiens. The model calculates the effective bSiO2 dissolution rate as opposed to the experimental apparent bSiO2 dissolution rate, which is the results of the effective dissolution of bSiO2 and transport of dSi out of the aggregate. In the model, dSi transport out of the aggregate is modulated by alternatively considering retention (decrease of the dSi diffusion constant) and adsorption (reversible chemical bonds between dSi and the aggregate matrix) processes. Modelled bSiO2 dissolution is modulated by the impact of dSi concentration inside aggregates and diatom viability, as enhanced persistence of metabolically active diatoms has been observed in aggregates. Adsorption better explains dSi accumulation within and outside aggregates, raising the possible importance of dSi travelling within aggregates to the deep sea (potentially representing 20% of the total silica flux). The model indicates that bSiO2 dissolution is effectively decreased in aggregates mainly due to higher diatom viability but also to other parameters discussed herein.

  17. Quantification of diatoms in biofilms: Standardisation of methods

    Digital Repository Service at National Institute of Oceanography (India)

    Patil, J.S.; Anil, A.C.

    of the difficulty in sampling and enumeration. Scraping or brushing are the traditional methods used for removal of diatoms from biofilms developed on solid substrata. The method of removal is the most critical step in enumerating the biofilm diatom community...

  18. 9 Records of Diatoms and Physicochemical.cdr

    African Journals Online (AJOL)

    Administrator

    between some physicochemical parameters and diatom species in these ponds. ..... Diversity and relative abundance (%) of diatoms species in selected seasonal ponds in Zaria, Nigeria ..... connection with reference conditions of the water.

  19. Preparation and method of study of fossil diatoms

    Digital Repository Service at National Institute of Oceanography (India)

    Setty, M.G.A.P.

    Two methods of chemical concentration of diatoms occurring in fresh-water sediments, and one chemico-mechanical method of concentration for diatoms occurring in marine sediments are outlined, with emphasis on the extreme care that needs...

  20. Diatoms: a fossil fuel of the future.

    Science.gov (United States)

    Levitan, Orly; Dinamarca, Jorge; Hochman, Gal; Falkowski, Paul G

    2014-03-01

    Long-term global climate change, caused by burning petroleum and other fossil fuels, has motivated an urgent need to develop renewable, carbon-neutral, economically viable alternatives to displace petroleum using existing infrastructure. Algal feedstocks are promising candidate replacements as a 'drop-in' fuel. Here, we focus on a specific algal taxon, diatoms, to become the fossil fuel of the future. We summarize past attempts to obtain suitable diatom strains, propose future directions for their genetic manipulation, and offer biotechnological pathways to improve yield. We calculate that the yields obtained by using diatoms as a production platform are theoretically sufficient to satisfy the total oil consumption of the US, using between 3 and 5% of its land area. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Microfossil sequences in Ilponlampi, a small lake in northern Russian Karelia

    Directory of Open Access Journals (Sweden)

    Huttunen, A.

    1994-12-01

    Full Text Available The Holocene history of Ilponlampi, a small lake situated in northwestern Russian Karelia, is presented based on pollen, diatom, charred particle and botanical macroremain analyses. Four 14-C dates for the sequence show that it reaches back almost to the beginning of the Holocene. The immigration of the various tree species took place somewhat earlier than further west. A natural acidification process is characteristic of the lake, which seems to have remained practically unaffected by any human influence.

  2. Diatoms in Liyu Lake, Eastern Taiwan

    Directory of Open Access Journals (Sweden)

    Liang-Chi Wang

    2010-09-01

    Full Text Available This study described the diatoms appeared in the sediments of Liyu Lake, a lowland natural lake situated at Hualen, eastern Taiwan. A total of 50 species was found in the sediments of this eutrophic lake. In them, 8 species were reported for the first time in Taiwan. They are: Cymbella thienemannii, Navicula absoluta, Navicula bacillum, Frustulia rhomboides var. crassinervia, Gyrosigma procerum, Nitzschia paleacea Epithemia smithii and Eunotia subarcuatioides. The ultrastructures of each species were described on the basis of observations under a scanning electron microscope. The ecological implications of the occurrence of these diatom species in this lake were inferred.

  3. Transitional changes in microfossil assemblages in the Japan Sea from the Late Pliocene to Early Pleistocene related to global climatic and local tectonic events

    Science.gov (United States)

    Itaki, Takuya

    2016-12-01

    Many micropaleontological studies based on data from on-land sections, oil wells, and deep-sea drilling cores have provided important information about environmental changes in the Japan Sea that are related to the global climate and the local tectonics of the Japanese Islands. Here, major changes in the microfossil assemblages during the Late Pliocene to Early Pleistocene are reviewed. Late Pliocene (3.5-2.7 Ma) surface-water assemblages were characterized mainly by cold-temperate planktonic flora and fauna (nannofossils, diatoms, radiolarians, and planktonic foraminifera), suggesting that nutrient-rich North Pacific surface waters entered the Japan Sea via northern straits. The common occurrence of Pacific-type deep-water radiolarians during this period also suggests that deep water from the North Pacific entered the Japan Sea via the northern straits, indicating a sill depth >500 m. A weak warm-water influence is recognized along the Japanese coast, suggesting a small inflow of warm water via a southern strait. Nannofossil and sublittoral ostracod assemblages record an abrupt cooling event at 2.75 Ma that correlates with the onset of the Northern Hemisphere glaciation. Subsequently, cold intermediate- and deep-water assemblages of ostracods and radiolarians increased in abundance, suggesting active ventilation and the formation of the Japan Sea Proper Water, associated with a strengthened winter monsoon. Pacific-type deep-water radiolarians also disappeared around 2.75 Ma, which is attributed to the intermittent occurrence of deep anoxic environments and limited migration from the North Pacific, resulting from the near-closure or shallowing of the northern strait by a eustatic fall in sea level and tectonic uplift of northeastern Japan. A notable reduction in primary productivity from 2.3 to 1.3 Ma also suggests that the nutrient supply from the North Pacific was restricted by the near-closure of the northern strait. An increase in the abundance of subtropical

  4. Epibiotic Diatoms Are Universally Present on All Sea Turtle Species

    Science.gov (United States)

    Majewska, Roksana; Lazo-Wasem, Eric A.; Nel, Ronel; Paladino, Frank V.; Rojas, Lourdes; Zardus, John D.; Pinou, Theodora

    2016-01-01

    The macro-epibiotic communities of sea turtles have been subject to growing interest in recent years, yet their micro-epibiotic counterparts are almost entirely unknown. Here, we provide the first evidence that diatoms are epibionts for all seven extant species of sea turtle. Using Scanning Electron Microscopy, we inspected superficial carapace or skin samples from a single representative of each turtle species. We distinguished 18 diatom taxa from these seven individuals, with each sea turtle species hosting at least two diatom taxa. We recommend that future research is undertaken to confirm whether diatom communities vary between sea turtle species and whether these diatom taxa are facultative or obligate commensals. PMID:27257972

  5. Electron transport through a diatomic molecule

    International Nuclear Information System (INIS)

    Imran, Muhammad

    2014-01-01

    Electron transport through a diatomic molecular tunnel junction shows wave like interference phenomenon. By using Keldysh non-equilibrium Green's function (NEGF) theory, we have explicitly presented current and differential conductance calculation for a diatomic molecular and two isolated atoms (two atoms having zero hybridization between their energy orbitals) tunnel junctions. In case of a diatomic molecular tunnel junction, Green's function propagators entering into current and differential conductance formula interfere constructively for a molecular anti-bonding state and destructively for bonding state. Consequently, conductance through a molecular bonding state is suppressed, and to conserve current, conductance through anti-bonding state is enhanced. Therefore, current steps and differential conductance peaks amplitude show asymmetric correspondence between molecular bonding and anti-bonding states. Interestingly, for a diatomic molecule, comprising of two atoms of same energy level, these propagators interfere completely destructively for molecular bonding state and constructively for molecular anti-bonding state. Hence under such condition, a single step or a single peak is shown up in current versus voltage or differential conductance versus voltage studies.

  6. Genetic and metabolic engineering in diatoms.

    Science.gov (United States)

    Huang, Weichao; Daboussi, Fayza

    2017-09-05

    Diatoms have attracted considerable attention due to their success in diverse environmental conditions, which probably is a consequence of their complex origins. Studies of their metabolism will provide insight into their adaptation capacity and are a prerequisite for metabolic engineering. Several years of investigation have led to the development of the genome engineering tools required for such studies, and a profusion of appropriate tools is now available for exploring and exploiting the metabolism of these organisms. Diatoms are highly prized in industrial biotechnology, due to both their richness in natural lipids and carotenoids and their ability to produce recombinant proteins, of considerable value in diverse markets. This review provides an overview of recent advances in genetic engineering methods for diatoms, from the development of gene expression cassettes and gene delivery methods, to cutting-edge genome-editing technologies. It also highlights the contributions of these rapid developments to both basic and applied research: they have improved our understanding of key physiological processes; and they have made it possible to modify the natural metabolism to favour the production of specific compounds or to produce new compounds for green chemistry and pharmaceutical applications.This article is part of the themed issue 'The peculiar carbon metabolism in diatoms'. © 2017 The Author(s).

  7. Polymer-Layer Silicate Nanocomposites

    DEFF Research Database (Denmark)

    Potarniche, Catalina-Gabriela

    Nowadays, some of the material challenges arise from a performance point of view as well as from recycling and biodegradability. Concerning these aspects, the development of polymer layered silicate nanocomposites can provide possible solutions. This study investigates how to obtain polymer layered...... with a spectacular improvement up to 300 % in impact strength were obtained. In the second part of this study, layered silicate bio-nanomaterials were obtained starting from natural compounds and taking into consideration their biocompatibility properties. These new materials may be used for drug delivery systems...... and as biomaterials due to their high biocompatible properties, and because they have the advantage of being biodegradable. The intercalation process of natural compounds within silicate platelets was investigated. By uniform dispersing of binary nanohybrids in a collagen matrix, nanocomposites with intercalated...

  8. On crystallochemistry of uranil silicates

    International Nuclear Information System (INIS)

    Sidorenko, G.A.; Moroz, I.Kh.; Zhil'tsova, I.G.

    1975-01-01

    A crystallochemical analysis has been made of uranil silicates. It is shown that on crystallochemical grounds it is justified to distinguish among them uranophane-kasolite, soddyite and viksite groups differing in the uranil-anion [SiO 4 ] -4 ratio and, as a consequence, in their crystallochemical structures. Widespread silicates of the uranophane-kasolite group is the formation of polytype modifications where, depending on the interlaminar cation, crystalline structures are formed with various packing of single-type uranil-anion layers. It has been shown experimentally that silicates of the uranophanekasolite group contain no oxonium ion in their crystalline structures. Minerals of the viksite group belong to a group of isostructural (homeotypic) laminated formation apt to form phases of different degrees of hydration. Phases with a smaller interlaminar cation form hydrates with a greater number of water molecules in the formulas unit

  9. NON-AUTOCLAVE SILICATE BRICK

    Directory of Open Access Journals (Sweden)

    V. N. Yaglov

    2015-01-01

    Full Text Available The paper proposes a technology for obtaining bricks on the basis of lime-silica mixtures where chemical interactions are practically completely realized in dispersive state at the stage of preparation of binding contact maturing and raw mixture as a whole. The role of forming operation (moulding is changed in principle because in this case conversion of dispersive system into a rock-like solid occurs and due to this the solid obtains complete water-resistance in contact with water immediately after forming operation. Theoretical basis for the developed technology is capability of silicate dispersive substances (hydrated calcium silicate to transit in non-stable state, to form a rock-like water-resistant solid in the moment of mechanical load application during forming process. Specific feature of the proposed method is an exclusion of additional operations for autoclaving of products from the process of obtaining a silicate brick.Synthetic hydrated calcium silicate in contrast to natural ones are more uniform in composition and structure, they contain less impurities and they are characterized by dispersive composition and due to the mentioned advantages they find wider practical application. Contact-condensation binders permit to manipulate product properties on their basis and ensure maximum correspondence to the requirements of the concrete application. Raw material sources for obtaining synthetic hydrated calcium silicates are practically un-limited because calcium-silicon containing substances are found as in various technogenic wastes so in natural compounds as well. So the problem for obtaining hydrated calcium silicates having contact-condensation ability for structure formation becomes more and more actual one. This transition is considered as dependent principally on arrangement rate of substance particles which determined the level of its instability.

  10. Potential effects of climate change on the distribution range of the main silicate sinker of the Southern Ocean.

    Science.gov (United States)

    Pinkernell, Stefan; Beszteri, Bánk

    2014-08-01

    Fragilariopsis kerguelensis, a dominant diatom species throughout the Antarctic Circumpolar Current, is coined to be one of the main drivers of the biological silicate pump. Here, we study the distribution of this important species and expected consequences of climate change upon it, using correlative species distribution modeling and publicly available presence-only data. As experience with SDM is scarce for marine phytoplankton, this also serves as a pilot study for this organism group. We used the maximum entropy method to calculate distribution models for the diatom F. kerguelensis based on yearly and monthly environmental data (sea surface temperature, salinity, nitrate and silicate concentrations). Observation data were harvested from GBIF and the Global Diatom Database, and for further analyses also from the Hustedt Diatom Collection (BRM). The models were projected on current yearly and seasonal environmental data to study current distribution and its seasonality. Furthermore, we projected the seasonal model on future environmental data obtained from climate models for the year 2100. Projected on current yearly averaged environmental data, all models showed similar distribution patterns for F. kerguelensis. The monthly model showed seasonality, for example, a shift of the southern distribution boundary toward the north in the winter. Projections on future scenarios resulted in a moderately to negligibly shrinking distribution area and a change in seasonality. We found a substantial bias in the publicly available observation datasets, which could be reduced by additional observation records we obtained from the Hustedt Diatom Collection. Present-day distribution patterns inferred from the models coincided well with background knowledge and previous reports about F. kerguelensis distribution, showing that maximum entropy-based distribution models are suitable to map distribution patterns for oceanic planktonic organisms. Our scenario projections indicate

  11. Paleoceanographic history of the Guaymas Basin, Gulf of California, during the past 15,000 years based on diatoms, silicoflagellates, and biogenic sediments

    Science.gov (United States)

    Barron, J.A.; Bukry, D.; Dean, W.E.

    2005-01-01

    High-resolution records of calcium carbonate, biogenic opal, diatoms, and silicoflagellates from western Guaymas Basin gravity core GGC55 and piston core JPC56 and eastern Guaymas Basin DSDP Site 480 reveal a complex paleoceanographic history of the central Gulf of California during the past 15,000 years. Prior to ??? 6.2 ka, the eastern and western Guaymas Basin proxy records were remarkably similar. After conditions similar to those of today during the B??lling-Allerod, the Younger Dryas (YD) saw a major drop in diatom production, coincident with increased calcium carbonate and tropical microfossils suggestive of El Nin??o-like conditions. Biosiliceous productivity began increasing during the latter part of the YD, but it was only during the earliest Holocene (11.6 to 11.0 ka) that conditions similar to those of the B??lling-Allerod returned to the central Gulf. Between around 11.0 and 6.2 ka, tropical diatoms and silicoflagellates were virtually absent from the central Gulf, as relatively cooler and fresher surface waters resembling those of the modern northern Gulf were present in the central Gulf. Beginning at about 6.2 ka, tropical diatoms and silicoflagellates began increasing in the central Gulf, and coccoliths returned to western Gulf sediments. The onset of modern-day monsoon conditions in the American Southwest required the presence of warm SSTs in the northern Gulf, which probably did not occur until after about 5.4 ka, when tropical diatoms and silicoflagellates became relatively common in the central Gulf. Modern east-west contrasts, which arise from late winter-early spring coastal upwelling on the mainland side and lower diatom productivity on the western side of the Gulf, commenced between 6.2 and 5.4 ka, possibly due to a shift in the direction of late winter-early spring winds more towards the southeast, or down the axis of the Gulf. This proposed wind shift might have ultimately been due to a late Holocene strengthening of ENSO-like conditions

  12. Antibacterial Activity of Silicate Bioceramics

    Institute of Scientific and Technical Information of China (English)

    HU Sheng; NING Congqin; ZHOU Yue; CHEN Lei; LIN Kaili; CHANG Jiang

    2011-01-01

    Four kinds of pure silicate ceramic particles, CaSiO3, Ca3SiO5, bredigite and akermanite were prepared and their bactericidal effects were systematically investigated. The phase compositions of these silicate ceramics were characterized by XRD. The ionic concentration meas urement revealed that the Calcium (Ca) ion concentration were relatively higher in Ca3SiO5 and bredigite, and much lower in CaSiO3 and akermanite. Accordingly, the pH values of the four silicate ceramics extracts showed a positive correlation with the particle concentrations. Meanwhile, by decreasing the particle size, higher Ca ion concentrations can be achieved, leading to the increase of aqueous pH value as well. In summary, all of the four silicate ceramics tested in our study showed antibacterial effect in a dose-dependent manner. Generally, the order of their antibacterial activity against E.coli from strong to weak is Ca3SiO5, bredigite, CaSiO3 and akermanite.

  13. Amended Silicated for Mercury Control

    Energy Technology Data Exchange (ETDEWEB)

    James Butz; Thomas Broderick; Craig Turchi

    2006-12-31

    Amended Silicates{trademark}, a powdered, noncarbon mercury-control sorbent, was tested at Duke Energy's Miami Fort Station, Unit 6 during the first quarter of 2006. Unit 6 is a 175-MW boiler with a cold-side electrostatic precipitator (ESP). The plant burns run-of-the-river eastern bituminous coal with typical ash contents ranging from 8-15% and sulfur contents from 1.6-2.6% on an as-received basis. The performance of the Amended Silicates sorbent was compared with that for powdered activated carbon (PAC). The trial began with a period of baseline monitoring during which no sorbent was injected. Sampling during this and subsequent periods indicated mercury capture by the native fly ash was less than 10%. After the baseline period, Amended Silicates sorbent was injected at several different ratios, followed by a 30-day trial at a fixed injection ratio of 5-6 lb/MMACF. After this period, PAC was injected to provide a comparison. Approximately 40% mercury control was achieved for both the Amended Silicates sorbent and PAC at injection ratios of 5-6 lbs/MMACF. Higher injection ratios did not achieve significantly increased removal. Similar removal efficiencies have been reported for PAC injection trials at other plants with cold-side ESPs, most notably for plants using medium to high sulfur coal. Sorbent injection did not detrimentally impact plant operations and testing confirmed that the use of Amended Silicates sorbent does not degrade fly ash quality (unlike PAC). The cost for mercury control using either PAC or Amended Silicates sorbent was estimated to be equivalent if fly ash sales are not a consideration. However, if the plant did sell fly ash, the effective cost for mercury control could more than double if those sales were no longer possible, due to lost by-product sales and additional cost for waste disposal. Accordingly, the use of Amended Silicates sorbent could reduce the overall cost of mercury control by 50% or more versus PAC for locations where

  14. 21 CFR 182.2227 - Calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c) Limitations...

  15. 21 CFR 582.2227 - Calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c) Limitations...

  16. [Research advances in heavy metals pollution ecology of diatom].

    Science.gov (United States)

    Ding, Teng-Da; Ni, Wan-Min; Zhang, Jian-Ying

    2012-03-01

    Diatom, due to its high sensitivity to environmental change, is one of the bio-indicators of aquatic ecosystem health, and some typical diatom species have been applied to indicate the heavy metals pollution of water body. With the focus on the surface water heavy metals pollution, this paper reviewed the research advances in the toxic effect of heavy metals pollution on diatom, biosorption and bioaccumulation of heavy metals by diatom, ecological adaptation mechanisms of diatom to heavy metals pollution, and roles of diatom as bio-indicator and in ecological restoration of heavy metals pollution. The growth tendency of diatom and the morphological change of frustule under heavy metals pollution as well as the differences in heavy metals biosorption and bioaccumulation by diatom, the ecological adaptation mechanisms of diatom on heavy metals surface complexation and ion exchange, and the roles of diatom as bio-indicator and in ecological restoration of heavy metals polluted water body were also discussed. This review could provide scientific evidences for the prevention of aquatic ecosystems heavy metals pollution and related early warning techniques.

  17. The isotopic composition of valves and organic tissue of diatoms grown in steady state cultures under varying conditions of temperature, light and nutrients. Implications for the interpretation of oxygen isotopes from sedimentary biogenic opal as proxies of environmental variations

    Energy Technology Data Exchange (ETDEWEB)

    Kowalczyk, K

    2006-05-15

    The oxygen isotopes of diatomaceous silica from marine and freshwater sediments are frequently used as indicators of the palaeotemperature development, particularly in cases where calcareous microfossils are rare or absent. With regard to terrestrial waters it is unknown whether or not palaeotemperature scale can be used in a limnic ecosystem. Due to the fact that the seasonal variations in lakes are larger than in oceans, specific problems arise when working with freshwater sediments. Thus, an understanding of the contribution of the various factors (e.g. temperature, light nutrients, competition) influencing the formation of isotope signals in biogenic opal is a prerequisite for the accurate interpretation of environmental processes. Since it is impossible to examine the influence of a single parameter under natural ecosystem conditions due to permanent changes of the environment, laboratory experiments with single diatom species are needed. Therefore, the aim of this study was to investigate the correlation between the oxygen isotope variations in biogenic opal and different environmental parameters using steady state cultures with diatoms. It should be examined whether or not the different diatom species grown under identical conditions show equal oxygen isotope ratios (species relationship), if variations of the water temperature induce variations of the oxygen isotope ratio (relationship with temperature), variable parameters such as light intensity and nitrate concentration influence the isotope ratio, and if vital effects (e.g. growth rate) lead to variations of the oxygen isotope ratio. (orig.)

  18. The isotopic composition of valves and organic tissue of diatoms grown in steady state cultures under varying conditions of temperature, light and nutrients. Implications for the interpretation of oxygen isotopes from sedimentary biogenic opal as proxies of environmental variations

    International Nuclear Information System (INIS)

    Kowalczyk, K.

    2006-05-01

    The oxygen isotopes of diatomaceous silica from marine and freshwater sediments are frequently used as indicators of the palaeotemperature development, particularly in cases where calcareous microfossils are rare or absent. With regard to terrestrial waters it is unknown whether or not palaeotemperature scale can be used in a limnic ecosystem. Due to the fact that the seasonal variations in lakes are larger than in oceans, specific problems arise when working with freshwater sediments. Thus, an understanding of the contribution of the various factors (e.g. temperature, light nutrients, competition) influencing the formation of isotope signals in biogenic opal is a prerequisite for the accurate interpretation of environmental processes. Since it is impossible to examine the influence of a single parameter under natural ecosystem conditions due to permanent changes of the environment, laboratory experiments with single diatom species are needed. Therefore, the aim of this study was to investigate the correlation between the oxygen isotope variations in biogenic opal and different environmental parameters using steady state cultures with diatoms. It should be examined whether or not the different diatom species grown under identical conditions show equal oxygen isotope ratios (species relationship), if variations of the water temperature induce variations of the oxygen isotope ratio (relationship with temperature), variable parameters such as light intensity and nitrate concentration influence the isotope ratio, and if vital effects (e.g. growth rate) lead to variations of the oxygen isotope ratio. (orig.)

  19. The diatom flora of Lake Kinneret (Israel) - Paleolimnological evidence for Holocene climate change and human impact in the southeastern Mediterranean

    Science.gov (United States)

    Vossel, Hannah; Reed, Jane M.; Litt, Thomas

    2015-04-01

    The Mediterranean basin is a region of highly complex topography and climatic variability, such that our understanding of the past environmental variability is still limited. Diatoms (single-celled siliceous algae, Bacillariophyceae) are abundant, diverse and sensitive to a wide range of environmental parameters. They are often well preserved in lake sediment records, and have well-recognised potential to generate high-quality paleolimnological data. Diatoms remain one of the least-exploited proxies in Mediterranean palaeoclimate research. Here, we present results of diatom analysis of an 18 m sediment core from Lake Kinneret (Israel) as part of a multi-proxy study of Holocene climate change and human impact in the Levant (http://www.sfb806.uni-koeln.de). Results are compared with other proxy data including pollen, and with output data from regional climate modelling, to strengthen interpretation of environmental change in the southeastern Mediterranean. The results show remarkable shifts in the diatom flora over the last ca. 8,000 years. Preliminary investigations show that 98% of the diatom taxa can be classified as oligohalobous-indifferent and as alkaliphilous, as is typical of freshwater, alkaline lakes of open hydrology in limestone, karst-dominated catchments. Changes in the diatom data over time can be interpreted mainly in terms of productivity shifts, with a clear trend from oligotrophic at the base to hypereutrophic in the modern lake. The eutrophication trend accelerates after ca. 3,000 cal. yrs. BP, indicating the influence of increased human activity in the catchment, identified previously by analysis of the vegetational history (Schiebel, 2013). The analysis of the composition of the diatom flora also provides some evidence for lake-level fluctuations, as a proxy for shifts in moisture availability. Low lake-level stands are characterized by low diatom concentration and increased relative abundance of littoral taxa. High lake-level stands are marked

  20. Diatomic infrared gas-dynamic laser

    International Nuclear Information System (INIS)

    Mckenzie, R.L.

    1971-01-01

    A laser is provided which utilizes the infrared vibration rotation transitions of a diatomic gas such as carbon monoxide. The laser action is produced by an active diatomic gas such as carbon monoxide mixed with a vibrationally resonant pumping gas such as nitrogen. In addition, a noble gas such as argon may be employed as a third gas in the mixture. The gas mixture contains from 1 to 80 vol percent of the active gas based on the pumping gas, and the third gas, if used, can constitute up to 90 percent of the total gas volume. A number of significantly different wavelengths can be produced by the laser. A single laser may contain several optical resonators at different locations, so that the desired wave length can be selected at will

  1. High CO2 and silicate limitation synergistically increase the toxicity of Pseudo-nitzschia fraudulenta.

    Directory of Open Access Journals (Sweden)

    Avery O Tatters

    Full Text Available Anthropogenic CO(2 is progressively acidifying the ocean, but the responses of harmful algal bloom species that produce toxins that can bioaccumulate remain virtually unknown. The neurotoxin domoic acid is produced by the globally-distributed diatom genus Pseudo-nitzschia. This toxin is responsible for amnesic shellfish poisoning, which can result in illness or death in humans and regularly causes mass mortalities of marine mammals and birds. Domoic acid production by Pseudo-nitzschia cells is known to be regulated by nutrient availability, but potential interactions with increasing seawater CO(2 concentrations are poorly understood. Here we present experiments measuring domoic acid production by acclimatized cultures of Pseudo-nitzschia fraudulenta that demonstrate a strong synergism between projected future CO(2 levels (765 ppm and silicate-limited growth, which greatly increases cellular toxicity relative to growth under modern atmospheric (360 ppm or pre-industrial (200 ppm CO(2 conditions. Cellular Si:C ratios decrease with increasing CO(2, in a trend opposite to that seen for domoic acid production. The coastal California upwelling system where this species was isolated currently exhibits rapidly increasing levels of anthropogenic acidification, as well as widespread episodic silicate limitation of diatom growth. Our results suggest that the current ecosystem and human health impacts of toxic Pseudo-nitzschia blooms could be greatly exacerbated by future ocean acidification and 'carbon fertilization' of the coastal ocean.

  2. Silicon diatom frustules as nanostructured photoelectrodes.

    Science.gov (United States)

    Chandrasekaran, Soundarrajan; Sweetman, Martin J; Kant, Krishna; Skinner, William; Losic, Dusan; Nann, Thomas; Voelcker, Nicolas H

    2014-09-18

    In the quest for solutions to meeting future energy demands, solar fuels play an important role. A particularly promising example is photocatalysis since even incremental improvements in performance in this process are bound to translate into significant cost benefits. Here, we report that semiconducting and high surface area 3D silicon replicas prepared from abundantly available diatom fossils sustain photocurrents and enable solar energy conversion.

  3. Collision-induced dissociation of diatomic ions

    International Nuclear Information System (INIS)

    Los, J.; Govers, T.R.

    1978-01-01

    An attempt is made to illustrate how mass spectrometric studies of dissociation in diatomic molecular ions can provide information on the dynamics of these collisions and on the predissociative states involved. Restriction is made to primary beam energies of the order of at least keV. The review covers the dynamics of dissociation, experimental techniques, direct dissociation in heavy-particle collisions, and translational spectroscopy. 120 references

  4. Electric dipole moment of diatomic molecules

    International Nuclear Information System (INIS)

    Rosato, A.

    1983-01-01

    The electric dipole moment of some diatomic molecules is calculated using the Variational Cellular Method. The results obtained for the molecules CO, HB, HF and LiH are compared with other calculations and with experimental data. It is shown that there is strong dependence of the electric dipole moment with respect to the geometry of the cells. It is discussed the possibility of fixing the geometry of the problem by giving the experimental value of the dipole moment. (Author) [pt

  5. Electric dipole moment of diatomic molecules

    International Nuclear Information System (INIS)

    Rosato, A.

    1983-01-01

    The electric dipole moment of some diatomic molecules is calculated using the Variational Cellular Method. The results obtained for the CO, HB, HF and LiH molecules are compared with other calculations and with experimental data. It is shown that there is strong dependence of the electric dipole moment with respect to the geometry of the cells. The possibility of fixing the geometry of the problem by giving the experimental value of the dipole moment is discussed. (Author) [pt

  6. Assessing trends in fishery resources and lake-water aluminum from paleolimnological analyses of siliceous algae

    International Nuclear Information System (INIS)

    Kingston, J.C.; Birks, H.J.B.; Uutala, A.J.; Cummings, B.F.; Smol, J.P.

    1992-01-01

    Lake water aluminum concentrations have a significant influence on the composition of microfossil assemblages of diatoms and chrysophytes deposited in lake sediments. With the paleolimnological approach of multilake datasets in the Adirondack region of New York, USA, the authors use canonical correspondence analysis to describe past trends in lake water Al. Four lakes, previously investigated regarding acidification and fishery trends, are used to demonstrate that paleolimnological assessment can also provide direction, timing, and magnitude of trends for both toxic metals and fish resources. Additionally, the authors use weighted average regression and calibration to obtain quantitative reconstructions of past lake water Al concentrations. Such reconstructions provide further insight into fishery resource damage and can be compared with modelling results. According to paleolimnological reconstructions, some of the naturally most acidic lakes in the Adirondack region had preindustrial lake water concentrations of inorganic monomeric Al near 4/micromol times L. Although these high concentrations are surprising from a geochemical point of view, they may partially explain the preindustrial absence of fish, as has been independently determined by paleolimnological analysis of phantom midges (Chaoborus). Fishery resource deterioration in acidified Adirondack lakes was coincident with major increases in lake water Al concentrations

  7. Microfossils, biomolecules and biominerals in carbonaceous meteorites: implications to the origin of life

    Science.gov (United States)

    Hoover, Richard B.

    2012-11-01

    Environmental and Field Emission Scanning Electron Microscopy (ESEM and FESEM) investigations have shown that a wide variety of carbonaceous meteorites contain the remains of large filaments embedded within freshly fractured interior surfaces of the meteorite rock matrix. The filaments occur singly or in dense assemblages and mats and are often encased within carbon-rich, electron transparent sheaths. Electron Dispersive X-ray Spectroscopy (EDS) spot analysis and 2D X-Ray maps indicate the filaments rarely have detectable nitrogen levels and exhibit elemental compositions consistent with that interpretation that of the meteorite rock matrix. Many of the meteorite filaments are exceptionally well-preserved and show evidence of cells, cell-wall constrictions and specialized cells and processes for reproduction, nitrogen fixation, attachment and motility. Morphological and morphometric analyses permit many of the filaments to be associated with morphotypes of known genera and species of known filamentous trichomic prokaryotes (cyanobacteria and sulfur bacteria). The presence in carbonaceous meteorites of diagenetic breakdown products of chlorophyll (pristane and phytane) along with indigenous and extraterrestrial chiral protein amino acids, nucleobases and other life-critical biomolecules provides strong support to the hypothesis that these filaments represent the remains of cyanobacteria and other microorganisms that grew on the meteorite parent body. The absence of other life-critical biomolecules in the meteorites and the lack of detectable levels of nitrogen indicate the filaments died long ago and can not possibly represent modern microbial contaminants that entered the stones after they arrived on Earth. This paper presents new evidence for microfossils, biomolecules and biominerals in carbonaceous meteorites and considers the implications to some of the major hypotheses for the Origin of Life.

  8. Applications of Diatoms as Potential Microalgae in Nanobiotechnology

    OpenAIRE

    Ahmad Yari Khosroushahi; Miguel de la Guardia; Mohamad Moradi Ghorakhlu; Ali Akbar Jamali; Fariba Akbari

    2012-01-01

    Introduction: Diatoms are single cell eukaryotic microalgae, which present in nearly every water habitat make them ideal tools for a wide range of applications such as oil explora­tion, forensic examination, environmental indication, biosilica pattern generation, toxicity testing and eutrophication of aqueous ecosystems. Methods: Essential information on diatoms were reviewed and discussed towards impacts of diatoms on biosynthesis and bioremediation. Results: In this review, we present the ...

  9. Diatom flora in subterranean ecosystems: a review

    Directory of Open Access Journals (Sweden)

    Elisa Falasco

    2014-09-01

    Full Text Available In scarcity of light and primary producers, subterranean ecosystems are generally extremely oligotrophic habitats, receiving poor supplies of degradable organic matter from the surface. Human direct impacts on cave ecosystems mainly derive from intensive tourism and recreational caving, causing important alterations to the whole subterranean environment. In particular, artificial lighting systems in show caves support the growth of autotrophic organisms (the so-called lampenflora, mainly composed of cyanobacteria, diatoms, chlorophytes, mosses and ferns producing exocellular polymeric substances (EPSs made of polysaccharides, proteins, lipids and nucleic acids. This anionic EPSs matrix mediates to the intercellular communications and participates to the chemical exchanges with the substratum, inducing the adsorption of cations and dissolved organic molecules from the cave formations (speleothems. Coupled with the metabolic activities of heterotrophic microorganisms colonising such layer (biofilm, this phenomenon may lead to the corrosion of the mineral surfaces. In this review, we investigate the formation of biofilms, especially of diatom-dominated ones, as a consequence of artificial lighting and its impacts on speleothems. Whenever light reaches the subterranean habitat (both artificially and naturally a relative high number of species of diatoms may indeed colonise it. Cave entrances, artificially illuminated walls and speleothems inside the cave are generally the preferred substrates. This review focuses on the diatom flora colonising subterranean habitats, summarizing the information contained in all the scientific papers published from 1900 up to date. In this review we provide a complete checklist of the diatom taxa recorded in subterranean habitats, including a total of 363 taxa, belonging to 82 genera. The most frequent and abundant species recorded in caves and other low light subterranean habitats are generally aerophilic and

  10. Modifying Silicates for Better Dispersion in Nanocomposites

    Science.gov (United States)

    Campbell, Sandi

    2005-01-01

    An improved chemical modification has been developed to enhance the dispersion of layered silicate particles in the formulation of a polymer/silicate nanocomposite material. The modification involves, among other things, the co-exchange of an alkyl ammonium ion and a monoprotonated diamine with interlayer cations of the silicate. The net overall effects of the improved chemical modification are to improve processability of the nanocomposite and maximize the benefits of dispersing the silicate particles into the polymer. Some background discussion is necessary to give meaning to a description of this development. Polymer/silicate nanocomposites are also denoted polymer/clay composites because the silicate particles in them are typically derived from clay particles. Particles of clay comprise layers of silicate platelets separated by gaps called "galleries." The platelet thickness is 1 nm. The length varies from 30 nm to 1 m, depending on the silicate. In order to fully realize the benefits of polymer/silicate nanocomposites, it is necessary to ensure that the platelets become dispersed in the polymer matrices. Proper dispersion can impart physical and chemical properties that make nanocomposites attractive for a variety of applications. In order to achieve nanometer-level dispersion of a layered silicate into a polymer matrix, it is typically necessary to modify the interlayer silicate surfaces by attaching organic functional groups. This modification can be achieved easily by ion exchange between the interlayer metal cations found naturally in the silicate and protonated organic cations - typically protonated amines. Long-chain alkyl ammonium ions are commonly chosen as the ion-exchange materials because they effectively lower the surface energies of the silicates and ease the incorporation of organic monomers or polymers into the silicate galleries. This completes the background discussion. In the present improved modification of the interlayer silicate surfaces

  11. Properties of Tricalcium Silicate Sealers.

    Science.gov (United States)

    Khalil, Issam; Naaman, Alfred; Camilleri, Josette

    2016-10-01

    Sealers based on tricalcium silicate cement aim at an interaction of the sealer with the root canal wall, alkalinity with potential antimicrobial activity, and the ability to set in a wet field. The aim of this study was to characterize and investigate the properties of a new tricalcium silicate-based sealer and verify its compliance to ISO 6876 (2012). A new tricalcium silicate-based sealer (Bio MM; St Joseph University, Beirut, Lebanon), BioRoot RCS (Septodont, St Maure de Fosses, France), and AH Plus (Dentsply, DeTrey, Konstanz, Germany) were investigated. Characterization using scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction analysis was performed. Furthermore, sealer setting time, flow, film thickness, and radiopacity were performed following ISO specifications. pH and ion leaching in solution were assessed by pH analysis and inductively coupled plasma. Bio MM and BioRoot RCS were both composed of tricalcium silicate and tantalum oxide in Bio MM and zirconium oxide in BioRoot RCS. In addition, the Bio MM contained calcium carbonate and a phosphate phase. The inorganic components of AH Plus were calcium tungstate and zirconium oxide. AH Plus complied with the ISO norms for both flow and film thickness. BioRoot RCS and Bio MM exhibited a lower flow and a higher film thickness than that specified for sealer cements in ISO 6876. All test sealers exhibited adequate radiopacity. Bio MM interacted with physiologic solution, thus showing potential for bioactivity. Sealer properties were acceptable and comparable with other sealers available clinically. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  12. Seasonal variations in fouling diatom communities on the Yantai coast

    Science.gov (United States)

    Yang, Cuiyun; Wang, Jianhua; Yu, Yang; Liu, Sujing; Xia, Chuanhai

    2015-03-01

    Fouling diatoms are a main component of biofilm, and play an important role in marine biofouling formation. We investigated seasonal variations in fouling diatom communities that developed on glass slides immersed in seawater, on the Yantai coast, northern Yellow Sea, China, using microscopy and molecular techniques. Studies were conducted during 2012 and 2013 over 3, 7, 14, and 21 days in each season. The abundance of attached diatoms and extracellular polymeric substances increased with exposure time of the slides to seawater. The lowest diatom density appeared in winter and the highest species richness and diversity were found in summer and autumn. Seasonal variation was observed in the structure of fouling diatom communities. Pennate diatoms Cylindrotheca, Nitzschia, Navicula, Amphora, Gomphonema, and Licmophora were the main fouling groups. Cylindrotheca sp. dominated in the spring. Under laboratory culture conditions, we found that Cylindrotheca grew very fast, which might account for the highest density of this diatom in spring. The lower densities in summer and autumn might result from the emergence of fouling animals and environmental factors. The Cylindrotheca sp. was identified as Cylindrotheca closterium using18S rDNA sequencing. The colonization process of fouling diatoms and significant seasonal variation in this study depended on environmental and biological factors. Understanding the basis of fouling diatoms is essential and important for developing new antifouling techniques.

  13. Inorganic carbon availability in benthic diatom communities: photosynthesis and migration.

    Science.gov (United States)

    Marques da Silva, Jorge; Cruz, Sónia; Cartaxana, Paulo

    2017-09-05

    Diatom-dominated microphytobenthos (MPB) is the main primary producer of many intertidal and shallow subtidal environments, being therefore of critical importance to estuarine and coastal food webs. Owing to tidal cycles, intertidal MPB diatoms are subjected to environmental conditions far more variable than the ones experienced by pelagic diatoms (e.g. light, temperature, salinity, desiccation and nutrient availability). Nevertheless, benthic diatoms evolved adaptation mechanisms to these harsh conditions, including the capacity to move within steep physical and chemical gradients, allowing them to perform photosynthesis efficiently. In this contribution, we will review present knowledge on the effects of dissolved inorganic carbon (DIC) availability on photosynthesis and productivity of diatom-dominated MPB. We present evidence of carbon limitation of photosynthesis in benthic diatom mats and highly productive MPB natural communities. Furthermore, we hypothesize that active vertical migration of epipelic motile diatoms could overcome local depletion of DIC in the photic layer, providing the cells alternately with light and inorganic carbon supply. The few available longer-term experiments on the effects of inorganic carbon enrichment on the productivity of diatom-dominated MPB have yielded inconsistent results. Therefore, further studies are needed to properly assess the response of MPB communities to increased CO 2 and ocean acidification related to climate change.This article is part of the themed issue 'The peculiar carbon metabolism in diatoms'. © 2017 The Author(s).

  14. Silicate enamel for alloyed steel

    International Nuclear Information System (INIS)

    Ket'ko, K.K.

    1976-01-01

    The use of silicate enamels in the metallurgical industry is discussed. Presented are the composition and the physico-chemical properties of the silicate enamel developed at the factory 'Krasnyj Oktyabr'. This enamel can be used in the working conditions both in the liquid and the solid state. In so doing the enamel is melted at 1250 to 1300 deg C, granulated and then reduced to a fraction of 0.3 to 0.5 mm. The greatest homogeneity is afforded by a granulated enamel. The trials have shown that the conversion of the test ingots melted under a layer of enamel leads to the smaller number of the ingots rejected for surface defect reasons and the lower metal consumption for slab cleaning. The cost of the silicate enamel is somewhat higher than that of synthetic slags but its application to the melting of stainless steels is still economically beneficial and technologically reasonable. Preliminary calculations only for steel EhI4IEh have revealed that the use of this enamel saves annually over 360000 roubles [ru

  15. Transparent Exopolymeric Particles (TEP Selectively Increase Biogenic Silica Dissolution From Fossil Diatoms as Compared to Fresh Diatoms

    Directory of Open Access Journals (Sweden)

    Jordan Toullec

    2018-03-01

    Full Text Available Diatom production is mainly supported by the dissolution of biogenic silica (bSiO2 within the first 200 m of the water column. The upper oceanic layer is enriched in dissolved and/or colloidal organic matter, such as exopolymeric polysaccharides (EPS and transparent exopolymeric particles (TEP excreted by phytoplankton in large amounts, especially at the end of a bloom. In this study we explored for the first time the direct influence of TEP-enriched diatom excretions on bSiO2 dissolution. Twelve dissolution experiments on fresh and fossil diatom frustules were carried out on seawater containing different concentrations of TEP extracted from diatom cultures. Fresh diatom frustules were cleaned from the organic matter by low ash temperature, and fossil diatoms were made from diatomite powder. Results confirm that newly formed bSiO2 dissolved at a faster rate than fossil diatoms due to a lower aluminum (Al content. Diatom excretions have no effect on the dissolution of the newly formed bSiO2 from Chaetoceros muelleri. Reversely, the diatomite specific dissolution rate constant and solubility of the bSiO2 were positively correlated to TEP concentrations, suggesting that diatom excretion may provide an alternative source of dSi when limitations arise.

  16. Climatically-controlled siliceous productivity in the eastern Gulf of Guinea during the last 40 000 yr

    Directory of Open Access Journals (Sweden)

    X. Crosta

    2012-03-01

    Full Text Available Opal content and diatom assemblages were analysed in core GeoB4905-4 to reconstruct siliceous productivity changes in the eastern Gulf of Guinea during the last 40 000 yr. Opal and total diatom accumulation rates presented low values over the considered period, except during the Last Glacial Maximum and between 15 000 calendar years Before Present (15 cal. ka BP and 5.5 cal. ka BP, the so-called African Humid Period, when accumulation rates of brackish and freshwater diatoms at the core site were highest. Conversely, accumulation rates of windblown diatoms exhibited an opposite pattern with higher values before and after the African Humid Period and greatest values during Heinrich Events, the Younger Dryas and since 5.5 cal. ka BP.

    Our results demonstrate that siliceous productivity in the eastern Gulf of Guinea was directly driven by the nutrient load from local rivers, whose discharges were forced by precipitation changes over western Equatorial Africa and/or modification of the fluvio-deltaic systems forced by sea level changes. Precipitation in this region is controlled by the West African monsoon which is, in turn, partly dependent on the presence and intensity of the Atlantic Cold Tongue (ACT. Our results therefore suggest that the ACT was weakened, warmer trade winds were less vigorous, and cloud convection and precipitation were greater during the AHP though centennial-to-millennial timescale dry events were observed at ∼10 cal. ka BP, ∼8.5 cal. ka BP and ∼6 cal. ka BP. Conversely, the ACT was more intense, trade winds were more vigorous and African climate was more arid during H1, the Younger Dryas and after 5.5 cal. ka BP into the present.

  17. Diatom community structure on in-service cruise ship hulls.

    Science.gov (United States)

    Hunsucker, Kelli Zargiel; Koka, Abhishek; Lund, Geir; Swain, Geoffrey

    2014-10-01

    Diatoms are an important component of marine biofilms found on ship hulls. However, there are only a few published studies that describe the presence and abundance of diatoms on ships, and none that relate to modern ship hull coatings. This study investigated the diatom community structure on two in-service cruise ships with the same cruise cycles, one coated with an antifouling (AF) system (copper self-polishing copolymer) and the other coated with a silicone fouling-release (FR) system. Biofilm samples were collected during dry docking from representative areas of the ship and these provided information on the horizontal and vertical zonation of the hull, and intact and damaged coating and niche areas. Diatoms from the genera Achnanthes, Amphora and Navicula were the most common, regardless of horizontal ship zonation and coating type. Other genera were abundant, but their presence was more dependent on the ship zonation and coating type. Samples collected from damaged areas of the hull coating had a similar community composition to undamaged areas, but with higher diatom abundance. Diatom fouling on the niche areas differed from that of the surrounding ship hull and paralleled previous studies that investigated differences in diatom community structure on static and dynamically exposed coatings; niche areas were similar to static immersion and the hull to dynamic immersion. Additionally, diatom richness was greater on the ship with the FR coating, including the identification of several new genera to the biofouling literature, viz. Lampriscus and Thalassiophysa. These results are the first to describe diatom community composition on in-service ship hulls coated with a FR system. This class of coatings appears to have a larger diatom community compared to copper-based AF systems, with new diatom genera that have the ability to stick to ship hulls and withstand hydrodynamic forces, thus creating the potential for new problematic species in the biofilm.

  18. Role of Diatoms in marine biofouling

    Digital Repository Service at National Institute of Oceanography (India)

    Anil, A; Patil, J.S..; Mitbavkar, S.; DeCosta, P.M.; DeSilva, S.; Hegde, S.; Naik, R.

    . Ltd., New Delhi, pp. 293-6. de Nys, R., Leya, T., Maximilien, R., Afsar, A., Nair, P. S. R. & Steinberg, P. D. 1996. The need for standardized broad scale bioassay testing: a case study using the red alga Laurencia rigida. Biofouling 10:213-24. de...-1 Content-Type text/plain; charset=ISO-8859-1 Recent Advances on Applied Aspects of Indian Marine Algae with Reference to Global Scenario, Volume 1, A. Tewari (Ed.), 2006 Central Salt & Marine Chemicals Research Institute Role of Diatoms...

  19. Digitisation of the South African diatom collection

    CSIR Research Space (South Africa)

    Van

    2008-06-01

    Full Text Available stream_source_info van der Molen_2008.pdf.txt stream_content_type text/plain stream_size 1285 Content-Encoding UTF-8 stream_name van der Molen_2008.pdf.txt Content-Type text/plain; charset=UTF-8 Digitisation... of the South African Diatom Collection Johan van der Molen, CSIR Background ➲ Since 1950 ➲ Properly curated ➲ In dis-use since ~1990 ➲ Renewed interest since ~2004 ➲ Water bodies in Southern Africa, mostly rivers ➲ Supports taxonomic work and biological...

  20. Trophic Cascading of Medusae on the Relationships between Copepods and Diatoms in a Subtropical Coastal Ecosystem

    Directory of Open Access Journals (Sweden)

    Jia-Lu Chung

    2009-01-01

    Full Text Available To investigate the spatial and temporal variation of phytoplankton and copepods, eight seasonal cruises (January 2005 ~ Oc to ber 2006 were conducted in a subtropical coast site that encom passed 19 sampling stations. The results in dicated that the temperature (18.4 - 29.7°C varied more than 10°C seasonally, while nutrient concentrations (ni trate: 0.4 - 6.3 mM, phosphate: 0.1 - 0.8 mM, and silicate 2.1 - 12.1 mM were in versely corre lated with temperature. Diatoms (2792 - 1602437 cells m-3 constituted > 90% of the phytoplankton as semblages and dinoflagellates (226 - 10029 cells m-3 represented only ~10% of the algaebiomass. Copepod abun dance (8 - 1031 ind. m-3 varied positively with that of diatom and tempeature. Therelative abundance of Temora spp. (1 - 712 ind. m-3 varied from 69% in summer; that of Paracalanus spp. (0.1 - 176 ind. m-3 were > 25% in spring and au tumn and Calanus spp. (0.5 - 24 ind. m-3 dom i nated in win ter and spring, but ac counted for only ~10% of the to tal copepods. Both di a tom den sity and copepod abun dance were positively correlated with temperature, indicating these two plank tongroups were left bot tom-up control. The copepod abun dance positively co-aried with diatoms in 2005, but not in 2006. Fur ther sea son-to-sea son analysis showed that the diatomvs. copepodratios changed positively only when the medusa abun dance changed greatly (> 40-fold between consecutive sea sons. During periods when the medusa abundance varied less than 10-fold between seasons, there is no relationship between the ratios and the medusa abun dance. This study suggests that the stability of the medusa abundance from season to season could be important in regulating the ecological linkage between diatoms and their predators ¡V copepods.

  1. The relevance of diatoms for water quality assessment in South ...

    African Journals Online (AJOL)

    Water quality assessment protocols based on the use of diatoms are now well developed and their value substantiated at an international level. The use of diatoms is not designed or intended to be a “rapid” technology. The detailed level of information generated from the procedure outweighs perceived disadvantages of ...

  2. Epiphytic Diatoms along Environmental Gradients in Western European Shallow Lakes

    NARCIS (Netherlands)

    Blanco, Saul; Cejudo-Figueiras, Cristina; Alvarez-Blanco, Irene; van Donk, Ellen|info:eu-repo/dai/nl/069838593; Gross, Elisabeth M.; Hansson, Lars-Anders; Irvine, Kenneth; Jeppesen, Erik; Kairesalo, Timo; Moss, Brian; Noges, Tiina; Becares, Eloy

    Diatom-based assays have been successfully associated worldwide with the tropic status of lakes. Several studies have demonstrated a correlation between epiphytic diatoms and nutrient load in shallow lakes and wetlands. We examine the relative importance of environmental factors in explaining the

  3. Colonization of diatom aggregates by the dinoflagellate Noctiluca scintillans

    DEFF Research Database (Denmark)

    Tiselius, P.; Kiørboe, Thomas

    1998-01-01

    coagulation of diatom cells and not by mucus feeding behavior of N. scintillans. N. scintillans can be positively buoyant, and estimates of encounter rates between N. scintillans and diatom aggregates during ascent demonstrates that this mechanism is sufficient to account for the observed colonization...

  4. Diatom-based water quality monitoring in southern Africa ...

    African Journals Online (AJOL)

    The purpose of this review is to summarise the challenges and future prospects associated with biological water quality monitoring using diatoms with special focus on southern Africa. Much work still needs to be carried out on diatom tolerances, ecological preferences and ecophysiology. It is recommended that past ...

  5. Diatom distribution in the surficial sediments of Lake Fuxian, Yunnan ...

    African Journals Online (AJOL)

    ajl yemi

    2011-11-30

    Nov 30, 2011 ... The diatom abundances per gram dry weight sediment vary between 18.4 × 106 and 66.9 × 106 valves (Figure 2). Abundances per gram dry weight of the eight most abundant diatom taxa are shown in Figure 3. The DCA diagram shows centroids of ecoregions in the ordination space of the first axes.

  6. Interference patterns and extinction ratio of the diatom Coscinodiscus granii

    DEFF Research Database (Denmark)

    Maibohm, Christian; Friis, Søren Michael Mørk; Ellegaard, M.

    2015-01-01

    We report experimental and theoretical verification of the nature and position of multiple interference points of visible light transmitted through the valve of the centric diatom species Coscinodiscus granii. Furthermore, by coupling the transmitted light into an optical fiber and moving...... the diatom valve between constructive and destructive interference points, an extinction ratio of 20 dB is shown...

  7. The health of benthic diatom assemblages in lower stretch

    Indian Academy of Sciences (India)

    This study examines the ecological state of epilithic diatom assemblages along the lower stretch of Mandakini, a glacier-fed Himalayan river. The diatoms were sampled at four stations during winter and summer, only once in each season. Valve counts were obtained from Naphrax mounts prepared from each sample.

  8. Influence of diatom diversity on the ocean biological carbon pump

    Science.gov (United States)

    Tréguer, Paul; Bowler, Chris; Moriceau, Brivaela; Dutkiewicz, Stephanie; Gehlen, Marion; Aumont, Olivier; Bittner, Lucie; Dugdale, Richard; Finkel, Zoe; Iudicone, Daniele; Jahn, Oliver; Guidi, Lionel; Lasbleiz, Marine; Leblanc, Karine; Levy, Marina; Pondaven, Philippe

    2018-01-01

    Diatoms sustain the marine food web and contribute to the export of carbon from the surface ocean to depth. They account for about 40% of marine primary productivity and particulate carbon exported to depth as part of the biological pump. Diatoms have long been known to be abundant in turbulent, nutrient-rich waters, but observations and simulations indicate that they are dominant also in meso- and submesoscale structures such as fronts and filaments, and in the deep chlorophyll maximum. Diatoms vary widely in size, morphology and elemental composition, all of which control the quality, quantity and sinking speed of biogenic matter to depth. In particular, their silica shells provide ballast to marine snow and faecal pellets, and can help transport carbon to both the mesopelagic layer and deep ocean. Herein we show that the extent to which diatoms contribute to the export of carbon varies by diatom type, with carbon transfer modulated by the Si/C ratio of diatom cells, the thickness of the shells and their life strategies; for instance, the tendency to form aggregates or resting spores. Model simulations project a decline in the contribution of diatoms to primary production everywhere outside of the Southern Ocean. We argue that we need to understand changes in diatom diversity, life cycle and plankton interactions in a warmer and more acidic ocean in much more detail to fully assess any changes in their contribution to the biological pump.

  9. Isolation of diatom Navicula cryptocephala and characterization of ...

    African Journals Online (AJOL)

    sjce

    synthesis to the storage of neutral lipids (Qiang et al.,. 2008). Diatoms were shown ... chemical analysis of the oil inside diatom oil droplets, a method for separating ... 120°C for 20 min. 0.1 mg.L. −1. Thiamine, 0.5 μg.L. −1. Biotin and 0.5 μg.L−1.

  10. Calcium and magnesium silicate hydrates

    International Nuclear Information System (INIS)

    Lothenbach, B.; L'Hopital, E.; Nied, D.; Achiedo, G.; Dauzeres, A.

    2015-01-01

    Deep geological disposals are planed to discard long-lived intermediate-level and high-level radioactive wastes. Clay-based geological barriers are expected to limit the ingress of groundwater and to reduce the mobility of radioelements. In the interaction zone between the cement and the clay based material alteration can occur. Magnesium silicate hydrates (M-S-H) have been observed due to the reaction of magnesium sulfate containing groundwater with cements or in the interaction zone between low-pH type cement and clays. M-S-H samples synthesized in the laboratory showed that M-S-H has a variable composition within 0.7 ≤ Mg/Si ≤ 1.5. TEM/EDS analyses show an homogeneous gel with no defined structure. IR and 29 Si NMR data reveal a higher polymerization degree of the silica network in M-S-H compared to calcium silicate hydrates (C-S-H). The presence of mainly Q 3 silicate tetrahedrons in M-S-H indicates a sheet like or a triple-chain silica structure while C-S-H is characterised by single chain-structure. The clear difference in the silica structure and the larger ionic radius of Ca 2+ (1.1 Angstrom) compared to Mg 2+ (0.8 Angstrom) make the formation of an extended solid solution between M-S-H and C-S-H gel improbable. In fact, the analyses of synthetic samples containing both magnesium and calcium in various ratios indicate the formation of separate M-S-H and C-S-H gels with no or very little uptake of magnesium in CS-H or calcium in M-S-H

  11. Microfossil and Fourier transform infrared analyses of Lapita and post-Lapita human dental calculus from Vanuatu, southwest Pacific

    International Nuclear Information System (INIS)

    Horrocks, M.; Nieuwoudt, M.K.; Kinaston, R.; Buckley, H.; Bedford, S.

    2014-01-01

    Here we report on microfossil analysis of human dental calculus from Lapita (3000-2600 yr BP) and post-Lapita (2300-2000 yr BP) burials from Vao and Uripiv, Vanuatu. Phytoliths of introduced Musa and indigenous Heliconia in the calculus suggest the use of these taxa as food wrappings. Phytoliths and most other material in the calculus, namely sponge spicules, calcium oxalate crystals, xylem and charcoal, are unequivocal identifications. Another type of material, comprising degraded objects with a general morphology suggesting starch grains, is uncertain, however, as the unequivocal starch indicator, the Maltese cross, was not observed. We used a new method for calculus analysis, Fourier Transform InfraRed spectroscopy (FTIR), comparing the suspected starch with modern reference starch of prehistoric Pacific crops. Although the ancient FTIR analysis was limited to a small number of suspected starch grains, the results provide another line of evidence for starch. The calculus data are consistent with previous microfossil studies of Lapita deposits at the sites, and demonstrate the efficacy of this technique in contributing to the definition of the history of plant use and diet of early Pacific Island populations. (author)

  12. Characteristics of microfossils assemblages of core SB-01 from Sanshui basin and discussion of paleocene-eocene boundary

    International Nuclear Information System (INIS)

    Chen Liang; Xie Yecai; Wang Zhengqing; Ma Chuang

    2011-01-01

    Characteristics of microfossils assemblages of core SB-01 from Sanshui Basin have been analysised in this paper. Based on micropaleontological study and data from carbon and oxygen isotopes of bulk carbonates, which depth of Paleocene-Eocene boundary from the core was discussed. Ostracode assemblages include the Sinocypris nitela-Cyprois buxinensis-Limnocythere honggangensis assemblage(89.0-73.38 m) with few species and low abundance and the Sinocypris nitela-Cyprois buxinensis-Limnocythere honggangensis assemblage (73.38-0 m) with few species and low abundance during early and middle the core deposition and relatively many species and abundance increasing quickly of the late time of the core deposition; Charophyte assemblages contain the Peckichara subspherica-Rhabdochara jiangduensis assemblage (89.0-73.38 m) with rich species, high abundance and large sizes of fossils and the Gyrogona qianjiangica-Obtusochara brevicylindrica assemblage (73.38-53.75 m) with few species,low abundance and small sizes of fossils. At 73.38 m core depth, the great changes of microfossils assemblages and carbon isotopes values (decrease by more than 3.0 per thousand) and oxygen isotopes values of bulk carbonates take place, which consist with the geological records of the Paleocene-Eocene Thermal Maximum (PETM). Hence, Paleocene-Eocene boundary of SanShui Basin should be roughly placed at 73.38 m core depth. (authors)

  13. Applications of Diatoms as Potential Microalgae in Nanobiotechnology

    Directory of Open Access Journals (Sweden)

    Ahmad Yari Khosroushahi

    2012-05-01

    Full Text Available Introduction: Diatoms are single cell eukaryotic microalgae, which present in nearly every water habitat make them ideal tools for a wide range of applications such as oil explora­tion, forensic examination, environmental indication, biosilica pattern generation, toxicity testing and eutrophication of aqueous ecosystems. Methods: Essential information on diatoms were reviewed and discussed towards impacts of diatoms on biosynthesis and bioremediation. Results: In this review, we present the recent progress in this century on the application of diatoms in waste degradation, synthesis of biomaterial, biomineraliza­tion, toxicity and toxic effects of mineral elements evaluations. Conclusion: Diatoms can be considered as metal toxicity bioindicators and they can be applied for biomineralization, synthesis of biomaterials, and degradation of wastes.

  14. Isolation and biochemical characterization of underwater adhesives from diatoms.

    Science.gov (United States)

    Poulsen, Nicole; Kröger, Nils; Harrington, Matthew J; Brunner, Eike; Paasch, Silvia; Buhmann, Matthias T

    2014-01-01

    Many aquatic organisms are able to colonize surfaces through the secretion of underwater adhesives. Diatoms are unicellular algae that have the capability to colonize any natural and man-made submerged surfaces. There is great technological interest in both mimicking and preventing diatom adhesion, yet the biomolecules responsible have so far remained unidentified. A new method for the isolation of diatom adhesive material is described and its amino acid and carbohydrate composition determined. The adhesive materials from two model diatoms show differences in their amino acid and carbohydrate compositions, but also share characteristic features including a high content of uronic acids, the predominance of hydrophilic amino acid residues, and the presence of 3,4-dihydroxyproline, an extremely rare amino acid. Proteins containing dihydroxyphenylalanine, which mediate underwater adhesion of mussels, are absent. The data on the composition of diatom adhesives are consistent with an adhesion mechanism based on complex coacervation of polyelectrolyte-like biomolecules.

  15. Epibiotic Diatoms Are Universally Present on All Sea Turtle Species.

    Directory of Open Access Journals (Sweden)

    Nathan J Robinson

    Full Text Available The macro-epibiotic communities of sea turtles have been subject to growing interest in recent years, yet their micro-epibiotic counterparts are almost entirely unknown. Here, we provide the first evidence that diatoms are epibionts for all seven extant species of sea turtle. Using Scanning Electron Microscopy, we inspected superficial carapace or skin samples from a single representative of each turtle species. We distinguished 18 diatom taxa from these seven individuals, with each sea turtle species hosting at least two diatom taxa. We recommend that future research is undertaken to confirm whether diatom communities vary between sea turtle species and whether these diatom taxa are facultative or obligate commensals.

  16. Aggregate Formation During the Viral Lysis of a Marine Diatom

    Directory of Open Access Journals (Sweden)

    Yosuke Yamada

    2018-05-01

    Full Text Available Recent studies have suggested that the viral lysis of microbes not only facilitates the conversion of particulate organic matter into dissolved organic matter, but also promotes the formation of organic aggregates, which enhance the export of organic carbon from the surface ocean to the deep sea. However, experimental data supporting this proposition are limited. Here, we tested the hypothesis that the viral infection of marine diatoms enhances aggregate formation. We used a model system consisting of Chaetoceros tenuissimus, a bloom-forming diatom with an approximate cell size of 3–10 μm, and a DNA virus, CtenDNAV type II, which replicates in the nucleus of C. tenuissimus. The volume of large particles (50–400 μm in equivalent spherical diameters, determined from photographic images was measured over time (up to 15 days in the diatom-alone control and a virus-added diatom culture. We also determined the concentrations of Coomassie-stainable particles (CSP, proteinaceous particles and transparent exopolymeric particles (TEP, acid-polysaccharide-rich particles with colorimetric methods. The total volume of large particles was significantly higher (5–59 fold in the virus-added diatoms than in the diatom-alone control during the period in which the viral lysis of the diatoms proceeded. One class of large particles produced in the virus-added diatoms was flake-shaped. The flakes were tightly packed and dense, and sank rapidly, possibly playing an important role in the vertical delivery of materials from the surface to the deep sea. The bulk CSP concentrations tended to be higher in the virus-added diatoms than in the diatom-alone control, whereas the reverse was true for the TEP. These results suggest that proteinaceous polymers are involved in aggregate formation. Our data support the emerging notion that the viral lysis of microbes facilitates aggregate formation and the export of organic carbon in the ocean.

  17. Coupled states approximation for scattering of two diatoms

    International Nuclear Information System (INIS)

    Heil, T.G.; Green, S.; Kouri, D.J.

    1978-01-01

    The coupled states (CS) approximation is developed in detail for the general case of two colliding diatomic molecules. The high energy limit of the exact Lippmann-Schwinger equation is used to obtain the CS equations so that the sufficiency conditions of Kouri, Heil, and Shimoni apply. In addition, care is taken to ensure correct treatment of parity in the CS, as well as correct labeling of the CS by an effective orbital angular momentum. The analysis follows that given by Shimoni and Kouri for atom-diatom collisions where the coupled rotor angular momentum j 12 and projection lambda 12 replace the single diatom angular momentum j and projection lambda. The result is an expression for the differential scattering amplitude which is a generalization of the highly successful McGuire-Kouri differential scattering amplitude for atom-diatom collisions. Also, the opacity function is found to be a generalization of the Clebsch-Gordon weight atom-diatom expression of Shimoni and Kouri. The diatom-diatom CS body frame T matrix T/sup J/(j 1 'j 2 'j 12 'lambda 12 'vertical-bar j 1 j 2 j 12 lambda 12 ) is also found to be nondiagonal in lambda' 12 ,lambda 12 , just as in the atom-diatom case. The parity and identical molecule interchange symmetries are also considered in detail in both the exact close coupling and CS approximations. Symmetrized expressions for all relevant quantities are obtained, along with the symmetrized coupled equations one must solve. The properly labeled and symmetrized CS equations have not been derived before this present work. The present correctly labeled CS theory is tested computationally by applications to three different diatom-diatom potentials. First we carry out calculations for para-para, ortho-ortho, and ortho-para H 2 -H 2 collisions using the experimental potential of Farrar and Lee

  18. Variation partitioning of diatom species data matrices: Understanding the influence of multiple factors on benthic diatom communities in tropical streams

    Energy Technology Data Exchange (ETDEWEB)

    Bere, Taurai, E-mail: tbere2015@gmail.com; Mangadze, Tinotenda; Mwedzi, Tongai

    2016-10-01

    Elucidating the confounding influence of multiple environmental factors on benthic diatom communities is important in developing water quality predictive models for better guidance of stream management efforts. The objective of this study was to explore the relative impact of metal pollution and hydromorphological alterations in, addition to nutrient enrichment and organic pollution, on diatom taxonomic composition with the view to improve stream diatom-based water quality inference models. Samples were collected twice at 20 sampling stations in the tropical Manyame Catchment, Zimbabwe. Diatom, macroinvertebrate communities and environmental factors were sampled and analysed. The variations in diatom community composition explained by different categories of environmental factors were analysed using canonical correspondence analysis using variance partitioning (partial CCA). The following variations were explained by the different predictor matrices: nutrient levels and organic pollution - 10.4%, metal pollution - 8.3% and hydromorphological factors - 7.9%. Thus, factors other than nutrient levels and organic pollution explain additional significant variation in these diatom communities. Development of diatom-based stream water quality inference models that incorporate metal pollution and hydromorphological alterations, where these are key issues, is thus deemed necessary. - Highlights: • Confounding influences of multiple environmental factors on diatom communities are elucidated. • Variation explained: nutrients + organic pollution - 10.4%, metals - 8.3% and hydromorphological factors - 7.9%. • Calibration of existing or development of new indices may be necessary.

  19. Variation partitioning of diatom species data matrices: Understanding the influence of multiple factors on benthic diatom communities in tropical streams

    International Nuclear Information System (INIS)

    Bere, Taurai; Mangadze, Tinotenda; Mwedzi, Tongai

    2016-01-01

    Elucidating the confounding influence of multiple environmental factors on benthic diatom communities is important in developing water quality predictive models for better guidance of stream management efforts. The objective of this study was to explore the relative impact of metal pollution and hydromorphological alterations in, addition to nutrient enrichment and organic pollution, on diatom taxonomic composition with the view to improve stream diatom-based water quality inference models. Samples were collected twice at 20 sampling stations in the tropical Manyame Catchment, Zimbabwe. Diatom, macroinvertebrate communities and environmental factors were sampled and analysed. The variations in diatom community composition explained by different categories of environmental factors were analysed using canonical correspondence analysis using variance partitioning (partial CCA). The following variations were explained by the different predictor matrices: nutrient levels and organic pollution - 10.4%, metal pollution - 8.3% and hydromorphological factors - 7.9%. Thus, factors other than nutrient levels and organic pollution explain additional significant variation in these diatom communities. Development of diatom-based stream water quality inference models that incorporate metal pollution and hydromorphological alterations, where these are key issues, is thus deemed necessary. - Highlights: • Confounding influences of multiple environmental factors on diatom communities are elucidated. • Variation explained: nutrients + organic pollution - 10.4%, metals - 8.3% and hydromorphological factors - 7.9%. • Calibration of existing or development of new indices may be necessary.

  20. Importance of sampling frequency when collecting diatoms

    KAUST Repository

    Wu, Naicheng

    2016-11-14

    There has been increasing interest in diatom-based bio-assessment but we still lack a comprehensive understanding of how to capture diatoms’ temporal dynamics with an appropriate sampling frequency (ASF). To cover this research gap, we collected and analyzed daily riverine diatom samples over a 1-year period (25 April 2013–30 April 2014) at the outlet of a German lowland river. The samples were classified into five clusters (1–5) by a Kohonen Self-Organizing Map (SOM) method based on similarity between species compositions over time. ASFs were determined to be 25 days at Cluster 2 (June-July 2013) and 13 days at Cluster 5 (February-April 2014), whereas no specific ASFs were found at Cluster 1 (April-May 2013), 3 (August-November 2013) (>30 days) and Cluster 4 (December 2013 - January 2014) (<1 day). ASFs showed dramatic seasonality and were negatively related to hydrological wetness conditions, suggesting that sampling interval should be reduced with increasing catchment wetness. A key implication of our findings for freshwater management is that long-term bio-monitoring protocols should be developed with the knowledge of tracking algal temporal dynamics with an appropriate sampling frequency.

  1. Silicate bonded ceramics of laterites

    International Nuclear Information System (INIS)

    Wagh, A.S.; Douse, V.

    1989-05-01

    Sodium silicate is vacuum impregnated in bauxite waste (red mud) at room temperature to develop ceramics of mechanical properties comparable to the sintered ceramics. For a concentration up to 10% the fracture toughness increases from 0.12 MNm -3/2 to 0.9 MNm -3/2 , and the compressive strength from 7 MNm -2 to 30 MNm -2 . The mechanical properties do not deteriorate, when soaked in water for an entire week. The viscosity and the concentration of the silicate solution are crucial, both for the success of the fabrication and the economics of the process. Similar successful results have been obtained for bauxite and lime stone, even though the latter has poor weathering properties. With scanning electron microscopy and energy dispersive analysis, an attempt is made to identify the crystals formed in the composite, which are responsible for the strength. The process is an economic alternative to the sintered ceramics in the construction industry in the tropical countries, rich in lateritic soils and poor in energy. Also the process has all the potential for further development in arid regions abundant in limestone. (author). 6 refs, 20 figs, 3 tabs

  2. Radiation effects in silicate glasses

    International Nuclear Information System (INIS)

    Bibler, N.E.; Howitt, D.G.

    1988-01-01

    The study of radiation effects in complex silicate glasses has received renewed attention because of their use in special applications such as high level nuclear waste immobilization and fiber optics. Radiation changes the properties of these glasses by altering their electronic and atomic configurations. These alterations or defects may cause dilatations or microscopic phase changes along with absorption centers that limit the optical application of the glasses. Atomic displacements induced in the already disordered structure of the glasses may affect their use where heavy irradiating particles such as alpha particles, alpha recoils, fission fragments, or accelerated ions are present. Large changes (up to 1%) in density may result. In some cases the radiation damage may be severe enough to affect the durability of the glass in aqueous solutions. In the paper, the authors review the literature concerning radiation effects on density, durability, stored energy, microstructure and optical properties of silicate glasses. Both simple glasses and complex glasses used for immobilization of nuclear waste are considered

  3. Silicates materials of high vacuum technology

    CERN Document Server

    Espe, Werner

    2013-01-01

    Materials of High Vacuum Technology, Volume 2: Silicates covers silicate insulators of special importance to vacuum technology. The book discusses the manufacture, composition, and physical and chemical properties of technical glasses, quartz glass, quartzware, vycor glass, ceramic materials, mica, and asbestos.

  4. Diatoms from a peat bog on the Pešter plateau (southwestern Serbia: New records for diatom flora of Serbia

    Directory of Open Access Journals (Sweden)

    Vidaković Danijela

    2016-01-01

    Full Text Available The distribution of diatoms was studied in three types of diatom communities (epiphytes, benthos and plankton of a peat bog on the Pešter plateau. The observed diatom flora inhabited all investigated communities, comprising in total 250 taxa in 53 genera. Among them, 45 taxa were new records for the Serbian diatom flora. Identified taxa belonged to different groups of algae, however alkaliphile diatoms were dominant. New ecological data for Encyonopsis minuta, Pinnularia isostauron and P. marchica are presented here. All the diatoms were documented by light micrographs, and brief notes on their morphology, distribution and ecology are provided. [Projekat Ministarstva nauke Republike Srbije, br. TR 037009

  5. Codon adaptation and synonymous substitution rate in diatom plastid genes.

    Science.gov (United States)

    Morton, Brian R; Sorhannus, Ulf; Fox, Martin

    2002-07-01

    Diatom plastid genes are examined with respect to codon adaptation and rates of silent substitution (Ks). It is shown that diatom genes follow the same pattern of codon usage as other plastid genes studied previously. Highly expressed diatom genes display codon adaptation, or a bias toward specific major codons, and these major codons are the same as those in red algae, green algae, and land plants. It is also found that there is a strong correlation between Ks and variation in codon adaptation across diatom genes, providing the first evidence for such a relationship in the algae. It is argued that this finding supports the notion that the correlation arises from selective constraints, not from variation in mutation rate among genes. Finally, the diatom genes are examined with respect to variation in Ks among different synonymous groups. Diatom genes with strong codon adaptation do not show the same variation in synonymous substitution rate among codon groups as the flowering plant psbA gene which, previous studies have shown, has strong codon adaptation but unusually high rates of silent change in certain synonymous groups. The lack of a similar finding in diatoms supports the suggestion that the feature is unique to the flowering plant psbA due to recent relaxations in selective pressure in that lineage.

  6. Effect of the Silica Content of Diatoms on Protozoan Grazing

    Directory of Open Access Journals (Sweden)

    Shuwen Zhang

    2017-06-01

    Full Text Available This study examined the effect that silica content in diatom cells has on the behavior of protists. The diatoms Thalassiosira weissflogii and T. pseudonana were cultured in high or low light conditions to achieve low and high silica contents, respectively. These cells were then fed to a heterotrophic dinoflagellate Noctiluca scintillans and a ciliate Euplotes sp. in single and mixed diet experiments. Our results showed that in general, N. scintillans and Euplotes sp. both preferentially ingested the diatoms with a low silica content rather than those with a high silica content. However, Euplotes sp. seemed to be less influenced by the silica content than was N. scintillans. In the latter case, the clearance and ingestion rate of the low silica diatoms were significantly higher, both in the short (6-h and long (1-d duration grazing experiments. Our results also showed that N. scintillans required more time to digest the high silica-containing cells. As the high silica diatoms are harder to digest, this might explain why N. scintillans exhibits a strong preference for the low silica prey. Thus, the presence of high silica diatoms might limit the ability of the dinoflagellate to feed. Our findings suggest that the silica content of diatoms affects their palatability and digestibility and, consequently, the grazing activity and selectivity of protozoan grazers.

  7. A morphogram for silica-witherite biomorphs and its application to microfossil identification in the early earth rock record.

    Science.gov (United States)

    Rouillard, J; García-Ruiz, J-M; Gong, J; van Zuilen, M A

    2018-05-01

    Archean hydrothermal environments formed a likely site for the origin and early evolution of life. These are also the settings, however, were complex abiologic structures can form. Low-temperature serpentinization of ultramafic crust can generate alkaline, silica-saturated fluids in which carbonate-silica crystalline aggregates with life-like morphologies can self-assemble. These "biomorphs" could have adsorbed hydrocarbons from Fischer-Tropsch type synthesis processes, leading to metamorphosed structures that resemble carbonaceous microfossils. Although this abiogenic process has been extensively cited in the literature and has generated important controversy, so far only one specific biomorph type with a filamentous shape has been discussed for the interpretation of Archean microfossils. It is therefore critical to precisely determine the full distribution in morphology and size of these biomorphs, and to study the range of plausible geochemical conditions under which these microstructures can form. Here, a set of witherite-silica biomorph synthesis experiments in silica-saturated solutions is presented, for a range of pH values (from 9 to 11.5) and barium ion concentrations (from 0.6 to 40 mmol/L BaCl 2 ). Under these varying conditions, a wide range of life-like structures is found, from fractal dendrites to complex shapes with continuous curvature. The size, spatial concentration, and morphology of the biomorphs are strongly controlled by environmental parameters, among which pH is the most important. This potentially limits the diversity of environments in which the growth of biomorphs could have occurred on Early Earth. Given the variety of the observed biomorph morphologies, our results show that the morphology of an individual microstructure is a poor criterion for biogenicity. However, biomorphs may be distinguished from actual populations of cellular microfossils by their wide, unimodal size distribution. Biomorphs grown by diffusion in silica gel can

  8. Stable isotope analysis of Dacryoconarid carbonate microfossils: a new tool for Devonian oxygen and carbon isotope stratigraphy.

    Science.gov (United States)

    Frappier, Amy Benoit; Lindemann, Richard H; Frappier, Brian R

    2015-04-30

    Dacryoconarids are extinct marine zooplankton known from abundant, globally distributed calcite microfossils in the Devonian, but their shell stable isotope composition has not been previously explored. Devonian stable isotope stratigraphy is currently limited to less common invertebrates or bulk rock analyses of uncertain provenance. As with Cenozoic planktonic foraminifera, isotopic analysis of dacryoconarid shells could facilitate higher-resolution, geographically widespread stable isotope records of paleoenvironmental change, including marine hypoxia events, climate changes, and biocrises. We explored the use of Dacryoconarid isotope stratigraphy as a viable method in interpreting paleoenvironments. We applied an established method for determining stable isotope ratios (δ(13) C, δ(18) O values) of small carbonate microfossils to very well-preserved dacryoconarid shells. We analyzed individual calcite shells representing five common genera using a Kiel carbonate device coupled to a MAT 253 isotope ratio mass spectrometer. Calcite shell δ(13) C and δ(18) O values were compared by taxonomic group, rock unit, and locality. Single dacryoconarid calcite shells are suitable for stable isotope analysis using a Kiel-IRMS setup. The dacryoconarid shell δ(13) C values (-4.7 to 2.3‰) and δ(18) O values (-10.3 to -4.8‰) were consistent across taxa, independent of shell size or part, but varied systematically through time. Lower fossil δ(18) O values were associated with warmer water temperature and more variable δ(13) C values were associated with major bioevents. Dacryoconarid δ(13) C and δ(18) O values differed from bulk rock carbonate values. Dacryoconarid individual microfossil δ(13) C and δ(18) O values are highly sensitive to paleoenvironmental changes, thus providing a promising avenue for stable isotope chemostratigraphy to better resolve regional to global paleoceanographic changes throughout the upper Silurian to the upper Devonian. Our results

  9. Diatom feeding across trophic guilds in tidal flat nematodes, and the importance of diatom cell size

    Science.gov (United States)

    Moens, Tom; Vafeiadou, Anna-Maria; De Geyter, Ellen; Vanormelingen, Pieter; Sabbe, Koen; De Troch, Marleen

    2014-09-01

    We examine the capacity of nematodes from three feeding types (deposit feeder, epistrate feeder, predator) to utilize microphytobenthos (MPB), and assess whether diatom cell size and consumer body size are important drivers of their feeding. We analyzed natural stable isotope ratios of carbon and nitrogen in abundant nematode genera and a variety of carbon sources at an estuarine intertidal flat. All nematodes had δ13C indicating that MPB is their major carbon source. δ15N, however, demonstrated that only one deposit and one epistrate feeder genus obtained most of their carbon from direct grazing on MPB, whereas other deposit feeders and predators obtained at least part of their carbon by predation on MPB grazers. We then performed a microcosm experiment in which equal cell numbers of each of three differently sized strains of the pennate diatom Seminavis were offered as food to four, one and one genera of deposit feeders, epistrate feeders and predators, respectively. Previous studies have shown that all but the epistrate feeder ingest whole diatoms, whereas the epistrate feeder pierces cells and sucks out their contents. Most genera showed markedly higher carbon absorption from medium and large cells than from small ones. When considering the number of cells consumed, however, none of the nematodes which ingest whole cells exhibited a clear preference for any specific diatom size. The epistrate feeder was the smallest nematode taxon considered here, yet it showed a marked preference for large cells. These results highlight that the feeding mechanism is much more important than consumer size as a driver of particle size selection in nematodes grazing MPB.

  10. Mesoporous Silicate Materials in Sensing

    Directory of Open Access Journals (Sweden)

    Paul T. Charles

    2008-08-01

    Full Text Available Mesoporous silicas, especially those exhibiting ordered pore systems and uniform pore diameters, have shown great potential for sensing applications in recent years. Morphological control grants them versatility in the method of deployment whether as bulk powders, monoliths, thin films, or embedded in coatings. High surface areas and pore sizes greater than 2 nm make them effective as adsorbent coatings for humidity sensors. The pore networks also provide the potential for immobilization of enzymes within the materials. Functionalization of materials by silane grafting or through cocondensation of silicate precursors can be used to provide mesoporous materials with a variety of fluorescent probes as well as surface properties that aid in selective detection of specific analytes. This review will illustrate how mesoporous silicas have been applied to sensing changes in relative humidity, changes in pH, metal cations, toxic industrial compounds, volatile organic compounds, small molecules and ions, nitroenergetic compounds, and biologically relevant molecules.

  11. Comparing optical properties of different species of diatoms

    DEFF Research Database (Denmark)

    Maibohm, Christian; Friis, Søren Michael Mørk; Su, Y.

    2015-01-01

    species dependent with huge variety in size, shape, and micro- structure. We have experimentally investigated optical properties of frustules of several species of diatoms to further understand light harvesting properties together with commo n traits, effects and differences between the different...... analysis software. The software uses parameters which are extracted from experimental im ages as basis for simulation and allows us to extract the influence of the different elements of the frustule. The information could be used both for predicting optical properties of diatoms and by changing frustule...... parameters, maybe by altering growth conditions of the diatoms tailor their optical properties....

  12. A Zeeman slower for diatomic molecules

    Science.gov (United States)

    Petzold, M.; Kaebert, P.; Gersema, P.; Siercke, M.; Ospelkaus, S.

    2018-04-01

    We present a novel slowing scheme for beams of laser-coolable diatomic molecules reminiscent of Zeeman slowing of atomic beams. The scheme results in efficient compression of the one-dimensional velocity distribution to velocities trappable by magnetic or magneto-optical traps. We experimentally demonstrate our method in an atomic testbed and show an enhancement of flux below v = 35 m s‑1 by a factor of ≈20 compared to white light slowing. 3D Monte Carlo simulations performed to model the experiment show excellent agreement. We apply the same simulations to the prototype molecule 88Sr19F and expect 15% of the initial flux to be continuously compressed in a narrow velocity window at around 10 m s‑1. This is the first experimentally shown continuous and dissipative slowing technique in molecule-like level structures, promising to provide the missing link for the preparation of large ultracold molecular ensembles.

  13. Magnetically responsive siliceous frustules for efficient chemotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Javalkote, Vivek S. [Department of Biotechnology, School of Life Sciences, North Maharashtra University, Jalgaon, Maharashtra (India); Pandey, Abhijeet P. [H. R. Patel Institute of Pharmaceutical Education and Research, Shirpur, Maharashtra (India); Puranik, Pravin R. [Department of Biotechnology, School of Life Sciences, North Maharashtra University, Jalgaon, Maharashtra (India); Deshmukh, Prashant K., E-mail: pkdesh@rediffmail.com [H. R. Patel Institute of Pharmaceutical Education and Research, Shirpur, Maharashtra (India)

    2015-05-01

    In the present investigation, curcumin loaded magnetically active frustules have been reported. The diatoms were cultured and frustules were obtained by chemical and thermal processes. The frustules were rendered magnetically active by incorporation of iron oxide nanoparticle using two different methods involving ferrofluid (CMDM-F) and in situ synthesis (CMDM-I) of iron oxide nanoparticle. These CMDM prepared by two techniques were characterized using FT-IR and vibrating sample magnetometer (VSM) analyses. Particle size and potential were measured using the Malvern Zetasizer. Scanning electron microscopy (SEM) was utilized for studying the surface morphology of CMDM, and in addition to this elemental analysis was also performed for confirming the presence of iron. The cell viability assay was carried out using the HeLa cell line. SEM images showed a change in surface morphology of diatoms before and after rendering magnetic activity. Cell viability assay revealed that CMDM-F had reasonably high cytotoxicity (60.2%) compared to Curcumin (42.1%), DM (1.9%), CDM (44.8%), and CMDM-I (59.9). Both, CMDM-F and CMDM-I showed improved cytotoxicity when compared with pure curcumin. The overall study suggests that the developed CMDM could be utilized as a potential carrier to deliver cargo for efficient chemotherapy. - Highlights: • In-lab culture and purification of Diatoms with pore size around 50 nm • A simple one step synthesis of magnetically active Diatoms using ferrofluid which has not been reported till date • Comparative study of magnetically active Diatoms synthesized using ferrofluid method and in situ method • Cell viability study of curcumin loaded magnetically active diatoms.

  14. Magnetically responsive siliceous frustules for efficient chemotherapy

    International Nuclear Information System (INIS)

    Javalkote, Vivek S.; Pandey, Abhijeet P.; Puranik, Pravin R.; Deshmukh, Prashant K.

    2015-01-01

    In the present investigation, curcumin loaded magnetically active frustules have been reported. The diatoms were cultured and frustules were obtained by chemical and thermal processes. The frustules were rendered magnetically active by incorporation of iron oxide nanoparticle using two different methods involving ferrofluid (CMDM-F) and in situ synthesis (CMDM-I) of iron oxide nanoparticle. These CMDM prepared by two techniques were characterized using FT-IR and vibrating sample magnetometer (VSM) analyses. Particle size and potential were measured using the Malvern Zetasizer. Scanning electron microscopy (SEM) was utilized for studying the surface morphology of CMDM, and in addition to this elemental analysis was also performed for confirming the presence of iron. The cell viability assay was carried out using the HeLa cell line. SEM images showed a change in surface morphology of diatoms before and after rendering magnetic activity. Cell viability assay revealed that CMDM-F had reasonably high cytotoxicity (60.2%) compared to Curcumin (42.1%), DM (1.9%), CDM (44.8%), and CMDM-I (59.9). Both, CMDM-F and CMDM-I showed improved cytotoxicity when compared with pure curcumin. The overall study suggests that the developed CMDM could be utilized as a potential carrier to deliver cargo for efficient chemotherapy. - Highlights: • In-lab culture and purification of Diatoms with pore size around 50 nm • A simple one step synthesis of magnetically active Diatoms using ferrofluid which has not been reported till date • Comparative study of magnetically active Diatoms synthesized using ferrofluid method and in situ method • Cell viability study of curcumin loaded magnetically active diatoms

  15. SIMS analyses of the oldest known assemblage of microfossils document their taxon-correlated carbon isotope compositions

    Science.gov (United States)

    Schopf, J. William; Kitajima, Kouki; Spicuzza, Michael J.; Kudryavtsev, Anatoliy B.; Valley, John W.

    2018-01-01

    Analyses by secondary ion mass spectroscopy (SIMS) of 11 specimens of five taxa of prokaryotic filamentous kerogenous cellular microfossils permineralized in a petrographic thin section of the ˜3,465 Ma Apex chert of northwestern Western Australia, prepared from the same rock sample from which this earliest known assemblage of cellular fossils was described more than two decades ago, show their δ13C compositions to vary systematically taxon to taxon from ‑31‰ to ‑39‰. These morphospecies-correlated carbon isotope compositions confirm the biogenicity of the Apex fossils and validate their morphology-based taxonomic assignments. Perhaps most significantly, the δ13C values of each of the five taxa are lower than those of bulk samples of Apex kerogen (‑27‰), those of SIMS-measured fossil-associated dispersed particulate kerogen (‑27.6‰), and those typical of modern prokaryotic phototrophs (‑25 ± 10‰). The SIMS data for the two highest δ13C Apex taxa are consistent with those of extant phototrophic bacteria; those for a somewhat lower δ13C taxon, with nonbacterial methane-producing Archaea; and those for the two lowest δ13C taxa, with methane-metabolizing γ-proteobacteria. Although the existence of both methanogens and methanotrophs has been inferred from bulk analyses of the carbon isotopic compositions of pre-2,500 Ma kerogens, these in situ SIMS analyses of individual microfossils present data interpretable as evidencing the cellular preservation of such microorganisms and are consistent with the near-basal position of the Archaea in rRNA phylogenies.

  16. SIMS analyses of the oldest known assemblage of microfossils document their taxon-correlated carbon isotope compositions.

    Science.gov (United States)

    Schopf, J William; Kitajima, Kouki; Spicuzza, Michael J; Kudryavtsev, Anatoliy B; Valley, John W

    2018-01-02

    Analyses by secondary ion mass spectroscopy (SIMS) of 11 specimens of five taxa of prokaryotic filamentous kerogenous cellular microfossils permineralized in a petrographic thin section of the ∼3,465 Ma Apex chert of northwestern Western Australia, prepared from the same rock sample from which this earliest known assemblage of cellular fossils was described more than two decades ago, show their δ 13 C compositions to vary systematically taxon to taxon from -31‰ to -39‰. These morphospecies-correlated carbon isotope compositions confirm the biogenicity of the Apex fossils and validate their morphology-based taxonomic assignments. Perhaps most significantly, the δ 13 C values of each of the five taxa are lower than those of bulk samples of Apex kerogen (-27‰), those of SIMS-measured fossil-associated dispersed particulate kerogen (-27.6‰), and those typical of modern prokaryotic phototrophs (-25 ± 10‰). The SIMS data for the two highest δ 13 C Apex taxa are consistent with those of extant phototrophic bacteria; those for a somewhat lower δ 13 C taxon, with nonbacterial methane-producing Archaea; and those for the two lowest δ 13 C taxa, with methane-metabolizing γ-proteobacteria. Although the existence of both methanogens and methanotrophs has been inferred from bulk analyses of the carbon isotopic compositions of pre-2,500 Ma kerogens, these in situ SIMS analyses of individual microfossils present data interpretable as evidencing the cellular preservation of such microorganisms and are consistent with the near-basal position of the Archaea in rRNA phylogenies.

  17. SILICATE COMPOSITION OF THE INTERSTELLAR MEDIUM

    Energy Technology Data Exchange (ETDEWEB)

    Fogerty, S.; Forrest, W.; Watson, D. M.; Koch, I. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Sargent, B. A., E-mail: sfogerty@pas.rochester.edu [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States)

    2016-10-20

    The composition of silicate dust in the diffuse interstellar medium and in protoplanetary disks around young stars informs our understanding of the processing and evolution of the dust grains leading up to planet formation. An analysis of the well-known 9.7 μ m feature indicates that small amorphous silicate grains represent a significant fraction of interstellar dust and are also major components of protoplanetary disks. However, this feature is typically modeled assuming amorphous silicate dust of olivine and pyroxene stoichiometries. Here, we analyze interstellar dust with models of silicate dust that include non-stoichiometric amorphous silicate grains. Modeling the optical depth along lines of sight toward the extinguished objects Cyg OB2 No. 12 and ζ Ophiuchi, we find evidence for interstellar amorphous silicate dust with stoichiometry intermediate between olivine and pyroxene, which we simply refer to as “polivene.” Finally, we compare these results to models of silicate emission from the Trapezium and protoplanetary disks in Taurus.

  18. SILICATE COMPOSITION OF THE INTERSTELLAR MEDIUM

    International Nuclear Information System (INIS)

    Fogerty, S.; Forrest, W.; Watson, D. M.; Koch, I.; Sargent, B. A.

    2016-01-01

    The composition of silicate dust in the diffuse interstellar medium and in protoplanetary disks around young stars informs our understanding of the processing and evolution of the dust grains leading up to planet formation. An analysis of the well-known 9.7 μ m feature indicates that small amorphous silicate grains represent a significant fraction of interstellar dust and are also major components of protoplanetary disks. However, this feature is typically modeled assuming amorphous silicate dust of olivine and pyroxene stoichiometries. Here, we analyze interstellar dust with models of silicate dust that include non-stoichiometric amorphous silicate grains. Modeling the optical depth along lines of sight toward the extinguished objects Cyg OB2 No. 12 and ζ Ophiuchi, we find evidence for interstellar amorphous silicate dust with stoichiometry intermediate between olivine and pyroxene, which we simply refer to as “polivene.” Finally, we compare these results to models of silicate emission from the Trapezium and protoplanetary disks in Taurus.

  19. Automated Diatom Classification (Part A: Handcrafted Feature Approaches

    Directory of Open Access Journals (Sweden)

    Gloria Bueno

    2017-07-01

    Full Text Available This paper deals with automatic taxa identification based on machine learning methods. The aim is therefore to automatically classify diatoms, in terms of pattern recognition terminology. Diatoms are a kind of algae microorganism with high biodiversity at the species level, which are useful for water quality assessment. The most relevant features for diatom description and classification have been selected using an extensive dataset of 80 taxa with a minimum of 100 samples/taxon augmented to 300 samples/taxon. In addition to published morphological, statistical and textural descriptors, a new textural descriptor, Local Binary Patterns (LBP, to characterize the diatom’s valves, and a log Gabor implementation not tested before for this purpose are introduced in this paper. Results show an overall accuracy of 98.11% using bagging decision trees and combinations of descriptors. Finally, some phycological features of diatoms that are still difficult to integrate in computer systems are discussed for future work.

  20. Abundance of bacterial and diatom fouling on various surfaces

    Digital Repository Service at National Institute of Oceanography (India)

    PrabhaDevi

    Abundance of bacterial and diatom fouling on aluminium, fibreglass and stainless steel were studied from Dona Paula waters of the Zuari Estuary. Both these forms were reversibly attached in large numbers to surfaces during the initial 24 hr...

  1. A Simplified Quantum Mechanical Model of Diatomic Molecules

    Science.gov (United States)

    Nielsen, Lars Drud

    1978-01-01

    Introduces a simple one-dimensional model of a diatomic molecule that can explain all the essential features of a real two particle quantum mechanical system and gives quantitative results in fair agreement with those of a hydrogen molecule. (GA)

  2. Studies on new antifreeze protein from the psychrophilic diatom ...

    African Journals Online (AJOL)

    Studies on new antifreeze protein from the psychrophilic diatom, Fragilariopsis cylindrus. ... African Journal of Biotechnology. Journal Home · ABOUT THIS ... The predicted gene product, AfpA, had a molecular mass of 27 kDa. Expression of ...

  3. Analytic vibration-rotational matrix elements for diatomic molecules

    International Nuclear Information System (INIS)

    Bouanich, J.P.

    1987-01-01

    The vibration-rotational matrix elements for infrared or Raman transitions vJ → v'J' of diatomic molecules are calculated for powers of the reduced displacement X from parameters of the Dunham potential-energy function. (orig.)

  4. Modified Ribose Receptor Response in Isolated Diatom Frustules

    Energy Technology Data Exchange (ETDEWEB)

    Fairbanks, Carly R.

    2011-08-26

    Diatoms are a distinctive group of microalgae with the unique ability to produce a highly-ordered biosilica matrix, known as the frustule. Diatoms hold significant potential in the biotechnology field as a silica scaffold for embedding proteins. In this study, we analyzed the funtionalization of biosilica with a receptor complex through genetic modification of the diatom, Thalassiosira pseudonana. Through the use of Foerster Resonance Energy Transfer (FRET), the receptor was shown to remain active in transformed frustules after the inner cellular contents were removed. In addition to protein functionality, growth conditions for T. pseudonana were optimized. Untransformed cultures receiving aeration grew more rapidly than stagnant untransformed cultures. Surprisingly, transformed cultures grew more quickly than untransformed cultures. This study demonstrates isolated diatom frustules provide an effective scaffold for embedded receptor complexes. Through this research, we provide the groundwork for the development of new biosensors for use in diagnostics and environmental remediation.

  5. Pliocene diatoms from the Bryce Canyon Area, Utah

    Digital Repository Service at National Institute of Oceanography (India)

    Setty, M.G.A.P.

    habitat. The fragmentary condition of these indicated agitation during sedimentation. The ratio between the planktonic and benthonic diatoms indicated near-shore deposition. The two extinct species (?), @iSurirella craticula@@ (= @iStictodesmis craticula...

  6. Resonant inelastic collisions of electrons with diatomic molecules

    International Nuclear Information System (INIS)

    Houfek, Karel

    2012-01-01

    In this contribution we give a review of applications of the nonlocal resonance theory which has been successfully used for treating the nuclear dynamics of low-energy electron collisions with diatomic molecules over several decades. We give examples and brief explanations of various structures observed in the cross sections of vibrational excitation and dissociative electron attachment to diatomic molecules such as threshold peaks, boomerang oscillations below the dissociative attachment threshold, or outer-well resonances.

  7. Resonant inelastic collisions of electrons with diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Houfek, Karel, E-mail: karel.houfek@gmail.com [Institute of Theoretical Physics, Faculty of Mathematics and Physics, Charles University, V Holesovickach 2, 180 00 Prague 8 (Czech Republic)

    2012-05-15

    In this contribution we give a review of applications of the nonlocal resonance theory which has been successfully used for treating the nuclear dynamics of low-energy electron collisions with diatomic molecules over several decades. We give examples and brief explanations of various structures observed in the cross sections of vibrational excitation and dissociative electron attachment to diatomic molecules such as threshold peaks, boomerang oscillations below the dissociative attachment threshold, or outer-well resonances.

  8. Epibiotic Diatoms Are Universally Present on All Sea Turtle Species

    OpenAIRE

    Robinson, Nathan J.; Majewska, Roksana; Lazo-Wasem, Eric A.; Nel, Ronel; Paladino, Frank V.; Rojas, Lourdes; Zardus, John D.; Pinou, Theodora

    2016-01-01

    The macro-epibiotic communities of sea turtles have been subject to growing interest in recent years, yet their micro-epibiotic counterparts are almost entirely unknown. Here, we provide the first evidence that diatoms are epibionts for all seven extant species of sea turtle. Using Scanning Electron Microscopy, we inspected superficial carapace or skin samples from a single representative of each turtle species. We distinguished 18 diatom taxa from these seven individuals, with each sea turtl...

  9. Radiational and energetic characteristics of diatomic molecules (data base)

    International Nuclear Information System (INIS)

    Kuznetsova, L.A.; Pazyuk, E.A.; Stolyarov, A.V.

    1993-01-01

    Data base on radiational and energetic characteristics of diatomic molecules was created. The base consists of two parts: reference system and recommended data system. The reference system contains the information about studies of radiational and energetic parameters of more than 1500 electronic states and 1700 electron transfers for ∼ 350 diatomic molecules and their ions. The base bibliography includes ∼ 3000 publications. 11 refs., 1 figs

  10. The adsorption kinetics of metal ions onto different microalgae and siliceous earth.

    Science.gov (United States)

    Schmitt, D; Müller, A; Csögör, Z; Frimmel, F H; Posten, C

    2001-03-01

    In the present work the adsorption kinetics of the six metal ions aluminum, zinc, mercury, lead, copper, and cadmium onto living microalgae were measured. The freshwater green microalga Scenedesmus subspicatus, the brackish water diatom Cyclotella cryptica, the seawater diatom Phaeodactylum tricornutum, and the seawater red alga Porphyridium purpureum were the subject of investigation. In most cases the adsorption rate of the metals could be well described by using the equation of the Langmuir adsorption rate expression. Inverse parameter estimation allowed the determination of the rate constants of the adsorption process and the maximum metal content of the algae. The highest values for the rate constant were obtained for Porphyridium purpureum followed by Phaeodactylum tricornutum. High values for the maximum content were obtained for Cyclotella cryptica and Scenedesmus subspicatus. The maximum rate constant was 24.21 h-1 for the adsorption of Hg to Porphyridium purpureum whereas the maximum metal content (0.243 g g-1) was obtained for Zn on Cyclotella cryptica. A comparison of these values with those obtained for the mineral siliceous earth exhibiting low maximum content and high adsorption rates reveals that the mechanism of adsorption onto the algae is a mixture of adsorption and accumulation.

  11. THE INFLUENCE OF SUBMERGED MACROPHYTES ON SEDIMENTARY DIATOM ASSEMBLAGES(1).

    Science.gov (United States)

    Vermaire, Jesse C; Prairie, Yves T; Gregory-Eaves, Irene

    2011-12-01

    Submerged macrophytes are a central component of lake ecosystems; however, little is known regarding their long-term response to environmental change. We have examined the potential of diatoms as indicators of past macrophyte biomass. We first sampled periphyton to determine whether habitat was a predictor of diatom assemblage. We then sampled 41 lakes in Quebec, Canada, to evaluate whether whole-lake submerged macrophyte biomass (BiomEpiV) influenced surface sediment diatom assemblages. A multivariate regression tree (MRT) was used to construct a semiquantitative model to reconstruct past macrophyte biomass. We determined that periphytic diatom assemblages on macrophytes were significantly different from those on wood and rocks (ANOSIM R = 0.63, P macrophyte, nutrient-limited lakes (BiomEpiV ≥525 μg · L(-1) ; total phosphorus [TP] macrophyte, nutrient-limited lakes (BiomEpiV macrophytes have a significant influence on diatom community structure and that sedimentary diatom assemblages can be used to infer past macrophyte abundance. © 2011 Phycological Society of America.

  12. Current trends to comprehend lipid metabolism in diatoms.

    Science.gov (United States)

    Zulu, Nodumo Nokulunga; Zienkiewicz, Krzysztof; Vollheyde, Katharina; Feussner, Ivo

    2018-04-01

    Diatoms are the most dominant phytoplankton species in oceans and they continue to receive a great deal of attention because of their significant contributions in ecosystems and the environment. Due to triacylglycerol (TAG) profiles that are abundant in medium-chain fatty acids, diatoms have emerged to be better feed stocks for biofuel production, in comparison to the commonly studied green microalgal species (chlorophytes). Importantly, diatoms are also known for their high levels of the essential ω3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and are considered to be a promising alternative source of these components. The two most commonly exploited diatoms include Thalassiosira pseudonana and Phaeodactylum tricornutum. Although obvious similarities between diatoms and chlorophytes exist, there are some substantial differences in their lipid metabolism. This review provides an overview on lipid metabolism in diatoms, with P. tricornutum as the most explored model. Special emphasis is placed on the synthesis and incorporation of very long chain ω3 fatty acids into lipids. Furthermore, current approaches including genetic engineering and biotechnological methods aimed at improving and maximizing lipid production in P. tricornutum are also discussed. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

  13. Oligocene age of the classic Belén fruit and seed assemblage of north coastal Peru based on diatom biostratigraphy

    Science.gov (United States)

    Manchester, Steven R.; Herrera, Fabiany; Fourtainer, Elisabeth; Barron, John A.; Martinez, Jean-Noël

    2012-01-01

    The Belén flora, in north coastal Peru, is the most diverse fruit and seed assemblage known from the Paleogene of South America. Almost no original paleobotanical work has been done on this assemblage since the pioneering treatments published by E.W. Berry, in the 1920’s and the precise age has not been settled. Nevertheless, the flora has been regarded as an important focal point in understanding the vegetational, orogenic and climatic history of northern South America, and in recent literature has been assumed to be early Eocene. In order to tighten the age assignment, which has varied from early Eocene to early Oligocene in the opinions of different authors, we revisited the Belén site, measured the stratigraphic section, and processed the fruit and seed-containing sediment for age-diagnostic microfossils. Although pollen and foraminifera were not recovered, the sediment is rich in diatoms. The diatom assemblage includes Lisitzinia ornata and Rocella vigilans among others, indicating a latest early Oligocene age (~30-28.5 Ma) for these deeper marine sediments that we infer to have been subsequently reworked into the Belén environment . This association leads us to consider the Belén flora, to be late Oligocene in age as is also consistent with its placement in the Mancora Formation. We also reevaluate the botanical identifications, based on the original museum specimens supplemented by more recently collected specimens. The Belén flora provides a window to extinct forests in South America before the rising of the Andes in western Peru.

  14. Responses of diatom communities to hydrological processes during rainfall events

    Science.gov (United States)

    Wu, Naicheng; Faber, Claas; Ulrich, Uta; Fohrer, Nicola

    2015-04-01

    The importance of diatoms as a tracer of hydrological processes has been recently recognized (Pfister et al. 2009, Pfister et al. 2011, Tauro et al. 2013). However, diatom variations in a short-term scale (e.g., sub-daily) during rainfall events have not been well documented yet. In this study, rainfall event-based diatom samples were taken at the outlet of the Kielstau catchment (50 km2), a lowland catchment in northern Germany. A total of nine rainfall events were caught from May 2013 to April 2014. Non-metric multidimensional scaling (NMDS) revealed that diatom communities of different events were well separated along NMDS axis I and II, indicating a remarkable temporal variation. By correlating water level (a proxy of discharge) and different diatom indices, close relationships were found. For example, species richness, biovolume (μm3), Shannon diversity and moisture index01 (%, classified according to van Dam et al. 1994) were positively related with water level at the beginning phase of the rainfall (i.e. increasing limb of discharge peak). However, in contrast, during the recession limb of the discharge peak, diatom indices showed distinct responses to water level declines in different rainfall events. These preliminary results indicate that diatom indices are highly related to hydrological processes. The next steps will include finding out the possible mechanisms of the above phenomena, and exploring the contributions of abiotic variables (e.g., hydrologic indices, nutrients) to diatom community patterns. Based on this and ongoing studies (Wu et al. unpublished data), we will incorporate diatom data into End Member Mixing Analysis (EMMA) and select the tracer set that is best suited for separation of different runoff components in our study catchment. Keywords: Diatoms, Rainfall event, Non-metric multidimensional scaling, Hydrological process, Indices References: Pfister L, McDonnell JJ, Wrede S, Hlúbiková D, Matgen P, Fenicia F, Ector L, Hoffmann L

  15. Physical ageing of silicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Nemilov, S.V. [S. I. Vavilov State Optical Inst., St. Petersburg (Russian Federation)

    2003-02-01

    The presented review has been devoted to the problem of volume-determined properties relaxation of silicate glasses at room temperature. It is shown that the experimental data are described by the simple Debye exponential law or by a superposition of two exponents. Their parameters are calculated and systematized. A molecular-kinetic model is proposed for these ageing processes. It proceeds from the possibility of volume relaxation due to the cooperative β-relaxation mechanism with no change in the system's topology. The characteristic ageing times can be calculated according to equations obtained based on the viscosity data in the glass transition range. The precision of the calculations is about {+-} 15% at the time variations from a few weeks up to about 15 years. The system of calculated parameters is proposed which characterizes the completeness of ageing and its rate at any glass age. Optical and thermometric glasses have been ranked by their tendency to ageing. The scheme of future investigations predetermined by practice is defined. (orig.)

  16. Magnetic properties of sheet silicates

    International Nuclear Information System (INIS)

    Ballet, O.; Coey, J.M.D.

    1982-01-01

    Susceptibility, magnetisation and Moessbauer measurements are reported for a representative selection of 2:1 layer phyllosilicates. Eight samples from the mica, vermiculite and smectite groups include examples diluted in iron which are paramagnetic at all temperatures, as well as iron-rich silicates which order magnetically below 10 K. Anisotropic susceptibility of crystals of muscovite, biotite and vermiculite is quantitatively explained with a model where the Fe 2+ ions lie in sites of effective trigonal symmetry, the trigonal axis lying normal to the sheets. The ferrous ground state is an orbital singlet. Ferric iron gives an isotropic contribution to the susceptibility. Fe 2+ -Fe 2+ exchange interactions are ferromagnetic with Gapprox. equal to2 K, whereas Fe 3+ -Fe 3+ coupling is antiferromagnetic in the purely ferric minerals. A positive paramagnetic Curie temperature for glauconite may be attributable to Fe 2+ → Fe 3+ charge transfer. Magnetic order was found to set in inhomogeneously for glauconite at 1-7 K. One biotite sample showed an antiferromagnetic transition at Tsub(N) = 7 K marked by a well-defined susceptibility maximum. Its magnetic structure, consisting of ferromagnetic sheets with moments in their planes coupled antiferromagnetically by other, weak interactions, resembles that found earlier for the 1:1 mineral greenalite. (orig.)

  17. Adsorption of aqueous silicate on hematite

    International Nuclear Information System (INIS)

    Taylor, P.; Ticknor, K.V.

    1997-08-01

    During radioisotope sorption studies, adsorption of silicate from synthetic groundwaters by synthetic hematite was observed. To further investigate this observation, the adsorption of silicate onto hematite (α-Fe 2 O 3 ) powder from a neutral, aqueous NaC1 solution (0.1 mol/dm 3 ), containing 2.56 x 10 -4 mol/dm 3 of Si added as Na 2 SiO 3 ·9H 2 O, was measured at ∼21 deg C. Equilibrium adsorption of silicate amounted to ∼1.93 μmol/m 2 (one Si(O,OH) 4 moiety per 86 A 2 ). It is important to take this adsorption into account when evaluating the ability of iron oxides to adsorb other species, especially anions, from groundwaters. Silicate adsorption is known to diminish the ability of iron oxides to adsorb other anions. (author)

  18. Thermodynamics and Kinetics of Silicate Vaporization

    Science.gov (United States)

    Jacobson, Nathan S.; Costa, Gustavo C. C.

    2015-01-01

    Silicates are a common class of materials that are often exposed to high temperatures. The behavior of these materials needs to be understood for applications as high temperature coatings in material science as well as the constituents of lava for geological considerations. The vaporization behavior of these materials is an important aspect of their high temperature behavior and it also provides fundamental thermodynamic data. The application of Knudsen effusion mass spectrometry (KEMS) to silicates is discussed. There are several special considerations for silicates. The first is selection of an appropriate cell material, which is either nearly inert or has well-understood interactions with the silicate. The second consideration is proper measurement of the low vapor pressures. This can be circumvented by using a reducing agent to boost the vapor pressure without changing the solid composition or by working at very high temperatures. The third consideration deals with kinetic barriers to vaporization. The measurement of these barriers, as encompassed in a vaporization coefficient, is discussed. Current measured data of rare earth silicates for high temperature coating applications are discussed. In addition, data on magnesium-iron-silicates (olivine) are presented and discussed.

  19. Rotation harmonics for a numerical diatomic potential

    International Nuclear Information System (INIS)

    Kobeissi, H.; Korek, M.

    1983-01-01

    The problem of the determination of the rotation harmonics phi 1 , phi 2 , ... for the case of a numerical diatomic potential is considered. These harmonics defined in a recent work by psisub(vJ) = psisub(vO) + lambda 2 phi 2 + ... (where psisub(vJ) is the wave function of the vibration level v and the rotation level J, and lambda = J(J+1)) are studied for the case of the Dunham potential and for a numerical potential defined by the coordinates of its turning points with polynomial interpolations and extrapolations. It is proved that the analytical expressions of the harmonics phi 1 , phi 2 , ... reduce to polynomials where the coefficients are simply related to those of the potential in the case of the Dunham potential, and to the coordinates of the turning points in the case of the numerical potential. The numerical application is simple. The examples presented show that the vibration-rotation wave function psisub(vJ) calculated by using two harmonics only is ''exact'' up to eight significant figures

  20. Diatomic molecule vibrational potentials: Accuracy of representations

    International Nuclear Information System (INIS)

    Engelke, R.

    1978-01-01

    A method is presented for increasing the radius of convergence of certain representations of diatomic molecule vibrational potentials. The method relies on using knowledge of the analytic structure of such potentials to the maximum when attempting to approximate them. The known singular point (due to the centrifugal and/or Coulomb potentials) at zero internuclear separation should be included in its exact form in an approximate representation. The efficacy of this idea is tested [using Peek's ''exact'' numerical Born-Oppenheimer potential for the (1ssigma/sub g/) 2 Σ + /sub g/ state of H + 2 as a test problem] when the representational form is the series of (1) Dunham, (2) Simons, Parr, and Finlan, (3) Thakkar, and (4) Ogilvie-Tipping, and also (5) when the form is a [2, 2] or a [3, 3] Pade approximant. Significant improvements in accuracy are obtained in some of these cases, particularly on the inner wall of the potential. A comparison of the effectiveness of the five methods is made both with and without the origin behavior being included exactly. This is useful in itself as no comprehensive accuracy comparison of the standard representations seems to have appeared in the literature. The Ogilvie-Tipping series, corrected at the origin for singular behavior, is the best representation presently available for states analogous to the (1ssigma/sub g/) 2 Σ + /sub g/ state of H + 2

  1. Wear and chemistry of zirconium-silicate, aluminium-silicate and zirconium-aluminium-silicate glasses in alkaline medium

    International Nuclear Information System (INIS)

    Rouse, C.G.; Lemos Guenaga, C.M. de

    1984-01-01

    A study of the chemical durability, in alkaline solutions, of zirconium silicate, aluminium silicate, zirconium/aluminium silicate glasses as a function of glass composition is carried out. The glasses were tested using standard DIN-52322 method, where the glass samples are prepared in small polished pieces and attacked for 3 hours in a 800 ml solution of 1N (NaOH + NA 2 CO 3 ) at 97 0 C. The results show that the presence of ZrO 2 in the glass composition increases its chemical durability to alkaline attack. Glasses of the aluminium/zirconium silicate series were melted with and without TiO 2 . It was shown experimentally that for this series of glasses, the presence of both TiO 2 and ZrO 2 gave better chemical durability results. However, the best overall results were obtained from the simpler zirconium silicate glasses, where it was possible to make glasses with higher values of ZrO 2 . (Author) [pt

  2. The kinetic fragility of natural silicate melts

    International Nuclear Information System (INIS)

    Giordano, Daniele; Dingwell, Donald B

    2003-01-01

    Newtonian viscosities of 19 multicomponent natural and synthetic silicate liquids, with variable contents of SiO 2 (41-79 wt%), Al 2 O 3 (10-19 wt%), TiO 2 (0-3 wt%), FeO tot (0-11 wt%); alkali oxides (5-17 wt%), alkaline-earth oxides (0-35 wt%), and minor oxides, obtained at ambient pressure using the high-temperature concentric cylinder, the low-temperature micropenetration, and the parallel plates techniques, have been analysed. For each silicate liquid, regression of the experimentally determined viscosities using the well known Vogel-Fulcher-Tammann (VFT) equation allowed the viscosity of all these silicates to be accurately described. The results of these fits, which provide the basis for the subsequent analysis here, permit qualitative and quantitative correlations to be made between the VFT adjustable parameters (A VFT , B VFT , and T 0 ). The values of B VFT and T 0 , calibrated via the VFT equation, are highly correlated. Kinetic fragility appears to be correlated with the number of non-bridging oxygens per tetrahedrally coordinated cation (NBO/T). This is taken to infer that melt polymerization controls melt fragility in liquid silicates. Thus NBO/T might form an useful ingredient of a structure-based model of non-Arrhenian viscosity in multicomponent silicate melts

  3. Species interactions within a fouling diatom community: Roles of nutrients, initial inoculum and competitive strategies

    Digital Repository Service at National Institute of Oceanography (India)

    Mitbavkar, S.; Anil, A

    Diatoms constitute an important component of the fouling community. Although a lot of work has dealt with the fouling diatom community structure, work on the species interactions within the community is still meager. In this regard, a study...

  4. Genotoxicity of cadmium in marine diatom Chaetoceros tenuissimus using the alkaline Comet assay

    Digital Repository Service at National Institute of Oceanography (India)

    Desai, S.R.; Verlecar, X.N.; Nagarajappa; Goswami, U.

    of Cd increased growth of the diatom decreased. Alkaline single-cell gel electrophoresis (Comet assay) method, which is highly sensitive in detection of DNA damage in eukaryotic cells, was used to observe genomic changes in marine diatom cells. DNA...

  5. Diatom community dynamics in a tropical, monsoon-influenced environment: West coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    DeCosta, P.M.; Anil, A.C.

    Diatom communities are influenced by environmental perturbations, such as the monsoon system that impact the niche opportunities of species. To discern the influence of the monsoon system on diatom community structure, we sampled during two...

  6. Fouling diatom community with reference to substratum variability in tropical marine environment

    Digital Repository Service at National Institute of Oceanography (India)

    Mitbavkar, S.; Desai, D.V.; Khandeparker, L.; Anil, A.C.; Wagh, A.B.

    form encountered. The paper deals with the qualitative and quantitative aspects of diatom colonization, their community structure, and correlation between the prevailing diatom population in the environment and that in the fouling community...

  7. Growth inhibition of periphytic diatoms by methanol extracts of sponges and holothurians

    Digital Repository Service at National Institute of Oceanography (India)

    Mokashe, S.S.; Garg, A; Anil, A; Wagh, A

    Crude methanol extracts of a holothurian Holothuria leucospilota, and two sponges Craniella sp. and Ircinia ramosa were tested for their inhibitory effects on the growth of two marine diatoms, Navicula subinflata and N. crucicula, by diatom plating...

  8. The application and testing of diatom-based indices of stream water ...

    African Journals Online (AJOL)

    The application and testing of diatom-based indices of stream water quality in Chinhoyi Town, Zimbabwe. ... PROMOTING ACCESS TO AFRICAN RESEARCH ... test the applicability of foreign diatom-based water quality assessment indices to ...

  9. Epipsammic diatoms in streams influenced by urban pollution, São Carlos, SP, Brazil

    Directory of Open Access Journals (Sweden)

    T. Bere

    Full Text Available Epipsammic diatoms have important implications for ecosystem processes in lotic environments. Most of the studies on benthic diatoms concentrate on epilithic diatoms and very little is known about epipsammic diatoms. The objective of this study was to assess epipsammic diatom communities in streams in relation to environmental conditions. Epipsammic diatoms and water quality sampling was done at 7 sites during summer base flow period (2008. Forward stepwise multiple regression and canonical correspondence analysis (CCA were used to determine environmental gradients along which species vary with physical and chemical variables. A total of 112 diatom species distributed among 44 genera were recorded. Altitude and the process of eutrophication played a significant role in structuring diatom communities in the study region.

  10. Fragmentation patterns in the diatom genus Rouxia and their potential for identifying latent depositional hiatuses in the early Pliocene diatomite of the ANDRILL AND-1B core

    Science.gov (United States)

    Konfirst, M. A.; Scherer, R. P.; Winter, D.; Sjunneskog, C.; Warnock, J.; Kuhn, G.; Niessen, F.; Helling, D.; Magens, D.

    2009-04-01

    Diatom genera have traditionally been split into two primary groupings based upon the symmetry of the siliceous frustule. Diatoms symmetric about a point are classified as centrics, while those symmetric about a line are classified as pennates. This fundamental difference in shape has consequences for preservation in ice proximal settings, where an overriding ice sheet can create shearing in the upper meters of the sediment column. This leads to preferential breakage in pennate forms, and results in a higher ratio of undamaged centric to pennate frustules (Scherer et al., 2004). Similarly, an ice sheet grounded over highly porous diatomite results in significant diatom fragmentation resulting from normal load compaction. The diatom genus Rouxia is a pennate form with a relatively wide raphe, making it particularly susceptible to breakage during ice advance and retreat, and offering the opportunity to evaluate ice advance stages in sedimentary units where glacial erosion may have removed upper depositional units. In the ANDRILL AND-1B core, a long interval of nearly pure diatomite was recovered from 382.98-459.24 mbsf. Construction of an age model during this interval has relied primarily on age ranges provided by presence or absence of key diatom species. However, questions still remain as to the continuity of deposition. In this study, samples were collected at an average of 50-cm spacing for the length of the long diatom unit as well as for 20 meters of the silica-rich diamictite unit directly overlaying the diatomite. Fragments of specimens from the genus Rouxia were counted and classified into categories based on the size of the fragment in relation to total frustule length. These data were then used to develop a quantitative index, which was examined for changes in fragmentation through time. Preliminary data are presented that indicate increased fragmentation at the top of the section under study, which we interpret to indicate evidence for increased glacial

  11. Computation of diatomic molecular spectra for selected transitions of aluminum monoxide, cyanide, diatomic carbon, and titanium monoxide

    Energy Technology Data Exchange (ETDEWEB)

    Parigger, Christian G., E-mail: cparigge@tennessee.edu [The University of Tennessee/University of Tennessee Space Institute, Center for Laser Applications, 411 B.H. Goethert Parkway, Tullahoma, TN 37388-9700 (United States); Woods, Alexander C.; Surmick, David M.; Gautam, Ghaneshwar; Witte, Michael J. [The University of Tennessee/University of Tennessee Space Institute, Center for Laser Applications, 411 B.H. Goethert Parkway, Tullahoma, TN 37388-9700 (United States); Hornkohl, James O. [Hornkohl Consulting, Tullahoma, TN 37388 (United States)

    2015-05-01

    Laser ablation studies with laser-induced breakdown spectroscopy (LIBS) typically emphasize atomic species yet fingerprints from molecular species can occur subsequently or concurrently. In this work, selected molecular transitions of aluminum monixide (AlO), diatomic carbon (C{sub 2}), cyanide (CN), and titanium monoxide (TiO) are accurately computed. Line strength tables are used to describe the radiative transitions of diatomic molecules primarily in the visible, optical region. Details are elaborated of the computational procedure that allows one to utilize diatomic spectra as a predictive and as a diagnostic tool. In order to create a computed spectrum, the procedure requires information regarding the temperature of the diatomic transitions along with other input such as the spectral resolution. When combined with a fitting algorithm to optimize such parameters, this procedure is used to infer information from an experimentally obtained spectrum. Furthermore, the programs and data files are provided for LIBS investigations that also reveal AlO, C{sub 2}, CN, and TiO diatomic spectra. - Highlights: • We present a program for fitting of molecular spectra. • This includes data base for AlO, C{sub 2}, CN, and TiO. • We discuss the details of the program including fitting. • We show computed examples and reference current work.

  12. Circular random motion in diatom gliding under isotropic conditions

    International Nuclear Information System (INIS)

    Gutiérrez-Medina, Braulio; Maldonado, Ana Iris Peña; Guerra, Andrés Jiménez; Rubio, Yadiralia Covarrubias; Meza, Jessica Viridiana García

    2014-01-01

    How cells migrate has been investigated primarily for the case of trajectories composed by joined straight segments. In contrast, little is known when cellular motion follows intrinsically curved paths. Here, we use time-lapse optical microscopy and automated trajectory tracking to investigate how individual cells of the diatom Nitzschia communis glide across surfaces under isotropic environmental conditions. We find a distinct kind of random motion, where trajectories are formed by circular arcs traveled at constant speed, alternated with random stoppages, direction reversals and changes in the orientation of the arcs. Analysis of experimental and computer-simulated trajectories show that the circular random motion of diatom gliding is not optimized for long-distance travel but rather for recurrent coverage of limited surface area. These results suggest that one main biological role for this type of diatom motility is to efficiently build the foundation of algal biofilms. (paper)

  13. Bioactive glass 45S5 from diatom biosilica

    Directory of Open Access Journals (Sweden)

    Luqman A. Adams

    2017-12-01

    Full Text Available A major draw-back to large scale production of bioactive glasses is the high cost of the standard silica precursor, usually tetraethyl orthosilicate (TEOS. The current study describes a novel sol–gel preparation of 45S5 bioactive glass using diatom biosilica from cultured cells of the diatom, Aulacoseira granulata as substitute to TEOS. The glass formed was characterized using mechanical tester, scanning electron microscopy (SEM, energy dispersive X-ray analysis (EDX, X-ray diffraction (XRD and Fourier transform infrared (FTIR spectroscopy. Results showed that the glass possessed a compressive strength of 3.75 ± 0.18 and formed carbonated hydroxyapatite (HCA within 7 days in simulated body fluid (SBF, attributable to good surface chemistry. The performance of the glass was compared with that of those formed using TEOS. Diatom biosilica could be a potential economically friendly starting material for large scale fabrication of bioactive glasses.

  14. A new cell primo-culture method for freshwater benthic diatom communities

    OpenAIRE

    Debenest, Timothée; Silvestre, Jérôme; Coste, Michel; Delmas, François; Pinelli, Eric

    2009-01-01

    A new cell primo-culture method was developed for the benthic diatom community isolated from biofilm sampled in rivers. The approach comprised three steps: (1) scraping biofilm from river pebbles, (2) diatom isolation from biofilm, and (3) diatom community culture. With a view to designing a method able to stimulate the growth of diatoms, to limit the development of other microorganisms, and to maintain in culture a community similar to the original natural one, different factors were test...

  15. Silicic magma generation at Askja volcano, Iceland

    Science.gov (United States)

    Sigmarsson, O.

    2009-04-01

    Rate of magma differentiation is an important parameter for hazard assessment at active volcanoes. However, estimates of these rates depend on proper understanding of the underlying magmatic processes and magma generation. Differences in isotope ratios of O, Th and B between silicic and in contemporaneous basaltic magmas have been used to emphasize their origin by partial melting of hydrothermally altered metabasaltic crust in the rift-zones favoured by a strong geothermal gradient. An alternative model for the origin of silicic magmas in the Iceland has been proposed based on U-series results. Young mantle-derived mafic protolith is thought to be metasomatized and partially melted to form the silicic end-member. However, this model underestimates the compositional variations of the hydrothermally-altered basaltic crust. New data on U-Th disequilibria and O-isotopes in basalts and dacites from Askja volcano reveal a strong correlation between (230Th/232Th) and delta 18O. The 1875 AD dacite has the lowest Th- and O isotope ratios (0.94 and -0.24 per mille, respectively) whereas tephra of evolved basaltic composition, erupted 2 months earlier, has significantly higher values (1.03 and 2.8 per mille, respectively). Highest values are observed in the most recent basalts (erupted in 1920 and 1961) inside the Askja caldera complex and out on the associated fissure swarm (Sveinagja basalt). This correlation also holds for older magma such as an early Holocene dacites, which eruption may have been provoked by rapid glacier thinning. Silicic magmas at Askja volcano thus bear geochemical signatures that are best explained by partial melting of extensively hydrothermally altered crust and that the silicic magma source has remained constant during the Holocene at least. Once these silicic magmas are formed they appear to erupt rapidly rather than mixing and mingling with the incoming basalt heat-source that explains lack of icelandites and the bi-modal volcanism at Askja

  16. Twentieth-century warming revives the world's northernmost lake

    DEFF Research Database (Denmark)

    Perren, Bianca B.; Wolfe, Alexander P.; Cooke, Colin A.

    2012-01-01

    lake to explore this question. Microfossils indicate that siliceous diatoms and chrysophytes were abundant initially, but disappeared 2400 yr ago in concert with Neoglacial cooling. Microfossils reappear in 20th-century sediments and reach unprecedented concentrations in sediments deposited after ca. A.......D. 1980, tracking increasing summer temperatures in the absence of evidence for atmospheric nutrient subsidies. These results indicate that current warming in northern Greenland is unprecedented in the context of the past 2400 yr, and that climate change alone is responsible for the marked biological...

  17. Effect of ageing on survival of benthic diatom propagules

    Digital Repository Service at National Institute of Oceanography (India)

    Anil, A.C.; Mitbavkar, S.; De; Hegde, S.; De; Meher, S.S.; Banerjee, D.

    unfavorable for vegetative growth, many diatoms form resting stages to survive cell degradation or death (Anderson, 1975; Malone, 1980; Hargraves and French, 1983; Fryxell, 1990). Various external factors like availability of nutrients (N, P, Fe, Si.... 128, 497-508. 15 Lewis, J., Harris, A.S.D., Jones, K.J., Edmonds, R.L., 1999. Long-term survival of marine planktonic diatoms and dinoflagellates in stored sediment samples. J. Plank. Res. 21, 343- 354. Malone, T.C., 1980. Algal size. In...

  18. Diatom Assemblage in the Lake of Gaber Oun, Southern Libya

    Directory of Open Access Journals (Sweden)

    Abdelkader Elzen

    2012-07-01

    Full Text Available The lake of Gaber Oun in the southern district of Libya was studied to assess the diatom community composition in the littoral zone. Planktic and attached diatoms were listed and information on the constituent species made known (images are shown. Some criteria of the water characteristics are also given such as the pH, which is an average of 8.3, electrical conductivity which accounted for 1.4 µSim/cm1- and total dissolved salts (TDS of 189.0 mg/L1-.

  19. Biological monitoring of lotic ecosystems: the role of diatoms

    Directory of Open Access Journals (Sweden)

    T. Bere

    Full Text Available Increasing anthropogenic influence on lotic environments as a result of civilisation has captured public interest because of the consequent problems associated with deterioration of water quality. Various biological monitoring methods that provide a direct measure of ecological integrity by using the response of biota to environmental changes have been developed to monitor the ecological status of lotic environments. Diatoms have been used extensively in this regard and this review attempts to summarise the basic concepts associated with biological monitoring using benthic diatoms. Where possible, examples from work carried out in Brazil are used.

  20. Biological monitoring of lotic ecosystems: the role of diatoms.

    Science.gov (United States)

    Bere, T; Tundisi, J G

    2010-08-01

    Increasing anthropogenic influence on lotic environments as a result of civilisation has captured public interest because of the consequent problems associated with deterioration of water quality. Various biological monitoring methods that provide a direct measure of ecological integrity by using the response of biota to environmental changes have been developed to monitor the ecological status of lotic environments. Diatoms have been used extensively in this regard and this review attempts to summarise the basic concepts associated with biological monitoring using benthic diatoms. Where possible, examples from work carried out in Brazil are used.

  1. The UV filtering potential of drop-casted layers of frustules of three diatom species

    DEFF Research Database (Denmark)

    Su, Yanyan; Lenau, Torben Anker; Gundersen, Emil

    2018-01-01

    Diatoms are in focus as biological materials for a range of photonic applications. Many of theseapplications would require embedding a multitude of diatoms in a matrix (e.g. paint, crème or lacquer); however, most studies on the photonic and spectral properties of diatoms frustules (silica walls)...

  2. Fluxes of diatoms in the Dona Paula Bay, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Garg, A.; Bhaskar, P.V.

    of POC and diatom carbon was 251 and 0.39 mg C m sup(-2) day sup(-1), respectively. The diatom carbon accounted for 0.15% of the POC flux. Mass flux of diatoms showed significant negative correlation with the concentration of nitrate and phosphate...

  3. Nanostructure of Calcium Silicate Hydrates in Cements

    KAUST Repository

    Skinner, L. B.; Chae, S. R.; Benmore, C. J.; Wenk, H. R.; Monteiro, P. J. M.

    2010-01-01

    Calcium silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated tricalcium silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure. © 2010 The American Physical Society.

  4. Nanostructure of Calcium Silicate Hydrates in Cements

    KAUST Repository

    Skinner, L. B.

    2010-05-11

    Calcium silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated tricalcium silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure. © 2010 The American Physical Society.

  5. Diatom-induced silicon isotopic fractionation in Antarctic sea ice

    Science.gov (United States)

    Francois, F.; Damien, C.; Jean-Louis, T.; Anthony, W.; Luc, A.

    2006-12-01

    We measured silicon-isotopic composition of dissolved silicon and biogenic silica collected by sequential melting from spring 2003 Antarctic pack ice (Australian sector). Sea ice is a key ecosystem in the Southern Ocean and its melting in spring has been often thought to have a seeding effect for the surface waters, triggering blooms in the mixed layer. This work is the first investigation of the silicon isotopes' proxy in sea ice and allows to estimate the activity of sea-ice diatoms in the different brine structures and the influence of sea- ice diatoms on the spring ice edge blooms. The relative use of the dissolved silicon pool by sea-ice diatoms is usually assessed by calculating nutrient:salinity ratios in the brines. However such an approach is biased by difficulties in evaluating the initial nutrient concentrations in the different brines structures, and by the impossibility to account for late sporadic nutrient replenishments. The silicon-isotopic composition of biogenic silica is a convenient alternative since it integrates an average Si utilization on all generations of diatoms. Measurements were performed on a MC-ICP-MS, in dry plasma mode using external Mg doping. Results are expressed as delta29Si relative to the NBS28 standard. From three sea ice cores with contrasted physico-chemical characteristics, we report significant isotopic fractionations linked to the diatoms activity, with distinct silicon biogeochemical dynamics between different brine structure. The diatoms in snow ice and in brine pockets of frazil or congelation ice have the most positive silicon-isotopic composition (+0.53 to +0.86 p.mil), indicating that they grow in a closed system and use a significant part of the small dissolved silicon pool. In the brine channels and skeletal layer, diatoms display a relatively less positive Si-isotopic composition (+0.41 to +0.70 p.mil), although it is still heavier compared to equilibrium fractionation (+0.38 p.mil). This suggests that they have

  6. Combustion synthesis and photoluminescence study of silicate ...

    Indian Academy of Sciences (India)

    sorbable and durable materials for orthopaedic and dental implants, that are capable of bearing high stress ... Other studies showed that these silicate ceramics also possess good in vivo bioactivity (Hench 1998; ... ceramic powders without the intermediate decomposition and/or calcining steps has attracted a good deal of ...

  7. Synthesis of non-siliceous mesoporous oxides.

    Science.gov (United States)

    Gu, Dong; Schüth, Ferdi

    2014-01-07

    Mesoporous non-siliceous oxides have attracted great interest due to their unique properties and potential applications. Since the discovery of mesoporous silicates in 1990s, organic-inorganic assembly processes by using surfactants or block copolymers as soft templates have been considered as a feasible path for creating mesopores in metal oxides. However, the harsh sol-gel conditions and low thermal stabilities have limited the expansion of this method to various metal oxide species. Nanocasting, using ordered mesoporous silica or carbon as a hard template, has provided possibilities for preparing novel mesoporous materials with new structures, compositions and high thermal stabilities. This review concerns the synthesis, composition, and parameter control of mesoporous non-siliceous oxides. Four synthesis routes, i.e. soft-templating (surfactants or block copolymers as templates), hard-templating (mesoporous silicas or carbons as sacrificial templates), colloidal crystal templating (3-D ordered colloidal particles as a template), and super lattice routes, are summarized in this review. Mesoporous metal oxides with different compositions have different properties. Non-siliceous mesoporous oxides are comprehensively described, including a discussion of constituting elements, synthesis, and structures. General aspects concerning pore size control, atomic scale crystallinity, and phase control are also reviewed.

  8. Dielectric properties of plasma sprayed silicates

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Sedláček, J.; Neufuss, Karel; Dubský, Jiří; Chráska, Pavel

    -, č. 31 (2005), s. 315-321 ISSN 0272-8842 R&D Projects: GA ČR(CZ) GA202/03/0708 Institutional research plan: CEZ:AV0Z20430508 Keywords : Optical microscopy * electrical properties * silicates * insulators * plasma spraying Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 0.702, year: 2005

  9. Suggestions for diatom-based monitoring in intermittent streams

    Directory of Open Access Journals (Sweden)

    Falasco Elisa

    2016-01-01

    Full Text Available Over the last decades, river lentification processes and droughts have been dramatically spreading worldwide, due to global and local drastic changes due to human activities. Under this scenario, the evaluation of physical disturbance caused by intermittency and droughts has become more and more relevant. In this research, we compare samples collected in Mediterranean streams following both traditional and experimental approaches with the aim of understanding if diatom indices calculated from a new sampling strategy could provide additional information for the physical disturbance assessment. Moreover, we also evaluated the response of functional metrics. Our results demonstrated that even though an enhanced sampling method better reflects hydrological disturbance than the traditional one, diatom indices do not detect it. Conversely, functional traits proved to be important metrics for the hydrological disturbance assessment. In particular, benthic diatom chlorophyll a showed significantly lower values in sections more subject to droughts. With respect to ecological guilds, the motile taxa proved to be linked to depositional areas, which resulted important microhabitats (MHs to be explored in rivers affected by lentification. Including different MHs in the sampling process improves the information we can obtain from the analysis of the diatom community and presents important implications in documenting species distribution and autecology.

  10. Evolutionary genomics of the cold-adapted diatom Fragilariopsis cylindrus

    KAUST Repository

    Mock, Thomas; Otillar, Robert P.; Strauss, Jan; McMullan, Mark; Paajanen, Pirita; Schmutz, Jeremy; Salamov, Asaf; Sanges, Remo; Toseland, Andrew; Ward, Ben J.; Allen, Andrew E.; Dupont, Christopher L.; Frickenhaus, Stephan; Maumus, Florian; Veluchamy, Alaguraj; Wu, Taoyang; Barry, Kerrie W.; Falciatore, Angela; Ferrante, Maria I.; Fortunato, Antonio E.; Glö ckner, Gernot; Gruber, Ansgar; Hipkin, Rachel; Janech, Michael G.; Kroth, Peter G.; Leese, Florian; Lindquist, Erika A.; Lyon, Barbara R.; Martin, Joel; Mayer, Christoph; Parker, Micaela; Quesneville, Hadi; Raymond, James A.; Uhlig, Christiane; Valas, Ruben E.; Valentin, Klaus U.; Worden, Alexandra Z.; Armbrust, E. Virginia; Clark, Matthew D.; Bowler, Chris; Green, Beverley R.; Moulton, Vincent; Oosterhout, Cock van; Grigoriev, Igor V.

    2017-01-01

    The Southern Ocean houses a diverse and productive community of organisms. Unicellular eukaryotic diatoms are the main primary producers in this environment, where photosynthesis is limited by low concentrations of dissolved iron and large seasonal fluctuations in light, temperature and the extent of sea ice. How diatoms have adapted to this extreme environment is largely unknown. Here we present insights into the genome evolution of a cold-adapted diatom from the Southern Ocean, Fragilariopsis cylindrus, based on a comparison with temperate diatoms. We find that approximately 24.7 per cent of the diploid F. cylindrus genome consists of genetic loci with alleles that are highly divergent (15.1 megabases of the total genome size of 61.1 megabases). These divergent alleles were differentially expressed across environmental conditions, including darkness, low iron, freezing, elevated temperature and increased CO2. Alleles with the largest ratio of non-synonymous to synonymous nucleotide substitutions also show the most pronounced condition-dependent expression, suggesting a correlation between diversifying selection and allelic differentiation. Divergent alleles may be involved in adaptation to environmental fluctuations in the Southern Ocean.

  11. Evolutionary genomics of the cold-adapted diatom Fragilariopsis cylindrus

    KAUST Repository

    Mock, Thomas

    2017-01-17

    The Southern Ocean houses a diverse and productive community of organisms. Unicellular eukaryotic diatoms are the main primary producers in this environment, where photosynthesis is limited by low concentrations of dissolved iron and large seasonal fluctuations in light, temperature and the extent of sea ice. How diatoms have adapted to this extreme environment is largely unknown. Here we present insights into the genome evolution of a cold-adapted diatom from the Southern Ocean, Fragilariopsis cylindrus, based on a comparison with temperate diatoms. We find that approximately 24.7 per cent of the diploid F. cylindrus genome consists of genetic loci with alleles that are highly divergent (15.1 megabases of the total genome size of 61.1 megabases). These divergent alleles were differentially expressed across environmental conditions, including darkness, low iron, freezing, elevated temperature and increased CO2. Alleles with the largest ratio of non-synonymous to synonymous nucleotide substitutions also show the most pronounced condition-dependent expression, suggesting a correlation between diversifying selection and allelic differentiation. Divergent alleles may be involved in adaptation to environmental fluctuations in the Southern Ocean.

  12. Functionalized diatom silica microparticles for removal of mercury ions

    International Nuclear Information System (INIS)

    Yu Yang; Addai-Mensah, Jonas; Losic, Dusan

    2012-01-01

    Diatom silica microparticles were chemically modified with self-assembled monolayers of 3-mercaptopropyl-trimethoxysilane (MPTMS), 3-aminopropyl-trimethoxysilane (APTES) and n-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPTMS), and their application for the adsorption of mercury ions (Hg(II)) is demonstrated. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy analyses revealed that the functional groups (–SH or –NH 2 ) were successfully grafted onto the diatom silica surface. The kinetics and efficiency of Hg(II) adsorption were markedly improved by the chemical functionalization of diatom microparticles. The relationship among the type of functional groups, pH and adsorption efficiency of mercury ions was established. The Hg(II) adsorption reached equilibrium within 60 min with maximum adsorption capacities of 185.2, 131.7 and 169.5 mg g -1 for particles functionalized with MPTMS, APTES and AEAPTMS, respectively. The adsorption behavior followed a pseudo-second-order reaction model and Langmuirian isotherm. These results show that mercapto- or amino-functionalized diatom microparticles are promising natural, cost-effective and environmentally benign adsorbents suitable for the removal of mercury ions from aqueous solutions.

  13. Effect of Industrial Effluent on the Growth of Marine Diatom ...

    African Journals Online (AJOL)

    The marine centric diatom,Chaetoceros simplex (Ostenfeld, 1901) was exposed to five different concentrations of industrial effluent for 96 hrs to investigate the effect on growth. The physico-chemical parameters viz. colour, odour, temperature, salinity, dissolved oxygen, turbidity, pH, alkalinity, hardness, ammonia, nitrite, ...

  14. Copepod reproduction is unaffected by diatom aldehydes or lipid composition

    DEFF Research Database (Denmark)

    Dutz, Jörg; Koski, Marja; Jonasdottir, Sigrun

    2008-01-01

    We investigated whether reduced reproductive success of copepods fed with diatoms was related to nutritional imbalances with regard to essential lipids or to the production of inhibitory aldehydes. In 10-d laboratory experiments, feeding, egg production, egg hatching success, and fecal pellet...

  15. Colonisation and community structure of benthic diatoms on artificial ...

    African Journals Online (AJOL)

    This was undertaken using tiles as artificial substrates so that we could study how the communities developed after the flood disturbance. The diatom community structure was assessed over a 28-day period following a flood event in October 2012. The Mann Whitney test indicated that there was a statistically significant ...

  16. Diatom distribution in the surficial sediments of Lake Fuxian, Yunnan ...

    African Journals Online (AJOL)

    ajl yemi

    2011-11-30

    Nov 30, 2011 ... (18.2%); there were some phosphorus post-mines which led to higher total phosphorus concentration than that in southern part. The most outstanding characteristic of diatom ... (212 km2 in surface area) is located in the central Yunnan. Province; it is a oligotrophic freshwater lake. It is the second deepest ...

  17. Mercury-induced genotoxicity in marine diatom (Chaetoceros tenuissimus)

    Digital Repository Service at National Institute of Oceanography (India)

    Sarker, S.; Desai, S.R.; Verlecar, X.N.; Sarker, M.S.; Sarkar, A.

    In this paper, we present an evaluation of genotoxic responses in marine diatom, Chaetoceros tenuissimus, isolated from Kandla Creek (lat 23.03° N, long 70.22° E), Gujarat, India, in terms of impairment of DNA integrity as a function...

  18. Enhancement of the reactive iron pool by marine diatoms

    NARCIS (Netherlands)

    Rijkenberg, Micha J. A.; Gerringa, Loes J. A.; Timmermans, Klaas R.; Fischer, Astrid C.; Kroon, Koos J.; Buma, Anita G. J.; Wolterbeek, Bert Th.; de Baar, Hein J. W.

    2008-01-01

    Short term (2 days) laboratory experiments were performed to study the change in irradiance induced production of Fe(II) in seawater in the presence of two open oceanic Southern Ocean diatom species, Thalassiosira sp. and Chaetoceros brevis. Three irradiance conditions were applied: 1) UVB+UVA+VIS,

  19. The Phaeodactylum genome reveals the evolutionary history of diatom genomes

    Czech Academy of Sciences Publication Activity Database

    Bowler, Ch.; Allen, A. E.; Badger, J. H.; Grimwood, J.; Jabbari, K.; Kuo, A.; Maheswari, U.; Martens, C.; Maumus, F.; Otillar, R. P.; Rayko, E.; Salamov, A.; Vandepoele, K.; Beszteri, B.; Gruber, A.; Heijde, M.; Katinka, M.; Mock, T.; Valentin, K.; Verret, F.; Berges, J. A.; Brownlee, C.; Cadoret, J.-P.; Chiovitti, A.; Choi, Ch. J.; Coesel, S.; De Martino, A.; Detter, J. Ch.; Durkin, C.; Falciatore, A.; Fournet, J.; Haruta, M.; Huysman, M. J. J.; Jenkins, B. D.; Jiroutová, Kateřina; Jorgensen, R. E.; Joubert, Y.; Kaplan, A.; Kröger, N.; Kroth, P. G.; La Roche, J.; Lindquist, E.; Lommer, M.; Martin–Jézéquel, V.; Lopez, P. J.; Lucas, S.; Mangogna, M.; McGinnis, K.; Medlin, L. K.; Montsant, A.; Oudot–Le Secq, M.-P.; Napoli, C.; Oborník, Miroslav; Schnitzler Parker, M.; Petit, J.-L.; Porcel, B. M.; Poulsen, N.; Robison, M.; Rychlewski, L.; Rynearson, T. A.; Schmutz, J.; Shapiro, H.; Siaut, M.; Stanley, M.; Sussman, M. R.; Taylor, A. R.; Vardi, A.; von Dassow, P.; Vyverman, W.; Willis, A.; Wyrwicz, L. S.; Rokhsar, D. S.; Weissenbach, J.; Armbrust, E. V.; Green, B. R.; Van de Peer, Y.; Grigoriev, I. V.

    2008-01-01

    Roč. 456, 13-11-2008 (2008), s. 239-244 ISSN 0028-0836 Institutional research plan: CEZ:AV0Z60220518 Keywords : Phaeodactylum * genome * evolution * diatom Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 31.434, year: 2008

  20. Models for calculation of dissociation energies of homonuclear diatomic molecules

    International Nuclear Information System (INIS)

    Brewer, L.; Winn, J.S.

    1979-08-01

    The variation of known dissociation energies of the transition metal diatomics across the Periodic Table is rather irregular like the bulk sublimation enthalpy, suggesting that the valence-bond model for bulk metallic systems might be applicable to the gaseous diatomic molecules and the various intermediate clusters. Available dissociation energies were converted to valence-state bonding energies considering various degrees of promotion to optimize the bonding. The degree of promotion of electrons to increase the number of bonding electrons is smaller than for the bulk, but the trends in bonding energy parallel the behavior found for the bulk metals. Thus using the established trends in bonding energies for the bulk elements, it was possible to calculate all unknown dissociation energies to provide a complete table of dissociation energies for all M 2 molecules from H 2 to Lr 2 . For solids such as Mg, Al, Si and most of the transition metals, large promotion energies are offset by strong bonding between the valence state atoms. The main question is whether bonding in the diatomics is adequate to sustain extensive promotion. The most extreme example for which a considerable difference would be expected between the bulk and the diatomics would be that of the Group IIA and IIB metals. The first section of this paper which deals with the alkaline earths Mg and Ca demonstrates a significant influence of the excited valence state even for these elements. The next section then expands the treatment to transition metals

  1. Diatoms in peat – dominant producers in a changing environment?

    DEFF Research Database (Denmark)

    Kokfelt, Ulla; Struyf, Eric; Randsalu, Linda

    2009-01-01

    to another, the old vegetation may be suppressed, die out or start to decay, and some time may pass until a new mire vegetation is fully established. Here, we demonstrate that diatoms may thrive during such transitions, creating isolated and shallow peat layers with significantly elevated biogenic silica...

  2. Molecular basis of chromatic adaptation in pennate diatom Phaeodactylum tricornutum

    Czech Academy of Sciences Publication Activity Database

    Herbstová, Miroslava; Bína, David; Koník, P.; Gardian, Zdenko; Vácha, František; Litvín, Radek

    2015-01-01

    Roč. 1847, 6-7 (2015), s. 534-543 ISSN 0005-2728 R&D Projects: GA ČR GBP501/12/G055 Institutional support: RVO:60077344 Keywords : Chromatic adaptation * Diatom * Heterokonta * Light harvesting antenna Subject RIV: CE - Biochemistry Impact factor: 4.864, year: 2015

  3. The effects of phosphorus limitation on carbon metabolism in diatoms.

    Science.gov (United States)

    Brembu, Tore; Mühlroth, Alice; Alipanah, Leila; Bones, Atle M

    2017-09-05

    Phosphorus is an essential element for life, serving as an integral component of nucleic acids, lipids and a diverse range of other metabolites. Concentrations of bioavailable phosphorus are low in many aquatic environments. Microalgae, including diatoms, apply physiological and molecular strategies such as phosphorus scavenging or recycling as well as adjusting cell growth in order to adapt to limiting phosphorus concentrations. Such strategies also involve adjustments of the carbon metabolism. Here, we review the effect of phosphorus limitation on carbon metabolism in diatoms. Two transcriptome studies are analysed in detail, supplemented by other transcriptome, proteome and metabolite data, to gain an overview of different pathways and their responses. Phosphorus, nitrogen and silicon limitation responses are compared, and similarities and differences discussed. We use the current knowledge to propose a suggestive model for the carbon flow in phosphorus-replete and phosphorus-limited diatom cells.This article is part of the themed issue 'The peculiar carbon metabolism in diatoms'. © 2017 The Authors.

  4. 21 CFR 582.2122 - Aluminum calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

  5. 21 CFR 182.2122 - Aluminum calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Aluminum calcium silicate. 182.2122 Section 182.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

  6. Suppressive effects of a polymer sodium silicate solution on ...

    African Journals Online (AJOL)

    Sodium silicate was dissolved in water in either a monomer form or polymer form; the effects of both forms of sodium silicate aqueous solution on rose powdery mildew and root rot diseases of miniature rose were examined. Both forms of sodium silicate aqueous solution were applied to the roots of the miniature rose.

  7. 40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section for...

  8. Doping of magnetite nanoparticles facilitates clean harvesting of diatom oil as biofuel for sustainable energy

    Science.gov (United States)

    Kumar, Vikas; Singh, Ramesh; Thakur, Shipra; Ballabh Joshi, Khashti; Vinayak, Vandana

    2018-04-01

    Photosynthetic unicellular brown algae diatoms are considered as photobioreactors (PBRs) that synthesize and store oil in the form of lipid droplets and the much of the crude oil we use comes from fossil diatoms. The clean extraction of this crude oil from diatoms is difficult task. The construction of green chemical protocols for the clean separation of diatom oil from cells without killing or to harm the diatom cells is still in its primitive stage. In this report we would like to propose that facile doping of magnetite on diatoms can be used for clean oil separation in PBRs. We doped magnetite nanoparticles onto the surface of diatom Diadesmis confervaceae a diatom which oozes oil naturally. Doping magnetite onto diatoms can also facilitate easy separation of oil when cells are kept in an electromagnetic field. The cell wall of diatom besides having SiOH group has 281 amino acids of which 187–188 amino acids are conserved and are known for metal binding sites. The magnetite nanoparticles bind to the SiOH groups and metal binding sites of amino acids. The presence of appropriate amine functionalized linkers forming peptide aminosilane shells can further facilitate the binding of peptide/polypeptides which can be used in drug delivery. Besides this the magnetite doped diatoms have wide applications in removal of phosphates and chromium from waste water too.

  9. Toxicity of dissolved and precipitated aluminium to marine diatoms.

    Science.gov (United States)

    Gillmore, Megan L; Golding, Lisa A; Angel, Brad M; Adams, Merrin S; Jolley, Dianne F

    2016-05-01

    Localised aluminium contamination can lead to high concentrations in coastal waters, which have the potential for adverse effects on aquatic organisms. This research investigated the toxicity of 72-h exposures of aluminium to three marine diatoms (Ceratoneis closterium (formerly Nitzschia closterium), Minutocellus polymorphus and Phaeodactylum tricornutum) by measuring population growth rate inhibition and cell membrane damage (SYTOX Green) as endpoints. Toxicity was correlated to the time-averaged concentrations of different aluminium size-fractions, operationally defined as aluminium exposure varied between diatom species. C. closterium was the most sensitive species (10% inhibition of growth rate (72-h IC10) of 80 (55-100)μg Al/L (95% confidence limits)) while M. polymorphus (540 (460-600)μg Al/L) and P. tricornutum (2100 (2000-2200)μg Al/L) were less sensitive (based on measured total aluminium). Dissolved aluminium was the primary contributor to toxicity in C. closterium, while a combination of dissolved and precipitated aluminium forms contributed to toxicity in M. polymorphus. In contrast, aluminium toxicity to the most tolerant diatom P. tricornutum was due predominantly to precipitated aluminium. Preliminary investigations revealed the sensitivity of C. closterium and M. polymorphus to aluminium was influenced by initial cell density with aluminium toxicity significantly (paluminium toxicity to diatoms do not involve compromising the plasma membrane. These results indicate that marine diatoms have a broad range in sensitivity to aluminium with toxic mechanisms related to both dissolved and precipitated aluminium. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Stratigraphic and microfossil evidence for hydroclimate changes over the middle to late Holocene in the northern Bahamas from an inland saline lake

    Science.gov (United States)

    van Hengstum, P. J.; Maale, G. E.; Donnelly, J. P.; Onac, B. P.; Sullivan, R.; Winkler, T. S.; Albury, N. A.

    2016-12-01

    No Man's Land is one of the largest inland lakes on the Little Bahama Bank in the northern Bahamas, so its paleoenvironmental history may provide insight into how the regional hydroclimate developed over the Holocene. In its modern state, the site is shallow (aquatic invertebrates (e.g., ostracodes, foraminifera, aquatic mollusks) indicate that the site was a terrestrial ecosystem. However, the site transitioned into a subaqueous freshwater environment at 6400 Cal yrs BP, and the site became a palustrine-lacustrine setting thereafter until 4200 Cal yrs BP. During this time, widespread palustrine-lacustrine carbonate deposition and the appearance of freshwater to low mesohaline microfossils indicates that the lake's salinity was likely oligohaline (charophytes, ostracodes: Candona annae, Cypridopsis vidua, foraminifera: Helenina davescottensis, mollusks: Planorbis, Hydrobia). A salinity increase at 4200 Cal yrs BP is inferred from the appearance of the ostracode Cyprideis americana that typically prefers salinities exceeding 10 psu, and deposition of laminated microbial mats. Thereafter, an organic- rich, algal sapropel unit accumulated that was devoid of any microfossils or mollusks. This unit suggests that the lake hosted a stratified water column, where surface waters supported phytoplankton primary productivity and corrosive or anoxic bottom water conditions either hampered microfossil growth or precluded their preservation. The transition to the modern environment ( 20 psu) at 2600 cal yrs BP is characterized by diversification of brackish ostracodes (Aurila floridana, Dolerocypria inopinata, and Hemicyprideis setipunctata), foraminifera (Elphidium spp., Ammonia beccarii, Triloculina oblonga) and mollusks (Anomalocardia, Cerithidea). Over the middle to late Holocene, it appears that the stratigraphic development and salinity changes in No Man's Land has been driven by groundwater-level rise in response to Holocene sea-level rise, the regional delivery of fresh

  11. Kinetic control on Zn isotope signatures recorded in marine diatoms

    Science.gov (United States)

    Köbberich, Michael; Vance, Derek

    2017-08-01

    Marine diatoms dominate the oceanic cycle of the essential micronutrient zinc (Zn). The stable isotopes of zinc and other metals are increasingly used to understand trace metal micronutrient cycling in the oceans. One clear feature of the early isotope data is the heavy Zn isotope signature of the average oceanic dissolved pool relative to the inputs, potentially driven by uptake of light isotopes into phytoplankton cells and export to sediments. However, despite the fact that diatoms strip Zn from surface waters across the Antarctic polar front in the Southern Ocean, the local upper ocean is not isotopically heavy. Here we use culturing experiments to quantify the extent of Zn isotope fractionation by diatoms and to elucidate the mechanisms driving it. We have cultured two different open-ocean diatom species (T. oceanica and Chaetoceros sp.) in a series of experiments at constant medium Zn concentration but at bioavailable medium Fe ranging from limiting to replete. We find that T. oceanica can maintain high growth rates and Zn uptake rates over the full range of bioavailable iron (Fe) investigated, and that the Zn taken up has a δ66Zn that is unfractionated relative to that of the bioavailable free Zn in the medium. The studied representative of the genus Chaetoceros, on the other hand, shows more significantly reduced Zn uptake rates at low Fe and records more variable biomass δ66Zn signatures, of up to 0.85‰ heavier than the medium. We interpret the preferential uptake of heavy isotopes at extremely low Zn uptake rates as potentially due to either of the following two mechanisms. First, the release of extracellular polymeric substances (EPS), at low Fe levels, may preferentially scavenge heavy Zn isotopes. Second, the Zn uptake rate may be slow enough to establish pseudo-equilibrium conditions at the transporter site, with heavy Zn isotopes forming more stable surface complexes. Thus we find that, in our experiments, Fe-limitation exerts a key control that

  12. Diatom assemblage in a tropical lake of northeastern Brazil

    Directory of Open Access Journals (Sweden)

    Lilian Rodrigues do Nascimento

    2010-02-01

    Full Text Available The composition and spatial variation of diatom assemblage in surface sediments of Caçó Lake (shallow, mesotrophic and weakly acid lake - Maranhão State, Brazil were analyzed in order to know the distribution pattern of the species along the lake during rainy season (April 1999. Four zones were established in the lake based on 21 diatoms species and habitat affinities. The first three zones (prime three meters deep to six meters deep were marked by the occurrence of Pinnularia gigas, Frustulia rhomboides, Encyonopsis krasskei, Eunotia camelus, E. femoriformis and E. monodon. Zone IV (seven to nine meters deep was inhabited mainly by Surirella biseriata and Fragilariforma floridana. During the beginning of the rainy season, the diatom assemblage in Caçó Lake was composed mainly by benthic and epiphytic forms that reflected the low lake levels and the abundance of littoral vegetation present in this lake.Com o objetivo de se conhecer a dinâmica espacial e a distribuição das diatomáceas contidas no sedimento superficial do lago Caçó, durante o período de chuvas (abril de 1999 foram realizadas coletas em um "transect" horizontal. A partir da observação destas coletas efetuadas a cada 1 metro pode-se observar que a distribuição das diatomáceas esteve fortemente ligada a ocorrência do banco de macrófitas da sua margem, com a ocorrência maciça das espécies epifíticas e bentônicas. A análise de agrupamento de dados permitiu uma melhor visualização, da sua distribuição a cada profundidade e também das associações específicas em cada zona. Os resultados deste estudo permitiram concluir que a ocorrência e distribuição das diatomáceas do Lago Caçó está fortemente ligada ao banco de macrófitas localizado em suas margens, definindo assim zonas características dentro do lago.

  13. Final report on the safety assessment of potassium silicate, sodium metasilicate, and sodium silicate.

    Science.gov (United States)

    Elmore, Amy R

    2005-01-01

    Potassium Silicate, Sodium Metasilicate, and Sodium Silicate combine metal cations with silica to form inorganic salts used as corrosion inhibitors in cosmetics. Sodium Metasilicate also functions as a chelating agent and Sodium Silicate as a buffering and pH adjuster. Sodium Metasilicate is currently used in 168 formulations at concentrations ranging from 13% to 18%. Sodium Silicate is currently used in 24 formulations at concentrations ranging from 0.3% to 55%. Potassium Silicate and Sodium Silicate have been reported as being used in industrial cleaners and detergents. Sodium Metasilicate is a GRAS (generally regarded as safe) food ingredient. Aqueous solutions of Sodium Silicate species are a part of a chemical continuum of silicates based on an equilibrium of alkali, water, and silica. pH determines the solubility of silica and, together with concentration, determines the degree of polymerization. Sodium Silicate administered orally is readily absorbed from the alimentary canal and excreted in the urine. The toxicity of these silicates has been related to the molar ratio of SiO2/Na2O and the concentration being used. The Sodium Metasilicate acute oral LD50 ranged from 847 mg/kg in male rats to 1349.3 mg/kg in female rats and from 770 mg/kg in female mice to 820 mg/kg in male mice. Gross lesions of variable severity were found in the oral cavity, pharynx, esophagus, stomach, larynx, lungs, and kidneys of dogs receiving 0.25 g/kg or more of a commercial detergent containing Sodium Metasilicate; similar lesions were also seen in pigs administered the same detergent and dose. Male rats orally administered 464 mg/kg of a 20% solution containing either 2.0 or 2.4 to 1.0 ratio of sodium oxide showed no signs of toxicity, whereas doses of 1000 and 2150 mg/kg produced gasping, dypsnea, and acute depression. Dogs fed 2.4 g/kg/day of Sodium Silicate for 4 weeks had gross renal lesions but no impairment of renal function. Dermal irritation of Potassium Silicate, Sodium

  14. Insight into silicate-glass corrosion mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Cailleteau, C; Angeli, F; Gin, S; Jollivet, P [CEA VALRHO, DEN, Lab Etude Comportement Long Terme, F-30207 Bagnols Sur Ceze, (France); Devreux, F [Ecole Polytech, CNRS, Lab Phys Mat Condensee, F-91128 Palaiseau, (France); Jestin, J [CEA, CNRS, Lab Leon Brillouin, F-91191 Gif Sur Yvette, (France); Spalla, O [CEA, DSM, Lab Interdisciplinaire Org Nanometr et Supramol, F-91191 Gif Sur Yvette, (France)

    2008-07-01

    The remarkable chemical durability of silicate glass makes it suitable for a wide range of applications. The slowdown of the aqueous glass corrosion kinetics that is frequently observed at long time is generally attributed to chemical affinity effects (saturation of the solution with respect to silica). Here, we demonstrate a new mechanism and highlight the impact of morphological transformations in the alteration layer on the leaching kinetics. A direct correlation between structure and reactivity is revealed by coupling the results of several structure-sensitive experiments with numerical simulations at mesoscopic scale. The sharp drop in the corrosion rate is shown to arise from densification of the outer layers of the alteration film, leading to pore closure. The presence of insoluble elements in the glass can inhibit the film restructuring responsible for this effect. This mechanism may be more broadly applicable to silicate minerals. (authors)

  15. Sorption of Europium in zirconium silicate

    International Nuclear Information System (INIS)

    Garcia R, G.

    2004-01-01

    Some minerals have the property of sipping radioactive metals in solution, that it takes advantage to manufacture contention barriers that are placed in the repositories of nuclear wastes. The more recent investigations are focused in the development of new technologies guided to the sorption of alpha emissors on minerals which avoid their dispersion in the environment. In an effort to contribute to the understanding of this type of properties, some studies of sorption of Europium III are presented like homologous of the americium, on the surface of zirconium silicate (ZrSiO 4 ). In this work the results of sorption experiences are presented as well as the interpretation of the phenomena of the formation of species in the surface of the zirconium silicate. (Author)

  16. Effects of ionization on silicate glasses

    International Nuclear Information System (INIS)

    Primak, W.

    1982-02-01

    This evaluation of radiation effects in silicate glasses caused by ionization is based on our own investigations, on material collected in our files (reports, articles, and notes), and on a computer literature search through recent issues of Physics Abstracts and Chemical Abstracts (and the apparently pertinent references which appeared). Some of our recent results, available heretofore only in internal correspondence, are presented in some detail. It is concluded that research into the behavior of silicate glasses generally will be required before the specific effects in the radioactive waste storage glasses can be properly understood and evaluated. Two particular neglected areas of investigation are targeted for immediate concern: a kinetic analysis of annealing data and the acquisition of data on effects of irradiation at controlled elevated temperatures

  17. Stability constants for silicate adsorbed to ferrihydrite

    DEFF Research Database (Denmark)

    Hansen, Hans Christian Bruun; Wetche, T.P.; Raulund-Rasmussen, Karsten

    1994-01-01

    Intrinsic surface acidity constants (K(a1)intr, K(a2)intr) and surface complexation constant for adsorption of orthosilicate onto synthetic ferrihydrite (K(Si) for the complex = FeOSi(OH)3) have been determined from acid/base titrations in 0.001-0.1 m NaClO4 electrolytes and silicate adsorption...... experiments in 0.01 m NaNO3 electrolyte (pH 3-6). The surface equilibrium constants were calculated according to the two-layer model by Dzombak & Morel (1990). Near equilibrium between protons/hydroxyls in solution and the ferrihydrite surface was obtained within minutes while equilibration with silicate...

  18. Diatom diet selectivity by early post-larval abalone Haliotis diversicolor supertexta under hatchery conditions

    Science.gov (United States)

    Zhang, Yuyu; Gao, Yahui; Liang, Junrong; Chen, Changping; Zhao, Donghai; Li, Xuesong; Li, Yang; Wu, Wenzhong

    2010-11-01

    Benthic diatoms constitute the primary diet of abalone during their early stages of development. To evaluate the dietary preferences of early post-larval abalone, Haliotis diversicolor supertexta, we analyzed the gut contents of post-larvae that settled on diatom films. We compared the abundance and species diversity of diatom assemblages in the gut to those of the epiphytic diatom assemblages on the attachment films, and identified 40 benthic diatom species in the gut contents of post-larvae 12 to 24 d after settlement. The most abundant taxa in the gut contents were Navicula spp., Amphora copulate, and Amphora coffeaeformis. Navicula spp. accounted for 64.0% of the cell density. In the attachment films, we identified 110 diatom species belonging to 38 genera. Pennate diatoms were the dominant members including the species Amphiprora alata, Cocconeis placentula var. euglypta, Cylindrotheca closterium, Navicula sp. 2, and A. coffeaeformis. Nano-diatoms (abalone seed. The difference of the composition and abundance of diatoms between in the guts and on the biofilms suggests that early post-larval grazing was selective. An early post-larval abalone preferred nano-diatoms and the genera Navicula and Amphora during the month after settlement.

  19. SILICATE EVOLUTION IN BROWN DWARF DISKS

    International Nuclear Information System (INIS)

    Riaz, B.

    2009-01-01

    We present a compositional analysis of the 10 μm silicate spectra for brown dwarf disks in the Taurus and Upper Scorpius (UppSco) star-forming regions, using archival Spitzer/Infrared Spectrograph observations. A variety in the silicate features is observed, ranging from a narrow profile with a peak at 9.8 μm, to nearly flat, low-contrast features. For most objects, we find nearly equal fractions for the large-grain and crystalline mass fractions, indicating both processes to be active in these disks. The median crystalline mass fraction for the Taurus brown dwarfs is found to be 20%, a factor of ∼2 higher than the median reported for the higher mass stars in Taurus. The large-grain mass fractions are found to increase with an increasing strength in the X-ray emission, while the opposite trend is observed for the crystalline mass fractions. A small 5% of the Taurus brown dwarfs are still found to be dominated by pristine interstellar medium-like dust, with an amorphous submicron grain mass fraction of ∼87%. For 15% of the objects, we find a negligible large-grain mass fraction, but a >60% small amorphous silicate fraction. These may be the cases where substantial grain growth and dust sedimentation have occurred in the disks, resulting in a high fraction of amorphous submicron grains in the disk surface. Among the UppSco brown dwarfs, only usd161939 has a signal-to-noise ratio high enough to properly model its silicate spectrum. We find a 74% small amorphous grain and a ∼26% crystalline mass fraction for this object.

  20. Adsorption of dimeric surfactants in lamellar silicates

    Energy Technology Data Exchange (ETDEWEB)

    Balcerzak, Mateusz; Pietralik, Zuzanna [Department of Macromolecular Physics, Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Domka, Ludwik [Department of Metalorganic Chemistry, Faculty of Chemistry, A. Mickiewicz University, Grunwaldzka 6, 60-780 Poznań (Poland); Skrzypczak, Andrzej [Institute of Chemical Technology, Poznań University of Technology, Berdychowo 4, 60-965 Poznań (Poland); Kozak, Maciej, E-mail: mkozak@amu.edu.pl [Department of Macromolecular Physics, Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland)

    2015-12-01

    Highlights: • The intercalation of dimeric surfactants changed the morphology of MMT samples. • XRD indicated structures formed by surfactant molecules in interlayer space. • The four-step thermal decomposition of dimeric surfactant, confirms intercalation. - Abstract: The adsorption of different types of cationic surfactants in lamellar silicates changes their surface character from hydrophilic to hydrophobic. This study was undertaken to obtain lamellar silicates modified by a series of novel dimeric (gemini) surfactants of different length alkyl chains and to characterise these organophilised materials. Synthetic sodium montmorillonite SOMASIF® ME 100 (M) and enriched bentonite of natural origin (Nanoclay – hydrophilic bentonite®) were organophilised with dimeric (gemini) surfactants (1,1′-(1,4-butanediyl)bis(alkoxymethyl)imidazolium dichlorides). As a result of surfactant molecule adsorption in interlamellar space, the d-spacing (d{sub 001}) increased from 0.97 nm (for the anhydrous structure) to 2.04 nm. A Fourier transform infrared spectroscopy (FTIR) analysis of the modified systems reveals bands assigned to the stretching vibrations of the CH{sub 2} and CH{sub 3} groups and the scissoring vibrations of the NH group from the structure of the dimeric surfactants. Thermogravimetric (TG) and derivative thermogravimetric (DTG) studies imply a four-stage process of surfactant decomposition. Scanning electron microscopy (SEM) images provide information on the influence of dimeric surfactant intercalation into the silicate structures. Particles of the modified systems show a tendency toward the formation of irregularly shaped agglomerates.

  1. Lead-silicate glass optical microbubble resonator

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Pengfei, E-mail: pengfei.wang@dit.ie [Photonics Research Centre, Dublin Institute of Technology, Kevin Street, Dublin 8 (Ireland); Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ (United Kingdom); Ward, Jonathan; Yang, Yong; Chormaic, Síle Nic [Light-Matter Interactions Unit, OIST Graduate University, 1919-1 Tancha, Onna-son, Okinawa 904-0495 (Japan); Feng, Xian; Brambilla, Gilberto [Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ (United Kingdom); Farrell, Gerald [Photonics Research Centre, Dublin Institute of Technology, Kevin Street, Dublin 8 (Ireland)

    2015-02-09

    Microbubble whispering gallery resonators have the potential to become key components in a variety of active and passive photonic circuit devices by offering a range of significant functionalities. Here, we report on the fabrication, optical characterization, and theoretical analysis of lead-silicate glass and optical microbubble resonators. Evanescent field coupling to the microbubbles was achieved using a 1 μm diameter, silica microfiber at a wavelength of circa 775 nm. High Q-factor modes were efficiently excited in both single-stem and two-stem, lead-silicate glass, and microbubble resonators, with bubble diameters of 38 μm (single-stem) and 48 μm (two-stem). Whispering gallery mode resonances with Q-factors as high as 2.3 × 10{sup 5} (single-stem) and 7 × 10{sup 6} (two-stem) were observed. By exploiting the high-nonlinearity of the lead-silicate glass, this work will act as a catalyst for studying a range of nonlinear optical effects in microbubbles, such as Raman scattering and four-wave mixing, at low optical powers.

  2. Momentum autocorrelation function of a classic diatomic chain

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Ming B., E-mail: mingbyu@gmail.com

    2016-10-23

    A classical harmonic diatomic chain is studied using the recurrence relations method. The momentum autocorrelation function results from contributions of acoustic and optical branches. By use of convolution theorem, analytical expressions for the acoustic and optical contributions are derived as even-order Bessel function expansions with coefficients given in terms of integrals of elliptic functions in real axis and a contour parallel to the imaginary axis, respectively. - Highlights: • Momentum autocorrelation function of a classic diatomic chain is studied. • It is derived as even-order Bessel function expansion using the convolution theorem. • The expansion coefficients are integrals of elliptic functions. • Addition theorem is used to reduce complex elliptic function to complex sum of real ones.

  3. Interface states in a class of heterojunctions between diatomic semiconductors

    International Nuclear Information System (INIS)

    Kandilarov, B.D.; Detcheva, V.

    1979-09-01

    The theory of interface state in heterojunctions between diatomic semiconductors is developed in the framework of the S-matrix approach and on the basis of a one-dimensional model. The condition for the existence of interface states is explicitly derived for undeformed and deformed herterojunctions. Numerical analysis is performed and several particular cases are discussed in order to clarify the general features of the problem. (author)

  4. Novel sex cells and evidence for sex pheromones in diatoms.

    Science.gov (United States)

    Sato, Shinya; Beakes, Gordon; Idei, Masahiko; Nagumo, Tamotsu; Mann, David G

    2011-01-01

    Diatoms belong to the stramenopiles, one of the largest groups of eukaryotes, which are primarily characterized by a presence of an anterior flagellum with tubular mastigonemes and usually a second, smooth flagellum. Based on cell wall morphology, diatoms have historically been divided into centrics and pennates, of which only the former have flagella and only on the sperm. Molecular phylogenies show the pennates to have evolved from among the centrics. However, the timing of flagellum loss--whether before the evolution of the pennate lineage or after--is unknown, because sexual reproduction has been so little studied in the 'araphid' basal pennate lineages, to which Pseudostaurosira belongs. Sexual reproduction of an araphid pennate, Pseudostaurosira trainorii, was studied with light microscopy (including time lapse observations and immunofluorescence staining observed under confocal scanning laser microscopy) and SEM. We show that the species produces motile male gametes. Motility is mostly associated with the extrusion and retrieval of microtubule-based 'threads', which are structures hitherto unknown in stramenopiles, their number varying from one to three per cell. We also report experimental evidence for sex pheromones that reciprocally stimulate sexualization of compatible clones and orientate motility of the male gametes after an initial 'random walk'. The threads superficially resemble flagella, in that both are produced by male gametes and contain microtubules. However, one striking difference is that threads cannot beat or undulate and have no motility of their own, and they do not bear mastigonemes. Threads are sticky and catch and draw objects, including eggs. The motility conferred by the threads is probably crucial for sexual reproduction of P. trainorii, because this diatom is non-motile in its vegetative stage but obligately outbreeding. Our pheromone experiments are the first studies in which gametogenesis has been induced in diatoms by cell

  5. Bacterial colonization of the freshwater planktonic diatom Fragilaria crotonensis

    Czech Academy of Sciences Publication Activity Database

    Znachor, Petr; Šimek, Karel; Nedoma, Jiří

    2012-01-01

    Roč. 66, č. 1 (2012), s. 87-94 ISSN 0948-3055 R&D Projects: GA ČR(CZ) GA206/08/0015; GA ČR(CZ) GAP504/11/2177; GA ČR(CZ) GAP504/11/2182 Institutional research plan: CEZ:AV0Z60170517 Keywords : PDMPO * bacterial colonization * diatoms * Fragilaria crotonensis * flood * reservoir Subject RIV: DA - Hydrology ; Limnology Impact factor: 2.037, year: 2012

  6. Novel sex cells and evidence for sex pheromones in diatoms.

    Directory of Open Access Journals (Sweden)

    Shinya Sato

    Full Text Available BACKGROUND: Diatoms belong to the stramenopiles, one of the largest groups of eukaryotes, which are primarily characterized by a presence of an anterior flagellum with tubular mastigonemes and usually a second, smooth flagellum. Based on cell wall morphology, diatoms have historically been divided into centrics and pennates, of which only the former have flagella and only on the sperm. Molecular phylogenies show the pennates to have evolved from among the centrics. However, the timing of flagellum loss--whether before the evolution of the pennate lineage or after--is unknown, because sexual reproduction has been so little studied in the 'araphid' basal pennate lineages, to which Pseudostaurosira belongs. METHODS/PRINCIPAL FINDING: Sexual reproduction of an araphid pennate, Pseudostaurosira trainorii, was studied with light microscopy (including time lapse observations and immunofluorescence staining observed under confocal scanning laser microscopy and SEM. We show that the species produces motile male gametes. Motility is mostly associated with the extrusion and retrieval of microtubule-based 'threads', which are structures hitherto unknown in stramenopiles, their number varying from one to three per cell. We also report experimental evidence for sex pheromones that reciprocally stimulate sexualization of compatible clones and orientate motility of the male gametes after an initial 'random walk'. CONCLUSIONS/SIGNIFICANCE: The threads superficially resemble flagella, in that both are produced by male gametes and contain microtubules. However, one striking difference is that threads cannot beat or undulate and have no motility of their own, and they do not bear mastigonemes. Threads are sticky and catch and draw objects, including eggs. The motility conferred by the threads is probably crucial for sexual reproduction of P. trainorii, because this diatom is non-motile in its vegetative stage but obligately outbreeding. Our pheromone experiments

  7. Interactions of bacteria with diatoms: Influence on natural marine biofilms.

    Digital Repository Service at National Institute of Oceanography (India)

    Khandeparker, L.; DeCosta, P.M.; Anil, A.C.; Sawant, S.S.

    therein). In fact, biofilms are considered a reservoir and source of dissemination for V. cholerae (Shikuma & Hadfield 2010). Nutrient concentrations in the surrounding waters also affect the progression of the biofilm community (Qian et al. 2007... to render diatom monocultures near axenic (Patil & Anil 2005c). The following diluents were used – Aged Sea Water (ASW; unenriched control), ASW+streptomycin (ASW+S), ASW+chloramphenicol (ASW+C), f/2 medium (Guillard and Ryther, 1962) prepared in ASW [f...

  8. Recombinational laser employing electron transitions of diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Biriukov, A S; Prokhorov, A M; Shelepin, L A; Shirokov, N N

    1974-12-01

    Conditions are established for obtaining laser action in the visible and uv regions of the spectrum, using transitions between electronic states of diatomic molecules during recombination of a dissociated gas. The mechanism of population inversion was studied for the oxygen molecule, and gain estimates were obtained for laser action at a wavelength of 4881 A. The feasibility of laser action at other wavelengths was examined.

  9. Single ionization of diatomic molecules by bare ion impact

    International Nuclear Information System (INIS)

    Purkait, M; Mandal, C R

    2014-01-01

    The molecular three-Coulomb wave model (M3CW) has been extensively used to study the double-differential ionization cross sections (DDCS) of diatomic molecules by the impact of bare ions at intermediate and high energies. In this model, the distortion of the initial channel by the incoming projectile is also included. The present DDCS results are found to be in good accord both with the experiment of Baran et al 2008 as well as with other theory

  10. Radiation damage in diatomic materials at high doses

    International Nuclear Information System (INIS)

    Hobbs, L.W.; Hughes, A.E.

    1975-10-01

    Radiation effects in diatomic materials can differ structurally from those in metals because of the need to take into account different displacement rates on the two sublattices and the inevitable stoichiometric implications; in most diatomic insulators the anion species has the greater displacement cross section. Anion point defect stabilisation in heavily-irradiated (0.1 to 10 dpa) diatomic insulators has been studied using radiolysis of alkali and alkaline earth halides. A temperatures > 0.3 Tsub(m), all anion defects are mobile and can aggregate. Aggregation of anion interstitials results in creation of perfect dislocation loops without the need for primary cation displacements; simultaneous formation of substitutional anion molecular centres provides the necessary cation interstitials. Aggregation of anion vacancies leads to formation of metallic inclusions of the cation species, in some cases in an ordered array, which is the analogue, on a single sublattice, to the void lattice in metals. Availability of sinks for both anion interstitials and anion vacancies yields defect growth kinetics similar to those observed during formation of voids in irradiated metals, and a very high level of damage (approximately 10%) can be sustained in the lattice. The width of the temperature region concerned is much narrower, however, due to the possibility of recombination of aggregated or re-emitted anion vacancies with mobile or dispersed anion molecular defects; the latter can also aggregate to form fluid anion molecular inclusions and so complete the decomposition of the solid into separate phases of its constituent elements. (author)

  11. A Rapid Method for the Determination of Fucoxanthin in Diatom

    Directory of Open Access Journals (Sweden)

    Li-Juan Wang

    2018-01-01

    Full Text Available Fucoxanthin is a natural pigment found in microalgae, especially diatoms and Chrysophyta. Recently, it has been shown to have anti-inflammatory, anti-tumor, and anti-obesityactivity in humans. Phaeodactylum tricornutum is a diatom with high economic potential due to its high content of fucoxanthin and eicosapentaenoic acid. In order to improve fucoxanthin production, physical and chemical mutagenesis could be applied to generate mutants. An accurate and rapid method to assess the fucoxanthin content is a prerequisite for a high-throughput screen of mutants. In this work, the content of fucoxanthin in P. tricornutum was determined using spectrophotometry instead of high performance liquid chromatography (HPLC. This spectrophotometric method is easier and faster than liquid chromatography and the standard error was less than 5% when compared to the HPLC results. Also, this method can be applied to other diatoms, with standard errors of 3–14.6%. It provides a high throughput screening method for microalgae strains producing fucoxanthin.

  12. Models of the delayed nonlinear Raman response in diatomic gases

    International Nuclear Information System (INIS)

    Palastro, J. P.; Antonsen, T. M. Jr.; Pearson, A.

    2011-01-01

    We examine the delayed response of a diatomic gas to a polarizing laser field with the goal of obtaining computationally efficient methods for use with laser pulse propagation simulations. We demonstrate that for broadband pulses, heavy molecules such as O 2 and N 2 , and typical atmospheric temperatures, the initial delayed response requires only classical physics. The linear kinetic Green's function is derived from the Boltzmann equation and shown to be in excellent agreement with full density-matrix calculations. A straightforward perturbation approach for the fully nonlinear, kinetic impulse response is also presented. With the kinetic theory a reduced fluid model of the diatomic gas' orientation is derived. Transport coefficients are introduced to model the kinetic phase mixing of the delayed response. In addition to computational rapidity, the fluid model provides intuition through the use of familiar macroscopic quantities. Both the kinetic and the fluid descriptions predict a nonlinear steady-state alignment after passage of the laser pulse, which in the fluid model is interpreted as an anisotropic temperature of the diatomic fluid with respect to motion about the polarization axis.

  13. Optimisation of critical medium components and culture conditions for enhanced biomass and lipid production in the oleaginous diatom Navicula phyllepta: a statistical approach.

    Science.gov (United States)

    Sabu, Sanyo; Singh, Isaac Sarojini Bright; Joseph, Valsamma

    2017-12-01

    Diatoms hold great promise as potential sources of biofuel production. In the present study, the biomass and lipid production in the marine diatom Navicula phyllepta, isolated from Cochin estuary, India and identified as a potential biodiesel feedstock, were optimized using Plackett-Burman (PB) statistical experimental design followed by central composite design (CCD) and response surface methodology (RSM). The growth analyses of the isolate in different nitrogen sources, salinities and five different enriched sea water media showed the best growth in the cheapest medium with minimum components using urea as nitrogen source at salinity between 25 and 40 g kg -1 . Plackett-Burman experimental analyses for screening urea, sodium metasilicate, sodium dihydrogen phosphate, ferric chloride, salinity, temperature, pH and agitation influencing lipid and biomass production showed that silicate and temperature had a positive coefficient on biomass production, and temperature had a significant positive coefficient, while urea and phosphate showed a negative coefficient on lipid content. A 2 4 factorial central composite design (FCCD) was used to optimize the concentration of the factors selected. The optimized media resulted in 1.62-fold increase (64%) in biomass (1.2 ± 0.08 g L -1 ) and 1.2-fold increase (22%) in estimated total lipid production (0.11 ± 0.003 g L -1 ) compared to original media within 12 days of culturing. A significantly higher biomass and lipid production in the optimized medium demands further development of a two-stage strategy of biomass production followed by induction of high lipid production under nutrient limitation or varying culture conditions for large-scale production of biodiesel from the marine diatom.

  14. A 900-Year Diatom and Chrysophyte Record of Spring Mixing and Summer Stratification From Varved Lake Mina, West-Central Minnesota, USA

    Science.gov (United States)

    St. Jacques, J.; Cumming, B. F.; Smol, J. P.

    2009-05-01

    A high-resolution, independent pollen-inferred paleoclimate record and direct algal seasonality data from the actual time of sediment deposition are used to interpret the high-resolution diatom and chrysophyte record of varved Lake Mina, west-central Minnesota, USA during AD 1116-2002. This direct algal seasonality information was obtained by a new technique of splitting varves into constituent winter-spring and summer lamina, and separately analyzing the siliceous algae in each layer. Analyses of integrated, continuous four-year diatom and chrysophyte samples from a sedimentary sequence show that the time period AD 1116-1478 (i.e. the Atlantic- centered Medieval Climate Anomaly (MCA)) was characterized by periods of vigorous and prolonged spring mixing, suggesting that ice-out occurred early. However, the warm summer temperatures in the MCA, particularly in a massive drought spanning AD 1300-1400, frequently caused the lake to stratify strongly, leading to nutrient depletion. During AD 1478-1870 (i.e. the Atlantic-centered Little Ice Age (LIA)), Lake Mina was characterized by weak spring circulation and increasing nutrient depletion, suggesting late ice-out conditions. Strong summer stratification and/or nutrient depletion in both time periods is shown by the occurrence of the nutrient-poor oligotrophic taxon Cyclotella pseudostelligera. The diatom and chrysophyte assemblages of the period of Euro-American settlement AD 1870-2002 show higher nutrient availability and increased spring mixing intensity, due to forest clearance and increasingly earlier ice-out (documented in regional historical records).

  15. Eighty years of food-web response to interannual variation in discharge recorded in river diatom frustules from an ocean sediment core.

    Science.gov (United States)

    Sculley, John B; Lowe, Rex L; Nittrouer, Charles A; Drexler, Tina M; Power, Mary E

    2017-09-19

    Little is known about the importance of food-web processes as controls of river primary production due to the paucity of both long-term studies and of depositional environments which would allow retrospective fossil analysis. To investigate how freshwater algal production in the Eel River, northern California, varied over eight decades, we quantified siliceous shells (frustules) of freshwater diatoms from a well-dated undisturbed sediment core in a nearshore marine environment. Abundances of freshwater diatom frustules exported to Eel Canyon sediment from 1988 to 2001 were positively correlated with annual biomass of Cladophora surveyed over these years in upper portions of the Eel basin. Over 28 years of contemporary field research, peak algal biomass was generally higher in summers following bankfull, bed-scouring winter floods. Field surveys and experiments suggested that bed-mobilizing floods scour away overwintering grazers, releasing algae from spring and early summer grazing. During wet years, growth conditions for algae could also be enhanced by increased nutrient loading from the watershed, or by sustained summer base flows. Total annual rainfall and frustule densities in laminae over a longer 83-year record were weakly and negatively correlated, however, suggesting that positive effects of floods on annual algal production were primarily mediated by "top-down" (consumer release) rather than "bottom-up" (growth promoting) controls.

  16. Eighty years of food-web response to interannual variation in discharge recorded in river diatom frustules from an ocean sediment core

    Science.gov (United States)

    Sculley, John B.; Lowe, Rex L.; Nittrouer, Charles A.; Drexler, Tina M.; Power, Mary E.

    2017-01-01

    Little is known about the importance of food-web processes as controls of river primary production due to the paucity of both long-term studies and of depositional environments which would allow retrospective fossil analysis. To investigate how freshwater algal production in the Eel River, northern California, varied over eight decades, we quantified siliceous shells (frustules) of freshwater diatoms from a well-dated undisturbed sediment core in a nearshore marine environment. Abundances of freshwater diatom frustules exported to Eel Canyon sediment from 1988 to 2001 were positively correlated with annual biomass of Cladophora surveyed over these years in upper portions of the Eel basin. Over 28 years of contemporary field research, peak algal biomass was generally higher in summers following bankfull, bed-scouring winter floods. Field surveys and experiments suggested that bed-mobilizing floods scour away overwintering grazers, releasing algae from spring and early summer grazing. During wet years, growth conditions for algae could also be enhanced by increased nutrient loading from the watershed, or by sustained summer base flows. Total annual rainfall and frustule densities in laminae over a longer 83-year record were weakly and negatively correlated, however, suggesting that positive effects of floods on annual algal production were primarily mediated by “top-down” (consumer release) rather than “bottom-up” (growth promoting) controls. PMID:28874576

  17. A simple digestion method with a Lefort aqua regia solution for diatom extraction.

    Science.gov (United States)

    Wang, Huipin; Liu, Yan; Zhao, Jian; Hu, Sunlin; Wang, Yuzhong; Liu, Chao; Zhang, Yanji

    2015-01-01

    Presence of diatoms in tissues has been considered as a significant sign of drowning. However, there are limitations in the present extraction methods. We developed a new digestion method using the Lefort aqua regia solution (3:1 nitric acid to hydrochloric acid) for diatom extraction and evaluated the digestive capability, diatom destruction, and diatoms' recovery of this new method. The kidney tissues from rabbit mixed with water rich in diatoms were treated by the Lefort aqua regia digestion method (n = 10) and the conventional acid digestion method (n = 10). The results showed that the digestive capability of Lefort aqua regia digestion method was superior to conventional acid digestion method (p 0.05). The Lefort aqua regia reagent is an improvement over the conventional acid digestion for recovery of diatoms from tissue samples. © 2014 American Academy of Forensic Sciences.

  18. Diatoms in acid mine drainage and their role in the formation of iron-rich stromatolites

    Energy Technology Data Exchange (ETDEWEB)

    Brake, S.S.; Hasiotis, S.T.; Dannelly, H.K. [Indiana State University, Terre Haute, IN (United States)

    2004-08-01

    Adverse conditions in the acid mine drainage (AMD) system at the Green Valley mine, Indiana, limit diatom diversity to one species, Nitzschia tubicola. It is present in three distinct microbial consortia: Euglena mutabilis-dominated biofilm, diatom-dominated biofilm, and diatom-exclusive biofilm. E. mutabilis dominates the most extensive biofilm, with lesser numbers of N. tubicola, other eukaryotes, and bacteria. Diatom-dominated biofilm occurs as isolated patches containing N. tubicola with minor fungal hyphae, filamentous algae, E. mutabilis, and bacteria. Diatom-exclusive biofilm is rare, composed entirely of N. tubicola. Diatom distribution is influenced by seasonal and intraseasonal changes in water temperature and chemistry. Diatoms are absent in winter due to cool water temperatures. In summer, isolated patchy communities are present due to warmer water temperatures. In 2001, the diatom community expanded its distribution following a major rainfall that temporarily diluted the effluent, creating hospitable conditions for diatom growth. After several weeks when effluent returned to preexisting conditions, the diatom biofilm retreated to isolated patches, and E. mutabilis biofilm flourished. Iron-rich stromatolites underlie the biofilms and consist of distinct laminae, recording spatial and temporal oscillations in physicochemical conditions and microbial activity. The stromatolites are composed of thin, wavy laminae with partially decayed E. mutabilis biofilm, representing microbial activity and iron precipitation under normal AMD conditions. Alternating with the wavy layers are thicker, porous, spongelike laminae composed of iron precipitated on and incorporated into radiating colonies of diatoms. These layers indicate episodic changes in water chemistry, allowing diatoms to temporarily dominate the system.

  19. Studies on fouling diatoms from the Zuari Estuary, Goa (west coast of India)

    Digital Repository Service at National Institute of Oceanography (India)

    Redekar, P.D.; Wagh, A.B.

    from offshore waters of Bombay High area using aluminium panels and recorded 58 species of fouling diatoms Of these Navicula Coscinodiscus Rhizosolenia and Chaetoceros were found to be common The dominance of Centrales over Pennales in water column... on fouling diatoms from the Zuari estuary, Goa (West coast of India) 119 Pangu (1993) used mild steel, aluminium, fiberglass and glass test panels and the immersion period of panels was long (1 month to 11 months) The fouling diatoms from Waghotana...

  20. Complex dynamics in diatomic molecules. Part II: Quantum trajectories

    International Nuclear Information System (INIS)

    Yang, C.-D.; Weng, H.-J.

    2008-01-01

    The second part of this paper deals with quantum trajectories in diatomic molecules, which has not been considered before in the literature. Morse potential serves as a more accurate function than a simple harmonic oscillator for illustrating a realistic picture about the vibration of diatomic molecules. However, if we determine molecular dynamics by integrating the classical force equations derived from a Morse potential, we will find that the resulting trajectories do not consist with the probabilistic prediction of quantum mechanics. On the other hand, the quantum trajectory determined by Bohmian mechanics [Bohm D. A suggested interpretation of the quantum theory in terms of hidden variable. Phys. Rev. 1952;85:166-179] leads to the conclusion that a diatomic molecule is motionless in all its vibrational eigen-states, which also contradicts probabilistic prediction of quantum mechanics. In this paper, we point out that the quantum trajectory of a diatomic molecule completely consistent with quantum mechanics does exist and can be solved from the quantum Hamilton equations of motion derived in Part I, which is based on a complex-space formulation of fractal spacetime [El Naschie MS. A review of E-Infinity theory and the mass spectrum of high energy particle physics. Chaos, Solitons and Fractals 2004;19:209-36; El Naschie MS. E-Infinity theory - some recent results and new interpretations. Chaos, Solitons and Fractals 2006;29:845-853; El Naschie MS. The concepts of E-infinity. An elementary introduction to the cantorian-fractal theory of quantum physics. Chaos, Solitons and Fractals 2004;22:495-511; El Naschie MS. SU(5) grand unification in a transfinite form. Chaos, Solitons and Fractals 2007;32:370-374; Nottale L. Fractal space-time and microphysics: towards a theory of scale relativity. Singapore: World Scientific; 1993; Ord G. Fractal space time and the statistical mechanics of random works. Chaos, Soiltons and Fractals 1996;7:821-843] approach to quantum

  1. Regularities in Low-Temperature Phosphatization of Silicates

    Science.gov (United States)

    Savenko, A. V.

    2018-01-01

    The regularities in low-temperature phosphatization of silicates are defined from long-term experiments on the interaction between different silicate minerals and phosphate-bearing solutions in a wide range of medium acidity. It is shown that the parameters of the reaction of phosphatization of hornblende, orthoclase, and labradorite have the same values as for clayey minerals (kaolinite and montmorillonite). This effect may appear, if phosphotization proceeds, not after silicate minerals with a different structure and composition, but after a secondary silicate phase formed upon interaction between silicates and water and stable in a certain pH range. Variation in the parameters of the reaction of phosphatization at pH ≈ 1.8 is due to the stability of the silicate phase different from that at higher pH values.

  2. Transformation techniques for metabolic engineering of diatoms and haptophytes: current state and prospects.

    Science.gov (United States)

    Velmurugan, Natarajan; Deka, Deepi

    2018-05-01

    Diatoms and haptophytes represent a key segment of the dominant phytoplankton communities that frequently form massive blooms in the photic zone of the ocean and are considered indicators of global climate changes. Diatoms and haptophytes also play a vital role in the biological carbon fixation in the carbon cycles. Carbon partitioning within diatoms and haptophytes possesses a wide range of chemical compounds and storage materials, such as lipids, carbohydrates, and chlorophyll. Among the marine microorganisms, diatoms and haptophytes have been recognized as promising sources of long- and very long-chain polyunsaturated fatty acids (PUFA). So far, a variety of approaches have been employed for genetic modification in the nuclei of diatoms and haptophytes. Studies on transformation and metabolic engineering in various intracellular genomes, such as chloroplast and mitochondria, are scarce. Particle bombardment, Agrobacterium and PEG-mediated gene transfer, and electroporation have been reported for foreign gene transformation into the diatoms and haptophytes. Antibiotics (G418 and chloramphenicol) and herbicides (zeocin, hygromycin, and norflurazon) have been successfully demonstrated as the best selection markers. Despite the availability of a wide range of molecular tools for foreign gene expression in microalgae, very few promoters (lhcf1, nr, h4, ef2, fcp, and pds) have been reported for diatoms and haptophytes. Therefore, in this review, we first summarize the significant progress that has been achieved in transgene expression in diatoms and haptophytes and highlight the importance and availability of recently developed novel tools that are suitable for transgenic expression in diatoms and haptophytes.

  3. Diatom Attachment at Aquatic Interfaces: Molecular Interactions, Mechanisms, and Physiology of Adhesion

    National Research Council Canada - National Science Library

    Gretz, Michael

    1997-01-01

    .... those more hydrophobic and that bacterial 'preconditioning' has variable effects on adhesion; (3) developed methodology for mass culture of fouling diatoms and isolation of adhesive components; (4...

  4. Comparison between sedimentary and living diatoms in Lago Maggiore (N. Italy: implications of using transfer functions

    Directory of Open Access Journals (Sweden)

    Simona MUSAZZI

    2001-02-01

    Full Text Available We compared the recent history of living planktonic diatom assemblages in Lago Maggiore with the remains found in the topmost section of 14 sediment cores taken from the lake. Sediment samples showed a marked domination of planktonic taxa, but a significant proportion of benthic taxa was found in cores collected close to river mouths. Between-core variability in diatom assemblage and in diatom-inferred total phosphorus concentration was also estimated. The implications of our results for calibration data sets relating environmental variables to diatom assemblages are also discussed.

  5. New silicates of rare earths and calcium

    International Nuclear Information System (INIS)

    Andreev, I.F.; Shevyakov, A.M.; Smorodina, T.P.; Semenov, N.E.

    1975-01-01

    The complex silicates of the third subgroup elements of lanthanides and calcium were synthesized: Ca 3 Er 2 Si 6 O 18 , Ca 3 Lu 2 Si 6 O 18 and Ca 3 Yb 2 Si 6 O 18 . To specify these compounds their physical and chemical properties were studied by means of roentgenographic, IR spectroscopic and crystaloptical methods. The values of Ng, Np,Δn,m,p were determined, the elementary cell parameters: a,b,c,α,β,γ were computed. Existence of such compounds and their analogy in ternary systems MeO-Ln 2 O 3 -SiO 2 were forcasted

  6. Tribo-exoemission from some silicate materials

    International Nuclear Information System (INIS)

    Holzapfel, G.; Lesz, J.; Otto, W.

    1983-01-01

    The tribo-exoemission from some minerals has been investigated in view of applications in the porcelain industries. Milling and sample preparation were performed under defined (liquid and solvent free) conditions. Quartz and the members of the alumo-silicate family feldspar, kaolin, and pegmatite are characterised by a strongly overlapped TSEE-peak between 100 0 C and 200 0 C, growing strongly with the mechanical dispersion of the powders. Thermal (TSEE) as well as optical (OSEE) stimulation reveal pegmatite as the strongest emitter with a very low fading of the tribo-signal at room temperature. (author)

  7. Structure peculiarities of mixed alkali silicate glasses

    International Nuclear Information System (INIS)

    Bershtein, V.A.; Gorbachev, V.V.; Egorov, V.

    1980-01-01

    The thermal porperties and structure of alkali and mixed alkali (Li, Na, K) silicate glasses by means of differential scanning calorimetry (DSC), the positron annihilation method, X-ray fluorescence and infrared (300-30 cm -1 ) spectroscopy were studied. Introduction of different alkali cations in glass results in nonadditive change in their electron structure (bond covalence degree growth) and the thermal behaviour. The different manifestations of mixed alkali effect can be explained by the lessening of long distance Coulomb interactions and strengthening the short-range forces in the mixed alkali glasses. (orig.)

  8. LABORATORY INVESTIGATIONS OF SILICATE MUD CONTAMINATION WITH CALCIUM

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    2004-12-01

    Full Text Available The silicate-based drilling fluid is a low solids KCl/polymer system with the addition of soluble sodium or potassium silicate to enhance inhibition and wellbore stability. Silicate-based drilling fluids exhibit remarkable shale and chalk stabilizing properties, resulting in gauge hole and the formation of firm cuttings when drilling reactive shales and soft chalks. Silicates protect shales by in-situ gellation when exposed to the neutral pore fluid and precipitation, which occurs on contact with divalent ions present at the surface of the shale. Also, silicates prevent the dispersion and washouts when drilling soft chalk by reacting with the Ca2+ ions present on chalk surfaces of cutting and wellbore to form a protective film. The silicate-based drilling fluid can be used during drilling hole section through shale interbeded anhydrite formations because of its superior shale stabilizing characteristics. However, drilling through the anhydrite can decrease the silicate concentration and change rheological and filtration fluid properties. So, the critical concentration of calcium ions should be investigated by lab tests. This paper details the mechanism of shale inhibition using silicate-based drilling fluid, and presents results of lab tests conducted to ascertain the effect of Ca2+ ions on silicate level in the fluid and the fluid properties.

  9. Location of silicic caldera formation in arc settings

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, Gwyneth R; Mahood, Gail A [Department of Geological and Environmental Sciences, Stanford University, 450 Serra, Mall, Building 320, Stanford, CA 94305-2115 (United States)

    2008-10-01

    Silicic calderas are the surface expressions of silicic magma chambers, and thus their study may yield information about what tectonic and crustal features favor the generation of evolved magma. The goal of this study is to determine whether silicic calderas in arc settings are preferentially located behind the volcanic front. After a global analysis of young, arc-related calderas, we find that silicic calderas at continental margins do form over a wide area behind the front, as compared to other types of arc volcanoes.

  10. Automated Diatom Analysis Applied to Traditional Light Microscopy: A Proof-of-Concept Study

    Science.gov (United States)

    Little, Z. H. L.; Bishop, I.; Spaulding, S. A.; Nelson, H.; Mahoney, C.

    2017-12-01

    Diatom identification and enumeration by high resolution light microscopy is required for many areas of research and water quality assessment. Such analyses, however, are both expertise and labor-intensive. These challenges motivate the need for an automated process to efficiently and accurately identify and enumerate diatoms. Improvements in particle analysis software have increased the likelihood that diatom enumeration can be automated. VisualSpreadsheet software provides a possible solution for automated particle analysis of high-resolution light microscope diatom images. We applied the software, independent of its complementary FlowCam hardware, to automated analysis of light microscope images containing diatoms. Through numerous trials, we arrived at threshold settings to correctly segment 67% of the total possible diatom valves and fragments from broad fields of view. (183 light microscope images were examined containing 255 diatom particles. Of the 255 diatom particles present, 216 diatoms valves and fragments of valves were processed, with 170 properly analyzed and focused upon by the software). Manual analysis of the images yielded 255 particles in 400 seconds, whereas the software yielded a total of 216 particles in 68 seconds, thus highlighting that the software has an approximate five-fold efficiency advantage in particle analysis time. As in past efforts, incomplete or incorrect recognition was found for images with multiple valves in contact or valves with little contrast. The software has potential to be an effective tool in assisting taxonomists with diatom enumeration by completing a large portion of analyses. Benefits and limitations of the approach are presented to allow for development of future work in image analysis and automated enumeration of traditional light microscope images containing diatoms.

  11. All New Faces of Diatoms: Potential Source of Nanomaterials and Beyond

    Directory of Open Access Journals (Sweden)

    Meerambika Mishra

    2017-07-01

    Full Text Available Nature’s silicon marvel, the diatoms have lately astounded the scientific community with its intricate designs and lasting durability. Diatoms are a major group of phytoplanktons involved in the biogeochemical cycling of silica and are virtually inherent in every environment ranging from water to ice to soil. The usage of diatoms has proved prudently cost effective and its handling neither requires costly materials nor sophisticated instruments. Diatoms can easily be acquired from the environment, their culture requires ambient condition and does not involve any costly media or expensive instruments, besides, they can be transported in small quantities and proliferated to a desirable confluence from that scratch, thus are excellent cost effective industrial raw material. Naturally occurring diatom frustules are a source of nanomaterials. Their silica bio-shells have raised curiosity among nanotechnologists who hope that diatoms will facilitate tailoring minuscule structures which are beyond the capabilities of material scientists. Additionally, there is a colossal diversity in the dimensions of diatoms as the frustule shape differs from species to species; this provides a scope for the choice of a particular species of diatom to be tailored to an exacting requisite, thus paving the way to create desired three dimensional nanocomposites. The present article explores the use of diatoms in various arenas of science, may it be in nanotechnology, biotechnology, environmental science, biophysics or biochemistry and summarizes facets of diatom biology under one umbrella. Special emphasis has been given to biosilicification, biomineralization and use of diatoms as nanomaterials’, drug delivery vehicles, optical and immune-biosensors, filters, immunodiagnostics, aquaculture feeds, lab-on-a-chip, metabolites, and biofuels.

  12. Diatom species abundance and morphologically-based dissolution proxies in coastal Southern Ocean assemblages

    Science.gov (United States)

    Warnock, Jonathan P.; Scherer, Reed P.

    2015-07-01

    Taphonomic processes alter diatom assemblages in sediments, thus potentially negatively impacting paleoclimate records at various rates across space, time, and taxa. However, quantitative taphonomic data is rarely included in diatom-based paleoenvironmental reconstructions and no objective standard exists for comparing diatom dissolution in sediments recovered from marine depositional settings, including the Southern Ocean's opal belt. Furthermore, identifying changes to diatom dissolution through time can provide insight into the efficiency of both upper water column nutrient recycling and the biological pump. This is significant in that reactive metal proxies (e.g. Al, Ti) in the sediments only account for post-depositional dissolution, not the water column where the majority of dissolution occurs. In order to assess the range of variability of responses to dissolution in a typical Southern Ocean diatom community and provide a quantitative guideline for assessing taphonomic variability in diatoms recovered from core material, a sediment trap sample was subjected to controlled, serial dissolution. By evaluating dissolution-induced changes to diatom species' relative abundance, three preservational categories of diatoms have been identified: gracile, intermediate, and robust. The relative abundances of these categories can be used to establish a preservation grade for diatom assemblages. However, changes to the relative abundances of diatom species in sediment samples may reflect taphonomic or ecological factors. In order to address this complication, relative abundance changes have been tied to dissolution-induced morphological change to the areolae of Fragilariopsis curta, a significant sea-ice indicator in Southern Ocean sediments. This correlation allows differentiation between gracile species loss to dissolution versus ecological factors or sediment winnowing. These results mirror a similar morphological dissolution index from a parallel study utilizing

  13. Tip-induced nanoreactor for silicate

    Science.gov (United States)

    Gao, Ming; Ma, Liran; Liang, Yong; Gao, Yuan; Luo, Jianbin

    2015-09-01

    Nanoscale scientific issues have attracted an increasing amount of research interest due to their specific size-effect and novel structure-property. From macro to nano, materials present some unique chemical reactivity that bulk materials do not own. Here we introduce a facile method to generate silicate with nanoscale control based on the establishment of a confined space between a meso/nanoscale tungsten tip and a smooth silica/silicon substrate. During the process, local water-like droplets deposition can be obviously observed in the confinement between the Si/SiO2 surfaces and the KOH-modified tungsten tip. By the combination of in-situ optical microscopy and Raman spectroscopy, we were able to take a deep insight of both the product composition and the underlying mechanism of such phenomena. It was indicated that such nanoreactor for silicate could be quite efficient as a result of the local capillarity and electric field effect, with implications at both nano and meso scales.

  14. Thermochemistry of dense hydrous magnesium silicates

    Science.gov (United States)

    Bose, Kunal; Burnley, Pamela; Navrotsky, Alexandra

    1994-01-01

    Recent experimental investigations under mantle conditions have identified a suite of dense hydrous magnesium silicate (DHMS) phases that could be conduits to transport water to at least the 660 km discontinuity via mature, relatively cold, subducting slabs. Water released from successive dehydration of these phases during subduction could be responsible for deep focus earthquakes, mantle metasomatism and a host of other physico-chemical processes central to our understanding of the earth's deep interior. In order to construct a thermodynamic data base that can delineate and predict the stability ranges for DHMS phases, reliable thermochemical and thermophysical data are required. One of the major obstacles in calorimetric studies of phases synthesized under high pressure conditions has been limitation due to the small (less than 5 mg) sample mass. Our refinement of calorimeter techniques now allow precise determination of enthalpies of solution of less than 5 mg samples of hydrous magnesium silicates. For example, high temperature solution calorimetry of natural talc (Mg(0.99) Fe(0.01)Si4O10(OH)2), periclase (MgO) and quartz (SiO2) yield enthalpies of drop solution at 1044 K to be 592.2 (2.2), 52.01 (0.12) and 45.76 (0.4) kJ/mol respectively. The corresponding enthalpy of formation from oxides at 298 K for talc is minus 5908.2 kJ/mol agreeing within 0.1 percent to literature values.

  15. Evidence for seismogenic fracture of silicic magma.

    Science.gov (United States)

    Tuffen, Hugh; Smith, Rosanna; Sammonds, Peter R

    2008-05-22

    It has long been assumed that seismogenic faulting is confined to cool, brittle rocks, with a temperature upper limit of approximately 600 degrees C (ref. 1). This thinking underpins our understanding of volcanic earthquakes, which are assumed to occur in cold rocks surrounding moving magma. However, the recent discovery of abundant brittle-ductile fault textures in silicic lavas has led to the counter-intuitive hypothesis that seismic events may be triggered by fracture and faulting within the erupting magma itself. This hypothesis is supported by recent observations of growing lava domes, where microearthquake swarms have coincided with the emplacement of gouge-covered lava spines, leading to models of seismogenic stick-slip along shallow shear zones in the magma. But can fracturing or faulting in high-temperature, eruptible magma really generate measurable seismic events? Here we deform high-temperature silica-rich magmas under simulated volcanic conditions in order to test the hypothesis that high-temperature magma fracture is seismogenic. The acoustic emissions recorded during experiments show that seismogenic rupture may occur in both crystal-rich and crystal-free silicic magmas at eruptive temperatures, extending the range of known conditions for seismogenic faulting.

  16. Diatom Communities and Metrics as Indicators of Urbanization Effects on Streams and Potential Moderation by Landscape Green Infrastructure

    Science.gov (United States)

    Diatoms are very useful and important indicators of anthropogenic impacts on streams because they are the foundation of primary production and are responsive to nutrients, conductivity, and habitat conditions. We characterized relationships of diatom assemblages with water chemis...

  17. Growth inhibition of fouling bacteria and diatoms by extract of terrestrial plant, @iDerris scandens@@ (Dicotyledonae:Leguminocae)

    Digital Repository Service at National Institute of Oceanography (India)

    Sawant, S.S.; Sonak, S.; Garg, A.

    Methanol extract of terrestrial plant, @iDerris scandens@@ Benth, was found to inhibit growth of four diatoms and 7 bacterial species of fouling community. The concentrations required to bring about 100% inhibition of growth of the diatoms ranged...

  18. Growth inhibition of fouling bacteria and diatoms by extract of terrestrial plant, Derris scandens (Dicotyledonae:Leguminocae)

    Digital Repository Service at National Institute of Oceanography (India)

    Sawant, S.S.; Sonak, S.; Garg, A.

    Methanol extract of terrestrial plant, Derris scandens Benth, was found to inhibit growth of four diatoms and 7 bacterial species of fouling community. The concentrations required to bring about 100% inhibition of growth of the diatoms ranged...

  19. Action Spectrum of Photoinhibition in the Diatom Phaeodactylum tricornutum.

    Science.gov (United States)

    Havurinne, Vesa; Tyystjärvi, Esa

    2017-12-01

    Light-dependent electron transfer is necessary for photosynthesis, but light also damages PSII. Light-induced damage to PSII is called photoinhibition, and the damaging reactions of photoinhibition are still under debate. Diatoms possess an exotic combination of light-harvesting pigments, Chls a/c and fucoxanthin, making them an interesting platform for studying the photoreceptors of photoinhibition. We first confirmed the direct proportionality of photoinhibition to the photon flux density of incident light in the diatom Phaeodactylum tricornutum. Phaeodactylum is known for its efficient non-photochemical quenching, and the effect of this photoprotective mechanism on photoinhibition was tested. Photoinhibition proceeded essentially at the same rate in blue-light-grown Phaeodactylum cells that are capable of non-photochemical quenching and in red-light-grown, non-photochemical quenching-deficient cells. To obtain more insight into how the pigment composition of diatoms affects photoinhibition, we measured the action spectrum of photoinhibition in Phaeodactylum. In visible light, the action spectrum resembled the absorption spectrum of Phaeodactylum, and UV radiation caused much more photoinhibition than visible light. Comparison of the action spectrum of photoinhibition with the absorption spectrum and the excitation spectrum of 77 K PSII fluorescence emission confirmed that photosynthetic pigments are involved in photoinhibition, but the photoinhibitory efficiency of red light is weak, suggesting that the role of light-harvesting pigments as light receptors of photoinhibition is secondary. Finally, we compared photoinhibition in Phaeodactylum with that in other photosynthetic organisms, and our data indicate that the PSII reaction centers of Phaeodactylum are not particularly well protected against the primary damage of photoinhibition. © The Author 2017. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights

  20. Optimizing CRISPR/Cas9 for the Diatom Phaeodactylum tricornutum

    Directory of Open Access Journals (Sweden)

    Daniel Stukenberg

    2018-06-01

    Full Text Available CRISPR/Cas9 is a powerful tool for genome editing. We constructed an easy-to-handle expression vector for application in the model organism Phaeodactylum tricornutum and tested its capabilities in order to apply CRISPR/Cas9 technology for our purpose. In our experiments, we targeted two different genes, screened for mutations and analyzed mutated diatoms in a three-step process. In the end, we identified cells, showing either monoallelic or homo-biallelic targeted mutations. Thus, we confirm that application of the CRISPR/Cas9 system for P. tricornutum is very promising, although, as discussed, overlooked pitfalls have to be considered.

  1. Seasonal effects of cadmium accumulation in periphytic diatom communities of freshwater biofilms

    International Nuclear Information System (INIS)

    Thi Thuy Duong; Morin, Soizic; Herlory, Olivier; Feurtet-Mazel, Agnes; Coste, Michel; Boudou, Alain

    2008-01-01

    The relationships between diatom species and cadmium (Cd) accumulated in biofilms of the Riou-Mort River (SW, France) were studied in July 2004 and March 2005. Biofilms were sampled from artificial substrates immersed along a metallic pollution gradient during 20 days. Dynamics of diatom communities and cadmium accumulation were followed by collecting samples after 4, 7, 14 and 20 days of biofilm colonization. Cd accumulation in biofilms during experiment was significantly higher in Cd polluted station (Joanis) than in reference station (Firmi) for both seasons. Periphytic diatom composition varied between sites and seasons. At Firmi station, seasonal dynamics of diatom communities were stable with the dominance of Cyclotella meneghiniana and Melosira varians in July and Surirellabrebissonnii and Navicula gregaria in March. At Joanis station, diatom communities mainly responded to high levels of metal by a high proportion of small, adnate species. Positive correlations between Eolimna minima, Nitzschia palea, Encyonema minutum, Surirella angusta, and Gomphonema parvulum and cadmium accumulation were observed, indicating that these species are tolerant to high levels of cadmium. On the other hand, negative correlations of C. meneghiniana, N. gregaria, Navicula lanceolata, M. varians and Nitzschia dissipata with cadmium qualify them as sensitive diatom species. Periphytic diatom composition through the presence of specific species highlight metal tolerant indicator diatom groups which will be meaningful for biomonitoring pollution in natural aquatic systems

  2. The influence of land use on water quality and diatom community ...

    African Journals Online (AJOL)

    Epilithic diatom communities offer a holistic and integrated approach for assessing water quality as they remain in one place for a number of months and reflect an ecological memory of water quality over a period of time. The objective of this study is to use diatom assemblages to distinguish between particular land types ...

  3. Grazer-induced transcriptomic and metabolomic response of the chain-forming diatom Skeletonema marinoi

    DEFF Research Database (Denmark)

    Amato, Alberto; Sabatino, Valeria; Nylund, Göran M.

    2018-01-01

    Diatoms and copepods are main actors in marine food webs. The prey-predator interactions between them affect bloom dynamics, shape marine ecosystems and impact the energy transfer to higher trophic levels. Recently it has been demonstrated that the presence of grazers may affect the diatom prey b...

  4. Rotation-vibrational spectra of diatomic molecules and nuclei with Davidson interactions

    CERN Document Server

    Rowe, D J

    1998-01-01

    Complete rotation-vibrational spectra and electromagnetic transition rates are obtained for Hamiltonians of diatomic molecules and nuclei with Davidson interactions. Analytical results are derived by dynamical symmetry methods for diatomic molecules and a liquid-drop model of the nucleus. Numerical solutions are obtained for a many-particle nucleus with quadrupole Davidson interactions within the framework of the microscopic symplectic model. (author)

  5. Influence of land-use patterns on benthic diatom communities and ...

    African Journals Online (AJOL)

    The objective of this study was to determine the effects of land-use patterns on both diatom community composition and water quality in tropical streams during the dry season. Benthic diatom collections and water quality sampling were done 4 times at 10 sites. A suite of environmental variables that varied with human ...

  6. A stress surveillance system based on calcium and nitric oxide in marine diatoms

    NARCIS (Netherlands)

    Vardi, A.; Formiggini, F.; Casotti, R.; De Martino, A.; Ribalet, F.; Miralto, A.; Bowler, C.

    2006-01-01

    Diatoms are an important group of eukaryotic phytoplankton, responsible for about 20% of global primary productivity. Study of the functional role of chemical signaling within phytoplankton assemblages is still in its infancy although recent reports in diatoms suggest the existence of chemical-based

  7. A stress surveillance system based on calcium and nitric oxide in marine diatoms.

    NARCIS (Netherlands)

    Vardi, A.; Formiggini, F.; Casotti, R.; De Martino, A.; Ribalet, F.; Miralto, A.; Bowler, C.

    2006-01-01

    Diatoms are an important group of eukaryotic phytoplankton, responsible for about 20% of global primary productivity. Study of the functional role of chemical signaling within phytoplankton assemblages is still in its infancy although recent reports in diatoms suggest the existence of chemical-based

  8. Contribution to the Study of the flora diatomic Nahr Yahfufah (Lebanon)

    International Nuclear Information System (INIS)

    SLIM, K.; ALOUF, N.

    1984-01-01

    Contribution to the study of Diatomic flora on Nahr Yahfufah Lebanon. From October 1980 to June 1982 a hydrobiologic study has taken place on the river of Yahfufah situated to the west of anti Lebanon. From the diatomic population 52 species and varieties were designated. Further more the physico-chemical parameters were followed and studied. (author).

  9. Adaptive significance of phytoplankton stickiness with emphasis on the diatom Skeletonema costatum

    DEFF Research Database (Denmark)

    Hansen, J.L.S.; Timm, U.; Kiørboe, Thomas

    1995-01-01

    Diatom aggregate formation was analyzed using coagulation theory. Population dynamics models show that coagulation has an important impact on species succession during diatom blooms. When different species collide and form mixed aggregates this process causes interspecific interference competitio...... was tested on field data, and the predicted dynamics of a spring bloom was very similar to that observed...

  10. Impact of marine influence and cultivation on the diatom flora of ...

    African Journals Online (AJOL)

    During a limnological and palaeolimnological study of the western part of the Great Coast of Senegal, an analysis of diatoms was carried out in Thiaroye Pond in the suburbs of Dakar. Current diatom flora in the water and on floating plants, and subfossil flora in two cores were sampled in 1996 and 2003. A total of 104 ...

  11. Seasonal effects of cadmium accumulation in periphytic diatom communities of freshwater biofilms

    Energy Technology Data Exchange (ETDEWEB)

    Thi Thuy Duong [Institute of Environmental Technology, Vietnamese Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi (Viet Nam); Universite de Bordeaux 1, CNRS, UMR 5805 EPOC, Place du Dr Peyneau, 33120 Arcachon (France)], E-mail: duongthuy0712@yahoo.com; Morin, Soizic [Cemagref, UR REBX, 50 avenue de Verdun, F-33612 Cestas cedex (France); Herlory, Olivier [Universite de Bordeaux 1, CNRS, UMR 5805 EPOC, Place du Dr Peyneau, 33120 Arcachon (France); Feurtet-Mazel, Agnes [Universite de Bordeaux 1, CNRS, UMR 5805 EPOC, Place du Dr Peyneau, 33120 Arcachon (France)], E-mail: a.feurtet-mazel@epoc.u-bordeaux1.fr; Coste, Michel [Cemagref, UR REBX, 50 avenue de Verdun, F-33612 Cestas cedex (France); Boudou, Alain [Universite de Bordeaux 1, CNRS, UMR 5805 EPOC, Place du Dr Peyneau, 33120 Arcachon (France)

    2008-10-20

    The relationships between diatom species and cadmium (Cd) accumulated in biofilms of the Riou-Mort River (SW, France) were studied in July 2004 and March 2005. Biofilms were sampled from artificial substrates immersed along a metallic pollution gradient during 20 days. Dynamics of diatom communities and cadmium accumulation were followed by collecting samples after 4, 7, 14 and 20 days of biofilm colonization. Cd accumulation in biofilms during experiment was significantly higher in Cd polluted station (Joanis) than in reference station (Firmi) for both seasons. Periphytic diatom composition varied between sites and seasons. At Firmi station, seasonal dynamics of diatom communities were stable with the dominance of Cyclotella meneghiniana and Melosira varians in July and Surirellabrebissonnii and Navicula gregaria in March. At Joanis station, diatom communities mainly responded to high levels of metal by a high proportion of small, adnate species. Positive correlations between Eolimna minima, Nitzschia palea, Encyonema minutum, Surirella angusta, and Gomphonema parvulum and cadmium accumulation were observed, indicating that these species are tolerant to high levels of cadmium. On the other hand, negative correlations of C. meneghiniana, N. gregaria, Navicula lanceolata, M. varians and Nitzschia dissipata with cadmium qualify them as sensitive diatom species. Periphytic diatom composition through the presence of specific species highlight metal tolerant indicator diatom groups which will be meaningful for biomonitoring pollution in natural aquatic systems.

  12. Paleoceanographic, and paleoclimatic constraints on the global Eocene diatom and silicoflagellate record

    Science.gov (United States)

    Barron, John A.; Stickley, Catherine E.; Bukry, David

    2015-01-01

    Eocene diatom and silicoflagellate biostratigraphy are summarized and correlated with the most recent geologic time scale as well as with the global oxygen isotope and eustatic sea level curves. The global distribution of Eocene diatom/silicoflagellate-bearing sediments varies considerably, reflecting changing oceanic gateways and paleoceanography with changing patterns that are punctuated by four major depositional events.

  13. An integrated analysis of molecular acclimation to high light in the marine diatom Phaeodactylum tricornutum

    DEFF Research Database (Denmark)

    Nymark, Marianne; Valle, Kristin C; Brembu, Tore

    2009-01-01

    Photosynthetic diatoms are exposed to rapid and unpredictable changes in irradiance and spectral quality, and must be able to acclimate their light harvesting systems to varying light conditions. Molecular mechanisms behind light acclimation in diatoms are largely unknown. We set out to investiga...

  14. Diatoms as water quality indicators in the upper reaches of the Great ...

    African Journals Online (AJOL)

    All index scores showed the Great Fish River to be impacted, and showed significant correlations of diatom species abundance with pH, NO3-N, electrical conductivity, NH4-N and CaCO3. Analysis revealed EC and NO3-N as the main environmental drivers affecting diatom commnity composition, followed by pH and ...

  15. Spectral properties of porphyrins in the systems with layered silicates

    International Nuclear Information System (INIS)

    Ceklovsky, A.

    2009-03-01

    This work is focused on investigation of hybrid materials based on layered silicates, representing host inorganic component, and porphyrin dyes as organic guest. Aqueous colloidal dispersions, as well as thin solid films of layered silicate/porphyrin systems were studied. Modification of photophysical properties, such as absorption and fluorescence of molecules, adsorbed or incorporated in layered silicate hosts, were studied mainly to spread the knowledge about the environments suitable for incorporating aromatic compounds, providing photoactive properties of potential technological interest. TMPyP cations interact with the surfaces of layered silicates via electrostatic interactions. The extent of dye adsorption on colloidal particles of the silicates is influenced by the CEC values and swelling ability of silicates. Interaction of porphyrins with layered silicate hosts leads to significant changes of dye spectral properties. One of the key parameters that has a crucial impact on this interaction is the layer charge of silicate template. Other factors influence the resulting spectral properties of hybrid systems, such as the method of hybrid material preparation, the material's type (colloid, film), and the modification of the silicate host. Molecular orientation studies using linearly-polarized spectroscopies in VIS and IR regions revealed that TMPyP molecules were oriented in almost parallel fashion with respect to the silicate surface plane. Slightly higher values of the orientation angle of TMPyP transition moment were observed for the TMPyP/FHT system. Thus, flattening of the guest TMPyP molecules is the next important factor (mainly in the systems with lower layer charge), influencing its spectral properties upon the interaction with layered silicates. Fluorescence was effectively quenched in the systems based on solid films prepared from the high concentration of the dye (10-3 mol.dm-3). The quenching is most probably related to the structure of the

  16. Intensive aggregate formation with low vertical flux during an upwelling-induced diatom bloom

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Tiselius, P.; Mitchell-Innes, B.

    1998-01-01

    of turbulent shear in the ocean such stickiness coefficients predict very high specific coagulation rates (0.3 d(-1)). In situ video observation demonstrated the occurrence of abundant diatom aggregates with surface water concentrations between 1,000 and 3,000 ppm. Despite the very high concentration......The surfaces of most pelagic diatoms are sticky at times and may therefore form rapidly settling aggregates by physical coagulation. Stickiness and aggregate formation may be particularly adaptive in upwelling systems by allowing the retention of diatom populations in the vicinity of the upwelling...... center. We therefore hypothesized that upwelling diatom blooms are terminated by aggregate formation and rapid sedimentation. We monitored the development of a maturing diatom (mainly Chaetoceros spp.) bloom in the Benguela upwelling current during 7 d in February. Chlorophyll concentrations remained...

  17. Growth of fouling diatoms from the Zuari estuary, Goa (west coast of India) under different salinities in the laboratory

    Digital Repository Service at National Institute of Oceanography (India)

    Redekar, P.D.; Wagh, A.B.

    Diatoms take part in the initial process of fouling i.e. primary film formation. In order to understand the growth of the diatoms under different salinity conditions in the laboratory, this work was undertaken. Fouling diatoms on glass slides were...

  18. A caveat regarding diatom-inferred nitrogen concentrations in oligotrophic lakes

    Science.gov (United States)

    Arnett, Heather A.; Saros, Jasmine E.; Mast, M. Alisa

    2012-01-01

    Atmospheric deposition of reactive nitrogen (Nr) has enriched oligotrophic lakes with nitrogen (N) in many regions of the world and elicited dramatic changes in diatom community structure. The lakewater concentrations of nitrate that cause these community changes remain unclear, raising interest in the development of diatom-based transfer functions to infer nitrate. We developed a diatom calibration set using surface sediment samples from 46 high-elevation lakes across the Rocky Mountains of the western US, a region spanning an N deposition gradient from very low to moderate levels (phosphorus, and hypolimnetic water temperature were related to diatom distributions. A transfer function was developed for nitrate and applied to a sedimentary diatom profile from Heart Lake in the central Rockies. The model coefficient of determination (bootstrapping validation) of 0.61 suggested potential for diatom-inferred reconstructions of lakewater nitrate concentrations over time, but a comparison of observed versus diatom-inferred nitrate values revealed the poor performance of this model at low nitrate concentrations. Resource physiology experiments revealed that nitrogen requirements of two key taxa were opposite to nitrate optima defined in the transfer function. Our data set reveals two underlying ecological constraints that impede the development of nitrate transfer functions in oligotrophic lakes: (1) even in lakes with nitrate concentrations below quantification (<1 μg L−1), diatom assemblages were already dominated by species indicative of moderate N enrichment; (2) N-limited oligotrophic lakes switch to P limitation after receiving only modest inputs of reactive N, shifting the controls on diatom species changes along the length of the nitrate gradient. These constraints suggest that quantitative inferences of nitrate from diatom assemblages will likely require experimental approaches.

  19. In vivo exposure to northern diatoms arrests sea urchin embryonic development.

    Science.gov (United States)

    Gudimova, Elena; Eilertsen, Hans C; Jørgensen, Trond Ø; Hansen, Espen

    2016-01-01

    There are numerous reports indicating that marine diatoms may act harmful to early developmental stages of invertebrates. It is believed that the compounds responsible for these detrimental effects are oxylipins resulting from oxidized polyunsaturated fatty acids, and that they may function as grazing deterrents. Most studies reporting these effects have exposed test organisms to diatom extracts or purified toxins, but data from in vivo exposure to intact diatoms are scarce. We have conducted sea urchin egg incubation and plutei feeding experiments to test if intact diatom cells affected sea urchin embryo development and survival. This was done by exposing the common northern sea urchins Strongylocentrotus droebachiensis and Echinus acutus to northern strains of the diatoms Chaetoceros socialis, Skeletonema marinoi, Chaetoceros furcellatus, Attheya longicornis, Thalassiosira gravida and Porosira glacialis. The intact diatom cell suspensions were found to inhibit sea urchin egg hatching and embryogenesis. S. marinoi was the most potent one as it caused acute mortality in S. droebachiensis eggs after only four hours exposure to high (50 μg/L Chla) diatom concentrations, as well as 24 h exposure to normal (20 μg/L Chla) and high diatom concentrations. The second most potent species was T. gravida that caused acute mortality after 24 h exposure to both diatom concentrations. A. longicornis was the least harmful of the diatom species in terms of embryo development arrestment, and it was the species that was most actively ingested by S. droebachiensis plutei. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  20. Stress-corrosion mechanisms in silicate glasses

    International Nuclear Information System (INIS)

    Ciccotti, Matteo

    2009-01-01

    The present review is intended to revisit the advances and debates in the comprehension of the mechanisms of subcritical crack propagation in silicate glasses almost a century after its initial developments. Glass has inspired the initial insights of Griffith into the origin of brittleness and the ensuing development of modern fracture mechanics. Yet, through the decades the real nature of the fundamental mechanisms of crack propagation in glass has escaped a clear comprehension which could gather general agreement on subtle problems such as the role of plasticity, the role of the glass composition, the environmental condition at the crack tip and its relation to the complex mechanisms of corrosion and leaching. The different processes are analysed here with a special focus on their relevant space and time scales in order to question their domain of action and their contribution in both the kinetic laws and the energetic aspects.

  1. Cesium titanium silicate and method of making

    Science.gov (United States)

    Balmer, Mari L.

    1997-01-01

    The invention is the new material, a ternary compound of cesium, silica, and titania, together with a method of making the ternary compound, cesium titanium silicate pollucite. More specifically, the invention is Cs.sub.2 Ti.sub.2 Si.sub.4 O.sub.13 pollucite which is a new crystalline phase representing a novel class of Ti-containing zeolites. Compositions contain relatively high Cs.sub.2 O and TiO.sub.2 loadings and are durable glass and ceramic materials. The amount of TiO.sub.2 and Cs.sub.2 that can be incorporated into these glasses and crystalline ceramics far exceeds the limits set for the borosilicate high level waste glass.

  2. Radiation effects on lead silicate glass surfaces

    International Nuclear Information System (INIS)

    Wang, P.W.; Zhang, L.P.; Borgen, N.; Pannell, K.

    1996-01-01

    Radiation-induced changes in the microstructure of lead silicate glass were investigated in situ under Mg K α irradiation in an ultra-high vacuum (UHV) environment by X-ray photoelectron spectroscopy (XPS). Lead-oxygen bond breaking resulting in the formation of pure lead was observed. The segregation, growth kinetics and the structural relaxation of the lead, with corresponding changes in the oxygen and silicon on the glass surfaces were studied by measuring the time-dependent changes in concentration, binding energy shifts, and the full width at half maximum. A bimodal distribution of the oxygen XPS signal, caused by bridging and non-bridging oxygens, was found during the relaxation process. All experimental data indicate a reduction of the oxygen concentration, a phase separation of the lead from the glass matrix, and the metallization of the lead occurred during and after the X-ray irradiation. (author)

  3. Symmetries and rotational line intensities in diatomic molecules

    International Nuclear Information System (INIS)

    Veseth, L.

    1986-02-01

    The general theory of angular momenta and the full rotation group is used to reconsider the theory of the intensity factors of rotational lines in the spectra of diatomic molecules (Hoenl-London factors). It is shown that the use of the rotational symmetry (rotation matrices) leads to compact derivations of the symmetry properties of the molecular wave functions, as well as the matrix elements of the transitions operator. The present work is restricted to spin-allowed electric dipole transitions, and the general sum rule characteristic of this type of transitions is rederived by use of the general angular momentum theory. A main purpose of the present work has been to provide a unified theoretical basis for exact numerical computations of Hoenl-London factors for all types of spin-allowed electric dipole transitions in diatomic molecules. The computed Hoenl-London factors are then in the next step intended to be the basis for construction of synthetic molecular band spectra, with particular applications to upper atmosperic emissions (aurora)

  4. Toxic Diatom Aldehydes Affect Defence Gene Networks in Sea Urchins.

    Directory of Open Access Journals (Sweden)

    Stefano Varrella

    Full Text Available Marine organisms possess a series of cellular strategies to counteract the negative effects of toxic compounds, including the massive reorganization of gene expression networks. Here we report the modulated dose-dependent response of activated genes by diatom polyunsaturated aldehydes (PUAs in the sea urchin Paracentrotus lividus. PUAs are secondary metabolites deriving from the oxidation of fatty acids, inducing deleterious effects on the reproduction and development of planktonic and benthic organisms that feed on these unicellular algae and with anti-cancer activity. Our previous results showed that PUAs target several genes, implicated in different functional processes in this sea urchin. Using interactomic Ingenuity Pathway Analysis we now show that the genes targeted by PUAs are correlated with four HUB genes, NF-κB, p53, δ-2-catenin and HIF1A, which have not been previously reported for P. lividus. We propose a working model describing hypothetical pathways potentially involved in toxic aldehyde stress response in sea urchins. This represents the first report on gene networks affected by PUAs, opening new perspectives in understanding the cellular mechanisms underlying the response of benthic organisms to diatom exposure.

  5. Diatom diversity in chronically versus episodically acidified adirondack streams

    Science.gov (United States)

    Passy, S.I.; Ciugulea, I.; Lawrence, G.B.

    2006-01-01

    The relationship between algal species richness and diversity, and pH is controversial. Furthermore, it is still unknown how episodic stream acidification following atmospheric deposition affects species richness and diversity. Here we analyzed water chemistry and diatom epiphyton dynamics and showed their contrasting behavior in chronically vs. episodically acidic streams in the Adirondack region. Species richness and diversity were significantly higher in the chronically acidic brown water stream, where organic acidity was significantly higher and the ratio of inorganic to organic monomeric aluminum significantly lower. Conversely, in the episodically acidic clear water stream, the inorganic acidity and pH were significantly higher and the diatom communities were very species-poor. This suggests that episodic acidification in the Adirondacks may be more stressful for stream biota than chronic acidity. Strong negative linear relationships between species diversity, Eunotia exigua, and dissolved organic carbon against pH were revealed after the influence of non-linear temporal trends was partialled out using a novel way of temporal modeling. ?? 2006 WILEY-VCH Verlag GmbH & Co. KGaA.

  6. Study on the excited diatomic molecules of rare gas

    International Nuclear Information System (INIS)

    Kasama, Kunihiko; Arai, Shigeyoshi

    1981-01-01

    The study on the excited diatomic molecules of rare gas is presented. The absorption spectra, the mechanism of formation and attenuation and the reactions with other molecules are described. The excitation of rare gas was made by using a pulsed electron beam generator. The absorption of excited diatomic molecules was measured as the functions of time. Two absorption peaks were observed. The electron states of rare gases were estimated. The observed and calculated transition values were given for each peak. The absorption spectra of Ne change with time. The spectra of Ar do not change with time. Four and eleven absorption maxima were seen in the spectra of Kr and Xe, respectively. In the case of Ar, the thermal equilibrium existed. The constants of the production and attenuation rates were obtained as the functions of Ar gas pressure. In the case of Ne, there wad definitely the time dependence of absorption spectra. The attenuation constant was obtained for each transition between various vibration levels. It is necessary to consider the relaxation from high vibrational levels. The energy transfer between vibrational levels hardly occurred in Ne because the intervals are large. When there are other molecules, the attnuation was accelerated. (Kato, T.)

  7. Redox kinetics and mechanism in silicate melts

    International Nuclear Information System (INIS)

    Cochain, B.

    2009-12-01

    This work contributes to better understand iron redox reactions and mechanisms in silicate melts. It was conducted on compositions in both Na 2 O-B 2 O 3 -SiO 2 -FeO and Na 2 O-Al 2 O 3 -SiO 2 -FeO systems. The influence of boron-sodium and aluminum-sodium substitutions and iron content on properties and structure of glasses and on the iron redox kinetics has been studied by Raman, Moessbauer and XANES spectroscopies at the B and Fe K-edges. In borosilicate glasses, an increase in iron content or in the Fe 3+ /ΣFe redox state implies a structural rearrangement of the BO 4 species in the glass network whereas the BO 3 and BO 4 relative proportions remain nearly constant. In all studied glasses and melts, Fe 3+ is a network former in tetrahedral coordination, unless for aluminosilicates of ratio Al/Na≥1 where Fe 3+ is a network modifier in five-fold coordination. Near Tg, diffusion of network modifying cations controls the iron redox kinetics along with a flux of electron holes. At liquidus temperatures, oxygen diffusion is considered to be the mechanism that governs redox reactions. This study shows the role played by the silicate network polymerization on the redox kinetics. In borosilicate melts, iron redox kinetics depends on the boron speciation between BO 3 and BO 4 that depends itself on the sodium content. Furthermore, an increase in the network-former/network-modifier ratio implies a decrease in oxygen diffusion that results in a slowing down of the redox kinetics. The obtained results allow a description of the iron redox kinetics for more complex compositions as natural lavas or nuclear waste model glasses. (author)

  8. Processing and characterization of diatom nanoparticles and microparticles as potential source of silicon for bone tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    Le, Thi Duy Hanh [Department of Industrial Engineering, University of Trento, Trento (Italy); BIOtech Research Center and European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Trento (Italy); Bonani, Walter [Department of Industrial Engineering, University of Trento, Trento (Italy); BIOtech Research Center and European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Trento (Italy); Interuniversity Consortium for Science and Technology of Materials, Trento Research Unit, Trento (Italy); Speranza, Giorgio [Center for Materials and Microsystems, PAM-SE, Fondazione Bruno Kessler, Trento (Italy); Sglavo, Vincenzo; Ceccato, Riccardo [Department of Industrial Engineering, University of Trento, Trento (Italy); Maniglio, Devid; Motta, Antonella [Department of Industrial Engineering, University of Trento, Trento (Italy); BIOtech Research Center and European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Trento (Italy); Interuniversity Consortium for Science and Technology of Materials, Trento Research Unit, Trento (Italy); Migliaresi, Claudio, E-mail: claudio.migliaresi@unitn.it [Department of Industrial Engineering, University of Trento, Trento (Italy); BIOtech Research Center and European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Trento (Italy); Interuniversity Consortium for Science and Technology of Materials, Trento Research Unit, Trento (Italy)

    2016-02-01

    Silicon plays an important role in bone formation and maintenance, improving osteoblast cell function and inducing mineralization. Often, bone deformation and long bone abnormalities have been associated with silica/silicon deficiency. Diatomite, a natural deposit of diatom skeleton, is a cheap and abundant source of biogenic silica. The aim of the present study is to validate the potential of diatom particles derived from diatom skeletons as silicon-donor materials for bone tissue engineering applications. Raw diatomite (RD) and calcined diatomite (CD) powders were purified by acid treatments, and diatom microparticles (MPs) and nanoparticles (NPs) were produced by fragmentation of purified diatoms under alkaline conditions. The influence of processing on the surface chemical composition of purified diatomites was evaluated by X-ray photoelectron spectroscopy (XPS). Diatoms NPs were also characterized in terms of morphology and size distribution by transmission electron microscopy (TEM) and Dynamic light scattering (DLS), while diatom MPs morphology was analyzed by scanning electron microscopy (SEM). Surface area and microporosity of the diatom particles were evaluated by nitrogen physisorption methods. Release of silicon ions from diatom-derived particles was demonstrated using inductively coupled plasma optical emission spectrometry (ICP/OES); furthermore, silicon release kinetic was found to be influenced by diatomite purification method and particle size. Diatom-derived microparticles (MPs) and nanoparticles (NPs) showed limited or no cytotoxic effect in vitro depending on the administration conditions. - Highlights: • Diatomite is a natural source of silica and has a potential as silicon-donor for bone regenerative applications. • Diatom particles derived from purified diatom skeletons were prepared by fragmentation under extreme alkaline condition. • Dissolution of diatom particles derived from diatom skeletons in DI water depend on purification method

  9. An improved coupled-states approximation including the nearest neighbor Coriolis couplings for diatom-diatom inelastic collision

    Science.gov (United States)

    Yang, Dongzheng; Hu, Xixi; Zhang, Dong H.; Xie, Daiqian

    2018-02-01

    Solving the time-independent close coupling equations of a diatom-diatom inelastic collision system by using the rigorous close-coupling approach is numerically difficult because of its expensive matrix manipulation. The coupled-states approximation decouples the centrifugal matrix by neglecting the important Coriolis couplings completely. In this work, a new approximation method based on the coupled-states approximation is presented and applied to time-independent quantum dynamic calculations. This approach only considers the most important Coriolis coupling with the nearest neighbors and ignores weaker Coriolis couplings with farther K channels. As a result, it reduces the computational costs without a significant loss of accuracy. Numerical tests for para-H2+ortho-H2 and para-H2+HD inelastic collision were carried out and the results showed that the improved method dramatically reduces the errors due to the neglect of the Coriolis couplings in the coupled-states approximation. This strategy should be useful in quantum dynamics of other systems.

  10. Lattice thermal conductivity of silicate glasses at high pressures

    Science.gov (United States)

    Chang, Y. Y.; Hsieh, W. P.

    2016-12-01

    Knowledge of the thermodynamic and transport properties of magma holds the key to understanding the thermal evolution and chemical differentiation of Earth. The discovery of the remnant of a deep magma ocean above the core mantle boundary (CMB) from seismic observations suggest that the CMB heat flux would strongly depend on the thermal conductivity, including lattice (klat) and radiative (krad) components, of dense silicate melts and major constituent minerals around the region. Recent measurements on the krad of dense silicate glasses and lower-mantle minerals show that krad of dense silicate glasses could be significantly smaller than krad of the surrounding solid mantle phases, and therefore the dense silicate melts would act as a thermal insulator in deep lower mantle. This conclusion, however, remains uncertain due to the lack of direct measurements on the lattice thermal conductivity of silicate melts under relevant pressure-temperature conditions. Besides the CMB, magmas exist in different circumstances beneath the surface of the Earth. Chemical compositions of silicate melts vary with geological and geodynamic settings of the melts and have strong influences on their thermal properties. In order to have a better view of heat transport within the Earth, it is important to study compositional and pressure dependences of thermal properties of silicate melts. Here we report experimental results on lattice thermal conductivities of silicate glasses with basaltic and rhyolitic compositions up to Earth's lower mantle pressures using time-domain thermoreflectance coupled with diamond-anvil cell techniques. This study not only provides new data for the thermal conductivity of silicate melts in the Earth's deep interior, but is crucial for further understanding of the evolution of Earth's complex internal structure.

  11. What if the Diatoms of the Deep Chlorophyll Maximum Can Ascend?

    Science.gov (United States)

    Villareal, T. A.

    2016-02-01

    Buoyancy regulation is an integral part of diatom ecology via its role in sinking rates and is fundamental to understanding their distribution and abundance. Numerous studies have documented the effects of size and nutrition on sinking rates. Many pelagic diatoms have low intrinsic sinking rates when healthy and nutrient-replete (deep chlorophyll maximum. The potential for ascending behavior adds an additional layer of complexity by allowing both active depth regulation similar to that observed in flagellated taxa and upward transport by some fraction of deep euphotic zone diatom blooms supported by nutrient injection. In this talk, I review the data documenting positive buoyancy in small diatoms, offer direct visual evidence of ascending behavior in common diatoms typical of both oceanic and coastal zones, and note the characteristics of sinking rate distributions within a single species. Buoyancy control leads to bidirectional movement at similar rates across a wide size spectrum of diatoms although the frequency of ascending behavior may be only a small portion of the individual species' abundance. While much remains to be learned, the paradigm of unidirectional downward movement by diatoms is both inaccurate and an oversimplification.

  12. Diatoms dominate the eukaryotic metatranscriptome during spring in coastal 'dead zone' sediments.

    Science.gov (United States)

    Broman, Elias; Sachpazidou, Varvara; Dopson, Mark; Hylander, Samuel

    2017-10-11

    An important characteristic of marine sediments is the oxygen concentration that affects many central metabolic processes. There has been a widespread increase in hypoxia in coastal systems (referred to as 'dead zones') mainly caused by eutrophication. Hence, it is central to understand the metabolism and ecology of eukaryotic life in sediments during changing oxygen conditions. Therefore, we sampled coastal 'dead zone' Baltic Sea sediment during autumn and spring, and analysed the eukaryotic metatranscriptome from field samples and after incubation in the dark under oxic or anoxic conditions. Bacillariophyta (diatoms) dominated the eukaryotic metatranscriptome in spring and were also abundant during autumn. A large fraction of the diatom RNA reads was associated with the photosystems suggesting a constitutive expression in darkness. Microscope observation showed intact diatom cells and these would, if hatched, represent a significant part of the pelagic phytoplankton biomass. Oxygenation did not significantly change the relative proportion of diatoms nor resulted in any major shifts in metabolic 'signatures'. By contrast, diatoms rapidly responded when exposed to light suggesting that light is limiting diatom development in hypoxic sediments. Hence, it is suggested that diatoms in hypoxic sediments are on 'standby' to exploit the environment if they reach suitable habitats. © 2017 The Author(s).

  13. Seasonal and daily fluctuation of diatoms during spring tide periods in Kerkennah Islands

    Directory of Open Access Journals (Sweden)

    Mounir Ben brahim

    2015-06-01

    Full Text Available Objective: To study seasonal and the daily distribution of diatoms in the three tidal periods (flood, slack and ebb period during the spring tide. Methods: Water samples were taken and environmental variables were measured three times in each tidal period during 10 days of spring tide. Sampling was done in 2007 in Cercina station located in the western coast of Kerkennah (34°41'27'' N; 11°07'45'' E (Southern Tunisia. Results: Nutrients showed significant variation between seasons, increasing in spring and decreasing noticeably in autumn and winter. About 36 diatom species were found. Results revealed a remarkable abundance increase in spring and summer. Irregular differences in diatom abundances were revealed over the tidal periods, with the highest rates being detected during the flood and the ebb period, while the abundance rate was lowest during the slack period. This could presumably be attributed to the increase of nutrient supply of suspended particulate matter during water motion. The results revealed a correlation between diatom abundance and temperature, NO2 - , NO3 - , Si(OH4 and PO4 3 . Temperature seemed to be the most important factors which may influence the distribution and diatom abundance. Conclusions: Tide has various effects on the nutrients status and diatoms community (in terms of species composition, succession and abundance between different tidal periods. Fluctuation of diatoms was correlated with changes in the circulation of water bodies and changes in nutrient regime.

  14. Review--Interactions between diatoms and stainless steel: focus on biofouling and biocorrosion.

    Science.gov (United States)

    Landoulsi, J; Cooksey, K E; Dupres, V

    2011-11-01

    There is a considerable body of information regarding bacterially enhanced corrosion, however, this review focuses on diatoms (unicellular algae) whose contribution to biocorrosion is less well studied. The reasons why diatoms have been neglected in studies of biocorrosion in natural waters are discussed and the question whether diatoms should be considered as inert with respect of electrochemical processes is considered. A particular focus is given to the case of stainless steels (SS), which are widely used in variety of applications in natural waters. Basic information on the cell biology of diatoms is included in the review, particularly with respect to their ability to 'sense' and adhere to surfaces. Investigations at the nanoscale are reviewed as these studies provide information about the behavior of cells at interfaces. Recent advances include the use of atomic force microscopy (AFM), although only a few studies have been applied to diatoms. Regarding the electrochemical behavior of SS, the mechanisms by which diatoms influence the potential ennoblement process is discussed. Such studies reveal the association of diatoms, in addition to bacteria, with biocorrosion processes.

  15. Architecture and material properties of diatom shells provide effective mechanical protection

    Science.gov (United States)

    Hamm, Christian E.; Merkel, Rudolf; Springer, Olaf; Jurkojc, Piotr; Maier, Christian; Prechtel, Kathrin; Smetacek, Victor

    2003-02-01

    Diatoms are the major contributors to phytoplankton blooms in lakes and in the sea and hence are central in aquatic ecosystems and the global carbon cycle. All free-living diatoms differ from other phytoplankton groups in having silicified cell walls in the form of two `shells' (the frustule) of manifold shape and intricate architecture whose function and role, if any, in contributing to the evolutionary success of diatoms is under debate. We explored the defence potential of the frustules as armour against predators by measuring their strength. Real and virtual loading tests (using calibrated glass microneedles and finite element analysis) were performed on centric and pennate diatom cells. Here we show that the frustules are remarkably strong by virtue of their architecture and the material properties of the diatom silica. We conclude that diatom frustules have evolved as mechanical protection for the cells because exceptional force is required to break them. The evolutionary arms race between diatoms and their specialized predators will have had considerable influence in structuring pelagic food webs and biogeochemical cycles.

  16. Investigation of the hydrodynamic behavior of diatom aggregates using particle image velocimetry.

    Science.gov (United States)

    Xiao, Feng; Li, Xiaoyan; Lam, Kitming; Wang, Dongsheng

    2012-01-01

    The hydrodynamic behavior of diatom aggregates has a significant influence on the interactions and flocculation kinetics of algae. However, characterization of the hydrodynamics of diatoms and diatom aggregates in water is rather difficult. In this laboratory study, an advanced visualization technique in particle image velocimetry (PIV) was employed to investigate the hydrodynamic properties of settling diatom aggregates. The experiments were conducted in a settling column filled with a suspension of fluorescent polymeric beads as seed tracers. A laser light sheet was generated by the PIV setup to illuminate a thin vertical planar region in the settling column, while the motions of particles were recorded by a high speed charge-coupled device (CCD) camera. This technique was able to capture the trajectories of the tracers when a diatom aggregate settled through the tracer suspension. The PIV results indicated directly the curvilinear feature of the streamlines around diatom aggregates. The rectilinear collision model largely overestimated the collision areas of the settling particles. Algae aggregates appeared to be highly porous and fractal, which allowed streamlines to penetrate into the aggregate interior. The diatom aggregates have a fluid collection efficiency of 10%-40%. The permeable feature of aggregates can significantly enhance the collisions and flocculation between the aggregates and other small particles including algal cells in water.

  17. Viscosity of Heterogeneous Silicate Melts: A Non-Newtonian Model

    Science.gov (United States)

    Liu, Zhuangzhuang; Blanpain, Bart; Guo, Muxing

    2017-12-01

    The recently published viscosity data of heterogeneous silicate melts with well-documented structure and experimental conditions are critically re-analyzed and tabulated. By using these data, a non-Newtonian viscosity model incorporating solid fraction, solid shape, and shear rate is proposed on the basis of the power-law equation. This model allows calculating the viscosity of the heterogeneous silicate melts with solid fraction up to 34 vol pct. The error between the calculated and measured data is evaluated to be 32 pct, which is acceptable considering the large error in viscosity measurement of the completely liquid silicate melt.

  18. Chemistry of the subalkalic silicic obsidians

    Science.gov (United States)

    MacDonald, Ray; Smith, Robert L.; Thomas, John E.

    1992-01-01

    Nonhydrated obsidians are quenched magmatic liquids that record in their chemical compositions details of the tectonic environment of formation and of the differentiation mechanisms that affected their subsequent evolution. This study attempts to analyze, in terms of geologic processes, the compositional variations in the subalkalic silicic obsidians (Si02≥70 percent by weight, molecular (Na2O+K20)>Al2O3). New major- and trace-element determinations of 241 samples and a compilation of 130 published major-element analyses are reported and interpreted. Obsidians from five different tectonic settings are recognized: (1) primitive island arcs, (2) mature island arcs, (3) continental margins, (4) continental interiors, and (5) oceanic extensional zones. Tectonomagmatic discrimination between these groups is successfully made on Nb-Ta, Nb-FeOt and Th-Hf-Ta plots, and compositional ranges and averages for each group are presented. The chemical differences between groups are related to the type of crust in which magmas were generated. With increasingly sialic (continental type) crust, the obsidians show overall enrichment in F, Be, Li, Mo, Nb, Rb, Sn, Ta, U, W, Zn, and the rare-earth elements, and depletion in Mg, Ca, Ba, Co, Sc, Sr, and Zr. They become more potassic, have higher Fe/Mg and F/Cl ratios, and lower Zr/Hf, Nb/Ta, and Th/U ratios. Higher values of total rare-earth elements are accompanied by light rare-earth-element enrichment and pronounced negative Eu anomalies. An attempt is made to link obsidian chemistry to genetic mechanlism. Two broad groups of rocks are distinguished: one generated where crystal-liquid processes dominated (CLPD types), which are the products of crustal anatexis, possibly under conditions of low halogen fugacity, ± crystal fractionation ± magma mixing; and a second group represented by rocks formed in the upper parts of large magma chambers by interplays of crystal fractionation, volatile transfer, magma mixing, and possibly various

  19. Diatom Transcriptional and Physiological Responses to Changes in Iron Bioavailability across Ocean Provinces

    Directory of Open Access Journals (Sweden)

    Natalie R. Cohen

    2017-11-01

    Full Text Available Changes in iron (Fe bioavailability influence diatom physiology and community composition, and thus have a profound impact on primary productivity and ecosystem dynamics. Iron limitation of diatom growth rates has been demonstrated in both oceanic and coastal waters of the Northeast Pacific Ocean and is predicted to become more pervasive in future oceans. However, it is unclear how the strategies utilized by phytoplankton to cope with low Fe bioavailability and resupply differ across these ocean provinces. We investigated the response of diatom communities to variable Fe conditions through incubation experiments performed in the Fe mosaic of the California Upwelling Zone and along a natural Fe gradient in the Northeast Pacific Ocean. Through coupling gene expression of two dominant diatom taxa (Pseudo-nitzschia and Thalassiosira with biological rate process measurements, we provide an in-depth examination of the physiological and molecular responses associated with varying Fe status. Following Fe enrichment, oceanic diatoms showed distinct differential expression of gene products involved in nitrogen assimilation, photosynthetic carbon fixation, and vitamin production compared to diatoms from low-Fe coastal sites, possibly driven by the chronic nature of Fe stress at the oceanic site. Genes of interest involved in Fe and N metabolism additionally exhibited divergent expression patterns between the two diatom taxa investigated, demonstrating that diverse diatoms may invoke alternative strategies when dealing with identical changes in their environment. We report here several mechanisms used distinctly by coastal or oceanic diatom communities as well as numerous taxa-specific strategies for coping with Fe stress and rearranging nutrient metabolism following Fe enrichment.

  20. Diatoms as an indicator for tile drainage flow in a German lowland catchment.

    Science.gov (United States)

    Wu, Naicheng; Faber, Claas; Ulrich, Uta; Fohrer, Nicola

    2018-01-01

    The separation of runoff components within a model simulation is of great importance for a successful implementation of management measures. Diatoms could be a promising indicator for tile drainage flow due to their diverse preferences to different aquatic habitats. In this study, we collected diatom samples of 9 sites (4 tile drainage, TD, and 5 river sites, Ri) in a German lowland catchment at a weekly or biweekly time step from March to July 2013 with the aim of testing the suitability of diatoms for tile drainage flow, which is typical for lowland catchment. Planothidium lanceolatum , Ulnaria biceps , and Navicula gregaria dominated in TD sites with relative abundances of 22.2, 21.5, and 10.9%, respectively. For Ri sites, the most abundant species was Navicula lanceolata (20.5%), followed by Ulnaria biceps (12.9%), Cyclotella meneghiniana (9.5%), and Planothidium lanceolatum (9.3%). Compared with Ri sites, TD had a lower diatom density, biomass, species richness, and percentage of Aquatic/Riparian diatoms (AqRi%). However, the proportion of Riparian diatoms (RiZo%) increased at TD. Indicator value method (IndVal) revealed that the two groups (Ri and TD) were characterized by different indicator species. Fifteen taxa, including Cocconeis placentula , Cyclotella meneghiniana , N. lanceolata , and U. biceps , were significant indicators for Ri sites. Planothidium lanceolatum , Achnanthidium minutissimum , and Navicula gregaria were significant indicators for TD sites. A pronounced variation was found in the species lists of diatom community between Ri and TD water body types associated with different indicator species. With respect to hydrograph separation, these findings highlight the suitability of diatoms as an indicator for tile drainage flow. However, spatial and temporal variations of diatoms should be considered in future surveys.

  1. Interstellar silicate analogs for grain-surface reaction experiments: Gas-phase condensation and characterization of the silicate dust grains

    Energy Technology Data Exchange (ETDEWEB)

    Sabri, T.; Jäger, C. [Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena Institute of Solid State Physics, Helmholtzweg 3, D-07743 Jena (Germany); Gavilan, L.; Lemaire, J. L.; Vidali, G. [Observatoire de Paris/Université de Cergy-Pontoise, 5 mail Gay Lussac, F-95000 Cergy-Pontoise (France); Mutschke, H. [Laboratory Astrophysics Group of the Astrophysical Institute and University Observatory, Friedrich Schiller University Jena Schillergässchen 3, D-07743 Jena (Germany); Henning, T., E-mail: tolou.sabri@uni-jena.de [Max Planck Institute for Astronomy Königstuhl 17, D-69117 Heidelberg (Germany)

    2014-01-10

    Amorphous, astrophysically relevant silicates were prepared by laser ablation of siliceous targets and subsequent quenching of the evaporated atoms and clusters in a helium/oxygen gas atmosphere. The described gas-phase condensation method can be used to synthesize homogeneous and astrophysically relevant silicates with different compositions ranging from nonstoichiometric magnesium iron silicates to pyroxene- and olivine-type stoichiometry. Analytical tools have been used to characterize the morphology, composition, and spectral properties of the condensates. The nanometer-sized silicate condensates represent a new family of cosmic dust analogs that can generally be used for laboratory studies of cosmic processes related to condensation, processing, and destruction of cosmic dust in different astrophysical environments. The well-characterized silicates comprising amorphous Mg{sub 2}SiO{sub 4} and Fe{sub 2}SiO{sub 4}, as well as the corresponding crystalline silicates forsterite and fayalite, produced by thermal annealing of the amorphous condensates, have been used as real grain surfaces for H{sub 2} formation experiments. A specifically developed ultra-high vacuum apparatus has been used for the investigation of molecule formation experiments. The results of these molecular formation experiments on differently structured Mg{sub 2}SiO{sub 4} and Fe{sub 2}SiO{sub 4} described in this paper will be the topic of the next paper of this series.

  2. THE RESPONSE OF THE PERIPHYTIC DIATOM COMMUNITY TO ACID MINE DRAINAGE POLLUTION

    Directory of Open Access Journals (Sweden)

    Andreea Ciorba

    2004-01-01

    Full Text Available This paper proposes to relate the principal characteristics of diatom community (species richness, biodiversity, community biomass, diatom indices to the stress induced by acidification and high levels of metal. The study was done in a mine drainage affected area in Galicia (NW Spain by comparing periphytic diatom communities from polluted streams to ones in supposedly clean waters. The change in the dominant species was the clearest response to AMD pollution while species richness and diversity were sensitive only to high levels of pollution.

  3. Do diatoms percolate through soil and can they be used for tracing the origin of runoff?

    Science.gov (United States)

    De Graaf, Lenka; Cammeraat, Erik; Pfister, Laurent; Wetzel, Carlos; Klaus, Julian; Hissler, Christophe

    2015-04-01

    Tracers are widely used to study the movement of water in a catchment. Because of depletion of scientific possibilities with most common tracer types, we proposed the use of diatoms as a natural tracer. Paradoxical results on the contribution of surface runoff to the storm hydrograph were obtained in pioneer research on this idea. Diatom transport via the subsurface flow to the stream would explain this paradox. Prerequisite for this is vertical transport of diatoms through soils, which is the topic of this study. Emphasis is on percolation behavior (speed of percolation, speed of percolation over time, and species distribution) of Pseudostaurosira sp. and Melosira sp. (Bacillariophyceae) through undisturbed soil columns of contrasting substrates. Co-objective is to study the flowpaths of water through the soil columns. Natural undisturbed soil columns were sampled in the Attert basin (Luxembourg) on schist, marl and sandstone substrates. Rain simulation experiments were performed to study vertical diatom transport. Rhodamine dye experiments were carried out to gain insight in the active flowpaths of water, and breakthrough experiments were performed to study the responses of the soil columns to applied water. Diatoms were transported through the soil columns of the three substrates. A vast majority of diatom percolation took place within the first 15 minutes, percolation hereafter was marginal but nevertheless present. Peaks in diatom percolation corresponded with a high flux caused by the addition of the diatom culture, but seepage of diatoms along the sides is unlikely according to the species distribution and the rhodamine dye experiment. Pseudostaurosira sp. percolated significantly better than Melosira sp. Significantly more diatoms percolated through the marl columns compared to the schist columns and variance within the sandstone group was very high. Absolute differences between substrates however, were marginal. Most preferential flowpaths were observed in

  4. Limits to gene flow in a cosmopolitan marine planktonic diatom.

    Science.gov (United States)

    Casteleyn, Griet; Leliaert, Frederik; Backeljau, Thierry; Debeer, Ann-Eline; Kotaki, Yuichi; Rhodes, Lesley; Lundholm, Nina; Sabbe, Koen; Vyverman, Wim

    2010-07-20

    The role of geographic isolation in marine microbial speciation is hotly debated because of the high dispersal potential and large population sizes of planktonic microorganisms and the apparent lack of strong dispersal barriers in the open sea. Here, we show that gene flow between distant populations of the globally distributed, bloom-forming diatom species Pseudo-nitzschia pungens (clade I) is limited and follows a strong isolation by distance pattern. Furthermore, phylogenetic analysis implies that under appropriate geographic and environmental circumstances, like the pronounced climatic changes in the Pleistocene, population structuring may lead to speciation and hence may play an important role in diversification of marine planktonic microorganisms. A better understanding of the factors that control population structuring is thus essential to reveal the role of allopatric speciation in marine microorganisms.

  5. Sorption of 237Pu by the diatom Asterionella formosa

    International Nuclear Information System (INIS)

    Conway, H.L.; Wahlgren, M.A.; Peterson, N.; Nelson, D.M.

    1976-01-01

    Knowledge of the behavior of the man-made radionuclide plutonium within aquatic environments is of fundamental importance in assessing its potential hazards and ecological impact. The sorption of plutonium by phytoplankton and other algae is the dominant factor in the biological transport of plutonium in the aquatic environment, and it has been suggested that sorption by phytoplankton may be responsible for the seasonal loss of plutonium from the epilimnion of Lake Michigan. A unialgal diatom culture was spiked with 237 Pu tracer solution in an attempt to simulate the behavior of fallout plutonium observed in field studies. The results were encouraging in that the 237 Pu in the filtered lake water medium exhibited strongly anionic properties similar to fallout plutonium in Lake Michigan, with limited sorption on container walls. The purpose of the present study was to extend the investigations of the sorption of plutonium by phytoplankton in a controlled environment using continuous culture techniques

  6. TRIGLYCERIDE COMPOSITION OF SIXTEEN STRAINS OF MARINE DIATOM

    Directory of Open Access Journals (Sweden)

    Lily M.G. Panggabean

    2013-07-01

    Full Text Available Trigliceride or triacylglicerol (TAG composition in crude oil of sixteen strain of marine diatom has been detected by spectra analyses on an Electrospray - Ion Trap – Mass Spectrometry (ESI-IT-MS HCT Bruker-Daltonic GmbH instrument with AgNO3 used as coordination ionization agent. Biomass samples of each microalga strain were taken from early and late stationary cultures in f/2 enriched seawater and algal oils were extracted according to Bligh and Dyer. Results from spectra analysis showed that P-Pt-P (C16:0-C16:1-C16:0 were distinguished in TAG from diatom strains Chaetoceros sp.1, Chaetoceros sp.2, Thalasiossira sp.1, Thalasiossira sp.2, Thalasiossira sp.3, Navicula sp. 1, Navicula sp. 2, Navicula sp. 3, Navicula sp. 4, Nitzschia sp. 2 and Amphora sp. In contrast, TAGs in Melosira sp. included P-P-P (C16:0-C16:0-C16:0 and P-P-O (C16:0-C16:0-C18:1 were identified. TAGs from Chaetoceros sp. were the most varies among samples, i.e. P-Pt-P (C16:0-C16:1-C16:0, A-P-M (C20:4-C16:0-C14:0, P-Pt-Lt (C16:0-C16:1-C18:3, P-Pt-A (C16:0-C16:1-C20:4, D-P-P (C22:6-C16:0-C16:0, A-Ln-P (C20:4-C18:2-C16:0. Various TAGs were also detected in Nitzschia sp.2, i.e. P-Pt-M (C16:0-C16:1-C14:0, P-Pt-P (C16:0-C16:1-C16:0, P-Pt-S (C16:0-C16:1-C18:0, P-Pt-A (C16:0-C16:1-C20:4. TAGs composition in Skeletonema strains that similar to those in Nitzschia sp.1 has longer carbon, i.e. P-P-O (C16:0-C16:0-C18:1, P-O-O (C16:0-C18:1-C18:1 and O-O-O (C18:1-C18:1-C18:1. TAGs with longer carbon chain and more double bond including highly unsaturated fatty acid C20:4 were increased with culture age in diatoms Chaetoceros sp.1, Chaetoceros sp.2, Thalasiossira sp.2, Navicula sp.1 and Nitzschia sp. 2.Keywords: diatom, TAG, ESI-IT-MS, f/2, early and late stationary

  7. Quantum work distribution for a driven diatomic molecule

    International Nuclear Information System (INIS)

    Leonard, Alison; Deffner, Sebastian

    2015-01-01

    Highlights: • A method for calculating the time-dependent solution for a driven system is proposed. • These solutions are used to compute the quantum work distribution. • This distribution is calculated for the Morse potential mimicking a diatomic molecule. • Due to bound and scattering states distribution exhibits continuous and discrete part. • Result is compared with that of a harmonic approximation. - Abstract: We compute the quantum work distribution for a driven Morse oscillator. To this end, we solve the time-dependent dynamics for a scale-invariant process, from which the exact expressions for the transition probabilities are found. Special emphasis is put on the contributions to the work distribution from discrete (bound) and continuous (scattering) parts of the spectrum. The analysis is concluded by comparing the work distribution for the exact Morse potential and the one resulting from a harmonic approximation

  8. Sedimentation of phytoplankton during a diatom bloom : Rates and mechanisms

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Hansen, J.L.S.; Alldredge, A.L.

    1996-01-01

    Phytoplankton blooms are uncoupled from grazing and are normally terminated by sedimentation. There are several potential mechanisms by which phytoplankton cells may settle out of the photic zone: sinking of individual cells or chains, coagulation of cells into aggregates with high settling...... velocities, settling of cells attached to marine snow aggregates formed from discarded larvacean houses or pteropod feeding webs, and packaging of cells into rapidly falling zooplankton fecal pellets. We quantified the relative significance of these different mechanisms during a diatom bloom in a temperate...... to marine snow aggregates formed from discarded larvacean houses, whereas settling of unaggregated cells was insignificant. Formation rates of phytoplankton aggregates by physical coagulation was very low, and losses by this mechanism were much less than 0.07 d(-1); phytoplankton aggregates were neither...

  9. Shedding light on diatom photonics by means of digital holography.

    Science.gov (United States)

    Di Caprio, Giuseppe; Coppola, Giuseppe; De Stefano, Luca; De Stefano, Mario; Antonucci, Alessandra; Congestri, Roberta; De Tommasi, Edoardo

    2014-05-01

    Diatoms are among the dominant phytoplankters in the world's oceans, and their external silica investments, resembling artificial photonic crystals, are expected to play an active role in light manipulation. Digital holography allowed studying the interaction with light of Coscinodiscus wailesii cell wall reconstructing the light confinement inside the cell cytoplasm, condition that is hardly accessible via standard microscopy. The full characterization of the propagated beam, in terms of quantitative phase and intensity, removed a long-standing ambiguity about the origin of the light confinement. The data were discussed in the light of living cell behavior in response to their environment. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Nonlinear quantum dynamics in diatomic molecules: Vibration, rotation and spin

    International Nuclear Information System (INIS)

    Yang, Ciann-Dong; Weng, Hung-Jen

    2012-01-01

    Highlights: ► This paper reveals the internal nonlinear dynamics embedded in a molecular quantum state. ► Analyze quantum molecular dynamics in a deterministic way, while preserving the consistency with probability interpretation. ► Molecular vibration–rotation interaction and spin–orbital coupling are considered simultaneously. ► Spin is just the remnant angular motion when orbital angular momentum is zero. ► Spin is the “zero dynamics” of nonlinear quantum dynamics. - Abstract: For a given molecular wavefunction Ψ, the probability density function Ψ ∗ Ψ is not the only information that can be extracted from Ψ. We point out in this paper that nonlinear quantum dynamics of a diatomic molecule, completely consistent with the probability prediction of quantum mechanics, does exist and can be derived from the quantum Hamilton equations of motion determined by Ψ. It can be said that the probability density function Ψ ∗ Ψ is an external representation of the quantum state Ψ, while the related Hamilton dynamics is an internal representation of Ψ, which reveals the internal mechanism underlying the externally observed random events. The proposed internal representation of Ψ establishes a bridge between nonlinear dynamics and quantum mechanics, which allows the methods and tools already developed by the former to be applied to the latter. Based on the quantum Hamilton equations of motion derived from Ψ, vibration, rotation and spin motions of a diatomic molecule and the interactions between them can be analyzed simultaneously. The resulting dynamic analysis of molecular motion is compared with the conventional probability analysis and the consistency between them is demonstrated.

  11. Electronic structure calculations of calcium silicate hydrates

    International Nuclear Information System (INIS)

    Sterne, P.A.; Meike, A.

    1995-11-01

    Many phases in the calcium-silicate-hydrate system can develop in cement exposed over long periods of time to temperatures above 25 C. As a consequence, chemical reactions involving these phases can affect the relative humidity and water chemistry of a radioactive waste repository that contains significant amounts of cement. In order to predict and simulate these chemical reactions, the authors are developing an internally consistent database of crystalline Ca-Si-hydrate structures. The results of first principles electronic structure calculations on two such phases, wollastonite (CaSiO 3 ) and xonotlite (Ca 6 Si 6 O 17 (OH) 2 ), are reported here. The calculated ground state properties are in very good agreement with experiment, providing equilibrium lattice parameters within about 1--1.4% of the experimentally reported values. The roles of the different types of oxygen atoms, which are fundamental to understanding the energetics of crystalline Ca-Si-hydrates are briefly discussed in terms of their electronic state densities. The good agreement with experiment for the lattice parameters and the consistency of the electronic density of states features for the two structures demonstrate the applicability of these electronic structure methods in calculating the fundamental properties of these phases

  12. Calcium Isotopic Composition of Bulk Silicate Earth

    Science.gov (United States)

    Kang, J.; Ionov, D. A.; Liu, F.; Zhang, C.; Zhang, Z.; Huang, F.

    2016-12-01

    Ca isotopes are used to study the accretion history of the Earth and terrestrial planets, but, Ca isotopic composition of the Bulk Silicate Earth (BSE) remains poorly constrained [1]. To better understand the Ca isotopic composition of BSE, we analyzed 22 well studied peridotite xenoliths from Tariat (Mongolia), Vitim (southern Siberia) and Udachnaya (Siberian Craton). These samples include both fertile and highly depleted garnet and spinel peridotites that show no or only minor post-melting metasomatism or alteration. Ca isotope measurements were done on a Triton-TIMS using double spike method at the Guangzhou Institute of Geochemistry, CAS. The data are reported as δ44/40Ca (relative to NIST SRM 915a). Results for geostandards are consistent with those from other laboratories. 2 standard deviations of SRM 915a analyses are 0.13‰ (n=48). δ44/40Ca of both and fertile and refractory peridotites range from 0.79 to 1.07‰ producing an average of 0.93±0.12‰ (2SD). This value defines the Ca isotopic composition of the BSE, which is consistent with the average δ44/40Ca of oceanic basalts ( 0.90‰)[2,3]. [1] Huang et al (2010) EPSL 292; [2] Valdes et al (2014) EPSL 394; [3]DePaolo (2004) RMG 55.

  13. Suppressive effects of a polymer sodium silicate solution on ...

    African Journals Online (AJOL)

    Mohsen

    2015-10-21

    Oct 21, 2015 ... suppressive effects of sodium silicate in the polymer form were confirmed against powdery mildew and ... crops (such as rice) controls diseases and could reduce ... negative charge and sodium ions with a positive charge.

  14. Conversion of rice hull ash into soluble sodium silicate

    Directory of Open Access Journals (Sweden)

    Edson Luiz Foletto

    2006-09-01

    Full Text Available Sodium silicate is used as raw material for several purposes: silica gel production, preparation of catalysts, inks, load for medicines, concrete hardening accelerator, component of detergents and soaps, refractory constituent and deflocculant in clay slurries. In this work sodium silicate was produced by reacting rice hull ash (RHA and aqueous sodium hydroxide, in open and closed reaction systems. The studied process variables were time, temperature of reaction and composition of the reaction mixture (expressed in terms of molar ratios NaOH/SiO2 and H2O/SiO2. About 90% silica conversion contained in the RHA into sodium silicate was achieved in closed system at 200 °C. The results showed that sodium silicate production from RHA can generate aggregate value to this residue.

  15. Synthesis of the Tube Silicate Litidionite and Structural Relationships between It and Some Other Silicates.

    Science.gov (United States)

    1982-02-17

    CuSi4015 Others are agrellite, NaCa2Si4O0oF, 1 6 narsarsukite, Na2TiSi4O 1 7 miserite, KCa5 i2 07 Si601 5 (OH)F,18 and probably canasite , Na4K2Ca 5...and canasite are rare. Litidionite is apparently very rare, the only reported occurrence of it being in the crater of Mt. Vesuvius. Both litidionite1...narsarsukite, miserite, and probably canasite contain, like 13-19 lititionite, tube silicate ions. The first three contain ions that are the same as that in

  16. Thermal properties and application of potential lithium silicate breeder materials

    International Nuclear Information System (INIS)

    Skokan, A.; Wedemeyer, H.; Vollath, D.; Gunther, E.

    1987-01-01

    Phase relations, thermal stability and preparation methods of the Li 2 O-rich silicates Li 8 SiO 6 and ''Li 6 SiO 5 '' have been investigated experimentally, the application of these compounds as solid breeder materials is discussed. In the second part of this contribution, the results of thermal expansion measurements on the silicates Li 2 SiO 3 , Li 4 SiO 4 and Li 8 SiO 6 are presented

  17. Thermal properties and application of potential lithium silicate breeder materials

    International Nuclear Information System (INIS)

    Skokan, A.; Wedemeyer, H.; Vollath, D.; Guenther, E.

    1986-01-01

    Phase relations, thermal stability and preparation methods of the Li 2 O-rich silicates Li 8 SiO 6 and 'Li 6 SiO 5 ' have been investigated experimentally, the application of these compounds as solid breeder materials is discussed. In the second part of this contribution, the results of thermal expansion measurements on the silicates Li 2 SiO 3 , Li 4 SiO 4 and Li 8 SiO 6 are presented. (author)

  18. Comparison of silicon nanoparticles and silicate treatments in fenugreek.

    Science.gov (United States)

    Nazaralian, Sanam; Majd, Ahmad; Irian, Saeed; Najafi, Farzaneh; Ghahremaninejad, Farrokh; Landberg, Tommy; Greger, Maria

    2017-06-01

    Silicon (Si) fertilization improves crop cultivation and is commonly added in the form of soluble silicates. However, most natural plant-available Si originates from plant formed amorphous SiO 2 particles, phytoliths, similar to SiO 2 -nanoparticles (SiNP). In this work we, therefore, compared the effect by sodium silicate and that of SiNP on Si accumulation, activity of antioxidative stress enzymes catalase, peroxidase, superoxide dismutase, lignification of xylem cell walls and activity of phenylalanine ammonia-lyase (PAL) as well as expression of genes for the putative silicon transporter (PST), defensive (Tfgd 1) and phosphoenolpyruvate carboxykinase (PEPCK) and protein in fenugreek (Trigonella foenum-graecum L.) grown in hydroponics. The results showed that Si was taken up from both silicate and SiNP treatments and increasing sodium silicate addition increased the translocation of Si to the shoot, while this was not shown with increasing SiNP addition. The silicon transporter PST was upregulated at a greater level when sodium silicate was added compared with SiNP addition. There were no differences in effects between sodium silicate and SiNP treatments on the other parameters measured. Both treatments increased the uptake and accumulation of Si, xylem cell wall lignification, cell wall thickness, PAL activity and protein concentration in seedlings, while there was no effect on antioxidative enzyme activity. Tfgd 1 expression was strongly downregulated in leaves at Si addition. The similarity in effects by silicate and SiNP would be due to that SiNP releases silicate, which may be taken up, shown by a decrease in SiNP particle size with time in the medium. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  19. PETROLOGY AND GEOCHEMISTRY OF CALC-SILICATE SCHISTS ...

    African Journals Online (AJOL)

    DR OKONKOWO

    2012-02-29

    silicate reaction bands have higher contents of CaO and Sr and lower concentrations of K2O, Rb, Ni, and Ba relative to the calc-silicate schists; and relatively higher SiO2, TiO2, Al2O3, Fe2O3, MgO, Na2O, K2O and P2O5 and lower ...

  20. The application of silicon and silicates in dentistry: a review.

    Science.gov (United States)

    Lührs, A-K; Geurtsen, Werner

    2009-01-01

    Silicates and silicate-based compounds are frequently used materials in dentistry. One of their major applications is their use as fillers in different dental filling materials such as glass-ionomer cements, compomers, composites, and adhesive systems. In these materials, the fillers react with acids during the setting process or they improve the mechanical properties by increasing physical resistance, thermal expansion coefficient and radiopacity in acrylic filling materials. They also reduce polymerization shrinkage, and increase esthetics as well as handling properties. Furthermore, silicates are used for the tribochemical silication of different surfaces such as ceramics or alloys. The silicate layer formed in this process is the chemical basis for silanes that form a bond between this layer and the organic composite matrix. It also provides a micromechanical bond between the surface of the material and the composite matrix. Silicates are also a component of dental ceramics, which are frequently used in dentistry, for instance for veneers, inlays, and onlays, for denture teeth, and for full-ceramic crowns or as crown veneering materials.

  1. High Pressure/Temperature Metal Silicate Partitioning of Tungsten

    Science.gov (United States)

    Shofner, G. A.; Danielson, L.; Righter, K.; Campbell, A. J.

    2010-01-01

    The behavior of chemical elements during metal/silicate segregation and their resulting distribution in Earth's mantle and core provide insight into core formation processes. Experimental determination of partition coefficients allows calculations of element distributions that can be compared to accepted values of element abundances in the silicate (mantle) and metallic (core) portions of the Earth. Tungsten (W) is a moderately siderophile element and thus preferentially partitions into metal versus silicate under many planetary conditions. The partitioning behavior has been shown to vary with temperature, silicate composition, oxygen fugacity, and pressure. Most of the previous work on W partitioning has been conducted at 1-bar conditions or at relatively low pressures, i.e. pressure. Predictions based on extrapolation of existing data and parameterizations suggest an increased pressured dependence on metal/ silicate partitioning of W at higher pressures 5. However, the dependence on pressure is not as well constrained as T, fO2, and silicate composition. This poses a problem because proposed equilibration pressures for core formation range from 27 to 50 GPa, falling well outside the experimental range, therefore requiring exptrapolation of a parametereized model. Higher pressure data are needed to improve our understanding of W partitioning at these more extreme conditions.

  2. Understanding the sub-cellular dynamics of silicon transportation and synthesis in diatoms using population-level data and computational optimization.

    Directory of Open Access Journals (Sweden)

    Narjes Javaheri

    2014-06-01

    Full Text Available Controlled synthesis of silicon is a major challenge in nanotechnology and material science. Diatoms, the unicellular algae, are an inspiring example of silica biosynthesis, producing complex and delicate nano-structures. This happens in several cell compartments, including cytoplasm and silica deposition vesicle (SDV. Considering the low concentration of silicic acid in oceans, cells have developed silicon transporter proteins (SIT. Moreover, cells change the level of active SITs during one cell cycle, likely as a response to the level of external nutrients and internal deposition rates. Despite this topic being of fundamental interest, the intracellular dynamics of nutrients and cell regulation strategies remain poorly understood. One reason is the difficulties in measurements and manipulation of these mechanisms at such small scales, and even when possible, data often contain large errors. Therefore, using computational techniques seems inevitable. We have constructed a mathematical model for silicon dynamics in the diatom Thalassiosira pseudonana in four compartments: external environment, cytoplasm, SDV and deposited silica. The model builds on mass conservation and Michaelis-Menten kinetics as mass transport equations. In order to find the free parameters of the model from sparse, noisy experimental data, an optimization technique (global and local search, together with enzyme related penalty terms, has been applied. We have connected population-level data to individual-cell-level quantities including the effect of early division of non-synchronized cells. Our model is robust, proven by sensitivity and perturbation analysis, and predicts dynamics of intracellular nutrients and enzymes in different compartments. The model produces different uptake regimes, previously recognized as surge, externally-controlled and internally-controlled uptakes. Finally, we imposed a flux of SITs to the model and compared it with previous classical kinetics

  3. Epiphytic diatoms in lotic and lentic waters - diversity and representation of species complexes

    Czech Academy of Sciences Publication Activity Database

    Kollár, J.; Fránková, Markéta; Hašler, P.; Letáková, M.; Poulíčková, A.

    2015-01-01

    Roč. 15, č. 2 (2015), s. 259-271 ISSN 1802-5439 Institutional support: RVO:67985939 Keywords : diatoms * epiphyton * species comlexes * lotic and lentic waters Subject RIV: EF - Botanics Impact factor: 2.026, year: 2015

  4. Relationships between diatoms and tidal environments in Oregon and Washington, USA

    Science.gov (United States)

    Sawai, Yuki; Horton, Benjamin P.; Kemp, Andrew C.; Hawkes, Andrea D.; Nagumo, Tamostsu; Nelson, Alan R.

    2016-01-01

    A new regional dataset comprising 425 intertidal diatom taxa from 175 samples from 11 ecologically diverse Oregon and Washington estuaries illustrates the importance of compiling a large modern dataset from a range of sites. Cluster analyses and detrended correspondence analysis of the diatom assemblages identify distinct vertical zones within supratidal, intertidal and subtidal environments at six of the 11 study sites, but the abundance of some of the most common species varies widely among and within sites. Canonical correspondence analysis of the regional dataset shows relationships between diatom species and tidal exposure, salinity and substratum (grain size and organic content). Correspondence analyses of local datasets show higher values of explained variation than the analysis of the combined regional dataset. Our results emphasize that studies of the autecology of diatom species require many samples from a range of modern environments to adequately characterize species–environment relationships.

  5. Seasonal variations in the fouling diatom community structure from a monsoon influenced tropical estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Mitbavkar, S.; Anil, A.C.

    Seasonal variations in the fouling diatom community from a monsoon influenced tropical estuary were investigated. The community composition did not differ significantly between stainless steel and polystyrene substrata due to dominance by Navicula...

  6. Morphometry and cell volumes of diatoms from a tropical estuary of India

    Digital Repository Service at National Institute of Oceanography (India)

    RaviKumar, M.S.; Ramaiah, N.; Tang, D.

    Cell volumes and per cell carbon contents of different diatoms (10 centric, 14 pennate and 1 dinoflagellate) collected from Dona Paula Bay in the central west coast of India have been analyzed. Morphometric information on the phytoplankton types...

  7. A diatom functional-based approach to assess changing environmental conditions in temporary depressional wetlands

    CSIR Research Space (South Africa)

    Riato, L

    2017-07-01

    Full Text Available is limited although important for the development of temporary wetland biological assessments. We assessed how diatom life-form and ecological guilds responded to a seasonal hydrological and hydrochemical gradient in three least human-disturbed, temporary...

  8. Effect of holothurian and zoanthid extracts on growth of some bacterial and diatom species

    Digital Repository Service at National Institute of Oceanography (India)

    Gonsalves, C.

    The antifouling properties of the extracts from two zoanthids, viz. Zoanthus sp, Protopalythoa sp and one holothurian species, viz. Holothuria leucospilota occurring in the coastal waters off Goa were tested against 5 bacteria and 2 diatom species...

  9. Effect of chlorination on the development of marine biofilms dominated by diatoms

    Digital Repository Service at National Institute of Oceanography (India)

    Patil, J.S.; Jagadeesan, V.

    , and Thalassionema did not increase in density after chlorine treatment. It was also demonstrated that diatoms can colonize, grow and photosynthesize on chlorine-treated surfaces. Under pulse chlorination (treatment every 6 h), irrespective of chlorine concentration...

  10. An integrative analysis of post-translational histone modifications in the marine diatom Phaeodactylum tricornutum

    KAUST Repository

    Veluchamy, Alaguraj; Rastogi, Achal; Lin, Xin; Lombard, Bé rangè re; Murik, Omer; Thomas, Yann; Dingli, Florent; Rivarola, Maximo; Ott, Sandra; Liu, Xinyue; Sun, Yezhou; Rabinowicz, Pablo D.; McCarthy, James; Allen, Andrew E.; Loew, Damarys; Bowler, Chris; Tirichine, Leï la

    2015-01-01

    in global biogeochemical cycles. Dissecting chromatin-mediated regulation of genes in diatoms will help understand the ecological success of these organisms in contemporary oceans. Results: Here, we use high resolution mass spectrometry to identify a full

  11. Tidal Channel Diatom Assemblages Reflect within Wetland Environmental Conditions and Land Use at Multiple Scales

    Science.gov (United States)

    We characterized regional patterns of the tidal channel benthic diatom community and examined the relative importance of local wetland and surrounding landscape level factors measured at multiple scales in structuring this assemblage. Surrounding land cover was characterized at ...

  12. Influence of land-use patterns on benthic diatom communities and ...

    African Journals Online (AJOL)

    2010-03-01

    Mar 1, 2010 ... for management of Brazilian and other tropical lotic systems. The objective of this ... ity, floods and inundations, which affect diatom development, especially ...... Sociedade Brasileira de Ficologia, CETESB, São Paulo. 34-55.

  13. Phenotypic plasticity of southern ocean diatoms: key to success in the sea ice habitat?

    Directory of Open Access Journals (Sweden)

    Olivia Sackett

    Full Text Available Diatoms are the primary source of nutrition and energy for the Southern Ocean ecosystem. Microalgae, including diatoms, synthesise biological macromolecules such as lipids, proteins and carbohydrates for growth, reproduction and acclimation to prevailing environmental conditions. Here we show that three key species of Southern Ocean diatom (Fragilariopsis cylindrus, Chaetoceros simplex and Pseudo-nitzschia subcurvata exhibited phenotypic plasticity in response to salinity and temperature regimes experienced during the seasonal formation and decay of sea ice. The degree of phenotypic plasticity, in terms of changes in macromolecular composition, was highly species-specific and consistent with each species' known distribution and abundance throughout sea ice, meltwater and pelagic habitats, suggesting that phenotypic plasticity may have been selected for by the extreme variability of the polar marine environment. We argue that changes in diatom macromolecular composition and shifts in species dominance in response to a changing climate have the potential to alter nutrient and energy fluxes throughout the Southern Ocean ecosystem.

  14. New and interesting small-celled naviculoid diatoms (Bacillariophyta) from the Maritime Antarctic Region

    Czech Academy of Sciences Publication Activity Database

    Van de Vijver, B.; Kopalová, Kateřina; Zidarova, R.; Cox, E. J.

    2013-01-01

    Roč. 97, 1-2 (2013), s. 189-208 ISSN 0029-5035 Institutional support: RVO:67985939 Keywords : Bacillariophyta * Diatoms * Maritime Antarctic Region Subject RIV: EF - Botanics Impact factor: 0.989, year: 2013

  15. Identification automatique des diatomées de la Merja fouarate : Une ...

    African Journals Online (AJOL)

    SARAH

    30 sept. 2015 ... Automatic identification of Fouarate Merja diatoms: An alternative to manual determination and classification .... 21 genres, avec une erreur de 4% car plusieurs organismes .... Electronic, Technologies of Information and.

  16. Intracellular nitrate of marine diatoms as a driver of anaerobic nitrogen cycling in sinking aggregates

    DEFF Research Database (Denmark)

    Kamp, Anja; Stief, Peter; Bristow, Laura A.

    2016-01-01

    % was recovered as nitrite. Hence, aggregate-associated diatoms accumulate nitrate from the surrounding water and sustain complex nitrogen transformations, including loss of fixed nitrogen, in anoxic, pelagic microniches. Additionally, it may be expected that intracellular nitrate not converted before...... store nitrate intracellularly, we explored the fate of intracellular nitrate and its availability for microbial metabolism within anoxic diatom-bacteria aggregates. The ubiquitous nitrate-storing diatom Skeletonema marinoi was studied as both axenic cultures and laboratory-produced diatom......-bacteria aggregates. Stable 15N isotope incubations under dark and anoxic conditions revealed that axenic S. marinoi is able to reduce intracellular nitrate to ammonium that is immediately excreted by the cells. When exposed to a light:dark cycle and oxic conditions, S. marinoi stored nitrate intracellularly...

  17. Autofluorescence imaging system to discriminate and quantify the distribution of benthic cyanobacteria and diatoms

    DEFF Research Database (Denmark)

    Carreira, Cátia; Staal, Marc Jaap; Middelboe, Mathias

    2015-01-01

    successfully to (mixed) laboratory cultures as well as natural photosynthetic microbial mats. Cultures of the diatom Nitzschia capitellata and the cyanobacterium Geitlerinema sp. showed close correlation between autofluorescence and cell abundance. This simple and cheap imaging system allows fast observations...

  18. Aulacoseira kruegeriana (Bacillariophyta, Coscinodiscophyceae): a new centric diatom from high-elevation Andean streams of Bolivia

    Czech Academy of Sciences Publication Activity Database

    Morales, E. A.; Rivera, S. F.; Rubin, S. D. C.; Vis, M. L.; Houk, Václav

    2015-01-01

    Roč. 30, č. 3 (2015), s. 269-277 ISSN 0269-249X Institutional support: RVO:67985939 Keywords : centric diatoms * taxonomy * valve ultrastructure Subject RIV: EF - Botanics Impact factor: 1.868, year: 2015

  19. Diatom species composition in the Raška river (Southwestern Serbia

    Directory of Open Access Journals (Sweden)

    Vidaković Danijela P.

    2015-01-01

    Full Text Available The paper presents data on the composition of epilithic diatoms in the Raška River. Samples were collected by scraping stone surfaces with a brush from 5 localities along the Raška River in April, June, August and November 2011 and March and May 2012. Diatom frustules were cleaned using cold acid method, and mounted on permanent slides. An investigation of the Raška River resulted in description of 106 diatom taxa. The most species rich genera are Navicula (10, Gomphonema (10 and Nitzschia (9, while other genera are presented with one or more species. Detailed floristic analysis of the benthic diatom flora in this river has not been conducted before. Therefore, this paper provides a groundwork for future researches. [Projekat Ministarstva nauke Republike Srbije, br. TR 037009

  20. Diatom production in the marine environment : implications for larval fish growth and condition

    DEFF Research Database (Denmark)

    St. John, Michael; Clemmesen, C.; Lund, T.

    2001-01-01

    To test the effects of diatom production on larval fish growth and condition. laboratory experiments were performed with larval North Sea cod reared on different algal food chains. These food chains were based on cultures of (a) the diatoms Skeletonema costatum and Thalassiosira weissflogii: (b....../omega6 fatty acids in the algal source had no significant effect. The highest and lowest growth rates were observed in food chains based on H. triquetra and T. weissflogii. respectively (means for days 14-16 of 4.0 and - 4.7). The mixed diatom/dinoflagellate diet resulted in inter- mediate growth rates...... and condition. Regressions of growth rates against EPA and DHA content indicated no inhibitory effect of diatom production on growth in larval cod...

  1. Molecular fossils of diatoms. Applications in petroleum geochemistry and palaeoenvironmental studies

    Energy Technology Data Exchange (ETDEWEB)

    Rampen, S.W.

    2009-06-11

    Diatoms are one of the major groups of algae which originated relatively recently and evolved in the Late Jurassic/Cretaceous. This thesis presents the results of a comprehensive study of diatom lipids in cultures and in the environment and their applications in the age determination of petroleum and in palaeoenvironmental studies. Diatom DNA sequences were analyzed in order to relate the phylogenetic positions of diatoms to the lipid chemotaxonomy. Forty four different sterols were identified in diatoms, with 24-methylcholesta-5,24(28)-dien-3-beta-ol being most common. 24-Methylcholesta-5,22E-dien-3-beta-ol, previously described as a diatom biomarker, was only the fifth most common sterol and absent in some major diatom groups. All identified sterols have been reported in other algae, but within the diatoms, some sterols and sterol compositions seem to be specific for specific phylogenetic clusters. Sterol compositions confirmed the separate phylogenetic position of the genus Attheya, as also indicated by molecular phylogeny and microscopy. 23-Methyl and 23,24-dimethyl sterols, often associated with dinoflagellate algae, were present in a substantial number of diatoms, suggesting that diatoms may also be a major source. Their phylogenetic position suggests that these diatoms originated from a single common ancestor which evolved in the late Jurassic. In addition to 23-methyl and 23,24-dimethyl sterols, the unusual sterol gorgosterol was found in two diatom cultures of the genus Delphineis. 24-Norsterols were found in the diatom species Thalassiosira aff. antarctica and in dinoflagellate cultures. The evolutionary history of dinoflagellates and diatoms explains the stepwise increases of 24-norsterane concentrations, diagenetic products of 24-norsterols, in petroleum. Long-chain 1,14-diols and 12-hydroxy methyl alkanoates were detected in Proboscia diatoms and may be used as indicators for high-nutrient conditions and upwelling. Their distributions varied between

  2. Deep carbon export from a Southern Ocean iron-fertilized diatom bloom

    Digital Repository Service at National Institute of Oceanography (India)

    Smetacek, V.; Klaas, C.; Strass, V.H.; Assmy, P.; Montresor, M.; Cisewski, B.; Savoye, N.; Webb, A.; d’Ovidio, F.; Arrieta, J.M.; Bathmann, U.; Bellerby, R.; Berg, G.M.; Croot, P.; Gonzalez, S.; Henjes, J.; Herndl, G.J.; Hoffmann, L.J.; Leach, H.; Losch, M.; Mills, M.M.; Neill, C.; Peeken, I.; Rottgers, R.; Sachs, O.; Sauter, E.; Schmidt, M.M.; Schwarz, J.; Terbruggen, A.; Wolf-Gladrow, D.

    Fertilization of the ocean by adding iron compounds has induced diatom-dominated phytoplankton blooms accompanied by considerable carbon dioxide drawdown in the ocean surface layer. However, because the fate of bloom biomass could not be adequately...

  3. Photophysiological variability of microphytobenthic diatoms after growth in different types of culture conditions

    NARCIS (Netherlands)

    Forster, R.M.; Martin-Jézéquel, V.R.

    2005-01-01

    Microphytobenthic diatoms have great ecological importance in estuarine and coastal marine ecosystenis, yet many aspects of their physiology have not been investigated under controlled conditions. This work describes patterns in growth rates and photosynthesis in different types of culture for

  4. The reponse of epilithic diatom assemblages to sewage pollution in mountain streams of the Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Moravcová, A.; Rauch, Ota; Lukavský, Jaromír; Nedbalová, Linda

    2013-01-01

    Roč. 146, č. 2 (2013), s. 153-166 ISSN 2032-3913 Institutional support: RVO:67985939 Keywords : epilitic diatoms * mountain streams * sewage polllution Subject RIV: EH - Ecology, Behaviour Impact factor: 0.960, year: 2013

  5. Occurrence of cyanobacteria - diatom symbiosis in the Bay of Bengal: Implications in biogeochemistry

    Digital Repository Service at National Institute of Oceanography (India)

    Kulkarni, V.V.; Chitari, R.R.; Narale, D.D.; Patil, J.S.; Anil, A.C.

    cyanobacterial endosymbiont of several diatom genera, are the most important diazotrophs accounting for approx. 63% of pelagic N sub(2) -fixation in the world’s oceans. However, information on R. intracellularis is lacking, even though its distribution...

  6. USE OF DIATOMS TO ASSES WATER QUALITY OF ANTHROPOGENICALLY MODIFIED MATYSÓWKA STREAM

    Directory of Open Access Journals (Sweden)

    Teresa Noga

    2013-04-01

    Full Text Available Matysówka stream is small, under 6 km long watercourse, which is a right-bank tributary of Strug River. In 2009–2011studies on the subject of diversity of diatom communities using diatom indices IPS, GDI and TDI for water quality assessment were conducted. On the stream 271 diatom taxa were identified, among which: Achnanthidium minutissimum var. minutissimum, Navicula cryptotenella, N. gregaria, N. lanceolata, N. tripunctata, Nitzschia linearis, N. pusilla, N. recta, Planothidium frequentissimum, Rhoicosphenia abbreviata were the most frequent. Middle and lower section of Matysówka stream was characterized by increased concentrations of phosphates, nitrites, ammonium, total phosphorus and nitrogen, BOD5. On the basis of diatom indices IPS and GDI waters were characterized as III–IV quality classes, while the TDI index revealed the worst water quality classes (IV–V.

  7. Diatom-based models for inferring water chemistry and hydrology in temporary depressional wetlands

    CSIR Research Space (South Africa)

    Riato, L

    2017-08-01

    Full Text Available Information on the response of temporary depressional wetland diatoms to human-induced disturbances is a limited and important component for the development of temporary wetland biological assessments in human-modified landscapes. Establishing a...

  8. Effect of moisture and chitosan layered silicate on morphology and properties of chitosan/layered silicates films

    International Nuclear Information System (INIS)

    Silva, J.R.M.B. da; Santos, B.F.F. dos; Leite, I.F.

    2014-01-01

    Thin chitosan films have been for some time an object of practical assessments. However, to obtain biopolymers capable of competing with common polymers a significant improvement in their properties is required. Currently, the technology of obtaining polymer/layered silicates nanocomposites has proven to be a good alternative. This work aims to evaluate the effect of chitosan content (CS) and layered silicates (AN) on the morphology and properties of chitosan/ layered silicate films. CS/AN bionanocomposites were prepared by the intercalation by solution in the proportion 1:1 and 5:1. Then were characterized by infrared spectroscopy (FTIR), diffraction (XRD) and X-ray thermogravimetry (TG). It is expected from the acquisition of films, based on different levels of chitosan and layered silicates, choose the best composition to serve as a matrix for packaging drugs and thus be used for future research. (author)

  9. Potassium silicate and calcium silicate on the resistance of soybean to Phakopsora pachyrhizi infection

    Directory of Open Access Journals (Sweden)

    Maria Fernanda Cruz

    2013-01-01

    Full Text Available The control of Asian Soybean Rust (ASR, caused by Phakopsora pachyrhizi, has been difficult due to the aggressiveness of the pathogen and the lack of resistant cultivars. The objective of this study was to evaluate the effects of spray of potassium silicate (PS and soil amendment with calcium silicate (CS on soybean resistance to ASR. The PS solution was sprayed to leaves 24 hours prior to fungal inoculation while CS was amended to the soil at thirty-five days before sowing. The infection process of P. pachyrhizi was investigated by scanning electron microscopy. The uredia on leaves of plants sprayed with PS were smaller and more compact than those observed on the leaves of plants grown in soil amended with CS or in soil non-amended with CS (control treatment. On leaves of plants from the control treatment, uredia produced many urediniospores at 9 days after inoculation, and the ASR severity was 15, 8 and 9%, respectively, for plants from control, PS and CS treatments. In conclusion, the spray of PS contributed to reduce the number of uredia per cm² of leaf area and both PS spray and CS resulted in lower ASR symptoms.

  10. Diet Reconstructed From an Analysis of Plant Microfossils in Human Dental Calculus From the Bronze Age Site of Shilinggang, Southwestern China

    Science.gov (United States)

    Zhang, N.; Dong, G.; Yang, X.; Zuo, X.; Kang, L.; Ren, L.; Liu, H.; Li, H.; Min, R.; Liu, X.; Zhang, D.; Chen, F.

    2017-12-01

    The extracted microfossils from the dental calculus of ancient teeth are a new form of archaeological evidence which can provide direct information on the plant diet of a population. Here, we present the results of analyses of starch grains and phytoliths trapped in the dental calculus of humans who occupied the Bronze Age site of Shilinggang ( 2500 cal yr BP) in Yunnan Province, southwestern China. The results demonstrate that the inhabitants consumed a wide range of plants, including rice, millet, and palms, together with other food plants which have not previously been detected in Yunnan. The discovery of various underground storage organs (USOs; tubers, roots, bulbs, and rhizomes) and acorns complements the application of conventional macrofossil and isotope studies to understand the diet of the Bronze Age human population of Yunnan. The wide variety of plant foods consumed suggests that the inhabitants adopted a broad-spectrum strategy of gathering food and cultivating crops in northwest Yunnan Province in the late Bronze Age at a time when agricultural societies were developed in the central plains of China.

  11. Stylolites, porosity, depositional texture, and silicates in chalk facies sediments

    DEFF Research Database (Denmark)

    Fabricius, Ida Lykke; Borre, Mai K.

    2007-01-01

    dissolution around 490 m below sea floor (bsf) corresponds to an interval of waning porosity-decline, and even the occurrence of proper stylolites from 830 m bsf is accompanied by only minor porosity reduction. Because opal is present, the pore-water is relatively rich in Si which through the formation of Ca......-silica complexes causes an apparent super-saturation of Ca and retards cementation. The onset of massive pore-filling cementation at 1100 m bsf may be controlled by the temperature-dependent transition from opal-CT to quartz. In the stylolite-bearing chalk of two wells in the Gorm and Tyra fields, the nannofossil...... matrix shows recrystallization but only minor pore-filling cement, whereas microfossils are cemented. Cementation in Gorm and Tyra is thus partial and has apparently not been retarded by opal-controlled pore-water. A possible explanation is that, due to the relatively high temperature, silica has...

  12. Role of Diatoms in the Spatial-Temporal Distribution of Intracellular Nitrate in Intertidal Sediment

    DEFF Research Database (Denmark)

    Stief, P.; Kamp, A.; de Beer, D.

    2013-01-01

    Intracellular nitrate storage allows microorganisms to survive fluctuating nutrient availability and anoxic conditions in aquatic ecosystems. Here we show that diatoms, ubiquitous and highly abundant microalgae, represent major cellular reservoirs of nitrate in an intertidal flat of the German Wa...... in anaerobic nitrate respiration. Due to the widespread dominance of diatoms in microphytobenthos, the total nitrate pool in coastal marine sediments may generally be at least two times larger than derived from porewater measurements and partially be recycled to ammonium....

  13. Decadal variations in diatoms and dinoflagellates on the inner shelf of the East China Sea, China

    Science.gov (United States)

    Abate, Rediat; Gao, Yahui; Chen, Changping; Liang, Junrong; Mu, Wenhua; Kifile, Demeke; Chen, Yanghang

    2017-11-01

    Diatoms and dinoflagellates are two major groups of phytoplankton that flourish in the oceans, particularly in coastal zone and upwelling systems, and their contrasting production have been reported in several world seas. However, this information is not available in the coastal East China Sea (ECS). Thus, to investigate and compare the decadal trends in diatoms and dinoflagellates, a sediment core, 47 cm long, was collected from the coastal zone of the ECS. Sediment chlorophyll- a (Chl- a), phytoplankton-group specific pigment signatures of diatoms and dinoflagellates, and diatom valve concentrations were determined. The sediment core covered the period from 1961 to 2011 AD. The chlorophyll- a contents ranged from 2.32 to 73 µg/g dry sediment (dw) and averaged 9.81 µg/g dw. Diatom absolute abundance ranged from 29152 to 177501 valve/gram (v/g) dw and averaged 72137 v/g dw. Diatom valve and diatom specific pigment marker concentrations were not significantly correlated. Peridinin increased after the 1980s in line with intensified use of fertilizer and related increases in nutrient inputs into the marine environment. The increased occurrence of dinoflagellate dominance after the 1980s can be mostly explained by the increase in nutrients. However, the contribution of dinoflagellates to total phytoplankton production (Chl- a) decreased during the final decade of this study, probably because of the overwhelming increase in diatom production that corresponded with the construction of the Three Gorges Dam (TGD) and related light availability. Similarly, the mean ratio of fucoxanthin/peridinin for the period from 1982 to 2001 was 6% less than for 1961 to 1982, while the ratio for 2001 to 2011 was 45.3% greater than for 1982 to 2001. The decadal variation in the fucoxanthin/peridinin ratio implies that dinoflagellate production had been gradually increasing until 2001. We suggest that the observed changes can be explained by anthropogenic impacts, such as nutrient

  14. Hierarchical and Size Dependent Mechanical Properties of Silica and Silicon Nanostructures Inspired by Diatom Algae

    Science.gov (United States)

    2010-09-01

    Chaniotakis. The physical and mechanical properties of composite cements manufactured with cal- careous and clayey greek diatomite mixtures. Cement and...Hierarchical and size dependent mechanical properties of silica and silicon nanostructures inspired by diatom algae by Andre Phillipe Garcia B.S...dependent mechanical properties of silica and silicon nanostructures inspired by diatom algae 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM

  15. Biosynthesis of gold nanoparticles using diatoms-silica-gold and EPS-gold bionanocomposite formation

    OpenAIRE

    Schröfel, Adam; Kratošová, Gabriela; Bohunická, Markéta; Dobročka, Edmund; Vávra, Ivo

    2011-01-01

    Novel synthesis of gold nanoparticles, EPS-gold, and silica-gold bionanocomposites by biologically driven processes employing two diatom strains (Navicula atomus, Diadesmis gallica) is described. Transmission electron microscopy (TEM) and electron diffraction analysis (SAED) revealed a presence of gold nanoparticles in the experimental solutions of the diatom culture mixed with tetrachloroaureate. Nature of the gold nanoparticles was confirmed by X-ray diffraction studies. Scanning electron m...

  16. Evolutionary origins and functions of the carotenoid biosynthetic pathway in marine diatoms.

    Directory of Open Access Journals (Sweden)

    Sacha Coesel

    Full Text Available Carotenoids are produced by all photosynthetic organisms, where they play essential roles in light harvesting and photoprotection. The carotenoid biosynthetic pathway of diatoms is largely unstudied, but is of particular interest because these organisms have a very different evolutionary history with respect to the Plantae and are thought to be derived from an ancient secondary endosymbiosis between heterotrophic and autotrophic eukaryotes. Furthermore, diatoms have an additional xanthophyll-based cycle for dissipating excess light energy with respect to green algae and higher plants. To explore the origins and functions of the carotenoid pathway in diatoms we searched for genes encoding pathway components in the recently completed genome sequences of two marine diatoms. Consistent with the supplemental xanthophyll cycle in diatoms, we found more copies of the genes encoding violaxanthin de-epoxidase (VDE and zeaxanthin epoxidase (ZEP enzymes compared with other photosynthetic eukaryotes. However, the similarity of these enzymes with those of higher plants indicates that they had very probably diversified before the secondary endosymbiosis had occurred, implying that VDE and ZEP represent early eukaryotic innovations in the Plantae. Consequently, the diatom chromist lineage likely obtained all paralogues of ZEP and VDE genes during the process of secondary endosymbiosis by gene transfer from the nucleus of the algal endosymbiont to the host nucleus. Furthermore, the presence of a ZEP gene in Tetrahymena thermophila provides the first evidence for a secondary plastid gene encoded in a heterotrophic ciliate, providing support for the chromalveolate hypothesis. Protein domain structures and expression analyses in the pennate diatom Phaeodactylum tricornutum indicate diverse roles for the different ZEP and VDE isoforms and demonstrate that they are differentially regulated by light. These studies therefore reveal the ancient origins of several

  17. Evolutionary origins and functions of the carotenoid biosynthetic pathway in marine diatoms.

    Science.gov (United States)

    Coesel, Sacha; Oborník, Miroslav; Varela, Joao; Falciatore, Angela; Bowler, Chris

    2008-08-06

    Carotenoids are produced by all photosynthetic organisms, where they play essential roles in light harvesting and photoprotection. The carotenoid biosynthetic pathway of diatoms is largely unstudied, but is of particular interest because these organisms have a very different evolutionary history with respect to the Plantae and are thought to be derived from an ancient secondary endosymbiosis between heterotrophic and autotrophic eukaryotes. Furthermore, diatoms have an additional xanthophyll-based cycle for dissipating excess light energy with respect to green algae and higher plants. To explore the origins and functions of the carotenoid pathway in diatoms we searched for genes encoding pathway components in the recently completed genome sequences of two marine diatoms. Consistent with the supplemental xanthophyll cycle in diatoms, we found more copies of the genes encoding violaxanthin de-epoxidase (VDE) and zeaxanthin epoxidase (ZEP) enzymes compared with other photosynthetic eukaryotes. However, the similarity of these enzymes with those of higher plants indicates that they had very probably diversified before the secondary endosymbiosis had occurred, implying that VDE and ZEP represent early eukaryotic innovations in the Plantae. Consequently, the diatom chromist lineage likely obtained all paralogues of ZEP and VDE genes during the process of secondary endosymbiosis by gene transfer from the nucleus of the algal endosymbiont to the host nucleus. Furthermore, the presence of a ZEP gene in Tetrahymena thermophila provides the first evidence for a secondary plastid gene encoded in a heterotrophic ciliate, providing support for the chromalveolate hypothesis. Protein domain structures and expression analyses in the pennate diatom Phaeodactylum tricornutum indicate diverse roles for the different ZEP and VDE isoforms and demonstrate that they are differentially regulated by light. These studies therefore reveal the ancient origins of several components of the

  18. Intracellular Nitrate of Marine Diatoms as a Driver of Anaerobic Nitrogen Cycling in Sinking Aggregates

    Directory of Open Access Journals (Sweden)

    Anja Kamp

    2016-11-01

    Full Text Available Diatom-bacteria aggregates are key for the vertical transport of organic carbon in the ocean. Sinking aggregates also represent pelagic microniches with intensified microbial activity, oxygen depletion in the center, and anaerobic nitrogen cycling. Since some of the aggregate-forming diatom species store nitrate intracellularly, we explored the fate of intracellular nitrate and its availability for microbial metabolism within anoxic diatom-bacteria aggregates. The ubiquitous nitrate-storing diatom Skeletonema marinoi was studied as both axenic cultures and laboratory-produced diatom-bacteria aggregates. Stable 15N isotope incubations under dark and anoxic conditions revealed that axenic S. marinoi is able to reduce intracellular nitrate to ammonium that is immediately excreted by the cells. When exposed to a light:dark cycle and oxic conditions, S. marinoi stored nitrate intracellularly in concentrations > 60 mmol L-1 both as free-living cells and associated to aggregates. Intracellular nitrate concentrations exceeded extracellular concentrations by three orders of magnitude. Intracellular nitrate was used up within 2-3 days after shifting diatom-bacteria aggregates to dark and anoxic conditions. Thirty-one percent of the diatom-derived nitrate was converted to nitrogen gas, indicating that a substantial fraction of the intracellular nitrate pool of S. marinoi becomes available to the aggregate-associated bacterial community. Only 5% of the intracellular nitrate was reduced to ammonium, while 59% was recovered as nitrite. Hence, aggregate-associated diatoms accumulate nitrate from the surrounding water and sustain complex nitrogen transformations, including loss of fixed nitrogen, in anoxic, pelagic microniches. Additionally, it may be expected that intracellular nitrate not converted before the aggregates have settled onto the seafloor could fuel benthic nitrogen transformations.

  19. Large centric diatoms allocate more cellular nitrogen to photosynthesis to counter slower RUBISCO turnover rates

    Directory of Open Access Journals (Sweden)

    Yaping eWu

    2014-12-01

    Full Text Available Diatoms contribute ~40% of primary production in the modern ocean and encompass the largest cell size range of any phytoplankton group. Diatom cell size influences their nutrient uptake, photosynthetic light capture, carbon export efficiency, and growth responses to increasing pCO2. We therefore examined nitrogen resource allocations to the key protein complexes mediating photosynthesis across six marine centric diatoms, spanning 5 orders of magnitude in cell volume, under past, current and predicted future pCO2 levels, in balanced growth under nitrogen repletion. Membrane bound photosynthetic protein concentrations declined with cell volume in parallel with cellular concentrations of total protein, total nitrogen and chlorophyll. Larger diatom species, however, allocated a greater fraction (by 3.5 fold of their total cellular nitrogen to the soluble RUBISCO carbon fixation complex than did smaller species. Carbon assimilation per unit of RUBISCO large subunit (C RbcL-1 s-1 decreased with cell volume, from ~8 to ~2 C RbcL-1 s-1 from the smallest to the largest cells. Whilst a higher allocation of cellular nitrogen to RUBISCO in larger cells increases the burden upon their nitrogen metabolism, the higher RUBISCO allocation buffers their lower achieved RUBISCO turnover rate to enable larger diatoms to maintain carbon assimilation rates per total protein comparable to small diatoms. Individual species responded to increased pCO2, but cell size effects outweigh pCO2 responses across the diatom species size range examined. In large diatoms a higher nitrogen cost for RUBISCO exacerbates the higher nitrogen requirements associated with light absorption, so the metabolic cost to maintain photosynthesis is a cell size-dependent trait.

  20. Development of a diatom-based multimetric index for acid mine drainage impacted depressional wetlands.

    Science.gov (United States)

    Riato, Luisa; Leira, Manel; Della Bella, Valentina; Oberholster, Paul J

    2018-01-15

    Acid mine drainage (AMD) from coal mining in the Mpumalanga Highveld region of South Africa has caused severe chemical and biological degradation of aquatic habitats, specifically depressional wetlands, as mines use these wetlands for storage of AMD. Diatom-based multimetric indices (MMIs) to assess wetland condition have mostly been developed to assess agricultural and urban land use impacts. No diatom MMI of wetland condition has been developed to assess AMD impacts related to mining activities. Previous approaches to diatom-based MMI development in wetlands have not accounted for natural variability. Natural variability among depressional wetlands may influence the accuracy of MMIs. Epiphytic diatom MMIs sensitive to AMD were developed for a range of depressional wetland types to account for natural variation in biological metrics. For this, we classified wetland types based on diatom typologies. A range of 4-15 final metrics were selected from a pool of ~140 candidate metrics to develop the MMIs based on their: (1) broad range, (2) high separation power and (3) low correlation among metrics. Final metrics were selected from three categories: similarity to reference sites, functional groups, and taxonomic composition, which represent different aspects of diatom assemblage structure and function. MMI performances were evaluated according to their precision in distinguishing reference sites, responsiveness to discriminate reference and disturbed sites, sensitivity to human disturbances and relevancy to AMD-related stressors. Each MMI showed excellent discriminatory power, whether or not it accounted for natural variation. However, accounting for variation by grouping sites based on diatom typologies improved overall performance of MMIs. Our study highlights the usefulness of diatom-based metrics and provides a model for the biological assessment of depressional wetland condition in South Africa and elsewhere. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Diatoms as an indicator of bottom surface sediment dynamics in the southern Scotia sea

    Directory of Open Access Journals (Sweden)

    Олег Сергеевич Огиенко

    2015-05-01

    Full Text Available The study of diatoms from the sediments of the lower interval of column K97-18 in Scotia Sea it is revealed the combination of Late-Holocene and Miocene species in complexes, due to the abundance of inclusions of Middle Miocene diatoms in the rock. Age of re-deposition, transporters and ways of transportation are determined, and it is suggested possible localization of diatomite layers

  2. Fine-grained sheet silicate rocks

    International Nuclear Information System (INIS)

    Weaver, C.E.

    1977-09-01

    Considerable interest has been shown in the possibility of using shales as repositories for radioactive waste and a variety of other waste products, and it appears that over the next few years much money and effort will be expended to investigate and test a wide variety of shales. If shales are to be studied in detail by a large number of investigators, it is important that all concerned have the same concept of what constitutes a shale. The term shale and other terms for fine-grained rocks have been used for many years and have been continually redefined. Most definitions predate the development of modern instrumentation and are based on field observations and intuition; however, the main problem is the diversity of definitions. An attempt is made here to develop a simple, rational classification of fine-grained sediments, and it is hoped that this classification will eliminate some of the present ambiguity. In order that the classification be pertinent, mineral composition and textural data were compiled and evaluated. The data on unconsolidated and consolidated sediments were contrasted and the effects of burial diagenesis assessed. It was found necessary to introduce a new term, physil, to describe all sheet silicate minerals. In contrast to the term clay mineral, the term physil has no size connotation. A simple classification is proposed that is based on the percentage of physils and grain size. In Part II the fine-grained physil rocks are classified on the basis of physil type, non-physil minerals, and texture. Formations are listed which have the mineral and textural characteristics of the most important rock types volumetrically. Selected rock types, and the formations in which they can be found, are recommended for laboratory study to determine their suitability for the storage of high-level radioactive waste

  3. Spring molybdenum enrichment in scallop shells: a potential tracer of diatom productivity in coastal temperate environments (Brittany, NW France)?

    Science.gov (United States)

    Barats, A.; Amouroux, D.; Pécheyran, C.; Chauvaud, L.; Thébault, J.; Donard, O. F. X.

    2009-08-01

    Skeletal molybdenum/calcium ([Mo]/[Ca])shell ratios were recently examined in bivalves. These ratios were determined by quantitative LA-ICP-MS analyses every third daily striae (i.e. a temporal resolution of 3 days) in 36 flat valves of the Great Scallop shells Pecten maximus (2-year old; 3 shells/year) collected in temperate coastal environments of Western Europe (42 to 49° N). Variations of ([Mo]/[Ca])shell ratio were significant and reproducible for scallops from a same population, from different years (1998-2004) and from different coastal temperate locations. ([Mo]/[Ca])shell exhibits typical profiles characterized by a background content, below the method detection limit (<0.003 μmol/mol) for most of the shell growth period, which is punctuated by a significant transient enrichment (0.031-2.1 μmol/mol) mainly occurring from May to June. The Bay of Brest (France) was especially investigated because of long term observations on scallop communities, environmental variables, and high resolution analyses of dissolved Mo in bottom seawater in 2000. In 2000, dissolved Mo exhibited significant increasing concentration just preceding a maximum of ([Mo]/[Ca])shell ratio. The environmental conditions preceding ([Mo]/[Ca])shell maximum events, both in 2000 and over the 7-year survey indicates a direct influence of the scallop environmental conditions at the sediment water interface subsequent to the intense and periodic spring bloom event. Spring maxima of ([Mo]/[Ca])shell ratio were found to be specifically related to the dynamic of spring diatom blooms and to the extent of the subsequent silicate depletion. ([Mo]/[Ca])shell records reveal thus unexpected biogeochemical routes of Mo, potentially related to coastal spring productivity.

  4. Diatoms on the carapace of common snapping turtles: Luticola spp. dominate despite spatial variation in assemblages.

    Directory of Open Access Journals (Sweden)

    Shelly C Wu

    Full Text Available Filamentous algae are often visible on the carapaces of freshwater turtles and these algae are dominated by a few species with varying geographic distributions. Compared to filamentous algae, little is known about the much more speciose microalgae on turtles. Our objectives were to compare the diatom flora on a single turtle species (the common snapping turtle, Chelydra serpentina across part of its range to examine spatial patterns and determine whether specific diatom taxa were consistently associated with turtles (as occurs in the filamentous alga Basicladia spp.. Using preserved turtle specimens from museums, we systematically sampled diatoms on the carapaces of 25 snapping turtles across five states. The diverse diatom assemblages formed two groups-the southern Oklahoma group and the northern Illinois/Wisconsin/New York group, with Arkansas not differing from either group. Of the six diatom species found in all five states, four species are widespread, whereas Luticola cf. goeppertiana and L. cf. mutica are undescribed species, known only from turtles in our study. L. cf. goeppertiana comprised 83% of the diatom abundance on Oklahoma turtles and was relatively more abundant on southern turtles (Oklahoma and Arkansas than on northern turtles (where mean abundance/state was > 10%. L. cf. mutica was the most abundant species (40% on New York turtles. Some Luticola species are apparently turtle associates and results support a pattern of spatial variation in Luticola species, similar to that in Basicladia. Using museum specimens is an efficient and effective method to study the distribution of micro-epibionts.

  5. Diatoms on the carapace of common snapping turtles: Luticola spp. dominate despite spatial variation in assemblages

    Science.gov (United States)

    Wu, Shelly C.; Bergey, Elizabeth A.

    2017-01-01

    Filamentous algae are often visible on the carapaces of freshwater turtles and these algae are dominated by a few species with varying geographic distributions. Compared to filamentous algae, little is known about the much more speciose microalgae on turtles. Our objectives were to compare the diatom flora on a single turtle species (the common snapping turtle, Chelydra serpentina) across part of its range to examine spatial patterns and determine whether specific diatom taxa were consistently associated with turtles (as occurs in the filamentous alga Basicladia spp.). Using preserved turtle specimens from museums, we systematically sampled diatoms on the carapaces of 25 snapping turtles across five states. The diverse diatom assemblages formed two groups–the southern Oklahoma group and the northern Illinois/Wisconsin/New York group, with Arkansas not differing from either group. Of the six diatom species found in all five states, four species are widespread, whereas Luticola cf. goeppertiana and L. cf. mutica are undescribed species, known only from turtles in our study. L. cf. goeppertiana comprised 83% of the diatom abundance on Oklahoma turtles and was relatively more abundant on southern turtles (Oklahoma and Arkansas) than on northern turtles (where mean abundance/state was > 10%). L. cf. mutica was the most abundant species (40%) on New York turtles. Some Luticola species are apparently turtle associates and results support a pattern of spatial variation in Luticola species, similar to that in Basicladia. Using museum specimens is an efficient and effective method to study the distribution of micro-epibionts. PMID:28192469

  6. Accumulation of {sup 241}Am by suspended matter, diatoms and aquatic weeds of the Yenisei River

    Energy Technology Data Exchange (ETDEWEB)

    Zotina, T.A., E-mail: t_zotina@ibp.r [Institute of Biophysics SB RAS, Akademgorodok, Krasnoyarsk 660036 (Russian Federation); Bolsunovsky, A.Ya.; Bondareva, L.G. [Institute of Biophysics SB RAS, Akademgorodok, Krasnoyarsk 660036 (Russian Federation)

    2010-02-15

    In this work we experimentally estimated the capacities of the key components of the Yenisei River (Russia): particulate suspended matter (seston), diatom microalgae, and submerged macrophytes for accumulating {sup 241}Am from water. In our experiments large particles of seston (>8 mum), comparable in size with diatoms, took up most of americium from water. The accumulation of americium by isolated diatom algae (Asterionella formosa and Diatoma vulgare) was lower than by total seston. The concentration factors (CFs) of {sup 241}Am for seston of the Yenisei River in our experiments were (2.8-6.9).10{sup 5}; for diatoms - (1.5-4.2).10{sup 4}. The CFs for aquatic plant Elodea canadensis were within the same order of magnitude as those for diatoms. Activity concentration and CFs of {sup 241}Am were nearly the same in experiments under dark and light conditions. This is indicative of an energy independent mechanism of americium uptake from the water by diatoms and submerged macrophytes.

  7. Biofilm and capsule formation of the diatom Achnanthidium minutissimum are affected by a bacterium.

    Science.gov (United States)

    Windler, Miriam; Leinweber, Katrin; Bartulos, Carolina Rio; Philipp, Bodo; Kroth, Peter G

    2015-04-01

    Photoautotrophic biofilms play an important role in various aquatic habitats and are composed of prokaryotic and/or eukaryotic organisms embedded in extracellular polymeric substances (EPS). We have isolated diatoms as well as bacteria from freshwater biofilms to study organismal interactions between representative isolates. We found that bacteria have a strong impact on the biofilm formation of the pennate diatom Achnanthidium minutissimum. This alga produces extracellular capsules of insoluble EPS, mostly carbohydrates (CHO), only in the presence of bacteria (xenic culture). The EPS themselves also have a strong impact on the aggregation and attachment of the algae. In the absence of bacteria (axenic culture), A. minutissimum did not form capsules and the cells grew completely suspended. Fractionation and quantification of CHO revealed that the diatom in axenic culture produces large amounts of soluble CHO, whereas in the xenic culture mainly insoluble CHO were detected. For investigation of biofilm formation by A. minutissimum, a bioassay was established using a diatom satellite Bacteroidetes bacterium that had been shown to induce capsule formation of A. minutissimum. Interestingly, capsule and biofilm induction can be achieved by addition of bacterial spent medium, indicating that soluble hydrophobic molecules produced by the bacterium may mediate the diatom/bacteria interaction. With the designed bioassay, a reliable tool is now available to study the chemical interactions between diatoms and bacteria with consequences for biofilm formation. © 2015 Phycological Society of America.

  8. Marennine, Promising Blue Pigments from a Widespread Haslea Diatom Species Complex

    Directory of Open Access Journals (Sweden)

    Romain Gastineau

    2014-05-01

    Full Text Available In diatoms, the main photosynthetic pigments are chlorophylls a and c, fucoxanthin, diadinoxanthin and diatoxanthin. The marine pennate diatom Haslea ostrearia has long been known for producing, in addition to these generic pigments, a water-soluble blue pigment, marennine. This pigment, responsible for the greening of oysters in western France, presents different biological activities: allelopathic, antioxidant, antibacterial, antiviral, and growth-inhibiting. A method to extract and purify marennine has been developed, but its chemical structure could hitherto not be resolved. For decades, H. ostrearia was the only organism known to produce marennine, and can be found worldwide. Our knowledge about H. ostrearia-like diatom biodiversity has recently been extended with the discovery of several new species of blue diatoms, the recently described H. karadagensis, H. silbo sp. inedit. and H. provincialis sp. inedit. These blue diatoms produce different marennine-like pigments, which belong to the same chemical family and present similar biological activities. Aside from being a potential source of natural blue pigments, H. ostrearia-like diatoms thus present a commercial potential for aquaculture, cosmetics, food and health industries.

  9. Spectral radiation dependent photoprotective mechanism in the diatom Pseudo-nitzschia multistriata.

    Directory of Open Access Journals (Sweden)

    Christophe Brunet

    Full Text Available Phytoplankton, such as diatoms, experience great variations of photon flux density (PFD and light spectrum along the marine water column. Diatoms have developed some rapidly-regulated photoprotective mechanisms, such as the xanthophyll cycle activation (XC and the non-photochemical chlorophyll fluorescence quenching (NPQ, to protect themselves from photooxidative damages caused by excess PFD. In this study, we investigate the role of blue fluence rate in combination with red radiation in shaping photoacclimative and protective responses in the coastal diatom Pseudo-nitzschia multistriata. This diatom was acclimated to four spectral light conditions (blue, red, blue-red, blue-red-green, each of them provided with low and high PFD. Our results reveal that the increase in the XC pool size and the amplitude of NPQ is determined by the blue fluence rate experienced by cells, while cells require sensing red radiation to allow the development of these processes. Variations in the light spectrum and in the blue versus red radiation modulate either the photoprotective capacity, such as the activation of the diadinoxanthin-diatoxanthin xanthophyll cycle, the diadinoxanthin de-epoxidation rate and the capacity of non-photochemical quenching, or the pigment composition of this diatom. We propose that spectral composition of light has a key role on the ability of diatoms to finely balance light harvesting and photoprotective capacity.

  10. COMPARISON OF SOL-GEL SILICATE COATINGS ON Ti SUBSTRATE

    Directory of Open Access Journals (Sweden)

    DIANA HORKAVCOVÁ

    2012-12-01

    Full Text Available The objective of the submitted work was to prepare and to characterize two types of silicate coatings prepared by the sol-gel method using the dip-coating technique on a titanium substrate. Efforts have been made to use mechanical properties of bio-inert titanium and bioactive properties of a silicate layer enriched with an admixture of compounds identified below. The first group consisted of silicate coatings containing silver, brushite and monetite. The other group of silicate coatings contained calcium nitrate and triethyl phosphate. Mechanically and chemically treated titanium substrates were dipped into sols and dried and fired. Silicate coatings from the first group were also chemically treated in 10 mol.l-1 solution of sodium hydroxide. All coatings were measured to determine their adhesive and bioactive properties and furthermore the antibacterial properties were tested in the case of first group. Surfaces of the coated substrates were investigated after the firing and after the individual tests with optical and electron microscopy and X-ray microdiffraction. A tape test demonstrated excellent adhesive property of all coatings to the substrate, classified with degree 5. A static in vitro test demonstrated bioactivity of nearly all the coatings. The basic silicate coating from the first group and one type of coating from the second group were identified as inert. Antibacterial properties of silicate coatings containing silver showed to be different when tested against Escherichia coli bacteria. A complete inhibition of the growth of bacteria under our experimental conditions was observed for the coating containing silver and monetite and a partial inhibition of the growth of bacteria for coatings containing silver and silver in combination with brushite.

  11. Probing physics beyond the standard model in diatomic molecules

    International Nuclear Information System (INIS)

    Denis, M.

    2017-01-01

    Nowadays, the incompleteness of the Standard Model of particles (SM) is largely acknowledged. One of its most obvious shortcomings is the lack of explanation for the huge surplus of matter over antimatter in the universe, the so-called baryon asymmetry of the universe. New CP (charge conjugation and spatial parity) violations absent in the SM are assumed to be responsible for this asymmetry. Such a violation could be observed, in ordinary matter through a set of interactions violating both parity and time-reversal symmetries (P, T -odd) among which the preponderant ones are the electron Electric Dipole Moment (eEDM), the electron-nucleon scalar-pseudoscalar (enSPS) and the nuclear magnetic quadrupole moment (nMQM) interactions. Hence, an experimental evidence of a non-zero P, T -odd interaction constant would be a probe of this New Physics beyond the Standard Model. The calculation of the corresponding molecular parameters is performed by making use of an elaborate four-component relativistic configuration interaction approach in polar diatomic molecules containing an actinide, that are particularly adequate systems for eEDM experiments, such as ThO that allowed for assigning the most constraining upper bound on the eEDM and ThF"+ that will be used in a forthcoming experiment. Those results will be of crucial importance in the interpretation of the measurements since the fundamental constants can only be evaluated if one combines both experimental energy shift measurements and theoretical molecular parameters. This manuscript proceeds as follows, after an introduction to the general background of the search of CP-violations and its consequences for the understanding of the Universe (Chapter 1), a presentation of the underlying theory of the evidence of such violation in ordinary matter, namely the P, T -odd sources of the Electric Dipole Moment of a many-electron system, as well as the relevant molecular parameters is given in Chapter 2. A similar introduction to

  12. Diatom paleoecology Pass Key core 37, Everglades National Park, Florida Bay

    Science.gov (United States)

    Pyle, Laura; Cooper, S.R.; Huvane, J.K.

    1998-01-01

    During the 20th century, there have been large-scale anthropogenic modifications to the South Florida ecosystem. The effects of these changes on Florida Bay and its biological communities are currently of political and scientific interest. This study is part of a larger effort to reconstruct the history of environmental changes in the bay, using paleoecological techniques. We are using diatom indicators preserved in Florida Bay sediments to infer long-term water quality, productivity, nutrient, and salinity changes. We are also obtaining information concerning the natural variability of the ecosystem. Diatoms are microscopic algae, the remains of which are generally well preserved in sediments, and their distributions are closely linked to water quality. Diatoms were extracted from a 70-cm sediment core collected from the Pass Key mudbank of Florida Bay by the U.S. Geological Survey. Between 300-500 diatom valves from each of 15 core samples were identified and counted. Estimates of absolute abundance, species richness, Shannon-Wiener diversity, and centric:pennate ratios were calculated for each sample that was counted. Information on the ecology of the diatom species is presented, and changes in diatom community composition are evaluated. Samples contained an average of four million diatom valves per gram of sediment. Major changes in the diatom community are evident down core. These include increases in the percent abundance of marine diatoms in the time period represented by the core, probably the result of increasing salinity at Pass Key. Benthic diatoms become less abundant in the top half of the core. This may be related to a number of factors including the die-off of sea grass beds or increased turbidity of the water column. Once the chronology of the Pass Key core 37 is established, these down-core changes can be related to historical events and compared with other indicators in the sedimentary record that are currently being investigated by U.S Geological

  13. Diatoms as a fingerprint of sub-catchment contributions to meso-scale catchment runoff

    Science.gov (United States)

    Klaus, Julian; Wetzel, Carlos E.; Martinez-Carreras, Nuria; Ector, Luc; Pfister, Laurent

    2014-05-01

    In recent years, calls were made for new eco-hydrological approaches to improve understanding of hydrological processes. Recently diatoms, one of the most common and diverse algal groups that can be easily transported by flowing water due to their small size (~10-200 µm), were used to detect the onset and cessation of surface runoff to small headwater streams and constrain isotopic and hydro-chemical hydrograph separation methods. While the method showed its potential in the hillslope-riparian zone-stream continuum of headwater catchments, the behavior of diatoms and their use for hydrological process research in meso-scale catchments remains uncertain. Diatoms can be a valuable support for isotope and hydro-chemical tracer methods when these become ambiguous with increasing scale. Distribution and abundance of diatom species is controlled by various environmental factors (pH, soil type, moisture conditions, exposition to sunlight, etc.). We therefore hypothesize that species abundance and composition can be used as a proxy for source areas. This presentation evaluates the potential for diatoms to trace source-areas in the nested meso-scale Attert River basin (250 km2, Luxembourg, Europe). We sampled diatom populations in streamwater during one flood event in Fall 2011 in 6 sub-catchments and the basin outlet - 17 to 28 samples/catchment for the different sampling locations. Diatoms were classified and counted in every individual sample. In total more than 400 diatom species were detected. Ordination analysis revealed a clear distinction between communities sampled in different sub-catchments. The species composition at the catchment outlet reflects a mixing of the diatom composition originating from different sub-catchments. This data suggests that diatoms indeed can reflect the geographic origin of stream water at the catchment outlet. The centroids of the ordination analysis might be linked to the physiographic characteristics (geology and land use) of the

  14. A subsurface Fe-silicate weathering microbiome

    Science.gov (United States)

    Napieralski, S. A.; Buss, H. L.; Roden, E. E.

    2017-12-01

    Traditional models of microbially mediated weathering of primary Fe-bearing minerals often invoke organic ligands (e.g. siderophores) used for nutrient acquisition. However, it is well known that the oxidation of Fe(II) governs the overall rate of Fe-silicate mineral dissolution. Recent work has demonstrated the ability of lithtrophic iron oxidizing bacteria (FeOB) to grow via the oxidation of structural Fe(II) in biotite as a source of metabolic energy with evidence suggesting a direct enzymatic attack on the mineral surface. This process necessitates the involvement of dedicated outer membrane proteins that interact with insoluble mineral phases in a process known as extracellular electron transfer (EET). To investigate the potential role FeOB in a terrestrial subsurface weathering system, samples were obtained from the bedrock-saprolite interface (785 cm depth) within the Rio Icacos Watershed of the Luquillo Mountains in Puerto Rico. Prior geochemical evidence suggests the flux of Fe(II) from the weathering bedrock supports a robust lithotrophic microbial community at depth. Current work confirms the activity of microorganism in situ, with a marked increase in ATP near the bedrock-saprolite interface. Regolith recovered from the interface was used as inoculum to establish enrichment cultures with powderized Fe(II)-bearing minerals serving as the sole energy source. Monitoring of the Fe(II)/Fe(total) ratio and ATP generation suggests growth of microorganisms coupled to the oxidation of mineral bound Fe(II). Analysis of 16S rRNA gene and shotgun metagenomic libraries from in situ and enrichment culture samples lends further support to FeOB involvement in the weathering process. Multiple metagenomic bins related to known FeOB, including Betaproteobacteria genera, contain homologs to model EET systems, including Cyc2 and MtoAB. Our approach combining geochemistry and metagenomics with ongoing microbiological and genomic characterization of novel isolates obtained

  15. Deep-Earth Equilibration between Molten Iron and Solid Silicates

    Science.gov (United States)

    Brennan, M.; Zurkowski, C. C.; Chidester, B.; Campbell, A.

    2017-12-01

    Elemental partitioning between iron-rich metals and silicate minerals influences the properties of Earth's deep interior, and is ultimately responsible for the nature of the core-mantle boundary. These interactions between molten iron and solid silicates were influential during planetary accretion, and persist today between the mantle and liquid outer core. Here we report the results of diamond anvil cell experiments at lower mantle conditions (40 GPa, >2500 K) aimed at examining systems containing a mixture of metals (iron or Fe-16Si alloy) and silicates (peridotite). The experiments were conducted at pressure-temperature conditions above the metallic liquidus but below the silicate solidus, and the recovered samples were analyzed by FIB/SEM with EDS to record the compositions of the coexisting phases. Each sample formed a three-phase equilibrium between bridgmanite, Fe-rich metallic melt, and an oxide. In one experiment, using pure Fe, the quenched metal contained 6 weight percent O, and the coexisting oxide was ferropericlase. The second experiment, using Fe-Si alloy, was highly reducing; its metal contained 10 wt% Si, and the coexisting mineral was stishovite. The distinct mineralogies of the two experiments derived from their different starting metals. These results imply that metallic composition is an important factor in determining the products of mixed phase iron-silicate reactions. The properties of deep-Earth interfaces such as the core-mantle boundary could be strongly affected by their metallic components.

  16. Heterogeneous nucleation of protein crystals on fluorinated layered silicate.

    Directory of Open Access Journals (Sweden)

    Keita Ino

    Full Text Available Here, we describe an improved system for protein crystallization based on heterogeneous nucleation using fluorinated layered silicate. In addition, we also investigated the mechanism of nucleation on the silicate surface. Crystallization of lysozyme using silicates with different chemical compositions indicated that fluorosilicates promoted nucleation whereas the silicates without fluorine did not. The use of synthesized saponites for lysozyme crystallization confirmed that the substitution of hydroxyl groups contained in the lamellae structure for fluorine atoms is responsible for the nucleation-inducing property of the nucleant. Crystallization of twelve proteins with a wide range of pI values revealed that the nucleation promoting effect of the saponites tended to increase with increased substitution rate. Furthermore, the saponite with the highest fluorine content promoted nucleation in all the test proteins regardless of their overall net charge. Adsorption experiments of proteins on the saponites confirmed that the density of adsorbed molecules increased according to the substitution rate, thereby explaining the heterogeneous nucleation on the silicate surface.

  17. Relationships between mineralization and silicic volcanism in the central Andes

    Energy Technology Data Exchange (ETDEWEB)

    Francis, P.W.; Halls, C.; Baker, M.C.W.

    1983-10-01

    Studies of late Tertiary silicic volcanic centers in the Western and Eastern Cordilleras of the Central Andes show that three volcanic environments are appropriate sites for mineralization: (1) ring-fracture extrusions post-dating large calderas; (2) similar extrusions within ignimbrite shields; and (3) isolated, small silicic volcanoes. Subvolcanic tin mineralization in the Eastern Cordillera is located in silicic stocks and associated breccias of Miocene age. The Cerro Rico stock, Potosi, Bolivia, contains tin and silver mineralization and has an intrusion age apparently millions of years younger than that of the associated Kari Kari caldera. Similar age relationships between mineralization and caldera formation have been described from the San Juan province, Colorado. The vein deposits of Chocaya, southern Bolivia, were emplaced in the lower part of an ignimbrite shield, a type of volcanic edifice as yet unrecognized in comparable areas of silicic volcanism. The El Salvador porphyry copper deposit, Chile, is related to silicic stocks which may have been intruded along a caldera ring fracture. Existing models for the genesis of porphyry copper deposits suggest that they formed in granodioritic stocks located in the infrastructure of andesitic stratovolcanoes. The dome of La Soufriere, Guadeloupe is proposed as a modern analog for the surface expression of subvolcanic mineralization processes, the phreatic eruptions there suggesting the formation of hydrothermal breccia bodies in depth.

  18. Quantum entanglement and the dissociation process of diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Esquivel, Rodolfo O; Molina-Espiritu, Moyocoyani [Departamento de Quimica, Universidad Autonoma Metropolitana, 09340-Mexico DF (Mexico); Flores-Gallegos, Nelson [Unidad Profesional Interdisciplinaria de IngenierIa, Campus Guanajuato del Instituto Politecnico Nacional, 36275-Guanajuato (Mexico); Plastino, A R; Angulo, Juan Carlos; Dehesa, Jesus S [Instituto Carlos I de Fisica Teorica y Computacional, and Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, 18071-Granada (Spain); Antolin, Juan, E-mail: esquivel@xanum.uam.mx, E-mail: arplastino@ugr.es [Departamento de Fisica Aplicada, EUITIZ, Universidad de Zaragoza, 50018-Zaragoza (Spain)

    2011-09-14

    In this work, we investigate quantum entanglement-related aspects of the dissociation process of some selected, representative homo- and heteronuclear diatomic molecules. This study is based upon high-quality ab initio calculations of the (correlated) molecular wavefunctions involved in the dissociation processes. The values of the electronic entanglement characterizing the system in the limit cases corresponding to (i) the united-atom representation and (ii) the asymptotic region when atoms dissociate are discussed in detail. It is also shown that the behaviour of the electronic entanglement as a function of the reaction coordinate R exhibits remarkable correspondences with the phenomenological description of the physically meaningful regimes comprising the processes under study. In particular, the extrema of the total energies and the electronic entanglement are shown to be associated with the main physical changes experienced by the molecular spatial electronic density, such as charge depletion and accumulation or bond cleavage regions. These structural changes are characterized by several selected descriptors of the density, such as the Laplacian of the electronic molecular distributions (LAP), the molecular electrostatic potential (MEP) and the atomic electric potentials fitted to the MEP.

  19. Heat conduction in diatomic chains with correlated disorder

    Science.gov (United States)

    Savin, Alexander V.; Zolotarevskiy, Vadim; Gendelman, Oleg V.

    2017-01-01

    The paper considers heat transport in diatomic one-dimensional lattices, containing equal amounts of particles with different masses. Ordering of the particles in the chain is governed by single correlation parameter - the probability for two neighboring particles to have the same mass. As this parameter grows from zero to unity, the structure of the chain varies from regular staggering chain to completely random configuration, and then - to very long clusters of particles with equal masses. Therefore, this correlation parameter allows a control of typical cluster size in the chain. In order to explore different regimes of the heat transport, two interatomic potentials are considered. The first one is an infinite potential wall, corresponding to instantaneous elastic collisions between the neighboring particles. In homogeneous chains such interaction leads to an anomalous heat transport. The other one is classical Lennard-Jones interatomic potential, which leads to a normal heat transport. The simulations demonstrate that the correlated disorder of the particle arrangement does not change the convergence properties of the heat conduction coefficient, but essentially modifies its value. For the collision potential, one observes essential growth of the coefficient for fixed chain length as the limit of large homogeneous clusters is approached. The thermal transport in these models remains superdiffusive. In the Lennard-Jones chain the effect of correlation appears to be not monotonous in the limit of low temperatures. This behavior stems from the competition between formation of long clusters mentioned above, and Anderson localization close to the staggering ordered state.

  20. Scattering and stopping of swift diatomic molecules under Coulomb explosion

    International Nuclear Information System (INIS)

    Sigmund, P.

    1992-01-01

    The scattering and stopping of the fragments of a fast diatomic molecule under Coulomb explosion has been analysed theoretically. The central assumption in the scheme is the dominance of Coulomb explosion, while electronic stopping (including wake forces) and elastic scattering are treated as perturbations. Charge exchange has been neglected. Coulomb images of penetration phenomena are heavily distorted. For small penetrated layer thicknesses, images appear contracted in the direction of the molecular axis, and expanded perpendicular to it. This distortion is described quantitatively by a linear transformation. General expressions have been derived for the effect of continuous and stochastic forces on the distribution of fragment velocities from Coulomb explosion (the ''ring pattern''). Moreover, relations have been found that allow to scale velocity distributions valid in the absence of Coulomb explosion into distributions allowing for Coulomb explosion. Applications concern the shift in ring pattern due to electronic stopping, the lateral broadening due to multiple scattering, and the effect of zero-point motion on the Coulomb image of a molecule. (orig.)

  1. Steady-state growth of the marine diatom Thalassiosira pseudonana

    International Nuclear Information System (INIS)

    Olson, R.J.; SooHoo, J.B.; Kiefer, D.A.

    1980-01-01

    Seasonal studies of the vertical distribution of nitrate, nitrite, and phytoplankton in the oceans and studies using 15 N as a tracer of nitrate metabolism indicate that the reduction of nitrate by phytoplankton is a source of nitrite in the upper waters of the ocean. To better understand this process, the relationship between nitrate uptake and nitrite production has been examined with continuous cultures of the small marine diatom Thalassiosira pseudonana. In a turbidostat culture, the rates of nitrite production by T. Pseudonana increase with light intensity. This process is only loosely coupled to rates of nitrate assimilation since the ratio of net nitrite production to total nitrate assimilation increases with increased rates of growth. In continuous cultures where steady-state concentrations of nitrate and nitrite were varied, T. pseudonana produced nitrite at rates which increased with increasing concentrations of nitrate. Again, the rates of nitrite production were uncoupled from rates of nitrate assimilation. The study was used to derive a mathematical description of nitrate and nitrite metabolism by T. pseudonana. The validity of this model was supported by the results of a study in which 15 N-labeled nitrite was introduced into the continuous culture, and the model was used to examine patterns in distribution of nitrite in the Antarctic Ocean and the Sargasso Sea

  2. Scattering and stopping of swift diatomic molecules under Coulomb explosion

    International Nuclear Information System (INIS)

    Sigmund, P.

    1991-01-01

    The scattering and stopping of the fragments of a fast diatomic molecule under Coulomb explosion has been analyzed theoretically. The central assumption in the scheme is the dominance of Coulomb explosion, while electronic stopping (including wake forces) and elastic scattering are treated as perturbations. Charge exchange has been neglected. Coulomb images of penetration phenomena are heavily distorted. For small penetrated layer thicknesses, images appear contracted in the direction of the molecular axis, and expanded perpendicular to it. This distortion is described quantitatively by a linear transformation. General expressions have been derived for the effect of continuous and stochastic forces on the distribution of fragment velocities from Coulomb explosion (the ''ring pattern''). Moreover, relations have been found that allow to scale velocity distributions valid in the absence of Coulomb explosion into distributions allowing for Coulomb explosion. Applications concern the shift in ring pattern due to electronic stopping, the lateral broadening due to multiple scattering and the effect of zero-point motion on the Coulomb image of a molecule. 14 refs., 5 figs

  3. Response of the marine diatom Thalassiosira weissflogii to iron stress

    International Nuclear Information System (INIS)

    Harrison, G.I.; Morel, F.M.M.

    1986-01-01

    The coastal diatom Thalassiosira weissflogii responds to iron limitation with decreasing growth rate, decreasing quotas of cellular iron, and increasing rates of maximum short term uptake. Growth response to steady iron limitation can be modeled according to the equations of Droop and Monod. The cellular iron quota varies from about 2 to 25 x 10 -1 mol iron per liter-cell with increasing iron; the half-saturation constant for growth, Kμ, is 1.1 x 10 -21 M (free ferric ion). In contrast, the half-saturation constant for 59 I iron uptake, K/sub rho/ is about 3 x 10 -19 M; the maximum iron uptake rate (rho/sub max/) is increased several-fold under iron limitation, resulting in a potential short term uptake rate that is a few hundred times the steady state rate. At a fixed concentration of free manganese ion, the cellular manganese quota is increased several-fold in iron-limited cultures compared to iron-sufficient cultures

  4. Behavior of the Position-Spread Tensor in Diatomic Systems.

    Science.gov (United States)

    Brea, Oriana; El Khatib, Muammar; Angeli, Celestino; Bendazzoli, Gian Luigi; Evangelisti, Stefano; Leininger, Thierry

    2013-12-10

    The behavior of the Position-Spread Tensor (Λ) in a series of light diatomic molecules (either neutral or negative ions) is investigated at a Full Configuration Interaction level. This tensor, which is the second moment cumulant of the total position operator, is invariant with respect to molecular translations, while its trace is also rotationally invariant. Moreover, the tensor is additive in the case of noninteracting subsystems and can be seen as an intrinsic property of a molecule. In the present work, it is shown that the longitudinal component of the tensor, Λ∥, which is small for internuclear distances close to the equilibrium, tends to grow if the bond is stretched. A maximum is reached in the region of the bond breaking, then Λ∥ decreases and converges toward the isolated-atom value. The degenerate transversal components, Λ⊥, on the other hand, usually have a monotonic growth toward the atomic value. The Position Spread is extremely sensitive to reorganization of the molecular wave function, and it becomes larger in the case of an increase of the electron mobility, as illustrated by the neutral-ionic avoided crossing in LiF. For these reasons, the Position Spread can be an extremely useful property that characterizes the nature of the wave function in a molecular system.

  5. Heat conduction in diatomic chains with correlated disorder

    Energy Technology Data Exchange (ETDEWEB)

    Savin, Alexander V., E-mail: asavin@center.chph.ras.ru [Semenov Institute of Chemical Physics, Russian Academy of Sciences, 4 Kosygin str., 119991 Moscow (Russian Federation); Zolotarevskiy, Vadim; Gendelman, Oleg V. [Faculty of Mechanical Engineering, Technion – Israel Institute of Technology, Haifa 32000 (Israel)

    2017-01-23

    The paper considers heat transport in diatomic one-dimensional lattices, containing equal amounts of particles with different masses. Ordering of the particles in the chain is governed by single correlation parameter – the probability for two neighboring particles to have the same mass. As this parameter grows from zero to unity, the structure of the chain varies from regular staggering chain to completely random configuration, and then – to very long clusters of particles with equal masses. Therefore, this correlation parameter allows a control of typical cluster size in the chain. In order to explore different regimes of the heat transport, two interatomic potentials are considered. The first one is an infinite potential wall, corresponding to instantaneous elastic collisions between the neighboring particles. In homogeneous chains such interaction leads to an anomalous heat transport. The other one is classical Lennard–Jones interatomic potential, which leads to a normal heat transport. The simulations demonstrate that the correlated disorder of the particle arrangement does not change the convergence properties of the heat conduction coefficient, but essentially modifies its value. For the collision potential, one observes essential growth of the coefficient for fixed chain length as the limit of large homogeneous clusters is approached. The thermal transport in these models remains superdiffusive. In the Lennard–Jones chain the effect of correlation appears to be not monotonous in the limit of low temperatures. This behavior stems from the competition between formation of long clusters mentioned above, and Anderson localization close to the staggering ordered state.

  6. Deceleration and Trapping of Heavy Diatomic Molecules for Precision Measurements

    Science.gov (United States)

    Berg, J. E. Van Den; Turkesteen, S. N. Hoekman; Prinsen, E. B.; Hoekstra, S.

    2011-06-01

    We are setting up a novel type of Stark-decelerator optimized for the deceleration and trapping of heavy diatomic molecules. Aim of these experiments is to prepare a trapped sample of ultracold molecules for precision studies of fundamental symmetries. The decelerator uses ring-shaped electrodes to create a moving trapping potential, a prototype of which has been shown to work for CO molecules. Molecules can be decelerated and trapped in the weak-field seeking part of excited rotational states. The alkaline-earth monohalide molecules (currently we focus on the SrF molecule) are prime candidates for next generation parity violation and electron-EDM studies. We plan to combine the Stark deceleration with molecular laser cooling to create a trapped sample of molecules at a final temperature of ˜ 200 μK. A. Osterwalder, S. A. Meek, G. Hammer, H. Haak and G. Meijer Phys. Rev. A 81 (51401), 2010. T. A. Isaev, S. Hoekstra, R. Berger Phys. Rev. A 82 (52521), 2010

  7. The Diatom Staurosirella pinnata for Photoactive Material Production.

    Directory of Open Access Journals (Sweden)

    Roberta De Angelis

    Full Text Available A native isolate of the colonial benthic diatom Staurosirella pinnata was cultivated for biosilica production. The silicified cell walls (frustules were used as a source of homogeneous and structurally predictable porous biosilica for dye trapping and random laser applications. This was coupled with the extraction of lipids from biomass showing potential to fabricate photoactive composite materials sustainably. The strain was selected for its ease of growth in culture and harvesting. Biosilica and lipids were obtained at the end of growth in indoor photobioreactors. Frustules were structurally characterized microscopically and their chemistry analyzed with Fourier Transform Infrared Spectroscopy. Frustule capacity of binding laser dyes was evaluated on a set of frustules/Rhodamine B (Rho B solutions and with respect to silicon dioxide and diatomite by Fluorescence Spectroscopy demonstrating a high affinity for the organic dye. The effect of dye trapping property in conveying Rho B emission to frustules, with enhancement of scattering events, was analyzed on Rho B doped polyacrylamide gels filled or not with frustules. Amplified spontaneous emission was recorded at increasing pump power indicating the onset of a random laser effect in frustule filled gels at lower power threshold compared to unfilled matrices.

  8. The Diatom Staurosirella pinnata for Photoactive Material Production

    Science.gov (United States)

    Prosposito, Paolo; Casalboni, Mauro; Lamastra, Francesca Romana; Nanni, Francesca; Congestri, Roberta

    2016-01-01

    A native isolate of the colonial benthic diatom Staurosirella pinnata was cultivated for biosilica production. The silicified cell walls (frustules) were used as a source of homogeneous and structurally predictable porous biosilica for dye trapping and random laser applications. This was coupled with the extraction of lipids from biomass showing potential to fabricate photoactive composite materials sustainably. The strain was selected for its ease of growth in culture and harvesting. Biosilica and lipids were obtained at the end of growth in indoor photobioreactors. Frustules were structurally characterized microscopically and their chemistry analyzed with Fourier Transform Infrared Spectroscopy. Frustule capacity of binding laser dyes was evaluated on a set of frustules/Rhodamine B (Rho B) solutions and with respect to silicon dioxide and diatomite by Fluorescence Spectroscopy demonstrating a high affinity for the organic dye. The effect of dye trapping property in conveying Rho B emission to frustules, with enhancement of scattering events, was analyzed on Rho B doped polyacrylamide gels filled or not with frustules. Amplified spontaneous emission was recorded at increasing pump power indicating the onset of a random laser effect in frustule filled gels at lower power threshold compared to unfilled matrices. PMID:27828985

  9. Shared Epizoic Taxa and Differences in Diatom Community Structure Between Green Turtles (Chelonia mydas) from Distant Habitats.

    Science.gov (United States)

    Majewska, Roksana; de Vijver, Bart Van; Nasrolahi, Ali; Ehsanpour, Maryam; Afkhami, Majid; Bolaños, Federico; Iamunno, Franco; Santoro, Mario; De Stefano, Mario

    2017-11-01

    The first reports of diatoms growing on marine mammals date back to the early 1900s. However, only recently has direct evidence been provided for similar associations between diatoms and sea turtles. We present a comparison of diatom communities inhabiting carapaces of green turtles Chelonia mydas sampled at two remote sites located within the Indian (Iran) and Atlantic (Costa Rica) Ocean basins. Diatom observations and counts were carried out using scanning electron microscopy. Techniques involving critical point drying enabled observations of diatoms and other microepibionts still attached to sea turtle carapace and revealed specific aspects of the epizoic community structure. Species-poor, well-developed diatom communities were found on all examined sea turtles. Significant differences between the two host sea turtle populations were observed in terms of diatom abundance and their community structure (including growth form structure). A total of 12 and 22 diatom taxa were found from sea turtles in Iran and Costa Rica, respectively, and eight of these species belonging to Amphora, Chelonicola, Cocconeis, Navicula, Nitzschia and Poulinea genera were observed in samples from both locations. Potential mechanisms of diatom dispersal and the influence of the external environment, sea turtle behaviour, its life stage, and foraging and breeding habitats, as well as epibiotic bacterial flora on epizoic communities, are discussed.

  10. Diatoms of the jukskei-crocodile river system (transvaal, republic of South Africa): a preliminary check list

    CSIR Research Space (South Africa)

    Schoeman, FR

    1982-01-01

    Full Text Available : V & R Printers. SCHOEMAN, F. R., 1976. Diatom indicator groups in the assessment of water quality in the Jukskei-Crocodile River system (Transvaal, Republic of South Afri ca). J. Limnol. Soc. yth. Afr. 2: 21?24. SCHOEMAN, F. R., 1979. Diatoms... groups of diatom spe cies have been successfully used as an index of the quality of running waters (Lange-Bertalot, 1978a; 1979a; 1979b; Schoeman, 1976; 1979). However, the successful determination of water quality using diatoms as indicators...

  11. Biological monitoring of lotic ecosystems: the role of diatoms Biomonitoramento dos ecossistemas lóticos: o papel das diatomáceas

    Directory of Open Access Journals (Sweden)

    T. Bere

    2010-08-01

    Full Text Available Increasing anthropogenic influence on lotic environments as a result of civilisation has captured public interest because of the consequent problems associated with deterioration of water quality. Various biological monitoring methods that provide a direct measure of ecological integrity by using the response of biota to environmental changes have been developed to monitor the ecological status of lotic environments. Diatoms have been used extensively in this regard and this review attempts to summarise the basic concepts associated with biological monitoring using benthic diatoms. Where possible, examples from work carried out in Brazil are used.O aumento da influência antropogênica sobre ambientes lóticos como resultado da civilização conquistou o interesse público por causa de problemas relacionados com a consequente deterioração da qualidade da água. Vários métodos de biomonitoramento que fornecem uma medida direta da integridade ecológica usando a resposta da biota a alterações ambientais têm sido desenvolvidos para monitorar o estado ecológico de ecossistemas lóticos. Diatomáceas têm sido amplamente utilizadas e esta revisão tenta resumir os conceitos básicos associados ao monitoramento biológico utilizando diatomáceas bentônicas. Sempre que possível, exemplos de trabalhos realizados no Brasil serão utilizados.

  12. Static vs dynamic settlement and adhesion of diatoms to ship hull coatings.

    Science.gov (United States)

    Zargiel, Kelli A; Swain, Geoffrey W

    2014-01-01

    Many experiments utilize static immersion tests to evaluate the performance of ship hull coatings. These provide valuable data; however, they do not accurately represent the conditions both the hull and fouling organisms encounter while a ship is underway. This study investigated the effect of static and dynamic immersion on the adhesion and settlement of diatoms to one antifouling coating (BRA 640), four fouling-release coatings (Intersleek(®) 700, Intersleek(®) 900, Hempasil X3, and Dow Corning 3140) and one standard surface (Intergard(®) 240 Epoxy). Differences in community composition were observed between the static and dynamic treatments. Achnanthes longipes was present on all coatings under static immersion, but was not present under dynamic immersion. This was also found for diatoms in the genera Bacillaria and Gyrosigma. Melosira moniformis was the only diatom present under dynamic conditions, but not static conditions. Several common fouling diatom genera were present on panels regardless of treatment: Amphora, Cocconeis, Entomoneis Cylindrotheca, Licmophora, Navicula, Nitzschia, Plagiotropis, and Synedra. Biofilm adhesion, diatom abundance and diatom diversity were found to be significantly different between static and dynamic treatments; however, the difference was dependent on coating and sampling date. Several coatings (Epoxy, DC 3140 and IS 700) had significantly higher biofilm adhesion on dynamically treated panels on at least one of the four sampling dates, while all coatings had significantly higher diatom abundance on at least one sampling date. Diversity was significantly greater on static panels than dynamic panels for Epoxy, IS 700 and HX3 at least once during the sampling period. The results demonstrate how hydrodynamic stress will significantly influence the microfouling community. Dynamic immersion testing is required to fully understand how antifouling surfaces will respond to biofilm formation when subjected to the stresses experienced

  13. Insights into global diatom distribution and diversity in the world’s ocean

    KAUST Repository

    Malviya, Shruti; Scalco, Eleonora; Audic, Sté phane; Vincent, Flora; Veluchamy, Alaguraj; Poulain, Julie; Wincker, Patrick; Iudicone, Daniele; de Vargas, Colomban; Bittner, Lucie; Zingone, Adriana; Bowler, Chris

    2016-01-01

    Diatoms (Bacillariophyta) constitute one of the most diverse and ecologically important groups of phytoplankton. They are considered to be particularly important in nutrient-rich coastal ecosystems and at high latitudes, but considerably less so in the oligotrophic open ocean. The Tara Oceans circumnavigation collected samples from a wide range of oceanic regions using a standardized sampling procedure. Here, a total of ∼12 million diatom V9-18S ribosomal DNA (rDNA) ribotypes, derived from 293 sizefractionated plankton communities collected at 46 sampling sites across the global ocean euphotic zone, have been analyzed to explore diatom global diversity and community composition. We provide a new estimate of diversity of marine planktonic diatoms at 4,748 operational taxonomic units (OTUs). Based on the total assigned ribotypes, Chaetoceros was the most abundant and diverse genus, followed by Fragilariopsis, Thalassiosira, and Corethron. We found only a few cosmopolitan ribotypes displaying an even distribution across stations and high abundance, many of which could not be assigned with confidence to any known genus. Three distinct communities from South Pacific, Mediterranean, and Southern Ocean waters were identified that share a substantial percentage of ribotypes within them. Sudden drops in diversity were observed at Cape Agulhas, which separates the Indian and Atlantic Oceans, and across the Drake Passage between the Atlantic and Southern Oceans, indicating the importance of these ocean circulation choke points in constraining diatom distribution and diversity. We also observed high diatom diversity in the open ocean, suggesting that diatoms may be more relevant in these oceanic systems than generally considered.

  14. Large variation in the Rubisco kinetics of diatoms reveals diversity among their carbon-concentrating mechanisms

    Science.gov (United States)

    Young, Jodi N.; Heureux, Ana M.C.; Sharwood, Robert E.; Rickaby, Rosalind E.M.; Morel, François M.M.; Whitney, Spencer M.

    2016-01-01

    While marine phytoplankton rival plants in their contribution to global primary productivity, our understanding of their photosynthesis remains rudimentary. In particular, the kinetic diversity of the CO2-fixing enzyme, Rubisco, in phytoplankton remains unknown. Here we quantify the maximum rates of carboxylation (k cat c), oxygenation (k cat o), Michaelis constants (K m) for CO2 (K C) and O2 (K O), and specificity for CO2 over O2 (SC/O) for Form I Rubisco from 11 diatom species. Diatom Rubisco shows greater variation in K C (23–68 µM), SC/O (57–116mol mol−1), and K O (413–2032 µM) relative to plant and algal Rubisco. The broad range of K C values mostly exceed those of C4 plant Rubisco, suggesting that the strength of the carbon-concentrating mechanism (CCM) in diatoms is more diverse, and more effective than previously predicted. The measured k cat c for each diatom Rubisco showed less variation (2.1–3.7s−1), thus averting the canonical trade-off typically observed between K C and k cat c for plant Form I Rubisco. Uniquely, a negative relationship between K C and cellular Rubisco content was found, suggesting variation among diatom species in how they allocate their limited cellular resources between Rubisco synthesis and their CCM. The activation status of Rubisco in each diatom was low, indicating a requirement for Rubisco activase. This work highlights the need to better understand the correlative natural diversity between the Rubisco kinetics and CCM of diatoms and the underpinning mechanistic differences in catalytic chemistry among the Form I Rubisco superfamily. PMID:27129950

  15. Insights into global diatom distribution and diversity in the world’s ocean

    KAUST Repository

    Malviya, Shruti

    2016-03-01

    Diatoms (Bacillariophyta) constitute one of the most diverse and ecologically important groups of phytoplankton. They are considered to be particularly important in nutrient-rich coastal ecosystems and at high latitudes, but considerably less so in the oligotrophic open ocean. The Tara Oceans circumnavigation collected samples from a wide range of oceanic regions using a standardized sampling procedure. Here, a total of ∼12 million diatom V9-18S ribosomal DNA (rDNA) ribotypes, derived from 293 sizefractionated plankton communities collected at 46 sampling sites across the global ocean euphotic zone, have been analyzed to explore diatom global diversity and community composition. We provide a new estimate of diversity of marine planktonic diatoms at 4,748 operational taxonomic units (OTUs). Based on the total assigned ribotypes, Chaetoceros was the most abundant and diverse genus, followed by Fragilariopsis, Thalassiosira, and Corethron. We found only a few cosmopolitan ribotypes displaying an even distribution across stations and high abundance, many of which could not be assigned with confidence to any known genus. Three distinct communities from South Pacific, Mediterranean, and Southern Ocean waters were identified that share a substantial percentage of ribotypes within them. Sudden drops in diversity were observed at Cape Agulhas, which separates the Indian and Atlantic Oceans, and across the Drake Passage between the Atlantic and Southern Oceans, indicating the importance of these ocean circulation choke points in constraining diatom distribution and diversity. We also observed high diatom diversity in the open ocean, suggesting that diatoms may be more relevant in these oceanic systems than generally considered.

  16. Steam based conversion coating on AA6060 alloy: Effect of sodium silicate chemistry and corrosion performance

    Science.gov (United States)

    Din, Rameez Ud; Bordo, Kirill; Tabrizian, Naja; Jellesen, Morten Stendahl; Ambat, Rajan

    2017-11-01

    Surface treatment of aluminium alloy AA6060 using an industrially applicable pilot steam jet system with and without silicate chemistry has been investigated. Treatment using steam alone and steam with silicate, resulted in an oxide layer formation with thickness ∼425 nm and ∼160 nm, respectively. Moreover, the use of sodium silicate resulted in the formation of distinct microstructure and incorporation of silicate into the oxide film. These oxide films reduced the anodic activity 4 times, while the corrosion protection by silicate containing oxide was the function of its concentration. Further, in acid salt spray and filiform corrosion tests, oxide layer containing silicate exhibited two times higher corrosion resistance.

  17. Rubber curing chemistry governing the orientation of layered silicate

    Directory of Open Access Journals (Sweden)

    2007-11-01

    Full Text Available The effect of curing systems on the orientation and the dispersion of the layered silicates in acrylonitrile butadiene rubber nanocomposite is reported. Significant differences in X-ray diffraction pattern between peroxide curing and sulfur curing was observed. Intense X-ray scattering values in the XRD experiments from peroxide cured vulcanizates indicate an orientation of the layers in a preferred direction as evinced by transmission electron micrographs. However, sulfur cured vulcanizates show no preferential orientation of the silicate particles. Nevertheless, a closer inspection of transmission electron microscopy (TEM images of peroxide and sulfur cured samples shows exfoliated silicate layers in the acrylonitrile butadiene rubber (NBR matrix. It was revealed in the prevailing study that the use of an excess amount of stearic acid in the formulation of the sulfur curing package leads to almost exfoliated type X-ray scattering pattern.

  18. Crystallochemical characteristics of alkali calcium silicates from charoitites

    International Nuclear Information System (INIS)

    Rozhdestvenskaya, I.V.; Nikishova, L.V.

    2002-01-01

    The characteristic features of the crystal structures of alkali calcium silicates from various deposits are considered. The structures of these minerals, which were established by single-crystal X-ray diffraction methods, are described as the combinations of large construction modules, including the alternating layers of alkali cations and tubular silicate radicals (in canasite, frankamenite, miserite, and agrellite) and bent ribbons linked through hydrogen bonds in the layers (in tinaksite and tokkoite). The incorporation of impurities and the different ways of ordering them have different effects on the structures of these minerals and give rise to the formation of superstructures accompanied by a change of the space group (frankamenite-canasite), leading, in turn, to different mutual arrangements of the layers of silicate tubes and the formation of pseudopolytypes (agrellites), structure deformation, and changes in the unit-cell parameters (tinaksite-tokkoite)

  19. Petrophysical Analysis of Siliceous Ooze Sediments, Ormen Lange Field, Norway

    DEFF Research Database (Denmark)

    Awedalkarim, Ahmed; Fabricius, Ida Lykke

    , but apparent porosity indications in any other lithology, such as siliceous ooze, are wrong and they should be corrected. The apparent bulk density log should be influenced by the hydrogen in opal as also the neutron porosity tools because they are sensitive to the amount of hydrogen in a formation...... present in the solid. Some minerals of siliceous ooze, such as opal, have hydrogen in their structures which influences the measured hydrogen index (HI). The neutron tool obtains the combined signal of the HI of the solid phase and of the water that occupies the true porosity. The HI is equal to true...... to interpret lithology and the unusual physical properties of the studied intervals. The integration of all these data revealed that the studied siliceous ooze is a mixture of opal and non-opal (shale). Our results proved to be reasonably consistent. The studied intervals apparently do not contain hydrocarbons....

  20. Energetic Processing of Interstellar Silicate Grains by Cosmic Rays

    Energy Technology Data Exchange (ETDEWEB)

    Bringa, E M; Kucheyev, S O; Loeffler, M J; Baragiola, R A; Tielens, A G Q M; Dai, Z R; Graham, G; Bajt, S; Bradley, J; Dukes, C A; Felter, T E; Torres, D F; van Breugel, W

    2007-03-28

    While a significant fraction of silicate dust in stellar winds has a crystalline structure, in the interstellar medium nearly all of it is amorphous. One possible explanation for this observation is the amorphization of crystalline silicates by relatively 'low' energy, heavy ion cosmic rays. Here we present the results of multiple laboratory experiments showing that single-crystal synthetic forsterite (Mg{sub 2}SiO{sub 4}) amorphizes when irradiated by 10 MeV Xe{sup ++} ions at large enough fluences. Using modeling, we extrapolate these results to show that 0.1-5.0 GeV heavy ion cosmic rays can rapidly ({approx}70 Million yrs) amorphize crystalline silicate grains ejected by stars into the interstellar medium.

  1. Synthesis and luminescence properties of erbium silicate thin films

    International Nuclear Information System (INIS)

    Miritello, Maria; Lo Savio, Roberto; Iacona, Fabio; Franzo, Giorgia; Bongiorno, Corrado; Priolo, Francesco

    2008-01-01

    We have studied the structure and the room temperature luminescence of erbium silicate thin films deposited by rf magnetron sputtering. Films deposited on silicon oxide layers are characterized by good structural properties and excellent stability. The optical properties of these films are strongly improved by rapid thermal annealing processes performed in the range of temperature 800-1250 deg. C. In fact through the reduction of the defect density of the material, a very efficient room temperature photoluminescence at 1535 nm is obtained. We have also investigated the influence of the annealing ambient, by finding that treatments in O 2 atmosphere are significantly more efficient in improving the optical properties of the material with respect to processes in N 2 . Upconversion effects become effective only when erbium silicate is excited with high pump powers. The evidence that all Er atoms (about 10 22 cm -3 ) in erbium silicate films are optically active suggests interesting perspectives for optoelectronic applications of this material

  2. FACIES, MICROFOSSILS (SMALLER FORAMINIFERS, CALCAREOUS ALGAE AND BIOSTRATIGRAPHY OF THE HUECO GROUP, DOÑA ANA MOUNTAINS, SOUTHERN NEW MEXICO, USA

    Directory of Open Access Journals (Sweden)

    KARL KRAINER

    2009-03-01

    Full Text Available The Lower Permian Hueco Group of the Doña Ana Mountains (south-central New Mexico, USA is studied in three sections (A, B, C located east of Leasburg, Doña Ana County. Regionally, the Hueco Group has been subdivided into four formations termed Shalem Colony, Community Pit, Robledo Mountains and Apache Dam formations; the lower three are exposed in the Doña Ana Mountains. The succession shows a shallowing upward trend from dominantly shallow, open marine conditions (Shalem Colony Fm to increasingly restricted marine environments (Community Pit Fm and siliciclastic influx (Robledo Mountains Formation. Sedimentation, particularly siliciclastic influx, was mainly controlled by reactivation of basement uplifts during the last pulses of the Ancestral Rocky Mountains deformation. The microfossils and microfacies of the two first formations are studied in detail here. The Shalem Colony Formation can be divided into a lower biozone with Triticites pinguis, which is Newwellian (latest Pennsylvanian, early Wolfcampian in age, and an upper division characterized by the first occurrence of Geinitzina, and lower-middle Asselian (late early Wolfcampian in age. By comparison with the subdivisions of the Carnic Alps (Austria, the Community Pit Formation is characterized as Sakmarian (middle Wolfcampian in age due to the first occurrence of the genus Pseudovermiporella, and its probable complete phylogeny from Hedraites. The late Asselian is restricted to the uppermost part of the Shalem Colony and lowermost part of the Community Pit Formation. Due to the occurrence of Pseudoreichelina the Robledo Mountains Formation is dated as Artinskian (late Wolfcampian. Some bioconstructions of Archaeolithophyllum are emphasized, as well as some species of foraminifers-globivalvulinids, Miliolata and Nodosariata. 

  3. Paleo-hydrological changes in the Chew Bahir area during the past 50 ka inferred from isotope signatures in aquatic microfossils

    Science.gov (United States)

    Junginger, Annett

    2017-04-01

    A major challenge in paleo-anthropology is to understand the impact of climatic changes on human evolution. The Hominin Sites and Paleo-lakes Drilling Project (HSPDP) is currently meeting that challenge by providing records that cover the last 3.7 Ma of paleoenvironmental change all located in close proximity to key paleo-anthropological findings in East Africa. One of the cored climatic archives comes from the Chew Bahir basin in southern Ethiopia, where duplicate sediment cores provide valuable insights about East African environmental variability during the last 550 ka. The lake basins in the eastern branch of the East African Rift System today contain mainly shallow and alkaline lakes. However, paleo-shorelines in the form of wave cut notches, shell beds, and beach ridges are common morphological evidences for deep freshwater lakes that have filled the basins up to their overflow level during pronounced humid episodes, such as the African Humid Period (15-5 ka). Unfortunately, further back in time, many of those morphological features disappear due to erosion and the estimation of paleo-water depths depend merely on qualitative proxies from core analyses. We here present a method that shows high potential to translate qualitative proxy signals from sediment core analyses to quantitative climate signals in the Ethiopian Rift. The method aims at water level reconstruction in the Chew Bahir basin using strontium isotope ratios (87Sr/86Sr, SIR) in lacustrine microfossils. SIR reflect the lithology of the drained catchment. SIR have changed pronouncedly when higher elevated paleo-lakes Abaya, Chamo and Awassa were overflowing into paleo-lake Chew Bahir. This new method may help to quantify paleo-lake levels beyond the past 20 ka and may also detect migrational barriers or routes due to the occurrence of synchronous large, connected and deep paleo-lakes.

  4. Potassium Silicate Foliar Fertilizer Grade from Geothermal Sludge and Pyrophyllite

    Directory of Open Access Journals (Sweden)

    Muljani Srie

    2016-01-01

    Full Text Available Potassium silicate fertilizer grade were successfully produced by direct fusion of silica (SiO2 and potasium (KOH and K2CO3 in furnaces at temperatures up to melting point of mixture. The geothermal sludge (98% SiO2 and the pyrophyllite (95% SiO2 were used as silica sources. The purposes of the study was to synthesise potassium silicate fertilizer grade having solids concentrations in the range of 31-37% K2O, and silica in the range of 48-54% SiO2. The weight ratio of silicon dioxide/potasium solid being 1:1 to 5:1. Silica from geothermal sludge is amorphous, whereas pyrophylite is crystalline phase. The results showed that the amount of raw materials needed to get the appropriate molar ratio of potassium silicate fertilizer grade are different, as well as the fusion temperature of the furnace. Potassium silicate prepared from potassium hydroxide and geothermal sludge produced a low molar ratio (2.5: 1 to 3: 1. The potassium required quite small (4:1 in weight ratio, and on a fusion temperature of about 900 °C. Meanwhile, the potassium silicate prepared from pyrophyllite produced a high molar ratio (1.4 - 9.4 and on a fusion temperature of about 1350 °C, so that potassium needed large enough to meet the required molar ratio for the fertilizer grade. The product potassium silicate solid is amorphous with a little trace of crystalline.

  5. Leaf application of silicic acid to upland rice and corn

    Directory of Open Access Journals (Sweden)

    Carlos Alexandre Costa Crusciol

    2013-12-01

    Full Text Available This study aimed to evaluate the effect of Si (stabilized silicic acid, Silamol® leaf application on mineral nutrition and yield in upland rice and corn crops. The treatments were the control (without Si and Si foliar split spraying using 2 L ha-1 of the Silamol® commercial product, with 0.8% soluble Si as concentrated stabilized silicic acid. Silicon leaf application increased the concentrations of K, Ca and Si in rice and corn leaves, the number of panicles per m2 of rice and the number of grains per ear of corn; accordingly, the Si leaf application provided a higher grain yield in both crops.

  6. Dinoflagellate blooms in upwelling systems: Seeding, variability, and contrasts with diatom bloom behaviour

    Science.gov (United States)

    Smayda, T. J.; Trainer, V. L.

    2010-04-01

    The influence of diatom bloom behaviour, dinoflagellate life cycles, propagule type and upwelling bloom cycles on the seeding of dinoflagellate blooms in eastern boundary current upwelling systems is evaluated. Winter-spring diatom bloom behaviour is contrasted with upwelling bloom behaviour because their phenology impacts dinoflagellate blooms. The winter-spring diatom bloom is usually sustained, whereas the classical upwelling diatom bloom occurs as a series of separate, recurrent mini-blooms intercalated by upwelling-relaxation periods, during which dinoflagellates often bloom. Four sequential wind-regulated phases characterize upwelling cycles, with each phase having different effects on diatom and dinoflagellate bloom behaviour: bloom “spin up”, bloom maximum, bloom “spin down”, and upwelling relaxation. The spin up - bloom maximum is the period of heightened diatom growth; the spin down - upwelling-relaxation phases are the periods when dinoflagellates often bloom. The duration, intensity and ratio of the upwelling and relaxation periods making up upwelling cycles determine the potential for dinoflagellate blooms to develop within a given upwelling cycle and prior to the subsequent “spin up” of upwelling that favours diatom blooms. Upwelling diatoms and meroplanktonic dinoflagellates have three types of propagules available to seed blooms: vegetative cells, resting cells and resting cysts. However, most upwelling dinoflagellates are holoplanktonic, which indicates that the capacity to form resting cysts is not an absolute requirement for growth and survival in upwelling systems. The long-term (decadal) gaps in bloom behaviour of Gymnodinium catenatum and Lingulodinium polyedrum, and the unpredictable bloom behaviour of dinoflagellates generally, are examined from the perspective of seeding strategies. Mismatches between observed and expected in situ bloom behaviour and resting cyst dynamics are common among upwelling dinoflagellates. This

  7. Experimental toxicity and bioaccumulation of cadmium in freshwater periphytic diatoms in relation with biofilm maturity

    International Nuclear Information System (INIS)

    Duong, Thi Thuy; Morin, Soizic; Coste, Michel; Herlory, Olivier; Feurtet-Mazel, Agnes; Boudou, Alain

    2010-01-01

    A study was undertaken to examine cadmium accumulation in freshwater biofilm, its effects on biofilm development and on diatom community structure in laboratory experimental conditions. A suspension of a biofilm originated from the Riou-Mort River (South West France) was inoculated into three experimental units containing clean glass substrates under laboratory conditions. Settling and already developed biofilms were exposed to a Cd concentration of 100 μg L -1 . Metal accumulation (total and intracellular metal content) in biofilms, dry weight and ash-free dry mass, diatom cell density and diatom community composition were analyzed. Both total and intracellular Cd accumulated by the biofilm throughout the experiment increased with duration of metal exposure. Biofilms in the course of maturation were showed higher Cd content and less effective development than settled biofilms. However diatom communities in younger biofilms exposed to Cd increased their tolerance to Cd by a highly significant development of Nitzschia palea. In contrast, Cd exposure had different effect in installed biofilm and taxonomic composition. These results indicate that mature biofilm may limit Cd accumulation into its architecture and protect diatom communities from the effects of metals.

  8. Taxonomic studies of centric diatoms (Diatomeae: unusual nanoplanktonic forms and new records for Brazil

    Directory of Open Access Journals (Sweden)

    Kaoli Pereira Cavalcante

    2013-06-01

    Full Text Available There have been few taxonomic studies of centric diatoms in lotic freshwater environments in Brazil, especially in terms of those including nanoplanktonic forms, which are often neglected in studies of local floras, because of their small size or confusing taxonomy. This is the first study focusing on centric diatoms in the flora of the state of Bahia, in northeastern Brazil. Plankton and periphyton attached to Eichornia crassipes were collected in the winter of 2009 in the Cachoeira River. The diatoms were analyzed and described under light and electron microscopies. Seventeen infrageneric taxa were identified. Cyclotella was represented by five taxa, and concerning of similarities between diacritical features of species in this genus, their descriptions were thoroughly detailed. This was the first time that Cyclotella atomus var. marina, previously recorded only in coastal areas of Japan and Korea, has been documented in a river in South America. We also identified two diatom taxa previously unrecorded in the flora of Brazil: C. cryptica and C. meduanae. Finally, we present a detailed light, transmission and scanning electron microscopy analysis of Skeletonema potamos, a diatom rarely found in the Brazilian literature.

  9. A stress surveillance system based on calcium and nitric oxide in marine diatoms.

    Directory of Open Access Journals (Sweden)

    Assaf Vardi

    2006-03-01

    Full Text Available Diatoms are an important group of eukaryotic phytoplankton, responsible for about 20% of global primary productivity. Study of the functional role of chemical signaling within phytoplankton assemblages is still in its infancy although recent reports in diatoms suggest the existence of chemical-based defense strategies. Here, we demonstrate how the accurate perception of diatom-derived reactive aldehydes can determine cell fate in diatoms. In particular, the aldehyde (2E,4E/Z-decadienal (DD can trigger intracellular calcium transients and the generation of nitric oxide (NO by a calcium-dependent NO synthase-like activity, which results in cell death. However, pretreatment of cells with sublethal doses of aldehyde can induce resistance to subsequent lethal doses, which is reflected in an altered calcium signature and kinetics of NO production. We also present evidence for a DD-derived NO-based intercellular signaling system for the perception of stressed bystander cells. Based on these findings, we propose the existence of a sophisticated stress surveillance system in diatoms, which has important implications for understanding the cellular mechanisms responsible for acclimation versus death during phytoplankton bloom successions.

  10. Signal, Uncertainty, and Conflict in Phylogenomic Data for a Diverse Lineage of Microbial Eukaryotes (Diatoms, Bacillariophyta)

    Science.gov (United States)

    Parks, Matthew B; Wickett, Norman J; Alverson, Andrew J

    2018-01-01

    Abstract Diatoms (Bacillariophyta) are a species-rich group of eukaryotic microbes diverse in morphology, ecology, and metabolism. Previous reconstructions of the diatom phylogeny based on one or a few genes have resulted in inconsistent resolution or low support for critical nodes. We applied phylogenetic paralog pruning techniques to a data set of 94 diatom genomes and transcriptomes to infer perennially difficult species relationships, using concatenation and summary-coalescent methods to reconstruct species trees from data sets spanning a wide range of thresholds for taxon and column occupancy in gene alignments. Conflicts between gene and species trees decreased with both increasing taxon occupancy and bootstrap cutoffs applied to gene trees. Concordance between gene and species trees was lowest for short internodes and increased logarithmically with increasing edge length, suggesting that incomplete lineage sorting disproportionately affects species tree inference at short internodes, which are a common feature of the diatom phylogeny. Although species tree topologies were largely consistent across many data treatments, concatenation methods appeared to outperform summary-coalescent methods for sparse alignments. Our results underscore that approaches to species-tree inference based on few loci are likely to be misled by unrepresentative sampling of gene histories, particularly in lineages that may have diversified rapidly. In addition, phylogenomic studies of diatoms, and potentially other hyperdiverse groups, should maximize the number of gene trees with high taxon occupancy, though there is clearly a limit to how many of these genes will be available. PMID:29040712

  11. The transcriptome and proteome of the diatom Thalassiosira pseudonana reveal a diverse phosphorus stress response.

    Directory of Open Access Journals (Sweden)

    Sonya T Dyhrman

    Full Text Available Phosphorus (P is a critical driver of phytoplankton growth and ecosystem function in the ocean. Diatoms are an abundant class of marine phytoplankton that are responsible for significant amounts of primary production. With the control they exert on the oceanic carbon cycle, there have been a number of studies focused on how diatoms respond to limiting macro and micronutrients such as iron and nitrogen. However, diatom physiological responses to P deficiency are poorly understood. Here, we couple deep sequencing of transcript tags and quantitative proteomics to analyze the diatom Thalassiosira pseudonana grown under P-replete and P-deficient conditions. A total of 318 transcripts were differentially regulated with a false discovery rate of <0.05, and a total of 136 proteins were differentially abundant (p<0.05. Significant changes in the abundance of transcripts and proteins were observed and coordinated for multiple biochemical pathways, including glycolysis and translation. Patterns in transcript and protein abundance were also linked to physiological changes in cellular P distributions, and enzyme activities. These data demonstrate that diatom P deficiency results in changes in cellular P allocation through polyphosphate production, increased P transport, a switch to utilization of dissolved organic P through increased production of metalloenzymes, and a remodeling of the cell surface through production of sulfolipids. Together, these findings reveal that T. pseudonana has evolved a sophisticated response to P deficiency involving multiple biochemical strategies that are likely critical to its ability to respond to variations in environmental P availability.

  12. Aldehyde suppression of copepod recruitment in blooms of a ubiquitous planktonic diatom

    Science.gov (United States)

    Ianora, Adrianna; Miralto, Antonio; Poulet, Serge A.; Carotenuto, Ylenia; Buttino, Isabella; Romano, Giovanna; Casotti, Raffaella; Pohnert, Georg; Wichard, Thomas; Colucci-D'Amato, Luca; Terrazzano, Giuseppe; Smetacek, Victor

    2004-05-01

    The growth cycle in nutrient-rich, aquatic environments starts with a diatom bloom that ends in mass sinking of ungrazed cells and phytodetritus. The low grazing pressure on these blooms has been attributed to the inability of overwintering copepod populations to track them temporally. We tested an alternative explanation: that dominant diatom species impair the reproductive success of their grazers. We compared larval development of a common overwintering copepod fed on a ubiquitous, early-blooming diatom species with its development when fed on a typical post-bloom dinoflagellate. Development was arrested in all larvae in which both mothers and their larvae were fed the diatom diet. Mortality remained high even if larvae were switched to the dinoflagellate diet. Aldehydes, cleaved from a fatty acid precursor by enzymes activated within seconds after crushing of the cell, elicit the teratogenic effect. This insidious mechanism, which does not deter the herbivore from feeding but impairs its recruitment, will restrain the cohort size of the next generation of early-rising overwinterers. Such a transgenerational plant-herbivore interaction could explain the recurringly inefficient use of a predictable, potentially valuable food resource-the spring diatom bloom-by marine zooplankton.

  13. Cadmium sensitivity, uptake, subcellular distribution and thiol induction in a marine diatom: Exposure to cadmium

    International Nuclear Information System (INIS)

    Wang Mengjiao; Wang Wenxiong

    2011-01-01

    The aims of this study were to (1) evaluate the changes in the Cd tolerance of a marine diatom after exposure under different Cd concentrations for various durations and (2) to explore the potential subcellular and biochemical mechanisms underlying these changes. The 72-h toxicity, short-term Cd uptake, subcellular Cd distribution, as well as the synthesis of phytochelatins (PCs) were measured in a marine diatom Thalassiosira nordenskioeldii after exposure to a range of free Cd ion concentrations ([Cd 2+ ], 0.01-84 nM) for 1-15 days. Surprisingly, the diatoms did not acquire higher resistance to Cd after exposure; instead their sensitivity to Cd increased with a higher exposed [Cd 2+ ] and a longer exposure period. The underlying mechanisms could be traced to the responses of Cd cellular accumulation and the intrinsic detoxification ability of the preconditioned diatoms. Generally, exposure to a higher [Cd 2+ ] and for a longer period increased the Cd uptake rate, cellular accumulation, as well as the Cd concentration in metal-sensitive fraction (MSF) in these diatoms. In contrast, although PCs were induced by the environmental Cd stress (with PC 2 being the most affected), the increased intracellular Cd to PC-SH ratio implied that the PCs' detoxification ability had reduced after Cd exposure. All these responses resulted in an elevated Cd sensitivity as exposed [Cd 2+ ] and duration increased. This study shows that the physiological/biochemical and kinetic responses of phytoplankton upon metal exposure deserve further investigation.

  14. Low-Molecular-Weight Metabolites from Diatoms: Structures, Biological Roles and Biosynthesis

    Directory of Open Access Journals (Sweden)

    Valentin Stonik

    2015-06-01

    Full Text Available Diatoms are abundant and important biological components of the marine environment that biosynthesize diverse natural products. These microalgae are rich in various lipids, carotenoids, sterols and isoprenoids, some of them containing toxins and other metabolites. Several groups of diatom natural products have attracted great interest due to their potential practical application as energy sources (biofuel, valuable food constituents, and prospective materials for nanotechnology. In addition, hydrocarbons, which are used in climate reconstruction, polyamines which participate in biomineralization, new apoptotic agents against tumor cells, attractants and deterrents that regulate the biochemical communications between marine species in seawaters have also been isolated from diatoms. However, chemical studies on these microalgae are complicated by difficulties, connected with obtaining their biomass, and the influence of nutrients and contaminators in their environment as well as by seasonal and climatic factors on the biosynthesis of the corresponding natural products. Overall, the number of chemically studied diatoms is lower than that of other algae, but further studies, particularly those connected with improvements in the isolation and structure elucidation technique as well as the genomics of diatoms, promise both to increase the number of studied species with isolated biologically active natural products and to provide a clearer perception of their biosynthesis.

  15. Diatomic-molecule vibrational potentials. II. New representationsa)

    International Nuclear Information System (INIS)

    Engelke, R.

    1979-01-01

    Two new representations of diatomic-molecule vibrational potentials are presented. One of these includes most of the previously employed series approximations as special cases. The new representations are tested against older ones by using Peek's ''exact'' numerical Born--Oppenheimer potentials for the 1ssigma/sub g/, 2pπ/sub u/, and 3dsigma/sub g/ states of H 2 + as test problems. Accuracy comparisons are made with Dunham, Thakkar, Ogilvie--Tipping, Coulomb-subtracted Ogilvie--Tipping, and Pade representations. A central idea of the new treatment is that it is not necessary to use a global representation of the potential over the region 0 or =1 and then match them smoothly to each other and to the Dunham expansion at R/R/sub e/=1. Attention is focused on finding improved approximations for R/R/sub e/>1, since this region exerts strong control on the vibrational eigenvalue spectrum and it is here, perhaps, where the older techniques are at their weakest. Known properties of the exact potential such as the R→infinity behavior and the dissociation energy can be built into the new forms a priori. If the dissociation energy is not known, the new methods allow it to be estimated with better accuracy then could be done previously. If one knows only Dunham coefficients, the Coulomb-subtracted Ogilvie--Tipping series is the superior representation. If one knows, in addition, the dissociation energy, the new representations are superior and give more accurate results on the interval R/R/sub e/> or =1

  16. Obtainment and characterization of pure and doped gadolinium oxy ortho silicates with terbium III, precursor of luminescent silicates with sulphur

    International Nuclear Information System (INIS)

    Simoneti, J.A.

    1992-01-01

    Silicate and sulfide lattices are uniquely efficient luminescent materials to excitation by cathodic rays and furthermore the cathodoluminescence study of these compounds have been few investigated. In this work it has been prepared, characterized and investigated some spectroscopic properties of pure and Tb a+ - activated Gd 2 Si O 3 system and it has been tried to substitute oxygen by sulphur in order to obtain this or sulfide-silicate lattices. Products were characterized by vibrational infrared spectroscopy, powder X-ray diffraction patterns and electronic emission in UV-VIS region. (author)

  17. Penicillin-mediated changes in viable benthic diatom assemblages – insights about the relevance of bacteria across spatial and seasonal scales.

    Digital Repository Service at National Institute of Oceanography (India)

    DeCosta, P.M.; Anil, A.C.

    environment) and seasonal (post-monsoon, pre-monsoon, monsoon) scales. Penicillin treatment resulted in bacterial suppression and a reduction in diatoms at the intertidal and mangrove sites having stable pennate-dominated assemblages. Diatom response...

  18. Non-conservative controls on distribution of dissolved silicate in Cochin Backwaters

    Digital Repository Service at National Institute of Oceanography (India)

    Balachandran, K.K.; Sankaranarayanan, V.N.; Joseph, T.; Nair, M.

    Cochin backwater system was studied with regard to dissolved silicate (DSi) to understand its seasonal distribution and behaviour during estuarine mixing. Silicate had a linear relationship with salinity during the high river discharge period...

  19. Wind-Eroded Silicate as a Source of Hydrogen Peroxide on Mars

    Science.gov (United States)

    Bak, E. N.; Merrison, J. P.; Jensen, S. K.; Nørnberg, P.; Finster, K.

    2014-07-01

    Laboratory simulations show that wind-eroded silicate can be a source of hydrogen peroxide. The ubiquitous, fine-grained silicate dust might thus explain the oxidizing properties of the martian soil and affect the preservation of organic compounds.

  20. SILICATE TECHNOLOGY CORPORATION'S SOLIDIFICATION/ STABILIZATION TECHNOLOGY FOR ORGANIC AND INORGANIC CONTAMINANTS IN SOILS - APPLICATIONS ANALYSIS REPORT

    Science.gov (United States)

    This Applications Analysis Report evaluates the solidification/stabilization treatment process of Silicate Technology Corporation (STC) for the on-site treatment of hazardous waste. The STC immobilization technology utilizes a proprietary product (FMS Silicate) to chemically stab...

  1. E-Beam-Cured Layered-Silicate and Spherical Silica Epoxy Nanocomposites (Preprint)

    National Research Council Canada - National Science Library

    Chen, Chenggang; Anderson, David P

    2007-01-01

    .... The nanofillers can be two dimensional (layered-silicate) and zero dimensional (spherical silica). Both the spherical silica epoxy nanocomposite and the layered-silicate epoxy nanocomposite can be cured to a high degree of curing...

  2. Effect of Low ph on Carbohydrate Production by a Marine Planktonic Diatom (Chaetoceros muelleri)

    International Nuclear Information System (INIS)

    Thornton, D.C.O.

    2009-01-01

    Rising carbon dioxide (CO 2 ) concentrations in the atmosphere due to human activity are causing the surface ocean to become more acidic. Diatoms play a pivotal role in biogeochemical cycling and ecosystem function in the ocean. ph affected the quantum efficiency of photosystem II and carbohydrate metabolism in a planktonic diatom (Chaetoceros muelleri), representative of a widely distributed genus. In batch cultures grown at low ph, the proportion of total carbohydrate stored within the cells decreased and more dissolved carbohydrates were exuded from the cells into the surrounding medium. Changes in productivity and the way in which diatoms allocate carbon into carbohydrates may affect ecosystem function and the efficiency of the biological carbon pump in a low ph ocean.

  3. Effects of silicon deficiency on lipid and carbohydrate metabolism in the diatom Cyclotella cryptica

    International Nuclear Information System (INIS)

    Roessler, P.G.

    1987-01-01

    Previous studies have shown that silicon deficiency induces lipid accumulation in certain diatom species. The nature of the lipids produced under these conditions was not investigated, however, and the biochemical mechanisms which underlie this phenomenon were not determined. Research was carried out in order to increase our knowledge concerning the aspects of lipid accumulation in diatoms. The first phase of this project indicated that the diatoms C. cryptica, Cylindrotheca fusiformis, and Thalassiosira pseudonana accumulated storage lipids when grown under silicon-limiting conditions. The ratio of saturated and monounsaturated fatty acids to polyunsaturated fatty acids in C. cryptica cells increased markedly after 24 hours of silicon deficiency. Tracer experiments with [ 14 C]bicarbonate suggested that lipid accumulation in silicon-limited C. cryptica cells was due to two distinct processes: (1) an increase in the amount of newly photoassimilated carbon partitioned into lipids, and (2) a slow conversion of non-lipid compounds (carbohydrates and presumably proteins) into lipids

  4. Biosilica from Living Diatoms: Investigations on Biocompatibility of Bare and Chemically Modified Thalassiosira weissflogii Silica Shells

    Directory of Open Access Journals (Sweden)

    Stefania Roberta Cicco

    2016-12-01

    Full Text Available In the past decade, mesoporous silica nanoparticles (MSNs with a large surface area and pore volume have attracted considerable attention for their application in drug delivery and biomedicine. Here we propose biosilica from diatoms as an alternative source of mesoporous materials in the field of multifunctional supports for cell growth: the biosilica surfaces were chemically modified by traditional silanization methods resulting in diatom silica microparticles functionalized with 3-mercaptopropyl-trimethoxysilane (MPTMS and 3-aminopropyl-triethoxysilane (APTES. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses revealed that the –SH or –NH2 were successfully grafted onto the biosilica surface. The relationship among the type of functional groups and the cell viability was established as well as the interaction of the cells with the nanoporosity of frustules. These results show that diatom microparticles are promising natural biomaterials suitable for cell growth, and that the surfaces, owing to the mercapto groups, exhibit good biocompatibility.

  5. Late Pliocene diatoms in a diatomite from Prydz Bay, East Antarctica

    Science.gov (United States)

    Mahood, A.D.; Barron, J.A.

    1996-01-01

    Very well-preserved Pliocene diatoms from a diatomite unit interbedded within glacial sediments at Ocean Drilling Program Site 742 in Prydz Bay, Antarctica are documented and illustrated. The presence of Thalassiosira kolbei, T. torokina, Actinocyclus actinochilus, A. karstenii and the absence of Nitzschia interfrigidaria. T. insigna and T. vulnifica in Sample 119-742A-15R-4, 44-46cm constrain its age to ca. 2.2-1.8 Ma (late Pliocene). Diatoms associated with sea ice constitute 35% of the Pliocene diatom assemblage, compared with 71% of the modern sediment assemblage at the site, suggesting that sea ice was present during the late Pliocene period of deposition of the sample, although it probably was not the significant feature it is today. Thalassiosira ellitipora (Donahue) Fenner is described and illustrated in detail and is validly published. An expanded description and numerous illustrations are also presented for T. torokina Brady.

  6. Probing the evolutionary history of epigenetic mechanisms: what can we learn from marine diatoms

    Directory of Open Access Journals (Sweden)

    Achal Rastogi

    2015-07-01

    Full Text Available Recent progress made on epigenetic studies revealed the conservation of epigenetic features in deep diverse branching species including Stramenopiles, plants and animals. This suggests their fundamental role in shaping species genomes across different evolutionary time scales. Diatoms are a highly successful and diverse group of phytoplankton with a fossil record of about 190 million years ago. They are distantly related from other super-groups of Eukaryotes and have retained some of the epigenetic features found in mammals and plants suggesting their ancient origin. Phaeodactylum tricornutum and Thalassiosira pseudonana, pennate and centric diatoms, respectively, emerged as model species to address questions on the evolution of epigenetic phenomena such as what has been lost, retained or has evolved in contemporary species. In the present work, we will discuss how the study of non-model or emerging model organisms, such as diatoms, helps understand the evolutionary history of epigenetic mechanisms with a particular focus on DNA methylation and histone modifications.

  7. Dielectric properties of plasma sprayed silicates subjected to additional annealing

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Sedláček, J.; Nevrlá, Barbara; Neufuss, Karel

    2017-01-01

    Roč. 10, č. 2 (2017), s. 105-114 ISSN 2008-2134 Institutional support: RVO:61389021 Keywords : Annealing * Dielectric properties * Plasma spraying * Silicates * Electrical properties * Insulators Subject RIV: JK - Corrosion ; Surface Treatment of Materials OBOR OECD: Coating and films http://pccc.icrc.ac.ir/Articles/1/18/990/

  8. Vesuvianite–wollastonite–grossular-bearing calc-silicate rock near ...

    Indian Academy of Sciences (India)

    Felsic layers are white in colour, whereas mafic layers range from green, brown to grey colour depending on the modal abundance of different mafic minerals. Layers rich in diopside are green coloured and those rich in garnet are brown. Keywords. Vesuvianite; wollastonite; grossular; diopside; calc-silicate rock. J. Earth ...

  9. Decreased water flowing from a forest amended with calcium silicate

    Science.gov (United States)

    Mark B. Green; Amey S. Bailey; Scott W. Bailey; John J. Battles; John L. Campbell; Charles T. Driscoll; Timothy J. Fahey; Lucie C. Lepine; Gene E. Likens; Scott V. Ollinger; Paul G. Schaberg

    2013-01-01

    Acid deposition during the 20th century caused widespread depletion of available soil calcium (Ca) throughout much of the industrialized world. To better understand how forest ecosystems respond to changes in a component of acidification stress, an 11.8-ha watershed was amended with wollastonite, a calcium silicate mineral, to restore available soil Ca to preindustrial...

  10. Preparation of β-belite using liquid alkali silicates

    International Nuclear Information System (INIS)

    Koutník, P.

    2017-01-01

    The aim of this study is the preparation of β-belite by a solid-state reaction using powdered limestone, amorphous silica and liquid alkali silicates. The raw materials were blended, the mixtures were agglomerated and then burnt. The resulting samples were characterized by X-ray diffraction analysis and scanning electron microscopy. Free lime content in the β-belite samples was also determined. The effects of CaO/SiO2 ratio (1.6–2.1), burning temperature (800–1400 °C), utilization of different raw materials (silica fume, synthetic silica, potassium silicate, sodium silicate, potassium hydroxide) and burning time (0.5–16 h) on free lime content and mineralogical composition were investigated. The purest ?-belite samples were prepared from a mixture of powdered limestone, silica fume and liquid potassium silicate with a ratio CaO/SiO2 = 2 by burning at temperatures between 1100 and 1300 °C for more than 2 h. Decreasing of the CaO/SiO2 ratio led to rankinite formation and lower a burning temperature led to the formation of wollastonite. [es

  11. Silicon K-edge XANES spectra of silicate minerals

    Science.gov (United States)

    Li, Dien; Bancroft, G. M.; Fleet, M. E.; Feng, X. H.

    1995-03-01

    Silicon K-edge x-ray absorption near-edge structure (XANES) spectra of a selection of silicate and aluminosilicate minerals have been measured using synchrotron radiation (SR). The spectra are qualitatively interpreted based on MO calculation of the tetrahedral SiO{4/4-}cluster. The Si K-edge generally shifts to higher energy with increased polymerization of silicates by about 1.3 eV, but with considerable overlap for silicates of different polymerization types. The substitution of Al for Si shifts the Si K-edge to lower energy. The chemical shift of Si K-edge is also sensitive to cations in more distant atom shells; for example, the Si K-edge shifts to lower energy with the substitution of Al for Mg in octahedral sites. The shifts of the Si K-edge show weak correlation with average Si-O bond distance (dSi-O), Si-O bond valence (sSi-O) and distortion of SiO4 tetrahedra, due to the crystal structure complexity of silicate minerals and multiple factors effecting the x-ray absorption processes.

  12. Preparation and characterization of magnesium–aluminium–silicate ...

    Indian Academy of Sciences (India)

    A three-stage heating schedule involving calcination, nucleation and crystallization, has been evolved for the preparation of magnesium aluminium silicate (MAS) glass ceramic with MgF2 as a nucleating agent. The effect of sintering temperature on the density of compacted material was studied. Microstructure and ...

  13. Effect of antioxidants and silicates on peroxides in povidone.

    Science.gov (United States)

    Narang, Ajit S; Rao, Venkatramana M; Desai, Divyakant S

    2012-01-01

    Reactive peroxides in povidone often lead to degradation of oxidation-labile drugs. To reduce peroxide concentration in povidone, the roles of storage conditions, antioxidants, and silicates were investigated. Povidone alone and its physical mixtures with ascorbic acid, propyl gallate, sodium sulfite, butylated hydroxyanisole (BHA), or butylated hydroxytoluene (BHT) were stored at 25 °C and 40 °C, at 11%, 32%, and 50% relative humidity. In addition, povidone solution in methanol was equilibrated with silicates (silica gel and molecular sieves), followed by solvent evaporation to recover povidone powder. Peroxide concentrations in povidone were measured. The concentration of peroxides in povidone increased under very-low-humidity storage conditions. Among the antioxidants, ascorbic acid, propyl gallate, and sodium sulfite reduced the peroxide concentration in povidone, whereas BHA and BHT did not. Water solubility appeared to determine the effectiveness of antioxidants. Also, some silicates significantly reduced peroxide concentration in povidone without affecting its functionality as a tablet binder. Porosity of silicates was critical to their ability to reduce the peroxide concentration in povidone. A combination of these approaches can reduce the initial peroxide concentration in povidone and minimize peroxide growth under routine storage conditions. Copyright © 2011 Wiley-Liss, Inc.

  14. Mineralogy and trace element chemistry of the Siliceous Earth of ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    We report the presence of a 3–5 cm thick loose fragmental layer in the Siliceous Earth at Matti ka. Gol in the Barmer basin of Rajasthan. Petrographic, chemical and mineralogical study reveals the presence of abundant volcanic debris such as glass shards, agglutinates, hollow spheroids, kinked biotites, feldspars showing ...

  15. Small angle X-ray scattering from hydrating tricalcium silicate

    International Nuclear Information System (INIS)

    Vollet, D.

    1983-01-01

    The small-angle X-ray scattering technique was used to study the structural evolution of hydrated tricalcium silicate at room temperature. The changes in specific area of the associated porosity and the evolution of density fluctuations in the solid hydrated phase were deduced from the scattering data. A correlation of these variations with the hydration mechanism is tried. (Author) [pt

  16. In vitro bioactivity and cytocompatibility of tricalcium silicate

    Indian Academy of Sciences (India)

    tricalcium silicate powder showed that it could induce bone- like apatite formation after ... ated by soaking them in SBF, cell adhesion and MTT assay, respectively. 2. .... tibility, which might be used as one of the bioactive coating materials and ...

  17. Effects of Mixed Alkaline Earth Oxides in Potash Silicate Glass ...

    African Journals Online (AJOL)

    The aim of this work is to investigate the effects of mixed alkaline earth oxide in potash silicate glasses with regards to their physical properties. More recently; there has been an increase in the demand for light weight glasses which retains their physical and chemical properties for both domestic and industrial applications.

  18. Determination of reactivity rates of silicate particle-size fractions

    Directory of Open Access Journals (Sweden)

    Angélica Cristina Fernandes Deus

    2014-04-01

    Full Text Available The efficiency of sources used for soil acidity correction depends on reactivity rate (RR and neutralization power (NP, indicated by effective calcium carbonate (ECC. Few studies establish relative efficiency of reactivity (RER for silicate particle-size fractions, therefore, the RER applied for lime are used. This study aimed to evaluate the reactivity of silicate materials affected by particle size throughout incubation periods in comparison to lime, and to calculate the RER for silicate particle-size fractions. Six correction sources were evaluated: three slags from distinct origins, dolomitic and calcitic lime separated into four particle-size fractions (2, 0.84, 0.30 and <0.30-mm sieves, and wollastonite, as an additional treatment. The treatments were applied to three soils with different texture classes. The dose of neutralizing material (calcium and magnesium oxides was applied at equal quantities, and the only variation was the particle-size material. After a 90-day incubation period, the RER was calculated for each particle-size fraction, as well as the RR and ECC of each source. The neutralization of soil acidity of the same particle-size fraction for different sources showed distinct solubility and a distinct reaction between silicates and lime. The RER for slag were higher than the limits established by Brazilian legislation, indicating that the method used for limes should not be used for the slags studied here.

  19. Novel understanding of calcium silicate hydrate from dilute hydration

    KAUST Repository

    Zhang, Lina; Yamauchi, Kazuo; Li, Zongjin; Zhang, Xixiang; Ma, Hongyan; Ge, Shenguang

    2017-01-01

    The perspective of calcium silicate hydrate (C-S-H) is still confronting various debates due to its intrinsic complicated structure and properties after decades of studies. In this study, hydration at dilute suspension of w/s equaling to 10

  20. Decomposition of pre calcined aluminium silicate ores of Afghanistan by hydrochloric acid

    International Nuclear Information System (INIS)

    Khomidi, A.K.; Mamatov, E.D.

    2015-01-01

    Present article is devoted to decomposition of pre calcined aluminium silicate ores of Afghanistan by hydrochloric acid. The physicochemical properties of initial aluminium silicate ores were studied by means of X-ray phase, differential thermal and silicate analysis. The chemical composition of aluminium containing ores was determined. The optimal conditions of interaction of initial and pre calcined siallites with hydrochloric acid were defined. The kinetics of acid decomposition of aluminium silicate ores was studied as well.

  1. Silicate Dispersion and Mechanical Reinforcement in Polysiloxane/Layered Silicate Nanocomposites

    KAUST Repository

    Schmidt, Daniel F.

    2010-01-12

    We report the first in-depth comparison of the mechanical properties and equilibrium solvent uptake of a range of polysiloxane nanocomposites based on treated and untreated montmorillonite and fumed silica nanofillers. We demonstrate the ability of equilibrium solvent uptake data (and, thus, overall physical and chemical cross-link density) to serve as a proxy for modulus (combining rubber elasticity and Flory-Rehner theory), hardness (via the theory of Boussinesq), and elongation at break, despite the nonideal nature of these networks. In contrast, we find that tensile and tear strength are not well-correlated with solvent uptake. Interfacial strength seems to dominate equilibrium solvent uptake and the mechanical properties it predicts. In the montmorillonite systems in particular, this results in the surprising consequence that equilibrium solvent uptake and mechanical properties are independent of dispersion state. We conclude that edge interactions play a more significant role than degree of exfoliation, a result unique in the field of polymer nanocomposites. This demonstrates that even a combination of polymer/nanofiller compatibility and thermodynamically stable nanofiller dispersion levels may not give rise to reinforcement. These findings provide an important caveat when attempting to connect structure and properties in polymer nanocomposites, and useful guidance in the design of optimized polymer/layered silicate nanocomposites in particular. © 2009 American Chemical Society.

  2. Transition metal ions in silicate melts. I. Manganese in sodium silicate melts

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, C; White, W B

    1980-01-01

    Optical absorption spectra obtained on glasses quenched from sodium silicate melts show Mn/sup 3 +/ to be the dominant species for melts heated in air and Mn/sup 2 +/ to be the dominant species for melts heated at P/sub O/sub 2// = 10/sup -17/ bar. The absorption spectrum of Mn/sup 3 +/ consists of an intense band at 20,000 cm/sup -1/ with a 15,000 cm/sup -1/ satellite possibly arising from the Jahn-Teller effect. The independence of the spectrum from melt composition and the high band intensity is offered as evidence for a distinct Mn/sup 3 +/ complex in the melt. The spectrum of Mn/sup 2 +/ is weak and many expected bands are not observed. A two-band luminescence spectrum from Mn/sup 2 +/ has been tentatively interpreted as due to Mn/sup 2 +/ in interstitial sites in the network and Mn/sup 2 +/ coordiated by non-bridging oxygens.

  3. Adatom Bond Dissociation in the Collision Between an Adsorbed Atom and Incident Diatomic Molecule: A Classical Trajectory Study

    International Nuclear Information System (INIS)

    Bayhan, U.

    2004-01-01

    The collisional dissociation of the Atom-Surface bond in the diatomic molecule (gas) / atom (ads) collision taking place on a bcc-structure surface have been studied by classical trajectory methods over the collision energy ranges and the attractive well depth of the diatomic molecule (gas) / atom (ads) interactions

  4. Relationship of fouling diatom number and chlorophyll-a value from Zuari estuary, Goa (west coast of India)

    Digital Repository Service at National Institute of Oceanography (India)

    Redekar, P.D.; Wagh, A.B.

    The diatom cell biomass is expressed in terms of diatom number and chlorophyll -a value on panel of glass slide. The Chlorophyll value in a water body is indicative of the productivity. The present study was conducted to find out the relationship...

  5. Influence of elevated temperature and pCO2 on the marine periphytic diatom Navicula distans and its associated organisms in culture

    Digital Repository Service at National Institute of Oceanography (India)

    Baragi, L.V.; Khandeparker, L.; Anil, A.C.

    are available for diatoms (Sett et al., 2014; Torstensson et al., 2013). Diatoms are the major primary producers and dominate the fouling community in the shallow water photic system. Fouling diatoms are: (a) a source of primary production for higher... (picoperiphyte and heterotrophic bacteria). Materials and methods Culture conditions Navicula distans, a pennate periphytic diatom, was isolated from a biofilm developed on a glass slide submerged in the waters of Dona Paula Bay located along the west coast...

  6. Herbicide effects on freshwater benthic diatoms: Induction of nucleus alterations and silica cell wall abnormalities

    International Nuclear Information System (INIS)

    Debenest, T.; Silvestre, J.; Coste, M.; Delmas, F.; Pinelli, E.

    2008-01-01

    Benthic diatoms are well known bio-indicators of river pollution by nutrients (nitrogen and phosphorus). Biological indexes, based on diatom sensitivity for non-toxic pollution, have been developed to assess the water quality. Nevertheless, they are not reliable tools to detect pollution by pesticides. Many authors have suggested that toxic agents, like pesticides, induce abnormalities of the diatom cell wall (frustule). High abnormal frustule abundances have been reported in natural diatom communities sampled in streams contaminated by pesticides. However, no direct link was found between the abundances of abnormal frustules in these communities and the pesticide concentrations in stream water. In the present study, a freshwater benthic diatom community, isolated from natural biofilm and cultured under controlled conditions, was treated with a known genotoxic herbicide, maleic hydrazide (MH). Cells were exposed to three concentrations of MH (5 x 10 -6 , 10 -6 , 10 -7 M) for 6 h followed by a 24 h-recovery time. After MH treatments, nucleus alterations were observed: abnormal nucleus location, micronucleus, multinuclear cell or disruption of the nuclear membrane. A dose-dependent increase of nuclear alterations was observed. The difference between the control (9.65 nuclear alterations per 1000 cells observed (9.65 per mille ), S.D. = 4.23) and the highest concentrations (29.40 per mille , S.D. = 8.49 for 10 -6 M and 35.96 per mille , S.D. = 3.71 for 5 x 10 -6 M) was statistically significant (Tukey test, P -6 and 5 x 10 -6 M; Tukey test, P < 0.05). These two parameters tended to increase together (Pearson correlation = 0.702, P < 0.05). The results suggest that the induction of abnormal frustules could be associated with the genotoxic effects of MH. The alterations observed could be related to the effects of MH on the synthesis of the proteins involved in frustule formation or in the regulation of the cytoskeleton of the diatom cells

  7. Metatranscriptomes reveal functional variation in diatom communities from the Antarctic Peninsula

    KAUST Repository

    Pearson, Gareth A

    2015-04-14

    Functional genomics of diatom-dominated communities fromthe Antarctic Peninsula was studied using comparative metatranscriptomics. Samples obtained from diatom-rich communities in the Bransfield Strait, the western Weddell Sea and sea ice in the Bellingshausen Sea/Wilkins Ice Shelf yielded more than 500K pyrosequencing reads that were combined to produce a global metatranscriptome assembly. Multi-gene phylogenies recovered three distinct communities, and diatom-assigned contigs further indicated little read-sharing between communities, validating an assembly-based annotation and analysis approach. Although functional analysis recovered a core of abundant shared annotations that were expressed across the three diatom communities, over 40% of annotations (but accounting for <10% of sequences) were community-specific. The two pelagic communities differed in their expression of N-metabolism and acquisition genes, which was almost absent in post-bloom conditions in the Weddell Sea community, while enrichment of transporters for ammonia and urea in Bransfield Strait diatoms suggests a physiological stance towards acquisition of reduced N-sources. The depletion of carbohydrate and energy metabolism pathways in sea ice relative to pelagic communities, together with increased light energy dissipation (via LHCSR proteins), photorespiration, and NO3 - uptake and utilization all pointed to irradiance stress and/or inorganic carbon limitation within sea ice. Ice-binding proteins and cold-shock transcription factors were also enriched in sea ice diatoms. Surprisingly, the abundance of gene transcripts for the translational machinery tracked decreasing environmental temperature across only a 4 °C range, possibly reflecting constraints on translational efficiency and protein production in cold environments. © 2015 International Society for Microbial Ecology All rights reserved.

  8. Red and green algal origin of diatom membrane transporters: insights into environmental adaptation and cell evolution.

    Directory of Open Access Journals (Sweden)

    Cheong Xin Chan

    Full Text Available Membrane transporters (MTs facilitate the movement of molecules between cellular compartments. The evolutionary history of these key components of eukaryote genomes remains unclear. Many photosynthetic microbial eukaryotes (e.g., diatoms, haptophytes, and dinoflagellates appear to have undergone serial endosymbiosis and thereby recruited foreign genes through endosymbiotic/horizontal gene transfer (E/HGT. Here we used the diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum as models to examine the evolutionary origin of MTs in this important group of marine primary producers. Using phylogenomics, we used 1,014 diatom MTs as query against a broadly sampled protein sequence database that includes novel genome data from the mesophilic red algae Porphyridium cruentum and Calliarthron tuberculosum, and the stramenopile Ectocarpus siliculosus. Our conservative approach resulted in 879 maximum likelihood trees of which 399 genes show a non-lineal history between diatoms and other eukaryotes and prokaryotes (at the bootstrap value ≥70%. Of the eukaryote-derived MTs, 172 (ca. 25% of 697 examined phylogenies have members of both red/green algae as sister groups, with 103 putatively arising from green algae, 19 from red algae, and 50 have an unresolved affiliation to red and/or green algae. We used topology tests to analyze the most convincing cases of non-lineal gene history in which red and/or green algae were nested within stramenopiles. This analysis showed that ca. 6% of all trees (our most conservative estimate support an algal origin of MTs in stramenopiles with the majority derived from green algae. Our findings demonstrate the complex evolutionary history of photosynthetic eukaryotes and indicate a reticulate origin of MT genes in diatoms. We postulate that the algal-derived MTs acquired via E/HGT provided diatoms and other related microbial eukaryotes the ability to persist under conditions of fluctuating ocean chemistry, likely

  9. Anaerobic Nitrogen Turnover by Sinking Diatom Aggregates at Varying Ambient Oxygen Levels

    Directory of Open Access Journals (Sweden)

    Peter eStief

    2016-02-01

    Full Text Available In the world’s oceans, even relatively low oxygen (O2 levels inhibit anaerobic nitrogen cycling by free-living microbes. Sinking organic aggregates, however, might provide oxygen-depleted microbial hotspots in otherwise oxygenated surface waters. Here we show that sinking diatom aggregates can host anaerobic nitrogen cycling at ambient O2 levels well above the hypoxic threshold. Aggregates were produced from the ubiquitous diatom Skeletonema marinoi and the natural microbial community of seawater. Microsensor profiling through the center of sinking aggregates revealed internal anoxia at ambient 40% air saturation (~100 µmol O2 L-1 and below. Accordingly, anaerobic nitrate turnover inside the aggregates was evident within this range of ambient O2 levels. In incubations with 15N-labeled nitrate, individual Skeletonema aggregates produced NO2- (up to 10.7 nmol N h-1 per aggregate, N2 (up to 7.1 nmol N h-1, NH4+ (up to 2.0 nmol N h-1, and N2O (up to 0.2 nmol N h-1. Intriguingly, nitrate stored inside the diatom cells served as an additional, internal nitrate source for N2 production, which may partially uncouple anaerobic nitrate turnover by diatom aggregates from direct ambient nitrate supply. Sinking diatom aggregates can contribute directly to fixed-nitrogen loss in low-oxygen environments in the ocean and vastly expand the ocean volume in which anaerobic nitrogen turnover is possible, despite relatively high ambient O2 levels. Depending on the extent of intracellular nitrate consumption during the sinking process, diatom aggregates may also be involved in the long-distance export of nitrate to the deep ocean.

  10. Feeding, growth, and survival of post-larval abalone Haliotis asinina on different benthic diatoms

    Directory of Open Access Journals (Sweden)

    Emmanuel C. Capinpin, Jr.

    2007-12-01

    Full Text Available The feeding behavior, digestive efficiency, growth, and survival of post-larval abalone Haliotis asininafed with 5 species of locally isolated benthic diatom strains (Navicula mollis, N. ramosissima, Stauroneissp., Pleurosigma sp., and Cocconeis sp. were examined in the laboratory. Two 15-day feeding trialsusing 1 mm post-larvae were conducted. No significant differences were observed in sizes of post-larvalabalone after 15 days in all diatom treatments (P>0.05. However, in both trials, Cocconeis sp. resulted inhigh survival rates (88.9±5.6% and 80.0±20.0% for Trials 1 and 2, respectively. Cocconeis sp. wasefficiently digested by post-larval abalone, with most of the cells being ruptured during ingestion and/orpassage through the gut. One diatom strain, Pleurosigma sp., resulted to a high survival but producedthe slowest growth rate (<10 ìm.d-1 SL. It was probably not ingested easily during the experiment due toits large size or mobility. For the other diatom strains, N. mollis and N. ramosissima, most cells passedthrough the gut with the cells left intact. Stauroneis sp. is highly digestible, but did not result to highsurvival, although the remaining live post-larval abalone fed on this diatom as well as on N. mollis grewfaster during the second week of both feeding trials. N. ramosissima resulted to poorest survival rate(<10% due to its poor digestibility. Only Cocconeis sp. showed a fairly high growth rate, digestionefficiency, and survival rate. N. mollis which gave a fairly high survival rate and Stauroneis may be addedtowards the later stages of post-larval rearing as well as other large diatoms. The digestion efficiency ofdiatom strains is considered an important factor determining its dietary value, but other factors may alsobe important such as volume contents, biochemical composition, and other physical characteristics.

  11. Metatranscriptomes reveal functional variation in diatom communities from the Antarctic Peninsula

    KAUST Repository

    Pearson, Gareth A; Lago-Leston, Asuncion; Cá novas, Fernando; Cox, Cymon J; Verret, Frederic; Lasternas, Sebastian; Duarte, Carlos M.; Agusti, Susana; Serrã o, Ester A

    2015-01-01

    Functional genomics of diatom-dominated communities fromthe Antarctic Peninsula was studied using comparative metatranscriptomics. Samples obtained from diatom-rich communities in the Bransfield Strait, the western Weddell Sea and sea ice in the Bellingshausen Sea/Wilkins Ice Shelf yielded more than 500K pyrosequencing reads that were combined to produce a global metatranscriptome assembly. Multi-gene phylogenies recovered three distinct communities, and diatom-assigned contigs further indicated little read-sharing between communities, validating an assembly-based annotation and analysis approach. Although functional analysis recovered a core of abundant shared annotations that were expressed across the three diatom communities, over 40% of annotations (but accounting for <10% of sequences) were community-specific. The two pelagic communities differed in their expression of N-metabolism and acquisition genes, which was almost absent in post-bloom conditions in the Weddell Sea community, while enrichment of transporters for ammonia and urea in Bransfield Strait diatoms suggests a physiological stance towards acquisition of reduced N-sources. The depletion of carbohydrate and energy metabolism pathways in sea ice relative to pelagic communities, together with increased light energy dissipation (via LHCSR proteins), photorespiration, and NO3 - uptake and utilization all pointed to irradiance stress and/or inorganic carbon limitation within sea ice. Ice-binding proteins and cold-shock transcription factors were also enriched in sea ice diatoms. Surprisingly, the abundance of gene transcripts for the translational machinery tracked decreasing environmental temperature across only a 4 °C range, possibly reflecting constraints on translational efficiency and protein production in cold environments. © 2015 International Society for Microbial Ecology All rights reserved.

  12. Energetics of silicate melts from thermal diffusion studies. Final report

    International Nuclear Information System (INIS)

    Walker, D.

    1997-01-01

    Initially this project was directed towards exploiting Soret diffusion of silicate liquids to learn about the internal energetics of the constituents of the liquids. During the course of this project this goal was realized at the same time a series of intellectual and technical developments expanded the scope of the undertaking. Briefly recapping some of the highlights, the project was initiated after the discovery that silicate liquids were strongly Soret-active. It was possible to observe the development of strong diffusive gradients in silicate liquid composition in response to laboratory-imposed thermal gradients. The character of the chemical separations was a direct window into the internal speciation of the liquids; the rise time of the separation was a useful entree to quantitatively measuring chemical diffusivity; and the steady state magnitude of the separation proved to be an excellent determinant of the constituents' mixing energies. A comprehensive program was initiated to measure the separations, rise times, and mixing energies of a range of geologically and technically interesting silicate liquids. An additional track of activities in the DOE project has run in parallel to the Soret investigation of single-phase liquids in a thermal gradient. This additional track is the study of liquid-plus-crystal systems in a thermal gradient. In these studies solubility-driven diffusion introduced many useful effects, some quite surprising. In partially molten silicate liquids the authors applied their experiments to understanding magmatic cumulate rocks. They have also applied their understanding of these systems to aspects of evaporite deposits in the geological record. They also undertook studies of this sort in systems with retrograde solubility in order to form the basis for understanding remediation for brine migration problems in evaporite-hosted nuclear waste repositories such as the WIPP

  13. Wastewater reuse in liquid sodium silicate manufacturing in alexandria, egypt.

    Science.gov (United States)

    Ismail, Gaber A; Abd El-Salam, Magda M; Arafa, Anwar K

    2009-01-01

    Soluble sodium silicates (waterglass) are liquids containing dissolved glass which have some water like properties. They are widely used in industry as sealants, binders, deflocculants, emulsifiers and buffers. Their most common applications in Egypt are in the pulp and paper industry (where they improve the brightness and efficiency of peroxide bleaching) and the detergent industry, in which they improve the action of the detergent and lower the viscosity of liquid soaps. The survey results showed that the production was carried out batch-wise, in an autoclave (dissolver). Sodium silicate in the state of crushed glass was charged in an autoclave (dissolver) with sodium hydroxide and water. The product is filtered through a press. The left over sludge (mud and silicates impurities) is emptied into the local sewer system. Also, sludge (silica gel) was discharged from the neutralization process of the generated alkaline wastewater and consequently clogging the sewerage system. So this study was carried out to modify the current wastewater management system which eliminates sludge formation, the discharge of higher pH wastewater to the sewer system, and to assess its environmental and economic benefits. To assess the characteristics of wastewater to be reused, physico-chemical parameters of 12 samples were tested using standard methods. The survey results showed that a total capacity of the selected enterprise was 540 tons of liquid sodium silicates monthly. The total amount of wastewater being discharged was 335 m3/month. Reusing of wastewater as feed autoclave water reduced water consumption of 32.1% and reduced wastewater discharge/month that constitutes 89.6% as well as saving in final product of 6 ton/month. It was concluded that reusing of wastewater generated from liquid sodium silicate manufacturing process resulted in cheaper and environmental-friendly product.

  14. Silicate Phases on the Surfaces of Trojan Asteroids

    Science.gov (United States)

    Martin, Audrey; Emery, Joshua P.; Lindsay, Sean S.

    2017-10-01

    Determining the origin of asteroids provides an effective means of constraining the solar system’s dynamic past. Jupiter Trojan asteroids (hereafter Trojans) may help in determining the amount of radial mixing that occurred during giant planet migration. Previous studies aimed at characterizing surface composition show that Trojans have low albedo surfaces and are spectrally featureless in the near infrared. The thermal infrared (TIR) wavelength range has advantages for detecting silicates on low albedo asteroids such as Trojans. The 10 μm region exhibits strong features due to the Si-O fundamental molecular vibrations. Silicates that formed in the inner solar system likely underwent thermal annealing, and thus are crystalline, whereas silicates that accreted in the outer solar system experienced less thermal processing, and therefore are more likely to have remained in an amorphous phase. We hypothesize that the Trojans formed in the outer solar system (i.e., the Kuiper Belt), and therefore will have a more dominant amorphous spectral silicate component. With TIR spectra from the Spitzer Space Telescope, we identify mineralogical features from the surface of 11 Trojan asteroids. Fine-grain mixtures of crystalline pyroxene and olivine exhibit a 10 μm feature with sharp cutoffs between about 9 μm and 12 μm, which create a broad flat plateau. Amorphous phases, when present, smooth the sharp emission features, resulting in a dome-like shape. Preliminary results indicate that the surfaces of analyzed Trojans contain primarily amorphous silicates. Emissivity spectra of asteroids 1986 WD and 4709 Ennomos include small peaks in the 10 μm region, diagnostic of small amounts of crystalline olivine. One explanation is that Trojans formed in the same region as Kuiper Belt objects, and when giant planet migration ensued, they were swept into Jupiter’s stable Lagrange points where they are found today. As such, it is possible that an ancestral group of Kuiper Belt

  15. Interaction of a dinoflagellate neurotoxin with voltage-activated ion channels in a marine diatom.

    Science.gov (United States)

    Kitchen, Sheila A; Bourdelais, Andrea J; Taylor, Alison R

    2018-01-01

    The potent neurotoxins produced by the harmful algal bloom species Karenia brevis are activators of sodium voltage-gated channels (VGC) in animals, resulting in altered channel kinetics and membrane hyperexcitability. Recent biophysical and genomic evidence supports widespread presence of homologous sodium (Na + ) and calcium (Ca 2+ ) permeable VGCs in unicellular algae, including marine phytoplankton. We therefore hypothesized that VGCs of these phytoplankton may be an allelopathic target for waterborne neurotoxins produced by K. brevis blooms that could lead to ion channel dysfunction and disruption of signaling in a similar manner to animal Na + VGCs. We examined the interaction of brevetoxin-3 (PbTx-3), a K. brevis neurotoxin, with the Na + /Ca 2+ VGC of the non-toxic diatom Odontella sinensi s using electrophysiology. Single electrode current- and voltage- clamp recordings from O. sinensis in the presence of PbTx-3 were used to examine the toxin's effect on voltage gated Na + /Ca 2+ currents. In silico analysis was used to identify the putative PbTx binding site in the diatoms. We identified Na + /Ca 2+ VCG homologs from the transcriptomes and genomes of 12 diatoms, including three transcripts from O. sinensis and aligned them with site-5 of Na + VGCs, previously identified as the PbTx binding site in animals. Up to 1 µM PbTx had no effect on diatom resting membrane potential or membrane excitability. The kinetics of fast inward Na + /Ca 2+ currents that underlie diatom action potentials were also unaffected. However, the peak inward current was inhibited by 33%, delayed outward current was inhibited by 25%, and reversal potential of the currents shifted positive, indicating a change in permeability of the underlying channels. Sequence analysis showed a lack of conservation of the PbTx binding site in diatom VGC homologs, many of which share molecular features more similar to single-domain bacterial Na + /Ca 2+ VGCs than the 4-domain eukaryote channels

  16. The fascinating diatom frustule—can it play a role for attenuation of UV radiation?

    DEFF Research Database (Denmark)

    Ellegaard, Marianne; Lenau, Torben Anker; Lundholm, Nina

    2016-01-01

    size range as wave lengths of visible and ultraviolet (UV) light. This has prompted research into the possible role of the frustule in mediating light for the diatoms’ photosynthesis as well as into possible photonic applications of the diatom frustule. One of the possible biological roles, as well...... as area of potential application, is UV protection. In this review, we explore the possible adaptive value of the silica frustule with focus on research on the effect of UV radiation ondiatoms. We also explore the possible effect of the frustules on UV radiation, from a theoretical, biological......, and applied perspective, including recent experimental data on UV transmission of diatom frustules....

  17. A mesoscale iron enrichment in the western subarctic Pacific induces a large centric diatom bloom.

    Science.gov (United States)

    Tsuda, Atsushi; Takeda, Shigenobu; Saito, Hiroaki; Nishioka, Jun; Nojiri, Yukihiro; Kudo, Isao; Kiyosawa, Hiroshi; Shiomoto, Akihiro; Imai, Keiri; Ono, Tsuneo; Shimamoto, Akifumi; Tsumune, Daisuke; Yoshimura, Takeshi; Aono, Tatsuo; Hinuma, Akira; Kinugasa, Masatoshi; Suzuki, Koji; Sohrin, Yoshiki; Noiri, Yoshifumi; Tani, Heihachiro; Deguchi, Yuji; Tsurushima, Nobuo; Ogawa, Hiroshi; Fukami, Kimio; Kuma, Kenshi; Saino, Toshiro

    2003-05-09

    We have performed an in situ test of the iron limitation hypothesis in the subarctic North Pacific Ocean. A single enrichment of dissolved iron caused a large increase in phytoplankton standing stock and decreases in macronutrients and dissolved carbon dioxide. The dominant phytoplankton species shifted after the iron addition from pennate diatoms to a centric diatom, Chaetoceros debilis, that showed a very high growth rate, 2.6 doublings per day. We conclude that the bioavailability of iron regulates the magnitude of the phytoplankton biomass and the key phytoplankton species that determine the biogeochemical sensitivity to iron supply of high-nitrate, low-chlorophyll waters.

  18. Consistent quantum approach to new laser-electron-nuclear effects in diatomic molecules

    International Nuclear Information System (INIS)

    Glushkov, A V; Malinovskaya, S V; Loboda, A V; Shpinareva, I M; Prepelitsa, G P

    2006-01-01

    We present a consistent, quantum approach to the calculation of electron-nuclear γ. spectra (set of vibrational and rotational satellites) for nuclei in diatomic molecules. The approach generelizes the well known Letokhov-Minogin model and is based on the Dunham model potential approximation for potential curves of diatomic molecules. The method is applied to the calculation of probabilities of the vibration-rotation-nuclear transitions in a case of emission and absorption spectrum for the nucleus 127 I (E γ (0) = 203 keV) linked with the molecule H 127 I

  19. Distribution of Epilithic Diatoms in Estuaries of the Korean Peninsula in Relation to Environmental Variables

    Directory of Open Access Journals (Sweden)

    Ha-Kyung Kim

    2015-11-01

    Full Text Available This study explores the relationships between environmental factors and the distribution of epilithic diatoms in 161 estuaries of three coastal areas on the Korean peninsula. We investigated epilithic diatoms, water quality, and land use in the vicinities of the estuaries during the months of May 2012, 2013 and 2014, because Korea is relatively free from the influences of rainfall at that time of year. We recorded 327 diatom taxa from the study sites, and the assemblage was dominated by members of the Naviculaceae. Bacillariaceae accounted for the largest proportion of diatoms, and Nitzschia inconspicua (18% and N. frustulum (9.6% were the most dominant species. A cluster analysis based on epilithic diatom abundance suggested that the epilithic diatom communities of Korean estuaries can be classified into four large groups (G according to geography, as follows: Ia—the East Sea watershed, Ib—the eastern watershed of the South Sea, IIa—the West Sea watershed, and IIb—the western watershed of the South Sea. The former two groups, Ia and Ib, showed higher proportions of forest land cover and use, higher species occurrence, lower salinity, lower turbidity, and lower concentrations of nutrients than the latter two groups, while the latter groups, IIa and IIb, had higher proportions of agricultural land cover and use, higher electrical conductivity, higher turbidity, higher concentrations of nutrients, and lower species occurrence. The environmental factors underlying the distribution of epilithic diatoms, representative of each region, are as follows: dissolved oxygen and forest land cover and use for Reimeria sinuate and Rhoicosphenia abbreviate of the East Sea (ES, salinity and turbidity for Tabularia fasciculate of the West Sea (WS, and biochemical oxygen demand (BOD and nutrients for Cyclotella meneghiniana of the WS. On the other hand, the most influential environmental factors affecting the occurrence of indicator species showing the

  20. Anaerobic nitrogen turnover by sinking diatom aggregates at varying ambient oxygen levels

    DEFF Research Database (Denmark)

    Stief, Peter; Kamp, Anja; Thamdrup, Bo

    2016-01-01

    nitrate supply. Sinking diatom aggregates can contribute directly to fixed-nitrogen loss in low-oxygen environments in the ocean and vastly expand the ocean volume in which anaerobic nitrogen turnover is possible, despite relatively high ambient oxygen levels. Depending on the extent of intracellular......In the world’s oceans, even relatively low oxygen levels inhibit anaerobic nitrogen cycling by free-living microbes. Sinking organic aggregates, however, might provide oxygen-depleted microbial hotspots in otherwise oxygenated surface waters. Here, we show that sinking diatom aggregates can host...