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Sample records for laminated diatom ooze

  1. A rapidly deposited pennate diatom ooze in Upper Miocene-Lower Pliocene sediment beneath the North Pacific polar front

    USGS Publications Warehouse

    Dickens, G.R.; Barron, J.A.

    1997-01-01

    Rapidly deposited Thalassionema-Thalassiothrix pennate diatom oozes previously have been described in Upper Miocene-Lower Pliocene sediment beneath the frontal boundary of the eastern equatorial Pacific. Here we document a new occurrence of Thalassionema-Thalassiothrix ooze in Upper Miocene Lower Pliocene sediment beneath the frontal boundary of the subarctic North Pacific. The ooze is a 6 m interval of siliceous sediment at Ocean Drilling Program (ODP) sites 885/886 that was rapidly deposited between approximately 5.0 and 5.9 Ma. Bulk sediment in this interval may contain greater than 85% pennate diatom tests. There are also abundant laminae and pockets that are composed entirely of Thalassionema and Thalassiothrix diatoms. The presence of a rapidly deposited ooze dominated by pennate diatoms indicates unusual past conditions in the overlying surface waters. Time coincident deposition of such oozes at two distinct frontal boundary locations of the Pacific suggests that the unusual surface water conditions were causally linked to large-scale oceanographic change. This same oceanographic change most likely involved (1) addition of nutrients to the ocean, or (2) redistribution of nutrients within the ocean. The occurrence and origin of pennate diatom oozes may be a key component to an integrative understanding of late Neogene paleoceanography and biogeochemical cycling.

  2. Microscopic observation of laminated sediment in thin section using diatom assemblages to reconstruct annual paleoenvironmental changes

    NASA Astrophysics Data System (ADS)

    Ishikawa, S.; Kaoru, K.

    2013-12-01

    Eastern Hokkaido is a severe earthquake and tsunami district. Lake Harutori, located in eastern Hokkaido, records 22 traces of huge tsunamis in lake sediment since 9500 years ago. The latest event was occurred in 17th century (e.g. Nanayama et al., 2003). However, the strict age is still unknown, because the autochthon Ainu culture did not have literature. In lake sediment, there is laminated structure between tsunami deposits, and also on the 17th huge tsunami deposit. If this laminated structure was recognized as annual varve, it will be able to decide the strict age and reconstruct the paleoenvironment in high resolution. Large thin section 165 mm length was made included 17th tsunami deposits, laminated silt layer and age known tephra and observed lithofacies and diatoms with 1,000 magnification light microscope. The thin section comprised from 80 mm thick tsunami deposit in bottom, 60 mm thick laminated silt layer, 15 mm tephra as known as Ta-b fallen in 1667A.D. and 10 mm laminated silt layer at the top. As the result of optical observation to laminated silt layer, 31 laminated structures were recognized. Inferred from diatom assemblages, 37 cyclic productions were recognized. Diatom components were apparently changed from bottom to top and were seemed to influence by the changes of lake water conditions after tsunami inundation. These results indicate that the start of accumulation of laminated silt layer and/or the end of confusion of lake water by tsunami current was around 1630 A.D.; 37 years before 1667 A.D.. This earthquake was separated from the 1611 Keicho Sanriku earthquake was well known in this era and the hypocenters of these earthquakes need to reexam.

  3. Diatoms

    USGS Multimedia Gallery

    Diatoms are algae that reflect the biotic condition of streams, lakes and estuaries. Diatoms are important indicator organisms because they are sensitive to natural and human impacts, and monitoring their condition provides information about ecosystem health....

  4. Diatoms

    USGS Multimedia Gallery

    Diatoms are algae that reflect the biotic condition of streams, lakes and estuaries. Diatoms are important indicator organisms because they are sensitive to natural and human impacts, and monitoring their condition provides information about ecosystem health. Diatoms can live in permanently ice-cove...

  5. Diatoms

    USGS Multimedia Gallery

    Diatoms are algae that reflect the biotic condition of streams, lakes and estuaries. Diatoms are important indicator organisms because they are sensitive to natural and human impacts, and monitoring their condition provides information about ecosystem health. A scanning electron micrograph (SEM) sho...

  6. Diatoms

    USGS Multimedia Gallery

    Diatoms are algae that reflect the biotic condition of streams, lakes and estuaries. Diatoms are important indicator organisms because they are sensitive to natural and human impacts, and monitoring their condition provides information about ecosystem health. A large, living Pleurosira laevis cell h...

  7. Diatoms

    USGS Multimedia Gallery

    Diatoms are algae that reflect the biotic condition of streams, lakes and estuaries. Diatoms are important indicator organisms because they are sensitive to natural and human impacts, and monitoring their condition provides information about ecosystem health. Shown here is a live cell of Didymosphen...

  8. Revised Ages for Laminated Sediment and a Holocene-Marker Diatom from the Northern California Continental Slope

    USGS Publications Warehouse

    Hemphill-Haley, E.; Gardner, J.V.

    1994-01-01

    Conventional and accelerator mass spectrometry 14C ages indicate that laminated sediment in three cores from the northern California continental slope near 38??N and 39??N were deposited between 42,000 and 25,000 yr B.P. This revises and refines our previous estimates that laminated sediment accumulated during the late Pleistocene to early Holocene (J. V. Gardner and E. Hemphill-Haley, 1986, Geology 14, 691-694). Preservation of laminated sediment on the upper slope in this area suggests a period of intense coastal upwelling, high primary productivity, and resultant depletion of oxygen in bottomwaters preceding the onset of global glacial conditions. The transition from Pleistocene to Holocene conditions, and the establishment of a modern climatic regime driven by the California Current, included the incursion of the subtropical diatom, Pseudoeunotia doliola. P. doliola is common in sediment younger than about 10,000 yr and thus is a reliable marker species for identifying Holocene deposits off northern California.

  9. The silicon isotope composition of Ethmodiscus rex laminated diatom mats from the tropical West Pacific: Implications for silicate cycling during the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Xiong, Zhifang; Li, Tiegang; Algeo, Thomas; Doering, Kristin; Frank, Martin; Brzezinski, Mark A.; Chang, Fengming; Opfergelt, Sophie; Crosta, Xavier; Jiang, Fuqing; Wan, Shiming; Zhai, Bin

    2015-07-01

    The cause of massive blooms of Ethmodiscus rex laminated diatom mats (LDMs) in the eastern Philippine Sea (EPS) during the Last Glacial Maximum (LGM) remains uncertain. In order to better understand the mechanism of formation of E. rex LDMs from the perspective of dissolved silicon (DSi) utilization, we determined the silicon isotopic composition of single E. rex diatom frustules (δ30SiE. rex) from two sediment cores in the Parece Vela Basin of the EPS. In the study cores, δ30SiE. rex varies from -1.23‰ to -0.83‰ (average -1.04‰), a range that is atypical of marine diatom δ30Si and that corresponds to the lower limit of reported diatom δ30Si values of any age. A binary mixing model (upwelled silicon versus eolian silicon) accounting for silicon isotopic fractionation during DSi uptake by diatoms was constructed. The binary mixing model demonstrates that E. rex dominantly utilized DSi from eolian sources (i.e., Asian dust) with only minor contributions from upwelled seawater sources (i.e., advected from Subantarctic Mode Water, Antarctic Intermediate Water, or North Pacific Intermediate Water). E. rex utilized only ~24% of available DSi, indicating that surface waters of the EPS were eutrophic with respect to silicon during the LGM. Our results suggest that giant diatoms did not always use a buoyancy strategy to obtain nutrients from the deep nutrient pool, thus revising previously proposed models for the formation of E. rex LDMs.

  10. Experimental formation of chalk from calcareous ooze. Technical progress report

    SciTech Connect

    Seyfried, W.E.; Johnson, T.C.

    1981-02-15

    Samples of calcareous ooze collected from the tropical and equatorial Atlantic Ocean were subjected to hydrothermal alteration in order to simulate the diagenesis of chalk. Changes in mineralogy and morphology of enclosed microfossils were measured. (ACR)

  11. Late Quaternary Biosiliceous Laminated Marine Sediments From Antarctica: Seasonality During a Period of Rapid Climate Change

    NASA Astrophysics Data System (ADS)

    Pike, J.; Stickley, C. E.; Maddison, E. J.; Leventer, A.; Brachfeld, S.; Domack, E. W.; Dunbar, R. B.; Manley, P. L.; McClennen, C.

    2004-12-01

    The Antarctic ice sheet plays a key role in global oceanic and atmosphere systems. One of the most dynamic regions of the continent is the Antarctic Peninsula (AP) where ecological and cryospheric systems respond rapidly to climate change, such as the last deglaciation ( 12-13 kyr BP). Here, deglacial laminated diatom-rich marine sediments are well known, e.g., Palmer Deep (64 S 64 W; ODP Hole 1098A) comprising a distinctive 3 m thick sequence of deglacial `couplet' laminations. The East Antarctic margin (EAM), however, has received less attention than the West Antarctic margin (WAM) in palaeoceanographic studies yet its role in deep ocean circulation and, therefore, the global ocean system is significant. Recent sediment cores recovered from EAM sites during NSF Polar Programs-funded cruise NBP0101 in February and March 2001 (e.g. Mertz Drift \\{66 S 143 E\\}, Svenner Channel \\{69 S 77 E\\} in Prydz Bay, Nielsen Basin \\{67 S 66 E\\} and Iceberg Alley \\{67 S 63 E\\}), reveal that a similar sedimentary facies was deposited along the EAM, in similar geomorphological settings to Palmer Deep, during the same timeframe. These rich sediment archives reveal clues about circum-Antarctic palaeoceanographic change during the last deglaciation, a time of both high silica flux and rapid climate change. Microfabrics and diatom assemblages from scanning electron microscope backscattered and secondary electron imagery analysis of coeval deglacial varves from Palmer Deep (WAM), Mertz-Ninnis Trough and Iceberg Alley (EAM) are presented and compared. The varves from these localities are characterised by laminae to thin beds of orange-brown diatom ooze up to 8cm thick alternating with blue-grey diatom-bearing terrigenous sediments up to 4cm thick. The orange-brown oozes are dominated by resting spores and vegetative valves of Hyalochaete Chaetoceros spp., resulting from spring sedimentation associated with stratified surface waters promoting exceptionally high primary productivity. The blue-grey terrigenous sediments contain mixed open-water Antarctic diatoms resulting from summer/autumn sedimentation associated with increased terrigenous input and the annual trend to more oligotrophic conditions. The significance of these biogenic seasonal and annual cyclicities will be discussed in terms of interannual palaeoclimate oscillations. Sub-seasonality and a related deglacial trend are apparent within the spring lamine from the EAM and in the summer/autumn laminae from the WAM. This circum-Antarctic asymmetry indicates differences in the nature and timing of oceanographic and cryospheric systems operating around the Antarctic continent at this time.

  12. Potential role of giant marine diatoms in sequestration of atmospheric CO2 during the Last Glacial Maximum: ?13C evidence from laminated Ethmodiscus rex mats in tropical West Pacific

    NASA Astrophysics Data System (ADS)

    Xiong, Zhifang; Li, Tiegang; Crosta, Xavier; Algeo, Thomas; Chang, Fengming; Zhai, Bin

    2013-09-01

    Giant marine diatoms, blooming or aggregating within deep chlorophyll maxima under stratified conditions, can generate substantial production and a large export flux of organic carbon from surface waters. However, their role in regulating glacial-interglacial variation in atmospheric pCO2 remains unclear. Here, we report the organic carbon isotopic compositions of Ethmodiscus rex diatoms (?13CE. rex) and bulk sediments (?13Corg) from a sediment core in the eastern Philippine Sea dated to ~ 19.5-31.0 kyr B.P. and consisting of (from youngest to oldest) (1) laminated E. rex diatom mats (LDM), (2) diatomaceous clay (DC), and (3) pelagic clay (PC). Our results suggest that ?13CE. rex provides a better record of palaeoceanographic processes during LDM and DC deposition than ?13Corg because of reduced differential vital effects in near-monospecific E. rex fractions. We used the isotopic composition of the coarse E. rex fraction (?13CE. rex (> 154 ?m)) to calculate the CO2 partial pressure of eastern Philippine Sea surface waters (pCO2-sw) during the Last Glacial Maximum (LGM). Our pCO2-sw records suggest that the eastern Philippine Sea switched from being a strong CO2 source during DC deposition to a weak CO2 sink during LDM deposition. The role of the eastern Philippine Sea as a CO2 sink during the LGM was promoted by elevated primary production and, to a lesser extent, intensified water-column stratification. These observations highlight the potential role of giant marine diatoms in the sequestration of atmospheric CO2 during the LGM and, hence, support changes in biogenic silica fluxes as a potential cause of lower glacial atmospheric CO2. Our findings are consistent with an eolian source of silica, as proposed by the silica hypothesis and the silicon-induced alkalinity pump hypothesis but not by the silicic acid leakage hypothesis.

  13. Current and sea-level signals in periplatform ooze (Neogene, Maldives, Indian Ocean)

    NASA Astrophysics Data System (ADS)

    Betzler, Christian; Ldmann, Thomas; Hbscher, Christian; Frstenau, Jrn

    2013-05-01

    Periplatform ooze is an admixture of pelagic carbonate and sediment derived from neritic carbonate platforms. Compositional variations of periplatform ooze allow the reconstruction of past sea-level changes. Periplatform ooze formed during sea-level highstands is finer grained and richer in aragonite through the elevated input of material from the flooded platform compared to periplatform ooze formed during the episodes of lowered sea level. In many cases, however, the sea floor around carbonate platforms is subjected to bottom currents which are expected to affect sediment composition, i.e. through winnowing of the fine fraction. The interaction of sea-level driven highstand shedding and current impact on the formation of periplatform ooze has hitherto not been analyzed. To test if a sea-level driven input signal in periplatform ooze is influenced or even distorted by changing current activity, an integrated study using seismic, hydroacoustic and sedimentological data has been performed on periplatform ooze deposited in the Inner Sea of the Maldives. The Miocene to Pleistocene succession of drift deposits is subdivided into nine units; limits of seismostratigraphic units correspond to changes or turnarounds in grain size trends in cores recovered at ODP Site 716 and NEOMA Site 1143. For the Pleistocene it can be shown how changes in grain size occur in concert with sea-level changes and changes of the monsoonal system, which is thought to be a major driver of bottom currents in the Maldives. A clear highstand shedding pattern only appears in the data at a time of relaxation of monsoonal strength during the last 315 ky. Results imply (1) that drift sediments provide a potential target for analyzing past changes in oceanic currents and (2) that the ooze composition bears a mixed signal of input and physical winnowing at the sea floor.

  14. Organic geochemical studies on kerogen precursors in recently deposited algal mats and oozes

    NASA Technical Reports Server (NTRS)

    Philp, R. P.; Calvin, M.; Brown, S.; Yang, E.

    1978-01-01

    The same kerogen-like residue from the algal mats and oozes at Laguna Mormona, Baja California, is examined following degradation by saponification, alkaline KMnO4 oxidation, and HBr treatment. For comparison, pyrolytic degradation is performed for the residue and five others, two of which are obtained from algal mats at Baffin Bay, Texas. Major conclusions are that (1) Saponification of a residue specimen from the algal-ooze residue results in minor amounts of components bonded to it as esters; (2) Alkaline KMnO4 oxidation reveals that the same residue consists of a cross-linked aliphatic nucleus with additional components attached to it as esters; (3) the major products from pyrolysis of the residue include phytenes, pristenes, sterenes, and triterpenes; and (4) the HBr treatment yielded only one product, indicating the absence of a large number of ether-linkages readily cleaved by HBr.

  15. Invertebrate lamins

    SciTech Connect

    Melcer, Shai; Gruenbaum, Yosef . E-mail: gru@vms.huji.ac.il; Krohne, Georg . E-mail: krohne@biozentrum.uni-wuerzburg.de

    2007-06-10

    Lamins are the main component of the nuclear lamina and considered to be the ancestors of all intermediate filament proteins. They are localized mainly at the nuclear periphery where they form protein complexes with integral proteins of the nuclear inner membrane, transcriptional regulators, histones and chromatin modifiers. Studying lamins in invertebrate species has unique advantages including the smaller number of lamin genes in the invertebrate genomes and powerful genetic analyses in Caenorhabditis elegans and Drosophila melanogaster. These simpler nuclear lamina systems allow direct analyses of their structure and functions. Here we give an overview of recent advances in the field of invertebrate nuclear lamins with special emphasis on their evolution, assembly and functions.

  16. Photoresist laminate

    DOEpatents

    Andrade, A.D.; Galbraith, L.K.

    1979-10-01

    The disclosure relates to a laminated negative dry-film photoresist for the production of thick, as well as thin, patterns with vertical sidewalls. Uniform depthwise exposure in a photoresist layer is effected by the use of an ultraviolet filtering top layer.

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

    NASA Astrophysics Data System (ADS)

    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, which point to specific scenarios involving e.g. changes in the food web that can be related to warmer surface water temperatures. Such warming of shelf waters may be related with an overshooting Atlantic Meridional Overturning Circulation (AMOC) and strong injection of warmer North Atlantic Deep Water into the Southern Ocean water masses at Termination I as reported by [2]. Such finding may highlight the effects of AMOC changes on Antarctic ice shelf extent and coastal ecosystems. [1] Hillenbrand et al., 2010. J. Quat. Sci. 25 (3), 280-295. [2] Barker et al., 2010. Nature Geosci. 3, 567-571.

  18. Laminate article

    DOEpatents

    Williams, Robert K.; Paranthaman, Mariappan; Chirayil, Thomas G.; Lee, Dominic F.; Goyal, Amit; Feenstra, Roeland

    2002-01-01

    A laminate article comprises a substrate and a biaxially textured (RE.sub.x A.sub.(1-x)).sub.2 O.sub.2-(x/2) buffer layer over the substrate, wherein 0laminate article can include a layer of YBCO over the (RE.sub.x A.sub.(1-x)).sub.2 O.sub.2-(x/2) buffer layer. A layer of CeO.sub.2 between the YBCO layer and the (RE.sub.x A.sub.(1-x)).sub.2 O.sub.2-(x/2) buffer layer can also be include. Further included can be a layer of YSZ between the CeO.sub.2 layer and the (RE.sub.x A.sub.(1-x)).sub.2 O.sub.2-(x/2) buffer layer. The substrate can be a biaxially textured metal, such as nickel. A method of forming the laminate article is also disclosed.

  19. Monosulfidic black ooze accumulations in sediments of the Geographe Bay area, Western Australia.

    PubMed

    Ward, N J; Bush, R T; Burton, E D; Appleyard, S; Wong, S; Sullivan, L A; Cheeseman, P J

    2010-11-01

    Mobilisation of sedimentary monosulfidic black ooze (MBO) may result in rapid deoxygenation and acidification of surface waters, and release of potentially toxic metals. This study examines the extent and nature of MBO accumulation in the Geographe Bay area, Western Australia. MBO accumulations were found to be widespread in benthic sediments of the Geographe Bay area with acid-volatile sulfide (AVS) contents as high as 320 ?mol g(-1). The MBO materials often had unusually high dissolved sulfide (S(-II)) concentrations in their pore-waters (up to 610 mg L(-1)) and elevated elemental sulfur (S(0)) contents (up to 51 ?mol g(-1)). Dissolved S(-II) is able to accumulate due to limited iron availability and S(0) is largely its partial oxidation product. The availability of organic carbon and Fe limited MBO accumulation at many sites. A comparison of AVS and simultaneously extracted metal (SEM) concentrations has shown that metals are likely to be bound in sulfide complexes. PMID:20727554

  20. Diatoms (50 Species)

    USGS Multimedia Gallery

    Photomicrograph depicting the siliceous frustulesof fifty species of diatoms arranged within a circular shape. Diatoms form the base of many marine and aquatic food chains and upon death, their glassy frustules form sediments known as diatomaceous earth....

  1. Diatoms (50 Species)

    USGS Multimedia Gallery

    Photomicrograph depicting the siliceous frustules of fifty species of diatoms arranged within a circular shape. Diatoms form the base of many marine and aquatic food chains and upon death, their glassy frustules form sediments known as diatomaceous earth....

  2. Hybrid composite laminate structures

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F. (Inventor)

    1977-01-01

    An invention which relates to laminate structures and specifically to essentially anisotropic fiber composite laminates is described. Metal foils are selectively disposed within the laminate to produce increased resistance to high velocity impact, fracture, surface erosion, and other stresses within the laminate.

  3. Reduction in bacterial ooze formation on immature fruitlets after preventive treatments of Fosethyl-Al against fire blight Erwinia amylovora.

    PubMed

    Deckers, T; Schoofs, H; Verjans, W; De Maeyer, L

    2010-01-01

    Fire blight, caused by the bacterium Erwinia amylovora (Burill Winslow et al.), is a very important bacterial disease on apple and pear orchards with devastating effects in some production area and in some years. Fire blight control consists in a whole strategy of measures that should start with control measures in and around the fruit tree nurseries. Only the use of Vacciplant (Laminarin), an inducer of the self-defence mechanism, is registered in Belgium since 2009. In other European countries Fosethyl-Al has been registered for fire blight control. Recently, research trials have been done at Pcfruit research station for several years on the activity of ALiette (fosethyl-Al) against fire blight. Fosethyl-Al, also a plant defence enhancing molecule, applied preventively 3 times at a dose of 3.75 kg/ha standard orchard (3 x 3000 g a.i./ha standard orchard), showed a reduction in the host susceptibility and decreased the disease development on artificial inoculated flower clusters and shoots. Also a clear reduction in the ooze droplet formation on artificially inoculated immature fruitlets has been observed with this molecule. This reduction in the bacterial ooze formation is considered as a very important factor in the spread of the disease in the orchard. PMID:21534464

  4. Diatomic Spectral Database

    National Institute of Standards and Technology Data Gateway

    SRD 114 Diatomic Spectral Database (Web, free access)   All of the rotational spectral lines observed and reported in the open literature for 121 diatomic molecules have been tabulated. The isotopic molecular species, assigned quantum numbers, observed frequency, estimated measurement uncertainty, and reference are given for each transition reported.

  5. Diatoms (50 Species)

    USGS Multimedia Gallery

    A photomicrograph depicting the siliceous frustules of fifty species of diatoms arranged within a circular shape. The image has been inverted to white on black to bring out details. Diatoms form the base of many marine and aquatic foodchains and upon death, their glassy frustules form sediments know...

  6. Laminating the hippocampus.

    PubMed

    Frster, Eckart; Zhao, Shanting; Frotscher, Michael

    2006-04-01

    Lamination of neurons and fibre projections is a fundamental organizational principle of the mammalian cerebral cortex. A laminated organization is likely to be essential for cortical function, as studies in mutant mice have revealed causal relationships between lamination defects and functional deficits. Unveiling the determinants of the laminated cortical architecture will contribute to our understanding of how cortical functions have evolved in phylogenetic and ontogenetic development. Recently, the hippocampus, with its clearly segregated cell and fibre layers, has become a major subject of studies on cortical lamination. PMID:16543914

  7. Lamination cooling system

    DOEpatents

    Rippel, Wally E.; Kobayashi, Daryl M.

    2005-10-11

    An electric motor, transformer or inductor having a lamination cooling system including a stack of laminations, each defining a plurality of apertures at least partially coincident with apertures of adjacent laminations. The apertures define a plurality of cooling-fluid passageways through the lamination stack, and gaps between the adjacent laminations are sealed to prevent a liquid cooling fluid in the passageways from escaping between the laminations. The gaps are sealed by injecting a heat-cured sealant into the passageways, expelling excess sealant, and heat-curing the lamination stack. The apertures of each lamination can be coincident with the same-sized apertures of adjacent laminations to form straight passageways, or they can vary in size, shape and/or position to form non-axial passageways, angled passageways, bidirectional passageways, and manifold sections of passageways that connect a plurality of different passageway sections. Manifold members adjoin opposite ends of the lamination stack, and each is configured with one or more cavities to act as a manifold to adjacent passageway ends. Complex manifold arrangements can create bidirectional flow in a variety of patterns.

  8. Pasture-associated laminitis.

    PubMed

    Geor, Raymond J

    2009-04-01

    Laminitis is a painful and debilitating condition of horses and ponies that has major economic and welfare implications. Anecdotal observations and the results of survey studies have indicated that most laminitis cases occur in horses and ponies kept at pasture (hence, the term pasture-associated laminitis). Risk for development of pasture-associated laminitis represents a dynamic interaction between animal predisposing factors (an insulin-resistant phenotype commonly termed equine metabolic syndrome) and environmental conditions, particularly the nonstructural carbohydrate (simple sugars, starches, and fructans) content of pasture forage. Countermeasures for avoidance of pasture-associated laminitis involve (1) mitigation of metabolic predisposition (insulin resistance and obesity) in high-risk horses and ponies and (2) dietary and pasture grazing management strategies that minimize exposure to the dietary conditions known to trigger laminitis in susceptible animals. PMID:19303549

  9. Laminating Polyimide Films

    NASA Technical Reports Server (NTRS)

    St. Clair, A. K.; St. Clair, T. L.; Robinson, P. D.

    1983-01-01

    Thermoplastic polyimide adhesive is used to bond polyimide sheets into flexible laminates. Films are first primed with polyimide adhesive, then bonded together under heat and pressure. Adhesive is cast on separate surface, then sandwiched between polyimide and/or metal films for final assembly. Objectives of process are to improve bonding of high-temperature polyimide film, prepare flexible, large-area, void-free laminates from polyimide film, and laminate polyimide film not only to itself but to metal surfaces.

  10. DIATOM: A DIALOG Simulator.

    ERIC Educational Resources Information Center

    Waldstein, Robert

    1981-01-01

    Describes DIATOM, an online bibliographic retrieval system designed and implemented at Syracuse University to teach search strategy and the use of DIALOG to library science students. System features and database storage considerations are explained. (FM)

  11. Diatoms in comets

    NASA Technical Reports Server (NTRS)

    Hoover, R.; Hoyle, F.; Wallis, M. K.; Wickramasinghe, N. C.

    1986-01-01

    The fossil record of the microscopic algae classified as diatoms suggests they were injected to earth at the Cretaceous boundary. Not only could diatoms remain viable in the cometary environment, but also many species might replicate in illuminated surface layers or early interior layers of cometary ice. Presumably they reached the solar system on an interstellar comet as an already-evolved assemblage of organisms. Diatoms might cause color changes to comet nuclei while their outgassing decays and revives around highly elliptical orbits. Just as for interstellar absorption, high-resolution IR observations are capable of distinguishing whether the 10-micron feature arises from siliceous diatom material or mineral silicates. The 10-30-micron band and the UV 220-nm region can also provide evidence of biological material.

  12. Nuclear Lamins and Neurobiology

    PubMed Central

    Jung, Hea-Jin; Lee, John M.

    2014-01-01

    Much of the work on nuclear lamins during the past 15 years has focused on mutations in LMNA (the gene for prelamin A and lamin C) that cause particular muscular dystrophy, cardiomyopathy, partial lipodystrophy, and progeroid syndromes. These disorders, often called laminopathies, mainly affect mesenchymal tissues (e.g., striated muscle, bone, and fibrous tissue). Recently, however, a series of papers have identified important roles for nuclear lamins in the central nervous system. Studies of knockout mice uncovered a key role for B-type lamins (lamins B1 and B2) in neuronal migration in the developing brain. Also, duplications of LMNB1 (the gene for lamin B1) have been shown to cause autosome-dominant leukodystrophy. Finally, recent studies have uncovered a peculiar pattern of nuclear lamin expression in the brain. Lamin C transcripts are present at high levels in the brain, but prelamin A expression levels are very lowdue to regulation of prelamin A transcripts by microRNA 9. This form of prelamin A regulation likely explains why prelamin A diseases such as Hutchinson-Gilford progeria syndrome spare the central nervous system. In this review, we summarize recent progress in elucidating links between nuclear lamins and neurobiology. PMID:24842906

  13. Plasmids in diatom species.

    PubMed Central

    Hildebrand, M; Corey, D K; Ludwig, J R; Kukel, A; Feng, T Y; Volcani, B E

    1991-01-01

    We have discovered plasmids in 5 of 18 diatom species surveyed. In several species, more than one type of plasmid is present. Several of the plasmids show similarity by hybridization previously characterized plasmids in Cylindrotheca fusiformis (J. D. Jacobs et al., unpublished data). Additionally, there is similarity between the plasmids found in C. fusiformis and chloroplast DNA in three diatom species. These results add to the evidence that the plasmids have features of mobile genetic elements. Images PMID:1885558

  14. Carotenoid biosynthesis in diatoms.

    PubMed

    Bertrand, Martine

    2010-11-01

    Diatoms are ubiquitous and constitute an important group of the phytoplankton community having a major contribution to the total marine primary production. These microalgae exhibit a characteristic golden-brown colour due to a high amount of the xanthophyll fucoxanthin that plays a major role in the light-harvesting complex of photosystems. In the water column, diatoms are exposed to light intensities that vary quickly from lower to higher values. Xanthophyll cycles prevent photodestruction of the cells in excessive light intensities. In diatoms, the diadinoxanthin-diatoxanthin cycle is the most important short-term photoprotective mechanism. If the biosynthetic pathways of chloroplast pigments have been extensively studied in higher plants and green algae, the research on carotenoid biosynthesis in diatoms is still in its infancy. In this study, the data on the biosynthetic pathway of diatom carotenoids are reviewed. The early steps occur through the 2-C-methyl-D: -erythritol 4-phosphate (MEP) pathway. Then a hypothetical pathway is suggested from dimethylallyl diphosphate (DMAPP) and isopentenyl pyrophosphate (IPP). Most of the enzymes of the pathway have not been so far isolated from diatoms, but candidate genes for each of them were identified using protein similarity searches of genomic data. PMID:20734232

  15. Honeycomb-laminate composite structure

    NASA Technical Reports Server (NTRS)

    Gilwee, W. J., Jr.; Parker, J. A. (Inventor)

    1977-01-01

    A honeycomb-laminate composite structure was comprised of: (1) a cellular core of a polyquinoxaline foam in a honeycomb structure, and (2) a layer of a noncombustible fibrous material impregnated with a polyimide resin laminated on the cellular core. A process for producing the honeycomb-laminate composite structure and articles containing the honeycomb-laminate composite structure is described.

  16. Environmental investigations using diatom microfossils

    USGS Publications Warehouse

    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.

  17. Fossil diatoms and neogene paleolimnology

    USGS Publications Warehouse

    Platt, Bradbury J.

    1988-01-01

    Diatoms have played an important role in the development of Neogene continental biostratigraphy and paleolimnology since the mid-19th Century. The history of progress in Quaternary diatom biostratigraphy has developed as a result of improved coring techniques that enable sampling sediments beneath existing lakes coupled with improved chronological control (including radiometric dating and varve enumeration), improved statistical treatment of fossil diatom assemblages (from qualitative description to influx calculations of diatom numbers or volumes), and improved ecological information about analogous living diatom associations. The last factor, diatom ecology, is the most critical in many ways, but progresses slowly. Fortunately, statistical comparison of modern diatom assemblages and insightful studies of the nutrient requirements of some common freshwater species are enabling diatom paleolimnologists to make more detailed interpretations of the Quaternary record than had been possible earlier, and progress in the field of diatom biology and ecology will continue to refine paleolimnological studies. The greater age and geologic setting of Tertiary diatomaceous deposits has prompted their study in the contexts of geologic history, biochronology and evolution. The distribution of diatoms of marine affinities in continental deposits has given geologists insights about tectonism and sea-level change, and the distribution of distinctive (extinct?) diatoms has found utilization both in making stratigraphic correlations between outcrops of diatomaceous deposits and in various types of biochronological studies that involve dating deposits in different areas. A continental diatom biochronologic scheme will rely upon evolution, such as the appearance of new genera within a family, in combination with regional environmental changes that are responsible for the wide distribution of distinctive diatom species. The increased use of the scanning electron microscope for the detailed descriptions of fossil diatoms will provide the basis for making more accurate correlations and identifications, and the micromorphological detail for speculations about evolutionary relationships. ?? 1988.

  18. Biomarker evidence of Holocene climate and cryosphere variability: results from a 171m, annually laminated, sediment core from the Adélie coast, Antarctica (IODP Expedition 318)

    NASA Astrophysics Data System (ADS)

    Bendle, J. A.; Seki, O.; Kawamura, K.; Willmott, V.; Schouten, S.; Sangiorgi, F.; McKay, R.; Riesselman, C. R.; Dunbar, R. B.

    2012-12-01

    The Southern Ocean remains the least studied region on Earth with respect to Holocene climate variability. The few Antarctic proximal marine sedimentary records available tend to be short, low resolution, and discontinuous. However, sediments recently recovered from the Adélie drift during IODP Expedition 318 present a new opportunity to study East Antarctic Holocene climatic evolution, at a resolution that facilitates direct comparison with ice-cores. Expedition 318 recovered 171m of Holocene laminated diatom ooze from site U1357B. The sediments represent continuous Holocene accumulation up to the present day (based on 89 AMS 14C dates) and are characterised by 2-6cm thick, light/dark laminae couplets, interpreted as seasonal biogenic production and accumulation events. We present the results of initial biomarker analyses: fatty acid δD and TEX86 measurements on lipid extracts from paired light/dark laminae throughout the Holocene. The C18 fatty acid is assumed to represent an integrated signal from the algal precursors and thus surface water conditions. The δDC18-FA values show no consistent offset between the light and dark laminae, and values become isotopically heavier on average through the Holocene (ca. -220 to 140‰), in line with declining insolation at 65°S. Superimposed on this trend are millennial scale isotopic excursions of ca. 20 to 60‰, including a clear excursion coeval with an increase in grain size in U1356B and the late Holocene climate 'optimum' between 6 and 3 kyr, inferred from East Antarctic ice-cores. δDC18-FA shows no clear relationship with TEXL86 sea-surface temperature estimates, which display pronounced early variability and relative warmth from 11.2 to 10.4 ka (0 to 6.5 °C, average ca. 3.5 °C), but almost no change after 10.4 ka, as cold, stable SSTs (average ca. 2 °C) persist through the rest of the Holocene. We explore the potential controls on the δDC18-FA record and suggest the influence of isotopically depleted meltwater from the proximal ice-sheet (additive to a salinity effect) and/or upwelling could account for the millennial scale variability. The next steps are to ground-truth the proxies in this unique archive and to exploit the paleoclimatic information encoded in the abundant algal sterol compounds, the higher plant waxes and to apply compound-specific δ13C as well as additional δD measurements.

  19. Lamination cooling system formation method

    DOEpatents

    Rippel, Wally E [Altadena, CA; Kobayashi, Daryl M [Monrovia, CA

    2009-05-12

    An electric motor, transformer or inductor having a cooling system. A stack of laminations have apertures at least partially coincident with apertures of adjacent laminations. The apertures define straight or angled cooling-fluid passageways through the lamination stack. Gaps between the adjacent laminations are sealed by injecting a heat-cured sealant into the passageways, expelling excess sealant, and heat-curing the lamination stack. Manifold members adjoin opposite ends of the lamination stack, and each is configured with one or more cavities to act as a manifold to adjacent passageway ends. Complex manifold arrangements can create bidirectional flow in a variety of patterns.

  20. Lamination cooling system formation method

    DOEpatents

    Rippel, Wally E. (Altadena, CA); Kobayashi, Daryl M. (Monrovia, CA)

    2012-06-19

    An electric motor, transformer or inductor having a cooling system. A stack of laminations have apertures at least partially coincident with apertures of adjacent laminations. The apertures define straight or angled cooling-fluid passageways through the lamination stack. Gaps between the adjacent laminations are sealed by injecting a heat-cured sealant into the passageways, expelling excess sealant, and heat-curing the lamination stack. Manifold members adjoin opposite ends of the lamination stack, and each is configured with one or more cavities to act as a manifold to adjacent passageway ends. Complex manifold arrangements can create bidirectional flow in a variety of patterns.

  1. Photosynthetic Pigments in Diatoms

    PubMed Central

    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-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. PMID:26389924

  2. Photosynthetic Pigments in Diatoms.

    PubMed

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

    2015-09-01

    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-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. PMID:26389924

  3. Resin hybrid composite laminates

    SciTech Connect

    Bhatnagar, A.

    1986-01-01

    Hybrid composites are generally referred to as the materials that combine two or more fibers in a suitable binding resin. Resin hybrid composites described in this paper utilize two or more resins with a suitable reinforcement. The resins are rigid resin and flexible resins. The elongation of the rigid resin is less than 2% and elongation of the flexible resins are varied between 25% to 100% by blending a very flexible resin with the rigid resin. Test laminates are fabricated by using either glass, carbon or aramid reinforcement in a layered sequence. This produces rigid-flexible-rigid and flexible-rigid-flexible laminates. These laminates are tested for impact, compression, flexural and inter-laminar strengths. Results show that the resin hybriding provides a wide choice of mechanical properties to the composite industry.

  4. Laminates and reinforced metals

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1980-01-01

    A selective review is presented of the state of the art of metallic laminates and fiber reinforced metals called metallic matrix laminates (MMLs). Design and analysis procedures that are used for, and typical structural components that have been made from MMLs are emphasized. Selected MMLs, constituent materials, typical material properties and fabrication procedures are briefly described, including hybrids and superhybrids. Advantages, disadvantages, and special considerations required during design, analysis, and fabrication of MMLs are examined. Tabular and graphical data are included to illustrate key aspects of MMLs. Appropriate references are cited to provide a selective bibliography of a rapidly expanding and very promising research and development field.

  5. Laminate armor and related methods

    SciTech Connect

    Chu, Henry S; Lillo, Thomas M; Zagula, Thomas M

    2013-02-26

    Laminate armor and methods of manufacturing laminate armor. Specifically, laminate armor plates comprising a commercially pure titanium layer and a titanium alloy layer bonded to the commercially pure titanium outer layer are disclosed, wherein an average thickness of the titanium alloy inner layer is about four times an average thickness of the commercially pure titanium outer layer. In use, the titanium alloy layer is positioned facing an area to be protected. Additionally, roll-bonding methods for manufacturing laminate armor plates are disclosed.

  6. Transparent polymeric laminates

    NASA Technical Reports Server (NTRS)

    Parker, J. A.; Fohlen, G. M.; Sawko, P. M.

    1973-01-01

    Laminate prepared from epoxy-boroxine and phenolphthalein polycarbonate has high mechanical strength at elevated temperature and is resistant to impact, fire, and high-energy thermal radiation. Polycarbonate is prepared by reaction of phenolphthalein with phosgene in presence of amine catalyst and immiscible organic solvent phase.

  7. Loosely-Bound Diatomic Molecules.

    ERIC Educational Resources Information Center

    Balfour, W. J.

    1979-01-01

    Discusses concept of covalent bonding as related to homonuclear diatomic molecules. Article draws attention to the existence of bound rare gas and alkaline earth diatomic molecules. Summarizes their molecular parameters and offers spectroscopic data. Strength and variation with distance of interatomic attractive forces is given. (Author/SA)

  8. Interactions between diatoms and bacteria.

    PubMed

    Amin, Shady A; Parker, Micaela S; Armbrust, E Virginia

    2012-09-01

    Diatoms and bacteria have cooccurred in common habitats for hundreds of millions of years, thus fostering specific associations and interactions with global biogeochemical consequences. Diatoms are responsible for one-fifth of the photosynthesis on Earth, while bacteria remineralize a large portion of this fixed carbon in the oceans. Through their coexistence, diatoms and bacteria cycle nutrients between oxidized and reduced states, impacting bioavailability and ultimately feeding higher trophic levels. Here we present an overview of how diatoms and bacteria interact and the implications of these interactions. We emphasize that heterotrophic bacteria in the oceans that are consistently associated with diatoms are confined to two phyla. These consistent bacterial associations result from encounter mechanisms that occur within a microscale environment surrounding a diatom cell. We review signaling mechanisms that occur in this microenvironment to pave the way for specific interactions. Finally, we discuss known interactions between diatoms and bacteria and exciting new directions and research opportunities in this field. Throughout the review, we emphasize new technological advances that will help in the discovery of new interactions. Deciphering the languages of diatoms and bacteria and how they interact will inform our understanding of the role these organisms have in shaping the ocean and how these interactions may change in future oceans. PMID:22933565

  9. Diatom DNA as historical information

    NASA Astrophysics Data System (ADS)

    Stoof, K. R.; Epp, L. S.; Trauth, M. H.; Tiedemann, R.

    2009-04-01

    This survey is about the reconstruction of paleo environmental conditions in East Africa using recent and historic lakes sediments of shallow lakes in Kenya. This interdisciplinary approach combines the molecular analysis of ancient diatom DNA and the morphological analysis of diatom assemblages of short sediment cores to reveal the potential of molecular genetics in geosciences. This study comprises the investigation of two short sediment cores from Lake Naivasha (Kenya) taken in 2007, covering a stretch of ca. 80 years. Several sediment slices were analysed by molecular methods that concludes in species identification based on DNA fragments. Therefore total DNA was extracted and applied to a diatom DNA specific PCR amplifying a gene fragment that is frequently used for species identification. After cloning PCR products, clones were sequenced, sequences from different diatom species were analysed. As a comparison permanent slides were prepared for each sediment sample for counting diatom valves. The results suggest that DNA damage, perhaps species depended, and specific factors of PCR contribute to an overhang of two dominant diatom species (Aulacoseira ambigua and Aulacoseira granulata) represented by the molecular approach whereas rare species seen by light microscopy are not yet identifiable with molecular methods. Moreover changes in diatom assemblages and the reconstructed conductivity indicate a decrease of lake level around 1940. This shift seems to be also represented in the molecular approach as a decrease in the amount of diverse diatom DNA sequences found, what is probably caused by worse DNA preservation conditions at that time.

  10. Planktonic diatoms of Lake Ontario

    USGS Publications Warehouse

    Reinwand, Jerry F.

    1969-01-01

    The major species of diatoms in surface collections from Lake Ontario in September 1964 were Asterionella formosa, Fragilaria crotonensis, and Tabellaris fenestrata. Dominant species in the deep-water samples were Stephanodiscus astraea, S. astraea var. mintula, and F. crotonensis. The diatom flora in surface collections varied among several stations in the eastern end of the lake.

  11. Interactions between Diatoms and Bacteria

    PubMed Central

    Amin, Shady A.; Parker, Micaela S.

    2012-01-01

    Summary: Diatoms and bacteria have cooccurred in common habitats for hundreds of millions of years, thus fostering specific associations and interactions with global biogeochemical consequences. Diatoms are responsible for one-fifth of the photosynthesis on Earth, while bacteria remineralize a large portion of this fixed carbon in the oceans. Through their coexistence, diatoms and bacteria cycle nutrients between oxidized and reduced states, impacting bioavailability and ultimately feeding higher trophic levels. Here we present an overview of how diatoms and bacteria interact and the implications of these interactions. We emphasize that heterotrophic bacteria in the oceans that are consistently associated with diatoms are confined to two phyla. These consistent bacterial associations result from encounter mechanisms that occur within a microscale environment surrounding a diatom cell. We review signaling mechanisms that occur in this microenvironment to pave the way for specific interactions. Finally, we discuss known interactions between diatoms and bacteria and exciting new directions and research opportunities in this field. Throughout the review, we emphasize new technological advances that will help in the discovery of new interactions. Deciphering the languages of diatoms and bacteria and how they interact will inform our understanding of the role these organisms have in shaping the ocean and how these interactions may change in future oceans. PMID:22933565

  12. Diatomic predissociation line widths

    NASA Technical Reports Server (NTRS)

    Child, M. S.

    1973-01-01

    Predissociation by rotation and curve crossing in diatomic molecules is discussed. The pattern of predissociation line widths is seen as providing a highly sensitive yardstick for the determination of unknown potential curves. In addition, the computation of such a pattern for given potential curves is considered a matter of routine, unless the predissociation happens to occur from an adiabatic potential curve. Analytic formulas are used to provide physical insight into the details of the predissociation pattern, to the extent that a direct inversion procedure is developed for determination of the repulsive potential curves for Type 1 predissociations.

  13. Diatomic gasdynamic lasers.

    NASA Technical Reports Server (NTRS)

    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.

  14. Diatomic gasdynamic lasers

    NASA Technical Reports Server (NTRS)

    Mckenzie, R. L.

    1971-01-01

    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.

  15. The Diatom EST Database

    PubMed Central

    Maheswari, Uma; Montsant, Anton; Goll, Johannes; Krishnasamy, S.; Rajyashri, K. R.; Patell, Villoo Morawala; Bowler, Chris

    2005-01-01

    The Diatom EST database provides integrated access to expressed sequence tag (EST) data from two eukaryotic microalgae of the class Bacillariophyceae, Phaeodactylum tricornutum and Thalassiosira pseudonana. The database currently contains sequences of close to 30?000 ESTs organized into PtDB, the P.tricornutum EST database, and TpDB, the T.pseudonana EST database. The EST sequences were clustered and assembled into a non-redundant set for each organism, and these non-redundant sequences were then subjected to automated annotation using similarity searches against protein and domain databases. EST sequences, clusters of contiguous sequences, their annotation and analysis with reference to the publicly available databases, and a codon usage table derived from a subset of sequences from PtDB and TpDB can all be accessed in the Diatom EST Database. The underlying RDBMS enables queries over the raw and annotated EST data and retrieval of information through a user-friendly web interface, with options to perform keyword and BLAST searches. The EST data can also be retrieved based on Pfam domains, Cluster of Orthologous Groups (COG) and Gene Ontologies (GO) assigned to them by similarity searches. The Database is available at http://avesthagen.sznbowler.com. PMID:15608213

  16. Laminated piezoelectric transformer

    NASA Technical Reports Server (NTRS)

    Vazquez Carazo, Alfredo (Inventor)

    2006-01-01

    A laminated piezoelectric transformer is provided using the longitudinal vibration modes for step-up voltage conversion applications. The input portions are polarized to deform in a longitudinal plane and are bonded to an output portion. The deformation of the input portions is mechanically coupled to the output portion, which deforms in the same longitudinal direction relative to the input portion. The output portion is polarized in the thickness direction relative its electrodes, and piezoelectrically generates a stepped-up output voltage.

  17. Thermally stable laminating resins

    NASA Technical Reports Server (NTRS)

    Jones, R. J.; Vaughan, R. W.; Burns, E. A.

    1972-01-01

    Improved thermally stable laminating resins were developed based on the addition-type pyrolytic polymerization. Detailed monomer and polymer synthesis and characterization studies identified formulations which facilitate press molding processing and autoclave fabrication of glass and graphite fiber reinforced composites. A specific resin formulation, termed P10P was utilized to prepare a Courtaulds HMS reinforced simulated airfoil demonstration part by an autoclave molding process.

  18. Do biosiliceous laminated sediments reveal sea ice seasonality in the middle Eocene Arctic Ocean?

    NASA Astrophysics Data System (ADS)

    Stickley, C. E.; Koc, N.; Pearce, R. B.; Kemp, A. E. S.

    2009-04-01

    We present initial microfabric analyses of finely laminated middle Eocene biosiliceous sediments from the IODP Expedition 302 "ACEX" cores (central Arctic, Lomonosov Ridge). Backscattered electron imagery (BSEI) of polished thin sections and scanning electron microscope secondary electron imagery (SEI) of lamina-parallel fracture surfaces are used to analyse the laminations in 2 short intervals dated at approximately 46 Ma. Our data offer insight into the cryospheric history of the central Arctic from a siliceous microfossil perspective during a significant phase in Cenozoic climate evolution—the start of the transition from a greenhouse to an icehouse world. Importantly, the BSEI technique offers the detail of information which can not be achieved by bulk sediment analysis. These organic-rich sediments, deposited under an anoxic benthic environment, are also rich in heavily silicified endemic marine to brackish (diatoms, ebridians, silicoflagellates) and in situ freshwater (chrysophyte cysts) siliceous microfossils. They also contain the weakly silicified needle-like diatom Synedropsis spp., an indicator of sea ice and the world's oldest known fossil record of sea ice dwelling diatoms (Stickley et al., in press; Stickley and Koc, Session CL33 this conference). Their presence highlights an exceptional preservational environment along the Lomonosov Ridge at this time. Synedropsis spp. show the Arctic Ocean supported sea ice-based life from 47 Ma, yet episodes of melting must have occurred to allow their preservation in the sediments. Initial investigations indicate Synedropsis spp. form mono-specific laminations or elongate lenses of, on average, 25

  19. Solar cell module lamination process

    DOEpatents

    Carey, Paul G. (Mountain View, CA); Thompson, Jesse B. (Brentwood, CA); Aceves, Randy C. (Tracy, CA)

    2002-01-01

    A solar cell module lamination process using fluoropolymers to provide protection from adverse environmental conditions and thus enable more extended use of solar cells, particularly in space applications. A laminate of fluoropolymer material provides a hermetically sealed solar cell module structure that is flexible and very durable. The laminate is virtually chemically inert, highly transmissive in the visible spectrum, dimensionally stable at temperatures up to about 200.degree. C. highly abrasion resistant, and exhibits very little ultra-violet degradation.

  20. Stuart R. Stidolph diatom atlas

    USGS Publications Warehouse

    Stidolph, S.R.; Sterrenburg, F.A.S.; Smith, K.E.L.; Kraberg, A.

    2012-01-01

    The "Stuart R. Stidolph Diatom Atlas" is a comprehensive volume of diatom taxa identified and micrographed by Stuart R. Stidoph during the 1980s and 1990s. The samples were collected from marine coasts of various geographic regions within tropical and subtropical climates. The plates included within this report have never been published and are being published by the USGS as an online reference so that others may have access to this incredible collection.

  1. Diatoms inhabiting a wind flat of the Baltic Sea: Species diversity and seasonal succession

    NASA Astrophysics Data System (ADS)

    Woelfel, Jana; Schumann, Rhena; Adler, Sven; Hbener, Thomas; Karsten, Ulf

    2007-11-01

    The seasonal succession of brackish microphytobenthos (consisting of diatoms and cyanobacteria) was studied at a wind flat at the southern Baltic Sea coast. Wind flats are coastal zones with a high degree of exposition becoming flooded irregularly as a function of sea levels, prevailing wind direction and speed. These extreme environmental conditions favour the formation of laminated microbial mats similar to those in tidal flats. Special attention was paid to the comparison of diatom compositions in a laminated microbial mat as a relatively steady biocoenosis, and compositions in sediment without a mat, probably a more disturbed area. Therefore, monthly sediment samples from March to November 2002 were examined at two adjacent stations (reference station without mat, microbial mat station). Biomass (chlorophyll a content), cyanobacterial and diatom abundance, species composition and diversity were determined. The main mat forming cyanobacteria were Microcoleus chthonoplastes and Lyngbya aestuarii. The laminated mat exhibited a larger total biomass from spring on, while diatoms at the reference station accumulated relatively more biomass until late summer. 93 diatom taxa were identified in total. The species compositions at both stations were similar compared to those inhabiting other sandy and shallow water areas of the Baltic Sea. However, in the mat inhabiting diatom community lower relative abundances of very small species (<15 ?m) were determined. In contrast to tidal flats, diatoms of the wind flat were found in much deeper zones of the mat (down to 1 cm), which may contribute to less anoxic conditions. This occurrence may be influenced by the specific sediment features, such as larger sand grain sizes. Species numbers were moderate within a given sample, indicating that environmental conditions in wind flats are extreme and outside of the tolerance limits of many species. On the other hand, the Shannon-Weaver index was comparably high due to its evenness component, so that disturbances may have been too frequent to establish climax communities, i.e. supporting few strongly dominant species. Nevertheless, the total biomass accumulated in the range of many other microphytobenthos communities in spite of extreme conditions hinting on good adaptation and protection capabilities, e.g. mucous material with high water retention potential.

  2. Beach lamination: Nature and origin

    USGS Publications Warehouse

    Clifton, H.E.

    1969-01-01

    A distinctive two-fold sedimentation unit characterizes lamination in the upper swash zone of beaches. Within the unit a fine and/or a heavy mineral rich layer at the base grades upward into a coarser and/or a heavy mineral poor layer at the top. This distinctive type of lamination results from grain segregation within bed flow during wave backwash. ?? 1969.

  3. Holographic nondestructive testing of laminates

    NASA Technical Reports Server (NTRS)

    Stuckenberg, F. H.

    1973-01-01

    Very small differences in laminate thickness result in interference fringes in holograph image. These indicate presence of unbonded area. Theoretical knowledge of membrane deflection may be used in conjunction with reduced number of pretest experiments to determine number of optical fringes that should appear for given laminate.

  4. Laminated, composite flywheel failure analysis

    NASA Astrophysics Data System (ADS)

    Nimmer, R. P.

    1980-06-01

    A hybrid, composite flywheel, composed of a laminated, flat S2 glass central disc, with a filament wound, graphite outer ring has been proposed for vehicle application. The failure mechanism of the laminated central disco of this hybrid design is discussed with reference to spin test data, nondestructive ultrasound test data, and supporting failure analysis.

  5. Mechanism to explore lamination rate.

    PubMed

    Rossi, Lionel

    2010-02-01

    A mechanism amenable to laminate and fold flows is identified and quantified. This laminating mechanism follows from a physical and experimental approach relying on the interlaced structure of velocity and Lagrangian acceleration. The Lagrangian acceleration being the resultant of the forces applied on particle fluids, the component of acceleration perpendicular to the velocity vector allows the quantification of a rate of change of the velocity's direction, i.e., the local angular Lagrangian velocity, theta. The spatial variation in theta is then used to predict and measure the lamination and folding rate. To support and illustrate this approach, three basic experimental flows, driven by electromagnetic forces, are discussed and compared. Folding rate intensities are extracted for different characteristic length scales. Also, good agreement is found between grid deformation and the prediction of lamination rate. This quantification of lamination rate opens new avenues for the design of mixers, in particular at low Reynolds numbers. PMID:20365680

  6. Dissociation of diatomic gases

    NASA Technical Reports Server (NTRS)

    Hansen, C. F.

    1991-01-01

    The Landau-Zener theory of reactive cross sections has been applied to diatomic molecules dissociating from a ladder of rotational and vibrational states. Although the preexponential factor of the Arrhenius rate expression is shown to be a complex function of the dimensionless activation energy, the average over all states in the ladder is well represented by a single factor that varies about as T exp (-n), where the coefficient n is the order of unity. This relation agrees very well with experimental data for dissociation of O2 and N2, for example. The results validate previous empirical assignment of a single preexponential factor in the Arrhenius expression and justify the extrapolation of the expression well beyond the range of data. The theory is then used to calculate the effect of vibrational nonequilibrium on dissociation rate. For Morse oscillators the results are about the same as for harmonic oscillators, and the dissociation from a ladder of equilibrium rotational and nonequilibrium vibrational states is close to an analytic approximation provided by Hammerling, Kivel, and Teare for harmonic oscillators all dissociating from the ground rotational state.

  7. Dinoflagellates, diatoms, and their viruses.

    PubMed

    Nagasaki, Keizo

    2008-06-01

    Since the first discovery of the very high virus abundance in marine environments, a number of researchers were fascinated with the world of "marine viruses", which had previously been mostly overlooked in studies on marine ecosystems. In the present paper, the possible role of viruses infecting marine eukaryotic microalgae is enlightened, especially summarizing the most up-to-the-minute information of marine viruses infecting bloom-forming dinoflagellates and diatoms. To author's knowledge, approximately 40 viruses infecting marine eukaryotic algae have been isolated and characterized to different extents. Among them, a double-stranded DNA (dsDNA) virus "HcV" and a single-stranded RNA (ssRNA) virus "HcRNAV" are the only dinoflagellate-infecting (lytic) viruses that were made into culture; their hosts are a bivalve-killing dinoflagellate Heterocapsa circularisquama. In this article, ecological relationship between H. circularisquama and its viruses is focused. On the other hand, several diatom-infecting viruses were recently isolated and partially characterized; among them, one is infectious to a pen-shaped bloom-forming diatom species Rhizosolenia setigera; some viruses are infectious to genus Chaetoceros which is one of the most abundant and diverse diatom group. Although the ecological relationships between diatoms and their viruses have not been sufficiently elucidated, viral infection is considered to be one of the significant factors affecting dynamics of diatoms in nature. Besides, both the dinoflagellate-infecting viruses and diatom-infecting viruses are so unique from the viewpoint of virus taxonomy; they are remarkably different from any other viruses ever reported. Studies on these viruses lead to an idea that ocean may be a treasury of novel viruses equipped with fascinating functions and ecological roles. PMID:18604491

  8. Diatom genomics: genetic acquisitions and mergers.

    PubMed

    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. PMID:15620637

  9. High Resolution Diatom Biostratigraphy for the Past 400 Years From West Pisco Basin, Peru

    NASA Astrophysics Data System (ADS)

    Tapia, P.; Gutierrez, D.; Velazco, F.; Salvatteci, R.; Ortlieb, L.; Soler, P.; Sifeddine, A.; Baumgartner, T.; Ferreira, V.; Field, D.; Solis, J.

    2005-12-01

    A high-resolution record from box-core B0405-6-IV retrieved off Pisco, south-central Peru, at 300-m water depth shows important diatom species changes during its the time of deposition. An age model based on excess 210Pb activities, bomb-derived 241Am signals, and sediment structures derived from historically well-known seismic events, suggests about 400-yr of sedimentary record. The 73-cm core contains massive and fine to coarse laminated mud; samples for siliceous microfossils analysis were taken continuously every 3 to 8 mm following the main sedimentary structure. Mean sedimentation rate is 2.2 mm x yr-1 in the upper section of the core, which indicate that each sample interval may represent from 1.3 to 3.6 yr. Four diatom assemblages are present throughout the core. Sediments contain Chaetoceros resting spores throughout the whole sequence indicating that the site lies over an active coastal upwelling system. The Chaetoceros group dominates the lower half of the core sediment and define the first diatom assemblage. This assemblage is present in the bottom half of the core from about 73 cm (1600 AD) to 33 cm and contains Actinopthychus senarius, Cocconeis sp., Fragilariopsis doliolus and Thalassiosira eccentrica as subordinated species. Diatom concentrations in the lower half of the core are lower than in the upper part. A second assemblage is found from about 33 cm (1840 AD) to 26 cm, and is dominated by the centric diatom Skeletonema costatum, with Pseudo-nitzschia pungens, Pseudo-nitzschia australis and Prosbocia alata as subdominant species. The third assemblage extends from about 26 cm (1870 AD) to 10 cm and contains abundant Thalassionema bacillare and lower amounts of Coscinodiscus argus. Finally, the last diatom assemblage represent the past 50 years with an important increment of Thalassionema nitzschiodes coupled by the presence of Actinocyclus octonarius as subordinate species. Rare occurrences of freshwater diatoms are found downcore from 25 cm to the bottom, which suggests that the site were reached by particles out of severalpulses of riverine water from the Andes. Decadal to centennial-scale changes on diatom composition from the past 165 years (since 1840 AD) is quite remarkable because a) the diatom species are mostly indicative of modern Cold Coastal Waters, and b) the changes coincide with higher concentrations of diatom valves. This increase of primary productivity on the Peruvian upwelling system is the highest from the last 400-yr record.

  10. Overview of current laminitis research.

    PubMed

    Eades, Susan C

    2010-04-01

    All cases of laminitis are characterized by failure of the attachment of the epidermal cells of the epidermal laminae to the underlying basement membrane of the dermal laminae despite the diversity of diseases that underlie the syndrome. The preponderance of evidence supports roles for inflammation, metabolic derangement, endothelial and venous dysfunction, and matrix degradation as causes of laminitis. Inflammation, oxidant stress, and matrix degradation may be factors common to each of these mechanisms that lead to the laminar damage of laminitis. The understanding of the pathophysiology and progression of the disease is incomplete, and this limits efforts to prevent and treat this devastating disease successfully. However, scientific investigations are occurring at a phenomenal rate and shedding light on the pathophysiologic events involved with laminitis. PMID:20381735

  11. Hierarchic models for laminated plates

    NASA Technical Reports Server (NTRS)

    Szabo, Barna A.; Actis, Ricardo L.

    1991-01-01

    The research conducted in the formulation of hierarchic models for laminated plates is described. The work is an extension of the work done for laminated strips. The use of a single parameter, beta, is investigated that represents the degree to which the equilibrium equations of three dimensional elasticity are satisfied. The powers of beta identify members in the hierarchic sequence. Numerical examples that were analyzed with the proposed sequence of models are included. The results obtained for square plates with uniform loading and homogeneous boundary conditions are very encouraging. Several cross-ply and angle-ply laminates were evaluated and the results compared with those of the fully three dimensional model, computed using MSC/PROBE, and with previously reported work on laminated strips.

  12. Sudden bending of cracked laminates

    NASA Technical Reports Server (NTRS)

    Sih, G. C.; Chen, E. P.

    1980-01-01

    A dynamic approximate laminated plate theory is developed with emphasis placed on obtaining effective solution for the crack configuration where the 1/square root of r stress singularity and the condition of plane strain are preserved. The radial distance r is measured from the crack edge. The results obtained show that the crack moment intensity tends to decrease as the crack length to laminate plate thickness is increased. Hence, a laminated plate has the desirable feature of stabilizing a through crack as it increases its length at constant load. Also, the level of the average load intensity transmitted to a through crack can be reduced by making the inner layers to be stiffer than the outer layers. The present theory, although approximate, is useful for analyzing laminate failure to crack propagation under dynamic load conditions.

  13. Internal Stresses in Laminated Construction

    NASA Technical Reports Server (NTRS)

    Heim, A L; Knauss, A C; Seutter, Louis

    1923-01-01

    This report reviews the procedure employed in an investigation of the sources and influence of internal stresses in laminated construction, and discusses the influence of shrinkage and swelling stresses caused by atmospheric conditions upon the tensile strength across grain in laminated construction with special reference to airplane propellers. The investigation covered three sources of internal stress, namely, the combination of plain-sawed and quarter-sawed material in the same construction, the gluing together of laminations of different moisture contents, and the gluing together of laminations of different densities. Glued specimens and free specimens, made up under various manufacturing conditions, were subjected to various climatic changes inducing internal stresses and then were tested.

  14. Vacuum lamination of photovoltaic modules

    NASA Technical Reports Server (NTRS)

    Burger, D. R.

    1982-01-01

    Vacuum lamination of terrestrial photovoltaic modules is a new high volume process requiring new equipment and newly develop materials. Equipment development, materials research, and some research in related fields and testing methods are discussed.

  15. Laminated electromagnetic pump stator core

    DOEpatents

    Fanning, A.W.

    1995-08-08

    A stator core for an electromagnetic pump includes a plurality of circumferentially abutting tapered laminations extending radially outwardly from a centerline axis to collectively define a radially inner bore and a radially outer circumference. Each of the laminations includes radially inner and outer edges and has a thickness increasing from the inner edge toward the outer edge to provide a substantially continuous path adjacent the circumference. This pump is used in nuclear fission reactors. 19 figs.

  16. Laminated electromagnetic pump stator core

    DOEpatents

    Fanning, Alan W. (San Jose, CA)

    1995-01-01

    A stator core for an electromagnetic pump includes a plurality of circumferentially abutting tapered laminations extending radially outwardly from a centerline axis to collectively define a radially inner bore and a radially outer circumference. Each of the laminations includes radially inner and outer edges and has a thickness increasing from the inner edge toward the outer edge to provide a substantially continuous path adjacent the circumference.

  17. Diatom 'Didymosphenia geminata' Cell Wall

    USGS Multimedia Gallery

    Image of the silica cell wall of the diatom 'Didymosphenia geminata' from Rio Espolon, Chile. The sample was collected early in 2010 from an extensive bloom on the river. The image has been processed to show the silica cell wall, removing the organic cell contents and the stalk material....

  18. Automated measurement of diatom size

    USGS Publications Warehouse

    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.

  19. Luminescence properties of a nanoporous freshwater diatom.

    PubMed

    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 ?-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. PMID:21618682

  20. Proteomics studies on stress responses in diatoms.

    PubMed

    Muhseen, Ziyad Tariq; Xiong, Qian; Chen, Zhuo; Ge, Feng

    2015-12-01

    Diatoms are a highly diverse group of eukaryotic phytoplankton that are distributed throughout marine and freshwater environments and are believed to be responsible for approximately 40% of the total marine primary productivity. The ecological success of diatoms suggests that they have developed a range of strategies to cope with various biotic and abiotic stress factors. It is of great interest to understand the adaptive responses of diatoms to different stresses in the marine environment. Proteomic technologies have been applied to the adaptive responses of marine diatoms under different growth conditions in recent years such as nitrogen starvation, iron limitation and phosphorus deficiency. These studies have provided clues to elucidate the sophisticated sensing mechanisms that control their adaptive responses. Although only a very limited number of proteomic studies were conducted in diatoms, the obtained data have led to a better understanding of the biochemical processes that contribute to their ecological success. This review presents the current status of proteomic studies of diatom stress responses and discusses the novel developments and applications for the analysis of protein post-translational modification in diatoms. The potential future application of proteomics could contribute to a better understanding of the physiological mechanisms underlying diatom acclimation to a given stress and the acquisition of an enhanced diatom stress tolerance. Future challenges and research opportunities in the proteomics studies of diatoms are also discussed. PMID:26364674

  1. High diatom production and export in stratified waters - A potential negative feedback to global warming

    NASA Astrophysics Data System (ADS)

    Kemp, Alan E. S.; Villareal, Tracy A.

    2013-12-01

    It is widely held that increased stratification and reduced vertical mixing in the ocean driven by global warming will promote the replacement of diatoms by smaller phytoplankton and lead to an overall decrease in productivity and carbon export. Here we present contrary evidence from a synergy of modern observations and palaeo-records that reveal high diatom production and export from stratified waters. Diatom adaptations to stratified waters include the ability to grow in low light conditions in deep chlorophyll maxima; vertical migrations between nutricline depths and the surface, and symbioses with N2-fixing cyanobacteria in diatom-diazotroph associations (DDA). These strategies foster the maintenance of seed populations that may then exploit mixing events induced by storms or eddies, but may also inherently promote blooms. Recent oceanographic observations in the subtropical gyres, at increasingly high temporal and spatial resolutions, have monitored short-lived but often substantial blooms and export of stratified-adapted diatoms including rhizosolenids and the diazotroph-associated Hemiaulus hauckii. Aggregate formation by such diatoms is common and promotes rapid settling thereby minimizing water column remineralization and optimizing carbon flux. Convergence zones associated with oceanic fronts or mesoscale features may also generate substantial flux of stratified-adapted diatom species. Conventional oceanographic observing strategies and sampling techniques under-represent such activity due to the lack of adequate capability to sample the large sized diatoms and colonies involved, the subsurface location of many of these blooms, their common development in thin <3 m layers and their episodic nature. Superbly preserved palaeo-sediment trap records in laminated sediments reveal enhanced production and export from stratified waters mediated by the same taxa. The organic carbon-rich Mediterranean sapropels were the result of production within deep chlorophyll maxima in highly stratified waters dominated by rhizosolenid diatoms but also including H. hauckii. In the Cretaceous when CO2 levels were higher than present, laminated sediments reveal dominant flux also including Hemiaulus and rhizosolenid species. Nitrogen isotope and biomarker studies suggest that, analogous to modern DDA blooms within the subtropical gyres, Hemiaulus blooms in the ancient Mediterranean and within the Cretaceous seas were aided by nitrogen-fixing cyanobacterial symbionts. These lines of evidence suggest that diatom production and associated export of organic carbon, may not decrease, as is widely predicted, but may actually increase with greater ocean stratification, and potentially act as a negative feedback to global warming. However, the key genera involved in such potential feedbacks are underrepresented in both laboratory and field studies and are poorly represented in models. Our findings suggest that a reappraisal is necessary of the way diatoms are represented as plankton functional types (PFTs) in ocean biogeochemical models and that new observing and sampling strategies are also required to study these processes.

  2. Lamin A, farnesylation and aging

    SciTech Connect

    Reddy, Sita; Comai, Lucio

    2012-01-01

    Lamin A is a component of the nuclear envelope that is synthesized as a precursor prelamin A molecule and then processed into mature lamin A through sequential steps of posttranslational modifications and proteolytic cleavages. Remarkably, over 400 distinct point mutations have been so far identified throughout the LMNA gene, which result in the development of at least ten distinct human disorders, collectively known as laminopathies, among which is the premature aging disease Hutchinson-Gilford progeria syndrome (HGPS). The majority of HGPS cases are associated with a single point mutation in the LMNA gene that causes the production of a permanently farnesylated mutant lamin A protein termed progerin. The mechanism by which progerin leads to premature aging and the classical HGPS disease phenotype as well as the relationship between this disorder and the onset of analogous symptoms during the lifespan of a normal individual are not well understood. Yet, recent studies have provided critical insights on the cellular processes that are affected by accumulation of progerin and have suggested that cellular alterations in the lamin A processing pathway leading to the accumulation of farnesylated prelamin A intermediates may play a role in the aging process in the general population. In this review we provide a short background on lamin A and its maturation pathway and discuss the current knowledge of how progerin or alterations in the prelamin A processing pathway are thought to influence cell function and contribute to human aging.

  3. Nonlinear analysis of composite laminates

    SciTech Connect

    Chen, J.

    1984-01-01

    Nonlinear static and dynamic responses of composite laminates were investigated using the finite element method. A nine-node isoparametric quadrilateral element was developed to formulate the finite element equations for a laminated plate under initial deformations and initial stresses according to the Mindlin plate theory and von Karman large deflection assumptions. Static large deflection and postbuckling of plates, impact response of a laminate under initial stresses, free vibration and impact response of buckled composite plates, and non-linear transient and impact analyses of laminated plates with/without initial stresses were studied. In the impact analysis, a experimentally established contact law that accounts for the permanent indentation was employed to calculate the contact force. This contact law was incorporated into the finite element program to study the dynamic response of laminated composites subjected to impact of a hard object. In the nonlinear transient analysis, Newmark time integration algorithm, in conjunction with successive iterations within each time step was used. An iteration scheme with a constant coefficient matrix was used to treat the nonlinear terms. The efficiency and the accuracy of the algorithm were demonstrated for given external loadings. Numerical results were compared with those available in the literature.

  4. Both lamin A and lamin C mutations cause lamina instability as well as loss of internal nuclear lamin organization

    SciTech Connect

    Broers, Jos L.V. . E-mail: jos.broers@molcelb.unimaas.nl; Kuijpers, H.J.H.; Oestlund, C.; Worman, H.J.; Endert, J.; Ramaekers, F.C.S.

    2005-04-01

    We have applied the fluorescence loss of intensity after photobleaching (FLIP) technique to study the molecular dynamics and organization of nuclear lamin proteins in cell lines stably transfected with green fluorescent protein (GFP)-tagged A-type lamin cDNA. Normal lamin A and C proteins show abundant decoration of the inner layer of the nuclear membrane, the nuclear lamina, and a generally diffuse localization in the nuclear interior. Bleaching studies revealed that, while the GFP-tagged lamins in the lamina were virtually immobile, the intranuclear fraction of these molecules was partially mobile. Intranuclear lamin C was significantly more mobile than intranuclear lamina A. In search of a structural cause for the variety of inherited diseases caused by A-type lamin mutations, we have studied the molecular organization of GFP-tagged lamin A and lamin C mutants R453W and R386K, found in Emery-Dreifuss muscular dystrophy (EDMD), and lamin A and lamin C mutant R482W, found in patients with Dunnigan-type familial partial lipodystrophy (FPLD). In all mutants, a prominent increase in lamin mobility was observed, indicating loss of structural stability of lamin polymers, both at the perinuclear lamina and in the intranuclear lamin organization. While the lamin rod domain mutant showed overall increased mobility, the tail domain mutants showed mainly intranuclear destabilization, possibly as a result of loss of interaction with chromatin. Decreased stability of lamin mutant polymers was confirmed by flow cytometric analyses and immunoblotting of nuclear extracts. Our findings suggest a loss of function of A-type lamin mutant proteins in the organization of intranuclear chromatin and predict the loss of gene regulatory function in laminopathies.

  5. Impedances of Laminated Vacuum Chambers

    SciTech Connect

    Burov, A.; Lebedev, V.; /Fermilab

    2011-06-22

    First publications on impedance of laminated vacuum chambers are related to early 70s: those are of S. C. Snowdon [1] and of A. G. Ruggiero [2]; fifteen years later, a revision paper of R. Gluckstern appeared [3]. All the publications were presented as Fermilab preprints, and there is no surprise in that: the Fermilab Booster has its laminated magnets open to the beam. Being in a reasonable mutual agreement, these publications were all devoted to the longitudinal impedance of round vacuum chambers. The transverse impedance and the flat geometry case were addressed in more recent paper of K. Y. Ng [4]. The latest calculations of A. Macridin et al. [5] revealed some disagreement with Ref. [4]; this fact stimulated us to get our own results on that matter. Longitudinal and transverse impendances are derived for round and flat laminated vacuum chambers. Results of this paper agree with Ref. [5].

  6. Lamin-Binding Proteins in Caenorhabditis elegans.

    PubMed

    Dobrzynska, Agnieszka; Askjaer, Peter; Gruenbaum, Yosef

    2016-01-01

    The nuclear lamina, composed of lamins and numerous lamin-associated proteins, is required for mechanical stability, mechanosensing, chromatin organization, developmental gene regulation, mRNA transcription, DNA replication, nuclear assembly, and nuclear positioning. Mutations in lamins or lamin-binding proteins cause at least 18 distinct human diseases that affect specific tissues such as muscle, adipose, bone, nerve, or skin, and range from muscular dystrophies to lipodystrophy, peripheral neuropathy, or accelerated aging. Caenorhabditis elegans has unique advantages in studying lamin-binding proteins. These advantages include the low complexity of genes encoding lamin and lamin-binding proteins, advanced transgenic techniques, simple application of RNA interference, sophisticated genetic strategies, and a large collection of mutant lines. This chapter provides detailed and comprehensive protocols for the genetic and phenotypic analysis of lamin-binding proteins in C. elegans. PMID:26778571

  7. Sampler collection gadget for epilithic diatoms.

    PubMed

    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. PMID:18278320

  8. Basic mechanics of laminated composite plates

    NASA Technical Reports Server (NTRS)

    Nettles, Alan T.

    1994-01-01

    The mechanics of laminated composite materials is presented in a clear manner with only essential derivations included. The constitutive equations in all of their forms are developed and then summarized in a separate section. The effects of hygrothermal effects are included. The prediction of the engineering constants for a laminate are derived. Strength of laminated composites is not covered.

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

    PubMed

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

    2014-03-01

    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. PMID:24343246

  10. Multilayer printed wiring board lamination

    SciTech Connect

    Lula, J.W.

    1980-06-01

    The relationship of delamination resistance of multilayer PWBs made from GF material to manufacturing process variables was investigated. A unique quantitative test method developed during this project shows that delamination resistance is highly sensitive to material conditioning, to innerlayer surface treatment, and to post-lamination storage conditions, but is relatively insensitive to cure cycle variations.

  11. Vacuum multilayer lamination of printed wiring boards

    NASA Astrophysics Data System (ADS)

    Wilkus, J. W.

    1992-11-01

    This experiment investigates vacuum multilayer lamination of rigid/flex, epoxy glass, polyimide glass, and polyimide quartz printed wiring boards. The effectiveness of the vacuum in removing entrapped air during the lamination cycle is demonstrated. The results of the experiment have also shown that vacuum lamination of epoxy glass multilayers improves the delamination resistance. Thus, epoxy glass multilayers that have been vacuum laminated will be able to withstand soldering temperatures longer without delaminating. Also, the experiment shows that vacuum multilayer lamination does not significantly change thickness, layer-to-layer registration, glass transition temperature, dielectric spacing between conductors, electrical resistance following thermal shock test, and other critical printed wiring board properties.

  12. Steady state response of unsymmetrically laminated plates

    SciTech Connect

    Hosokawa, Kenji; Kawashima, Katsuya; Sakata, Toshiyuki

    1995-11-01

    A numerical approach for analyzing the forced vibration problem of a symmetrically laminated FRP (fiber reinforced plastic) composite plate was proposed by the authors. In the present paper, this approach is modified for application to an unsymmetrically laminated FRP composite plate. Numerical calculations are carried out for the clamped antisymmetrically laminated rectangular and elliptical plates which are a kind of unsymmetrically laminated plate. Then,, the effects of the lamina material and the fiber orientation angle on the steady state response are discussed. Furthermore, it is investigated that what structural damping factor is most influenced on the steady state response of an antisymmetrically laminated plate.

  13. Superplasticity in laminated metal composites

    SciTech Connect

    Lesuer, D.; Sherby, O.; Syn, C.

    1998-10-20

    Several studies have shown the possibility of achieving superplastic behavior in laminated metal composites consisting of alternating layers of superplastic and non-superplastic materials. Achieving high rate sensitivity in such a laminate requires the appropriate choice of component materials and component volume fraction as well as deformation under appropriate conditions of strain rate and temperature. The first investigators to study this behavior were Snyder et al. [1], who demonstrated that a non-superplastic material (interstitial free iron) could be made superplastic by lamination with a superplastic material (fine-grained ultrahigh carbon steel (UHCS)). Other laminates in which superplasticity has been observed in a non-superplastic material include UHCS/stainless steel and UHCS/aluminum bronze. In these studies, tensile tests were conducted with the tensile axis parallel to the layers. High strain rate sensitivities were observed and are associated with high tensile ductilities. However, as observed by Tsai et al. [2], obtaining high strain rate sensitivity is a necessary but not sufficient condition for high elongations. Tsai et al. studied the UHCS/brass laminate and found that, despite a strain rate sensitivity exponent of 0.5, only about 60% elongation was obtained. The low tensile ductility resulted from brittle, intergranular fracture of the brass. Once cracking started in the brass, cracks penetrated into the UHCS and premature failure resulted. Thus high elongations requires achieving high strain rate sensitivity as well as avoiding brittle fracture in the less ductile layer. In addition to tension, other deformation modes, including compression [3] and co-extrusion [4], have been studied for deformation response under conditions of high strain rate s

  14. Assessing subglacial processes from diatom fragmentation patterns

    USGS Publications Warehouse

    Scherer, R.P.; Sjunneskog, C.M.; Iverson, N.R.; Hooyer, T.S.

    2004-01-01

    Reconstructing the size and glacial style of past ice-sheet advances requires interpreting complex glacial sedimentary facies. We use diatoms, a major component of Antarctic continental shelf deposits, to infer the physical conditions under which these deposits were emplaced. The degree of diatom fragmentation and the presence of diatoms of varying stratigraphic age in glacial sediments provide means to qualitatively gauge glacial mixing and transport. Here we report an experimentally calibrated index of diatom fragmentation that provides a simple but objective method of assessing the degree of subshearing imparted on marine glacial sedimentary deposits. By using a ring-shear device to subject diatomaceous sediment to stresses comparable to those beneath the Ross ice streams, we quantitatively assess patterns of diatom comminution resulting from compaction and from progressive shear stress. Elongate pennate diatoms are found to break disproportionately to discoid centric diatoms when subjected to shear stress; thus, a simple ratio of unbroken centric to pennate diatoms provides a reliable gauge of past shearing. Comparison of ring-shear results with a suite of previously analyzed sediments that represent a variety of glacial, glacial-marine, and hemipelagic settings of the Ross Sea and subglacial Ross Embayment demonstrates that this index can be employed for estimating relative subglacial stresses in this setting. ?? 2004 Geological Society of America.

  15. Diatom Seasonal Abundance, Assemblages and Lipid Biomarkers: Towards a More Robust Reconstruction of Diatom Paleoproductivity

    NASA Astrophysics Data System (ADS)

    Santos, C.; Zuniga, D.; Hefter, J.; Frjan, M.; Salgueiro, E.; Castro, C. G.; Figueiras, F.; Schefu, E.; Mollenhauer, G.; Abrantes, F. F. G.

    2014-12-01

    Diatoms are the dominant phytoplankton class in coastal upwelling systems, accounting for a large proportion of global primary production. Their frustules preserved in sediments are powerful paleoceanographic and paleoproductivity proxies. However, despite high diatom abundance in the water column, they are frequently affected by dissolution and their sedimentary record is discontinuous. A more robust reconstruction independent of preservation characteristics in the sediments would thus be desirable. Lipid biomarkers have a specific structure that might remain intact in the sediments and may be better preserved under conditions corrosive to diatom frustules. This research aims to investigate the organic imprint of upwelling-related diatom species, which may allow the reconstruction of past primary productivity in areas where diatoms are not preserved in the sediments. To better understand the preservation and chemical signature of diatoms in the sedimentary record, we are studying diatom abundance, assemblages and lipid biomarkers in samples from the water column, sediment traps, surface sediments and diatom cultures recovered at the Iberian Margin. This study aims 1) to understand the present-day seasonal abundance and diversity of diatoms, their relation to the hydrographic conditions, along with their transfer/preservation pathways into the sediments; 2) to identify the major groups of lipid biomarkers related with upwelling diatom species in this area. Diatom abundances and assemblages observed in the water column and sediment traps evidence seasonal primary productivity. Sediment traps and surface sediment samples are dominated by Leptocylindrus spp. and Chaetoceros spp. resting spores, suggesting these genera as productivity tracers. Preliminary results of the biomarkers study show that sterols, known to be one of the major groups of biomarkers related to diatoms, occur in different composition and concentration in the analyzed diatom cultures, water column and sediment trap samples. Others known diatom related lipid biomarkers, namely highly branched isoprenoids and long - chain diols, are also being investigated.

  16. A computational procedure to analyze metal matrix laminates with nonlinear lamination residual strains

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sullivan, T. L.

    1974-01-01

    An approximate computational procedure is described for the analysis of angleplied laminates with residual nonlinear strains. The procedure consists of a combination of linear composite mechanics and incremental linear laminate theory. The procedure accounts for initial nonlinear strains, unloading, and in-situ matrix orthotropic nonlinear behavior. The results obtained in applying the procedure to boron/aluminum angleplied laminates show that this is a convenient means to accurately predict the initial tangent properties of angleplied laminates in which the matrix has been strained nonlinearly by the lamination residual stresses. The procedure predicted initial tangent properties results which were in good agreement with measured data obtained from boron/aluminum angleplied laminates.

  17. Linking diatom deposition in a deep lake with the spring temperature gradient (Tiefer See, NE Germany)

    NASA Astrophysics Data System (ADS)

    Kienel, Ulrike; Kirillin, Georgiy; Brademann, Brian; Plessen, Birgit; Brauer, Achim

    2015-04-01

    Monitoring of deep Lake Tiefer See showed a much larger deposition of diatoms following ice out and a rapid spring stratification in mid April 2013 compared to that following the gradual warming and stratification in mid April 2012. The manifold of diatom individuals in 2013 compared to 2012 amounted to calculated 2.0 compared to 0.15 g silica per square meter and day. The striking difference was the two orders of magnitude larger number of Stephanodiscus sp. in 2013, which were only a minor component in 2012. The monitored weather and lake conditions suggest the 2013-spring bloom was boosted by a quick succession of ice breakup, spring turnover, and stratification leading to nutrient recycling and rapidly improved light conditions. The comparatively longer mixing in spring 2012, calculated using the lake-temperature model FLake, caused population losses that impeded bloom development. To verify the exemplified inverse relation of diatom deposition and mixing duration in spring we use the subannually laminated, recent sediment record of Lake Tiefer See (AD 1924 - 2008), the instrumental series from the meteorological station in Schwerin, and model simulations of the spring mixing. The mixing duration was calculated as the period between water temperatures of 4C and a mixing depth of 6 m were reached for the period 1951 - 2008. To cover the full sediment record a simple estimate of the mixing period was calculated from mean temperatures, i.e. the temperature duration from the first 5C-day to the first of ?5C days. The annual diatom deposition was calculated as the annual average XRF-counts of Si in the sediment record (AD 1924-2008), based on negligible amounts of detrital Si, low deposition of inorganic matter during winter, and a striking balance of IM deposition and Si deposition calculated from the diatom frustules deposited. We find support for the linear and inverse relation of diatom silica deposition with the duration of spring mixing using the modeled mixing duration with 25% explained variability and with 20% using the temperature relation, respectively. The explanation increases to 49%, respectively 53% when the period after AD1980 is removed from the data set. The lack of diatom response during this period is supposed to relate to the primary influence of nutrients from intensive manuring and drainage in the catchment on the algal development at that time.

  18. Laminated composite disc flywheel development

    NASA Astrophysics Data System (ADS)

    Nimmer, R. P.; Torossian, K.; Hickey, J.

    1980-02-01

    A flywheel concept for an electric powered vehicle uses a laminated disc and a filament wound outer ring assembled with an interference fit between these two components. The laminated, central disc is made of S2-glass-epoxy and the outer ring is filament-wound graphite-epoxy. Projections for this particular flywheel design indicate that it will be both practical and relatively inexpensive to produce, and that it will have a high energy density capacity. Two hybrid composite flywheels of 37 cm O.D. were successfully assembled. The spin test data are summarized, the nondestructive test dat are discussed and the fabrication techniques developed for the hybrid flywheel assembly are described.

  19. Plastic Laminate Pulsed Power Development

    SciTech Connect

    ALEXANDER,JEFF A.; SHOPE,STEVEN L.; PATE,RONALD C.; RINEHART,LARRY F.; JOJOLA,JOHN M.; RUEBUSH,MITCHELL H.; CROWE,WAYNE; LUNDSTROM,J.; SMITH,T.; ZAGAR,D.; PRESTWICH,K.

    2000-09-01

    The desire to move high-energy Pulsed Power systems from the laboratory to practical field systems requires the development of compact lightweight drivers. This paper concerns an effort to develop such a system based on a plastic laminate strip Blumlein as the final pulseshaping stage for a 600 kV, 50ns, 5-ohm driver. A lifetime and breakdown study conducted with small-area samples identified Kapton sheet impregnated with Propylene Carbonate as the best material combination of those evaluated. The program has successfully demonstrated techniques for folding large area systems into compact geometry's and vacuum impregnating the laminate in the folded systems. The major operational challenges encountered revolve around edge grading and low inductance, low impedance switching. The design iterations and lessons learned are discussed. A multistage prototype testing program has demonstrated 600kV operation on a short 6ns line. Full-scale prototypes are currently undergoing development and testing.

  20. Specific contribution of lamin A and lamin C in the development of laminopathies

    SciTech Connect

    Sylvius, Nicolas Hathaway, Andrea; Boudreau, Emilie; Gupta, Pallavi; Labib, Sarah; Bolongo, Pierrette M.; Rippstein, Peter; McBride, Heidi; Bilinska, Zofia T.; Tesson, Frederique

    2008-08-01

    Mutations in the lamin A/C gene are involved in multiple human disorders for which the pathophysiological mechanisms are partially understood. Conflicting results prevail regarding the organization of lamin A and C mutants within the nuclear envelope (NE) and on the interactions of each lamin to its counterpart. We over-expressed various lamin A and C mutants both independently and together in COS7 cells. When expressed alone, lamin A with cardiac/muscular disorder mutations forms abnormal aggregates inside the NE and not inside the nucleoplasm. Conversely, the equivalent lamin C organizes as intranucleoplasmic aggregates that never connect to the NE as opposed to wild type lamin C. Interestingly, the lamin C molecules present within these aggregates exhibit an abnormal increased mobility. When co-expressed, the complex formed by lamin A/C aggregates in the NE. Lamin A and C mutants for lipodystrophy behave similarly to the wild type. These findings reveal that lamins A and C may be differentially affected depending on the mutation. This results in multiple possible physiological consequences which likely contribute in the phenotypic variability of laminopathies. The inability of lamin C mutants to join the nuclear rim in the absence of lamin A is a potential pathophysiological mechanism for laminopathies.

  1. Postbuckling of laminated anisotropic panels

    NASA Technical Reports Server (NTRS)

    Jeffrey, Glenda L.

    1987-01-01

    A two-part study of the buckling and postbuckling of laminated anisotropic plates with bending-extensional coupling is presented. The first part involves the development and application of a modified Rayleigh-Ritz analysis technique. Modifications made to the classical technique can be grouped into three areas. First, known symmetries of anisotropic panels are exploited in the selection of approximation functions. Second, a reduced basis technique based on these same symmetries is applied in the linear range. Finally, geometric boundary conditions are enforced via an exterior penalty function approach, rather than relying on choice of approximation functions to satisfy these boundary conditions. Numerical results are presented for both the linear and nonlinear range, with additional studies made to determine the effect of variation in penalty parameter and number of basis vectors. In the second part, six panels possessing anisotropy and bending-extensional coupling are tested. Detailed comparisons are made between experiment and finite element results in order to gain insight into the postbuckling and failure characteristics of such panels. The panels are constructed using two different lamination sequences, and panels with three different aspect ratios were constructed for each lamination sequence.

  2. Diatoms.

    ERIC Educational Resources Information Center

    Hungerford, James J.

    1988-01-01

    Discusses a unicellular component of hytoplankton that can easily be collected and studied in the classroom. Describes how to construct and use a diatometer. Suggests activities that can be done with diatoas collected outdoors or grown in an aquarium. (CW)

  3. Diatom Community Response to Global Change

    NASA Astrophysics Data System (ADS)

    Hook, W. F.; Rose, J.; Langley, J. A.; Coyne, K. J.

    2008-12-01

    Diatoms are ubiquitous components of marine and freshwater environments and are responsible for nearly a quarter of the world's primary production. These microscopic algae are excellent indicators of environmental change and are routinely used as indicators of water quality. Diatom frustules have also been used to infer past climate change. With anticipated increases in atmospheric CO2 and eutrophication, understanding the contribution by diatoms as sinks for carbon in the world's oceans and estuaries is crucial. Benthic diatoms are especially significant in this respect due to their interactions with both atmospheric and sedimentary carbon cycling. We investigated changes in marsh sediment diatom community structure in response to elevated atmospheric carbon dioxide and nitrogen input. Twenty plots of brackish marsh were enclosed in environmental chambers and exposed to two levels of atmospheric CO2 (ambient and elevated) crossed with a nitrogen-addition treatment (2 x 2 factorial) beginning in May 2006. DNA was extracted from sediment samples obtained from environmentally controlled marsh plots in June, 2008. Using diatom-specific primers, the diatom community was amplified by PCR and evaluated by denaturing gradient gel electrophoresis (DGGE). The diatom community composition was then compared across the four treatments (Amb, Amb+N, Elev, Elev+N) using multivariate statistical methods. Multidimensional scaling plots revealed clear grouping of samples according to treatment. A global analysis of similarity test was significant, as were all pairwise comparisons of treatments. The greatest changes in community structure occurred in the elevated CO2 group. In contrast, Amb+N was more similar to Elev+N, suggesting that nitrogen effects may mask elevated CO2 effects on diatom community structure in these plots.

  4. Damage tolerance evaluation of adhesively laminated titanium

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.

    1983-01-01

    Basic damage tolerance properties of Ti-6A1-4V titanium plate can be improved by laminating thin sheets of titanium with adhesives. Compact tension and center cracked tension specimens made from thick plate, thin sheet, and laminated plate (six plies of thin sheet) were tested. The fracture toughness of the laminated plate was 39 percent higher than the monolithic plate. The laminated plate's through the thickness crack growth rate was about 20 percent less than that of the monolithic plate. The damage tolerance life of the surface cracked laminate was 6 to over 15 times the life of a monolithic specimen. A simple method of predicting crack growth in a crack ply of a laminate is presented. Previously announced in STAR as N82-33737

  5. Modelling metabolism of the diatom Phaeodactylum tricornutum.

    PubMed

    Singh, Dipali; Carlson, Ross; Fell, David; Poolman, Mark

    2015-12-01

    Marine diatoms have potential as a biotechnological production platform, especially for lipid-derived products, including biofuels. Here we introduce some features of diatom metabolism, particularly with respect to photosynthesis, photorespiration and lipid synthesis and their differences relative to other photosynthetic eukaryotes. Since structural metabolic modelling of other photosynthetic organisms has been shown to be capable of representing their metabolic capabilities realistically, we briefly review the main approaches to this typeof modelling. We then propose that genome-scale modelling of the diatom Phaeodactylum tricornutum, in response to varying light intensity, could uncover the novel aspects of the metabolic potential of this organism. PMID:26614658

  6. The yield criterion of laminated media.

    NASA Technical Reports Server (NTRS)

    Chou, P. C.; Mcnamee, B. M.; Chou, D. K.

    1973-01-01

    This study examines the yield criteria for anisotropic laminated media. It will be shown that for laminated media with isotropic layers, the criterion of Tsai and Wu is a direct extension of Von Mises'. Also presented here is a set of equations governing the relative positions of the yield ellipses. Furthermore, a general expression for the yield condition of a laminated medium composed of generally anisotropic layers is obtained.

  7. Adsorption kinetics of diatomic molecules.

    PubMed

    Burde, Jared T; Calbi, M Mercedes

    2014-05-01

    The adsorption dynamics of diatomic molecules on solid surfaces is examined by using a Kinetic Monte Carlo algorithm. Equilibration times at increasing loadings are obtained, and explained based on the elementary processes that lead to the formation of the adsorbed film. The ability of the molecules to change their orientation accelerates the overall uptake and leads to competitive kinetic behaviour between the different orientations. The dependence of the equilibration time on coverage follows the same decreasing trend obtained experimentally for ethane adsorption on closed-end carbon nanotube bundles. The exploration of molecule-molecule interaction effects on this trend provides relevant insights to understand the kinetic behaviour of other species, from simpler molecules to larger polyatomic molecules, adsorbing on surfaces with different binding strength. PMID:24654004

  8. Geometrically nonlinear analysis of laminated elastic structures

    NASA Technical Reports Server (NTRS)

    Reddy, J. N.

    1984-01-01

    Laminated composite plates and shells that can be used to model automobile bodies, aircraft wings and fuselages, and pressure vessels among many other were analyzed. The finite element method, a numerical technique for engineering analysis of structures, is used to model the geometry and approximate the solution. Various alternative formulations for analyzing laminated plates and shells are developed and their finite element models are tested for accuracy and economy in computation. These include the shear deformation laminate theory and degenerated 3-D elasticity theory for laminates.

  9. Compression failure in reduced adhesion fiber laminates

    NASA Astrophysics Data System (ADS)

    Swanson, Stephen R.; Colvin, Glenn E.

    1993-04-01

    A micromechanics model for compression failure of laminates is verified through a comparison with experiments performed on laminates with specially treated fiber-matrix interphases. Tests were carried out on control specimens based on fibers with standard surface treatment and on laminates in which the fiber were treated with a release agent to reduce fiber-matrix adhesion. Results show that the specimens with reduced fiber adhesion exhibited a loss of strength of up to 75 percent, indicating the effects of loss of matrix support. It is concluded that the model explains a number of important experimental features and thus gives insight into compression failure of laminates.

  10. Fatigue mechanisms in metal matrix composite laminates

    NASA Technical Reports Server (NTRS)

    Dvorak, G. J.; Johnson, W. S.

    1981-01-01

    Certain aspects of the damage process are described. The shakedown phenomenon in laminates is first explained. This is followed by a presentation of matrix test data used in evaluating the shakedown limits of the laminates used in the subsequent experiments. Test results suggesting that there is no loss of elastic stiffness in laminates loaded at constant amplitudes within their shakedown limits are presented. Damage accumulation and the development of the saturation damage state are illustrated by experimental results on specimens loaded outside the shakedown range. Attention is also given to the behavior of laminates subjected to variable cyclic loading.

  11. Lamins at the crossroads of mechanosignaling

    PubMed Central

    Osmanagic-Myers, Selma; Dechat, Thomas

    2015-01-01

    The intermediate filament proteins, A- and B-type lamins, form the nuclear lamina scaffold adjacent to the inner nuclear membrane. B-type lamins confer elasticity, while A-type lamins lend viscosity and stiffness to nuclei. Lamins also contribute to chromatin regulation and various signaling pathways affecting gene expression. The mechanical roles of lamins and their functions in gene regulation are often viewed as independent activities, but recent findings suggest a highly cross-linked and interdependent regulation of these different functions, particularly in mechanosignaling. In this newly emerging concept, lamins act as a “mechanostat” that senses forces from outside and responds to tension by reinforcing the cytoskeleton and the extracellular matrix. A-type lamins, emerin, and the linker of the nucleoskeleton and cytoskeleton (LINC) complex directly transmit forces from the extracellular matrix into the nucleus. These mechanical forces lead to changes in the molecular structure, modification, and assembly state of A-type lamins. This in turn activates a tension-induced “inside-out signaling” through which the nucleus feeds back to the cytoskeleton and the extracellular matrix to balance outside and inside forces. These functions regulate differentiation and may be impaired in lamin-linked diseases, leading to cellular phenotypes, particularly in mechanical load-bearing tissues. PMID:25644599

  12. An improved lamination technique for solar arrays

    NASA Astrophysics Data System (ADS)

    Garcia, A., III; Olson, C.

    Encapsulating solar cells by lamination has been plagued with problems such as bubbles, cell shifting, ripples, and cracked cells. A low-cost laminating procedure has been developed using a double vacuum bagging technique and recently improved formulations of ethylene vinyl acetate, successfully minimizing these problems. The lamination fixturing used is described. The causes and cures of various problems are discussed and solutions to these problems presented. The apparent modulus of the face sheet seen by the module being laminated is believed to be the primary variable which must be optimized. Conditions at the module edge are also considered to be important for producing an acceptable product.

  13. An improved lamination technique for solar arrays

    NASA Technical Reports Server (NTRS)

    Garcia, A., III; Olson, C.

    1980-01-01

    Encapsulating solar cells by lamination has been plagued with problems such as bubbles, cell shifting, ripples, and cracked cells. A low-cost laminating procedure has been developed using a double vacuum bagging technique and recently improved formulations of ethylene vinyl acetate, successfully minimizing these problems. The lamination fixturing used is described. The causes and cures of various problems are discussed and solutions to these problems presented. The apparent modulus of the face sheet seen by the module being laminated is believed to be the primary variable which must be optimized. Conditions at the module edge are also considered to be important for producing an acceptable product.

  14. Diatoms in space: testing prospects for reliable diatom nanotechnology in microgravity

    NASA Astrophysics Data System (ADS)

    Gordon, Richard; Hoover, Richard B.; Tuszynski, Jack A.; de Luis, Javier; Camp, Philip J.; Tiffany, Mary Ann; Nagy, Stephen S.; Fayek, Mostafa; Lopez, Pascal J.; Lerner, Beatriz E.

    2007-09-01

    The worldwide effort to grow nanotechnology, rather than use lithography, focuses on diatoms, single cell eukaryotic algae with ornate silica shells, which can be replaced by oxides and ceramics, or reduced to elemental silicon, to create complex nanostructures with compositions of industrial and electronics importance. Diatoms produce an enormous variety of structures, some of which are microtubule dependent and perhaps sensitive to microgravity. The NASA Single Loop for Cell Culture (SLCC) for culturing and observing microorganisms permits inexpensive, low labor in-space experiments. We propose to send up to the International Space Station diatom cultures of the three diatom species whose genomes are currently being sequenced, plus the giant diatoms of Antarctica (up to 6 mm length for a single cell) and the unique colonial diatom, Bacillaria paradoxa. Bacillaria cells move against each other in partial synchrony, like a sliding deck of cards, by a microfluidics mechanism. Will normal diatoms have aberrant patterns, shapes or motility compared to ground controls? The generation time is typically one day, so that many generations may be examined from one flight. Rapid, directed evolution may be possible running the SLCC as a compustat. The shell shapes and patterns are preserved in hard silica, so that the progress of normal and aberrant morphogenesis may be followed by drying samples on a moving filter paper "diatom tape recorder". With a biodiversity of 100,000 distinct species, diatom nanotechnology may offer a compact and portable nanotechnology toolkit for space exploration anywhere.

  15. DIATOMS: POWERFUL INDICATORS OF ENVIRONMENTAL CHANGE

    EPA Science Inventory

    Diatoms are being used increasingly to assess short- and long-term environmental change, because they are informative, versatile, flexible, and powerful ecological indicators. iatoms respond rapidly to changes in many ecological characteristics. ssemblages are usually diverse and...

  16. Amino Acid Biosynthesis Pathways in Diatoms

    PubMed Central

    Bromke, Mariusz A.

    2013-01-01

    Amino acids are not only building blocks for proteins but serve as precursors for the synthesis of many metabolites with multiple functions in growth and other biological processes of a living organism. The biosynthesis of amino acids is tightly connected with central carbon, nitrogen and sulfur metabolism. Recent publication of genome sequences for two diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum created an opportunity for extensive studies on the structure of these metabolic pathways. Based on sequence homology found in the analyzed diatomal genes, the biosynthesis of amino acids in diatoms seems to be similar to higher plants. However, one of the most striking differences between the pathways in plants and in diatomas is that the latter possess and utilize the urea cycle. It serves as an important anaplerotic pathway for carbon fixation into amino acids and other N-containing compounds, which are essential for diatom growth and contribute to their high productivity. PMID:24957993

  17. Oceanographic and Biogeochemical Insights from Diatom Genomes

    NASA Astrophysics Data System (ADS)

    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.

  18. Hydrodynamics of diatom chains and semiflexible fibres

    PubMed Central

    Nguyen, Hoa; Fauci, Lisa

    2014-01-01

    Diatoms are non-motile, unicellular phytoplankton that have the ability to form colonies in the form of chains. Depending upon the species of diatoms and the linking structures that hold the cells together, these chains can be quite stiff or very flexible. Recently, the bending rigidities of some species of diatom chains have been quantified. In an effort to understand the role of flexibility in nutrient uptake and aggregate formation, we begin by developing a three-dimensional model of the coupled elastichydrodynamic system of a diatom chain moving in an incompressible fluid. We find that simple beam theory does a good job of describing diatom chain deformation in a parabolic flow when its ends are tethered, but does not tell the whole story of chain deformations when they are subjected to compressive stresses in shear. While motivated by the fluid dynamics of diatom chains, our computational model of semiflexible fibres illustrates features that apply widely to other systems. The use of an adaptive immersed boundary framework allows us to capture complicated buckling and recovery dynamics of long, semiflexible fibres in shear. PMID:24789565

  19. Asymptotical modeling of thermopiezoelastic laminates

    NASA Astrophysics Data System (ADS)

    Long, Yufei; Yu, Wenbin

    2016-01-01

    A general anisotropic laminated plate model with thermal deformation and two-way coupled piezoelectric effect and pyroelectric effect is constructed using the variational asymptotic method. Total potential energy contains strain energy, electric potential energy and energy caused by temperature change and external loads. The feature of small thickness and large in-plane dimension of plate structures helps to asymptotically simplify the three-dimensional analysis to a two-dimensional analysis on the reference surface and a one-dimensional analysis through the thickness. Several numerical examples are studied. The present model is validated by the excellent agreement between the results from 3D finite element analyses and the present model.

  20. Symmetries in laminated composite plates

    NASA Technical Reports Server (NTRS)

    Noor, A. K.

    1976-01-01

    The different types of symmetry exhibited by laminated anisotropic fibrous composite plates are identified and contrasted with the symmetries of isotropic and homogeneous orthotropic plates. The effects of variations in the fiber orientation and the stacking sequence of the layers on the symmetries exhibited by composite plates are discussed. Both the linear and geometrically nonlinear responses of the plates are considered. A simple procedure is presented for exploiting the symmetries in the finite element analysis. Examples are given of square, skew and polygonal plates where use of symmetry concepts can significantly reduce the scope and cost of analysis.

  1. Residual stresses in angleplied laminates and their effects on laminate behavior

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1978-01-01

    Evidence of the presence of lamination residual stresses in angleplied laminates were transply cracks and warpage of unsymmetric laminates which occur prior to application of any mechanical load. Lamination residual strains were measured using the embedded strain gage technique. These strains result from the temperature differences between cure and room temperature and vary linearly within this temperature range. Lamination residual stresses were usually present in angleplied fiber composites laminates; they were also present in unidirectional hybrids and superhybrids. For specific applications, the magnitudes of lamination residual stresses were determined and evaluated relative to the anticipated applied stresses. Particular attention was given to cyclic thermal loadings in applications where the thermal cycling takes place over a wide temperature range.

  2. Lamin Dysfunction Mediates Neurodegeneration in Tauopathies.

    PubMed

    Frost, Bess; Bardai, Farah H; Feany, Mel B

    2016-01-11

    The filamentous meshwork formed by the lamin nucleoskeleton provides a scaffold for the anchoring of highly condensed heterochromatic DNA to the nuclear envelope, thereby establishing the three-dimensional architecture of the genome [1]. Insight into the importance of lamins to cellular viability can be gleaned from laminopathies, severe disorders caused by mutations in genes encoding lamins. Acellular consequence of lamin dysfunction in laminopathies is relaxation of heterochromatic DNA [1]. Similarly, we have recently reported the widespread relaxation of heterochromatin in tauopathies [1]: age-related progressive neurodegenerative disorders, including Alzheimer's disease, that are pathologically characterized by aggregates of phosphorylated tau protein in the brain [2, 3]. Herewe demonstrate that acquired lamin misregulation though aberrant cytoskeletal-nucleoskeletal coupling promotes relaxation of heterochromatin and neuronal death in an invivo model of neurodegenerative tauopathy. Genetic manipulation of lamin function significantly modifies neurodegeneration invivo, demonstrating that lamin pathology plays acausal role in tau-mediated neurotoxicity. We show that lamin dysfunction is conserved in human tauopathy, as super-resolution microscopy reveals a significantly disrupted nuclear lamina in postmortem tissue from human Alzheimer's disease brain. Our study provides strong evidence that tauopathies are neurodegenerative laminopathies and identifies a new pathway mediating neuronal death in currently untreatable human neurodegenerative disorders, including Alzheimer's disease. PMID:26725200

  3. Bumper-protected laminated spacecraft mainwalls

    NASA Technical Reports Server (NTRS)

    Kinslow, R.

    1973-01-01

    A study was made of the meteoroid impact resistance of bumper-protected mainwalls of both solid aluminum and polycarbonate-aluminum laminates. Semi-empirical models of the debris cloud and stress waves were formulated. Results indicated that a laminated mainwall affords greater impact resistance than a solid aluminum mainwall of the same weight.

  4. Silicone modified resins for graphite fiber laminates

    NASA Technical Reports Server (NTRS)

    Frost, L. W.; Bower, G. M.

    1980-01-01

    Six silicone modified resins were selected for evaluation in unidirectional filament wound graphite laminates. Neat samples of these resins had 1,000 C char residues of 6-63%. The highest flexural values measured for the laminates were a strength of 1,220 MPa and a modulus of 105 GPa. The highest interlaminar shear strength was 72 MPa.

  5. Numbers, sizes, and types of diatoms around estuaries for a diatom test.

    PubMed

    Kakizaki, Eiji; Kozawa, Shuji; Sakai, Masahiro; Yukawa, Nobuhiro

    2011-09-01

    We collected 68 fresh, brackish, and seawater samples from various sites around the estuaries of 2 rivers at high and low tides. Seawater flowed approximately 2.4 (salinity, 2.2% at the site) and 1.2 km (1.8%) upstream of the estuaries, but the surface comprised essentially fresh water up to the mouth. Sites contained 69 to 22,200 diatoms/50 mL of water, and the numbers varied by depth and at sites separated by only approximately 1.2 km. Diatoms ranged from 2.8 to 429 ?m (mean range, 16.1-59.2 ?m) in size. Large pennate diatoms populated fresh water areas, and most sedimented before reaching the sea. Numbers of pennate diatoms of less than 20 ?m were decreased in areas of seawater. Numbers of centric diatoms tended to increase nearer the sea, and seawater contained large centric diatoms. Brackish water containing large volumes of seawater was easily discriminated by assemblages of marine diatoms, unlike that containing a little seawater, because marine diatoms could be found in fresh water around estuaries. Tides and the nature of the river often altered diatomaceous assemblages at the same estuarial sites. Caution is recommended for forensic interpretation of aqueous media to deduce drowning sites. PMID:21725229

  6. Lamins of the sea lamprey (Petromyzon marinus) and the evolution of the vertebrate lamin protein family.

    PubMed

    Schilf, Paul; Peter, Annette; Hurek, Thomas; Stick, Reimer

    2014-07-01

    Lamin proteins are found in all metazoans. Most non-vertebrate genomes including those of the closest relatives of vertebrates, the cephalochordates and tunicates, encode only a single lamin. In teleosts and tetrapods the number of lamin genes has quadrupled. They can be divided into four sub-types, lmnb1, lmnb2, LIII, and lmna, each characterized by particular features and functional differentiations. Little is known when during vertebrate evolution these features have emerged. Lampreys belong to the Agnatha, the sister group of the Gnathostomata. They split off first within the vertebrate lineage. Analysis of the sea lamprey (Petromyzon marinus) lamin complement presented here, identified three functional lamin genes, one encoding a lamin LIII, indicating that the characteristic gene structure of this subtype had been established prior to the agnathan/gnathostome split. Two other genes encode lamins for which orthology to gnathostome lamins cannot be designated. Search for lamin gene sequences in all vertebrate taxa for which sufficient sequence data are available reveals the evolutionary time frame in which specific features of the vertebrate lamins were established. Structural features characteristic for A-type lamins are not found in the lamprey genome. In contrast, lmna genes are present in all gnathostome lineages suggesting that this gene evolved with the emergence of the gnathostomes. The analysis of lamin gene neighborhoods reveals noticeable similarities between the different vertebrate lamin genes supporting the hypothesis that they emerged due to two rounds of whole genome duplication and makes clear that an orthologous relationship between a particular vertebrate paralog and lamins outside the vertebrate lineage cannot be established. PMID:25059907

  7. Composite laminate optimization program suitable for microcomputers

    NASA Technical Reports Server (NTRS)

    Flanagan, G. V.; Palazotto, A. N.

    1984-01-01

    The design of a composite panel requires some way of finding the minimum thickness laminate which will withstand the load requirements without failure. The mathematical complexity of this problem dictates the use of nonlinear optimization techniques. Specialized laminate optimization programs were developed which are compact and efficient enough to run on microcomputers. Only stresses at a point and inplane loads and deflections are considered. The programs are simple to use and require no knowledge of optimization. Techniques are developed which find minimum thickness laminates with either ply ratios or ply angles as design variables. A method is presented for finding the optimum orientation for the axis of symmetry of an orthotropic laminate. The orthotropic laminate program uses an approximate failure theory, which speed up computations dramatically.

  8. Stationary turbine component with laminated skin

    DOEpatents

    James, Allister W.

    2012-08-14

    A stationary turbine engine component, such as a turbine vane, includes a internal spar and an external skin. The internal spar is made of a plurality of spar laminates, and the external skin is made of a plurality of skin laminates. The plurality of skin laminates interlockingly engage the plurality of spar laminates such that the external skin is located and held in place. This arrangement allows alternative high temperature materials to be used on turbine engine components in areas where their properties are needed without having to make the entire component out of such material. Thus, the manufacturing difficulties associated with making an entire component of such a material and the attendant high costs are avoided. The skin laminates can be made of advanced generation single crystal superalloys, intermetallics and refractory alloys.

  9. Wettability of graphene-laminated micropillar structures

    SciTech Connect

    Bong, Jihye; Seo, Keumyoung; Ju, Sanghyun E-mail: shju@kgu.ac.kr; Park, Ji-Hoon; Ahn, Joung Real E-mail: shju@kgu.ac.kr

    2014-12-21

    The wetting control of graphene is of great interest for electronic, mechanical, architectural, and bionic applications. In this study, the wettability of graphene-laminated micropillar structures was manipulated by changing the height of graphene-laminated structures and employing the trichlorosilane (HDF-S)-based self-assembly monolayer. Graphene-laminated micropillar structures with HDF-S exhibited higher hydrophobicity (contact angle of 129.5°) than pristine graphene thin film (78.8°), pristine graphene-laminated micropillar structures (97.5°), and HDF-S self-assembled graphene thin film (98.5°). Wetting states of the graphene-laminated micropillar structure with HDF-S was also examined by using a urea solution, which flowed across the surface without leaving any residues.

  10. Strength of tape cast and laminated ceramics

    SciTech Connect

    Ham-Su, R.; Wilkinson, D.S.

    1995-06-01

    Monolithic Al{sub 2}O{sub 3} ceramic laminates were fabricated via a tape casting process. The strength of the single tapes was compared with that of laminates, using biaxial flexure tests. The fracture stress was similar. However, the laminates presented a lower Weibull modulus. The feasibility of eliminating or diminishing void-type flaws present in the green tapes was also assessed. To this end, tapes were first punctured, then laminated and sintered, and the effect of these known flaws in the final ceramic was assessed in four-point flexure tests. The thermocompression of green tapes during laminate fabrication was found to modify the flaws to a more forgiving morphology.

  11. Wettability of graphene-laminated micropillar structures

    NASA Astrophysics Data System (ADS)

    Bong, Jihye; Seo, Keumyoung; Park, Ji-Hoon; Ahn, Joung Real; Ju, Sanghyun

    2014-12-01

    The wetting control of graphene is of great interest for electronic, mechanical, architectural, and bionic applications. In this study, the wettability of graphene-laminated micropillar structures was manipulated by changing the height of graphene-laminated structures and employing the trichlorosilane (HDF-S)-based self-assembly monolayer. Graphene-laminated micropillar structures with HDF-S exhibited higher hydrophobicity (contact angle of 129.5) than pristine graphene thin film (78.8), pristine graphene-laminated micropillar structures (97.5), and HDF-S self-assembled graphene thin film (98.5). Wetting states of the graphene-laminated micropillar structure with HDF-S was also examined by using a urea solution, which flowed across the surface without leaving any residues.

  12. Stiffnesses of laminated flat plates

    NASA Astrophysics Data System (ADS)

    1994-04-01

    ESDU 94003 gives formulae for the in-plane and flexural stiffnesses of laminated flat plates built-up from thin orthotropic layers that may have different material properties, thicknesses, and orientations of their principal axes of orthotropy. The influence of the lay-up arrangement on the plate stiffnesses is explained. A complete list of possible forms of the stiffness matrices is provided with in each case examples of possible lay-up arrangements that will give them. Although it is normally convenient to use the central plane of the plate as the reference plane, subsequent calculations may be simplified by adopting another parallel reference plane; formulae are given for the values of the coupled in-plane and flexural stiffness matrix and the flexural stiffness matrix of the plate for such a shift of reference plane. The in-plane stiffness matrix is unaffected. A worked example illustrates the calculation of the stiffnesses. The relationship between the stiffnesses of a layer and the complete matrix of the elastic constants for an anisotropic solid is included. The relationship of the stiffnesses of both isotropic plates and sandwich panels with the laminated plate stiffnesses is also given. Equations are given relating the stress and strain in a layer in one axis system to those in another. The formulae apply to composite plates with systematic fibrous reinforcements in metallic or non-metallic matrices.

  13. The Glass Menagerie: diatoms for novel applications in nanotechnology.

    PubMed

    Gordon, Richard; Losic, Dusan; Tiffany, Mary Ann; Nagy, Stephen S; Sterrenburg, Frithjof A S

    2009-02-01

    Diatoms are unicellular, eukaryotic, photosynthetic algae that are found in aquatic environments. Diatoms have enormous ecological importance on this planet and display a diversity of patterns and structures at the nano- to millimetre scale. Diatom nanotechnology, a new interdisciplinary area, has spawned collaborations in biology, biochemistry, biotechnology, physics, chemistry, material science and engineering. We survey diatom nanotechnology since 2005, emphasizing recent advances in diatom biomineralization, biophotonics, photoluminescence, microfluidics, compustat domestication, multiscale porosity, silica sequestering of proteins, detection of trace gases, controlled drug delivery and computer design. Diatoms might become the first organisms for which the gap in our knowledge of the relationship between genotype and phenotype is closed. PMID:19167770

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

    PubMed Central

    Gügi, Bruno; Le Costaouec, Tinaïg; Burel, Carole; Lerouge, Patrice; Helbert, William; Bardor, Muriel

    2015-01-01

    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. PMID:26393622

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

    PubMed

    Ggi, Bruno; Le Costaouec, Tinag; Burel, Carole; Lerouge, Patrice; Helbert, William; Bardor, Muriel

    2015-09-01

    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 CO? 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. PMID:26393622

  16. Exotic diatomic molecules of cesium

    NASA Astrophysics Data System (ADS)

    Tallant, Jonathan E.

    The observation of a new, polar class of homonuclear diatomic molecules, called trilobite molecules, is presented. The molecules have permanent electric dipole moments of 20--100 Debye. The observations are in agreement with calculations carried out by our collaborators at the Institute of Theoretical Atomic, Molecular, and Optical Physics (ITAMP), at Harvard University. The unique mechanism that binds the molecules will be described. The molecules are not observable inside of a Magneto-Optical Trap (MOT) due to the low density of trapped atoms, 1 x 1010 cm -3. This thesis also describes the improvements to the apparatus in an effort to increase the density of trapped atoms. The improvements are two-fold. First, a system to slow an atomic beam using the Zeeman effect is described. The slowed atomic beam is used to load the MOT instead of from a background vapor, enhancing both the loading rate and the number of trapped atoms. A Monte Carlo simulation of the slowing process is presented. Second, an optical dipole trapping system has been developed and successfully implemented which captures atoms at a temperature of 40 muK and at a density of 2 x 1013 cm-3. The increase in density augments two-body event rates by a factor of 4 x 106, and allows experiments to probe smaller interaction distances. This is demonstrated by the photoassociation of these exotic trilobite molecules.

  17. Updated diatom biostratigraphy for Monterey Formation

    SciTech Connect

    Barron, J.A.

    1986-04-01

    Diatom biostratigraphy for the latest early Miocene to earliest Pliocene of California is updated by new correlations to absolute time, and additional secondary datum levels (first and last occurrences) are identified. As yet, late middle Miocene to latest Miocene (14-6 Ma) diatom datum levels have not been correlated directly with magnetic stratigraphy in the northeast Pacific. Absolute ages are estimated indirectly by correlating northeast Pacific diatom datum levels with tropical Pacific diatom datum levels, which are correlated directly with magnetic stratigraphy. DSDP sections in the northeastern Pacific (Sites 470, 472) and northwestern Pacific (Site 438) contain mixtures of tropical and temperate diatom species. Graphical correlation techniques applied to these sections correlate temperate datum levels to tropical datum levels and, hence, to magnetic stratigraphy. Absolute ages for these datum levels are then estimated using magnetic time scales. W.A. Berggren et al suggested a new correlation of magnetic anomaly 5 (8.92-10.42 Ma) with magnetic polarity Chron 11, rather than with Chron 9. Significant changes in absolute age estimates from late middle Miocene to early late Miocene diatom zones and subzones are as follows: base of Denticulopsis hustedtii-D. lauta zone = 13.8 Ma; base of subzone b = 12.7 Ma; base of subzone c = 11.4 Ma; base of subzone d = 8.9 Ma; base of D. hustedtii zone = 8.4 Ma; top of D. hustedtii zone (base of Thalassiosira antiqua zone) = 7.6 Ma. Graphical correlation techniques have been applied to stratigraphic sections from Newport Beach, Naples coastal bluffs, Lompoc, Monterey, and the type Luisian area near Paso Robles, as well as from DSDP Sites 173, 468, 469, and 470, and have identified 31 secondary diatom datums and 4 silicoflagellate datums that are the most useful for correlations.

  18. High-resolution past environmental reconstruction in East Asia using annually laminated lake sediments of Lake Megata in northeastern Japan

    NASA Astrophysics Data System (ADS)

    Yamada, K.; Gotanda, K.; Yonenobu, H.; Shinozuka, Y.; Kitagawa, J.; Makohonienko, M.; Schwab, M.; Haraguchi, T.; Yasuda, Y.

    2007-12-01

    37 m-long non-glacial varved sequences were taken from Ichi-no-Megata maar in Oga Peninsula, Akita, northern part of Japan. Ichi-no-Megata maar occupies 0.25 km2 with a maximum water depth of ca. 45.1 m. The shape of lake is a kettle-type basin and the deepest bottom basin is very flat. We took core samples (named IMG06 core) at the center of the lake in November to December in 2006. In order to take completely continuous maar sediment, we drilled three holes and take every sample from each hole which apart only few meters. In this drilling campaign, we can 37 m-long continuous maar sediment except thick volcanic deposits from 26.5 to 31.7m in core. The sedimentological feature of IMG06 core is dominated by thin lamination clay/silt from most top part up to 37 m with turbidites characterized upward fining structure. The SEM image observation of lamination reveals that sponge-like lamina consists of diatom assemblage against dark colored lamina consists of mixture of detritus minerals, clay minerals, and diatom. It means sponge-like lamina deposits during spring season, and later one deposits during another three seasons, and then these thin lamination of IMG06 core could be identified as annual lamination (varves). This interpretation is supported by the correlation of historic event as earthquake and tunnel construction. In this IMG06 core, six volcanic ashes are found and we have also analyzed radiocarbon dating from 38 horizons of the core to use leaf and seeds inter-bedded varves. As the results, the IMG06 core covers from 25,000 to 4,000 14C yr BP with stable sedimentation rates (0.71mm/year).

  19. Diatom-based reconstruction of the Lake Czechowskie trophy status in the last 2000 years (Tuchola Forest, Northern Poland)

    NASA Astrophysics Data System (ADS)

    Rzodkiewicz, Monika; Hübener, Thomas; Ott, Florian; Kramkowski, Mateusz; Obremska, Milena; Słowiński, Michał; Zawiska, Izabela; Błaszkiewicz, Mirosław; Brauer, Achim

    2015-04-01

    Lakes ecosystems are very sensitive to climate and environment fluctuation. In lake sediments there are preserved remains of plant and animals that lived in the lake and its surroundings in the past. In paleolimnological research we analyse the species composition of the assemblages preserved in the sediments and on this base reconstruct past environment changes (climate changes). One of the most commonly used bio-proxy for reconstruction of lake development are subfossil diatoms. Diatoms are commonly used to reconstruct such environment parameters as: pH, nutrient status, salinity or temperature. In our study we analysed the sediments of Lake Czechowskie, which is located in the northern part of the Tuchola Forest region (Northern Poland). Lacustrine sediments of this lake are laminated and therefore are unique archive to reconstruct climate and environmental changes in Northern Polish Lowland. In this research we focused on the last 2000 years and with high resolution analyzed diatoms, pollen and sediment geochemistry. The core chronology is based varve counting, 14C AMS dating of terrestrial macro remains, 137Cs activity measurement. Diatoms communities during the last 2000 years were rich and mostly very well preserved. A characteristic feature of those communities is the dominance of typically planktonic species of the spring phytoplankton, as the oligo to mesotraphent Cyclotella comensis but also the eutraphent Stephanodiscus parvus. We also aimed at quantitative reconstruction of the pH and eutrophication(TP) using diatom-based transfer functions in order to identify reference conditions for the Lake Czechowskie. Transfer function are based on the assumption that the modern biological proxies, which ecological requirements are known, can be used to quantitative reconstructions of the past changes. This study is a contribution to the Virtual Institute ICLEA (Integrated Climate and Landscape Evolution Analysis) funded by the Helmholtz Association. The research was supported by the National Science Centre Poland (grant NCN 2011/01/B/ST10/07367).

  20. Extremophile Diatoms: Implications to the Drake Equation

    NASA Technical Reports Server (NTRS)

    Sterrenburg, Frithjof A. S.; Hoover, Richard B.

    2011-01-01

    Diatoms are unicellular Eukaryotes that (as a group and phylogenetically) are not strictly regarded as extremophiles , since the vast majority of diatoms are mesophilic photoautotrophs. However, among the terrestrial Eukaryotes, diatoms are by far the single group of organisms with the ability to inhabit the greatest range of hostile environments on Earth. They are the dominant eukaryotes in the polar regions; in fumaroles, hot springs and geysers; and in hypersaline and hyperalkaline lakes and pools. Cryophilic species such as Fragilaria sublinearis and Chaetoceras fragilis are able to carry out respiration at extremely low rates at low temperatures in darkness. The Drake Equation refers to the likelihood of there being intelligent life at the technological level of electromagnetic communication. However, consideration of the range of conditions suitable for the habitability of eukaryotic diatoms and prokaryotic extremophiles, the likelihood that life exists elsewhere in the cosmos becomes many orders of magnitude greater than that predicted by the classical Drake Equation. In this paper we review the characteristics of diatoms as eukaryotic extremophiles and consider the implications to adjustments needed to the Drake Equation to assess the possibility that life exists elsewhere in the Universe.

  1. Laminitis and the equine metabolic syndrome.

    PubMed

    Johnson, Philip J; Wiedmeyer, Charles E; LaCarrubba, Alison; Ganjam, V K Seshu; Messer, Nat T

    2010-08-01

    Although much has been written about laminitis in the context of its association with inflammatory processes, recognition is growing that most cases of laminitis examined by veterinarians in private practice are those associated with pasture grazing, obesity, and insulin resistance (IR). The term 'endocrinopathic laminitis' has been adopted to classify the instances of laminitis in which the origin seems to be more strongly associated with an underlying endocrinopathy, such as either IR or the influence of corticosteroids. Results of a recent study suggest that obesity and IR represent the most common metabolic and endocrinopathic predispositions for laminitis in horses. IR also plays an important role in the pathogenesis of laminitis that develops when some horses or ponies are allowed to graze pastures at certain times of the year. The term equine metabolic syndrome (EMS) has been proposed as a label for horses whose clinical examination results (including both physical examination and laboratory testing) suggest heightened risk for developing laminitis as a result of underlying IR. PMID:20699172

  2. Indentation law for composite laminates

    NASA Technical Reports Server (NTRS)

    Yang, S. H.; Sun, C. T.

    1982-01-01

    Static indentation tests are described for glass/epoxy and graphite/epoxy composite laminates with steel balls as the indentor. Beam specimens clamped at various spans were used for the tests. Loading, unloading, and reloading data were obtained and fitted into power laws. Results show that: (1) contact behavior is not appreciably affected by the span; (2) loading and reloading curves seem to follow the 1.5 power law; and (3) unloading curves are described quite well by a 2.5 power law. In addition, values were determined for the critical indentation, alpha sub cr which can be used to predict permanent indentations in unloading. Since alpha sub cr only depends on composite material properties, only the loading and an unloading curve are needed to establish the complete loading-unloading-reloading behavior. Previously announced in STAR as N82-15123

  3. Indentation law for composite laminates

    NASA Technical Reports Server (NTRS)

    Yang, S. H.

    1981-01-01

    Static indentation tests are described for glass/epoxy and graphite/epoxy composite laminates with steel balls as the indentor. Beam specimens clamped at various spans were used for the tests. Loading, unloading, and reloading data were obtained and fitted into power laws. Results show that: (1) contact behavior is not appreciably affected by the span; (2) loading and reloading curves seem to follow the 1.5 power law; and (3) unloading curves are described quite well by a 2.5 power law. In addition, values were determined for the critical indentation, alpha sub cr which can be used to predict permanent indentations in unloading. Since alpha sub cr only depends on composite material properties, only the loading and an unloading curve are needed to establish the complete loading-unloading-reloading behavior.

  4. Method of laminating structural members

    NASA Technical Reports Server (NTRS)

    Heier, W. C. (Inventor)

    1974-01-01

    A laminate is obtained by providing a lightweight core material, such as a honeycombed plastic or metal, within the cavity defined by an annular mold cavity frame. Face sheets, which are to be bonded to the core material, are provided on opposite sides of the frame and extend over the frame, thus sealing the core material in the cavity. An adhesive is provided between the core material and the face sheets and the combined thickness of the core material and adhesive is a close fit within the opposed face sheets. A gas tight seal, such as an O-ring gasket, is provided between the frame and the face sheet members to form a gas tight cavity between the face sheet members and the frame. External heat and pressure are used to bond the face sheets to the core material. Gas pressure is introduced into the sealed cavity to minimize out-gasing of the adhesive.

  5. Damage of hybrid composite laminates

    NASA Astrophysics Data System (ADS)

    Haery, Haleh A.; Kim, Ho Sung

    2013-08-01

    Hybrid laminates consisting of woven glass fabric/epoxy composite plies and woven carbon fabric/epoxy composite plies are studied for fatigue damage and residual strength. A theoretical framework based on the systems approach is proposed as a guide to deal with the complexity involving uncertainties and a large number of variables in the hybrid composite system. A relative damage sensitivity factor expression was developed for quantitative comparisons between non-hybrid and hybrid composites. Hypotheses derived from the theoretical framework were tested and verified. The first hypothesis was that the difference between two different sets of properties produces shear stress in interface between carbon fibre reinforced plastics (CRP) and glass fibre reinforced plastics (GRP), and eventually become a source for CRP/GRP interfacial delamination or longitudinal cracking. The second hypothesis was that inter-fibre bundle delamination occurs more severely to CRP sub-system than GRP sub-system.

  6. Systematic identification of pathological lamin A interactors

    PubMed Central

    Dittmer, Travis A.; Sahni, Nidhi; Kubben, Nard; Hill, David E.; Vidal, Marc; Burgess, Rebecca C.; Roukos, Vassilis; Misteli, Tom

    2014-01-01

    Laminopathies are a collection of phenotypically diverse diseases that include muscular dystrophies, cardiomyopathies, lipodystrophies, and premature aging syndromes. Laminopathies are caused by >300 distinct mutations in the LMNA gene, which encodes the nuclear intermediate filament proteins lamin A and C, two major architectural elements of the mammalian cell nucleus. The genotypephenotype relationship and the basis for the pronounced tissue specificity of laminopathies are poorly understood. Here we seek to identify on a global scale lamin Abinding partners whose interaction is affected by disease-relevant LMNA mutations. In a screen of a human genomewide ORFeome library, we identified and validated 337 lamin Abinding proteins. Testing them against 89 known lamin A disease mutations identified 50 disease-associated interactors. Association of progerin, the lamin A isoform responsible for the premature aging disorder HutchinsonGilford progeria syndrome, with its partners was largely mediated by farnesylation. Mapping of the interaction sites on lamin A identified the immunoglobulin G (IgG)like domain as an interaction hotspot and demonstrated that lamin A variants, which destabilize the Ig-like domain, affect proteinprotein interactions more globally than mutations of surface residues. Analysis of a set of LMNA mutations in a single residue, which result in three phenotypically distinct diseases, identified disease-specific interactors. The results represent a systematic map of disease-relevant lamin A interactors and suggest loss of tissue-specific lamin A interactions as a mechanism for the tissue-specific appearance of laminopathic phenotypes. PMID:24623722

  7. Flat laminated microbial mat communities

    NASA Astrophysics Data System (ADS)

    Franks, Jonathan; Stolz, John F.

    2009-10-01

    Flat laminated microbial mats are complex microbial ecosystems that inhabit a wide range of environments (e.g., caves, iron springs, thermal springs and pools, salt marshes, hypersaline ponds and lagoons, methane and petroleum seeps, sea mounts, deep sea vents, arctic dry valleys). Their community structure is defined by physical (e.g., light quantity and quality, temperature, density and pressure) and chemical (e.g., oxygen, oxidation/reduction potential, salinity, pH, available electron acceptors and donors, chemical species) parameters as well as species interactions. The main primary producers may be photoautotrophs (e.g., cyanobacteria, purple phototrophs, green phototrophs) or chemolithoautophs (e.g., colorless sulfur oxidizing bacteria). Anaerobic phototrophy may predominate in organic rich environments that support high rates of respiration. These communities are dynamic systems exhibiting both spatial and temporal heterogeneity. They are characterized by steep gradients with microenvironments on the submillimeter scale. Diel oscillations in the physical-chemical profile (e.g., oxygen, hydrogen sulfide, pH) and species distribution are typical for phototroph-dominated communities. Flat laminated microbial mats are often sites of robust biogeochemical cycling. In addition to well-established modes of metabolism for phototrophy (oxygenic and non-oxygenic), respiration (both aerobic and anaerobic), and fermentation, novel energetic pathways have been discovered (e.g., nitrate reduction couple to the oxidation of ammonia, sulfur, or arsenite). The application of culture-independent techniques (e.g., 16S rRNA clonal libraries, metagenomics), continue to expand our understanding of species composition and metabolic functions of these complex ecosystems.

  8. Characterization of marine diatom-infecting virus promoters in the model diatom Phaeodactylum tricornutum.

    PubMed

    Kadono, Takashi; Miyagawa-Yamaguchi, Arisa; Kira, Nozomu; Tomaru, Yuji; Okami, Takuma; Yoshimatsu, Takamichi; Hou, Liyuan; Ohama, Takeshi; Fukunaga, Kazunari; Okauchi, Masanori; Yamaguchi, Haruo; Ohnishi, Kohei; Falciatore, Angela; Adachi, Masao

    2015-01-01

    Viruses are considered key players in phytoplankton population control in oceans. However, mechanisms that control viral gene expression in prominent microalgae such as diatoms remain largely unknown. In this study, potential promoter regions isolated from several marine diatom-infecting viruses (DIVs) were linked to the egfp reporter gene and transformed into the Pennales diatom Phaeodactylum tricornutum. We analysed their activity in cells grown under different conditions. Compared to diatom endogenous promoters, novel DIV promoter (ClP1) mediated a significantly higher degree of reporter transcription and translation. Stable expression levels were observed in transformants grown under both light and dark conditions, and high levels of expression were reported in cells in the stationary phase compared to the exponential phase of growth. Conserved motifs in the sequence of DIV promoters were also found. These results allow the identification of novel regulatory regions that drive DIV gene expression and further examinations of the mechanisms that control virus-mediated bloom control in diatoms. Moreover, the identified ClP1 promoter can serve as a novel tool for metabolic engineering of diatoms. This is the first report describing a promoter of DIVs that may be of use in basic and applied diatom research. PMID:26692124

  9. Characterization of marine diatom-infecting virus promoters in the model diatom Phaeodactylum tricornutum

    PubMed Central

    Kadono, Takashi; Miyagawa-Yamaguchi, Arisa; Kira, Nozomu; Tomaru, Yuji; Okami, Takuma; Yoshimatsu, Takamichi; Hou, Liyuan; Ohama, Takeshi; Fukunaga, Kazunari; Okauchi, Masanori; Yamaguchi, Haruo; Ohnishi, Kohei; Falciatore, Angela; Adachi, Masao

    2015-01-01

    Viruses are considered key players in phytoplankton population control in oceans. However, mechanisms that control viral gene expression in prominent microalgae such as diatoms remain largely unknown. In this study, potential promoter regions isolated from several marine diatom-infecting viruses (DIVs) were linked to the egfp reporter gene and transformed into the Pennales diatom Phaeodactylum tricornutum. We analysed their activity in cells grown under different conditions. Compared to diatom endogenous promoters, novel DIV promoter (ClP1) mediated a significantly higher degree of reporter transcription and translation. Stable expression levels were observed in transformants grown under both light and dark conditions, and high levels of expression were reported in cells in the stationary phase compared to the exponential phase of growth. Conserved motifs in the sequence of DIV promoters were also found. These results allow the identification of novel regulatory regions that drive DIV gene expression and further examinations of the mechanisms that control virus-mediated bloom control in diatoms. Moreover, the identified ClP1 promoter can serve as a novel tool for metabolic engineering of diatoms. This is the first report describing a promoter of DIVs that may be of use in basic and applied diatom research. PMID:26692124

  10. Severe laminitis in multiple zoo species.

    PubMed

    Wiedner, Ellen; Holland, Jeff; Trupkiewicz, John; Uzal, Francisco

    2014-01-01

    A 10-year record review from a zoological institution in the western USA identified four cases of severe laminitis resulting in rotation and protrusion of the third phalanx through the sole. Laminitis is reported in a Masai giraffe (Giraffa camelopardalis tippelskirchi), a Sichuan takin (Budorcas taxicolor tibetana), a greater Malayan chevrotain (Tragulus napu) and a giant eland (Taurotragus derbianus). This is the first report of severe laminitis with pedal bone rotation and protrusion in multiple species of non-domestic hoofstock, and the first report of this disease in three of these species (takin, chevrotain, and giant eland). PMID:24730432

  11. Free Vibration of Symmetrically Laminated Skew Plates

    NASA Astrophysics Data System (ADS)

    Han, W.; Dickinson, S. M.

    1997-12-01

    A Ritz approach, developed for the analysis of the vibration of thin, laminated, rectangular plates, is extended to apply to symmetrically laminated, composite, skew plates. There is relatively little information available on the vibration of such skew plates, despite their increasing use in the aerospace industry. A convergence study and comparisons with results available from the literature indicate that the approach presented is reliable and accurate. A fairly extensive set of numerical results is given in graphical form, illustrating the influence of different lamination lay-ups, skew angles and edge conditions on the natural frequencies and nodal patterns of a selection of plates.

  12. Probabilistic methods for the calculation of laminate properties

    SciTech Connect

    Mcmanus, H.L. )

    1993-06-01

    A method for calculating the properties of advanced composite laminates, including their variations due to known variations in the properties of the individual plies and the laminate geometry, is presented. The method is useful for understanding scatter in the measured properties of composite laminates. This scatter is particularly important in the design of ultra-low coefficient of thermal expansion (CTE) laminates. Such laminates are designed with a theoretically zero CTE, but in practice have a distribution of nonzero CTEs. Information useful for designing ultra-low expansion laminates is discussed. A practical limit on how close to zero the CTE of a laminate can be assumed to be is found. 10 refs.

  13. From diatoms to silica-based biohybrids.

    PubMed

    Nassif, Nadine; Livage, Jacques

    2011-02-01

    This critical review shows that diatoms can be a source of inspiration for the synthesis of advanced nanostructured biohybrids. These single cell microalgae are living inside a porous silica shell called 'frustule'. Mimicking this model, silica-based biohybrids have been produced via the so-called sol-gel process. Biomolecules such as proteins, enzymes or antibodies can be trapped within a silica matrix leading to hybrid biosensors and bioreactors. Whole cells remain viable and retain their metabolic activity leading to the formation of living biohybrids that offer new possibilities in the field of biotechnology and nanomedicine. Diatom frustules exhibit an incredible variety of sophisticated shapes; they can be used as 3D hierarchically structured materials for the realization of sensors, photonic devices or microfluidics. They can also be a model for the bio-templated synthesis of nanostructured materials. Diatom nanotechnology is becoming a new field of research where biologists and materials scientists are working together! (125 references). PMID:21173981

  14. 70 Ma nonmarine diatoms from northern Mexico

    NASA Astrophysics Data System (ADS)

    Chacn-Baca, Elizabeth; Beraldi-Campesi, H.; Cevallos-Ferriz, S. R. S.; Knoll, A. H.; Golubic, S.

    2002-03-01

    Carbonaceous cherts of the Tarahumara Formation, exposed near Huepac, Sonora, Mexico, contain abundant diatom frustules occurring as benthic filamentous colonies. Stratigraphic and paleontological observations indicate that Tarahumara sediments accumulated in a nonmarine setting; radiometric ages on encompassing volcanic rocks delimit their depositional age to ca. 70 Ma. Tarahumara fossils therefore extend the paleontological record of nonmarine diatoms from middle Eocene to Late Cretaceous. Preserved populations include forms similar to species of the extant genera Amphora and Melosira, as well as filament-forming araphid pennates comparable to species of Fragilaria and Tabellaria. Tarahumara fossils indicate that by 70 Ma, nonmarine diatoms had achieved considerable environmental as well as taxonomic diversity.

  15. A Capillarity Mechanism for Diatom Gliding Locomotion

    PubMed Central

    Gordon, Richard; Drum, Ryan W.

    1970-01-01

    It is proposed that the diatom raphe is a parallel-plate capillary containing a fluid which reacts at the trailing end, turning into a form which no longer wets the raphe walls, and which is left behind as a trail. More unreacted raphe fluid is drawn by capillary pressure from a source near the leading end of the raphe. This fluid sticks out from the raphe along its length, adhering to surfaces, thus causing gliding locomotion. Formulae are given for the maximum velocity and force of a moving diatom in terms of the raphe dimensions and the surface tension and viscosity of the fluid. An a priori estimate of the force exerted by a moving diatom, 1-50 millidynes, agrees with measured values. Five experimental tests of the theory are proposed. PMID:16591861

  16. Diatoms: a fossil fuel of the future.

    PubMed

    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. PMID:24529448

  17. Designer diatom episomes delivered by bacterial conjugation

    PubMed Central

    Karas, Bogumil J.; Diner, Rachel E.; Lefebvre, Stephane C.; McQuaid, Jeff; Phillips, Alex P.R.; Noddings, Chari M.; Brunson, John K.; Valas, Ruben E.; Deerinck, Thomas J.; Jablanovic, Jelena; Gillard, Jeroen T.F.; Beeri, Karen; Ellisman, Mark H.; Glass, John I.; Hutchison III, Clyde A.; Smith, Hamilton O.; Venter, J. Craig; Allen, Andrew E.; Dupont, Christopher L.; Weyman, Philip D.

    2015-01-01

    Eukaryotic microalgae hold great promise for the bioproduction of fuels and higher value chemicals. However, compared with model genetic organisms such as Escherichia coli and Saccharomyces cerevisiae, characterization of the complex biology and biochemistry of algae and strain improvement has been hampered by the inefficient genetic tools. To date, many algal species are transformable only via particle bombardment, and the introduced DNA is integrated randomly into the nuclear genome. Here we describe the first nuclear episomal vector for diatoms and a plasmid delivery method via conjugation from Escherichia coli to the diatoms Phaeodactylum tricornutum and Thalassiosira pseudonana. We identify a yeast-derived sequence that enables stable episome replication in these diatoms even in the absence of antibiotic selection and show that episomes are maintained as closed circles at copy number equivalent to native chromosomes. This highly efficient genetic system facilitates high-throughput functional characterization of algal genes and accelerates molecular phytoplankton research. PMID:25897682

  18. Designer diatom episomes delivered by bacterial conjugation.

    PubMed

    Karas, Bogumil J; Diner, Rachel E; Lefebvre, Stephane C; McQuaid, Jeff; Phillips, Alex P R; Noddings, Chari M; Brunson, John K; Valas, Ruben E; Deerinck, Thomas J; Jablanovic, Jelena; Gillard, Jeroen T F; Beeri, Karen; Ellisman, Mark H; Glass, John I; Hutchison, Clyde A; Smith, Hamilton O; Venter, J Craig; Allen, Andrew E; Dupont, Christopher L; Weyman, Philip D

    2015-01-01

    Eukaryotic microalgae hold great promise for the bioproduction of fuels and higher value chemicals. However, compared with model genetic organisms such as Escherichia coli and Saccharomyces cerevisiae, characterization of the complex biology and biochemistry of algae and strain improvement has been hampered by the inefficient genetic tools. To date, many algal species are transformable only via particle bombardment, and the introduced DNA is integrated randomly into the nuclear genome. Here we describe the first nuclear episomal vector for diatoms and a plasmid delivery method via conjugation from Escherichia coli to the diatoms Phaeodactylum tricornutum and Thalassiosira pseudonana. We identify a yeast-derived sequence that enables stable episome replication in these diatoms even in the absence of antibiotic selection and show that episomes are maintained as closed circles at copy number equivalent to native chromosomes. This highly efficient genetic system facilitates high-throughput functional characterization of algal genes and accelerates molecular phytoplankton research. PMID:25897682

  19. Energy Transfer in Diatom/diatom Molecular Collisions

    NASA Astrophysics Data System (ADS)

    Sohlberg, Karl William

    By utilizing the tools of molecular scattering theory we are striving to uncover the fundamental mechanisms of energy transfer in molecular collisions. In a collision of two molecules, the translational energy of the collision may be redistributed into internal energy of rotation, vibration, or electronic motion, in one or both of the colliding partners. In addition, internal energy in one or more of these modes may be "quenched" 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, we have investigated vibrational energy transfer in collisions between two diatomic molecules. In addition to serving as models for all molecular collision processes, gas phase collisions of these species, (N_2, O_2, CO, NO, and so forth) are ubiquitous in atmospheric phenomena which are of critical importance in answering the current questions about the human induced degradation of the earth's atmosphere. 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, even. In order to obtain precise state-to-state specific information about a scattering process, quantum methods must, of course, be used. Quantum scattering techniques have also been applied to the above mentioned problem but without complete success. The strong interaction potential and the dramatic classical nature of the N_sp {2}{+} + N_2 system make it very difficult to treat quantum mechanically.

  20. AN ELEMENTARY MATHEMATICAL PROBLEM ARISING IN DIATOM TAXONOMY

    EPA Science Inventory

    This paper involves a problem confronted by the working diatom taxonomist who must make some basic observations and measurements of the diatom cell wall to achieve an accurate identification. the identification of diatoms to the species level is possible by microscopic observatio...

  1. Free edge effects in laminated composites

    NASA Technical Reports Server (NTRS)

    Herakovich, C. T.

    1989-01-01

    The fundamental mechanics of free-edge effects in laminated fiber-reinforced composites is examined, reviewing the results of recent experimental and analytical investigations. The derivation of the governing equations for the basic problem is outlined, including the equilibrium and mismatch conditions and the elasticity formulation, and experimental data on axial displacement and shear strain in angle-ply laminates are summarized. Numerical predictions of free-edge deformation and interlaminar and through-thickness stress distributions are presented for cross-ply, angle-ply, and quasi-isotropic laminates, and the mechanisms of edge damage and failure in angle-ply laminates are briefly characterized. Extensive diagrams, drawings, graphs, and photographs are provided.

  2. Behaviour of Mechanically Laminated CLT Members

    NASA Astrophysics Data System (ADS)

    Kuklík, P.; Velebil, L.

    2015-11-01

    Cross laminated timber (CLT) is one of the structural building systems based on the lamination of multiple layers, where each layer is oriented perpendicularly to each other. Recent requirements are placed to develop an alternative process based on the mechanical lamination of the layers, which is of particular interest to our research group at the University Centre for Energy Efficient Buildings. The goal is to develop and verify the behaviour of mechanically laminated CLT wall panels exposed to shear stresses in the plane. The shear resistance of mechanically jointed CLT is ensured by connecting the layers by screws. The paper deals with the experimental analysis focused on the determination of the torsional stiffness and the slip modulus of crossing areas for different numbers of orthogonally connected layers. The results of the experiments were compared with the current analytical model.

  3. Vacuum-and-pressure laminating polymer materials

    NASA Technical Reports Server (NTRS)

    Hoffman, D. R.; Riley, T. J.

    1980-01-01

    Lamination setup is used to produce void-free bonds by first employing vacuum to outgas materials and adhesive at temperature below curing temperature and then subjecting assembly to pressure and temperature necessary to cure.

  4. Fatigue crack growth in aluminum laminate composites

    SciTech Connect

    Hoffman, P.B.; Carpenter, R.D.; Gibeling, J.C.

    1996-12-31

    Fatigue crack growth has been measured in a laminated metal composite (LMC) consisting of alternating layers of AA6090/SiC/25p metal matrix composite (MMC) and AA5182 alloy. This material was tested in both as-pressed (F temper) and aged (T6 temper) conditions. Corresponding crack growth measurements were made in self-laminates of both the MMC and AA5182 materials to examine the role of the interfaces.

  5. Oxylipin Diversity in the Diatom Family Leptocylindraceae Reveals DHA Derivatives in Marine Diatoms

    PubMed Central

    Nanjappa, Deepak; dIppolito, Giuliana; Gallo, Carmela; Zingone, Adriana; Fontana, Angelo

    2014-01-01

    Marine planktonic organisms, such as diatoms, are prospective sources of novel bioactive metabolites. Oxygenated derivatives of fatty acids, generally referred to as oxylipins, in diatoms comprise a highly diverse and complex family of secondary metabolites. These molecules have recently been implicated in several biological processes including intra- and inter-cellular signaling as well as in defense against biotic stressors and grazers. Here, we analyze the production and diversity of C20 and C22 non-volatile oxylipins in five species of the family Leptocylindraceae, which constitute a basal clade in the diatom phylogeny. We report the presence of species-specific lipoxygenase activity and oxylipin patterns, providing the first demonstration of enzymatic production of docosahexaenoic acid derivatives in marine diatoms. The differences observed in lipoxygenase pathways among the species investigated broadly reflected the relationships observed with phylogenetic markers, thus providing functional support to the taxonomic diversity of the individual species. PMID:24445306

  6. Oxylipin diversity in the diatom family Leptocylindraceae reveals DHA derivatives in marine diatoms.

    PubMed

    Nanjappa, Deepak; d'Ippolito, Giuliana; Gallo, Carmela; Zingone, Adriana; Fontana, Angelo

    2014-01-01

    Marine planktonic organisms, such as diatoms, are prospective sources of novel bioactive metabolites. Oxygenated derivatives of fatty acids, generally referred to as oxylipins, in diatoms comprise a highly diverse and complex family of secondary metabolites. These molecules have recently been implicated in several biological processes including intra- and inter-cellular signaling as well as in defense against biotic stressors and grazers. Here, we analyze the production and diversity of C20 and C22 non-volatile oxylipins in five species of the family Leptocylindraceae, which constitute a basal clade in the diatom phylogeny. We report the presence of species-specific lipoxygenase activity and oxylipin patterns, providing the first demonstration of enzymatic production of docosahexaenoic acid derivatives in marine diatoms. The differences observed in lipoxygenase pathways among the species investigated broadly reflected the relationships observed with phylogenetic markers, thus providing functional support to the taxonomic diversity of the individual species. PMID:24445306

  7. A Live Bioprobe for Studying Diatom-Surface Interactions

    PubMed Central

    Arce, Fernando Tern; Avci, Recep; Beech, Iwona B.; Cooksey, Keith E.; Wigglesworth-Cooksey, Barbara

    2004-01-01

    Atomic force microscopy has been employed to compare the adhesion of Navicula species I diatoms to surfaces of a hydrophobic elastomer, Intersleek, and a hydrophilic mineral, mica. This was accomplished using tipless atomic force microscopy cantilevers functionalized with live diatom cells. Both surfaces were tested with the same diatom bioprobe. Force versus distance curves generated during these experiments revealed comparable cell adhesion strengths on Intersleek and mica, indicating that Navicula diatoms secrete extracellular polymeric substances with hydrophobic and hydrophilic properties. A statistical analysis of force curves was carried out and the average values of works of detachment of a diatom from Intersleek and mica surfaces were determined. PMID:15377513

  8. Laminopathy-inducing lamin A mutants can induce redistribution of lamin binding proteins into nuclear aggregates

    SciTech Connect

    Huebner, S. . E-mail: stefan.huebner@med.monash.edu.au; Eam, J.E.; Huebner, A.; Jans, D.A.

    2006-01-15

    Lamins, members of the family of intermediate filaments, form a supportive nucleoskeletal structure underlying the nuclear envelope and can also form intranuclear structures. Mutations within the A-type lamin gene cause a variety of degenerative diseases which are collectively referred to as laminopathies. At the molecular level, laminopathies have been shown to be linked to a discontinuous localization pattern of A-type lamins, with some laminopathies containing nuclear lamin A aggregates. Since nuclear aggregate formation could lead to the mislocalization of proteins interacting with A-type lamins, we set out to examine the effects of FLAG-lamin A N195K and R386K protein aggregate formation on the subnuclear distribution of the retinoblastoma protein (pRb) and the sterol responsive element binding protein 1a (SREBP1a) after coexpression as GFP-fusion proteins in HeLa cells. We observed strong recruitment of both proteins into nuclear aggregates. Nuclear aggregate recruitment of the NPC component nucleoporin NUP153 was also observed and found to be dependent on the N-terminus. That these effects were specific was implied by the fact that a number of other coexpressed karyophilic GFP-fusion proteins, such as the nucleoporin NUP98 and kanadaptin, did not coaggregate with FLAG-lamin A N195K or R386K. Immunofluorescence analysis further indicated that the precursor form of lamin A, pre-lamin A, could be found in intranuclear aggregates. Our results imply that redistribution into lamin A-/pre-lamin A-containing aggregates of proteins such as pRb and SREBP1a could represent a key aspect underlying the molecular pathogenesis of certain laminopathies.

  9. Selective silicate-directed motility in diatoms

    PubMed Central

    Bondoc, Karen Grace V.; Heuschele, Jan; Gillard, Jeroen; Vyverman, Wim; Pohnert, Georg

    2016-01-01

    Diatoms are highly abundant unicellular algae that often dominate pelagic as well as benthic primary production in the oceans and inland waters. Being strictly dependent on silica to build their biomineralized cell walls, marine diatoms precipitate 240 × 1012 mol Si per year, which makes them 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 dSi-limited conditions in a chemokinetic response and, if gradients of this resource are present, increased directionality of cell movement promotes chemotaxis. The ability to exploit local and short-lived dSi hotspots using a specific search behaviour likely contributes to micro-scale patch dynamics in biofilm communities. On a global scale this behaviour might affect sediment–water dSi fluxes and biogeochemical cycling. PMID:26842428

  10. Seasonal fluctuations of Lake Michigan diatoms

    USGS Publications Warehouse

    Holland, Ruth E.

    1969-01-01

    Diatoms were collected in four areas of Lake Michigan and in southern Green Bay from April to early November 1965. The flora of the lake was characterized by Fragilaria crotonensis, Tabellaria flocculosa, Melosira islandica, Cyclotella 'glomerata-stelligera,' Cyclotella michiganiana, Asterionella formosa, and Stephanodiscus tenuis. Stephanodiscus niagarae always dominated the diatom biomass in Green Bay; also characteristic of the bay were Melosira granulata, Melosira ambigua, Melosira binderana, Fragilaria capucina, and Fragilaria crotonensis. There was an average of 517 diatoms per ml in the lake and 944 in the bay. Diatom abundance appeared to have one peak in the lake and two in the bay. At times of maximum abundance, optimum depth was usually 5 m. Numbers were greater in Green Bay and the inshore areas than in the offshore areas and appreciably higher near the eastern shore than the western shore of the lake. The higher populations near the eastern shore and in Green Bay appeared to be correlated with higher concentrations of phosphorus and chlorophyll a and lower concentrations of nitrate-N.

  11. Selective silicate-directed motility in diatoms.

    PubMed

    Bondoc, Karen Grace V; Heuschele, Jan; Gillard, Jeroen; Vyverman, Wim; Pohnert, Georg

    2016-01-01

    Diatoms are highly abundant unicellular algae that often dominate pelagic as well as benthic primary production in the oceans and inland waters. Being strictly dependent on silica to build their biomineralized cell walls, marine diatoms precipitate 240 × 10(12) mol Si per year, which makes them 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 dSi-limited conditions in a chemokinetic response and, if gradients of this resource are present, increased directionality of cell movement promotes chemotaxis. The ability to exploit local and short-lived dSi hotspots using a specific search behaviour likely contributes to micro-scale patch dynamics in biofilm communities. On a global scale this behaviour might affect sediment-water dSi fluxes and biogeochemical cycling. PMID:26842428

  12. Effect of laminate edge conditions on the formation of microvoids in composite laminates

    NASA Astrophysics Data System (ADS)

    Anderson, J. P.; Altan, M. C.

    2015-05-01

    Manufacturing defects such as microvoids are common in thermoset composite components and are known to negatively affect their strength. The resin pressure developed in and the resin flow out from the laminates during cure have been reported to be the primary factors influencing the final void content of a composite component. In this work, the effect of laminate edge conditions during the cure process on the formation of microvoids was experimentally investigated. This was achieved by fabricating eight-ply laminates from TenCate BT250/7781 prepreg in a hot-press at a constant cure pressure of 170 kPa while limiting the laminate perimeter available for resin flow by 0%, 25%, 50%, 75%, and 100%. The individual plies of these five laminates were conditioned at 99% relative humidity before curing to maximize the moisture present in the lay-up before fabrication. The presence of moisture in the lay-ups was expected to promote void formation and allow the effect of restricting flow at the edges of a laminate to be better identified. The restriction of resin outflow was found to cause the average characteristic void diameter to decrease by 17% and void content to rise by 33%. This phenomenon was identified to be a result of the outflow restriction increasing the number of voids trapped within the laminate and indicates that for laminates cured at low pressures resin outflow is the dominant mechanism for void reduction.

  13. 78 FR 13083 - Products Having Laminated Packaging, Laminated Packaging, and Components Thereof; Notice of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-26

    ...Notice is hereby given that the U.S. International Trade Commission has received a complaint entitled Products Having Laminated Packaging, Laminated Packaging, and Components Thereof, DN 2940; the Commission is soliciting comments on any public interest issues raised by the complaint or complainant's filing under section 210.8(b) of the Commission's Rules of Practice and Procedure (19 CFR......

  14. Ultimate strength of composite laminates with free-edge delamination

    NASA Astrophysics Data System (ADS)

    Onohara, Kaoru; Kunoo, Kazuo; Ono, Kousei

    1993-06-01

    This paper presents experimental and analytical studies of ultimate strength of (30(2)/-30(2)/90)(s) carbon/epoxy laminates with free-edge delamination under uniaxial tension. We performed tensile tests for laminates with Telflon inserted on interfaces to simulate initial free-edge delamination. The experiment reveals that extensional stiffness of the laminate decreases by the initiation of the delamination, and that strength of the laminate without delamination is smaller than that of the laminates with delamination. Generalized quasi-3D finite element analysis, which employs energy release rate and maximum stress criteria, predicts the ultimate strength of the laminates with sufficient accuracy.

  15. Lamination residual stresses in fiber composites

    NASA Technical Reports Server (NTRS)

    Daniel, I. M.; Liber, T.

    1975-01-01

    An experimental investigation was conducted to determine the magnitude of lamination residual stresses in angle-ply composites and to evaluate their effects on composite structural integrity. The materials investigated were boron/epoxy, boron/polyimide, graphite/low modulus epoxy, graphite/high modulus epoxy, graphite/polyimide and s-glass/epoxy. These materials were fully characterized. Static properties of laminates were also determined. Experimental techniques using embedded strain gages were developed and used to measure residual strains during curing. The extent of relaxation of lamination residual stresses was investigated. It was concluded that the degree of such relaxation is low. The behavior of angle-ply laminates subjected to thermal cycling, tensile load cycling, and combined thermal cycling with tensile load was investigated. In most cases these cycling programs did not have any measurable influence on residual strength and stiffness of the laminates. In the tensile load cycling tests, the graphite/polyimide shows the highest endurance with 10 million cycle runouts at loads up to 90 percent of the static strength.

  16. Mechanical Behavior of Fabric-Film Laminates

    NASA Technical Reports Server (NTRS)

    Said, Magdi S.

    1999-01-01

    Inflatable structures are gaining wide support in planetary scientific missions as well as commercial applications. For such applications a new class of materials made of laminating thin homogenous films to lightweight fabrics are being considered us structura1 gas envelops. The emerging composite materials are a result of recent advances in the manufacturing cf 1ightweight, high strength fibers, fabrics and scrims. The lamination of these load-carrying members with the proper gas barrier film results in wide range of materials suitable for various loading and environmental conditions. Polyester - based woven fabrics laminated to thin homogeneus film of polyester (Maylar) is an example of this class. This fabric/ film laminate is being considered for the development a material suitable for building large gas envelopes for use in the NASA Ultra Long Duration Balloon Program (ULDB). Compared to commercial homogeneus films, the material provides relatively high strength to weight ratio as well as better resistance to crack and tear propagation. The purpose of this papers is to introduce the mechanical behavior of this class of multi-layers composite and to highlight some of the concerns observed during the characterization of these laminate composites.

  17. Evaluation of Behaviours of Laminated Glass

    NASA Astrophysics Data System (ADS)

    Sable, L.; Japins, G.; Kalnins, K.

    2015-11-01

    Visual appearance of building facades and other load bearing structures, which now are part of modern architecture, is the reason why it is important to investigate in more detail the reliability of laminated glass for civil structures. Laminated glass in particular has become one of the trendy materials, for example Apple© stores have both load carrying capacity and transparent appearance. Glass has high mechanical strength and relatively medium density, however, the risk of sudden brittle failure like concrete or other ceramics determine relatively high conservatism in design practice of glass structures. This should be changed as consumer requirements evolve calling for a safe and reliable design methodology and corresponding building standards. A design methodology for glass and glass laminates should be urgently developed and included as a chapter in Eurocode. This paper presents initial experimental investigation of behaviour of simple glass sheets and laminated glass samples in 4-point bending test. The aim of the current research is to investigate laminated glass characteristic values and to verify the obtained experimental results with finite element method for glass and EVA material in line with future European Structural Design of Glass Components code.

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

    PubMed

    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. PMID:22720636

  19. Silicone modified resins for graphite fiber laminates

    NASA Technical Reports Server (NTRS)

    Frost, L. W.; Bower, G. M.

    1979-01-01

    The development of silicon modified resins for graphite fiber laminates which will prevent the dispersal of graphite fibers when the composites are burned is discussed. Eighty-five silicone modified resins were synthesized and evaluated including unsaturated polyesters, thermosetting methacrylates, epoxies, polyimides, and phenolics. Neat resins were judged in terms of Si content, homogeneity, hardness, Char formation, and thermal stability. Char formation was estimated by thermogravimetry to 1,000 C in air and in N2. Thermal stability was evaluated by isothermal weight loss measurements for 200 hrs in air at three temperatures. Four silicone modified epoxies were selected for evaluation in unidirectional filament wound graphite laminates. Neat samples of these resins had 1,000 C char residues of 25 to 50%. The highest flexural values measured for the laminates were a strength of 140 kpsi and a modulus of 10 Mpsi. The highest interlaminar shear strength was 5.3 kpsi.

  20. Damage initiation and propagation in metal laminates

    SciTech Connect

    Riddle, R.A.; Lesuer, D.R.; Syn, C.K.

    1996-07-26

    The metal laminates proposed here for aircraft structures are Al alloy interlayers between Al alloy based metal matrix composite (MMC) plates reinforced with Si carbide particles. Properties to be tailored for jet engine fan containment and wing and auxiliary support structures include the important property fracture toughness. A method was developed for simulating and predicting crack initiation/growth using finite element analysis and fracture mechanics. An important key in predicting the failure is the tie- break slideline with prescribed (chosen based on J Integral calculations) effective plastic strain to failure in elements along the slideline. More development of the method is needed, particularly in its correlation with experimental data from various fracture toughness and strength tests of metal laminates. Results show that delamination at the interface of the ductile interlayer and MMC material can add significantly to the energy required to propagate a crack through a metal laminate. 11 figs, 7 refs.

  1. Development of tough, moisture resistant laminating resins

    NASA Technical Reports Server (NTRS)

    Brand, R. A.; Harrison, E. S.

    1982-01-01

    Tough, moisture resistant laminating resins for employment with graphite fibers were developed. The new laminating resins exhibited cost, handleability and processing characteristics equivalent to 394K (250 F) curing epoxies. The laminating resins were based on bisphenol A dicyanate and monofunctional cyanates with hydrophobic substituents. These resins sorb only small quantities of moisture at equilibrium (0.5% or less) with minimal glass transition temperature depression and represent an improvement over epoxies which sorb around 2% moisture at equilibrium. Toughening was accomplished by the precipitation of small diameter particles of butadiene nitrile rubber throughout the resin matrix. The rubber domains act as microcrack termini and energy dissipation sites, allowing increased stress accommodation prior to catastrophic failure. A unique blend of amine terminated butadiene nitrile elastomer (MW 2,000) and a high nitrile content butadiene nitrile rubber yielded the desired resin morphology.

  2. Structural reliability analysis of laminated CMC components

    NASA Technical Reports Server (NTRS)

    Duffy, Stephen F.; Palko, Joseph L.; Gyekenyesi, John P.

    1991-01-01

    For laminated ceramic matrix composite (CMC) materials to realize their full potential in aerospace applications, design methods and protocols are a necessity. The time independent failure response of these materials is focussed on and a reliability analysis is presented associated with the initiation of matrix cracking. A public domain computer algorithm is highlighted that was coupled with the laminate analysis of a finite element code and which serves as a design aid to analyze structural components made from laminated CMC materials. Issues relevant to the effect of the size of the component are discussed, and a parameter estimation procedure is presented. The estimation procedure allows three parameters to be calculated from a failure population that has an underlying Weibull distribution.

  3. Plated lamination structures for integrated magnetic devices

    SciTech Connect

    Webb, Bucknell C.

    2014-06-17

    Semiconductor integrated magnetic devices such as inductors, transformers, etc., having laminated magnetic-insulator stack structures are provided, wherein the laminated magnetic-insulator stack structures are formed using electroplating techniques. For example, an integrated laminated magnetic device includes a multilayer stack structure having alternating magnetic and insulating layers formed on a substrate, wherein each magnetic layer in the multilayer stack structure is separated from another magnetic layer in the multilayer stack structure by an insulating layer, and a local shorting structure to electrically connect each magnetic layer in the multilayer stack structure to an underlying magnetic layer in the multilayer stack structure to facilitate electroplating of the magnetic layers using an underlying conductive layer (magnetic or seed layer) in the stack as an electrical cathode/anode for each electroplated magnetic layer in the stack structure.

  4. Flutter of laminated plates in supersonic flow

    NASA Technical Reports Server (NTRS)

    Sawyer, J. W.

    1975-01-01

    A solution procedure was developed using linear small deflection theory for the flutter of simply supported laminated plates. For such plates, the bending and extensional governing equations are coupled and have cross-stiffness terms which do not appear in classical plate theory. An extended Galerkin method is used to obtain approximate solutions to the governing equations, and the aerodynamic pressure loading used in the analysis is that given by linear piston theory with flow at arbitrary cross-flow angle. A limited parametric study was conducted for typical laminated composite plates. The calculations show that both the bending-extensional coupling and the cross-stiffness terms have a large destabilizing effect on flutter. Since classical plate theory does not consider bending-extensional coupling and cross stiffness terms, it usually gives inaccurate and nonconservative flutter boundaries for laminated plates.

  5. Preliminary evaluation of hybrid titanium composite laminates

    NASA Technical Reports Server (NTRS)

    Miller, J. L.; Progar, D. J.; Johnson, W. S.; St.clair, T. L.

    1994-01-01

    In this study, the mechanical response of hybrid titanium composite laminates (HTCL) was evaluated at room and elevated temperatures. Also, the use of an elastic-plastic laminate analysis program for predicting the tensile response from constituent properties was verified. The improvement in mechanical properties achieved by the laminates was assessed by comparing the results of static strength and constant amplitude fatigue tests to those for monolithic titanium sheet. Two HTCL were fabricated with different fiber volume fractions, resin layer thicknesses, and resins. One panel was thicker and was more poorly bonded in comparison to other. Consequently, the former had a lower tensile strength, while fewer cracks grew in this panel and at a slower rate. Both panels showed an improvement in fatigue life of almost two orders of magnitude. The model predictions were also in good agreement with the experimental results for both HTCL panels.

  6. Stochastic damage evolution in textile laminates

    NASA Technical Reports Server (NTRS)

    Dzenis, Yuris A.; Bogdanovich, Alexander E.; Pastore, Christopher M.

    1993-01-01

    A probabilistic model utilizing random material characteristics to predict damage evolution in textile laminates is presented. Model is based on a division of each ply into two sublaminas consisting of cells. The probability of cell failure is calculated using stochastic function theory and maximal strain failure criterion. Three modes of failure, i.e. fiber breakage, matrix failure in transverse direction, as well as matrix or interface shear cracking, are taken into account. Computed failure probabilities are utilized in reducing cell stiffness based on the mesovolume concept. A numerical algorithm is developed predicting the damage evolution and deformation history of textile laminates. Effect of scatter of fiber orientation on cell properties is discussed. Weave influence on damage accumulation is illustrated with the help of an example of a Kevlar/epoxy laminate.

  7. Adhesives for laminating polyimide insulated flat conductor cable

    NASA Technical Reports Server (NTRS)

    Montermoso, J. C.; Saxton, T. R.; Taylor, R. L.

    1967-01-01

    Polymer adhesive laminates polyimide-film flat conductor cable. It is obtained by reacting an appropriate diamine with a dianhydride. The adhesive has also been used in the lamination of copper to copper for the preparation of multilayer circuit boards.

  8. Can hydrodynamics change phosphorus strategies of diatoms?-Nutrient levels and diatom blooms in lotic and lentic ecosystems.

    PubMed

    Wang, Peili; Shen, Hong; Xie, Ping

    2012-02-01

    Diatom blooms occur in many water bodies worldwide, causing significant ecological and social concerns. In order to understand the mechanisms of diatom blooms formation, the effects of varying phosphorus (P) concentration and hydrodynamics on the growth of diatoms were studied by combining results from field observations and laboratory experiments. The field investigation showed that spring diatom blooms (Cyclotella meneghiniana and Stephanodiscus hantzschii) occurred in Lake Taihu and Hanjiang River with similar environmental factors such as water temperature, pH, and dissolved oxygen in 2008. Concentrations of total phosphorus (TP), total nitrogen, and ammonia nitrogen (NH(4)-N) in Lake Taihu were significantly higher than the concentrations in the Hanjiang River. Laboratory experiments were conducted to evaluate growth and physiological responses of four lotic diatoms (Cyclotella atomus, Fragilaria crotonensis, Nitzschia palea, and S. hantzschii, isolated from the Hanjiang River) and three lentic diatoms (C. meneghiniana, Melosira varians, and Stephanodiscus minutulus, isolated from Lake Taihu, Lake Donghu, and Guanqiao Pond, respectively) to various P concentrations under small-scale turbulent and standing conditions. Our results showed that, with turbulence, lotic diatoms C. atomus, F. crotonensis, N. palea, and S. hantzschii demonstrated a significant increase in affinity for P compared with lentic diatoms C. meneghiniana, M. varians, and S. minutulus. Moreover, lotic diatoms C. atomus, F. crotonensis, and N. palea had higher growth rates and photosynthetic efficiencies with small-scale turbulence than with standing conditions both in P-limited and P-replete conditions. Lotic species S. hantzschii and three lentic diatoms (C. meneghiniana, M. varians, and S. minutulus) grew well under standing conditions. Our results may explain our field observation that the occurrence of diatom blooms in lakes is often associated with higher TP concentrations whereas in rivers, diatom blooms occur at a wide range of TP concentrations under flows. Therefore, different hydrodynamics and nutrient concentrations determined the dominant diatom species, according to their habitat-dependent physiological characteristics. PMID:21811794

  9. Hylleraas hydride binding energy: diatomic electron affinities.

    PubMed

    Chen, Edward S; Keith, Herman; Lim, Tristan; Pham, Dang; Rosenthal, Reece; Herder, Charles; Pai, Sunil; Flores, R A; Chen, Edward C M

    2015-04-01

    Theoretical adiabatic electron affinities are often considered inaccurate because they are referenced to only a single value. Ground state electron affinities for all the main group elements and homonuclear diatomics were identified recently using the normalized binding energy of the hydrogen atom: [0.75420375(3)/2?=?0.37710187(1) eV]. Here we revisit experimental values and extend the identifications to diatomics in the G2-1 set. We assign new ground state electron affinities: (eV) Cl2, 3.2(2); Br2, 2.87(14); CH, 2.1(2); H2, 0.6 ; NH, 1.1, SiH, 1.90. Anion Morse potentials are calculated for H2 and N2 from positive electron affinities and for hyperfine superoxide states for the first time. PMID:25758340

  10. A 5 Ma ocean history of the Bering Sea, observed through diatoms

    NASA Astrophysics Data System (ADS)

    Stroynowski, Z.; Ravelo, C.; Caissie, B.

    2011-12-01

    Until now, a paucity of marine records from the arctic and subarctic North Pacific has hindered a complete evaluation of the Pacific's role in abrupt climate events. The Bering Sea is a marginal sea in the North Pacific that has experienced, and is sensitive to, major climatic change. Although only insignificant amounts of North Pacific Intermediate Water (NPIW) forms in the Bering Sea today, the basin not only records, but is potentially involved in causing major climate changes. In 2009, IODP Exp. 323 recovered continuous cores from the Bering Sea extending back into the Pliocene. Diatoms are the dominant microfossil group in this region and reveal major ecological shifts throughout the 5 Ma record. Here we present fossil diatom abundance and assemblage records from core U1340A. The onset of Northern Hemisphere Glaciation is clearly depicted by a shift from warm, nutrient-rich, shade flora species Coscinodiscus marginatus and Lioloma pacificum, to the appearance of sea-ice species at ca. 2.65 Ma. Also at this time, Actinocyclus sp. appears and dominates the assemblage until the present during intergalcial periods. This species is correlated with low nutrient, stratified waters and suggests a reduction in nutrient availability in the subsurface waters. Increasing 15N of bulk organic matter values supports the idea that nutrients were less available and more fully utilized. Neodenticula sp., a species transported by the Alaskan Stream, has a strong presence during interglacial intervals and reflects ice-free open waters at the site. The overall decreasing trend of Neodenticula sp., particularly after 1.0 Ma until the Present, highlights increasing winter sea ice cover (glacial intensification) in the Bering Sea in line with the switch to 100 Ka cycles. A Uk'37-based SST record from this site, indicates about 7 degree C of cooling, in agreement with the idea that the flow of relatively warm Alaskan Stream water decreased since 5 Ma. Laminated sections in core 323-U1340 permit, for the first time, insight into Pliocene diatom seasonal dynamics. High resolution analysis, consisting of diatom counts, SEM, BSEI and X-ray imagery will be presented.

  11. Silicon diatom frustules as nanostructured photoelectrodes.

    PubMed

    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. PMID:25061637

  12. Marine diatom biostratigraphy in Pacific Coast neogene basins

    SciTech Connect

    Barron, J.A.

    1988-03-01

    Marine diatoms offer a powerful tool for correlation in the Monterey Formation and related fine-grained siliceous rocks deposited in Pacific Coast basins during the late early Miocene (18 Ma) to the earliest Pliocene (4 Ma). In offshore regions, their biostratigraphic usefulness extends to the late Pliocene and Quaternary. In contrast to other microfossil groups, diatoms are abundant and diverse in cold waters, such as those that have typified the US pacific coast since 14 m.y. (latest Luisian benthic foraminiferal stage). Miocene diatom zones can be readily correlated throughout the North Pacific. Correlations with standard tropical microfossil zonations are well established, and an age resolution approaching 200,000-300,000 years is possible. Diatom frustules, however, are readily destroyed by diagenesis, so they are absent in the porcelanite and chert that typify most lower units of the Monterey Formation. In such circumstances, diatoms are commonly preserved in primary dolomites (beds and concretions), and diatom biostratigraphy can be applied.

  13. Functionalization of the living diatom Thalassiosira weissflogii with thiol moieties

    NASA Astrophysics Data System (ADS)

    Lang, Yvonne; Del Monte, Francisco; Collins, Liam; Rodriguez, Brian J.; Thompson, Kerry; Dockery, Peter; Finn, David P.; Pandit, Abhay

    2013-11-01

    Biomineralization processes identified within diatoms have inspired the design of synthetic silica structures in vitro using alkoxysilane precursors. Here we explore the use of the machinery within the living diatom to fabricate organo-silica constructs using a combination of alkoxysilane and organoalkoxysilane precursors. We report on the incorporation of thiol moieties into the diatom during frustule synthesis. Formation of valves within the parent diatom is monitored using fluorescence microscopy, and the modification of the chemical composition of the diatom is confirmed using energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and 29Si-nuclear magnetic resonance spectroscopy. Chemical modification is achieved without loss of the nano-scale architectural features of the frustule. Extension of this work may allow the chemistry of the diatom to be tailored during synthesis.

  14. Reliability analysis of continuous fiber composite laminates

    NASA Technical Reports Server (NTRS)

    Thomas, David J.; Wetherhold, Robert C.

    1991-01-01

    This paper describes two methods, the maximum distortion energy (MDE) and the principle of independent action (PIA), developed for the analysis of the reliability of a single continuous composite lamina. It is shown that, for the typical laminated plate structure, the individual lamina reliabilities can be combined in order to produce the upper and the lower bounds of reliability for the laminate, similar in nature to the bounds on properties produced from variational elastic methods. These limits were derived for both the interactive and the model failure considerations. Analytical expressions were also derived for the sensitivity of the reliability limits with respect to changes in the Weibull parameters and in loading conditions.

  15. Stiffness and thermoelastic coefficients for composite laminates

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.; Tenek, Lazarus H.

    1992-01-01

    Simple analytic expressions are presented for the stiffness and thermoelastic coefficients of composite laminates in terms of the material properties of the individual layers. Expressions for the derivatives of the various coefficients with respect to each of the material properties and fiber orientation angles are also included. For typical high-performance composites, numerical values are given showing the effects of the stacking sequence and the fiber orientation angle of quasi-isotropic and angle-ply laminates on the values of the various coefficients and their sensitivity derivatives. The expressions for the thermoelastic coefficients and the sensitivity derivatives are given herein for the first time.

  16. Composite laminate free edge reinforcement concepts

    NASA Technical Reports Server (NTRS)

    Howard, W. E.; Gossard, T., Jr.; Jones, R. M.

    1985-01-01

    The presence of a free edge in a laminated composite structure can result in delamination of the composite under certain loading conditions. Linear finite element analysis predicts large or even singular interlaminar stresses near the free edge. Edge reinforcements which will reduce these interlaminar stresses, prevent or delay the onset of delaminations, and thereby increase the strength and life of the structure were studied. Finite element models are used to analyze reinforced laminates which were subsequently fabricated and loaded to failure in order to verify the analysis results.

  17. Fracture behavior of laminated discontinuously reinforced aluminum material

    SciTech Connect

    Osman, T.M. |; Lewandowski, J.J.; Lesuer, D.R.; Syn, C.K.; Hunt, W.H. Jr

    1994-05-01

    Laminated metallic composites are being developed for applications which require high specific stiffness and fracture resistance. Recent work with laminated discontinuously reinforced aluminum (DRA) materials has demonstrated the potential for marked improvements in stable crack growth resistance via extrinsic toughening. The purpose of this work is to compare the fracture mechanisms and fracture resistance of laminated DRA materials to unlaminated DRA materials. In particular, the production of extensive stable crack growth and the associated improvement in damage tolerance in DRA laminates is documented.

  18. Prediction of Composite Laminate Fracture: Micromechanics and Progressive Fracture

    NASA Technical Reports Server (NTRS)

    Gotsis, P. K.; Chamis, C. C.; Minnetyan, L.

    1998-01-01

    An investigation is described on the prediction of first-ply failure and fracture in selected composite laminates. The laminates are made from glass fibers and graphite fibers in epoxy matrices. Failure envelopes are generated for combined loading of these laminates on the basis of first-ply failure and laminate fracture. The evaluation is performed by a micromechanics-based theory and progressive fracture.

  19. Phonons in Diatomic Linear Viscoelastic Chains

    NASA Astrophysics Data System (ADS)

    Palermo, Antonio; Marzani, Alessandro

    In this study waves propagating in a diatomic linear viscoelastic periodic system are investigated with the aim of understanding the operative range of some commonly adopted rheological models. Dispersion laws of a diatomic viscoelastic periodic system under prescribed harmonic motion, i.e. real angular frequency and complex wavenumber (wavenumber and attenuation), are derived. It is shown that such relations can be easily obtained from the linear elastic counterpart in force of the correspondence principle. The complex band structures and energy velocity for the one-dimensional diatomic periodic chains are computed considering both the Kelvin Voigt and the Standard Linear Solid models. It is proven that unusual dispersive behaviors already observed by other researchers when using the Kelvin Voigt model, such as wavenumber-gaps and strong band shifting, are only caused by its nonphysical rigid behavior at high frequencies, since they disappear once the Standard Linear Solid model is adopted. The comparison between the energy velocity of the Kelvin Voigt and Standard Linear Solid discrete systems provides a further confirmation of these findings.

  20. Multi-layer laminate structure and manufacturing method

    DOEpatents

    Keenihan, James R. (Midland, MI); Cleereman, Robert J. (Midland, MI); Eurich, Gerald (Merrill, MI); Graham, Andrew T. (Midland, MI); Langmaid, Joe A. (Caro, MI)

    2012-04-24

    The present invention is premised upon a multi-layer laminate structure and method of manufacture, more particularly to a method of constructing the multi-layer laminate structure utilizing a laminate frame and at least one energy activated flowable polymer.

  1. Multi-layer laminate structure and manufacturing method

    DOEpatents

    Keenihan, James R.; Cleereman, Robert J.; Eurich, Gerald; Graham, Andrew T.; Langmaid, Joe A.

    2013-01-29

    The present invention is premised upon a multi-layer laminate structure and method of manufacture, more particularly to a method of constructing the multi-layer laminate structure utilizing a laminate frame and at least one energy activated flowable polymer.

  2. Light acclimation in diatoms: from phenomenology to mechanisms.

    PubMed

    Wilhelm, Christian; Jungandreas, Anne; Jakob, Torsten; Goss, Reimund

    2014-08-01

    This review summarizes the current knowledge about light acclimation processes in diatoms. Against the background of the phenomenological description of the process in the 70s-80s, the recent progress in diatom genetics has generated new information about the underlying mechanisms. Although the general responses of diatoms to changes in the light climate are comparable to the green algal lineage, many differences in the underlying mechanisms have been observed in the last ten years, yielding clear evidence that the regulatory network in diatoms has unique traits that might explain their ecological success. PMID:24412570

  3. Testing Prospects for Reliable Diatom Nanotechnology in Microgravity

    NASA Technical Reports Server (NTRS)

    Gordon, Richard; Hoover, Richard B.; Tuszynski, Jack A.; deLuis, Javier; Camp, Philip J.; Tiffany, Mary Ann; Nagy, Stephen S.; Lerner, Beatriz E.

    2007-01-01

    The worldwide effort to grow nanotechnology, rather than use lithography, focuses on diatoms, single cell eukaryotic algae with ornate silica shells, which can be replaced by oxides and ceramics, or reduced to elemental silicon, to create complex nanostructures with compositions of industrial and electronics importance. Diatoms produce an enormous variety of structures, some of which are microtubule dependent and perhaps sensitive to microgravity. The NASA Single Loop for Cell Culture (SLCC) for culturing and observing microorganisms permits inexpensive, low labor in-space experiments. We propose to send up to the International Space Station diatom cultures of the three diatom species whose genomes are being sequenced, plus the giant diatoms of Antarctica (up to 2 mm diameter for a single cell) and the unique colonial diatom, Bacillaria paradoxa. Bacillaria cells move against each other in partial synchrony, like a sliding deck of cards, by a microfluidics mechanism. Will normal diatoms have aberrant pattern and shape or motility compared to ground controls? The generation time is typically one day, so that many generations may be examined from one flight. Rapid, directed evolution may be possible running the SLCC as a compustat. The shell shapes and patterns are preserved in hard silica, so that the progress of normal and aberrant morphogenesis may be followed by drying samples on a moving filter paper "diatom tape recorder". With a biodiversity of 100,000 distinct species, diatom nanotechnology may offer a compact and portable nanotechnology toolkit for exploration anywhere.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Micro-Cracking Detection in Laminated Composites

    NASA Technical Reports Server (NTRS)

    Chu, Tsuchin; Leyte, Alma; DiGregorio, Anthony; Russell, Samuel S.; Walker, James L.; Thom, Robert (Technical Monitor)

    2002-01-01

    Porosity and fatigue cracking are two critical factors that affect the performance and safety of cryogenic fuel tanks and feedlines made from unlined laminated or weaved carbon/epoxy materials. This paper presents the experiments to induce fatigue cracking of laminated composites through thermal cycling as well as the feasibility of using Thermography and Ultrasound Spectroscopy technology (UT) to detect and measure such micro-cracking. Carbon/epoxy laminated composite panels were built and cut into strips. These specimens were partially submerged in liquid nitrogen while subjected to various loads on a test machine. Edges of some specimens were polished and etched to determine the degree of micro-cracking. The rest of specimens were then examined with Thermography and Ultrasound Spectroscopy NDE systems to investigate the feasibility of finding such micro-cracking in the laminated composites. Thermography is utilized to determine changes in thermal diffusivity. The degree of cracking may reduce the apparent thermal diffusivity and therefore change the thermal response on the surface. Thermography testing was conducted on a group of specimens where it is desired to have some correlation between the predetermined stress and the thermography data. Ultrasound Spectroscopy was used to determine peak changes between the pre-stressed and stressed samples. Data from the inspections were analyzed and the results are presented in this paper.

  6. Reliability analysis of continuous fiber composite laminates

    NASA Technical Reports Server (NTRS)

    Thomas, David J.; Wetherhold, Robert C.

    1990-01-01

    A composite lamina may be viewed as a homogeneous solid whose directional strengths are random variables. Calculation of the lamina reliability under a multi-axial stress state can be approached by either assuming that the strengths act separately (modal or independent action), or that they interact through a quadratic interaction criterion. The independent action reliability may be calculated in closed form, while interactive criteria require simulations; there is currently insufficient data to make a final determination of preference between them. Using independent action for illustration purposes, the lamina reliability may be plotted in either stress space or in a non-dimensional representation. For the typical laminated plate structure, the individual lamina reliabilities may be combined in order to produce formal upper and lower bounds of reliability for the laminate, similar in nature to the bounds on properties produced from variational elastic methods. These bounds are illustrated for a (0/plus or minus 15)sub s Graphite/Epoxy (GR/EP) laminate. And addition, simple physically plausible phenomenological rules are proposed for redistribution of load after a lamina has failed. These rules are illustrated by application to (0/plus or minus 15)sub s and (90/plus or minus 45/0)sub s GR/EP laminates and results are compared with respect to the proposed bounds.

  7. Laminated insulators having heat dissipation means

    DOEpatents

    Niemann, R.C.; Mataya, K.F.; Gonczy, J.D.

    1980-04-24

    A laminated body is provided with heat dissipation capabilities. The insulator body is formed by dielectric layers interleaved with heat conductive layers, and bonded by an adhesive to form a composite structure. The heat conductive layers include provision for connection to an external thermal circuit.

  8. Labial reduction guide for laminate veneer preparation.

    PubMed

    Cho, Seok-Hwan; Nagy, William W

    2015-10-01

    This article describes a method of fabricating a labial reduction guide for laminate veneer preparations by using a digital tire tread depth gauge and orthodontic wire. The labial reduction guide can help clinicians to achieve accurate reduction of the labial surface. PMID:25979445

  9. Behavior of bolted joints in composite laminates

    SciTech Connect

    Jurf, R.A.

    1986-01-01

    This investigation characterizes bolted joint strength in Kevlar/epoxy and graphite/epoxy (0/45/90/-45)/sub 25/ composite laminates. The fundamental problem of a single bolt hole loaded symmetrically in tension is addressed. The first objective is to generalize the relationships between width, edge distance, hole size, thickness, washer diameter, and degree of lateral constraint with bolted joint strength based on experimental observations. The second objective is to numerically predict the same observation using only lamina properties. The effective laminate behavior is calculated with a nonlinear laminate analysis based on the material and the stacking sequence. The effective laminate properties are input into a nonlinear finite-element analysis to model the bolted joint. The degree of lateral surface constraint is also included in the analysis. The predicted bolted-joint failure regions and strengths were consistent with the experimental data, although improved nonlinear constitutive finite-element models are needed. The analysis is useful in predicting critical width, edge distance,and washer sizes needed to optimize bolted joint strength.

  10. Doped LZO buffer layers for laminated conductors

    DOEpatents

    Paranthaman, Mariappan Parans [Knoxville, TN; Schoop, Urs [Westborough, MA; Goyal, Amit [Knoxville, TN; Thieme, Cornelis Leo Hans [Westborough, MA; Verebelyi, Darren T. [Oxford, MA; Rupich, Martin W. [Framingham, MA

    2010-03-23

    A laminated conductor includes a metallic substrate having a surface, a biaxially textured buffer layer supported by the surface of the substrate, the biaxially textured buffer layer comprising LZO and a dopant for mitigating metal diffusion through the LZO, and a biaxially textured conductor layer supported by the biaxially textured buffer layer.

  11. Compression failure of angle-ply laminates

    NASA Technical Reports Server (NTRS)

    Peel, Larry D.; Hyer, Michael W.; Shuart, Mark J.

    1991-01-01

    The present work deals with modes and mechanisms of failure in compression of angle-ply laminates. Experimental results were obtained from 42 angle-ply IM7/8551-7a specimens with a lay-up of ((plus or minus theta)/(plus or minus theta)) sub 6s where theta, the off-axis angle, ranged from 0 degrees to 90 degrees. The results showed four failure modes, these modes being a function of off-axis angle. Failure modes include fiber compression, inplane transverse tension, inplane shear, and inplane transverse compression. Excessive interlaminar shear strain was also considered as an important mode of failure. At low off-axis angles, experimentally observed values were considerably lower than published strengths. It was determined that laminate imperfections in the form of layer waviness could be a major factor in reducing compression strength. Previously developed linear buckling and geometrically nonlinear theories were used, with modifications and enhancements, to examine the influence of layer waviness on compression response. The wavy layer is described by a wave amplitude and a wave length. Linear elastic stress-strain response is assumed. The geometrically nonlinear theory, in conjunction with the maximum stress failure criterion, was used to predict compression failure and failure modes for the angle-ply laminates. A range of wave length and amplitudes were used. It was found that for 0 less than or equal to theta less than or equal to 15 degrees failure was most likely due to fiber compression. For 15 degrees less than theta less than or equal to 35 degrees, failure was most likely due to inplane transverse tension. For 35 degrees less than theta less than or equal to 70 degrees, failure was most likely due to inplane shear. For theta less than 70 degrees, failure was most likely due to inplane transverse compression. The fiber compression and transverse tension failure modes depended more heavily on wave length than on wave amplitude. Thus using a single parameter, such as a ratio of wave amplitude to wave length, to describe waviness in a laminate would be inaccurate. Throughout, results for AS4/3502, studied previously, are included for comparison. At low off-axis angles, the AS4/3502 material system was found to be less sensitive to layer waviness than IM7/8551-7a. Analytical predictions were also obtained for laminates with waviness in only some of the layers. For this type of waviness, laminate compression strength could also be considered a function of which layers in the laminate were wavy, and where those wavy layers were. Overall, the geometrically nonlinear model correlates well with experimental results.

  12. Determining Shear Stress Distribution in a Laminate

    NASA Technical Reports Server (NTRS)

    Bednarcyk, Brett A.; Aboudi, Jacob; Yarrington, Phillip W.

    2010-01-01

    A "simplified shear solution" method approximates the through-thickness shear stress distribution within a composite laminate based on an extension of laminated beam theory. The method does not consider the solution of a particular boundary value problem; rather, it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply-level stresses can be efficiently determined from global load resultants at a given location in a structure and used to evaluate the margin of safety on a ply-by-ply basis. The simplified shear solution stress distribution is zero at free surfaces, continuous at ply boundaries, and integrates to the applied shear load. The method has been incorporated within the HyperSizer commercial structural sizing software to improve its predictive capability for designing composite structures. The HyperSizer structural sizing software is used extensively by NASA to design composite structures. In the case of through-thickness shear loading on panels, HyperSizer previously included a basic, industry-standard, method for approximating the resulting shear stress distribution in sandwich panels. However, no such method was employed for solid laminate panels. The purpose of the innovation is to provide an approximation of the through-thickness shear stresses in a solid laminate given the through-thickness shear loads (Qx and Qy) on the panel. The method was needed for implementation within the HyperSizer structural sizing software so that the approximated ply-level shear stresses could be utilized in a failure theory to assess the adequacy of a panel design. The simplified shear solution method was developed based on extending and generalizing bi-material beam theory to plate-like structures. It is assumed that the through-thickness shear stresses arise due to local bending of the laminate induced by the through-thickness shear load, and by imposing equilibrium both vertically and horizontally, the through-thickness shear stress distribution can be calculated. The resulting shear stresses integrate to the applied shear load, are continuous at the ply interfaces, and are zero at the laminate-free surfaces. If both Qx and Qy shear loads are present, it is assumed that they act independently and that their effects can be superposed. The calculated shear stresses can be rotated within each ply to the principal material coordinates for use in a ply-level failure criterion. The novelty of the simplified shear solution method is its simplicity and the fact that it does not require solution of a particular boundary value problem. The advantages of the innovation are that an approximation of the though-thickness shear stress distribution can be quickly determined for any solid laminate or solid laminate region within a stiffened panel.

  13. Involvement of the Lamin Rod Domain in Heterotypic Lamin Interactions Important for Nuclear Organization

    PubMed Central

    Schirmer, Eric C.; Guan, Tinglu; Gerace, Larry

    2001-01-01

    The nuclear lamina is a meshwork of intermediate-type filament proteins (lamins) that lines the inner nuclear membrane. The lamina is proposed to be an important determinant of nuclear structure, but there has been little direct testing of this idea. To investigate lamina functions, we have characterized a novel lamin B1 mutant lacking the middle ?4/5 of its ?-helical rod domain. Though retaining only 10 heptads of the rod, this mutant assembles into intermediate filament-like structures in vitro. When expressed in cultured cells, it concentrates in patches at the nuclear envelope. Concurrently, endogenous lamins shift from a uniform to a patchy distribution and lose their complete colocalization, and nuclei become highly lobulated. In vitro binding studies suggest that the internal rod region is important for heterotypic associations of lamin B1, which in turn are required for proper organization of the lamina. Accompanying the changes in lamina structure induced by expression of the mutant, nuclear pore complexes and integral membrane proteins of the inner membrane cluster, principally at the patches of endogenous lamins. Considered together, these data indicate that lamins play a major role in organizing other proteins in the nuclear envelope and in determining nuclear shape. PMID:11331300

  14. Edge effects in angle-ply composite laminates

    NASA Technical Reports Server (NTRS)

    Hsu, P. W.; Herakovich, C. T.

    1977-01-01

    This paper presents the results of a zeroth-order solution for edge effects in angle-ply composite laminates obtained using perturbation techniques and a limiting free body approach. The general solution for edge effects in laminates of arbitrary angle ply is applied to the special case of a (+ or - 45)s graphite/epoxy laminate. Interlaminar stress distributions are obtained as a function of the laminate thickness-to-width ratio and compared to finite difference results. The solution predicts stable, continuous stress distributions, determines finite maximum tensile interlaminar normal stress and provides mathematical evidence for singular interlaminar shear stresses in (+ or - 45) graphite/epoxy laminates.

  15. Nonlinear laminate analysis for metal matrix fiber composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1981-01-01

    A nonlinear laminate analysis is described for predicting the mechanical behavior (stress-strain relationships) of angleplied laminates in which the matrix is strained nonlinearly by both the residual stress and the mechanical load and in which additional nonlinearities are induced due to progressive fiber fractures and ply relative rotations. The nonlinear laminate analysis (NLA) is based on linear composite mechanics and a piece wise linear laminate analysis to handle the nonlinear responses. Results obtained by using this nonlinear analysis on boron fiber/aluminum matrix angleplied laminates agree well with experimental data. The results shown illustrate the in situ ply stress-strain behavior and synergistic strength enhancement.

  16. Strength and flaw elimination assessment in tape cast ceramic laminates

    SciTech Connect

    Ham-su, R.; Wilkinson, D.S.

    1992-10-01

    Monolithic Al2O3 ceramic laminates were fabricated via tape-casting process. The strength of single tapes were compared with laminates using biaxial flexure tests. The average fracture stress was unchanged. However, the laminates presented a multimodal strength distribution. The feasibility of eliminating or diminishing void-type flaws present in the green tapes was assessed. To this end, tapes were first punctured, then laminated and sintered and the effect of these known flaws in the final ceramic was assessed by four-point bending tests. The thermocompression of green tapes during laminate fabrication was found to drastically reduce the severity of flaws. 6 refs.

  17. Characterization of graphite/epoxy laminates for aeroelastic tailoring

    NASA Technical Reports Server (NTRS)

    Shyprykevich, P.

    1979-01-01

    A study of interaction between wing bending and twist by graphite/epoxy anisotropic laminates used in aircraft wing skins is presented. The laminates were used as covers for subscale box beams supported as a cantilever and tested in tip shear and tip torque, measuring beam response with a reflected light technique. The results indicated that the in-plane stiffness properties of anisotropic laminates can be predicted if the layer properties of the composite materials are known; thus, the coupled bending/twist response of wing type structures made from these laminates can be determined provided the limits of the laminate linear behavior are not significantly exceeded.

  18. Fatigue damage development of various CFRP-laminates

    NASA Technical Reports Server (NTRS)

    Schulte, K.; Baron, CH.

    1988-01-01

    The chronic strength and fatigue behavior of a woven carbon-fiber reinforced laminate in a balanced eight-shaft satin weave style was compared to nonwoven laminates with an equivalent cross-ply layup. Half the fibers were arranged in the direction of the load and the other half perpendicular to it. Two types of nonwoven laminates consisting of continuous fibers and aligned discontinuous fibers, both produced from carbon fiber prepregs, were studied. The cross-ply laminate with continuous fiber showed the best characteristics with regard to both static strength and fatigue. The similarities and differences in damage mechanisms in the laminates are described.

  19. Prediction of Composite Laminate Fracture: Micromechanics and Progressive Fracture

    NASA Technical Reports Server (NTRS)

    Gotsis, P. K.; Chamis, C. C.; Minnetyan, L.

    1996-01-01

    This report describes an investigation to predict first-ply failure and final fracture in selected composite laminates subjected to inplane loads. The laminates were composed of glass fiber and graphite fibers in epoxy matrices. Failure envelopes based on first-ply failure and laminate fracture were generated for combined loading of these laminates. Predictions were evaluated by micromechanics-based theory and progressive fracture. The results show that, for most cases, combined tensile loading significantly enhanced the laminate fracture stress in comparison to the uniaxial loading.

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

    PubMed

    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. PMID:25377486

  1. Ultrasonic monitoring of asymmetric carbon fibre reinforced aluminum laminates

    NASA Astrophysics Data System (ADS)

    Zhao, Junqing; Yang, Fan; Wang, Rongguo

    2013-08-01

    Asymmetric carbon fibre reinforced aluminum alloy laminates was manufactured for the purpose with repeat tensile test, which will be applied in composite pressure vessel. Ultrasonic C scan and A scan approach are used to evaluate the damage of the asymmetric CFRP-Al (carbon fibre reinforced aluminum alloy) laminates. Nondestructive detection is carried out for the CFRP-Al laminates before and after tensile test. Comparison results and pulse echo analysis show that when subjected to repeat tensile test with 70% elastic limit strain load of the CFRP laminates, the interface debonding between CFRP and Al will not occur but the delamination within CFRP laminates becomes the main damage of the asymmetric CFRP-Al laminates. This investigation indicated that combined ultrasonic C scan and A scan is available for damage evaluation of fibre metal laminates.

  2. Optimal design of stiffened composite laminates in compression

    SciTech Connect

    Harik, I.E.; Guo, M.W.

    1996-11-01

    For the purpose of optimizing the design of stiffened composite laminates in compression, numerical results from a layerwise (zig-zag) finite element model are presented. The laminate is subdivided into element layers in the thickness direction. The element layers and stiffeners are modeled using the degenerated shell element and general 3-D beam element, respectively. The advantage of this model is its ability to predict the effects of the lateral stability of the stiffener on the buckling of the laminate itself. The influence of the degree of orthotropy, laminate aspect ratio, and laminate layouts, as well as the stiffener orientation and sectional dimensions, are investigated through parametric studies. The significance of this study lies in the ability of the proposed finite element model to predict the optimum stiffener depth and ply-angle of the laminate. The findings clearly show that deeper stiffeners do not always lead to stiffer composite laminates.

  3. Nuclear lamins: key regulators of nuclear structure and activities

    PubMed Central

    Prokocimer, Miron; Davidovich, Maya; Nissim-Rafinia, Malka; Wiesel-Motiuk, Naama; Bar, Daniel Z; Barkan, Rachel; Meshorer, Eran; Gruenbaum, Yosef

    2009-01-01

    The nuclear lamina is a proteinaceous structure located underneath the inner nuclear membrane (INM), where it associates with the peripheral chromatin. It contains lamins and lamin-associated proteins, including many integral proteins of the INM, chromatin modifying proteins, transcriptional repressors and structural proteins. A fraction of lamins is also present in the nucleoplasm, where it forms stable complexes and is associated with specific nucleoplasmic proteins. The lamins and their associated proteins are required for most nuclear activities, mitosis and for linking the nucleoplasm to all major cytoskeletal networks in the cytoplasm. Mutations in nuclear lamins and their associated proteins cause about 20 different diseases that are collectively called laminopathies’. This review concentrates mainly on lamins, their structure and their roles in DNA replication, chromatin organization, adult stem cell differentiation, aging, tumorogenesis and the lamin mutations leading to laminopathic diseases. PMID:19210577

  4. Novel Remanufacturing Process of Recycled Polytetrafluoroethylene(PTFE)/GF Laminate

    NASA Astrophysics Data System (ADS)

    Xi, Z.; Ghita, O. R.; Johnston, P.; Evans, K. E.

    2011-01-01

    Currently, the PTFE/GF laminate and PTFE PCB manufacturers are under considerable pressure to address the recycling issues due to Waste Electrical and Electronic Equipment (WEEE) Directive, shortage of landfill capacity and cost of disposal. This study is proposing a novel manufacture method for reuse of the mechanical ground PTFE/Glass fibre (GF) laminate and production of the first reconstitute PTFE/GF laminate. The reconstitute PTFE/GF laminate proposed here consists of a layer of recycled sub-sheet, additional layers of PTFE and PTFE coated glass cloth, also covered by copper foils. The reconstitute PTFE/GF laminate showed good dielectric properties. Therefore, there is potential to use the mechanical ground PTFE/GF laminate powder to produce reconstitute PTFE/GF laminate, for use in high frequencies PCB applications.

  5. Tensile stress-strain behavior of boron/aluminum laminates

    NASA Technical Reports Server (NTRS)

    Sova, J. A.; Poe, C. C., Jr.

    1978-01-01

    The tensile stress-strain behavior of five types of boron/aluminum laminates was investigated. Longitudinal and transverse stress-strain curves were obtained for monotonic loading to failure and for three cycles of loading to successively higher load levels. The laminate strengths predicted by assuming that the zero deg plies failed first correlated well with the experimental results. The stress-strain curves for all the boron/aluminum laminates were nonlinear except at very small strains. Within the small linear regions, elastic constants calculated from laminate theory corresponded to those obtained experimentally to within 10 to 20 percent. A limited amount of cyclic loading did not affect the ultimate strength and strain for the boron/aluminum laminates. The laminates, however, exhibited a permanent strain on unloading. The Ramberg-Osgood equation was fitted to the stress-strain curves to obtain average curves for the various laminates.

  6. Diatoms respire nitrate to survive dark and anoxic conditions

    PubMed Central

    Kamp, Anja; de Beer, Dirk; Nitsch, Jana L.; Lavik, Gaute; Stief, Peter

    2011-01-01

    Diatoms survive in dark, anoxic sediment layers for months to decades. Our investigation reveals a correlation between the dark survival potential of marine diatoms and their ability to accumulate NO3? intracellularly. Axenic strains of benthic and pelagic diatoms that stored 11274 mM NO3? in their cells survived for 628 wk. After sudden shifts to dark, anoxic conditions, the benthic diatom Amphora coffeaeformis consumed 8487% of its intracellular NO3? pool within 1 d. A stable-isotope labeling experiment proved that 15NO3? consumption was accompanied by the production and release of 15NH4+, indicating dissimilatory nitrate reduction to ammonium (DNRA). DNRA is an anaerobic respiration process that is known mainly from prokaryotic organisms, and here shown as dissimilatory nitrate reduction pathway used by a eukaryotic phototroph. Similar to large sulfur bacteria and benthic foraminifera, diatoms may respire intracellular NO3? in sediment layers without O2 and NO3?. The rapid depletion of the intracellular NO3? storage, however, implies that diatoms use DNRA to enter a resting stage for long-term survival. Assuming that pelagic diatoms are also capable of DNRA, senescing diatoms that sink through oxygen-deficient water layers may be a significant NH4+ source for anammox, the prevalent nitrogen loss pathway of oceanic oxygen minimum zones. PMID:21402908

  7. Biomimetic Photonic Crystals based on Diatom Algae Frustules

    NASA Astrophysics Data System (ADS)

    Mishler, Jonathan; Alverson, Andrew; Herzog, Joseph

    2015-03-01

    Diatom algae are unicellular, photosynthetic microorganisms with a unique external shell known as a frustule. Frustules, which are composed of amorphous silica, exhibit a unique periodic nano-patterning, distinguishing diatoms from other types of phytoplankton. Diatoms have been studied for their distinctive optical properties due to their resemblance of photonic crystals. In this regard, diatoms are not only considered for their applications as photonic crystals, but also for their use as biomimetic templates for artificially fabricated photonic crystals. Through the examination and measurement of the physical characteristics of many scanning electron microscope (SEM) images of diatom frustules, a biomimetic photonic crystal derived from diatom frustules can be recreated and modeled with the finite element method. In this approach, the average geometries of the diatom frustules are used to recreate a 2-dimensional photonic crystal, after which the electric field distribution and optical transmission through the photonic crystal are both measured. The optical transmission is then compared to the transmission spectra of a regular hexagonal photonic crystal, revealing the effects of diatom geometry on their optical properties. Finally, the dimensions of the photonic crystal are parametrically swept, allowing for further control over the transmission of light through the photonic crystal.

  8. Diatoms respire nitrate to survive dark and anoxic conditions.

    PubMed

    Kamp, Anja; de Beer, Dirk; Nitsch, Jana L; Lavik, Gaute; Stief, Peter

    2011-04-01

    Diatoms survive in dark, anoxic sediment layers for months to decades. Our investigation reveals a correlation between the dark survival potential of marine diatoms and their ability to accumulate NO(3)(-) intracellularly. Axenic strains of benthic and pelagic diatoms that stored 11-274 mM NO(3)(-) in their cells survived for 6-28 wk. After sudden shifts to dark, anoxic conditions, the benthic diatom Amphora coffeaeformis consumed 84-87% of its intracellular NO(3)(-) pool within 1 d. A stable-isotope labeling experiment proved that (15)NO(3)(-) consumption was accompanied by the production and release of (15)NH(4)(+), indicating dissimilatory nitrate reduction to ammonium (DNRA). DNRA is an anaerobic respiration process that is known mainly from prokaryotic organisms, and here shown as dissimilatory nitrate reduction pathway used by a eukaryotic phototroph. Similar to large sulfur bacteria and benthic foraminifera, diatoms may respire intracellular NO(3)(-) in sediment layers without O(2) and NO(3)(-). The rapid depletion of the intracellular NO(3)(-) storage, however, implies that diatoms use DNRA to enter a resting stage for long-term survival. Assuming that pelagic diatoms are also capable of DNRA, senescing diatoms that sink through oxygen-deficient water layers may be a significant NH(4)(+) source for anammox, the prevalent nitrogen loss pathway of oceanic oxygen minimum zones. PMID:21402908

  9. Chitin in Diatoms and Its Association with the Cell Wall ?

    PubMed Central

    Durkin, Colleen A.; Mock, Thomas; Armbrust, E. Virginia

    2009-01-01

    Chitin is a globally abundant polymer widely distributed throughout eukaryotes that has been well characterized in only a few lineages. Diatoms are members of the eukaryotic lineage of stramenopiles. Of the hundreds of diatom genera, two produce long fibers of chitin that extrude through their cell walls of silica. We identify and describe here genes encoding putative chitin synthases in a variety of additional diatom genera, indicating that the ability to produce chitin is more widespread and likely plays a more central role in diatom biology than previously considered. Diatom chitin synthases fall into four phylogenetic clades. Protein domain predictions and differential gene expression patterns provide evidence that chitin synthases have multiple functions within a diatom cell. Thalassiosira pseudonana possesses six genes encoding three types of chitin synthases. Transcript abundance of the gene encoding one of these chitin synthase types increases when cells resume division after short-term silicic acid starvation and during short-term limitation by silicic acid or iron, two nutrient conditions connected in the environment and known to affect the cell wall. During long-term silicic acid starvation transcript abundance of this gene and one additional chitin synthase gene increased at the same time a chitin-binding lectin localized to the girdle band region of the cell wall. Together, these results suggest that the ability to produce chitin is more widespread in diatoms than previously thought and that a subset of the chitin produced by diatoms is associated with the cell wall. PMID:19429777

  10. Using diatom assemblages to assess urban stream conditions

    USGS Publications Warehouse

    Walker, C.E.; Pan, Y.

    2006-01-01

    We characterized changes in diatom assemblages along an urban-to-rural gradient to assess impacts of urbanization on stream conditions. Diatoms, water chemistry, and physical variables of riffles at 19 urban and 28 rural stream sites were sampled and assessed during the summer base flow period. Near stream land use was characterized using GIS. In addition, one urban and one rural site were sampled monthly throughout a year to assess temporal variation of diatom assemblages between the urban and rural stream sites. Canonical correspondence analysis (CCA) showed that the 1st ordination axis distinctly separated rural and urban sites. This axis was correlated with conductivity (r = 0.75) and % near-stream commercial/industrial land use (r = 0.55). TWINSPAN classified all sites into four groups based on diatom assemblages. These diatom-based site groups were significantly different in water chemistry (e.g., conductivity, dissolved nutrients), physical habitat (e.g., % stream substrate as fines), and near-stream land use. CCA on the temporal diatom data set showed that diatom assemblages had high seasonal variation along the 2nd axis in both urban and rural sites, however, rural and urban sites were well separated along the 1st ordination axis. Our results suggest that changes in diatom assemblages respond to urban impacts on stream conditions. ?? Springer 2006.

  11. SEASONAL ABUNDANCE PATTERNS OF DIATOMS ON 'CLADOPHORA' IN LAKE HURON

    EPA Science Inventory

    Rocks bearing Cladophora were collected from May to November 1979 at two locations near Harbor Beach, Michigan, in Lake Huron to document seasonal patterns of epiphytic diatom abundance and diatom proportion of the Cladophora-epiphyte assemblage biomass in an area receiving efflu...

  12. Watershed Alteration Impacts to Benthic Diatom Assemblages in Streams

    EPA Science Inventory

    To examine the use of diatoms as indicators of urban impacts to streams, we identified relationships of diatom assemblages with water chemistry and land use for 160 sites in New England. The first axis of a nonmetric multidimensional scaling ordination showed significant relation...

  13. Continental diatoms as indicators of long-term environmental change

    USGS Publications Warehouse

    Bradbury, J. Platt

    1999-01-01

    It is curious that diatoms, whose short lifespans and capacity for rapid regeneration make them especially suitable for short-term paleoenvironmental studies, would also have a significant role as indicators of long-term environmental change. This chapter explores the nature of long diatom records, their relation to global environmental changes, guidelines for their interpretation, and problems common to such records.

  14. Late Neogene changes in diatom sedimentation in the North Pacific

    USGS Publications Warehouse

    Barron, J.A.

    1998-01-01

    During the late Neogene, North Pacific diatom sedimentation underwent major changes in response to high-latitude cooling and changes in surface and deep water circulation. At 9 Ma diatom mass accumulation rates (MARs) increased in the NW Pacific and off northeast Japan, possibly due to shoaling of the Isthmus of Panama, which lead to an enrichment of nutrients in North Pacific deep waters. During the latest Miocene, diatom MARs increased progressively off southern California (6.5 Ma), at high latitudes of the North Pacific (6.2 Ma), and off northeastern Japan (5.5 Ma), presumably in response to high latitude cooling. At about 4.5 Ma diatom sedimentation abruptly increased in the NW Pacific but declined off Japan and California, coincident with the onset of a prolonged period of high-latitude warmth. Enhanced upwelling of nutrient-rich deep waters in the NW Pacific probably stimulated diatom production there. A major step in high latitude cooling at 2.7 Ma caused a reversal of these mid Pliocene diatom sedimentation patterns. Upwelling of deep, nutrient-rich waters waned at higher latitudes, leading to a decline in diatom productivity; while wind-driven, coastal upwelling increased off southern California and stimulated diatom growth.

  15. The Central Carbon and Energy Metabolism of Marine Diatoms

    PubMed Central

    Obata, Toshihiro; Fernie, Alisdair R.; Nunes-Nesi, Adriano

    2013-01-01

    Diatoms are heterokont algae derived from a secondary symbiotic event in which a eukaryotic host cell acquired an eukaryotic red alga as plastid. The multiple endosymbiosis and horizontal gene transfer processes provide diatoms unusual opportunities for gene mixing to establish distinctive biosynthetic pathways and metabolic control structures. Diatoms are also known to have significant impact on global ecosystems as one of the most dominant phytoplankton species in the contemporary ocean. As such their metabolism and growth regulating factors have been of particular interest for many years. The publication of the genomic sequences of two independent species of diatoms and the advent of an enhanced experimental toolbox for molecular biological investigations have afforded far greater opportunities than were previously apparent for these species and re-invigorated studies regarding the central carbon metabolism of diatoms. In this review we discuss distinctive features of the central carbon metabolism of diatoms and its response to forthcoming environmental changes and recent advances facilitating the possibility of industrial use of diatoms for oil production. Although the operation and importance of several key pathways of diatom metabolism have already been demonstrated and determined, we will also highlight other potentially important pathways wherein this has yet to be achieved. PMID:24957995

  16. Integration of TiO2 into the diatom Thalassiosira weissflogii during frustule synthesis

    PubMed Central

    Lang, Yvonne; Monte, Francisco del; Rodriguez, Brian J.; Dockery, Peter; Finn, David P.; Pandit, Abhay

    2013-01-01

    Nature has inspired the design of complex hierarchical structures in the field of material science. Diatoms, unicellular algae with a hallmark intricate siliceous cell wall, have provided such a stimulus. Altering the chemistry of the diatom frustule has been explored to expand on the potential application of diatoms. The ability to modify the diatom in vivo opens the possibility to tailor the diatom to the end application. Herein, we report the chemical modification of the living diatom T. weissflogii using a titania precursor, titanium (IV) bis-(ammonium lactato)-dihydroxide (TiBALDH). Incorporation of Ti into the diatom is achieved via repeated treatment of cultures with non-toxic concentrations of TiBALDH. The characteristic architectural features of the diatom are unaltered following chemical modification. Transformation of the living diatom provides opportunity to confer novel structural, chemical or functional properties upon the diatom. We report on a photocatalytic ability imparted upon the TiBALDH-modified diatom. PMID:24220344

  17. Periodic Traveling Waves in Diatomic Granular Chains

    NASA Astrophysics Data System (ADS)

    Betti, Matthew; Pelinovsky, Dmitry E.

    2013-10-01

    We study bifurcations of periodic traveling waves in diatomic granular chains from the anti-continuum limit, when the mass ratio between the light and heavy beads is zero. We show that every limiting periodic wave is uniquely continued with respect to the mass ratio parameter, and the periodic waves with a wavelength larger than a certain critical value are spectrally stable. Numerical computations are developed to study how this solution family is continued to the limit of equal mass ratio between the beads, where periodic traveling waves of homogeneous granular chains exist.

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

    PubMed

    Poulsen, Nicole; Krger, 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. PMID:24689803

  19. Regulated growth of diatom cells on self-assembled monolayers

    PubMed Central

    Umemura, Kazuo; Yamada, Tomoaki; Maeda, Yuta; Kobayashi, Koichi; Kuroda, Reiko; Mayama, Shigeki

    2007-01-01

    We succeeded in regulating the growth of diatom cells on chemically modified glass surfaces. Glass surfaces were functionalized with -CF3, -CH3, -COOH, and -NH2 groups using the technique of self-assembled monolayers (SAM), and diatom cells were subsequently cultured on these surfaces. When the samples were rinsed after the adhesion of the diatom cells on the modified surfaces, the diatoms formed two dimensional arrays; this was not possible without the rinsing treatment. Furthermore, we examined the number of cells that grew and their motility by time-lapse imaging in order to clarify the interaction between the cells and SAMs. We hope that our results will be a basis for developing biodevices using living photosynthetic diatom cells. PMID:17381834

  20. Biotemplated diatom silica-titania materials for air purification.

    PubMed

    Van Eynde, Erik; Tytgat, Tom; Smits, Marianne; Verbruggen, Sammy W; Hauchecorne, Birger; Lenaerts, Silvia

    2013-04-01

    We present a novel manufacture route for silica-titania photocatalysts using the diatom microalga Pinnularia sp. Diatoms self-assemble into porous silica cell walls, called frustules, with periodic micro-, meso- and macroscale features. This unique hierarchical porous structure of the diatom frustule is used as a biotemplate to incorporate titania by a sol-gel methodology. Important material characteristics of the modified diatom frustules under study are morphology, crystallinity, surface area, pore size and optical properties. The produced biosilica-titania material is evaluated towards photocatalytic activity for NOx abatement under UV radiation. This research is the first step to obtain sustainable, well-immobilised silica-titania photocatalysts using diatoms. PMID:23128085

  1. Applications of Diatoms as Potential Microalgae in Nanobiotechnology

    PubMed Central

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

    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 explora-tion, 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, biomineraliza-tion, 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. PMID:23678445

  2. Spatial Response of Epilithic Diatom Communities to Downstream Nutrient Increases.

    PubMed

    Schuch, Marilia; Oliveira, Maria Angelica; Lobo, Eduardo A

    2015-06-01

    To monitor water quality and investigate relationships between downstream nutrient increases and diatom communities in the Pardo River Basin, Brazil, water and diatom samples were collected between 2005 and 2009. There were significant differences in diatom community composition among all river zones, with the greatest differences found between the upper and lower reaches. Significant changes were detected in relative abundances of diatom species and spatial structuring was evident. Dissolved oxygen, phosphates, turbidity, Eicherichia coli, and total dissolved solids were the most important variables shaping diatom communities, characterizing an organic pollution and eutrophication gradient. However, the hypothesis of sensitive species prevailing upstream and their gradual downstream replacement for more tolerant species was not confirmed because shifts in relative abundances of the same group of species in both the upper and lower reaches of the rivers were identified. PMID:26459823

  3. The structural response of unsymmetrically laminated composite cylinders

    NASA Technical Reports Server (NTRS)

    Butler, T. A.; Hyer, M. W.

    1989-01-01

    The responses of an unsymmetrically laminated fiber-reinforced composite cylinder to an axial compressive load, a torsional load, and the temperature change associated with cooling from the processing temperature to the service temperature are investigated. These problems are considered axisymmetric and the response is studied in the context of linear elastic material behavior and geometrically linear kinematics. Four different laminates are studied: a general unsymmetric laminate; two unsymmetric but more conventional laminates; and a conventional quasi-isotropic symmetric laminate. The responses based on closed-form solutions for different boundary conditions are computed and studied in detail. Particular emphasis is directed at understanding the influence of elastic couplings in the laminates. The influence of coupling decreased from a large effect in the general unsymmetric laminate, to practically no effect in the quasi-isotropic laminate. For example, the torsional loading of the general unsymmetric laminate resulted in a radial displacement. The temperature change also caused a significant radial displacement to occur near the ends of the cylinder. On the other hand, the more conventional unsymmetric laminate and the quasi-isotropic cylinder did not deform radially when subjected to a torsional load. From the results obtained, it is clear the degree of elastic coupling can be controlled and indeed designed into a cylinder, the degree and character of the coupling being dictated by the application.

  4. The Role of Diatoms in Export Flux

    NASA Astrophysics Data System (ADS)

    Kemp, A. E.; Pike, J.; Pearce, R. B.; Davies, A.

    2005-12-01

    Recent oceanographic observations and experiments have shed a new light on the mechanisms of production in oligotrophic settings and the significance of this for export. Phytoplankton species and lifestyles (e.g. symbiosis with N-fixing cyanobacteria) previously thought to be characteristic of subsistence or low production have been shown to be involved in major production and export events. Parallel studies of ancient Quaternary and Neogene sediments have confirmed that major flux of both opal and organic carbon may be associated with such styles of production. In particular, a number of genera and species of diatoms, not hitherto regarded as biogeochemically significant appear to be key players in export in stratified or oligotrophic settings. Recent research extending to marine sediments of Cretaceous age shows that ancestors of these key diatoms were the dominant genera of the time and may have played a critical role in export from Cretaceous seas. The implications of these findings call for a species-approach both to modern oceanographic observations and in studies of ancient sediments.

  5. Nonnuclear Attractors in Heteronuclear Diatomic Systems.

    PubMed

    Terrabuio, Luiz Alberto; Teodoro, Tiago Quevedo; Matta, Chérif F; Haiduke, Roberto Luiz Andrade

    2016-03-01

    Nonnuclear attractors (NNAs) are observed in the electron density of a variety of systems, but the factors governing their appearance and their contribution to the system's properties remain a mystery. The NNA occurring in homo- and heteronuclear diatomics of main group elements with atomic numbers up to Z = 38 is investigated computationally (at the UCCSD/cc-pVQZ level of theory) by varying internuclear separations. This was done to determine the NNA occurrence window along with the evolution of the respective pseudoatomic basin properties. Two distinct categories of NNAs were detected in the data analyzed by means of catastrophe theory. Type "a" implies electronic charge transfer between atoms mediated by a pseudoatom. Type "b" shows an initial relocation of some electronic charge to a pseudoatom, which posteriorly returns to the same atom that donated this charge in the first place. A small difference of polarizability between the atoms that compose these heteronuclear diatomics seems to favor NNA formation. We also show that the NNA arising tends to result in some perceptible effects on molecular dipole and/or quadrupole moment curves against internuclear distance. Finally, successive cationic ionization results in the fast disappearance of the NNA in Li2 indicating that its formation is mainly governed by the field generated by the quantum mechanical electronic density and only depends parametrically on the bare nuclear field/potential at a given molecular geometry. PMID:26842391

  6. Diatom Milking: A Review and New Approaches

    PubMed Central

    Vinayak, Vandana; Manoylov, Kalina M.; Gateau, Hélène; Blanckaert, Vincent; Hérault, Josiane; Pencréac’h, Gaëlle; Marchand, Justine; Gordon, Richard; Schoefs, Benoît

    2015-01-01

    The rise of human populations and the growth of cities contribute to the depletion of natural resources, increase their cost, and create potential climatic changes. To overcome difficulties in supplying populations and reducing the resource cost, a search for alternative pharmaceutical, nanotechnology, and energy sources has begun. Among the alternative sources, microalgae are the most promising because they use carbon dioxide (CO2) to produce biomass and/or valuable compounds. Once produced, the biomass is ordinarily harvested and processed (downstream program). Drying, grinding, and extraction steps are destructive to the microalgal biomass that then needs to be renewed. The extraction and purification processes generate organic wastes and require substantial energy inputs. Altogether, it is urgent to develop alternative downstream processes. Among the possibilities, milking invokes the concept that the extraction should not kill the algal cells. Therefore, it does not require growing the algae anew. In this review, we discuss research on milking of diatoms. The main themes are (a) development of alternative methods to extract and harvest high added value compounds; (b) design of photobioreactors; (c) biodiversity and (d) stress physiology, illustrated with original results dealing with oleaginous diatoms. PMID:25939034

  7. Fabrication of CFRP/Al Active Laminates

    NASA Astrophysics Data System (ADS)

    Asanuma, Hiroshi; Haga, Osamu; Ohira, Junichiro; Takemoto, Kyosuke; Imori, Masataka

    This paper describes fabrication and evaluation of the active laminate. It was made by hot-pressing of an aluminum plate as a high CTE material, a unidirectional CFRP prepreg as a low CTE material and an electric resistance heater, a KFRP prepreg as a low CTE material and an insulator between them, and copper foils as electrodes. In this study, fabricating conditions and performances such as curvature change and output force were examined. Under optimized fabricating conditions, it became clear that 1) the curvature of the active laminate linearly changes as a function of temperature, between room temperature and its hot pressing temperature without hysteresis by electric resistance heating of carbon fiber in the CFRP layer and cooling, and 2) the output force against a fixed punch almost linearly increases with increasing temperature during heating from 313K up to around the glass transition temperature of the epoxy matrix.

  8. Flow and pressure experiments for laminate fabrication

    NASA Astrophysics Data System (ADS)

    Poursartip, Anoush; Riahi, Golnar; Smith, Gregory

    Experimental methods are presented to determine the amount of resin flow and the pressure distribution within a composite laminate during cure. The resin flow method is analogous to the use of radioactive tracers in other applications. Heavier elements such as chlorine and bromine, which may be naturally present in small amounts in resins are used to follow resin flow and mixing. The presence and quantity of these tags is determined using wavelength dispersive X-ray analysis. The pressure distribution is measured using small postage stamp-sized resistive sensors. It is shown that these sensors can currently provide a qualitative picture of the pressure distribution through the thickness of the laminate. Results from these methods are discussed in light of current processing models.

  9. Investigating Delamination Migration in Composite Tape Laminates

    NASA Technical Reports Server (NTRS)

    Ratcliffe, James G.; DeCarvalho, Nelson V.

    2014-01-01

    A modification to a recently developed test specimen designed to investigate migration of a delamination between neighboring ply interfaces in tape laminates is presented. The specimen is a cross-ply laminated beam consisting of 40 plies with a polytetrafluoroethylene insert spanning part way along its length. The insert is located between a lower 0-degree ply (specimen length direction) and a stack of four 90-degree plies (specimen width direction). The modification involved a stacking sequence that promotes stable delamination growth prior to migration, and included a relocation of the insert from the specimen midplane to the interface between plies 14 and 15. Specimens were clamped at both ends onto a rigid baseplate and loaded on their upper surface via a piano hinge assembly, resulting in a predominantly flexural loading condition. Tests were conducted with the load-application point positioned at various locations along a specimen's span. This position affected the sequence of damage events during a test.

  10. Flutter and buckling of general laminated plates

    NASA Technical Reports Server (NTRS)

    Sawyer, J. W.

    1976-01-01

    An anisotropic buckling and flutter analysis is developed with allowance for both bending-extensional coupling and bending-twisting coupling within the framework of linear small deflection theory for simply supported general laminated plates. The extended Galerkin method is used to obtain approximate solutions to the coupled governing equations. The effects of various anisotropic stiffness parameters on the static and dynamic stability of laminated plates are evaluated, with particular emphasis on assessing the range of applicability of classical orthotropic plate theory. It is shown that bending-extensional coupling and bending-twisting stiffness terms have a destabilizing effect on buckling and flutter, the effect being more pronounced for a small number of layers. For symmetric plates, the number of layers required for orthotropic plate theory to be applicable is generally less for the buckling problem than for flutter. For square plates, aligning the fibers with the direction of airflow over the plate surface results in the highest flutter dynamic pressure.

  11. Laminated grid and web magnetic cores

    DOEpatents

    Sefko, John; Pavlik, Norman M.

    1984-01-01

    A laminated magnetic core characterized by an electromagnetic core having core legs which comprise elongated apertures and edge notches disposed transversely to the longitudinal axis of the legs, such as high reluctance cores with linear magnetization characteristics for high voltage shunt reactors. In one embodiment the apertures include compact bodies of microlaminations for more flexibility and control in adjusting permeability and/or core reluctance.

  12. Residual stresses in polymer matrix composite laminates

    NASA Technical Reports Server (NTRS)

    Hahn, H. T.

    1976-01-01

    Residual stresses in composites are induced during fabrication and by environmental exposure. The theory formulated can describe the shrinkage commonly observed after a thermal expansion test. Comparison between the analysis and experimental data for laminates of various material systems indicates that the residual stress-free temperature can be lower than the curing temperature, depending on the curing process. Effects of residual stresses on ply failure including the acoustic emission characteristics are discussed.

  13. A refined theory for laminated anisotropic plates

    NASA Astrophysics Data System (ADS)

    Cai, Si-Wei; Cai, Min

    A theory for bending of laminated plates has been developed. This high-order theory is different from the classic high-order theory in two respects: (1) both the stresses and displacements between layers of the plate are continuous in this theory; and (2) the governing equations as well as the unknown functions in this theory are five in number only. Accuracy is ascertained by comparing solutions from the present theory with the exact theory of elasticity.

  14. Natural vibrations of laminated anisotropic plates

    NASA Technical Reports Server (NTRS)

    Reddy, J. N.; Kuppusamy, T.

    1984-01-01

    This paper contains a description of the three-dimensional elasticity equations and the associated finite element model for natural vibrations of laminated rectangular plates. The numerical results for natural frequencies are compared with those obtained by a shear deformable plate theory. A number of cross-ply and angle-ply rectangular plates are analyzed for natural frequencies. For relatively thick plates, the plate element predicts frequencies higher than those predicted by the 3-D element.

  15. Scaling effects in angle-ply laminates

    NASA Technical Reports Server (NTRS)

    Kellas, Sotiris; Morton, John

    1992-01-01

    The effect of specimen size upon the response and strength of +/- 45 degree angle-ply laminates was investigated for two graphite fiber reinforced plastic systems and several stacking sequences. The first material system was a brittle epoxy based system, AS4 fibers in 3502 epoxy, and the second was a tough thermoplastic based system, AS4 fibers in PEEK matrix. For the epoxy based system, two generic +/- 45 degree lay-ups were studied: (+45 degrees sub n/-45 degrees sub n) sub 2S (blocked plies), and (+45 degrees/-45 degrees) sub 2nS, for n=1 and 2. The in-plane dimensions of the specimens were varied such that the width/length relationship was 12.7 x n/127 x n mm, for m=1, 2, 3, or 4. It is shown that the stress/strain response and the ultimate strength of these angle-ply laminates depends on the laminate thickness and the type of generic lay-up used. Furthermore, it is shown that first ply failure occurs in the surface plies as a result of normal rather than shear stresses. The implications of the experimental findings upon the validity of the +/- 45 degree tensile test which is used to determine the in-plane shear response of unidirectional composites are discussed.

  16. Superconductivity in Ca-doped graphene laminates

    PubMed Central

    Chapman, J.; Su, Y.; Howard, C. A.; Kundys, D.; Grigorenko, A. N.; Guinea, F.; Geim, A. K.; Grigorieva, I. V.; Nair, R. R.

    2016-01-01

    Despite graphene’s long list of exceptional electronic properties and many theoretical predictions regarding the possibility of superconductivity in graphene, its direct and unambiguous experimental observation has not been achieved. We searched for superconductivity in weakly interacting, metal decorated graphene crystals assembled into so-called graphene laminates, consisting of well separated and electronically decoupled graphene crystallites. We report robust superconductivity in all Ca-doped graphene laminates. They become superconducting at temperatures (Tc) between ≈4 and ≈6 K, with Tc’s strongly dependent on the confinement of the Ca layer and the induced charge carrier concentration in graphene. We find that Ca is the only dopant that induces superconductivity in graphene laminates above 1.8 K among several dopants used in our experiments, such as potassium, caesium and lithium. By revealing the tunability of the superconducting response through doping and confinement of the metal layer, our work shows that achieving superconductivity in free-standing, metal decorated monolayer graphene is conditional on an optimum confinement of the metal layer and sufficient doping, thereby bringing its experimental realization within grasp. PMID:26979564

  17. Eastern Guaymas Basin: laminated but not anoxic

    NASA Astrophysics Data System (ADS)

    Cheshire, H.; Thurow, J. W.

    2009-12-01

    Site MD02-2513, eastern Guaymas Basin, challenges the accepted hypothesis about the circumstances and sequence of events leading to the occurrence of annually laminated (varved) sediment. By convention, under a climate regime of strong seasonal contrast, high productivity in a restricted basin enhances a preformed OMZ and inhibits bioturbation, resulting in the preservation of varves. The comparison of the high-resolution log of the sediment fabric and continuous XRF data from Core MD02-2513 reveal that laminated intervals over the last ~90 ka BP are characterised by an increase of oxygenation above background levels and are accompanied by lows of terrestrial and biogenic flux indicating that the preserving factor is rapid burial rather than high sedimentation rate (ie high seasonality and low rainfall). Intervals of diffuse/discontinuous laminations are times of high terrestrial and biogenic flux indicating comparatively low seasonality and high rainfall. Brief periods of relatively high anoxic conditions occur within homogeneous intervals and are accompanied by exceptionally high biogenic flux, indicating there was no seasonal contrast. Long homogenous intervals occur during the last glacial due to lowered sea level and the consequent removal of the upwelling cell offshore. The changes in Guaymas Basin seasonality are most probably caused by alterations to the migration pattern of the North Pacific Subtropical High due to the growth and decay of the North American ice sheets.

  18. Modeling Composite Laminate Crushing for Crash Analysis

    NASA Technical Reports Server (NTRS)

    Fleming, David C.; Jones, Lisa (Technical Monitor)

    2002-01-01

    Crash modeling of composite structures remains limited in application and has not been effectively demonstrated as a predictive tool. While the global response of composite structures may be well modeled, when composite structures act as energy-absorbing members through direct laminate crushing the modeling accuracy is greatly reduced. The most efficient composite energy absorbing structures, in terms of energy absorbed per unit mass, are those that absorb energy through a complex progressive crushing response in which fiber and matrix fractures on a small scale dominate the behavior. Such failure modes simultaneously include delamination of plies, failure of the matrix to produce fiber bundles, and subsequent failure of fiber bundles either in bending or in shear. In addition, the response may include the significant action of friction, both internally (between delaminated plies or fiber bundles) or externally (between the laminate and the crushing surface). A figure shows the crushing damage observed in a fiberglass composite tube specimen, illustrating the complexity of the response. To achieve a finite element model of such complex behavior is an extremely challenging problem. A practical crushing model based on detailed modeling of the physical mechanisms of crushing behavior is not expected in the foreseeable future. The present research describes attempts to model composite crushing behavior using a novel hybrid modeling procedure. Experimental testing is done is support of the modeling efforts, and a test specimen is developed to provide data for validating laminate crushing models.

  19. Superconductivity in Ca-doped graphene laminates.

    PubMed

    Chapman, J; Su, Y; Howard, C A; Kundys, D; Grigorenko, A N; Guinea, F; Geim, A K; Grigorieva, I V; Nair, R R

    2016-01-01

    Despite graphene's long list of exceptional electronic properties and many theoretical predictions regarding the possibility of superconductivity in graphene, its direct and unambiguous experimental observation has not been achieved. We searched for superconductivity in weakly interacting, metal decorated graphene crystals assembled into so-called graphene laminates, consisting of well separated and electronically decoupled graphene crystallites. We report robust superconductivity in all Ca-doped graphene laminates. They become superconducting at temperatures (Tc) between ≈4 and ≈6 K, with Tc's strongly dependent on the confinement of the Ca layer and the induced charge carrier concentration in graphene. We find that Ca is the only dopant that induces superconductivity in graphene laminates above 1.8 K among several dopants used in our experiments, such as potassium, caesium and lithium. By revealing the tunability of the superconducting response through doping and confinement of the metal layer, our work shows that achieving superconductivity in free-standing, metal decorated monolayer graphene is conditional on an optimum confinement of the metal layer and sufficient doping, thereby bringing its experimental realization within grasp. PMID:26979564

  20. Impact of nonlinear laminated composite plates

    SciTech Connect

    Kam, T.Y.; Chao, T.N.; Lai, F.M.

    1996-10-01

    Laminated composite materials have many superior properties which have made them become an important engineering material for industrial applications. Many energy related structures or components such as off-shore drilling platforms, turban blades, pressure vessels, pipes, etc., which are usually modelled as plate structures in analysis, have been designed using composite materials. In general, these structures or components, which require high reliability, are operated in severe environments and susceptible to low-speed impact by foreign objects. Here, the dynamic response of nonlinear laminated composite plates subject to low-speed impact is studied using the von Karman-Mindin plate theory. The equations of motion of the impactor and the plate are derived via a virtual work approach. The contact force between the impactor and the plate is calculated by using an experimentally established contact law. The accuracy of the method for impact analysis is verified by experimental results as well as the theoretical results available in the literature. The discrepancies between the results predicted by the linear and nonlinear plate theories are investigated. Optimal layups of laminates for minimizing dynamic response via the present method and a global optimization technique are presented.

  1. Characteristics of laminates with delamination control strips

    SciTech Connect

    Sun, C.T.; Goering, J.C.; Alper, J.M.; Gause, L.W.

    1992-09-01

    Tough resin is needed to resist delamination crack propagation. However, modulus often has to be compromised because it is difficult to retain both high modulus and toughness in a matrix material. A potential solution is to use a hybrid system in which tough resin strips are included within a conventional matrix composite. By adjusting the spacing of the tough resin strips, maximum delamination size can be controlled. Experimental results for impact damage and subsequent damage propagation in laminates containing tough resin strips are reported. Plain adhesive strips and fiber-reinforced tough resin composite strips were used in constructing the hybrid laminates. Test results indicated that size of delamination inflicted by impact was confined between the tough resin strips. As a result, significantly increased residual compressive strength was obtained. Impacted laminates containing tough resin strips were also fatigue tested. It was found that these strips reduced the growth of the impact damage area relative to the growth seen in coupons with no tough resin strips. Damage growth from an open hole under tension fatigue was evaluated using both tough resin strips and glass fiber reinforced tough resin strips. Unreinforced tough resin strips retarded delamination growth from the open hole, but did not stop matrix cracks growing in the fiber direction. Fiber reinforced tough resin strips did not contain axial delamination growth from the open hole. However, they did act as crack arresters, stopping the through-the-thickness tension crack originating from the hole.

  2. Laminate articles on biaxially textured metal substrates

    DOEpatents

    Beach, David B.; Morrell, Jonathan S.; Paranthaman, Mariappan; Chirayil, Thomas; Specht, Eliot D.; Goyal, Amit

    2003-12-16

    A laminate article comprises a substrate and a biaxially textured (RE.sup.1.sub.x RE.sup.2.sub.(1-x)).sub.2 O.sub.3 buffer layer over the substrate, wherein 0laminate article can include a layer of YBCO over the (RE.sup.1.sub.x RE.sup.2.sub.(1-x)).sub.2 O.sub.3 buffer layer. A layer of CeO.sub.2 between the YBCO layer and the (RE.sup.1.sub.x RE.sup.2.sub.(1-x)).sub.2 O.sub.3 buffer can also be include. Further included can be a layer of YSZ between the CeO.sub.2 layer and the (R.sup.1.sub.x RE.sup.2.sub.(1-x)).sub.2 O.sub.3 buffer layer. The substrate can be a biaxially textured metal, such as nickel. A method of forming the laminate article is also disclosed.

  3. Characteristics of laminates with delamination control strips

    NASA Technical Reports Server (NTRS)

    Sun, C. T.; Goering, J. C.; Alper, J. M.; Gause, L. W.

    1992-01-01

    Tough resin is needed to resist delamination crack propagation. However, modulus often has to be compromised because it is difficult to retain both high modulus and toughness in a matrix material. A potential solution is to use a hybrid system in which tough resin strips are included within a conventional matrix composite. By adjusting the spacing of the tough resin strips, maximum delamination size can be controlled. Experimental results for impact damage and subsequent damage propagation in laminates containing tough resin strips are reported. Plain adhesive strips and fiber-reinforced tough resin composite strips were used in constructing the hybrid laminates. Test results indicated that size of delamination inflicted by impact was confined between the tough resin strips. As a result, significantly increased residual compressive strength was obtained. Impacted laminates containing tough resin strips were also fatigue tested. It was found that these strips reduced the growth of the impact damage area relative to the growth seen in coupons with no tough resin strips. Damage growth from an open hole under tension fatigue was evaluated using both tough resin strips and glass fiber reinforced tough resin strips. Unreinforced tough resin strips retarded delamination growth from the open hole, but did not stop matrix cracks growing in the fiber direction. Fiber reinforced tough resin strips did not contain axial delamination growth from the open hole. However, they did act as crack arresters, stopping the through-the-thickness tension crack originating from the hole.

  4. The prevalence of endocrinopathic laminitis among horses presented for laminitis at a first-opinion/referral equine hospital.

    PubMed

    Karikoski, N P; Horn, I; McGowan, T W; McGowan, C M

    2011-10-01

    Endocrinopathic causes of laminitis may be a common underlying causative pathogenesis in first-opinion or field cases presenting with laminitis, as opposed to laminitis produced in inflammatory research models. This study aimed to determine whether evidence of an underlying endocrinopathy was present in horses presented for laminitis to a first-opinion/referral veterinary teaching hospital. A second aim was to compare the signalment of horses and ponies with laminitis with the equine hospital population during the same period. All horses presenting for laminitis at Helsinki University Equine Teaching Hospital, Finland, over a 16-month period were examined for an underlying endocrinopathy. Horses presenting for laminitis were compared with the hospitalized population over the same period. There were 36 horses presented for laminitis, and evidence of endocrinopathy was present in 89%. Of the horses showing an underlying endocrinopathy, one-third had a diagnosis of pituitary pars intermedia dysfunction, and two-thirds showed basal hyperinsulinemia indicative of insulin resistance, without evidence of hirsutism. Phenotypic indicators of obesity were present in 95% of horses with basal hyperinsulinemia without hirsutism. Compared with the hospital population during the same period, horses with laminitis associated with an underlying endocrinopathy were significantly older and more likely to be pony breeds. Our data support that endocrine testing should be performed on all cases of laminitis that do not have a clear inflammatory or gastrointestinal origin. PMID:21696910

  5. Tailored metal matrix laminates for high-temperature performance

    NASA Technical Reports Server (NTRS)

    Morei, Michael R.; Saravanos, Dimitris A.; Chamis, C. C.

    1992-01-01

    A multi-objective tailoring methodology is presented to maximize stiffness and load carrying capacity of a metal matrix cross-ply laminated at elevated temperatures. The fabrication process and fiber volume ratio are used as the design variables. A unique feature is the concurrent effects from fabrication, residual stresses, material nonlinearity, and thermo-mechanical loading on the laminate properties at the post-fabrication phase. For a (0.90) (sub s) graphite/copper laminate, strong coupling was observed between the fabrication process, laminate characteristics, and thermo-mechanical loading. The multi-objective tailoring was found to be more effective than single objective tailoring. Results indicate the potential to increase laminate stiffness and load carrying capacity by controlling the critical parameters of the fabrication process and the laminate.

  6. Improved damage tolerance of titanium by adhesive lamination

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.

    1982-01-01

    Basic damage tolerance properties of Ti-6A1-4V titanium plate can be improved by laminating thin sheets of titanium with adhesives. Compact tension and center cracked tension specimens made from thick plate, thin sheet, and laminated plate (six plies of thin sheet) were tested. The fracture toughness of the laminated plate was 39 percent higher than the monolithic plate. The laminated plate's through the thickness crack growth rate was about 20 percent less than that of the monolithic plate. The damage tolerance life of the surface cracked laminate was 6 to over 15 times the life of a monolithic specimen. A simple method of predicting crack growth in a crack ply of a laminate is presented.

  7. Residual stress and fracture of laminated ceramic membranes

    SciTech Connect

    Atkinson, A.; Selcuk, A.

    1999-02-05

    Bilayer laminated ceramic membranes were produced comprising a layer of gadolinia-doped ceria (CGO) 180 {micro}m thick and a layer of yttria-stabilized zirconia (YSZ) 5 {micro}m thick. The residual stresses in the laminates at room temperature were estimated from their curvature and the elastic constants of the individual layers. The fracture of the laminates was studied in biaxial flexure at 35 and 800 C. The mean failure stress in the CGO in the laminates was much greater than in unlaminated CGO. This is due partly to an improved microstructure from the lamination process and partly to the restraint of the compressively stressed YSZ. The combined effects of higher failure stress and residual stresses lead to the laminated membranes having higher apparent strength than single layer CGO membranes by factors of between 1.75 and 4.06.

  8. Molecular Detection of a Potentially Toxic Diatom Species

    PubMed Central

    Dhar, Bidhan Chandra; Cimarelli, Lucia; Singh, Kumar Saurabh; Brandi, Letizia; Brandi, Anna; Puccinelli, Camilla; Marcheggiani, Stefania; Spurio, Roberto

    2015-01-01

    A few diatom species produce toxins that affect human and animal health. Among these, members of the Pseudo-nitzschia genus were the first diatoms unambiguously identified as producer of domoic acid, a neurotoxin affecting molluscan shell-fish, birds, marine mammals, and humans. Evidence exists indicating the involvement of another diatom genus, Amphora, as a potential producer of domoic acid. We present a strategy for the detection of the diatom species Amphora coffeaeformis based on the development of species-specific oligonucleotide probes and their application in microarray hybridization experiments. This approach is based on the use of two marker genes highly conserved in all diatoms, but endowed with sufficient genetic divergence to discriminate diatoms at the species level. A region of approximately 450 bp of these previously unexplored marker genes, coding for elongation factor 1-a (eEF1-a) and silicic acid transporter (SIT), was used to design oligonucleotide probes that were tested for specificity in combination with the corresponding fluorescently labeled DNA targets. The results presented in this work suggest a possible use of this DNA chip technology for the selective detection of A. coffeaeformis in environmental settings where the presence of this potential toxin producer may represent a threat to human and animal health. In addition, the same basic approach can be adapted to a wider range of diatoms for the simultaneous detection of microorganisms used as biomarkers of different water quality levels. PMID:25955528

  9. Microbial control of diatom bloom dynamics in the open ocean

    NASA Astrophysics Data System (ADS)

    Boyd, Philip W.; Strzepek, Robert; Chiswell, Steve; Chang, Hoe; DeBruyn, Jennifer M.; Ellwood, Michael; Keenan, Sean; King, Andrew L.; Maas, Elisabeth W.; Nodder, Scott; Sander, Sylvia G.; Sutton, Philip; Twining, Benjamin S.; Wilhelm, Steven W.; Hutchins, David A.

    2012-09-01

    Diatom blooms play a central role in supporting foodwebs and sequestering biogenic carbon to depth. Oceanic conditions set bloom initiation, whereas both environmental and ecological factors determine bloom magnitude and longevity. Our study reveals another fundamental determinant of bloom dynamics. A diatom spring bloom in offshore New Zealand waters was likely terminated by iron limitation, even though diatoms consumed <1/3 of the mixed-layer dissolved iron inventory. Thus, bloom duration and magnitude were primarily set by competition for dissolved iron between microbes and small phytoplankton versus diatoms. Significantly, such a microbial mode of control probably relies both upon out-competing diatoms for iron (i.e., K-strategy), and having high iron requirements (i.e., r-strategy). Such resource competition for iron has implications for carbon biogeochemistry, as, blooming diatoms fixed three-fold more carbon per unit iron than resident non-blooming microbes. Microbial sequestration of iron has major ramifications for determining the biogeochemical imprint of oceanic diatom blooms.

  10. Diatoms in forensic analysis: A practical approach in rats.

    PubMed

    Badu, Isaac K; Girela, Eloy; Beltrn, Cristina M; Ruz-Caracuel, Ignacio; Jimena, Ignacio

    2015-07-01

    A diagnosis of drowning is a challenge in legal medicine, as there is generally a lack of pathognomonic findings indicative of drowning. Diatom analysis has been considered very supportive for a diagnosis of drowning, although the test is still controversial for some investigators. We assessed diatoms association with drowning in the peripheral tissues of drowned rats and the effects of the drowning medium on the diatom yield. A modified acid digestion method was optimised for diatom recovery in water and rat tissues. Eighteen adult Wistar rats were employed for the study, subdivided into six groups of three rats. Groups 1, 3 and 5 were drowned in seawater, lake water, or river water respectively, while groups 2, 4 and 6 were controls (immersed after death in seawater, lake water or river water respectively). Water samples were taken from the sea, lake and river in Mlaga and Crdoba (Spain) for the purposes of diatomological mapping and drowning of the rats. Diatoms were successfully recovered from all water samples and matched with tissues of the drowned rats. There were significant differences in diatom numbers between control and test samples for all the tissues studied, as well as within test samples. Histological investigations conducted on lung samples obtained from drowned rats provided complementary and valuable information. This study demonstrates the feasibility of the diatom test as a reliable method for the diagnosis of drowning, especially if adequate precautions are taken to avoid contamination, and if interpretation of the analysis is performed in light of other complementary investigations. PMID:24966336

  11. Molecular detection of a potentially toxic diatom species.

    PubMed

    Dhar, Bidhan Chandra; Cimarelli, Lucia; Singh, Kumar Saurabh; Brandi, Letizia; Brandi, Anna; Puccinelli, Camilla; Marcheggiani, Stefania; Spurio, Roberto

    2015-05-01

    A few diatom species produce toxins that affect human and animal health. Among these, members of the Pseudo-nitzschia genus were the first diatoms unambiguously identified as producer of domoic acid, a neurotoxin affecting molluscan shell-fish, birds, marine mammals, and humans. Evidence exists indicating the involvement of another diatom genus, Amphora, as a potential producer of domoic acid. We present a strategy for the detection of the diatom species Amphora coffeaeformis based on the development of species-specific oligonucleotide probes and their application in microarray hybridization experiments. This approach is based on the use of two marker genes highly conserved in all diatoms, but endowed with sufficient genetic divergence to discriminate diatoms at the species level. A region of approximately 450 bp of these previously unexplored marker genes, coding for elongation factor 1-a (eEF1-a) and silicic acid transporter (SIT), was used to design oligonucleotide probes that were tested for specificity in combination with the corresponding fluorescently labeled DNA targets. The results presented in this work suggest a possible use of this DNA chip technology for the selective detection of A. coffeaeformis in environmental settings where the presence of this potential toxin producer may represent a threat to human and animal health. In addition, the same basic approach can be adapted to a wider range of diatoms for the simultaneous detection of microorganisms used as biomarkers of different water quality levels. PMID:25955528

  12. Copepod Population-Specific Response to a Toxic Diatom Diet

    PubMed Central

    Lauritano, Chiara; Carotenuto, Ylenia; Miralto, Antonio; Procaccini, Gabriele; Ianora, Adrianna

    2012-01-01

    Diatoms are key phytoplankton organisms and one of the main primary producers in aquatic ecosystems. However, many diatom species produce a series of secondary metabolites, collectively termed oxylipins, that disrupt development in the offspring of grazers, such as copepods, that feed on these unicellular algae. We hypothesized that different populations of copepods may deal differently with the same oxylipin-producing diatom diet. Here we provide comparative studies of expression level analyses of selected genes of interest for three Calanus helgolandicus populations (North Sea, Atlantic Ocean and Mediterranean Sea) exposed to the same strain of the oxylipin-producing diatom Skeletonema marinoi using as control algae the flagellate Rhodomonas baltica. Expression levels of detoxification enzymes and stress proteins (e.g. glutathione S-transferase, glutathione synthase, superoxide dismutase, catalase, aldehyde dehydrogenases and heat shock proteins) and proteins involved in apoptosis regulation and cell cycle progression were analyzed in copepods after both 24 and 48 hours of feeding on the diatom or on a control diet. Strong differences occurred among copepod populations, with the Mediterranean population of C. helgolandicus being more susceptible to the toxic diet compared to the others. This study opens new perspectives for understanding copepod population-specific responses to diatom toxins and may help in underpinning the cellular mechanisms underlying copepod toxicity during diatom blooms. PMID:23056617

  13. Self-assembled diatom substrates with plasmonic functionality

    NASA Astrophysics Data System (ADS)

    Kwon, Sun Yong; Park, Sehyun; Nichols, William T.

    2014-04-01

    Marine diatoms have an exquisitely complex exoskeleton that is promising for engineered surfaces such as sensors and catalysts. For such applications, creating uniform arrays of diatom frustules across centimeter scales will be necessary. Here, we present a simple, low-cost floating interface technique to self-assemble the diatom frustules. We show that well-prepared diatoms form floating hexagonal close-packed arrays at the air-water interface that can be transferred directly to a substrate. We functionalize the assembled diatom surfaces with gold and characterize the plasmonic functionality by using surface enhanced Raman scattering (SERS). Thin gold films conform to the complex, hierarchical diatom structure and produce a SERS enhancement factor of 2 104. Small gold nanoparticles attached to the diatom's surface produce a higher enhancement of 7 104 due to stronger localization of the surface plasmons. Taken together, the large-scale assembly and plasmonic functionalization represent a promising platform to control the energy and the material flows at a complex surface for applications such as sensors and plasmonic enhanced catalysts.

  14. Metatranscriptome analyses indicate resource partitioning between diatoms in the field.

    PubMed

    Alexander, Harriet; Jenkins, Bethany D; Rynearson, Tatiana A; Dyhrman, Sonya T

    2015-04-28

    Diverse communities of marine phytoplankton carry out half of global primary production. The vast diversity of the phytoplankton has long perplexed ecologists because these organisms coexist in an isotropic environment while competing for the same basic resources (e.g., inorganic nutrients). Differential niche partitioning of resources is one hypothesis to explain this "paradox of the plankton," but it is difficult to quantify and track variation in phytoplankton metabolism in situ. Here, we use quantitative metatranscriptome analyses to examine pathways of nitrogen (N) and phosphorus (P) metabolism in diatoms that cooccur regularly in an estuary on the east coast of the United States (Narragansett Bay). Expression of known N and P metabolic pathways varied between diatoms, indicating apparent differences in resource utilization capacity that may prevent direct competition. Nutrient amendment incubations skewed N/P ratios, elucidating nutrient-responsive patterns of expression and facilitating a quantitative comparison between diatoms. The resource-responsive (RR) gene sets deviated in composition from the metabolic profile of the organism, being enriched in genes associated with N and P metabolism. Expression of the RR gene set varied over time and differed significantly between diatoms, resulting in opposite transcriptional responses to the same environment. Apparent differences in metabolic capacity and the expression of that capacity in the environment suggest that diatom-specific resource partitioning was occurring in Narragansett Bay. This high-resolution approach highlights the molecular underpinnings of diatom resource utilization and how cooccurring diatoms adjust their cellular physiology to partition their niche space. PMID:25870299

  15. Diatom assemblages promote ice formation in large lakes

    PubMed Central

    D'souza, N A; Kawarasaki, Y; Gantz, J D; Lee, R E; Beall, B F N; Shtarkman, Y M; Koer, Z A; Rogers, S O; Wildschutte, H; Bullerjahn, G S; McKay, R M L

    2013-01-01

    We present evidence for the directed formation of ice by planktonic communities dominated by filamentous diatoms sampled from the ice-covered Laurentian Great Lakes. We hypothesize that ice formation promotes attachment of these non-motile phytoplankton to overlying ice, thereby maintaining a favorable position for the diatoms in the photic zone. However, it is unclear whether the diatoms themselves are responsible for ice nucleation. Scanning electron microscopy revealed associations of bacterial epiphytes with the dominant diatoms of the phytoplankton assemblage, and bacteria isolated from the phytoplankton showed elevated temperatures of crystallization (Tc) as high as ?3?C. Ice nucleation-active bacteria were identified as belonging to the genus Pseudomonas, but we could not demonstrate that they were sufficiently abundant to incite the observed freezing. Regardless of the source of ice nucleation activity, the resulting production of frazil ice may provide a means for the diatoms to be recruited to the overlying lake ice, thereby increasing their fitness. Bacterial epiphytes are likewise expected to benefit from their association with the diatoms as recipients of organic carbon excreted by their hosts. This novel mechanism illuminates a previously undescribed stage of the life cycle of the meroplanktonic diatoms that bloom in Lake Erie and other Great Lakes during winter and offers a model relevant to aquatic ecosystems having seasonal ice cover around the world. PMID:23552624

  16. Diatom (Bacillariophyta) community response to water quality and land use

    USGS Publications Warehouse

    Stewart, Paul M.; Butcher, Jason T.; Gerovac, Paul J.

    1999-01-01

    Aquatic algal communities are sensitive to environmental stresses and are used as indicators of water quality. Diatoms were collected from three streams that drain the Great Marsh at Indiana Dunes National Lakeshore. Diatom communities, water chemistry, and land use were measured at each site to test the hypothesis that differences in land use indirectly affect diatom communities, through changes in water quality. Relationships among these variables were examined by correlation, cluster, and detrended correspondence analysis. Several water chemistry variables were correlated to several land-use categories. Diatom species diversity was most variable in disturbed areas with poorer water quality and was correlated with land use and total alkalinity, total hardness, and specific conductance. Sites within each stream were grouped in terms of their diatom assemblage by both cluster and detrended correspondence analysis with but two exceptions in Dunes Creek. Diatom communities in the three streams responded to land use through its effects on water quality. The results of this study demonstrate the use of diatom assemblages as indicators of water quality, which can be linked to land use in a watershed.

  17. Diatom assemblages promote ice formation in large lakes.

    PubMed

    D'souza, N A; Kawarasaki, Y; Gantz, J D; Lee, R E; Beall, B F N; Shtarkman, Y M; Koer, Z A; Rogers, S O; Wildschutte, H; Bullerjahn, G S; McKay, R M L

    2013-08-01

    We present evidence for the directed formation of ice by planktonic communities dominated by filamentous diatoms sampled from the ice-covered Laurentian Great Lakes. We hypothesize that ice formation promotes attachment of these non-motile phytoplankton to overlying ice, thereby maintaining a favorable position for the diatoms in the photic zone. However, it is unclear whether the diatoms themselves are responsible for ice nucleation. Scanning electron microscopy revealed associations of bacterial epiphytes with the dominant diatoms of the phytoplankton assemblage, and bacteria isolated from the phytoplankton showed elevated temperatures of crystallization (T(c)) as high as -3 C. Ice nucleation-active bacteria were identified as belonging to the genus Pseudomonas, but we could not demonstrate that they were sufficiently abundant to incite the observed freezing. Regardless of the source of ice nucleation activity, the resulting production of frazil ice may provide a means for the diatoms to be recruited to the overlying lake ice, thereby increasing their fitness. Bacterial epiphytes are likewise expected to benefit from their association with the diatoms as recipients of organic carbon excreted by their hosts. This novel mechanism illuminates a previously undescribed stage of the life cycle of the meroplanktonic diatoms that bloom in Lake Erie and other Great Lakes during winter and offers a model relevant to aquatic ecosystems having seasonal ice cover around the world. PMID:23552624

  18. A peculiar lamin in a peculiar mammal: Expression of lamin LIII in platypus (Ornithorhynchus anatinus).

    PubMed

    Peter, Annette; Khandekar, Shaunak; Deakin, Janine E; Stick, Reimer

    2015-11-01

    Platypus (Ornithorhynchus anatinus) holds a unique phylogenetic position at the base of the mammalian lineage due to an amalgamation of mammalian and sauropsid-like features. Here we describe the set of four lamin genes for platypus. Lamins are major components of the nuclear lamina, which constitutes a main component of the nucleoskeleton and is involved in a wide range of nuclear functions. Vertebrate evolution was accompanied by an increase in the number of lamin genes from a single gene in their closest relatives, the tunicates and cephalochordates, to four genes in the vertebrate lineage. Of the four genes the LIII gene is characterized by the presence of two alternatively spliced CaaX-encoding exons. In amphibians and fish LIII is the major lamin protein in oocytes and early embryos. The LIII gene is conserved throughout the vertebrate lineage, with the notable exception of marsupials and placental mammals, which have lost the LIII gene. Here we show that platypus has retained an LIII gene, albeit with a significantly altered structure and with a radically different expression pattern. The platypus LIII gene contains only a single CaaX-encoding exon and the head domain together with coil 1a and part of coil1b of the platypus LIII protein is replaced by a novel short non-helical N-terminus. It is expressed exclusively in the testis. These features resemble those of male germ cell-specific lamins in placental mammals, in particular those of lamin C2. Our data suggest (i) that the specific functions of LIII, which it fulfills in all other vertebrates, is no longer required in mammals and (ii) once it had been freed from these functions has undergone structural alterations and has adopted a new functionality in monotremes. PMID:26213206

  19. The Laminated Marca Shale: High-Frequency Climate Cycles From the Latest Cretaceous

    NASA Astrophysics Data System (ADS)

    Davies, A.; Kemp, A. E.; Weedon, G.; Barron, J. A.

    2005-12-01

    The Latest Cretaceous (Maastrichtian) Marca Shale Member, California, displays a well-preserved record of alternating terrigenous and diatomaceous laminae couplets, remarkably similar in lithology to recent laminated sediments from the Gulf of California and Santa Barbara Basin. This similarity, together with the recognition of intra- and inter-annual variability in the diatom flora, implies an annual origin for these couplets. High-resolution backscattered electron imagery has identified two sublaminae types within the varved succession; near monospecific lamina of Chaetoceros-type resting spore and of large Azpeitiopsis morenoensis. The composition and occurrence of these laminae is similar to ENSO forced intra-annual variability of diatom flora along the modern Californian margin. Relative thickness variations in terrigenous and biogenic laminae (proxies for precipitation and productivity respectively) also exhibit similar characteristics to variability in Quaternary varves from the Santa Barbara Basin, shown to be imparted by ENSO forcing. In order to track changes in the levels of bottom water oxygenation within the basin, a bioturbation index was established. Periods when bioturbation was minimal (enhanced benthic anoxia) coincide with times of greatest diatomaceous export flux and also lowest flux of detrital material. Conversely, periods of enhanced bioturbation correspond with reduced diatomaceous export flux and an increased flux of detrital material, comparable with ENSO forced variations in diatomaceous and terrigenous export flux and associated benthic oxygenation levels in Pleistocene varves off the Californian margin. Power spectra obtained from time-series analysis of the bioturbation index and laminae thickness variations exhibit strong signals within the ENSO band. This research implies that high-frequency climate perturbations are inherent components of the climate system and that ENSO-type variability was not confined to the dynamic climate system of the Quaternary, but occurred as far back as the Cretaceous. These results also add to the growing body of evidence which indicate that warm end-member climate states are not characterised by a permanent El Nino state.

  20. Tension fatigue analysis and life prediction for composite laminates

    NASA Technical Reports Server (NTRS)

    O'Brien, T. K.; Rigamonti, M.; Zanotti, C.

    1989-01-01

    A methodology is presented for the tension fatigue analysis and life prediction of composite laminates subjected to tension fatigue loading. The methodology incorporates both the generic fracture mechanics characterization of delamination and the assessment of the infuence of damage on laminate fatigue life. Tension fatigue tests were conducted on quasi-isotropic and orthotropic glass epoxy, graphite epoxy, and glass/graphite epoxy hybrid laminates, demonstrating good agreement between measured and predicted lives.

  1. Non-linear behavior of fiber composite laminates

    NASA Technical Reports Server (NTRS)

    Hashin, Z.; Bagchi, D.; Rosen, B. W.

    1974-01-01

    The non-linear behavior of fiber composite laminates which results from lamina non-linear characteristics was examined. The analysis uses a Ramberg-Osgood representation of the lamina transverse and shear stress strain curves in conjunction with deformation theory to describe the resultant laminate non-linear behavior. A laminate having an arbitrary number of oriented layers and subjected to a general state of membrane stress was treated. Parametric results and comparison with experimental data and prior theoretical results are presented.

  2. Fracture behavior of thick, laminated graphite/epoxy composites

    NASA Technical Reports Server (NTRS)

    Harris, C. E.; Morris, D. H.

    1984-01-01

    The effect of laminate thickness on the fracture behavior of laminated graphite epoxy (T300/5208) composites was studied. The predominantly experimental research program included the study of the 0/+ or - 45/90 sub ns and 0/90 sub ns laminates with thickness of 8, 32, 64, 96 and 120 plies and the 0/+ or - 45 sub ns laminate with thickness of 6, 30, 60, 90 and 120 plies. The research concentrated on the measurement of fracture toughness utilizing the center-cracked tension, compact tension and three point bend specimen configurations. The development of subcritical damage at the crack tip was studied nondestructively using enhanced X-ray radiography and destructively using the laminate deply technique. The test results showed fracture toughness to be a function of laminate thickness. The fracture toughness of the 0 + or - 45/90 sub ns and 0/90 sub ns laminates decreased with increasing thickness and asymptotically approached lower bound values of 30 ksi square root of in. (1043 MPa square root of mm and 25 ksi square root of in (869 MPa square root of mm respectively. In contrast to the other two laminates, the fracture toughness of the 0/+ or - 45 sub ns laminate increased sharply with increasing thickness but reached an upper plateau value of 40 ksi square root of in (1390 MPa square root of mm) at 30 plies. Fracture toughness was independent of crack size for both thin and thick laminates for all three laminate types except for the 0/90 sub 2s laminate which spilt extensively. The center cracked tension, three point bend and compact tension specimens gave comparable results.

  3. Energy Saving Glass Lamination via Selective Radio-Frequency Heating

    SciTech Connect

    Shulman, Holly S.; Allan, Shawn M.

    2009-11-11

    This Inventions and Innovations program supported the technical and commercial research and development needed to elevate Ceralink's energy saving process for flat glass lamination from bench scale to a self-supporting technology with significant potential for growth. Radio-frequency heating was any un-explored option for laminating glass prior to this program. With significant commercial success through time and energy savings in the wood, paper, and plastics industries, RF heating was found to have significant promise for the energy intensive glass lamination industry. A major technical goal of the program was to demonstrate RF lamination across a wide range of laminate sizes and materials. This was successfully accomplished, dispelling many skeptics' concerns about the abilities of the technology. Ceralink laminated panels up to 2 ft x 3 ft, with four sets processed simultaneously, in a 3 minute cycle. All major categories of interlayer materials were found to work with RF lamination. In addition to laminating glass, other materials including photovoltaic silicon solar cells, light emitting diodes, metallized glass, plastics (acrylic and polycarbonate), and ceramics (alumina) were found compatible with the RF process. This opens up a wide range of commercial opportunities beyond the initially targeted automotive industry. The dramatic energy savings reported for RF lamination at the bench scale were found to be maintained through the scale up of the process. Even at 2 ft x 3 ft panel sizes, energy savings are estimated to be at least 90% compared to autoclaving or vacuum lamination. With targeted promotion through conference presentations, press releases and internet presence, RF lamination has gained significant attention, drawing large audiences at American Ceramic Society meetings. The commercialization success of the project includes the establishment of a revenue-generating business model for providing process development and demonstrations for potential RF lamination users. A path to industrial energy benefits and revenue through industrial equipment sales was established in a partnership with Thermex Thermatron, a manufacturer of RF equipment.

  4. A Germanium Isotope Record From Diatom Opal

    NASA Astrophysics Data System (ADS)

    Mantoura, S.; Galy, A.; de La Rocha, C. L.; Elderfield, H.; Shemesh, A.

    2005-12-01

    Here we present the first known record of the germanium isotopic composition of sedimentary diatom opal and the results of diatom culturing experiments. Analyses were performed using a hydride generation system coupled to a MC-ICP-MS and variations in the 74Ge/70Ge ratio are reported as ?74Ge. Diatom cultures grown in the laboratory showed no notable fractionation; For all experiments, the ?74Ge of the cultured opal fell within analytical error of the culture media. This lack of fractionation suggests that the ?74Ge of opal may be used as a paleorecorder of seawater ?74Ge. We tested procedures for the cleaning and dissolution of sedimentary samples and the purification of Ge. Comparison of the ?74Ge and trace metal content of the opal and fine fractions of sediments from 9 locations in the Southern Ocean indicate that the < 0.2 ?m fraction has a lighter isotopic composition than pure opal and that care must be taken to prevent this ultra fine fraction interfering with opal based measurements. Fe, Al, and Ti levels in measured samples may be used to indicate contamination. There is an insignificant difference between the average glacial and average interglacial ?74Ge of opal from a down core record spanning the penultimate deglaciation (MIS 6-5e) in the Southern Ocean. However, there appears to be a small (0.6) but notable perturbation at the glacial termination. The average ?74Ge of sedimentary opal indicates a seawater ?74Ge of +4.0 0.4 . This value is almost 3 heavier than a bulk silicate earth average of +1.1 0.3 [1], requiring the existence of a further sink for isotopically light Ge. The lack of variation in ?74Ge opal in this record stands in contrast to the systematic changes in Ge/Si opal. A one box model can be used to compare competing explanations for changes in Ge/Si opal by simulating their effect on ?74Ge, although this work is limited by the large uncertainties which exist in the the Ge isotope budget. [1] Rouxel,O. Galy,A. and Elderfield,H. Ge/Si and Ge isotope systematic in marine sediments, GCA 68, S1, A365.

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

    NASA Astrophysics Data System (ADS)

    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 ?13C indicating that MPB is their major carbon source. ?15N, 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.

  6. Spatial paradigms of lotic diatom distribution: A landscape ecology perspective

    USGS Publications Warehouse

    Passy, S.I.

    2001-01-01

    Spatial distributional patterns of benthic diatoms and their relation to current velocity were investigated in an unshaded cobble-bottom reach of White Creek (Washington County, NY). On 27 August 1999, diatoms were sampled and current velocity and depth were measured on a regular square sampling grid with a grain size of 0.01 m2, interval of 0.5 m, and extent of 16 m2. The relative abundance of the 18 common diatom species enumerated in the 81 samples was subjected to detrended correspondence analysis (DCA). The first axis (DCA1) explained 51% of the variance in diatom data and separated the samples according to current regimes. The spatial autocorrelation of DCA1 sample scores in deposition and erosion regions of White Creek was determined by Moran's I statistic to indicate patch size. In White Creek the patch length of all diatom communities was more than 3.1 m, whereas the patch width was 1 m in the deposition region and 0.5 m in the erosion region. There were 5 dominant diatom taxa, Achnanthes minutissima Ku??tz. et vars, Fragilaria capucina Dezmazie??res et vars, F. crotonensis Kitt., Diatoma vulgaris Bory, and Synedra ulna (Nitz.) Ehr. et vars. The patch length of the dominant species varied from 1 to more than 4.1 m, whereas the patch width, if defined, was 0.5 m. Achnanthes minutissima and F. capucina, the two diatom species with the highest relative abundance, displayed spatially structured patches of low abundance and comparatively random patches of high abundance, suggesting broad scale abiotic control of species performance in low abundance regions and finer scale biotic control of high abundance areas. Another objective of this study was to test the hypothesis that higher current velocities, which generally impede immigration, would increase randomness and complexity (i.e. homogeneity of diatom distributional patterns). The spatial complexity in low versus high velocity transects was determined by calculating the respective fractal dimension (D) of DCA1 scores. D of DCA1 was higher in the higher current velocity transects, suggesting that spatial complexity and homogeneity of diatom communities increased in faster currents. Partial canonical correspondence analysis was conducted on diatom, environmental, and spatial data to assess how much of the variance in species distribution could be attributed to environmental (current velocity and depth) versus spatial factors. The variance of species data, explained by the environment (exclusively current velocity), was 38%; whereas space alone contributed only 10%, indicating that 1) current velocity was the major factor that controlled diatom distribution in streams and 2) there were other spatially dependent variables, most likely biotic, but their role in shaping diatom communities was minor.

  7. Diatoms on earth, comets, Europa and in interstellar space

    NASA Technical Reports Server (NTRS)

    Hoover, R. B.; Hoover, M. J.; Hoyle, F.; Wickramasinghe, N. C.; Al-Mufti, S.

    1986-01-01

    There exists a close correspondence between the measured infrared properties of diatoms and the infrared spectrum of interstellar dust as observed in the Trapezium nebula and toward the galactic center source GC-IRS 7. Diatoms and bacteria also exhibit an absorbance peak near 2200 A, which is found to agree with the observed ultraviolet absorbance properties of interstellar grains. The observational data are reviewed, and the known properties of diatoms and bacteria are considered. It is suggested that these characteristics are consistent with the concept of a cosmic microbiological system in which these or similar microorganisms might exist on comets, Europa and in interstellar space.

  8. An aqueous route to organically functionalized silica diatom skeletons

    NASA Astrophysics Data System (ADS)

    Fowler, Christabel E.; Buchber, Catherine; Lebeau, Bndicte; Patarin, Jol; Delacte, Cyril; Walcarius, Alain

    2007-04-01

    Diatomaceous earth was functionalized by grafting organotrialkoxysilane precursors onto the surface of the porous silica cell walls of this biomineral. Vinyl- and mercapto-containing structures were prepared in aqueous media without disruption of the diatomic architecture. Successful grafting of the organic moieties was confirmed using solid state 29Si MAS NMR spectroscopy, and the presence of the intact diatom framework by scanning electron microscopy. The sorption properties of mercaptopropyl-functionalized diatoms towards heavy metals was studied by measuring the accessibility and diffusion rates of mercury(II) species to the binding sites (-SH) by the means of electrochemical methods.

  9. Energy Saving Glass Lamination via Selective Radio Frequency Heating

    SciTech Connect

    Allan, Shawn M.

    2012-02-27

    This project focused on advancing radio-frequency (RF) lamination technology closer to commercial implementation, in order to reduce the energy intensity of glass lamination by up to 90%. Lamination comprises a wide range of products including autoglass, architectural safety and innovative design glass, transparent armor (e.g. bullet proof glass), smart glass, mirrors, and encapsulation of photovoltaics. Lamination is also the fastest growing segment of glass manufacturing, with photovoltaics, architectural needs, and an anticipated transition to laminated side windows in vehicles. The state-of-the-art for glass lamination is to use autoclaves, which apply heat and uniform gas pressure to bond the laminates over the course of 1 to 18 hours. Laminates consist of layers of glass or other materials bonded with vinyl or urethane interlayers. In autoclaving, significant heat energy is lost heating the chamber, pressurized air, glass racks, and the glass. In RF lamination, the heat is generated directly in the vinyl interlayer, causing it to heat and melt quickly, in just 1 to 10 minutes, without significantly heating the glass or the equipment. The main purpose of this project was to provide evidence that low energy, rapid RF lamination quality met the same standards as conventionally autoclaved windows. The development of concepts for laminating curved glass with RF lamination was a major goal. Other primary goals included developing a stronger understanding of the lamination product markets described above, and to refine the potential benefits of commercial implementation. The scope of the project was to complete implementation concept studies in preparation for continuation into advanced development, pilot studies, and commercial implementation. The project consisted of 6 main tasks. The first dealt with lamination with poly-vinyl butyral (PVB) interlayers, which prior work had shown difficulties in achieving good quality laminates, working with Pilkington North America. The second task dealt with a study of current lamination processes in the various laminate industries, and development of concepts for integrating RF lamination into new or existing processes. The third task explored the use of a non-destructive technique for analyzing laminate adhesion with the University of Illinois at Urbana-Champaign. The fourth task focused on developing concepts for curved glass lamination using RF lamination. The fifth and sixth tasks together comprised an analysis of laminate product markets, ranking for applicability and commercialization potential, and the development of commercialization strategies for those products. In addition, throughout the project as new experimental data and conventional process data were obtained, the benefits analysis of RF lamination was refined. The goals of the project described above were achieved, positioning RF lamination for the next stage growth envisioned in the original Industrial Grand Challenge proposal. Working with Pilkington North America, lamination of flat autoglass with PVB was achieved, meeting all 16 stringent industry tests. In particular, PVB laminates made with RF lamination passed environmental tests including the high temperature, 120 C bake test, without significant formation of bubbles (defects). The adhesion of PVB to glass was measured using the pummel method. Adhesion values ranging from 1 to 7 out of 10 were obtained. The significant process parameters affecting the environmental and adhesion performance were identified through a designed experiment. Pre-lamination process variables including PVB storage humidity and the de-airing process (vacuum or nip rolling) were significant, as well as the level of pressure applied to the laminate during the RF process. Analysis of manufacturing with RF lamination equipment, based on the processes developed indicated that 3 RF presses could replace a typical auto-industry autoclave to achieve equal or greater throughput with possibly less capital cost and smaller footprint. Concepts for curved lamination identifying castable molds for prototyping were developed, which allowed Ceralink to obtain commitment to begin curved tooling development. The project significantly helped to advance RF lamination past the feasibility and novelty stage and into the realm of commercial acceptance as a viable alternative to autoclaves. The demonstration of autoclave-quality autoglass produced in just 1 minute with RF lamination, with validation by Pilkington, has fueled industry motivation to seriously consider RF lamination. The industry and other contacts and outreach made in the study of laminate markets (including 3 technical publications and 5 conference presentations), has resulted in a recent surge in RF lamination activity.

  10. Energy Saving Glass Lamination via Selective Radio Frequency Heating

    SciTech Connect

    Allan, Shawn M.; Baranova, Inessa; Poley, Joseph; Reis, Henrique

    2012-02-27

    This project focused on advancing radio-frequency (RF) lamination technology closer to commercial implementation, in order to reduce the energy intensity of glass lamination by up to 90%. Lamination comprises a wide range of products including autoglass, architectural safety and innovative design glass, transparent armor (e.g. bullet proof glass), smart glass, mirrors, and encapsulation of photovoltaics. Lamination is also the fastest growing segment of glass manufacturing, with photovoltaics, architectural needs, and an anticipated transition to laminated side windows in vehicles. The state-of-the-art for glass lamination is to use autoclaves, which apply heat and uniform gas pressure to bond the laminates over the course of 1 to 18 hours. Laminates consist of layers of glass or other materials bonded with vinyl or urethane interlayers. In autoclaving, significant heat energy is lost heating the chamber, pressurized air, glass racks, and the glass. In RF lamination, the heat is generated directly in the vinyl interlayer, causing it to heat and melt quickly, in just 1 to 10 minutes, without significantly heating the glass or the equipment. The main purpose of this project was to provide evidence that low energy, rapid RF lamination quality met the same standards as conventionally autoclaved windows. The development of concepts for laminating curved glass with RF lamination was a major goal. Other primary goals included developing a stronger understanding of the lamination product markets described above, and to refine the potential benefits of commercial implementation. The scope of the project was to complete implementation concept studies in preparation for continuation into advanced development, pilot studies, and commercial implementation. The project consisted of 6 main tasks. The first dealt with lamination with poly-vinyl butyral (PVB) interlayers, which prior work had shown difficulties in achieving good quality laminates, working with Pilkington North America. The second task dealt with a study of current lamination processes in the various laminate industries, and development of concepts for integrating RF lamination into new or existing processes. The third task explored the use of a non-destructive technique for analyzing laminate adhesion with the University of Illinois at Urbana-Champaign. The fourth task focused on developing concepts for curved glass lamination using RF lamination. The fifth and sixth tasks together comprised an analysis of laminate product markets, ranking for applicability and commercialization potential, and the development of commercialization strategies for those products. In addition, throughout the project as new experimental data and conventional process data were obtained, the benefits analysis of RF lamination was refined. The goals of the project described above were achieved, positioning RF lamination for the next stage growth envisioned in the original Industrial Grand Challenge proposal. Working with Pilkington North America, lamination of flat autoglass with PVB was achieved, meeting all 16 stringent industry tests. In particular, PVB laminates made with RF lamination passed environmental tests including the high temperature, 120 °C bake test, without significant formation of bubbles (defects). The adhesion of PVB to glass was measured using the pummel method. Adhesion values ranging from 1 to 7 out of 10 were obtained. The significant process parameters affecting the environmental and adhesion performance were identified through a designed experiment. Pre-lamination process variables including PVB storage humidity and the de-airing process (vacuum or nip rolling) were significant, as well as the level of pressure applied to the laminate during the RF process. Analysis of manufacturing with RF lamination equipment, based on the processes developed indicated that 3 RF presses could replace a typical auto-industry autoclave to achieve equal or greater throughput with possibly less capital cost and smaller footprint. Concepts for curved lamination identifying castable molds for prototyping were developed, which allowed Ceralink to obtain commitment to begin curved tooling development. The project significantly helped to advance RF lamination past the feasibility and novelty stage and into the realm of commercial acceptance as a viable alternative to autoclaves. The demonstration of autoclave-quality autoglass produced in just 1 minute with RF lamination, with validation by Pilkington, has fueled industry motivation to seriously consider RF lamination. The industry and other contacts and outreach made in the study of laminate markets (including 3 technical publications and 5 conference presentations), has resulted in a recent surge in RF lamination activity.

  11. Analytical solution to bending of stiffened and continuous antisymmetric laminates

    NASA Astrophysics Data System (ADS)

    Sun, Liecheng; Harik, Issam E.

    2015-01-01

    Analytical Strip Method is presented for the analysis of the bending-extension coupling problem of stiffened and continuous antisymmetric thin laminates. A system of three equations of equilibrium, governing the general response of antisymmetric laminates, is reduced to a single eighth-order partial differential equation (PDE) in terms of a displacement function. The PDE is then solved in a single series form to determine the displacement response of antisymmetric cross-ply and angle-ply laminates. The solution is applicable to rectangular laminates with two opposite edges simply supported and the other edges being free, clamped, simply supported, isotropic beam supports, or point supports.

  12. An Elastic Model of Blebbing in Nuclear Lamin Meshworks

    NASA Astrophysics Data System (ADS)

    Funkhouser, Chloe; Sknepnek, Rastko; Shimi, Takeshi; Goldman, Anne; Goldman, Robert; Olvera de La Cruz, Monica

    2013-03-01

    A two-component continuum elastic model is introduced to analyze a nuclear lamin meshwork, a structural element of the lamina of the nuclear envelope. The main component of the lamina is a meshwork of lamin protein filaments providing mechanical support to the nucleus and also playing a role in gene expression. Abnormalities in nuclear shape are associated with a variety of pathologies, including some forms of cancer and Hutchinson-Gilford progeria syndrome, and are often characterized by protruding structures termed nuclear blebs. Nuclear blebs are rich in A-type lamins and may be related to pathological gene expression. We apply the two-dimensional elastic shell model to determine which characteristics of the meshwork could be responsible for blebbing, including heterogeneities in the meshwork thickness and mesh size. We find that if one component of the lamin meshwork, rich in A-type lamins, has a tendency to form a larger mesh size than that rich in B-type lamins, this is sufficient to cause segregation of the lamin components and also to form blebs rich in A-type lamins. The model produces structures with comparable morphologies and mesh size distributions as the lamin meshworks of real, pathological nuclei. Funded by US DoE Award DEFG02-08ER46539 and by the DDR&E and AFOSR under Award FA9550-10-1-0167; simulations performed on NU Quest cluster

  13. Mechanical model of blebbing in nuclear lamin meshworks

    PubMed Central

    Funkhouser, Chloe M.; Sknepnek, Rastko; Shimi, Takeshi; Goldman, Anne E.; Goldman, Robert D.; Olvera de la Cruz, Monica

    2013-01-01

    Much of the structural stability of the nucleus comes from meshworks of intermediate filament proteins known as lamins forming the inner layer of the nuclear envelope called the nuclear lamina. These lamin meshworks additionally play a role in gene expression. Abnormalities in nuclear shape are associated with a variety of pathologies, including some forms of cancer and HutchinsonGilford Progeria Syndrome, and often include protruding structures termed nuclear blebs. These nuclear blebs are thought to be related to pathological gene expression; however, little is known about how and why blebs form. We have developed a minimal continuum elastic model of a lamin meshwork that we use to investigate which aspects of the meshwork could be responsible for bleb formation. Mammalian lamin meshworks consist of two types of lamin proteins, A type and B type, and it has been reported that nuclear blebs are enriched in A-type lamins. Our model treats each lamin type separately and thus, can assign them different properties. Nuclear blebs have been reported to be located in regions where the fibers in the lamin meshwork have a greater separation, and we find that this greater separation of fibers is an essential characteristic for generating nuclear blebs. The model produces structures with comparable morphologies and distributions of lamin types as real pathological nuclei. Thus, preventing this opening of the meshwork could be a route to prevent bleb formation, which could be used as a potential therapy for the pathologies associated with nuclear blebs. PMID:23401537

  14. Residual stress and crack propagation in laminated composites

    SciTech Connect

    Yttergren, R.M.F.; Zeng, K.; Rowcliffe, D.J.

    1994-12-31

    Residual stress distributions in several laminated ceramic composites were measured by an indentation technique. The material included alumina-zirconia laminated composites, containing strong interfaces, and alumina-porcelain laminated composites with both weak and strong interfaces. The residual stress in these material originates from the mismatch of the thermal properties, differences in elastic properties, and different shrinkage of the laminates during sintering. An experimental technique is presented which gives a direct view of the residual stress state in the materials. Values of residual tensile stress are presented as a function of position relative to the interface in each material.

  15. Extrinsic fracture mechanisms in two laminated metal composites

    SciTech Connect

    Lesuer, D.; Syn, C.; Riddle, R.; Sherby, O.

    1994-11-29

    The crack growth behavior and fracture toughness of two laminated metal composites (6090/SiC/25p laminated with 5182 and ultrahigh-carbon steel laminated with brass) have been studied in both ``crack arrester`` and ``crack divider`` orientations. The mechanisms of crack growth were analyzed and extrinsic toughening mechanisms were found to contribute significantly to the toughness. The influence of laminate architecture (layer thickness and component volume function), component material properties and residual stress on these mechanisms and the resulting crack growth resistance are discussed.

  16. Lamins position the nuclear pores and centrosomes by modulating dynein

    PubMed Central

    Guo, Yuxuan; Zheng, Yixian

    2015-01-01

    Lamins, the type V nuclear intermediate filament proteins, are reported to function in both interphase and mitosis. For example, lamin deletion in various cell types can lead to an uneven distribution of the nuclear pore complexes (NPCs) in the interphase nuclear envelope, whereas deletion of B-type lamins results in spindle orientation defects in mitotic neural progenitor cells. How lamins regulate these functions is unknown. Using mouse cells deleted of different combinations or all lamins, we show that lamins are required to prevent the aggregation of NPCs in the nuclear envelope near centrosomes in late G2 and prophase. This asymmetric NPC distribution in the absence of lamins is caused by dynein forces acting on NPCs via the dynein adaptor BICD2. We further show that asymmetric NPC distribution upon lamin depletion disrupts the distribution of BICD2 and p150 dynactin on the nuclear envelope at prophase, which results in inefficient dynein-driven centrosome separation during prophase. Therefore lamins regulate microtubule-based motor forces in vivo to ensure proper NPC distribution in interphase and centrosome separation in the mitotic prophase. PMID:26246603

  17. Nitrate Utilization by the Diatom Skeletonema costatum

    PubMed Central

    Serra, Juan L.; Llama, Maria J.; Cadenas, Eduardo

    1978-01-01

    Nitrate uptake has been studied in nitrogen-deficient cells of the marine diatom Skeletonema costatum. When these cells are incubated in the presence of nitrate, this ion is quickly taken up from the medium, and nitrite is excreted by the cells. Nitrite is excreted following classical saturation kinetics, its rate being independent of nitrate concentration in the incubation medium for nitrate concentration values higher than 3 micromolar. Nitrate uptake shows mixed-transfer kinetics, which can be attributed to the simultaneous contributions of mediated and diffusion transfer. Cycloheximide and p-hydroxymercuribenzoate inhibit the carrier-mediated contribution to nitrate uptake, without affecting the diffusion component. When cells are preincubated with nitrate, the net nitrogen uptake is increased. PMID:16660652

  18. Relationships between dipole moments of diatomic molecules.

    PubMed

    Hou, Shilin; Bernath, Peter F

    2015-02-14

    The dipole moment is one of the most important physical properties of a molecule. We present a combination rule for the dipole moments of related diatomic molecules. For molecules AB, AX, BY, and XY from two different element groups in the periodic table, if their elements make a small parallelogram, reliable predictions can be obtained. Our approach is particularly useful for systems with heavy atoms. For a large set of molecules tested, the average difference of the prediction from experimental data is less than 0.2 debye (D). The dipole moments for heavy molecules such as GaCl, InBr, SrCl, and SrS, for which no experimental data are available at present, are predicted to be 3.17, 3.76, 3.85 and 11.54 D, respectively. PMID:25588998

  19. Star Trek replicators and diatom nanotechnology.

    PubMed

    Drum, Ryan W; Gordon, Richard

    2003-08-01

    Diatoms are single celled algae, the 10(5)-10(6) species of which create a wide variety of three-dimensional amorphous silica shells. If we could get them to produce useful structures, perhaps by compustat selection experiments (i.e. forced evolution of development or evodevo), their exponential growth in suspension cultures could compete with the lithography techniques of present day nanotechnology, which have limited 3D capabilities. Alternatively, their fine detail could be used for templates for MEMS (micro electro mechanical systems), or their silica deposition systems isolated for guiding silica deposition. A recent paper has demonstrated that silica can be replaced atom for atom without change of shape--a step towards the Star Trek replicator. PMID:12902165

  20. The dilemma of disappearing diatoms: Incorporating diatom dissolution data into palaeoenvironmental modelling and reconstruction

    NASA Astrophysics Data System (ADS)

    Ryves, David B.; Battarbee, Richard W.; Fritz, Sherilyn C.

    2009-01-01

    Taphonomic issues pose fundamental challenges for Quaternary scientists to recover environmental signals from biological proxies and make accurate inferences of past environments. The problem of microfossil preservation, specifically diatom dissolution, remains an important, but often overlooked, source of error in both qualitative and quantitative reconstructions of key variables from fossil samples, especially those using relative abundance data. A first step to tackling this complex issue is establishing an objective method of assessing preservation (here, diatom dissolution) that can be applied by different analysts and incorporated into routine counting strategies. Here, we establish a methodology for assessment of diatom dissolution under standard light microscopy (LM) illustrated with morphological criteria for a range of major diatom valve shapes. Dissolution data can be applied to numerical models (transfer functions) from contemporary samples, and to fossil material to aid interpretation of stratigraphic profiles and taphonomic pathways of individual taxa. Using a surface sediment diatom-salinity training set from the Northern Great Plains (NGP) as an example, we explore a variety of approaches to include dissolution data in salinity inference models indirectly and directly. Results show that dissolution data can improve models, with apparent dissolution-adjusted error (RMSE) up to 15% lower than their unadjusted counterparts. Internal validation suggests improvements are more modest, with bootstrapped prediction errors (RMSEP) up to 10% lower. When tested on a short core from Devils Lake, North Dakota, which has a historical record of salinity, dissolution-adjusted models infer higher values compared to unadjusted models during peak salinity of the 1930s-1940s Dust Bowl but nonetheless significantly underestimate peak values. Site-specific factors at Devils Lake associated with effects of lake level change on taphonomy (preservation and re-working, implied by dissolution data) may override model improvements incorporating dissolution. Dissolution-adjusted salinity models are also applied to a 150-year sediment record from Spiritwood Lake, North Dakota, which suggests that this lake has a damped and lagged response to major regional climate forcing of salinity during the Dust Bowl. At this site, dissolution data also suggest different taphonomic behaviour of taxa related to their seasonal patterns of growth and sedimentation. Thus, dissolution data can improve models, and aid interpretation of sedimentary profiles as records of limnological, ecological and environmental change, filtered by taphonomy.

  1. 78 FR 48903 - Certain Products Having Laminated Packaging, Laminated Packaging, and Components Thereof...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-12

    ... infringement of certain claims of nine patents. 78 FR 19,007. The subject products are certain laminated... industry requirement.'' 78 FR 19,008. The ALJ conducted a hearing on the domestic-industry issue on May 16... the complainant did not satisfy the economic prong of the domestic industry requirement. On...

  2. A Simplified Quantum Mechanical Model of Diatomic Molecules

    ERIC Educational Resources Information Center

    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)

  3. Modified Ribose Receptor Response in Isolated Diatom Frustules

    SciTech Connect

    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.

  4. Adhesive characterization in prestressed piezoelectric laminates

    NASA Astrophysics Data System (ADS)

    Hodges, Charles A.; Mossi, Karla M.; Scott, Lisa A.

    2003-08-01

    Pre-stressed piezoelectric laminates, consisting of one or more metal layers and a piezoelectric material bonded together with an adhesive, have been widely studied over the past few years, both numerically and experimentally. Most of the current research has concentrated on the effect of the metal layers, types and geometry, along with variations in the active layer of the laminate. Historically, the adhesive layer has been neglected as a contributing factor in the overall performance of the final device. This paper attempts to address the effect of the adhesive line thickness and its influence on the performance of pre-stressed piezoelectric laminates under specific boundary conditions. All laminates tested were constructed with the following lay-up: 0.354 mm thick stainless steel, adhesive, 0.381 mm PZT ceramic, adhesive, and a 0.0254 mm aluminum layer. The devices having an adhesive line thickness of 0.169 mm were classified as group A, and group B were the devices with an adhesive line thickness of 0.036 mm. The adhesive line thickness for group A was approximately 21% more than the line thickness of group B. The devices were tested in a simply supported, free-free condition under a series of loads at a constant frequency of 5 Hz over a voltage range from 400 to 800 Volts peak-to-peak. Displacement was measured using loads of 25, 50, 75, 100, and 200 grams for each actuator. The data from each group was averaged and compared. The results showed group B generated more displacement at the same "arm weight" applied as compared to group A. However, only three samples for group B were measured since the rest of the samples failed during testing. Failure of the devices of group B may be due to the ultimate stress of the devices and their ability to lift a load under those conditions. The study demonstrated that adhesive layer thickness, along with the manufacturing process, has to be taken into account when developing an application that requires load-bearing capabilities. Even though no direct mechanical property measurements were taken to verify this theory, the results demonstrated that the adhesive does play a critical role in the performance of the device as an actuator and should be factored into both experimental and numerical studies to obtain more accurate predictions of the ultimate behavior of these devices.

  5. Tailoring Laminates For Protection Against Projectiles

    NASA Technical Reports Server (NTRS)

    Gassner, John J.; Boyce, Joseph S.; Smirlock, Martin E.; Evans, David A.

    1992-01-01

    Fiber/matrix composite laminates developed to protect military land vehicles against projectiles and spacecraft against impacts by micrometeroids. Although types, sizes, and velocities of expected incident objects differ between terrestrial and outer-space cases, general protection problems and solutions exhibit some common features. Configurations of fibers and matrices optimized with respect to protection, bulk, and weight, to obtain shield that breaks rapidly moving incident object into harmless smaller, more-slowly-moving pieces, containing debris, vaporizes debris, and/or otherwise absorbs kinetic energy of object to prevent harm to vehicle and occupants.

  6. Fracture modes in notched angleplied composite laminates

    NASA Technical Reports Server (NTRS)

    Irvine, T. B.; Ginty, C. A.

    1984-01-01

    The Composite Durability Structural Analysis (CODSTRAN) computer code is used to determine composite fracture. Fracture modes in solid and notched, unidirectional and angleplied graphite/epoxy composites were determined by using CODSTRAN. Experimental verification included both nondestructive (ultrasonic C-Scanning) and destructive (scanning electron microscopy) techniques. The fracture modes were found to be a function of ply orientations and whether the composite is notched or unnotched. Delaminations caused by stress concentrations around notch tips were also determined. Results indicate that the composite mechanics, structural analysis, laminate analysis, and fracture criteria modules embedded in CODSTRAN are valid for determining composite fracture modes.

  7. Micromechanics of composite laminate compression failures

    NASA Technical Reports Server (NTRS)

    Guynn, E. Gail; Bradley, Walter L.

    1988-01-01

    The purpose of this annual progress report is to summarize the work effort and results accomplished from July 1987 through July 1988 on NASA Research Grant NAG1-659 entitled Micromechanics of Composite Laminate Compressive Failure. The report contains: (1) the objective of the proposed research, (2) the summary of accomplishments, (3) a more extensive review of compression literature, (4) the planned material (and corresponding properties) received to date, (5) the results for three possible specimen geometries, experimental procedures planned, and current status of the experiments, and (6) the work planned for the next contract year.

  8. Laminated anisotropic reinforced plastic plates and shells

    NASA Technical Reports Server (NTRS)

    Korolev, V. I.

    1981-01-01

    Basic technical theories and engineering calculation equations for anisotropic plates and shells made of rigid reinforced plastics, mainly laminated fiberglass, are presented and discussed. Solutions are given for many problems of design of structural plates and shells, including curved sections and tanks, as well as two chapters on selection of the optimum materials, are given. Accounting for interlayer shearing and transverse separation, which are new engineering properties, are discussed. Application of the results obtained to thin three ply plates and shells wth a light elastic filler is presented and discussed.

  9. Opening the gateways for diatoms primes Earth for Antarctic glaciation

    NASA Astrophysics Data System (ADS)

    Egan, Katherine E.; Rickaby, Rosalind E. M.; Hendry, Katharine R.; Halliday, Alex N.

    2013-08-01

    The abrupt onset of Antarctic glaciation during the Eocene-Oligocene Transition (∼33.7 Ma, Oi1) is linked to declining atmospheric pCO2 levels, yet the mechanisms that forced pCO2 decline remain elusive. Biogenic silicon cycling is inextricably linked to both long and short term carbon cycling through the diatoms, siliceous walled autotrophs which today account for up to 40% of primary production. It is hypothesised that during the Late Eocene a sharp rise in diatom abundance could have contributed to pCO2 drawdown and global cooling by increasing the proportion of organic carbon buried in marine sediment. Diatom and sponge silicon isotope ratios (δ30Si) are here combined for the first time to reconstruct the late Eocene-early Oligocene ocean silicon cycle and provide new insight into the role of diatom productivity in Antarctic glaciation. At ODP site 1090 in the Southern Ocean, a 0.6‰ rise in diatom δ30Si through the late Eocene documents increasing diatom silicic acid utilisation with high, near modern values attained by the earliest Oligocene. A concomitant 1.5‰ decline in sponge δ30Si at ODP site 689 on the Maud Rise tracks an approximate doubling of intermediate depth silicic acid concentration in the high southern latitudes. Intermediate depth silicic acid concentration peaked at ∼31.5 Ma, coincident with the final establishment of a deepwater pathway through the Tasman Gateway and Drake Passage. These results suggest that upwelling intensification related to the spin-up of a circum-Antarctic current may have driven late Eocene diatom proliferation. Organic carbon burial associated with higher diatom abundance and export provides a mechanism that can account for pCO2 drawdown not only at, but also prior to, Antarctic glaciation as required by a pCO2 'threshold' mechanism for ice sheet growth.

  10. Diversity and Evolutionary History of Iron Metabolism Genes in Diatoms.

    PubMed

    Groussman, Ryan D; Parker, Micaela S; Armbrust, E Virginia

    2015-01-01

    Ferroproteins arose early in Earth's history, prior to the emergence of oxygenic photosynthesis and the subsequent reduction of bioavailable iron. Today, iron availability limits primary productivity in about 30% of the world's oceans. Diatoms, responsible for nearly half of oceanic primary production, have evolved molecular strategies for coping with variable iron concentrations. Our understanding of the evolutionary breadth of these strategies has been restricted by the limited number of species for which molecular sequence data is available. To uncover the diversity of strategies marine diatoms employ to meet cellular iron demands, we analyzed 367 newly released marine microbial eukaryotic transcriptomes, which include 47 diatom species. We focused on genes encoding proteins previously identified as having a role in iron management: iron uptake (high-affinity ferric reductase, multi-copper oxidase, and Fe(III) permease); iron storage (ferritin); iron-induced protein substitutions (flavodoxin/ferredoxin, and plastocyanin/cytochrome c6) and defense against reactive oxygen species (superoxide dismutases). Homologs encoding the high-affinity iron uptake system components were detected across the four diatom Classes suggesting an ancient origin for this pathway. Ferritin transcripts were also detected in all Classes, revealing a more widespread utilization of ferritin throughout diatoms than previously recognized. Flavodoxin and plastocyanin transcripts indicate possible alternative redox metal strategies. Predicted localization signals for ferredoxin identify multiple examples of gene transfer from the plastid to the nuclear genome. Transcripts encoding four superoxide dismutase metalloforms were detected, including a putative nickel-coordinating isozyme. Taken together, our results suggest that the majority of iron metabolism genes in diatoms appear to be vertically inherited with functional diversity achieved via possible neofunctionalization of paralogs. This refined view of iron use strategies in diatoms elucidates the history of these adaptations, and provides potential molecular markers for determining the iron nutritional status of different diatom species in environmental samples. PMID:26052941

  11. Differential response of marine diatoms to trace metals

    SciTech Connect

    Tadros, M.G.; Mbuthia, P.; Smith, W. )

    1990-06-01

    Phytoplankton constitutes the base of aquatic food chains and is thus important to aquatic communities. Trace metal micro-nutrients play a significant role in the ecology of phytoplankton. Phytoplankton species vary in their tolerance to trace metals. Diatoms in particular are able to detoxify trace metals by the excretion of organic compounds. The authors examined the effect of copper, nickel and zinc on ten marine diatoms to determine whether they differed in their responses to these metals.

  12. Computer checking of rotational line intensity factors for diatomic transitions.

    NASA Technical Reports Server (NTRS)

    Whiting, E. E.; Paterson, J. A.; Kovacs, I.; Nicholls, R. W.

    1973-01-01

    Previously published analytical formulae for the rotational line intensity factors of diatomic molecules have been compared with results from a comprehensive computer program, which determines numerical intensity factors for both spin-allowed and spin-forbidden electric and magnetic dipole transitions in diatomic molecules. The comparison uncovered several typographical errors and a few algebraic errors in the published formulae. The changes required in the formulae to give agreement with the results from the computer program are tabulated.

  13. Diversity and Evolutionary History of Iron Metabolism Genes in Diatoms

    PubMed Central

    Groussman, Ryan D.; Parker, Micaela S.; Armbrust, E. Virginia

    2015-01-01

    Ferroproteins arose early in Earth’s history, prior to the emergence of oxygenic photosynthesis and the subsequent reduction of bioavailable iron. Today, iron availability limits primary productivity in about 30% of the world’s oceans. Diatoms, responsible for nearly half of oceanic primary production, have evolved molecular strategies for coping with variable iron concentrations. Our understanding of the evolutionary breadth of these strategies has been restricted by the limited number of species for which molecular sequence data is available. To uncover the diversity of strategies marine diatoms employ to meet cellular iron demands, we analyzed 367 newly released marine microbial eukaryotic transcriptomes, which include 47 diatom species. We focused on genes encoding proteins previously identified as having a role in iron management: iron uptake (high-affinity ferric reductase, multi-copper oxidase, and Fe(III) permease); iron storage (ferritin); iron-induced protein substitutions (flavodoxin/ferredoxin, and plastocyanin/cytochrome c6) and defense against reactive oxygen species (superoxide dismutases). Homologs encoding the high-affinity iron uptake system components were detected across the four diatom Classes suggesting an ancient origin for this pathway. Ferritin transcripts were also detected in all Classes, revealing a more widespread utilization of ferritin throughout diatoms than previously recognized. Flavodoxin and plastocyanin transcripts indicate possible alternative redox metal strategies. Predicted localization signals for ferredoxin identify multiple examples of gene transfer from the plastid to the nuclear genome. Transcripts encoding four superoxide dismutase metalloforms were detected, including a putative nickel-coordinating isozyme. Taken together, our results suggest that the majority of iron metabolism genes in diatoms appear to be vertically inherited with functional diversity achieved via possible neofunctionalization of paralogs. This refined view of iron use strategies in diatoms elucidates the history of these adaptations, and provides potential molecular markers for determining the iron nutritional status of different diatom species in environmental samples. PMID:26052941

  14. Resonant inelastic collisions of electrons with diatomic molecules

    NASA Astrophysics Data System (ADS)

    Houfek, Karel

    2012-05-01

    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.

  15. Growth form defines physiological photoprotective capacity in intertidal benthic diatoms

    PubMed Central

    Barnett, Alexandre; Méléder, Vona; Blommaert, Lander; Lepetit, Bernard; Gaudin, Pierre; Vyverman, Wim; Sabbe, Koen; Dupuy, Christine; Lavaud, Johann

    2015-01-01

    In intertidal marine sediments, characterized by rapidly fluctuating and often extreme light conditions, primary production is frequently dominated by diatoms. We performed a comparative analysis of photophysiological traits in 15 marine benthic diatom species belonging to the four major morphological growth forms (epipelon (EPL), motile epipsammon (EPM-M) and non-motile epipsammon (EPM-NM) and tychoplankton (TYCHO)) found in these sediments. Our analyses revealed a clear relationship between growth form and photoprotective capacity, and identified fast regulatory physiological photoprotective traits (that is, non-photochemical quenching (NPQ) and the xanthophyll cycle (XC)) as key traits defining the functional light response of these diatoms. EPM-NM and motile EPL showed the highest and lowest NPQ, respectively, with EPM-M showing intermediate values. Like EPL, TYCHO had low NPQ, irrespective of whether they were grown in benthic or planktonic conditions, reflecting an adaptation to a low light environment. Our results thus provide the first experimental evidence for the existence of a trade-off between behavioural (motility) and physiological photoprotective mechanisms (NPQ and the XC) in the four major intertidal benthic diatoms growth forms using unialgal cultures. Remarkably, although motility is restricted to the raphid pennate diatom clade, raphid pennate species, which have adopted a non-motile epipsammic or a tychoplanktonic life style, display the physiological photoprotective response typical of these growth forms. This observation underscores the importance of growth form and not phylogenetic relatedness as the prime determinant shaping the physiological photoprotective capacity of benthic diatoms. PMID:25003964

  16. Developing diatoms for value-added products: challenges and opportunities.

    PubMed

    Fu, Weiqi; Wichuk, Kristine; Brynjlfsson, Sigurur

    2015-12-25

    As a major primary producer in marine environments, diatoms have been considered as promising feedstocks for their applications in functional foods, bioactive pharmaceuticals, and cosmetics. This review focuses on the biotechnology potential of diatoms for value-added products like carotenoids. The impact of abiotic environmental stresses, such as intensity and quality of incident light, nutrient deficiency and silicon depletion, on diatoms has been examined to determine key factors that affect the growth performance and the accumulation of valuable compounds. Previous studies suggested that adaptive evolution could be an efficient method to improve the diatom productivity of valuable compounds. Light emitting diode (LED)-based photobioreactors were introduced and proposed as a promising new technology for producing quality products from diatoms. Currently available molecular biology tools were also summarized and discussed in relation to their application in the production of carotenoids and other valuable products. Taken together, systems biology and synthetic biology approaches have the potential to address the challenges faced while working toward the industrial application of diatoms. PMID:25882605

  17. Growth form defines physiological photoprotective capacity in intertidal benthic diatoms.

    PubMed

    Barnett, Alexandre; Mlder, Vona; Blommaert, Lander; Lepetit, Bernard; Gaudin, Pierre; Vyverman, Wim; Sabbe, Koen; Dupuy, Christine; Lavaud, Johann

    2015-01-01

    In intertidal marine sediments, characterized by rapidly fluctuating and often extreme light conditions, primary production is frequently dominated by diatoms. We performed a comparative analysis of photophysiological traits in 15 marine benthic diatom species belonging to the four major morphological growth forms (epipelon (EPL), motile epipsammon (EPM-M) and non-motile epipsammon (EPM-NM) and tychoplankton (TYCHO)) found in these sediments. Our analyses revealed a clear relationship between growth form and photoprotective capacity, and identified fast regulatory physiological photoprotective traits (that is, non-photochemical quenching (NPQ) and the xanthophyll cycle (XC)) as key traits defining the functional light response of these diatoms. EPM-NM and motile EPL showed the highest and lowest NPQ, respectively, with EPM-M showing intermediate values. Like EPL, TYCHO had low NPQ, irrespective of whether they were grown in benthic or planktonic conditions, reflecting an adaptation to a low light environment. Our results thus provide the first experimental evidence for the existence of a trade-off between behavioural (motility) and physiological photoprotective mechanisms (NPQ and the XC) in the four major intertidal benthic diatoms growth forms using unialgal cultures. Remarkably, although motility is restricted to the raphid pennate diatom clade, raphid pennate species, which have adopted a non-motile epipsammic or a tychoplanktonic life style, display the physiological photoprotective response typical of these growth forms. This observation underscores the importance of growth form and not phylogenetic relatedness as the prime determinant shaping the physiological photoprotective capacity of benthic diatoms. PMID:25003964

  18. Marine Polysaccharide Networks and Diatoms at the Nanometric Scale

    PubMed Central

    Svetličić, Vesna; Žutić, Vera; Pletikapić, Galja; Radić, Tea Mišić

    2013-01-01

    Despite many advances in research on photosynthetic carbon fixation in marine diatoms, the biophysical and biochemical mechanisms of extracellular polysaccharide production remain significant challenges to be resolved at the molecular scale in order to proceed toward an understanding of their functions at the cellular level, as well as their interactions and fate in the ocean. This review covers studies of diatom extracellular polysaccharides using atomic force microscopy (AFM) imaging and the quantification of physical forces. Following a brief summary of the basic principle of the AFM experiment and the first AFM studies of diatom extracellular polymeric substance (EPS), we focus on the detection of supramolecular structures in polysaccharide systems produced by marine diatoms. Extracellular polysaccharide fibrils, attached to the diatom cell wall or released into the surrounding seawater, form distinct supramolecular assemblies best described as gel networks. AFM makes characterization of the diatom polysaccharide networks at the micro and nanometric scales and a clear distinction between the self-assembly and self-organization of these complex systems in marine environments possible. PMID:24113585

  19. Prospects for radiocarbon dating diatom-bound organic compounds

    NASA Astrophysics Data System (ADS)

    Ingalls, A. E.; Anderson, R. F.; Pearson, A.; Lee, C.

    2003-04-01

    Obtaining accurate radiocarbon chronologies for sedimentary deposits lacking calcium carbonate has been an obstacle to understanding biogeochemical cycling in several oceanic regions including the North Pacific and the Southern Ocean. Attempts to use organic carbon instead of calcium carbonate have been unsuccessful due to problems with contamination and diagenesis. Here we apply compound-specific radiocarbon dating of diatom frustule-bound organic compounds toward the goal of developing age chronologies for sediment cores from the Southern Ocean. Diatom frustules-bound organic carbon is both from a known phytoplankton source and is relatively unaltered by diagenesis on thousand year time-scales. Sediment samples are acid hydrolyzed and solvent extracted to remove non diatom-bound organic matter. The cleaned sediment is digested in HF. Diatom-bound organic compounds are identified and isolated using liquid chromatography-mass spectrometry (LC-MS) and collected using an automated fraction collector. LC-MS and NMR analyses suggest that a major component of diatom-bound organic matter is present as long chain polyamines. Individual fractions of polyamines are then radiocarbon dated using Accelerator Mass Spectrometry. We will present data comparing the radiocarbon age of diatom-bound polyamines to that of calcium carbonate from a Southern Ocean sediment core.

  20. Adsorption of diatoms at the oil-water interface

    NASA Astrophysics Data System (ADS)

    Fathollahi, Niloofar; Sheng, Jian

    2013-11-01

    Statistically robust experimental observations on 3D trajectory of diatoms approaching an oil-water interface is crucial for understanding sorption mechanisms of active particles, and interfacial rheology with over-arching implications in interfacial dynamics, droplet break and coalescence. Digital Holographic Cinematography is utilized to measure 3-D trajectories of diatoms, Thalassiosira pseudomona and T. weissflogii and simultaneously track the interface. Experiments are conducted in a 300 × 100 × 100 mm chamber containing 32 ppt artificial seawater. A stationary pendant drop is created on the tip of a needle located at the center of the chamber. Three oil samples, Louisiana crude, hexadecane, and mineral oil, are used. Diatoms are injected at a height above the drop with a negligible velocity, where Diatom precipitates freely on its excess weight. Holograms of diatom and drop are recorded at 5 fps with a magnification of 1.3X and are streamed in real time allowing for long-term study of sorption onto a slowly aging interface. A novel autofocus algorithm enables us to determine 3D locations within an uncertainty of 0.05 particle diameter. This allows us to perform super-resolution measurement to determine the effects of location and orientation of diatoms on the adsorption rate at the oil-water interface. Funded by GoMRI.

  1. The diatom molecular toolkit to handle nitrogen uptake.

    PubMed

    Rogato, Alessandra; Amato, Alberto; Iudicone, Daniele; Chiurazzi, Maurizio; Ferrante, Maria Immacolata; d'Alcal, Maurizio Ribera

    2015-12-01

    Nutrient concentrations in the oceans display significant temporal and spatial variability, which strongly affects growth, distribution and survival of phytoplankton. Nitrogen (N) in particular is often considered a limiting resource for prominent marine microalgae, such as diatoms. Diatoms possess a suite of N-related transporters and enzymes and utilize a variety of inorganic (e.g., nitrate, NO3(-); ammonium, NH4(+)) and organic (e.g., urea; amino acids) N sources for growth. However, the molecular mechanisms allowing diatoms to cope efficiently with N oscillations by controlling uptake capacities and signaling pathways involved in the perception of external and internal clues remain largely unknown. Data reported in the literature suggest that the regulation and the characteristic of the genes, and their products, involved in N metabolism are often diatom-specific, which correlates with the peculiar physiology of these organisms for what N utilization concerns. Our study reveals that diatoms host a larger suite of N transporters than one would expected for a unicellular organism, which may warrant flexible responses to variable conditions, possibly also correlated to the phases of life cycle of the cells. All this makes N transporters a crucial key to reveal the balance between proximate and ultimate factors in diatom life. PMID:26055207

  2. Radiocarbon dating of diatom-bound organic compounds

    NASA Astrophysics Data System (ADS)

    Hatte, C.; Hodgins, G.; Jull, T.; Cruz, R.; Lange, T.; Biddulph, D.

    2006-12-01

    We present a new method for obtaining radiocarbon dates for the proteins intrinsic to diatom frustules (sillafin). By asserting age models for sediment cores that lack calcium carbonate, this method will improve interpretations of diatom-based paleoproxies either marine or lacustrine. In preparation for radiocarbon dating by Accelerator Mass Spectrometry, diatoms were first concentrated out of the sediment. Through chemical and physical treatments that will be discussed and compared here, diatoms frustules are then freed of any surface-bound organic matter. Compounds intrinsic to diatoms frustules are then released from their opal matrix by HF dissolution. Since we have eliminated any of potentially contaminating organic matter, this method differs from approaches based on specific compounds extraction from a complex organic mixture by preparative chromatography such as proposed by Ingalls et al. (2004, Mar. Chem). The advantage of our method is that it does not require heavy cost investment. The method was applied to samples from a marine core collected in the Southern Ocean, that spans the last climatic cycle. Diatoms rich sediments from a Holocene lacustrine/palustrine record from Texas were also investigated. We report on the radiocarbon dating results obtained on organic matter at each step of the chemical treatment, from bulk to sillafin and their interpretation.

  3. Molecular identification of sequestered diatom chloroplasts and kleptoplastidy in foraminifera.

    PubMed

    Pillet, Loïc; de Vargas, Colomban; Pawlowski, Jan

    2011-07-01

    Kleptoplastidy is the ability of heterotrophic organisms to preserve chloroplasts of algal preys they eat and partially digest. As the sequestered chloroplasts stay functional for months, the "host" becomes photosynthetically active. Although remaining a marginal process, kleptoplastidy was observed in different protist lineages, including foraminifera. Previous studies showed at least eight species of the foraminiferal genera Haynesina and Elphidium grazing on diatoms and husbanding their chloroplasts. In order to characterize more precisely the origin of kleptochloroplasts in these genera, we obtained 1027 chloroplastic 16S rDNA sequences from 13 specimens of two Haynesina and five Elphidium species. We identified the foraminiferal kleptochloroplasts using a reference phylogeny made of 87 chloroplastic sequences of known species of diatoms and brown algae. All the analyzed specimens were performing kleptoplastidy and according to our phylogenetic analyses they seem to retain exclusively chloroplasts of diatom origin. There is no apparent specificity for the type of diatom from which chloroplasts originated, however some foraminiferal species seem to accept a wider range of diatoms than others. Possibly the diversity of kleptochloroplasts depends on the type of diatoms the foraminiferans feed on. PMID:21130034

  4. The pharmacologic basis for the treatment of endocrinopathic laminitis.

    PubMed

    Durham, Andy

    2010-08-01

    Although the treatment and management of laminitis in the horse requires a holistic and often multidisciplinary approach from the veterinarian, farrier, and nutritionist, this review focuses on pharmacologic interventions that might have prophylactic benefit, specifically in the horse with laminitis as a result of pituitary pars intermedia dysfunction and equine metabolic syndrome. PMID:20699177

  5. Micro-crack ultrasound scattering in anisotropic composite laminates

    NASA Astrophysics Data System (ADS)

    Roberts, R. A.

    2013-01-01

    A computational model of ultrasound scattering by micro-cracks in fiber reinforced polymer laminates is presented, foundational to study of micro-crack induced ultrasound attenuation. A model for transmission scattering response is developed using a boundary integral formulation, and associated approximate scattering theories are discussed. Numerical results are presented demonstrating application of the model to laminates containing distributed micro-cracking.

  6. Processing of thermoset prepreg laminate via exposure to microwave radiation

    SciTech Connect

    Paulauskas, F.L.; Meek, T.T.

    1994-06-01

    Studies of microwave-assisted curing of neat resins (epoxy) and unidirectional glass and carbon fiber laminates have shown that a substantial reduction in the curing time was obtained. This may be explained by the penetration of microwave energy directly and throughout the laminate with enhancement of the kinetics of the chemical reaction. Results of this work indicate that the microwave assisted curing of glass fiber laminates also shows a substantial reduction of the required curing time. Microwave radiation of 2.45 GHz has been demonstrated to be an acceptable method to cure unidirectional carbon fiber laminates. Also, effective curing of crossply (0/90) laminates through this method was observed when proper rotation of the parts accompanied the curing process. This is in accordance with previous work. Multidirectional carbon fiber/epoxy laminates demonstrate a lack of coupling during the curing process. A direct curing of these laminates was not possible by microwave radiation with the experimental approach used, in agreement with previous work. Nevertheless, a moderate reduction in the curing time of these thin laminates was observed due to hybrid curing.

  7. Better Thermal Insulation in Solar-Array Laminators

    NASA Technical Reports Server (NTRS)

    Burger, D. R.; Knox, J. F.

    1984-01-01

    Glass marbles improve temperature control. Modified vacuum laminator for photovoltaic solar arrays includes thermal insulation made of conventional glass marbles. Marbles serve as insulation for temperature control of lamination process at cure temperatures as high as 350 degrees F. Used to replace original insulation made of asbestos cement.

  8. Fabrication of Multi-Ply Birefringent Fibrous Composite Laminates

    NASA Technical Reports Server (NTRS)

    Daniel, I.; Niiro, T.

    1984-01-01

    Fabrication method produces unidirectional, multi-ply, transparent birefringent fibrous composite laminates for use in macromechanical stress analysis conducted by means of anisotropic photoelasticity. New laminates glass-fiber-reinforced plastics for which matrix and fibers have same index of refraction. Method utilized in structural applications of composites.

  9. Curvature shape based impact damage detection in composite laminates

    NASA Astrophysics Data System (ADS)

    Feng, Kan; Li, Zheng; Gong, Xiaojing

    2014-02-01

    In this study a vibration-based damage detection method-2D GSM (Two-Dimensional Gapped Smoothing Method), for plate-like structure is presented. A kind of typical carbon fibre reinforced composite laminate is studied as a quasi-isotropic and quasi-homogeneous material. The impact damage was produced by a drop weight acting on the surface of unidirectional tensile stressed composite laminate. For the delamination detaction of laminate by 2D GSM, PZT patches were arranged as actuators to excite the torsion mode of laminate under a certain frequency. By changing the frequency and the phase of signal inputted into each patch, we can actuate the laminate into different operational deflection shapes (ODSs). The deflection shapes of laminate are measured by a Scanning Laser Doppler Vibrometer (SLDV) system. A curvature shape based Two Dimensional Gapped Smoothing Method (2D GSM) is proposed and applied to locate the delamination of laminate caused by impact. The result shows that the 2D GSM is an efficient way for the damage detection in composite laminates.

  10. Fracture toughness and impact properties of laminated metal composites

    SciTech Connect

    Lesuer, D.R.; Riddle, R.A.; Gogolewski, R.P.; Syn, C.K.; Cunningham, B.J.

    1996-03-04

    Laminated metal composites consist of alternating metal (or metal matrix composite) layers bonded together. These materials can provide fracture toughness and impact properties superior to those of the component materials. These properties are a function of component material properties, laminate architecture (volume fraction, thickness) and interface properties. Properties are compared for seven lightweight materials.

  11. Hole-thru-laminate mounting supports for photovoltaic modules

    SciTech Connect

    Wexler, Jason; Botkin, Jonathan; Culligan, Matthew; Detrick, Adam

    2015-02-17

    A mounting support for a photovoltaic module is described. The mounting support includes a pedestal having a surface adaptable to receive a flat side of a photovoltaic module laminate. A hole is disposed in the pedestal, the hole adaptable to receive a bolt or a pin used to couple the pedestal to the flat side of the photovoltaic module laminate.

  12. Self-heating forecasting for thick laminate specimens in fatigue

    NASA Astrophysics Data System (ADS)

    Lahuerta, F.; Westphal, T.; Nijssen, R. P. L.

    2014-12-01

    Thick laminate sections can be found from the tip to the root in most common wind turbine blade designs. Obtaining accurate and reliable design data for thick laminates is subject of investigations, which include experiments on thick laminate coupons. Due to the poor thermal conductivity properties of composites and the material self-heating that occurs during the fatigue loading, high temperature gradients may appear through the laminate thickness. In the case of thick laminates in high load regimes, the core temperature might influence the mechanical properties, leading to premature failures. In the present work a method to forecast the self-heating of thick laminates in fatigue loading is presented. The mechanical loading is related with the laminate self-heating, via the cyclic strain energy and the energy loss ratio. Based on this internal volumetric heat load a thermal model is built and solved to obtain the temperature distribution in the transient state. Based on experimental measurements of the energy loss factor for 10mm thick coupons, the method is described and the resulting predictions are compared with experimental surface temperature measurements on 10 and 30mm UD thick laminate specimens.

  13. A MEMS lamination technology based on sequential multilayer electrodeposition

    SciTech Connect

    Kim, M; Kim, J; Herrault, F; Schafer, R; Allen, MG

    2013-08-06

    A MEMS lamination technology based on sequential multilayer electrodeposition is presented. The process comprises three main steps: (1) automated sequential electrodeposition of permalloy (Ni80Fe20) structural and copper sacrificial layers to form multilayer structures of significant total thickness; (2) fabrication of polymeric anchor structures through the thickness of the multilayer structures and (3) selective removal of copper. The resulting structure is a set of air-insulated permalloy laminations, the separation of which is sustained by insulating polymeric anchor structures. Individual laminations have precisely controllable thicknesses ranging from 500 nm to 5 mu m, and each lamination layer is electrically isolated from adjacent layers by narrow air gaps of similar scale. In addition to air, interlamination insulators based on polymers are investigated. Interlamination air gaps with very high aspect ratio (>1:100) can be filled with polyvinylalcohol and polydimethylsiloxane. The laminated structures are characterized using scanning electron microscopy and atomic force microscopy to directly examine properties such as the roughness and the thickness uniformity of the layers. In addition, the quality of the electrical insulation between the laminations is evaluated by quantifying the eddy current within the sample as a function of frequency. Fabricated laminations are comprised of uniform, smooth (surface roughness < 100 nm) layers with effective electrical insulation for all layer thicknesses and insulator approaches studied. Such highly laminated structures have potential uses ranging from energy conversion to applications where composite materials with highly anisotropic mechanical or thermal properties are required.

  14. Laminated sheet composites reinforced with modular filament sheet

    NASA Technical Reports Server (NTRS)

    Reece, O. Y.

    1968-01-01

    Aluminum and magnesium composite sheet laminates reinforced with low density, high strength modular filament sheets are produced by diffusion bonding and explosive bonding. Both processes are accomplished in normal atmosphere and require no special tooling or cleaning other than wire brushing the metal surfaces just prior to laminating.

  15. Molecular Fossils as Time Indicators for the Evolution of Diatoms.

    NASA Astrophysics Data System (ADS)

    Rampen, S. W.; Schouten, S.; Muyzer, G.; Abbas, B.; Rowland, S. J.; Moldowan, M.; Sinninghe Damst, J. S.

    2004-12-01

    Bacillariophyta (diatoms) are one of the most abundant divisions of phytoplankton, and contribute to almost 50% of the primary productivity of today's oceans. However, their ecological dominance is relatively young and little is known about the exact pace of their rapid evolution. DNA analyses on diatoms and the use of molecular clock calculations can help to reconstruct their evolution, but this molecular clock rate needs to be calibrated against the fossil record to determine the mutation rate. Until now, diatom silica skeletons have been used for reconstructing the evolution of diatoms, but their use is limited due to destruction by diagenesis. Molecular fossils may prove to be more useful for time reconstruction. To search for suitable compounds, we have analyzed both the lipid composition and 18S rRNA sequences of ca. 100 marine diatoms. This revealed that some specific phylogenetic clusters within the diatoms produce specific organic compounds, so-called diatom biomarkers. One group of diatom biomarkers are the C25 highly branched isoprenoid (HBI) alkenes (1,2). HBI biosynthesis evolved independently at least twice in the diatoms. The first group of HBI producers consists of the centric diatoms of the genus Rhizosolenia, the second group comprises pennate diatoms of the genera Haslea, Navicula and Pleurosigma. Based on the constructed phylogenetic tree it is likely that the HBI biosynthesis evolved first in the older group of centric diatoms (i.e. the Rhizosolenia genus). The fossil record was studied to determine the geological occurrence of C25 HBI alkenes, and this data set shows that HBI biosynthesis evolved ca. 91.5 My ago, so we can date the evolution of the genus Rizosolenia to ca. 91.5 My. With this information, we can now accurately predict the mutation rate of the 18S rDNA gene to 1% per 14.8 My for Rhizosolenia, which is substantially faster than the 1% per 18-26 My reported previously for diatoms in general. Another specific biomarker is 24-norsterol. Its value as an age diagnostic biomarker was already reported (3), but the source of this sterol was still unknown although a diatomaceous source was assumed. We have now found this sterol in the diatom species Thalassiosira aff. Antarctica. In combination with the knowledge that the 24-norsterol production increased substantially during the Cretaceous this may provide a tool to predict the mutation rate of the Thalassiosirales. Our data show that molecular paleontology can assist in obtaining more reliable estimates of the molecular clock rate and thus be an important tool in reconstructing the evolution of diatoms. References: 1. J.K. Volkman et al., Org.Geochem. 21, 407-413 (1994). 2. J.S. Sinninghe Damst et al., Science 304, 584-587 (2004). 3. A.G. Holba et al., Org.Geochem. 29, 1269-1283 (1998).

  16. The paleoclimatology of Lake Baikal: A diatom synthesis and prospectus

    NASA Astrophysics Data System (ADS)

    Mackay, Anson W.

    2007-06-01

    The paleoclimatic archive held in Lake Baikal sediments is of significant importance, given the lake's position in one of the world's most continental regions where there are few continuous, high quality records spanning the Quaternary. Here I review diatom and associated biogenic silica records from Lake Baikal sediments and provide a paleoclimatic synthesis of changes at various timescales over the Quaternary. I initially highlight major climatic and hydrological aspects of Lake Baikal, as understanding the contemporary system (both regionally and within the lake) are fundamental to understanding past change interpreted from the sedimentary archive. In this respect, special attention is given to factors that can affect the integrity of the diatom record, most notably dissolution processes. These mechanisms are likely to have had a relatively greater impact on the preservation of diatom valves during glacial periods because of overall lower diatom productivity. Lower diatom numbers and relative increased dissolution during cold periods explains the lack of diatoms and low biogenic silica concentrations found in the lake sediments during glacial periods. The biogenic record highlights the nature of the 100 ka cycle especially during the last 800 ka, although there is also a strong precessional component. Further work is needed to reassess biological responses in Lake Baikal with respect to different orbital forcing mechanisms, together with their impacts on evolution and speciation of diatoms. The biological record from Lake Baikal confirms that the last interglacial in central Asia lasted approximately 10.5 ka. Productivity in the lake (as inferred from diatom biovolume accumulation rates) exhibits millennial-scale variability with the occurrence of centennial-scale reductions in diatom biomass throughout the last interglacial period. The most severe reduction in diatom biomass (at c. 120 ka BP) is concurrent with millennial-scale cooling in the North Atlantic region. Links to changes in North Atlantic ocean thermohaline circulation via teleconnections are also evident in the nature of the abrupt ecological changes in the lake throughout the last 60 ka, linked to ice-rafting into the North Atlantic, otherwise known as Heinrich events. New robust radiocarbon chronologies for sediments deposited during the late glacial and Holocene in Lake Baikal allow detailed, multi-decadal records to be constructed for the last 14,000 years. Cooling events associated with millennial-scale cycles are also apparent in the Lake Baikal record, and both the diatom record and oxygen isotope record of the diatom silica highlight that biological responses to these abrupt events are almost simultaneous. Comparisons made between Lake Baikal records with others worldwide highlights that many of the Holocene cooling events are associated with melt-water outburst from the Laurentide ice sheet, and changes in solar insolation. During the last 1000 years, snow cover on Lake Baikal has been inferred from past diatom assemblages, and is closely linked to weakening of the North Atlantic Oscillation, allowing increasing intensity of the Siberian High to develop and during the 17th and 18th centuries. In the last 150 years, diatom species have been shown to be sensitive indicators of recent warming. However, impacts from future global warming will be complex, and are likely to impact not only on the balance between endemic and cosmopolitan diatoms throughout the lake, but on the balance between siliceous and non-siliceous algae, and sources of primary productivity.

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

    NASA Astrophysics Data System (ADS)

    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. 2009. The rivers are alive: on the potential for diatoms as a tracer of water source and hydrological connectivity. Hydrological Processes 23: 2841-2845. Pfister L, Wetzel CE, Martínez-Carreras N, Frentress J, Ector L, Hoffmann L, McDonnell JJ. 2011. Do diatoms run downhill? Using biodiversity of terrestrial and aquatic diatoms to identify hydrological connectivity between aquatic zones in Luxembourg. AGU Fall Meeting. Tauro F, Martínez-Carreras N, Wetzel CE, Hissler C, Barnich F, Frentress J, Ector L, Hoffmann L, McDonnell JJ, Pfister L. 2013. Fluorescent diatoms as hydrological tracers: a proof of concept percolation experiment. EGU abstract, EGU2013-7687-4. van Dam H, Mertens A, Sinkeldam J. 1994. A coded checklist and ecological indicator values of freshwater diatoms from the Netherlands. Netherlands Journal of Aquatic Ecology 28:117-133.

  18. The mechanical behavior of GLARE laminates for aircraft structures

    NASA Astrophysics Data System (ADS)

    Wu, Guocai; Yang, J.-M.

    2005-01-01

    GLARE (glass-reinforced aluminum laminate) is a new class of fiber metal laminates for advanced aerospace structural applications. It consists of thin aluminum sheets bonded together with unidirectional or biaxially reinforced adhesive prepreg of high-strength glass fibers. GLARE laminates offer a unique combination of properties such as outstanding fatigue resistance, high specific static properties, excellent impact resistance, good residual and blunt notch strength, flame resistance and corrosion properties, and ease of manufacture and repair. GLARE laminates can be tailored to suit a wide variety of applications by varying the fiber/resin system, the alloy type and thickness, stacking sequence, fiber orientation, surface pretreatment technique, etc. This article presents a comprehensive overview of the mechanical properties of various GLARE laminates under different loading conditions.

  19. The strength of laminated composite materials under repeated impact loading

    NASA Technical Reports Server (NTRS)

    Rotem, Assa

    1988-01-01

    When low velocity and energy impact is exerted on a laminated composite material, in a perpendicular direction to the plane of the laminate, invisible damage may develop. It is shown analytically and experimentally that the invisible damage occurs during the first stage of contact between the impactor and the laminate and is a result of the contact stresses. However, the residual flexural strength changes only slightly, because it depends mainly on the outer layers, and these remain undamaged. Repeated impact intensifies the damage inside the laminate and causes larger bending under equivalent impact load. Finally, when the damage is most severe, even though it is still invisible, the laminate fails because of bending on the tension side. If the repeated impact is halted before final fracture occurs the residual strength and modulus would decrease by a certain amount.

  20. Diverse lamin-dependent mechanisms interact to control chromatin dynamics

    PubMed Central

    Camozzi, Daria; Capanni, Cristina; Cenni, Vittoria; Mattioli, Elisabetta; Columbaro, Marta; Squarzoni, Stefano; Lattanzi, Giovanna

    2014-01-01

    Interconnected functional strategies govern chromatin dynamics in eukaryotic cells. In this context, A and B type lamins, the nuclear intermediate filaments, act on diverse platforms involved in tissue homeostasis. On the nuclear side, lamins elicit large scale or fine chromatin conformational changes, affect DNA damage response factors and transcription factor shuttling. On the cytoplasmic side, bridging-molecules, the LINC complex, associate with lamins to coordinate chromatin dynamics with cytoskeleton and extra-cellular signals. Consistent with such a fine tuning, lamin mutations and/or defects in their expression or post-translational processing, as well as mutations in lamin partner genes, cause a heterogeneous group of diseases known as laminopathies. They include muscular dystrophies, cardiomyopathy, lipodystrophies, neuropathies, and progeroid syndromes. The study of chromatin dynamics under pathological conditions, which is summarized in this review, is shedding light on the complex and fascinating role of the nuclear lamina in chromatin regulation. PMID:25482195

  1. Matrix cracking in laminated composites under monotonic and cyclic loadings

    NASA Technical Reports Server (NTRS)

    Allen, David H.; Lee, Jong-Won

    1991-01-01

    An analytical model based on the internal state variable (ISV) concept and the strain energy method is proposed for characterizing the monotonic and cyclic response of laminated composites containing matrix cracks. A modified constitution is formulated for angle-ply laminates under general in-plane mechanical loading and constant temperature change. A monotonic matrix cracking criterion is developed for predicting the crack density in cross-ply laminates as a function of the applied laminate axial stress. An initial formulation for a cyclic matrix cracking criterion for cross-ply laminates is also discussed. For the monotonic loading case, a number of experimental data and well-known models are compared with the present study for validating the practical applicability of the ISV approach.

  2. Hygrothermally stable laminated composites with optimal coupling

    NASA Astrophysics Data System (ADS)

    Haynes, Robert Andrew

    This work begins by establishing the necessary and sufficient conditions for hygrothermal stability of composite laminates. An investigation is performed into the range of coupling achievable from within all hygrothermally stable families. The minimum number of plies required to create an asymmetric hygrothermally stable stacking sequence is found to be five. Next, a rigorous and general approach for determining designs corresponding to optimal levels of coupling is established through the use of a constrained optimization procedure. Couplings investigated include extension-twist, bend-twist, extension-bend, shear-twist, and anticlastic. For extension-twist and bend-twist coupling, specimens from five- through ten-ply laminates are manufactured and tested to demonstrate hygrothermal stability and achievable levels of coupling. Nonlinear models and finite element analysis are developed, and predictions are verified through comparison with test results. Sensitivity analyses are performed to demonstrate the robustness of the hygrothermal stability and couplings to deviations in ply angle, typical of manufacturing tolerances. Comparisons are made with current state-of-the-art suboptimal layups, and significant increases in coupling over previously known levels are demonstrated.

  3. Bending analysis of laminated composite box beams

    SciTech Connect

    Tripathy, A.K.; Patel, H.J.; Pang, S.S. . Dept. of Mechanical Engineering)

    1994-01-01

    Box beams are widely used in weight reduction structures such as aircraft wings. The use of composite box beams further reduces the weight factor for such structures with the same deflection and stress as that of isotropic box beams. The difference in the behavior of composite box beam with different fiber orientation, number of plies, and number of stringers also provides a wide range of designing parameters to achieve the required performance for a given problem. A bending analysis has been carried out for the study of deflections and stresses for box beams of different material (isotropic and laminated composites), size, and number of stringers subjected to different kinds of loading conditions. A finite element model has been developed based on the strain energy principle, and the results are compared with an available commercial code COSMOS/M.'' Experiments using aluminum and scotchply composite laminates were conducted to verify the results. An optimal design for size and number of stiffeners for a given loading condition has been achieved. Investigations have also been carried out to find the effect of transverse shear on the span-wise normal stress.

  4. Lamins as mediators of oxidative stress

    SciTech Connect

    Sieprath, Tom; Darwiche, Rabih; De Vos, Winnok H.

    2012-05-18

    Highlights: Black-Right-Pointing-Pointer The nuclear lamina defines structural and functional properties of the cell nucleus. Black-Right-Pointing-Pointer Lamina dysfunction leads to a broad spectrum of laminopathies. Black-Right-Pointing-Pointer Recent data is reviewed connecting laminopathies to oxidative stress. Black-Right-Pointing-Pointer A framework is proposed to explain interactions between lamins and oxidative stress. -- Abstract: The nuclear lamina defines both structural and functional properties of the eukaryotic cell nucleus. Mutations in the LMNA gene, encoding A-type lamins, lead to a broad spectrum of diseases termed laminopathies. While different hypotheses have been postulated to explain disease development, there is still no unified view on the mechanistic basis of laminopathies. Recent observations indicate that laminopathies are often accompanied by altered levels of reactive oxygen species and a higher susceptibility to oxidative stress at the cellular level. In this review, we highlight the role of reactive oxygen species for cell function and disease development in the context of laminopathies and present a framework of non-exclusive mechanisms to explain the reciprocal interactions between a dysfunctional lamina and altered redox homeostasis.

  5. Free Vibration of Uncertain Unsymmetrically Laminated Beams

    NASA Technical Reports Server (NTRS)

    Kapania, Rakesh K.; Goyal, Vijay K.

    2001-01-01

    Monte Carlo Simulation and Stochastic FEA are used to predict randomness in the free vibration response of thin unsymmetrically laminated beams. For the present study, it is assumed that randomness in the response is only caused by uncertainties in the ply orientations. The ply orientations may become random or uncertain during the manufacturing process. A new 16-dof beam element, based on the first-order shear deformation beam theory, is used to study the stochastic nature of the natural frequencies. Using variational principles, the element stiffness matrix and mass matrix are obtained through analytical integration. Using a random sequence a large data set is generated, containing possible random ply-orientations. This data is assumed to be symmetric. The stochastic-based finite element model for free vibrations predicts the relation between the randomness in fundamental natural frequencies and the randomness in ply-orientation. The sensitivity derivatives are calculated numerically through an exact formulation. The squared fundamental natural frequencies are expressed in terms of deterministic and probabilistic quantities, allowing to determine how sensitive they are to variations in ply angles. The predicted mean-valued fundamental natural frequency squared and the variance of the present model are in good agreement with Monte Carlo Simulation. Results, also, show that variations between plus or minus 5 degrees in ply-angles can affect free vibration response of unsymmetrically and symmetrically laminated beams.

  6. Development of a heterogeneous laminating resin system

    NASA Technical Reports Server (NTRS)

    Biermann, T. F.; Hopper, L. C.

    1985-01-01

    The factors which effect the impact resistance of laminating resin systems and yet retain equivalent performance with the conventional 450 K curing epoxy matrix systems in other areas were studied. Formulation work was conducted on two systems, an all-epoxy and an epoxy/bismaleimide, to gain fundamental information on the effect formulation changes have upon neat resin and composite properties. The all-epoxy work involved formulations with various amounts and combinations of eight different epoxy resins, four different hardeners, fifteen different toughening agents, a filler, and a catalyst. The epoxy/bismaleimide effort improved formulations with various amounts and combinations of nine different resins, four different hardeners, eight different toughening agents, four different catalysts, and a filler. When a formulation appeared to offer the proper combination of properties required for a laminating resin Celion 3K-70P fabric was prepregged. Initial screening tests on composites primarily involved Gardner type impact and measurement of short beam shear strengths under dry and hot/wet conditions.

  7. Laminated piezoelectric phononic crystal with imperfect interfaces

    NASA Astrophysics Data System (ADS)

    Lan, Man; Wei, Peijun

    2012-01-01

    Dispersive characteristics of elastic waves propagating through laminated piezoelectric phononic crystal with imperfect interfaces are studied in this paper. First, the transfer matrix method and the Bloch theorem are used to derive the dispersion equation. Next, the imperfect interfaces with the jump of mechanical quantity across interface are considered. In the spring model of imperfect interface, the tractions are continuous, but displacements are discontinuous across the interface. In the mass model of imperfect interface, displacements are continuous, but tractions are discontinuous. In the spring-mass model, both traction and displacement are discontinuous. The effect of imperfect interface is introduced by inserting an additional interface transfer matrix in the calculation of total transfer matrix. Finally, the dispersion equation is solved numerically and the dispersive curves are shown in the Brillouin zone. Band gaps of phononic crystal with imperfect interface are compared with that of phononic crystal with perfect interface. The influences of the imperfect interface on the dispersive curves and the band gaps of periodic laminated piezoelectric composite are discussed.

  8. Bacteria Associated with Benthic Diatoms from Lake Constance: Phylogeny and Influences on Diatom Growth and Secretion of Extracellular Polymeric Substances?

    PubMed Central

    Bruckner, Christian G.; Bahulikar, Rahul; Rahalkar, Monali; Schink, Bernhard; Kroth, Peter G.

    2008-01-01

    The composition of diatom-associated bacterial communities was studied with 14 different unialgal xenic diatom cultures isolated from freshwater epilithic biofilms of Lake Constance, Germany. A clear dominance of Alphaproteobacteria was observed, followed by Betaproteobacteria, Gammaproteobacteria, Bacteroidetes, and Verrucomicrobia. Pure cultures of the diatom Cymbella microcephala, which was found to be dominant in epilithic biofilms in Lake Constance, were cocultivated with six associated bacterial strains. All these bacterial strains were able to grow in C. microcephala cultures in the absence of organic cosubstrates. Diatom growth was generally enhanced in the presence of bacteria, and polysaccharide secretion was generally increased in the presence of Proteobacteria. The monomer composition of extracellular polysaccharides of C. microcephala changed in relation to the presence of different bacteria, but the dominant monomers were less affected. Our results indicate that these changes were caused by the diatom itself rather than by specific bacterial degradation. One Bacteroidetes strain strongly influenced carbohydrate secretion by the alga via extracellular soluble compounds. Biofilms were formed only in the presence of bacteria. Phylogenetic analysis and coculture studies indicate an adaptation of Proteobacteria and Bacteroidetes to the microenvironment created by the diatom biofilm. PMID:18931294

  9. The modern diatom spectra of Madagascar and diatom-inferred Late Quaternary climatic changes in northeastern and central Madagascar

    SciTech Connect

    Reyes, N.E.

    1993-01-01

    A study was conducted to classify diatoms in modern sediment surface samples in freshwater sites into assemblages and to assess the historical changes in lake level changes and climatic conditions in Madagascar during the Late Quaternary. Analysis of taxonomic percentages of diatoms in recently deposited sediments from various sites shows that diatom communities in these sites can be grouped by means of cluster analysis into distinct assemblages, some of which show similarities to groupings found in East Africa. pH and conductivity appear to be important factors correlating with differences in diatom communities in these study sites. Trends in diatom assemblages in a sediment core taken from Lake Alaotra, supplemented by those in sediments of the paleolake Ampasambazimba, suggest that the late Pleistocene in northeastern Madagascar was arid, though aridity was probably not as constant or as severe as in many areas of eastern and northern Africa; the Holocene was a period of moderate but variable conditions, marked by a distinct dry episode ca 5000 yr B.P. and a drying trend toward the late Holocene. Changes in diatom assemblages in a sediment core from Lake Kavitaha in central Madagascar suggest changes in the surrounding environment during at least two periods in the late Holocene. These coincide with increases in charcoal influx and, around 700 yr B.P., with the intensification of agricultural activity in the area.

  10. Seasonal changes of diatom species in the Hooghly estuary, India

    NASA Astrophysics Data System (ADS)

    Goswami, P. K.

    2013-12-01

    The Hooghly estuary is considered as one of the most important fishing ground of north-east India which is mainly because presence of large shallow parts of Bays, which provide extensive growths for benthic and planktonic community and also makes it a highly productive area .Anthropogenic effects induce intensive pressure to this ecosystem ;and consequently results in the eutrophication followed by rapid plankton growth, sometimes even bloom. Diatom comprises one of the most diverse and significant part of the biota of aquatic habitats. Ecologically they are of immense importance since they constitute the podium of food chain and are at pinnacle of the biomass pyramid. The present study was based on the diversity of most dominant diatom species found in the brackish waters of Hooghly estuarine region in three locations of Sagar islands - Gangasagar, Chemaguri and Kachuberia. In this study diatom distribution from post monsoon - pre monsoon period was studied on the specific assemblages of them.. There was wide diversity of diatom species in different locations and in different seasons. Maximum number of diatom species was found in post-monsoon period in Gangasagar and Chemaguri, while in Kachuberia maximum number was found in pre-monsoon period. In Gangasagar, Navicula socialis, Coscinodiscus spp. and Biddulphia spp. were the predominant species in early, mid and late post monsoon period respectively and Biddulphia spp. also continues as the predominant diatom in pre-monsoon period. In Chemaguri, Amphora ostrearia, Coscinodiscus perforatus and Nitzschia acuminate were the predominant species in early, mid and late post monsoon period respectively while Coscinodiscus radiates was the stable predominant diatom species in pre-monsoon period while Thalassionema spp., Ditylum spp., Proboscia spp. and Biddulphia spp. were also found in significantly increased numbers at different times of pre-monsoon period. In Kachuberia area although a wide range of diatoms are present in post-monsoon period it was Coscinodiscus radiates which was the single predominant species found in total pre-monsoon period. Although such changes of diatom species in different seasons may be due to influence of various factors but seasonal changes may be the major factor influencing such changes of diatom species in this area.

  11. Vibrational nonequilibrium effects on diatomic dissociation rates

    NASA Technical Reports Server (NTRS)

    Hansen, C. F.

    1993-01-01

    The collision-induced dissociation rate of diatomic molecules from a ladder of rotational and anharmonic vibrational states is developed, and the correction for vibrational nonequilibrium is considered. The result is similar to an analytic correction derived by Hammerling et al. (1959) for harmonic oscillators. An empirical correction algorithm suggested by Park (1987, 1990) gives similar results when vibrational temperature is comparable to kinetic temperature but underestimates the dissociation rate when vibrational temperature is small compared with the kinetic temperature. This algorithm uses an effective temperature in the experimentally determined Arrhenius expression for the rate coefficient, which is a weighted average of the vibrational and kinetic temperature, whereas theory indicates that kinetic temperature should appear only in the exponential term of the Arrhenius expression. Nevertheless, an effective temperature can always be found that will numerically duplicate the proper rate coefficient at any given condition, but a constant weighting factor cannot be expected to provide this. However, the algorithm can he adjusted to give reasonable results over a range of conditions if the geometric weighting factor is taken to be a simple linear function of the ratio of vibrational to kinetic temperature in the gas.

  12. Diatom milking: a review and new approaches.

    PubMed

    Vinayak, Vandana; Manoylov, Kalina M; Gateau, Hélène; Blanckaert, Vincent; Hérault, Josiane; Pencréac'h, Gaëlle; Marchand, Justine; Gordon, Richard; Schoefs, Benoît

    2015-05-01

    The rise of human populations and the growth of cities contribute to the depletion of natural resources, increase their cost, and create potential climatic changes. To overcome difficulties in supplying populations and reducing the resource cost, a search for alternative pharmaceutical, nanotechnology, and energy sources has begun. Among the alternative sources, microalgae are the most promising because they use carbon dioxide (CO2) to produce biomass and/or valuable compounds. Once produced, the biomass is ordinarily harvested and processed (downstream program). Drying, grinding, and extraction steps are destructive to the microalgal biomass that then needs to be renewed. The extraction and purification processes generate organic wastes and require substantial energy inputs. Altogether, it is urgent to develop alternative downstream processes. Among the possibilities, milking invokes the concept that the extraction should not kill the algal cells. Therefore, it does not require growing the algae anew. In this review, we discuss research on milking of diatoms. The main themes are (a) development of alternative methods to extract and harvest high added value compounds; (b) design of photobioreactors; PMID:25939034

  13. Metatranscriptome analyses indicate resource partitioning between diatoms in the field

    PubMed Central

    Alexander, Harriet; Jenkins, Bethany D.; Rynearson, Tatiana A.; Dyhrman, Sonya T.

    2015-01-01

    Diverse communities of marine phytoplankton carry out half of global primary production. The vast diversity of the phytoplankton has long perplexed ecologists because these organisms coexist in an isotropic environment while competing for the same basic resources (e.g., inorganic nutrients). Differential niche partitioning of resources is one hypothesis to explain this “paradox of the plankton,” but it is difficult to quantify and track variation in phytoplankton metabolism in situ. Here, we use quantitative metatranscriptome analyses to examine pathways of nitrogen (N) and phosphorus (P) metabolism in diatoms that cooccur regularly in an estuary on the east coast of the United States (Narragansett Bay). Expression of known N and P metabolic pathways varied between diatoms, indicating apparent differences in resource utilization capacity that may prevent direct competition. Nutrient amendment incubations skewed N/P ratios, elucidating nutrient-responsive patterns of expression and facilitating a quantitative comparison between diatoms. The resource-responsive (RR) gene sets deviated in composition from the metabolic profile of the organism, being enriched in genes associated with N and P metabolism. Expression of the RR gene set varied over time and differed significantly between diatoms, resulting in opposite transcriptional responses to the same environment. Apparent differences in metabolic capacity and the expression of that capacity in the environment suggest that diatom-specific resource partitioning was occurring in Narragansett Bay. This high-resolution approach highlights the molecular underpinnings of diatom resource utilization and how cooccurring diatoms adjust their cellular physiology to partition their niche space. PMID:25870299

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

    PubMed

    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 ∂(18)O (climate) and carbon cycle records (∂(13)C, and 20-0 Ma pCO2). Warmer climates are strongly correlated with lower diatom diversity (raw: rho = .92, p<.001; detrended, r = .6, p = .01). Diatoms were 20% less diverse in the early late Miocene, when temperatures and pCO2 were only moderately higher than today. Diversity is strongly correlated to both ∂(13)C 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. PMID:24465441

  15. What controls silicon isotope fractionation during dissolution of diatom opal?

    NASA Astrophysics Data System (ADS)

    Wetzel, F.; de Souza, G. F.; Reynolds, B. C.

    2014-04-01

    The silicon isotope composition of opal frustules from photosynthesising diatoms is a promising tool for studying past changes in the marine silicon cycle, and indirectly that of carbon. Dissolution of this opal may be accompanied by silicon isotope fractionation that could disturb the pristine silicon isotope composition of diatom opal acquired in the surface ocean. It has previously been shown that dissolution of fresh and sediment trap diatom opal in seawater does fractionate silicon isotopes. However, as the mechanism of silicon isotope fractionation remained elusive, it is uncertain whether opal dissolution in general is associated with silicon isotope fractionation considering that opal chemistry and surface properties are spatially and temporally (i.e. opal of different age) diverse. In this study we dissolved sediment core diatom opal in 5 mM NaOH and found that this process is not associated with significant silicon isotope fractionation. Since no variability of the isotope effect was observed over a wide range of dissolution rates, we can rule out the suggestion that back-reactions had a significant influence on the net isotope effect. Similarly, we did not observe an impact of temperature, specific surface area, or degree of undersaturation on silicon isotope partitioning during dissolution, such that these can most likely also be ruled out as controlling factors. We discuss the potential impacts of the chemical composition of the dissolution medium and age of diatom opal on silicon isotope fractionation during dissolution. It appears most likely that the controlling mechanism of silicon isotope fractionation during dissolution is related to the reactivity, or potentially, aluminium content of the opal. Such a dependency would imply that silicon isotope fractionation during dissolution of diatom opal is spatially and temporally variable. However, since the isotope effects during dissolution are small, the silicon isotope composition of diatom opal appears to be robust against dissolution in the deep sea sedimentary environment.

  16. Cenozoic Planktonic Marine Diatom Diversity and Correlation to Climate Change

    PubMed Central

    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, p<.001; detrended, r = .6, p = .01). Diatoms were 20% less diverse in the early late Miocene, when temperatures and pCO2 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. PMID:24465441

  17. New laminated displacement-discontinuity program: Fundamental behavior

    SciTech Connect

    Heasley, K.A.; Salamon, M.D.G.

    1996-12-01

    In the past, numerous displacement-discontinuity (DID) models of stratified rock masses have been proposed using a homogeneous isotropic elastic overburden. In this paper, it is postulated that a laminated overburden model might be more accurate for describing the displacements and stress in these stratified deposits. In order to investigate the utility of using a laminated overburden in a DID model, the fundamental mathematical basis of the laminated model is presented and graphically compared with the fundamental behavior of homogeneous isotropic elastic overburden and with field data. Specifically, the stresses and displacements surrounding an idealized longwall panel as determined from the laminated overburden model are presented and compared with results from the homogeneous isotropic overburden and with measured abutment stress data. Also, the remote displacements and surface subsidence as calculated by the laminated overburden model are compared with homogeneous isotropic calculations and with measured subsidence data. The results of this investigation show that the laminated overburden is more supple, apt to propagate displacements and stress further, and better able to fit observed data than the classic homogeneous isotropic overburden. Ultimately, it is suggested that the laminated model has the potential to increase the accuracy of displacement and stress calculations for a variety of mining situations.

  18. Low cost and high performance screen laminate regenerator matrix

    NASA Astrophysics Data System (ADS)

    Bin-Nun, Uri; Manitakos, Dan

    2004-06-01

    A laminate screen matrix regenerator with 47 elements has been designed, analyzed, fabricated and tested. The laminate was fabricated from stainless steel screen sheets that were stacked on top of each other at certain angular orientation and then bonded at high temperature and pressure environment utilizing a sintering process. This laminate is a porous structure media with highly repeatable properties that can be controlled by varying mesh size, weave type, wire size and laminate sheet to sheet orientation. The flow direction in relation to the weave plan can be varied by cutting a cylindrical or rectangular laminate element along or across the weave. The regenerator flow resistance, thermal conductance losses, dead volume, surface area and heat transfer coefficient are analyzed. Regenerator cost and performance comparison data between the conventional widely used method of stacked screens and the new stacked laminate matrix regenerator is discussed. Also, a square stainless steel screen laminate was manufactured in a way which permits gas to flow along the screen wire instead of across it.

  19. Formaldehyde and TVOC emission behavior of laminate flooring by structure of laminate flooring and heating condition.

    PubMed

    An, Jae-Yoon; Kim, Sumin; Kim, Hyun-Joong

    2011-03-15

    Formaldehyde was measured with a desiccator, a 20 L chamber and the FLEC method. The formaldehyde emission rate from laminate was the highest at 32 °C using the desiccator, which then decreased with time. The formaldehyde emission using the 20 L small chamber and FLEC showed a similar tendency. There was a strong correlation between the formaldehyde and total volatile organic compounds (TVOCs) with both types of floorings using the two different methods. The formaldehyde emission rate and TVOC results were higher when tested using the FLEC method than with the 20 L small chamber method. The emission rate was affected by the joint edge length in laminate flooring. Toluene, ethylbenzene and xylene were the main VOCs emitted from laminate flooring, and there were more unidentified VOCs emitted than identified VOCs. The samples heated with a floor heating system emitted more formaldehyde than those heated using an air circulation system due to the temperature difference between the bottom panel and flooring. The TVOC emission level of the samples was higher when an air circulation system was used than when a floor heating system was used due to the high ventilation rate. PMID:20870352

  20. The Creep of Laminated Synthetic Resin Plastics

    NASA Technical Reports Server (NTRS)

    Perkuhn, H

    1941-01-01

    The long-time loading strength of a number of laminated synthetic resin plastics was ascertained and the effect of molding pressure and resin content determined. The best value was observed with a 30 to 40 percent resin content. The long-time loading strength also increases with increasing molding pressure up to 250 kg/cm(exp 2); a further rise in pressure affords no further substantial improvement. The creep strength is defined as the load which in the hundredth hour of loading produces a rate of elongation of 5 X 10(exp -4) percent per hour. The creep strength values of different materials were determined and tabulated. The effect of humidity during long-term tests is pointed out.

  1. Transient response of a laminated composite plate

    NASA Technical Reports Server (NTRS)

    Datta, S. K.; Ju, T. H.; Bratton, R. L.; Shah, A. H.

    1992-01-01

    Results are presented from an investigation of the effect of layering on transient wave propagation in a laminated cross-ply plate, giving attention to the case of 2D plane strain in the case where a line vertical force is applied on a free surface of the plate; the line may be either parallel or perpendicular to the fibers in a ply. The results are in both the time and frequency domains for the normal stress component in the x direction, at a point on the surface of the plate on which the force is applied. Comparative results are also presented for a homogeneous plate whose properties are the static effective ones, when the number of plies is large.

  2. Permeability After Impact Testing of Composite Laminates

    NASA Technical Reports Server (NTRS)

    Nettles, A.T.; Munafo, Paul (Technical Monitor)

    2002-01-01

    Since composite laminates are beginning to be identified for use in reusable launch vehicle propulsion systems, an understanding of their permeance is needed. A foreign object impact event can cause a localized area of permeability (leakage) in a polymer matrix composite and it is the aim of this study to assess a method of quantifying permeability-after-impact results. A simple test apparatus is presented and variables that could affect the measured values of permeability-after-impact were assessed. Once it was determined that valid numbers were being measured, a fiber/resin system was impacted at various impact levels and the resulting permeability measured, first with a leak check solution (qualitative) then using the new apparatus (quantitative). The results showed that as the impact level increased, so did the measured leakage. As the pressure to the specimen was increased, the leak rate was seen to increase in a non-linear fashion for almost all of the specimens tested.

  3. Permeability After Impact Testing of Composite Laminates

    NASA Technical Reports Server (NTRS)

    Nettles, Alan T.

    2003-01-01

    Since composite laminates are beginning to be identified for use in reusable launch vehicle propulsion systems, an understanding of their permeance is needed. A foreign object impact event can cause a localized area of permeability (leakage) in a polymer matrix composite and it is the aim of this study to assess a method of quantifying permeability-after-impact results. A simple test apparatus is presented and variables that could affect the measured values of permeability-after-impact were assessed. Once it was determined that valid numbers were being measured, a fiber/resin system was impacted at various impact levels and the resulting permeability measured, first with a leak check solution (qualitative) then using the new apparatus (quantitative). The results showed that as the impact level increased, so did the measured leakage. As the pressure to the specimen was increased, the leak rate was seen to increase in a non-linear fashion for almost all of the specimens tested.

  4. Eddy current losses in ferromagnetic laminations

    SciTech Connect

    Serpico, C.; Visone, C.; Mayergoyz, I. D.; Basso, V.; Miano, G.

    2000-05-01

    It is demonstrated through the comparison of analytical, numerical, and experimental results that the existence of excess eddy current losses can be explained by the peculiar nature of the nonlinear diffusion of electromagnetic fields in magnetically nonlinear laminations. The essence of this peculiar nature is that nonlinear diffusion occurs as inward progress of almost rectangular profiles of magnetic flux density of variable height. Approximating actual profiles of magnetic flux density by rectangular ones, the problem of nonlinear diffusion can be treated analytically by using a simple model. The accuracy and the limit of applicability of the rectangular profile model are discussed by comparing its predictions with finite elements numerical solutions of nonlinear diffusion equation as well as with experimental results. (c) 2000 American Institute of Physics.

  5. Analysis of "Kiss" Bonds Between Composite Laminates

    NASA Astrophysics Data System (ADS)

    Poveromo, Scott L.; Earthman, James C.

    2014-06-01

    One of the leading challenges to designing lightweight, cost-effective bonded structures is to detect low shear strength "kiss" bonds where no other defects such as voids and cracks exist. To develop a nondestructive testing method that is sensitive to kiss bonds, standards need to be fabricated with known strength values. In the current work, we attempt to create kiss bonds in between carbon fiber composite laminates that have been bonded with epoxy film adhesive and epoxy paste adhesive. Based on ultrasonic testing, when creating true kiss bonds using film adhesives, a complete disbond could not be avoided because of thermally induced stresses during the high-temperature cure. However, further work demonstrated that kiss bonds can be formed using room-temperature curable epoxy paste adhesives by creating an amine blush on the epoxy surface or applying a release agent on the bonding surfaces.

  6. Compression failure of angle-ply laminates

    NASA Technical Reports Server (NTRS)

    Peel, L. D.; Hyer, M. W.; Shuart, M. J.

    1992-01-01

    Test results from the compression loading of (+ or - Theta/ - or + Theta)(sub 6s) angle-ply IM7-8551-7a specimens, 0 less than or = Theta less than or = 90 degs, are presented. The observed failure strengths and modes are discussed, and typical stress-strain relations shown. Using classical lamination theory and the maximum stress criterion, an attempt is made to predict failure stress as a function of Theta. This attempt results in poor correlation with test results and thus a more advanced model is used. The model, which is based on a geometrically nonlinear theory, and which was taken from previous work, includes the influence of observed layer waviness. The waviness is described by the wave length and the wave amplitude. The theory is briefly described and results from the theory are correlated with test results. It is shown that by using levels of waviness observed in the specimens, the correlation between predictions and observations is good.

  7. Failure mechanisms in tapered laminated composites

    NASA Astrophysics Data System (ADS)

    Kim, R.; Miravete, A.; Baselga, S.; Bravo, P. M.

    The fracture behavior of tapered laminated composite plates subjected to transverse load has been studied. Three-point bending tests were carried out for static and fatigue analysis. Longitudinal and interlaminar strains were measured by means of a number of gauges set in critical places. The angle of variation of thickness, the aspect ratio (span/thickness) and the type of loading (static or fatigue) are the parameters that define the failure mechanism. The relationship between these parameters and the failure mode is analyzed and the strain component associated with this, if it exists, is also determined. A theoretical analysis based on a plane strain finite element model and a quadratic failure criterion is presented. The failure mode, the point of failure and the failure load can be predicted by applying this model. Finally, a correlation between the test measurements and the theory results shows excellent agreement.

  8. Development of a Heterogeneous Laminating Resin

    NASA Technical Reports Server (NTRS)

    Gosnell, R.

    1984-01-01

    The feasibility of toughening the common types of matrix resins such as Narmco 5208 by utilizing a heterogeneous additive was examined. Some basic concepts and principles in the toughening of matrix resins for advanced composites were studied. The following conclusions were advanced: (1) the use of damage volume as a guide for measurement of impact resistance appears to be a valid determination; (2) short beam shear is a good test to determine the effect of toughening agents on mechanical properties; (3) rubber toughening results in improved laminate impact strength, but with substantial loss in high temperature dry and wet strength; (4) in the all-epoxy systems, the polycarbonate toughening agent seemed to be the most effective, although hot-wet strength is sacrificed; ABS was not as effective; and (5) in general, the toughened all-epoxy systems showed better damage tolerance, but less hot-wet strength; toughened bismaleimides had better hot-wet strength.

  9. Diversity dynamics of marine planktonic diatoms across the Cenozoic.

    PubMed

    Rabosky, Daniel L; Sorhannus, Ulf

    2009-01-01

    Diatoms are the dominant group of phytoplankton in the modern ocean. They account for approximately 40% of oceanic primary productivity and over 50% of organic carbon burial in marine sediments. Owing to their role as a biological carbon pump and effects on atmospheric CO(2) levels, there is great interest in elucidating factors that influenced the rapid rise in diatom diversity during the past 40 million years. Two biotic controls on diversification have been proposed to explain this diversity increase: (1) geochemical coupling between terrestrial grasslands and marine ecosystems through the global silicon cycle; and (2) competitive displacement of other phytoplankton lineages. However, these hypotheses have not been tested using sampling-standardized fossil data. Here we show that reconstructions of species diversity in marine phytoplankton reject these proposed controls and suggest a new pattern for oceanic diatom diversity across the Cenozoic. Peak species diversity in marine planktonic diatoms occurred at the Eocene-Oligocene boundary and was followed by a pronounced decline, from which diversity has not recovered. Although the roles of abiotic and biotic drivers of diversification remain unclear, major features of oceanic diatom evolution are decoupled from both grassland expansion and competition among phytoplankton groups. PMID:19129846

  10. Comparing optical properties of different species of diatoms

    NASA Astrophysics Data System (ADS)

    Maibohm, C.; Friis, S. M. M.; Su, Y.; Rottwitt, K.

    2015-03-01

    Diatoms are single cellular algae encapsulated in an external wall of micro-structured porous silica called the frustule. Diatoms are present in all water environments and contribute with 20-25 % of the global primary production of oxygen by photosynthesis. The appearance of the frustule is very species dependent with huge variety in size, shape, and microstructure. We have experimentally investigated optical properties of frustules of several species of diatoms to further understand light harvesting properties together with common traits, effects and differences between the different frustules. We have observed, when incident light interacts with the micro-structured frustule it is multiple diffracted giving rise to wavelength dependent multiple focal points and other optical effects. Experimental results have been simulated and well confirmed by free space FFT propagation routine analysis software. The software uses parameters which are extracted from experimental images 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.

  11. Historical processes constrain patterns in global diatom diversity.

    PubMed

    Vyverman, Wim; Verleyen, Elie; Sabbe, Koen; Vanhoutte, Koenraad; Sterken, Mieke; Hodgson, Dominic A; Mann, David G; Juggins, Steve; Van de Vijver, Bart; Jones, Vivienne; Flower, Roger; Roberts, Donna; Chepurnov, Victor A; Kilroy, Cathy; Vanormelingen, Pieter; De Wever, Aaike

    2007-08-01

    There is a long-standing belief that microbial organisms have unlimited dispersal capabilities, are therefore ubiquitous, and show weak or absent latitudinal diversity gradients. In contrast, using a global freshwater diatom data set, we show that latitudinal gradients in local and regional genus richness are present and highly asymmetric between both hemispheres. Patterns in regional richness are explained by the degree of isolation of lake districts, while the number of locally coexisting diatom genera is highly constrained by the size of the regional diatom pool, habitat availability, and the connectivity between habitats within lake districts. At regional to global scales, historical factors explain significantly more of the observed geographic patterns in genus richness than do contemporary environmental conditions. Together, these results stress the importance of dispersal and migration in structuring diatom communities at regional to global scales. Our results are consistent with predictions from the theory of island biogeography and metacommunity concepts and likely underlie the strong provinciality and endemism observed in the relatively isolated diatom floras in the Southern Hemisphere. PMID:17824422

  12. Grasslands, silicate weathering and diatoms: Cause and effect

    SciTech Connect

    Johansson, A.K. . Dept. of Geological Sciences)

    1993-03-01

    Diatoms are silica-limited, photosynthetic, single-celled eukaryotes that today occupy a wide variety of habitats both in freshwater and marine environments. Ultimately the silica they use is derived from the weathering of silicates on land. Although marine diatoms first appear in the Jurassic, the fossil record shows a remarkable correlation between the Mid-Miocene appearance of widespread grasslands and the drastic increase in diatom-rich deposits in freshwater, as well as in marine environments throughout the world. Grasses actively weather silicates, accumulating soluble silica into their leaves. Decomposing grasses release this soluble silica into the soil from whence it is transported into lakes and oceans and made available to diatoms. Grasses also probably increased chemical weathering, and hence the release of soluble silica, in previously weakly vegetated semi-arid areas. Increased weathering of silicates also led to cooler climates as evidenced by the Mid-Miocene [delta][sup 18]O record. The author suggests that the Tertiary expansion of grasslands is responsible for the explosive increase in diversity and abundance of diatoms in the oceans and freshwaters of the Mid-Miocene.

  13. Neogene diatom and silicoflagellate biostratigraphy of Naples Beach, California

    SciTech Connect

    Navarrette, R.J.; Marolt, R.E.; Finger, K.L.

    1986-04-01

    Diatoms and silicoflagellates recovered from Monterey Formation outcrops along Naples Beach, California, provide detailed biostratigraphy in the middle Miocene to upper Pliocene strata. Thirty-eight diatom and six silicoflagellate index species are identified among the 178 selected taxa documented in this section. Seven diatom zones and subzones of J. Barron's northeastern Pacific diatom zonation are recognized in this section. These zones range from the Denticulopsis lauta subzone a (+15.0 m.y.) to the base of the Thalasiosira oestrupii zone (approx. 5.0 m.y.). In addition, several diatom occurrences provide direction correlation between the Naples Beach section and DSDP Sites 173 and 469 off the northern and southern California coasts, respectively. A new silicoflagellate zonation is proposed for the Naples Beach section of the Monterey Formation, which consists of two range zones, the Corbisema triacantha and the Distephanus speculum minutus, and four subzones. These four subzones are characterized by Distephanus crux parvus, Mesocena diodon, Distephanus pseudofibula, and Distephanus frugalis, respectively. This zonation provides greater precision than previous biostratigraphic divisions of the DSDP sites. A new silicoflagellate species of the genus Dictyocha Ehrenberg is also described.

  14. Chitinase producing bacteria with direct algicidal activity on marine diatoms.

    PubMed

    Li, Yi; Lei, Xueqian; Zhu, Hong; Zhang, Huajun; Guan, Chengwei; Chen, Zhangran; Zheng, Wei; Fu, Lijun; Zheng, Tianling

    2016-01-01

    Chitinase producing bacteria can involve extensively in nutrient cycling and energy flow in the aquatic environment through degradation and utilization of chitin. It is well known that diatoms cells are encased by box-like frustules composed of chitin. Thus the chitin containing of diatoms shall be a natural target of chitinase producing bacteria, however, the interaction between these two organismic groups has not been studied thus far. Therefore, in this study, the algicidal mechanism of one chitinase producing bacterium (strain LY03) on Thalassiosira pseudonana was investigated. The algicidal range and algicidal mode of strain LY03 were first studied, and then bacterial viability, chemotactic ability and direct interaction characteristic between bacteria and diatom were also confirmed. Finally, the characteristic of the intracellular algicidal substance was identified and the algicidal mechanism was determined whereby algicidal bacterial cells showed chemotaxis to algal cells, fastened themselves on algal cells with their flagella, and then produced chitinase to degrade algal cell walls, and eventually caused algal lysis and death. It is the first time to investigate the interaction between chitinase producing bacteria and diatoms, and this novel special interaction mode was confirmed in this study, which will be helpful in protection and utilization of diatoms resources. PMID:26902175

  15. Gene silencing in the marine diatom Phaeodactylum tricornutum

    PubMed Central

    De Riso, Valentina; Raniello, Raffaella; Maumus, Florian; Rogato, Alessandra; Bowler, Chris; Falciatore, Angela

    2009-01-01

    Diatoms are a major but poorly understood phytoplankton group. The recent completion of two whole genome sequences has revealed that they contain unique combinations of genes, likely recruited during their history as secondary endosymbionts, as well as by horizontal gene transfer from bacteria. A major limitation for the study of diatom biology and gene function is the lack of tools to generate targeted gene knockout or knockdown mutants. In this work, we have assessed the possibility of triggering gene silencing in Phaeodactylum tricornutum using constructs containing either anti-sense or inverted repeat sequences of selected target genes. We report the successful silencing of a GUS reporter gene expressed in transgenic lines, as well as the knockdown of endogenous phytochrome (DPH1) and cryptochrome (CPF1) genes. To highlight the utility of the approach we also report the first phenotypic characterization of a diatom mutant (cpf1). Our data open the way for reverse genetics in diatoms and represent a major advance for understanding their biology and ecology. Initial molecular analyses reveal that targeted downregulation likely occurs through transcriptional and post-transcriptional gene silencing mechanisms. Interestingly, molecular players involved in RNA silencing in other eukaryotes are only poorly conserved in diatoms. PMID:19487243

  16. Size of Dominant Diatom Species Can Alter Their Evenness

    PubMed Central

    Sugie, Koji; Suzuki, Koji

    2015-01-01

    Traditionally, biodiversity has often been estimated on the basis of abundance partly due to the need for complicated measurements of biomass. Here, we conducted robust measurements of the community composition and of the size structure of diatoms in the North Pacific to evaluate the importance of biomass on the biodiversity. We found that the two most useful evenness indices increased in most cases where small species were numerically dominant when calculations were based on biomass compared with those on abundance. Size-abundance spectra of diatoms revealed that numerically dominant small species rarely dominated in terms of biomass. On the other hand, intermediate to large diatom species generally played a dominant role in terms of biomass in diatom community. The results suggest that the size of the dominant species is a crucial factor in determining the role of diatoms in the ecosystem functioning. Because such size variability can also be observed in other organisms, we need to pay attention to the effect of size structures on biodiversity. PMID:26098838

  17. Chitinase producing bacteria with direct algicidal activity on marine diatoms

    PubMed Central

    Li, Yi; Lei, Xueqian; Zhu, Hong; Zhang, Huajun; Guan, Chengwei; Chen, Zhangran; Zheng, Wei; Fu, Lijun; Zheng, Tianling

    2016-01-01

    Chitinase producing bacteria can involve extensively in nutrient cycling and energy flow in the aquatic environment through degradation and utilization of chitin. It is well known that diatoms cells are encased by box-like frustules composed of chitin. Thus the chitin containing of diatoms shall be a natural target of chitinase producing bacteria, however, the interaction between these two organismic groups has not been studied thus far. Therefore, in this study, the algicidal mechanism of one chitinase producing bacterium (strain LY03) on Thalassiosira pseudonana was investigated. The algicidal range and algicidal mode of strain LY03 were first studied, and then bacterial viability, chemotactic ability and direct interaction characteristic between bacteria and diatom were also confirmed. Finally, the characteristic of the intracellular algicidal substance was identified and the algicidal mechanism was determined whereby algicidal bacterial cells showed chemotaxis to algal cells, fastened themselves on algal cells with their flagella, and then produced chitinase to degrade algal cell walls, and eventually caused algal lysis and death. It is the first time to investigate the interaction between chitinase producing bacteria and diatoms, and this novel special interaction mode was confirmed in this study, which will be helpful in protection and utilization of diatoms resources. PMID:26902175

  18. Interlaminar stresses in composite laminates: A perturbation analysis

    NASA Technical Reports Server (NTRS)

    Hsu, P. W.; Herakovich, C. T.

    1976-01-01

    A general method of solution for an elastic balanced symmetric composite laminate subject to a uniaxial extension was developed based upon a perturbation analysis of a limiting free body containing an interfacial plane. The solution satisfies more physical requirements and boundary conditions than previous investigations, and predicts smooth continuous interlaminar stresses with no instabilities. It determines the finite maximum intensity for the interlaminar normal stress in all laminates, provides mathematical evidences for the singular stresses in angle-ply laminates, suggests the need for the experimental determination of an important problem parameter, and introduces a viable means for solving related problems of practical interest.

  19. Prediction of microcracking in composite laminates under thermomechanical loading

    NASA Technical Reports Server (NTRS)

    Maddocks, Jason R.; Mcmanus, Hugh L.

    1995-01-01

    Composite laminates used in space structures are exposed to both thermal and mechanical loads. Cracks in the matrix form, changing the laminate thermoelastic properties. An analytical methodology is developed to predict microcrack density in a general laminate exposed to an arbitrary thermomechanical load history. The analysis uses a shear lag stress solution in conjunction with an energy-based cracking criterion. Experimental investigation was used to verify the analysis. Correlation between analysis and experiment is generally excellent. The analysis does not capture machining-induced cracking, or observed delayed crack initiation in a few ply groups, but these errors do not prevent the model from being a useful preliminary design tool.

  20. Multi-Layer Laminated Thin Films for Inflatable Structures

    NASA Technical Reports Server (NTRS)

    Yavrouian, Andre; Plett, Gary; Mannella, Jerami

    2005-01-01

    Special-purpose balloons and other inflatable structures would be constructed as flexible laminates of multiple thin polymeric films interspersed with layers of adhesive, according to a proposal. In the original intended application, the laminate would serve as the envelope of the Titan Aerobot a proposed robotic airship for exploring Titan (one of the moons of Saturn). Potential terrestrial applications for such flexible laminates could include blimps and sails. In the original application, the multi-layered laminate would contain six layers of 0.14-mil (0.0036-mm)-thick Mylar (or equivalent) polyethylene terephthalate film with a layer of adhesive between each layer of Mylar . The overall thickness and areal density of this laminate would be nearly the same as those of 1-mil (0.0254-mm)-thick monolayer polyethylene terephthalate sheet. However, the laminate would offer several advantages over the monolayer sheet, especially with respect to interrelated considerations of flexing properties, formation of pinholes, and difficulty or ease of handling, as discussed next. Most of the damage during flexing of the laminate would be localized in the outermost layers, where the radii of bending in a given bend would be the largest and, hence, the bending stress would be the greatest. The adverse effects of formation of pinholes would be nearly completely mitigated in the laminate because a pinhole in a given layer would not propagate to adjacent layers. Hence, the laminate would tend to remain effective as a barrier to retain gas. Similar arguments can be made regarding cracks: While a crack could form as a result of stress or a defect in the film material, a crack would not propagate into adjacent layers, and the adjacent layer(s) would even arrest propagation of the crack. In the case of the monolayer sheet, surface damage (scratches, dents, permanent folds, pinholes, and the like) caused by handling would constitute or give rise to defects that could propagate through the thickness as cracks or pinholes that would render the sheet less effective or ineffective as a barrier. In contrast, because damage incurred during handling of the laminate would ordinarily be limited to the outermost layers, the barrier properties of the laminate would be less likely to be adversely affected. Therefore, handling of the laminate would be easier because there would be less of a need to exercise care to ensure against surface damage.

  1. Nonlinear finite element models of laminated plates and shells

    NASA Technical Reports Server (NTRS)

    Redddy, J. N.; Chandrashekhara, K.

    1985-01-01

    In this expository paper a first-order shear deformation laminate theory that accounts for the von Karman strains is described and its finite element model is developed. The element also accounts for Hill's elastic-perfectly plastic material model. Sample applications of the present element to linear and nonlinear bending of laminated plates and shells are presented. Numerical results showing the effects of boundary conditions, lamination scheme, and loading on the deflections and stresses are also presented. It is found that the effect of shear deformation and boundary conditions on deflections are significant.

  2. Analysis of a hybrid, unidirectional buffer strip laminate

    NASA Technical Reports Server (NTRS)

    Dharani, L. R.; Goree, J. G.

    1983-01-01

    A method of analysis capable of predicting accurately the fracture behavior of a unidirectional composite laminate containing symmetrically placed buffer strips is presented. As an example, for a damaged graphite/epoxy laminate, the results demonstrate the manner in which to select the most efficient combination of buffer strip properties necessary to inhibit crack growth. Ultimate failure of the laminate after crack arrest can occur under increasing load either by continued crack extension through the buffer strips or the crack can jump the buffer strips. For some typical hybrid materials it is found that a buffer strip spacing-to-width ratio of about four to one is the most efficient.

  3. Analysis of a hybrid-undirectional buffer strip laminate

    NASA Technical Reports Server (NTRS)

    Dharani, L. R.; Goree, J. G.

    1983-01-01

    A method of analysis capable of predicting accurately the fracture behavior of a unidirectional composite laminate containing symmetrically placed buffer strips is presented. As an example, for a damaged graphite/epoxy laminate, the results demonstrate the manner in which to select the most efficient combination of buffer strip properties necessary to inhibit crack growth. Ultimate failure of the laminate after the arrest can occur under increasing load either by continued crack extension through the buffer strips or the crack can jump the buffer strips. For some typical hybrid materials it is found that a buffer strip spacing to width ratio of about four to one is the most efficient.

  4. Laminated metals composites fracture and ballistic impact behavior

    SciTech Connect

    Lesuer, D.R.; Syn, C.K.; Sherby, O.D.; Wadsworth, J.

    1998-01-20

    Recent advances in the fracture and ballistic impact response of laminated metal composites (LMCs) are reviewed. The laminate structure can provide significant improvements to these properties relative to the component materials. Typical fracture and ballistic impact properties in LMCs are illustrated for systems containing Al alloys and Al matrix composites. The unique mechanisms operating in a layered structure that contribute to fracture or ballistic impact resistance are discussed. The influence of laminate architecture, component material properties and interface strength on mechanisms and properties are briefly reviewed for these Al-based LMCs.

  5. Axisymmetric vibrations of laminated composite conical shells with varying thickness

    SciTech Connect

    Shikanai, G.; Suzuki, K.; Kojima, M.

    1995-11-01

    An exact solution procedure is presented for solving axisymmetric free vibrations of laminated composite conical shells with varying thickness. Based on the classical lamination theory neglecting shear deformation and rotary inertia, equations of motion and boundary conditions are obtained from the stationary conditions of the Lagrangian. The equations of motion are solved exactly by using a power series expansion for symmetrically laminated, cross-ply conical shells. Numerical studies are made for conical shells having both ends clamped to show the effects of the number of laminae, stacking sequences and other parameters upon the frequencies.

  6. Vibration analysis of rotating thin laminated composite shell of revolution

    SciTech Connect

    Suzuki, K.; Shikanai, G.; Takayama, K.

    1995-11-01

    An exact solution procedure is presented for solving free vibrations of a rotating thin laminated composite shell of revolution having meridionally constant curvature. Based on the classical lamination theory, equations of motion and boundary conditions are obtained from the stationally conditions of the Lagrangian. The equations of motion are solved exactly by using a power series expansion for symmetrically laminated, cross-ply shells. Frequencies and mode shapes of the shells having both ends clamped and both ends freely supported are presented showing their variations with rotating angular velocity, number of laminae and other parameters.

  7. Accurate stress resultants equations for laminated composite deep thick shells

    SciTech Connect

    Qatu, M.S.

    1995-11-01

    This paper derives accurate equations for the normal and shear force as well as bending and twisting moment resultants for laminated composite deep, thick shells. The stress resultant equations for laminated composite thick shells are shown to be different from those of plates. This is due to the fact the stresses over the thickness of the shell have to be integrated on a trapezoidal-like shell element to obtain the stress resultants. Numerical results are obtained and showed that accurate stress resultants are needed for laminated composite deep thick shells, especially if the curvature is not spherical.

  8. Wave propagation in graphite/epoxy laminates due to impact

    NASA Technical Reports Server (NTRS)

    Tan, T. M.; Sun, C. T.

    1982-01-01

    The low velocity impact response of graphite-epoxy laminates is investigated theoretically and experimentally. A nine-node isoparametric finite element in conjunction with an empirical contact law was used for the theoretical investigation. Flat laminates subjected to pendulum impact were used for the experimental investigation. Theoretical results are in good agreement with strain gage experimental data. The collective results of the investigation indicate that the theoretical procedure describes the impact response of the laminate up to about 150 in/sec. impact velocity.

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

    PubMed

    Bere, T; Tundisi, J G

    2010-11-01

    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. PMID:21180895

  10. Development of diatom indicators of ecological conditions for streams of the western US

    EPA Science Inventory

    The species composition of benthic diatoms was related to environmental conditions in streams throughout the western US to develop diatom traits, indicators for assessment of biological condition and indicators for diagnosing stressors. We hypothesized that indicators based on sp...

  11. Bound-free Spectra for Diatomic Molecules

    NASA Technical Reports Server (NTRS)

    Schwenke, David W.

    2012-01-01

    It is now recognized that prediction of radiative heating of entering space craft requires explicit treatment of the radiation field from the infrared (IR) to the vacuum ultra violet (VUV). While at low temperatures and longer wavelengths, molecular radiation is well described by bound-bound transitions, in the short wavelength, high temperature regime, bound-free transitions can play an important role. In this work we describe first principles calculations we have carried out for bound-bound and bound-free transitions in N2, O2, C2, CO, CN, NO, and N2+. Compared to bound ]bound transitions, bound-free transitions have several particularities that make them different to deal with. These include more complicated line shapes and a dependence of emission intensity on both bound state diatomic and atomic concentrations. These will be discussed in detail below. The general procedure we used was the same for all species. The first step is to generate potential energy curves, transition moments, and coupling matrix elements by carrying out ab initio electronic structure calculations. These calculations are expensive, and thus approximations need to be made in order to make the calculations tractable. The only practical method we have to carry out these calculations is the internally contracted multi-reference configuration interaction (icMRCI) method as implemented in the program suite Molpro. This is a widely used method for these kinds of calculations, and is capable of generating very accurate results. With this method, we must first of choose which electrons to correlate, the one-electron basis to use, and then how to generate the molecular orbitals.

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

    NASA Astrophysics Data System (ADS)

    Parigger, Christian G.; Woods, Alexander C.; Surmick, David M.; Gautam, Ghaneshwar; Witte, Michael J.; Hornkohl, James O.

    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 (C2), 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, C2, CN, and TiO diatomic spectra.

  13. Lensless light focusing with the centric marine diatom Coscinodiscus walesii.

    PubMed

    De Stefano, Luca; Rea, Ilaria; Rendina, Ivo; De Stefano, Mario; Moretti, Luigi

    2007-12-24

    In this work, we report on the light focusing ability exploited by the microshell of a marine organism: the Coscinodiscus wailesii diatom. A 100 microm spot size of a red laser beam is narrowed up to less than 10 microm at a distance of 104 microm after the transmission through the regular geometry of the diatom structure, which thus acts as a microlens. Numerical simulations of the electromagnetic field propagation show a good qualitative agreement with the experimental results. The focusing effect is due to the superposition of the waves scattered by the holes present on the surface of the diatom valve. Very interesting applications in micro-optic devices are feasible due to the morphological and biological characteristic of these unicellular organisms. PMID:19551106

  14. Ultrastructural observations on the marine fouling diatom Amphora

    NASA Astrophysics Data System (ADS)

    Daniel, G. F.; Chamberlain, A. H. L.; Jones, E. B. G.

    1980-06-01

    Ecological and Scanning electron microscope (S. E. M.) studies indicated that the diatom Amphora was an important constituent in the initial colonization of test panels coated with a copper antifouling composition. Amphora was also found as the dominant fouling diatom species on paint samples from in-service supertankers and yachts. Associated with the diatom was copious amounts of mucilaginous material, which often encapsulated the cells. Histochemical analysis of the mucilage indicates that it is predominantly polysaccharide in nature. Using the Transmission electron microscope (T. E. M.) and electron microscope cytochemistry the intracellular origin of the adhesive was investigated. T. E. M. and S. E. M. observations of acid-cleaned-cells indicate that the mucilage may be secreted through specialized regions of the frustule. Material isolated from antifouling panels was compared with laboratory cultured Amphora spp. for copper resistance and internal accumulation using TEMSCAN X ray analytical equipment.

  15. Diatoms: a biotemplating approach to fabricating drug delivery reservoirs.

    PubMed

    Chao, Joshua T; Biggs, Manus J P; Pandit, Abhay S

    2014-11-01

    Biotemplating is a rapidly expanding subfield that utilizes nature-inspired systems and structures to create novel functional materials, and it is through these methods that the limitations of current engineering practices may be advanced. The diatom is an exceptional template for drug delivery applications, owing largely to its highly-ordered pores, large surface area, species-specific architecture, and flexibility for surface modifications. Diatoms have been studied in a wide range of biomedical applications and their potential as the next frontier of drug delivery has yet to be fully exploited. In this editorial, the authors aim to review the use of diatoms in the delivery of poorly water-soluble drugs as reported in the literature, discuss the progress and advancements that have been made thus far, identify the shortcomings and limitations in the field, and, lastly, present their expert opinion and convey the future outlook on biotemplating approaches for drug delivery. PMID:25146231

  16. Microfluidic detachment assay to probe the adhesion strength of diatoms.

    PubMed

    Alles, M; Rosenhahn, A

    2015-01-01

    Fouling release (FR) coatings are increasingly applied as an environmentally benign alternative for controlling marine biofouling. As the technology relies on removing fouling by water currents created by the motion of ships, weakening of adhesion of adherent organisms is the key design goal for improved coatings. In this paper, a microfluidic shear force assay is used to quantify how easily diatoms can be removed from surfaces. The experimental setup and the optimization of the experimental parameters to study the adhesion of the diatom Navicula perminuta are described. As examples of how varying the physico-chemical surface properties affects the ability of diatoms to bind to surfaces, a range of hydrophilic and hydrophobic self-assembled monolayers was compared. While the number of cells that attached (adhered) was barely affected by the coatings, the critical shear stress required for their removal from the surface varied significantly. PMID:26168802

  17. The coupled states approximation for scattering of two diatoms

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    The paper presents a detailed development of the coupled-states approximation for the general case of two colliding diatomic molecules. The high-energy limit of the exact Lippman-Schwinger equation is applied, and the analysis follows the Shimoni and Kouri (1977) treatment of atom-diatom collisions where the coupled rotor angular momentum and projection replace the single diatom angular momentum and projection. Parallels to the expression for the differential scattering amplitude, the opacity function, and the nondiagonality of the T matrix are reported. Symmetrized expressions and symmetrized coupled equations are derived. The present correctly labeled coupled-states theory is tested by comparing its calculated results with other computed results for three cases: H2-H2 collisions, ortho-para H2-H2 scattering, and H2-HCl.

  18. Long-term decomposition of DOC from experimental diatom blooms

    SciTech Connect

    Fry, B.; Hopkinson, C.S. Jr.; Nolin, A.

    1996-09-01

    Decomposition of {sup 13}C-labeled dissolved organic carbon (DOC) produced in two marine diatom blooms was followed for 2.5 yr with large volume (20 liter) incubations performed in the dark. The {sup 13}C tracer was used to partition decomposition dynamics of the fresh diatom-derived DOC and the turnover of background DOC from Woods Hole Harbor. DOC from Woods Hole harbor proved largely refractory, with DOC concentrations falling from 122 to {approximately} 100 {mu}M C in 2.5 yr. DOC from the diatom blooms was more labile, but was also incompletely mineralized, with 25-35% remaining after 2.5 yr. Neither nutrients nor labile carbon (dextrose) added at 1.5 yr significantly stimulated DOC mineralization. The experiments indicate that DOC produced in short-term blooms can be surprisingly resistant to microbial attack. 21 refs., 1 fig., 1 tab.

  19. Diatom response to extremely low-frequency magnetic fields

    SciTech Connect

    Parkinson, W.C.; Sulik, G.L. )

    1992-06-01

    Reports that extremely low-frequency magnetic fields can interfere with normal biological cell function continue to stimulate experimental activity as well as investigations into the possible mechanism of the interaction. The cyclotron resonance' model of Liboff has been tested by Smith et al. using as the biological test system the diatom Amphora coffeiformis. They report enhanced motility of the diatom in response to a low-frequency electromagnetic field tuned to the cyclotron resonance condition for calcium ions. We report here an attempt to reproduce their results. Following their protocol diatoms were seeded onto agar plates containing varying amounts of calcium and exposed to colinear DC and AC magnetic fields tuned to the cyclotron resonant condition for frequencies of 16, 30, and 60 Hz. The fractional motility was compared with that of control plates seeded at the same time from the same culture. We find no evidence of a cyclotron resonance effect.

  20. Circular random motion in diatom gliding under isotropic conditions.

    PubMed

    Gutiérrez-Medina, Braulio; Guerra, Andrés Jiménez; Maldonado, Ana Iris Peña; 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. PMID:25393453

  1. Circular random motion in diatom gliding under isotropic conditions

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  2. A Guide to the Common Diatoms at Water Pollution Surveillance System Stations.

    ERIC Educational Resources Information Center

    Weber, Cornelius I.

    This guide was developed by the United States Environmental Protection Agency (EPA) as a taxonomic reference for the identification of diatoms. The taxonomic information included consists of a generic key to the common genera of diatoms, a section illustrating 164 diatom species representing 43 common genera found at the Water Pollution

  3. The relationship between light intensity and nutrient uptake kinetics in six freshwater diatoms.

    PubMed

    Shi, Pengling; Shen, Hong; Wang, Wenjing; Chen, Wenjie; Xie, Ping

    2015-08-01

    In order to find effective measures to control diatom blooms, a better understanding of the physiological characteristics of nutrient uptake in diatoms is needed. A study of P and Si-uptake kinetics for diatom species from two light regimes was conducted at low (LL), moderate (ML) and high light intensities (HL) (2, 25 and 80?mol photons/(m(2)sec)), respectively. The results showed that P uptake of diatoms was heavily influenced by historic light regimes. P affinity changed with growth and photosynthetic activity. The lowest half saturation constant for P uptake (Km(P)) was under HL for high-light adapted diatoms while the lowest half-saturation constant for low-light adapted diatoms was observed under LL. The Si half-saturation constant (Km(Si)) increased with increasing light intensities for pennate diatoms but decreased for centric diatoms. Diatom volumes were correlated with the maximum Si uptake rates (Vm(Si)) at HL and Km(Si) at ML and HL for six diatom species. Our results imply that when we assess the development of diatom blooms we should consider light intensity and cell volume in addition to ambient Si or P concentration. The relationship between light intensity and P-uptake suggests that we can find suitable methods to control diatom blooms on the basis of reducing phytoplankton activity of P-uptake and photosynthesis simultaneously. PMID:26257343

  4. Iron Oxide Nanoparticle Encapsulated Diatoms for Magnetic Delivery of Small Molecules to Tumors

    PubMed Central

    Todd, Trever; Zhen, Zipeng; Tang, Wei; Chen, Hongmin; Wang, Geoffrey; Chuang, Yen-Jun; Deaton, Kayley; Pan, Zhengwei; Xie, Jin

    2014-01-01

    Small molecules can be co-loaded with iron oxide nanoparticles onto diatoms. With an external magnetic field, the diatoms, after systemic administration, can be attracted to tumors. This study suggests a great potential of diatoms as a novel and powerful therapeutic vehicle. PMID:24424277

  5. Iron oxide nanoparticle encapsulated diatoms for magnetic delivery of small molecules to tumors.

    PubMed

    Todd, Trever; Zhen, Zipeng; Tang, Wei; Chen, Hongmin; Wang, Geoffrey; Chuang, Yen-Jun; Deaton, Kayley; Pan, Zhengwei; Xie, Jin

    2014-02-21

    Small molecules can be co-loaded with iron oxide nanoparticles onto diatoms. With an external magnetic field, the diatoms, after systemic administration, can be attracted to tumors. This study suggests a great potential of diatoms as a novel and powerful therapeutic vehicle. PMID:24424277

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

    NASA Astrophysics Data System (ADS)

    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 (<20 μm in length) accounted for a considerable proportion of the total species number and cell density of the diatom assemblages in the gut contents and on the films. This suggests that nano-diatoms are important to the efficient production of 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.

  7. Freshwater diatoms as environmental indicators: evaluating the effects of eutrophication using species morphology and biological indices.

    PubMed

    Vilmi, Annika; Karjalainen, Satu Maaria; Landeiro, Victor L; Heino, Jani

    2015-05-01

    Anthropogenic eutrophication is a major form of perturbation in freshwaters, and several approaches aim to recognise its effects on lake ecosystems. We compared the responses of diatom species morphology, diversity indices and diatom indices to total phosphorus, total nitrogen and distance from a point stressor causing eutrophication in a large lake. We specifically examined the degree to which extent nutrients and distance to the stressor affect variation in the values of various biological indices and diatom valve size. In addition, special attention was given to the adequate repetition of diatom valve width measurements in the context of environmental assessment. Our results showed that diatom valve width was a better indicator of nutrient concentrations than any of the diatom and diversity indices examined. However, the results varied between the two study transects, suggesting that the diatom-based variables not only respond to nutrients but also to other environmental factors (e.g. shoreline morphology). We also found that when using the method based on diatom morphology, one should measure more valves than has been originally suggested to provide a more reliable picture of response to eutrophication. We argue that diatom morphology could be considered as an additional environmental assessment tool, because it may complement the information provided by the traditional diatom indices. Diatom valve width may also be more sensitive to early phases of the eutrophication process and its effects on freshwater ecosystems than various diatom indices that were developed in regional contexts with wide ranges in nutrient levels. PMID:25864081

  8. USING DIATOMS AS INDICATORS OF ECOLOGICAL CONDITIONS IN LOTIC SYSTEMS: A REGIONAL ASSESSMENT

    EPA Science Inventory

    Benthic diatoms and water chemistry were sampled from 49 stream sites in the Mid-Atlantic Highlands region of the United States to evaluate the use of diatoms as indicators of environmental conditions in streams across varying geographic and ecoregional areas. Diatom samples were...

  9. A Guide to the Common Diatoms at Water Pollution Surveillance System Stations.

    ERIC Educational Resources Information Center

    Weber, Cornelius I.

    This guide was developed by the United States Environmental Protection Agency (EPA) as a taxonomic reference for the identification of diatoms. The taxonomic information included consists of a generic key to the common genera of diatoms, a section illustrating 164 diatom species representing 43 common genera found at the Water Pollution…

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

    PubMed

    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 <0.025μm filtered, <0.45μm filtered (dissolved) and unfiltered (total) present in solution over the 72-h bioassay. The chronic population growth rate inhibition after 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 (p<0.05) increasing with initial cell density from 10(3) to 10(5)cells/mL. No effects on plasma membrane permeability were observed for any of the three diatoms suggesting that mechanisms of aluminium 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. PMID:26921729

  11. Role of diatoms in nickel biogeochemistry in the ocean

    NASA Astrophysics Data System (ADS)

    Twining, Benjamin S.; Baines, Stephen B.; Vogt, Stefan; Nelson, David M.

    2012-12-01

    Dissolved nickel (Ni) typically displays a `nutrient-like' vertical profile in the ocean, with lower concentrations in surface waters and higher concentrations in deep waters, similar to other micronutrient metals such as iron and zinc. Vertical profiles of Ni show particular similarities to profiles of the macronutrients phosphate and silicic acid, suggesting that diatoms play an important role in mediating the vertical distribution of this metal. We performed synchrotron x-ray fluorescence (SXRF) analysis on individual phytoplankton cells collected from stations in the equatorial Pacific Ocean and from nutrient-addition incubation experiments conducted on the same cruise. Diatoms were enriched in Ni twofold to fivefold relative to picoplankton and flagellated cells. Changes in cellular quotas of Si, P and Ni observed in diatoms growing in response to Fe and Si additions were used to estimate the Ni:P (0.52 0.10 mmol/mol) and Ni:Si (28 13 ?mol/mol) ratios of internal biomass and the frustule, respectively. Elevated internal Ni:P suggests a heightened role for urease or the Ni isoform of superoxide dismutase in diatoms (similar to cyanobacteria), while Ni associated with the frustule appears to contribute an additional 50% of cellular Ni found in the diatoms. The derived Ni:Si ratio for frustule material is comparable to Ni:Si ratios in published nutrient profiles, confirming the dominant role that diatoms play in ocean Ni biogeochemistry. While a molecular explanation for the association of Ni with frustules remains to be determined, this study demonstrates the unique biogeochemical insight that can be gained from microanalytical element analysis.

  12. Diatom data from Bradley Lake, Oregon: downcore analyses

    USGS Publications Warehouse

    Hemphill-Haley, Eileen; Lewis, Roger C.

    2003-01-01

    Displaced marine diatoms provide biostratigraphic evidence for tsunami inundation at Bradley Lake, a small freshwater lake on the south-central Oregon coast. During the past 7,200 years, fine-grained lacustrine deposits in the deep axis of the lake were disturbed 17 times by the erosion and emplacement of coarse-grained gyttja and, in some cases, sand. By identifying diatoms in closely spaced core samples, we determined that 13 of the 17 events (termed idisturbance eventsi) record prehistoric tsunamis in Bradley Lake. We consider the evidence strong for 11 events, based on numbers and diversity of marine taxa: De1, De2, De4, De5, De6, De7, De8, De11, De12, De13, and De17. The evidence is less compelling for an additional 2 events (De9 and De10), although tsunami inundation is likely. Finally, we identified 4 events (De3, De14, De15 and De16) in which there were no marine diatoms to support tsunami inundation, although stratigraphic data shows that the lake bottom was disturbed. Freshwater diatoms dominate throughout the Bradley Lake record, showing that the lake has remained a freshwater habitat throughout its existence. However, anomalous occurrences of three species of brackish diatoms (Thalassiosira bramaputrae, Cyclotella meneghiniana, and Mastogloia smithii) may be evidence for short-lived periods of slightly elevated salinities in the lake following De16, De13, De12, De11, De9, De8, and De5. With the exception of De12, increased abundances of one or more of the brackish species is coincident with decreased numbers of freshwater diatoms. A temporary rise in salinity, as evidenced by short-lived increases in abundances of brackish species and decreases in abundances of freshwater species, is consistent with tsunami inundation into the lake.

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

    USGS Publications Warehouse

    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.

  14. Comparative Genomics of the Pennate Diatom Phaeodactylum tricornutum1[w

    PubMed Central

    Montsant, Anton; Jabbari, Kamel; Maheswari, Uma; Bowler, Chris

    2005-01-01

    Diatoms are one of the most important constituents of phytoplankton communities in aquatic environments, but in spite of this, only recently have large-scale diatom-sequencing projects been undertaken. With the genome of the centric species Thalassiosira pseudonana available since mid-2004, accumulating sequence information for a pennate model species appears a natural subsequent aim. We have generated over 12,000 expressed sequence tags (ESTs) from the pennate diatom Phaeodactylum tricornutum, and upon assembly into a nonredundant set, 5,108 sequences were obtained. Significant similarity (E < 1E-04) to entries in the GenBank nonredundant protein database, the COG profile database, and the Pfam protein domains database were detected, respectively, in 45.0%, 21.5%, and 37.1% of the nonredundant collection of sequences. This information was employed to functionally annotate the P. tricornutum nonredundant set and to create an internet-accessible queryable diatom EST database. The nonredundant collection was then compared to the putative complete proteomes of the green alga Chlamydomonas reinhardtii, the red alga Cyanidioschyzon merolae, and the centric diatom T. pseudonana. A number of intriguing differences were identified between the pennate and the centric diatoms concerning activities of relevance for general cell metabolism, e.g. genes involved in carbon-concentrating mechanisms, cytosolic acetyl-Coenzyme A production, and fructose-1,6-bisphosphate metabolism. Finally, codon usage and utilization of C and G relative to gene expression (as measured by EST redundance) were studied, and preferences for utilization of C and CpG doublets were noted among the P. tricornutum EST coding sequences. PMID:15665249

  15. 10. Detail view of pendant lamps, laminated arch beams and ...

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

    10. Detail view of pendant lamps, laminated arch beams and ceiling structure, facing north - Mountain Home Air Force Base, Base Chapel, 350 Willow Street, Cantonment Area, Mountain Home, Elmore County, ID

  16. Modelling of thick composites using a layerwise laminate theory

    NASA Technical Reports Server (NTRS)

    Robbins, D. H., Jr.; Reddy, J. N.

    1993-01-01

    The layerwise laminate theory of Reddy (1987) is used to develop a layerwise, two-dimensional, displacement-based, finite element model of laminated composite plates that assumes a piecewise continuous distribution of the tranverse strains through the laminate thickness. The resulting layerwise finite element model is capable of computing interlaminar stresses and other localized effects with the same level of accuracy as a conventional 3D finite element model. Although the total number of degrees of freedom are comparable in both models, the layerwise model maintains a 2D-type data structure that provides several advantages over a conventional 3D finite element model, e.g. simplified input data, ease of mesh alteration, and faster element stiffness matrix formulation. Two sample problems are provided to illustrate the accuracy of the present model in computing interlaminar stresses for laminates in bending and extension.

  17. Current concepts on the pathophysiology of pasture-associated laminitis.

    PubMed

    Geor, Raymond J

    2010-08-01

    Epidemiologic studies indicate that most laminitis cases occur in horses and ponies kept at pasture, hence the term 'pasture-associated laminitis'. Clinical cases of laminitis most often occur under conditions that favor accumulation of rapidly fermentable nonstructural carbohydrates (fructans, simple sugars, or starches) in pasture, and animals with an equine metabolic syndrome (EMS) phenotype (insulin resistance, abnormal insulin dynamics, +/- obesity) seem to be at highest risk for developing the condition. Although the mechanisms linking consumption of pasture forage with development of lamellar failure have not been fully elucidated, a systemic inflammatory response that accompanies hindgut carbohydrate overload likely initiates lamellar inflammatory events (including infiltration and activation of leukocytes) that contribute to destruction of lamellar epithelium and extracellular matrix. This article reviews current knowledge on the epidemiology and risk factors for pasture-associated laminitis, including the role of forage carbohydrates and metabolic/endocrine predispositions, and also discusses the pathophysiology of this condition. PMID:20699174

  18. Structural and Dielectric Properties of Subnanometric Laminates of Binary Oxides.

    PubMed

    Kahouli, Abdelkader; Lebedev, Oleg; Ben Elbahri, Marwa; Mercey, Bernard; Prellier, Wilfrid; Riedel, Stefan; Czernohorsky, Malte; Lallemand, Florent; Bunel, Catherine; Lüders, Ulrike

    2015-11-25

    Capacitors with a dielectric material consisting of amorphous laminates of Al2O3 and TiO2 with subnanometer individual layer thicknesses can show strongly enhanced capacitance densities compared to the bulk or laminates with nanometer layer thickness. In this study, the structural and dielectric properties of such subnanometer laminates grown on silicon by state-of-the-art atomic layer deposition are investigated with varying electrode materials. The laminates show a dielectric constant reaching 95 combined with a dielectric loss (tan δ) of about 0.2. The differences of the observed dielectric properties in capacitors with varying electrodes indicate that chemical effects at the interface with the TiN electrode play a major role, while the influence of the local roughness of the individual layers is rather limited. PMID:26523935

  19. Fatigue of notched fiber composite laminates. Part 1: Analytical model

    NASA Technical Reports Server (NTRS)

    Mclaughlin, P. V., Jr.; Kulkarni, S. V.; Huang, S. N.; Rosen, B. W.

    1975-01-01

    A description is given of a semi-empirical, deterministic analysis for prediction and correlation of fatigue crack growth, residual strength, and fatigue lifetime for fiber composite laminates containing notches (holes). The failure model used for the analysis is based upon composite heterogeneous behavior and experimentally observed failure modes under both static and fatigue loading. The analysis is consistent with the wearout philosophy. Axial cracking and transverse cracking failure modes are treated together in the analysis. Cracking off-axis is handled by making a modification to the axial cracking analysis. The analysis predicts notched laminate failure from unidirectional material fatique properties using constant strain laminate analysis techniques. For multidirectional laminates, it is necessary to know lamina fatique behavior under axial normal stress, transverse normal stress and axial shear stress. Examples of the analysis method are given.

  20. Calculation of the room-temperature shapes of unsymmetric laminates

    NASA Technical Reports Server (NTRS)

    Hyer, M. W.

    1981-01-01

    A theory explaining the characteristics of the cured shapes of unsymmetric laminates is presented. The theory is based on an extension of classical lamination theory which accounts for geometric nonlinearities. A Rayleigh-Ritz approach to minimizing the total potential energy is used to obtain quantitative information regarding the room temperature shapes of square T300/5208 (0(2)/90(2))T and (0(4)/90(4))T graphite-epoxy laminates. It is shown that, depending on the thickness of the laminate and the length of the side the square, the saddle shape configuration is actually unstable. For values of length and thickness that render the saddle shape unstable, it is shown that two stable cylindrical shapes exist. The predictions of the theory are compared with existing experimental data.

  1. Thermomechanical stress analysis of laminated thick-film multilayer substrates

    NASA Astrophysics Data System (ADS)

    Kim, Jin S.; Paik, Kyung W.; Lim, Ji H.; Earmme, Youn Y.

    1999-06-01

    As an increasing number of polymer dielectric layers were laminated, the maximum bow values were measured layer by layer using a laser profilometry during thermal cycling. In the lamination process, a polymeric film is overlaid on a silicon substrate using a polymeric adhesive. Since the lamination process uses relatively thick polymer films, the classical stress analyses assuming infinitesimally thin films, are no longer effective. In this letter, a simple model based on the composite beam theory is presented to analyze the experimental results, and compared with the well-known Stoney's formula. The thermomechanical behavior of the laminated multilayer polymer films on a silicon substrate was better described by the proposed model, while an error as much as 30% was involved using Stoney's formula. The model can be applied for the design and fabrication of multilayer multichip module substrates.

  2. Laminated rare earth structure and method of making

    DOEpatents

    Senor, David J [West Richland, WA; Johnson, Roger N [Richland, WA; Reid, Bruce D [Pasco, WA; Larson, Sandra [Richland, WA

    2002-07-30

    A laminated structure having two or more layers, wherein at least one layer is a metal substrate and at least one other layer is a coating comprising at least one rare earth element. For structures having more than two layers, the coating and metal substrate layers alternate. In one embodiment of the invention, the structure is a two-layer laminate having a rare earth coating electrospark deposited onto a metal substrate. In another embodiment of the invention, the structure is a three-layer laminate having the rare earth coating electrospark deposited onto a first metal substrate and the coating subsequently abonded to a second metal substrate. The bonding of the coating to the second metal substrate may be accomplished by hot pressing, hot rolling, high deformation rate processing, or combinations thereof. The laminated structure may be used in nuclear components where reactivity control or neutron absorption is desired and in non-nuclear applications such as magnetic and superconducting films.

  3. Progressive Failure Analysis Methodology for Laminated Composite Structures

    NASA Technical Reports Server (NTRS)

    Sleight, David W.

    1999-01-01

    A progressive failure analysis method has been developed for predicting the failure of laminated composite structures under geometrically nonlinear deformations. The progressive failure analysis uses C(exp 1) shell elements based on classical lamination theory to calculate the in-plane stresses. Several failure criteria, including the maximum strain criterion, Hashin's criterion, and Christensen's criterion, are used to predict the failure mechanisms and several options are available to degrade the material properties after failures. The progressive failure analysis method is implemented in the COMET finite element analysis code and can predict the damage and response of laminated composite structures from initial loading to final failure. The different failure criteria and material degradation methods are compared and assessed by performing analyses of several laminated composite structures. Results from the progressive failure method indicate good correlation with the existing test data except in structural applications where interlaminar stresses are important which may cause failure mechanisms such as debonding or delaminations.

  4. Nuclear lamins during gametogenesis, fertilization and early development

    NASA Technical Reports Server (NTRS)

    Maul, G. G.; Schatten, G.

    1986-01-01

    The distribution of lamins (described by Gerace, 1978, as major proteins of nuclear envelope) during gametogenesis, fertilization, and early development was investigated in germ cells of a mouse (Mus musculus), an echinoderm (Lytechinus variegatus), and the surf clam (Spisula solidissima) was investigated in order to determine whether the differences detected could be correlated with differences in the function of cells in these stages of the germ cells. In order to monitor the behavior of lamins, the gametes and embryos were labeled with antibodies to lamins A, C, and B extracted from autoimmune sera of patients with scleroderma and Lupus erythematosus. Results indicated that lamin B could be identified in nuclear envelopes on only those nuclei where chromatin is attached and where RNA synthesis takes place.

  5. Analytical displacements and vibrations of cantilevered unsymmetric fiber composite laminates

    NASA Technical Reports Server (NTRS)

    Minich, M. D.; Chamis, C. C.

    1975-01-01

    A fiber composite flat cantilever plate that has symmetric and nonsymmetric laminate configurations is theoretically investigated to determine its static and dynamic structural response. The finite element analysis method used includes a unique triangular finite element developed at Lewis for the analysis of fiber composite airfoils. The various responses investigated include tip displacements, natural frequencies, and fundamental mode shapes. The results show that the displacements and the natural frequencies can be in considerable error for nonsymmetric laminate configurations if the membrane-bending coupling is not taken into account. Structural response results obtained from ten laminate configurations are presented in tabular forms and may be used as an aid in selecting laminate configurations for composite airfoils.

  6. Characterization of delamination onset and growth in a composite laminate

    NASA Technical Reports Server (NTRS)

    Obrien, T. K.

    1981-01-01

    The onset and growth of delaminations in unnotched (+ or - 30/+ or - 30/90/90 bar) sub S graphite epoxy laminates is described quantitatively. These laminates, designed to delaminate at the edges under tensile loads, were tested and analyzed. Delamination growth and stiffness loss were monitored nondestructively. Laminate stiffness decreased linearly with delamination size. The strain energy release rate, G, associated with delamination growth, was calculated from two analyses. A critical G for delamination onset was determined, and then was used to predict the onset of delaminations in (+45 sub n/-45 sub n/o sub n/90 sub n) sub s (n=1,2,3) laminates. A delamination resistance curve (R curve) was developed to characterize the observed stable delamination growth under quasi static loading. A power law correlation between G and delamination growth rates in fatigue was established.

  7. 11. Detail of laminated arch beams, radiators, pews and portion ...

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

    11. Detail of laminated arch beams, radiators, pews and portion of the office to the left of the sanctuary, facing north - Mountain Home Air Force Base, Base Chapel, 350 Willow Street, Cantonment Area, Mountain Home, Elmore County, ID

  8. INTERIOR OF COMMITTAL SHELTER WITH REAR WALL, FLOOR PATTERN, LAMINATED ...

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

    INTERIOR OF COMMITTAL SHELTER WITH REAR WALL, FLOOR PATTERN, LAMINATED STRUCTURE, AND LIGHT WELLS. VIEW TO SOUTHWEST. - Black Hills National Cemetery, 20901 Pleasant Valley Drive, Sturgis, Meade County, SD

  9. Analysis of a unidirectional, symmetric buffer strip laminate with damage

    NASA Technical Reports Server (NTRS)

    Dharani, L. R.; Goree, J. G.

    1984-01-01

    A method for predicting the fracture behavior of hybrid buffer strip laminates is presented in which the classical shear-lag model is used to represent the shear stress distribution between adjacent fibers. The method is demonstrated by applying it to a notched graphite/epoxy laminate, and the results show clearly the manner in which the most efficient combination of buffer strip properties can be selected in order to arrest the crack. The ultimate failure stress of the laminate is plotted vs the buffer strip width. It is shown that in the case of graphite-epoxy and S-glass epoxy laminates, the optimum buffer strip spacing to width ratio should be about four to one.

  10. Nonlinear analysis of laminated fibrous composites. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Renieri, G. D.; Herakovich, C. T.

    1976-01-01

    A computerized analysis of the nonlinear behavior of fibrous composite laminates including axial loading, thermal loading, temperature dependent properties, and edge effects is presented. Ramberg-Osgood approximations are used to represent lamina stress-strain behavior and percent retention curves are employed to model the variation of properties with temperature. Balanced, symmetric laminates comprised of either boron/epoxy, graphite/epoxy, or borsic-aluminum are analyzed using a quasi-three-dimensional finite element analysis. Results are presented for the interlaminar stress distributions in cross-ply, angle-ply, and more complex laminates. Nonlinear stress-strain curves for a variety of composite laminates in tension and compression are obtained and compared to other existing theories and experimental results.

  11. Observation of damage growth in compressively loaded laminates

    NASA Technical Reports Server (NTRS)

    Knauss, W. G.; Babcock, C. D.; Chai, H.

    1983-01-01

    Graphite/epoxy laminates have a definite advantage with respect to the strength-to-weight relation over many standard engineering materials used in aerospace applications. However, this advantage is somewhat reduced by the sensitivity of these laminates to operational hazards, which include a low-velocity impact by foreign objects. Investigations conducted by Chai (1982) and Knauss et al. (1980) have been concerned with the growth of impact damage in compressively loaded laminates, and the visualization of such an impact damage. The present study represents a condensation of parts of these investigations, taking into account a determination of the damage-growth mechanism via real-time recording of the impact event. The material considered, a T300/5208 graphite/epoxy laminate, is typical of the configuration proposed for future heavily loaded primary structures. It has stiffness properties similar to those of the wing skins in existing transport aircraft.

  12. Laminated metamaterial flat lens at millimeter-wave frequencies.

    PubMed

    Kitayama, Daisuke; Yaita, Makoto; Song, Ho-Jin

    2015-09-01

    A flat and thin shape is obviously advantageous not only in terms of reducing the volume of a device, but also in handling and using it. Particularly, laminating or stacking flat devices is an intuitive and straightforward way of tailoring performance and functions. Here, we experimentally demonstrated a laminated flat lens for millimeter-wave frequencies that is based on split-ring resonators (SRRs) composed of multiple layers with different and/or identical index profiles and that exhibits characteristics that are linear combinations of those of the individual lenses. Since the characteristics of the lenses of each layer are preserved regardless of the neighbouring layers, the desired functionalities can be easily implemented simply by laminating elementary lenses designed already. When we laminated two lenses designed for bending or focusing incoming waves at 120 GHz, we clearly observed that the outgoing waves collimated and bended as desired. PMID:26368436

  13. Vibration Analysis of Composite Laminate Plate Excited by Piezoelectric Actuators

    PubMed Central

    Her, Shiuh-Chuan; Lin, Chi-Sheng

    2013-01-01

    Piezoelectric materials can be used as actuators for the active vibration control of smart structural systems. In this work, piezoelectric patches are surface bonded to a composite laminate plate and used as vibration actuators. A static analysis based on the piezoelectricity and elasticity is conducted to evaluate the loads induced by the piezoelectric actuators to the host structure. The loads are then employed to develop the vibration response of a simply supported laminate rectangular plate excited by piezoelectric patches subjected to time harmonic voltages. An analytical solution of the vibration response of a simply supported laminate rectangular plate under time harmonic electrical loading is obtained and compared with finite element results to validate the present approach. The effects of location and exciting frequency of piezoelectric actuators on the vibration response of the laminate plate are investigated through a parametric study. Numerical results show that modes can be selectively excited, leading to structural vibration control. PMID:23529121

  14. Coulomb-stable triply charged diatomic: HeY3+

    NASA Astrophysics Data System (ADS)

    Wesendrup, Ralf; Pernpointner, Markus; Schwerdtfeger, Peter

    1999-11-01

    Accurate relativistic coupled-cluster calculations show that the triply charged species HeY3+ is a stable molecule and represents the lightest diatomic trication that does not undergo a Coulomb fragmentation into charged fragments. The diatomic potential-energy curve is approximated by an extended Morse potential, and vibrational-rotational constants for HeY3+ are predicted (Re=224.3 pm, D0=0.394 eV, ?e=437 cm-1, ?exe=15.8 cm-1, Be=0.877 cm-1). It is further shown that the He-Y3+ bond can basically be described as a charge-induced dipole interaction.

  15. Analysis of exchange energy at long range for heteronuclear diatomics

    NASA Astrophysics Data System (ADS)

    Sheng, Xiaowei

    2015-04-01

    The present paper shows that the exchange energies of heteronuclear diatomics can be well fitted with simple analytical expressions. For heteronuclear diatomics with two atoms having large difference of ionization energies, the exchange energies can be closely fitted with - C R b e - 4 R/( b + 2). In cases where the constituent atoms have similar ionization energies, - C R b e - 7 R/( b + 1) fits the exchange energies very well. In addition, the parameter b, in general, can be well estimated with the atomic ionization energy.

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

    PubMed

    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. PMID:20737117

  17. Species-specific polyamines from diatoms control silica morphology

    NASA Astrophysics Data System (ADS)

    Krger, Nils; Deutzmann, Rainer; Bergsdorf, Christian; Sumper, Manfred

    2000-12-01

    Biomineralizing organisms use organic molecules to generate species-specific mineral patterns. Here, we describe the chemical structure of long-chain polyamines (up to 20 repeated units), which represent the main organic constituent of diatom biosilica. These substances are the longest polyamine chains found in nature and induce rapid silica precipitation from a silicic acid solution. Each diatom is equipped with a species-specific set of polyamines and silica-precipitating proteins, which are termed silaffins. Different morphologies of precipitating silica can be generated by polyamines of different chain lengths as well as by a synergistic action of long-chain polyamines and silaffins.

  18. Effects of diatomic reagent alignment on the A + BC reaction

    NASA Technical Reports Server (NTRS)

    Pattengill, M. D.; Zare, R. N.; Jaffe, R. L.

    1987-01-01

    A computational study is reported on the A + BC - AB + C bimolecular exchange reaction in which BC is aligned with respect to the approach direction of atom A so that the initial rotational angular momentum vector of BC is either parallel (or equivalently antiparallel) or perpendicular to the initial velocity vector of A. The calculations employ a modification of the extended LEPS potential, which permits straightforward generation of noncollinear minimum energy reaction paths. The calculations clearly demonstrate that diatomic reagent alignment can markedly affect the nature of reaction product early partitioning; they also demonstrate that diatomic reagent alignment affects reactive cross sections.

  19. Ab initio calculations of the photoionization of diatomic molecules

    NASA Astrophysics Data System (ADS)

    Lefebvre-Brion, Helene; Ra?eev, Georges

    2003-01-01

    A review is presented of the calculation of photoionization spectra, particularly in the spectral range where electron autoionization of diatomic molecules takes place. In addition to some interesting results obtained over years that compare favourably with experiment, the emphasis here is put on the relation between the methods developed for the calculation of observables associated with the continuum energy spectrum of the electrons and the Alchemy system of programs. This system of programs serves as a basis for initial and intermediate calculations. The examples presented show that diatomic molecules not only in gas phase but also oriented in space or physisorbed at surfaces may be studied readily.

  20. Tunable dark modes in one-dimensional "diatomic" dielectric gratings.

    PubMed

    Zeng, Bo; Majumdar, Arka; Wang, Feng

    2015-05-18

    Recently researchers have demonstrated ultra high quality factor (Q) resonances in one-dimensional (1D) dielectric gratings. Here we theoretically investigate a new class of subwavelength 1D gratings, namely "diatomic" gratings with two nonequivalent subcells in one period, and utilize their intrinsic dark modes to achieve robust ultra high Q resonances. Such "diatomic" gratings provide extra design flexibility, and enable high Q resonators using thinner geometry with smaller filling factors compared to conventional designs like the high contrast gratings (HCGs). More importantly, we show that these high Q resonances can be efficiently tuned in situ, making the design appealing in various applications including optical sensing, filtering and displays. PMID:26074503

  1. Relativistic Effects Break Periodicity in Group 6 Diatomic Molecules.

    PubMed

    Wang, Yi-Lei; Hu, Han-Shi; Li, Wan-Lu; Wei, Fan; Li, Jun

    2016-02-01

    The finding of the periodic law is a milestone in chemical science. The periodicity of light elements in the Periodic Table is fully accounted for by quantum mechanics. Here we report that relativistic effects change the bond multiplicity of the group 6 diatomic molecules M2 (M = Cr, Mo, W, Sg) from hextuple bonds for Cr2, Mo2, W2 to quadruple bonds for Sg2, thus breaking the periodicity in the nonrelativistic domain. The same trend is also found for other superheavy-element diatomics Rf2, Db2, Bh2, and Hs2. PMID:26787134

  2. Modeling of atom-diatom scattering. Technical report

    SciTech Connect

    Sindoni, J.M.

    1992-05-30

    This report entails the work performed on modeling atom-diatom scattering processes utilizing the Impulse Approach (IA). Results of the model, obtained with a computer code, have proven to be in remarkable agreement with laboratory measurements for several atom-diatom scattering systems. Two scattering systems, in particular, that were successfully modeled and compared to measurements were Ar-KBr and Ar-CsF. The IA model provided an explanation for the rapid deactivation evident in the Ar-KBr system. Experimental results in the Ar-CsF experiment that could not be explained by conventional models were also successfully modeled using the IA. Results fit the experimental observations.

  3. Distribution of Epiphytic Diatoms in a Sub-Tropical Estuary

    NASA Astrophysics Data System (ADS)

    Frankovich, T. A.; Gaiser, E. E.; Wachnicka, A.; Zieman, J. C.

    2005-05-01

    Within estuaries, seagrasses may represent an order of magnitude greater surface area relative to sediments for the colonization and growth of diatoms. Fossil diatom distributions have proven useful in inferring paleoenvironmental conditions. The strength of these inferences is dependent upon defining the environmental relationships of contempory diatom compositions. The present investigation characterized the modern epiphytic diatom flora on the seagrass Thalassia testudinum at seven sites in the sub-tropical Florida Bay estuary and at one Atlantic Ocean site east of the upper Florida Keys. These sites were sampled six times between March 2000 and April 2001. Diatom species composition was related to water quality parameters using multivariate statistics. 338 diatom species were identified. The seven most abundant species from pooled samples were Cocconeis placentula, Brachysira aponina, Nitzschia liebetruthii, Hyalosynedra laevigata, Amphora cf. tenerrima, Mastogloia crucicula, and M. pusilla. These seven species collectively accounted for 51.7 percent of all valves counted and occurred in at least 85 percent of all samples. Analysis of similiarity and NMDS ordination of species relative abundances revealed four distinct diatom communities across the study region. The spatial variability of these communities was correlated with salinity and water-column nutrient availability. Summertime communities were significantly different from winter-spring communities, but these communities showed a gradual temporal progression with much overlap. The temporal variability was correlated with temperature. Indicator species analysis identified many species significantly influencing the four spatial groups. The Atlantic marine site was characterized by many different Mastogloia species and some epipsammic (sand-grain associated) diatoms (i.e., Cymatosira lorenziana, Dimerogramma dubium, and Neofragilaria nicobarica). Mastogloia pusilla, Rhopalodia pacifica, and Cocconeis woodii were strong indicators of the Gulf of Mexico marine site. Reimerothrix floridensis was particularly abundant in the western interior of Florida Bay (i.e., sites 2, 3, and 4) during summer months. The eastern interior of Florida Bay was characterized by high relative abundances of Brachysira aponina and Nitzschia liebetruthii. The optima and tolerance of these indicator species relative to individual water quality parameters were also determined.

  4. Stairway fracture architecture in laminated to finely stratified rocks

    NASA Astrophysics Data System (ADS)

    Maggi, Matteo; Cianfarra, Paola; Salvini, Francesco

    2014-05-01

    In this work we present the result of a study dealing on the architecture of fractures in laminated rocks, where they develop accordingly to a stairway architecture. On a section perpendicular to the sedimentary layering/structure intersection, this architecture consists of stepping fracture segments running parallel to the lamination/layering (LaP) connected by ramp segments (R) cutting across the laminations. The presence of lamination produces an anisotropy that deviates the average fracture propagation. The presence of LaP segments strongly influences the fracture induced permeability in these rocks by increasing connectivity. These fractures are formed by either the coalescence of individual fractures (representing the ramp segments) or as the result of a single propagating fracture. Stairway fractures are likely to form during syn-diagenetic conditions. Depending on the original lamination dip, a component of rock sliding may trigger or enhance the fracturing process. The architecture of stairway fractures is parameterized by the L/R ratio (the ratio between the lengths of the Ramp and LaP segments), the original lamination dip, and the cut-off angle (the angle between the ramp segment of the fracture and the lamination), in turn depending from the stress regime. Successive tilting may tilt the original lamination dip. In this view, the cut-off angle results a particularly suited parameter being related to the interplay between the rheology of the layers and the stress conditions at failure. A physical model of stairway fractures has been developed considering the effect of the rheological contrast between the layer and the intra-layer infilling, the fluid overpressure and the overburden. The model has been successfully applied to laminated rocks outcrops. The rheological parameters needed to match the observed geometry were obtained using a Montecarlo approach. The obtained rheological parameters are comparable with those presented in the literature and justify the LaP/Ramp proposed model. Two distinct behaviors were found and quantified depending on the original lamination/layers dip. Fluid pressure plays an important role in the development of the LaP segments. Resulting model may be applied to model fracture-induced permeability in laminated fluid reservoirs.

  5. Sediment sources and sedimentation processes of 2011 Tohoku-oki tsunami deposits on the Sendai Plain, Japan — Insights from diatoms, nannoliths and grain size distribution

    NASA Astrophysics Data System (ADS)

    Szczuciński, Witold; Kokociński, Mikołaj; Rzeszewski, Michał; Chagué-Goff, Catherine; Cachão, Mario; Goto, Kazuhisa; Sugawara, Daisuke

    2012-12-01

    The 11th March 2011 Tohoku-oki tsunami inundated the low-lying Sendai Plain (Japan) more than 5 km inland leaving sand and mud deposits over most of the area. In order to establish the sources of the tsunami deposits and interpret processes of their sedimentation, samples were collected from the deposits, underlying soils and the beach along a shore-perpendicular transect and analysed for grain size, diatom assemblages and nannoliths. The fining-inland tsunami deposits consisted of poorly to moderately sorted medium to coarse sand within 2 km of the coastline and very poorly to poorly sorted mud farther inland. More specifically, there was a slight fining of the coarse to medium sand mode within the sandy deposits and an increased contribution of the coarse and very coarse silt fraction in the mud deposits. The tsunami deposits also exhibited vertical changes including fining upward and coupled coarsening-fining upward trends. Few diatoms were present in beach sediments, soils and tsunami deposits within 1 km of the coastline, while diatoms were more abundant farther inland. Diatom assemblages in the soil and tsunami deposits were similar and dominated by species typical of freshwater-brackish habitats, while no typically marine species were encountered. Nannoliths were generally absent in the studied sediments, except for few specimens. Our data indicate that there was probably no or only a very minor component of marine sediments transported onland by the tsunami. The sandy tsunami deposits within ~ 1 km of the coastline were mostly derived from beach and dune erosion. From 1 to 2 km landward the contribution of these sources decreased, while sources comprising local soil erosion and the entrainment of sediments from the Teizan-bori canal increased. Farther inland, local soil erosion was the major sediment source for the mud deposits. The tsunami deposits were most likely deposited during at least two inundations, mostly out from suspension resulting in an upward grain size fining trend. However, bed load deposition was also important in the sandy deposits as suggested by a common grain size upward coarsening, position on C-M diagrams and frequent horizontal lamination. The present study reveals that even very large tsunamis may not transport marine sediments onland and thus many commonly applied indicators of tsunami deposits based on the assumption of their offshore origin (marine diatoms, foraminifera, nannoliths, marine sediments) may be of limited use.

  6. Equine laminitis: a journey to the dark side of venous.

    PubMed

    Robertson, Tom P; Bailey, Simon R; Peroni, John F

    2009-06-15

    Equine laminitis is a crippling condition that continues to defy repeated efforts to delineate the precise mechanisms involved and develop effective therapeutic strategies for use in the clinic. In this article, the possible role of dysfunction of the laminar vasculature is discussed, with particular emphasis on the venous side of the laminar microvasculature and the possible role(s) that metabolic syndrome and thrombosis may play in the dysfunction observed in the laminar microvasculature during the development of laminitis. PMID:19110318

  7. Damage Tolerance of Composite Laminates from an Empirical Perspective

    NASA Technical Reports Server (NTRS)

    Nettles, Alan T.

    2009-01-01

    Damage tolerance consists of analysis and experimentation working together. Impact damage is usually of most concern for laminated composites. Once impacted, the residual compression strength is usually of most interest. Other properties may be of more interest than compression (application dependent). A damage tolerance program is application specific (not everyone is building aircraft). The "Building Block Approach" is suggested for damage tolerance. Advantage can be taken of the excellent fatigue resistance of damaged laminates to save time and costs.

  8. Review on antibacterial biocomposites of structural laminated veneer lumber

    PubMed Central

    Chen, Zi-xiang; Lei, Qiong; He, Rui-lin; Zhang, Zhong-feng; Chowdhury, Ahmed Jalal Khan

    2015-01-01

    In this review, the characteristics and applications of structural laminated veneer lumber made from planted forest wood is introduced, and its preparation is explained, including various tree species and slab qualities, treatments for multiple effects and reinforced composites. The relevant factors in the bonding technology and pressing processes as well as the mechanical properties, research direction and application prospects of structural laminated veneer lumber made from planted forest wood are discussed. PMID:26858559

  9. Determination of the technical constants of laminates in oblique directions

    NASA Technical Reports Server (NTRS)

    Vidouse, F.

    1979-01-01

    An off-axis tensile test theory based on Hooke's Law is applied to glass fiber reinforced laminates. A corrective parameter dependent on the characteristics of the strain gauge used is introduced by testing machines set up for isotropic materials. Theoretical results for a variety of strain gauges are compared with those obtained by a finite element method and with experimental results obtained on laminates reinforced with glass.

  10. Support Assembly for Composite Laminate Materials During Roll Press Processing

    NASA Technical Reports Server (NTRS)

    Catella, Luke A.

    2011-01-01

    A composite laminate material is supported during the roll press processing thereof by an assembly having: first and second perforated films disposed adjacent to first and second opposing surfaces of a mixture of uncured resin and fibers defining the composite laminate material, a gas permeable encasement surrounding the mixture and the first and second films, a gas impervious envelope sealed about the gas permeable encasement, and first and second rigid plates clamped about the gas impervious envelope.

  11. Higher order finite element analysis of thick composite laminates

    NASA Technical Reports Server (NTRS)

    Goering, J.; Kim, H. J.

    1992-01-01

    A higher order, sub-parametric, laminated, 3D solid finite element was used for the analysis of very thick laminated composite plates. The geometry of this element is defined by four nodes in the X-Y plane which define a prism of material through the thickness of the laminate. There are twenty-four degrees of freedom at each node; translations at the upper and lower surfaces of the laminate in each of the three coordinate directions, and the derivatives of these translations with respect to each coordinate. This choice of degrees of freedom leads to displacement and strain compatibility at the corners. Stacking sequence effects are accounted for by explicitly integrating the strain energy density through the thickness of the element. The laminated solid element was combined with a gap-contact element to analyze thick laminated composite lugs loaded through flexible pins. The resulting model accounts for pin bending effects that produce non-uniform bearing stresses through the thickness of the lug. A thick composite lug experimental test program was performed, and provided data that was used to validate the analytical model. Two lug geometries and three stacking sequences were tested.

  12. Association of the glycoxidative stress marker pentosidine with equine laminitis.

    PubMed

    Valle, E; Storace, D; Sanguineti, R; Carter, R; Odetti, P; Geor, R; Bergero, D

    2013-06-01

    Ponies suffering from recurrent episodes of laminitis when grazed at pasture (pasture-associated laminitis) exhibit phenotypes similar to those associated with human metabolic syndrome. In humans, evidence suggests that the obesity-related morbidities associated with metabolic syndrome, including diabetes and cardiovascular disease, are caused by an increase in the production of advanced glycoxidation end-products (AGEs). These end-products have been recognised as putative pro-inflammatory mediators and are considered a 'risk factor' for human health. However, the evaluation of AGEs in laminitic ponies has not been explored. The aim of this study was to compare plasma concentrations of the AGE pentosidine (PENT) in ponies presenting with clinical features of equine metabolic syndrome (EMS) with a history of recent laminitis and/or showing signs of laminitis at the time of sampling (LP) with those with no prior history of clinical laminitis (NL). Age, body condition score (BCS) and bodyweight were recorded and blood samples collected for the measurement of plasma concentrations of PENT, glucose, insulin, triglycerides (TG), non-esterified fatty acids (NEFA) and cortisol. Insulin sensitivity was assessed by the reciprocal of the square root of insulin (RISQI) and the insulin:glucose ratio. Plasma PENT concentrations were twofold higher (P<0.005) in LP than in NL ponies. Significant (P<0.05) correlations were also evident between PENT and insulin, RISQI, TG and age. These preliminary findings are consistent with the hypothesis that glycoxidation in laminitis is associated with EMS. PMID:23206662

  13. BioID Identification of Lamin-Associated Proteins.

    PubMed

    Mehus, Aaron A; Anderson, Ruthellen H; Roux, Kyle J

    2016-01-01

    A- and B-type lamins support the nuclear envelope, contribute to heterochromatin organization, and regulate a myriad of nuclear processes. The mechanisms by which lamins function in different cell types and the mechanisms by which lamin mutations cause over a dozen human diseases (laminopathies) remain unclear. The identification of proteins associated with lamins is likely to provide fundamental insight into these mechanisms. BioID (proximity-dependent biotin identification) is a unique and powerful method for identifying protein-protein and proximity-based interactions in living cells. BioID utilizes a mutant biotin ligase from bacteria that is fused to a protein of interest (bait). When expressed in living cells and stimulated with excess biotin, this BioID-fusion protein promiscuously biotinylates directly interacting and vicinal endogenous proteins. Following biotin-affinity capture, the biotinylated proteins can be identified using mass spectrometry. BioID thus enables screening for physiologically relevant protein associations that occur over time in living cells. BioID is applicable to insoluble proteins such as lamins that are often refractory to study by other methods and can identify weak and/or transient interactions. We discuss the use of BioID to elucidate novel lamin-interacting proteins and its applications in a broad range of biological systems, and provide detailed protocols to guide new applications. PMID:26778550

  14. Stochastic damage evolution modeling in laminates. Ph.D. Thesis

    SciTech Connect

    Dzenis, Y.A.

    1994-01-01

    A stochastic mesomechanics model has been developed for damage accumulation analysis in advanced laminated composites. The model is based on a theory of excursions of random process beyond the limiting bounds. Stochastic strains in the laminate subjected to random Gaussian in-plane loading are calculated using lamination theory and random functions theory. Probabilistic variation of stiffness and strength characteristics of plies are used in the analysis. A stochastic version of maximum strain failure criterion is applied for damage probability calculation. A mesovolume concept is utilized in modeling stiffness degradation. The model is verified experimentally based on the available data. Capabilities of the model are illustrated by predictions of damage accumulation and failure in a Kevlar/epoxy (0/ +/- 30/90){sub s} laminate under quasistationary, long-term stationary, and cyclic loading. Effects of loading rate, deviation, stationary level and cyclic amplitude on damage evolution are discussed. High-cycle fatigue behavior of laminate is calculated utilizing the observed stages in failure accumulation under the cyclic loading. Percolation type analysis of damage morphology is performed for the inhomogeneous anisotropic media. The model and computer codes developed can be incorporated into structural analysis software and used in design of laminated structures.

  15. Properties of wheat gluten/poly(lactic acid) laminates.

    PubMed

    Cho, Sung-Woo; Gllstedt, Mikael; Hedenqvist, Mikael S

    2010-06-23

    Laminates of compression-molded glycerol-plasticized wheat gluten (WG) films surrounded and supported by poly(lactic acid) (PLA) films have been produced and characterized. The objective was to obtain a fully renewable high gas barrier film with sufficient mechanical integrity to function in, for example, extrusion-coating paper/board applications. It was shown that the lamination made it possible to make films with a broad range of glycerol contents (0-30 wt %) with greater strength than single unsupported WG films. The low plasticizer contents yielded laminates with very good oxygen barrier properties. In addition, whereas the unsupported WG films had an immeasurably high water vapor transmission rate (WVTR), the laminate showed values that were finite and surprisingly, in several cases, also lower than that of PLA. Besides being a mechanical support (as evidenced by bending and tensile data) and a shield between the WG and surrounding moisture, the PLA layer also prevented the loss of the glycerol plasticizer from the WG layer. This was observed after the laminate had been aged on an "absorbing" blotting paper for up to 17 weeks. The interlayer adhesion (peel strength) decreased with decreasing glycerol content and increasing WG film molding temperature (130 degrees C instead of 110 degrees C). The latter effect was probably due to a higher protein aggregation, as revealed by infrared spectroscopy. The lamination temperature (110-140 degrees C) did not, however, have a major effect on the final peel strength. PMID:20504031

  16. Tracer Lamination in the Stratosphere: A Global Climatology

    NASA Technical Reports Server (NTRS)

    Appenzeller, Christof; Holton, James R.

    1997-01-01

    Vertical soundings of stratospheric ozone often exhibit laminated tracer structures characterized by strong vertical tracer gradients. The change in time of these gradients is used to define a tracer lamination rate. It is shown that this quantity can be calculated by the cross product of the horizontal temperature and horizontal tracer gradients. A climatology based on UARS satellite-borne ozone data and on ozone-like pseudotracer data is presented. Three stratospheric regions with high lamination rates were found: the part of the stratospheric overworld which is influenced by the polar vortex, the part of the lowermost stratosphere which is influenced by the tropopause and a third region in the subtropical lower stratosphere mainly characterized with strong vertical shear. High lamination rates in the stratospheric overworld were absent during summer, whereas in the lowermost stratosphere high lamination rates were found year-round. This is consistent with the occurrence and seasonal variation of the horizontal tracer gradient and vertical shear necessary for tilting the tracer surfaces. During winter, high lamination rates associated with the stratospheric polar vortex are present down to approximately 100 hPa. Several features of the derived climatology are roughly consistent with earlier balloon-borne studies. The patterns in the southern and northern hemisphere are comparable, but details differ as anticipated from a less disturbed and more symmetric southern polar vortex.

  17. Bending Boundary Layers in Laminated-Composite Circular Cylindrical Shells

    NASA Technical Reports Server (NTRS)

    Nemeth, Michael P.; Smeltzer, Stanley S., III

    2000-01-01

    An analytical, parametric study of the attenuation of bending boundary layers or edge effects in balanced and unbalanced, symmetrically and unsymmetrically laminated thin cylindrical shells is presented for nine contemporary material systems. The analysis is based on the linear Sanders-Koiter shell equations and specializations to the Love-Kirchhoff shell equations and Donnell's equations are included. Two nondimensional parameters are identified that characterize and quantify the effects of laminate orthotropy and laminate anisotropy on the bending boundary-layer decay length in a very general and encompassing manner. A substantial number of structural design technology results are presented for a wide range of laminated-composite cylinders. For all the laminate constructions considered, the results show that the differences between results that were obtained with the Sanders-Koiter shell equations, the Love-Kirchhoff shell equations, and Donnell's equations are negligible. The results also show that the effect of anisotropy in the form of coupling between pure bending and twisting has a negligible effect on the size of the bending boundary-layer decay length of the balanced, symmetrically laminated cylinders considered. Moreover, the results show that coupling between the various types of shell anisotropies has a negligible effect on the calculation of the bending boundary-layer decay length in most cases. The results also show that in some cases neglecting the shell anisotropy results in underestimating the bending boundary-layer decay length and in other cases it results in an overestimation.

  18. Three dimensional inelastic finite element analysis of laminated composites

    NASA Technical Reports Server (NTRS)

    Griffin, O. H., Jr.; Kamat, M. P.

    1980-01-01

    Formulations of the inelastic response of laminated composites to thermal and mechanical loading are used as the basis for development of the computer NALCOM (Nonlinear Analysis of Laminated Composites) computer program which uses a fully three dimensional isoparametric finite element with 24 nodes and 72 degrees of freedom. An incremental solution is performed with nonlinearities introduced as pseudoloads computed for initial strains. Equilibrium iteration may be performed at every step. Elastic and elastic-plastic response of boron/epoxy and graphite/epoxy graphite/epoxy and problems of curing 0/90 sub s Gr/Ep laminates with and without circular holes are analyzed. Mechanical loading of + or - 45sub s Gr/Ep laminates is modeled and symmetry conditions which exist in angle-ply laminates are discussed. Results are compared to experiments and other analytical models when possible. All models are seen to agree reasonably well with experimetnal results for off-axis tensile coupons. The laminate analyses show the three dimensional effects which are present near holes and free corners.

  19. Diatoms in Historical Tsunami Deposits, Northern California, USA

    NASA Astrophysics Data System (ADS)

    Hemphill-Haley, E.; Loofbourrow, C.

    2013-12-01

    A fundamental challenge in using microfossils to differentiate paleotsunami deposits from those of other sources (storms, floods) is to identify characteristics that favor one mode of deposition over the other. The silt- to sand-size siliceous hard parts (valves) of diatoms are commonly found as transported particles in tsunami deposits, but logically, may also be found in other types of coastal deposits of the same grain size. To date, observations on diatom preservation and provenance have been invoked as supporting evidence for paleotsunami deposits. These observations can be tested and refined by detailed observations of diatom assemblages in recent, well-documented tsunami deposits. As a component of the U.S. Geological Survey Science Application for Risk Reduction (SAFRR) project, diatoms were examined in two historical tsunami deposits on the central and northern California coast: the 1946 deposit on the north end of Half Moon Bay (37.5N) and the 1964 deposit about 10 km south of Crescent City (41.7N). Both tsunamis were the result of distant-source events across the Pacific Ocean from California: the M 8.1 Eastern Aleutians Islands earthquake (1946) and the M 9.2 Alaska earthquake (1964). At both localities tsunami inundation was documented by eyewitness accounts. The deposits are now preserved in the shallow subsurface as ~1-10 cm thick layers of silt and sand intercalated in peaty marsh or clay-rich lagoon deposits. These historical tsunami deposits are particularly useful for documenting characteristics of entrained diatom assemblages for comparison to paleotsunami deposits. First, the deposits consist of mostly fine sand and silt, and therefore are an appropriate particle size for containing diatoms. Second, although they are recent enough to have been documented by eyewitness accounts, they are also old enough to have been altered by natural geological processes (e.g., burial, compaction, taphonomic affects on diatom valves) as would be found in paleotsunami deposits. Finally, although they are both the result of deposition by a distant-source tsunami at a coastal location not affected by coincident earthquake deformation (i.e., non-subsiding coast), they accumulated and were preserved in different kinds of coastal environments, and therefore the diatom records for each are different. At Half Moon Bay, the 1946 tsunami swept across a shallow brackish lagoon and salt marsh, leaving a deposit of clean, very fine sand containing large, allochthonous epipsammic diatoms consistent with landward-directed transport from the adjacent shallow marine nearshore. Where the deposit settled out and was later buried by clay-rich lagoon deposits, both the tsunami sand layer and entrained diatoms are well preserved. In contrast to the open, preservation-conducive lagoon environment at Half Moon Bay, the 1964 tsunami south of Crescent City inundated a freshwater marsh with thick stands of vegetation. The resultant paleotsunami deposit is limited in lateral extent, and dominantly contains well-preserved freshwater diatoms that mask obvious evidence of marine inundation.

  20. R-Syst::diatom: an open-access and curated barcode database for diatoms and freshwater monitoring.

    PubMed

    Rimet, Frédéric; Chaumeil, Philippe; Keck, François; Kermarrec, Lenaïg; Vasselon, Valentin; Kahlert, Maria; Franc, Alain; Bouchez, Agnès

    2016-01-01

    Diatoms are micro-algal indicators of freshwater pollution. Current standardized methodologies are based on microscopic determinations, which is time consuming and prone to identification uncertainties. The use of DNA-barcoding has been proposed as a way to avoid these flaws. Combining barcoding with next-generation sequencing enables collection of a large quantity of barcodes from natural samples. These barcodes are identified as certain diatom taxa by comparing the sequences to a reference barcoding library using algorithms. Proof of concept was recently demonstrated for synthetic and natural communities and underlined the importance of the quality of this reference library. We present an open-access and curated reference barcoding database for diatoms, called R-Syst::diatom, developed in the framework of R-Syst, the network of systematic supported by INRA (French National Institute for Agricultural Research), see http://www.rsyst.inra.fr/en. R-Syst::diatom links DNA-barcodes to their taxonomical identifications, and is dedicated to identify barcodes from natural samples. The data come from two sources, a culture collection of freshwater algae maintained in INRA in which new strains are regularly deposited and barcoded and from the NCBI (National Center for Biotechnology Information) nucleotide database. Two kinds of barcodes were chosen to support the database: 18S (18S ribosomal RNA) and rbcL (Ribulose-1,5-bisphosphate carboxylase/oxygenase), because of their efficiency. Data are curated using innovative (Declic) and classical bioinformatic tools (Blast, classical phylogenies) and up-to-date taxonomy (Catalogues and peer reviewed papers). Every 6 months R-Syst::diatom is updated. The database is available through the R-Syst microalgae website (http://www.rsyst.inra.fr/) and a platform dedicated to next-generation sequencing data analysis, virtual_BiodiversityL@b (https://galaxy-pgtp.pierroton.inra.fr/). We present here the content of the library regarding the number of barcodes and diatom taxa. In addition to these information, morphological features (e.g. biovolumes, chloroplasts…), life-forms (mobility, colony-type) or ecological features (taxa preferenda to pollution) are indicated in R-Syst::diatom.Database URL: http://www.rsyst.inra.fr/. PMID:26989149

  1. R-Syst::diatom: an open-access and curated barcode database for diatoms and freshwater monitoring

    PubMed Central

    Rimet, Frédéric; Chaumeil, Philippe; Keck, François; Kermarrec, Lenaïg; Vasselon, Valentin; Kahlert, Maria; Franc, Alain; Bouchez, Agnès

    2016-01-01

    Diatoms are micro-algal indicators of freshwater pollution. Current standardized methodologies are based on microscopic determinations, which is time consuming and prone to identification uncertainties. The use of DNA-barcoding has been proposed as a way to avoid these flaws. Combining barcoding with next-generation sequencing enables collection of a large quantity of barcodes from natural samples. These barcodes are identified as certain diatom taxa by comparing the sequences to a reference barcoding library using algorithms. Proof of concept was recently demonstrated for synthetic and natural communities and underlined the importance of the quality of this reference library. We present an open-access and curated reference barcoding database for diatoms, called R-Syst::diatom, developed in the framework of R-Syst, the network of systematic supported by INRA (French National Institute for Agricultural Research), see http://www.rsyst.inra.fr/en. R-Syst::diatom links DNA-barcodes to their taxonomical identifications, and is dedicated to identify barcodes from natural samples. The data come from two sources, a culture collection of freshwater algae maintained in INRA in which new strains are regularly deposited and barcoded and from the NCBI (National Center for Biotechnology Information) nucleotide database. Two kinds of barcodes were chosen to support the database: 18S (18S ribosomal RNA) and rbcL (Ribulose-1,5-bisphosphate carboxylase/oxygenase), because of their efficiency. Data are curated using innovative (Declic) and classical bioinformatic tools (Blast, classical phylogenies) and up-to-date taxonomy (Catalogues and peer reviewed papers). Every 6 months R-Syst::diatom is updated. The database is available through the R-Syst microalgae website (http://www.rsyst.inra.fr/) and a platform dedicated to next-generation sequencing data analysis, virtual_BiodiversityL@b (https://galaxy-pgtp.pierroton.inra.fr/). We present here the content of the library regarding the number of barcodes and diatom taxa. In addition to these information, morphological features (e.g. biovolumes, chloroplasts…), life-forms (mobility, colony-type) or ecological features (taxa preferenda to pollution) are indicated in R-Syst::diatom. Database URL: http://www.rsyst.inra.fr/ PMID:26989149

  2. Analysis of quasi-periodic pore-network structure of centric marine diatom frustules

    NASA Astrophysics Data System (ADS)

    Cohoon, Gregory A.; Alvarez, Christine E.; Meyers, Keith; Deheyn, Dimitri D.; Hildebrand, Mark; Kieu, Khanh; Norwood, Robert A.

    2015-03-01

    Diatoms are a common type of phytoplankton characterized by their silica exoskeleton known as a frustule. The diatom frustule is composed of two valves and a series of connecting girdle bands. Each diatom species has a unique frustule shape and valves in particular species display an intricate pattern of pores resembling a photonic crystal structure. We used several numerical techniques to analyze the periodic and quasi-periodic valve pore-network structure in diatoms of the Coscinodiscophyceae order. We quantitatively identify defect locations and pore spacing in the valve and use this information to better understand the optical and biological properties of the diatom.

  3. Benefits of oxygen incorporation in atomic laminates

    NASA Astrophysics Data System (ADS)

    Dahlqvist, Martin

    2016-04-01

    Atomic laminates such as MAX phases benefit from the addition of oxygen in many ways, from the formation of a protective oxide surface layer with self-healing capabilities when cracks form to the tuning of anisotropic conductivity. In this paper oxygen incorporation and vacancy formation in M 2AlC (M  =  Ti, V, Cr) MAX phases have been studied using first-principles calculations where the focus is on phase stability and electronic structure for different oxygen and/or vacancy configurations. Oxygen prefers different lattice sites depending on M-element and this can be correlated to the number of available non-bonding M d-electrons. In Ti2AlC, oxygen substitutes carbon while in Cr2AlC it is located interstitially within the Al-layer. I predict that oxygen incorporation in Ti2AlC stabilizes the material, which explains the experimentally observed 12.5 at% oxygen (x  =  0.5) in Ti2Al(C1‑x O x ). In addition, it is also possible to use oxygen to stabilize the hypothetical Zr2AlC and Hf2AlC. Hence, oxygen incorporation may be beneficial in many ways. Not only can it make a material more stable, but it also can act as a reservoir for internal self-healing with shorter diffusion paths.

  4. Damage growth in composite laminates with interleaves

    NASA Technical Reports Server (NTRS)

    Goree, James G.

    1987-01-01

    The influence of placing interleaves between fiber reinforced plies in multilayered composite laminates is investigated. The geometry of the composite is idealized as two dimensional, isotropic, linearly elastic media made of a damaged layer bonded between two half planes and separated by thin interleaves of low extensional and shear moduli. The damage in the layer is taken in the form of a symmetric crack perpendicular to the interface and may extend up to the interface. The case of an H-shaped crack in the form of a broken layer with delamination along the interface is also analyzed. The interleaves are modeled as distributed shear and tension springs. Fourier integral transform techniques are used to develop solutions in terms of singular integral equations. An asymptotic analysis of the integral equations based on Muskhelishvili's techniques reveals logarithmically singular axial stresses in the half plane at the crack tips for the broken layer. For the H shaped crack, similar singularities are found to exist in the axial stresses at the interface crack tips in the layer and the half plane. The solution of the equations is found numerically for the stresses and displacements by using the Hadamard's concept of direct differentiation of Cauchy integrals as well as Gaussian integration techniques.

  5. Benefits of oxygen incorporation in atomic laminates.

    PubMed

    Dahlqvist, Martin

    2016-04-01

    Atomic laminates such as MAX phases benefit from the addition of oxygen in many ways, from the formation of a protective oxide surface layer with self-healing capabilities when cracks form to the tuning of anisotropic conductivity. In this paper oxygen incorporation and vacancy formation in M 2AlC (M  =  Ti, V, Cr) MAX phases have been studied using first-principles calculations where the focus is on phase stability and electronic structure for different oxygen and/or vacancy configurations. Oxygen prefers different lattice sites depending on M-element and this can be correlated to the number of available non-bonding M d-electrons. In Ti2AlC, oxygen substitutes carbon while in Cr2AlC it is located interstitially within the Al-layer. I predict that oxygen incorporation in Ti2AlC stabilizes the material, which explains the experimentally observed 12.5 at% oxygen (x  =  0.5) in Ti2Al(C1-x O x ). In addition, it is also possible to use oxygen to stabilize the hypothetical Zr2AlC and Hf2AlC. Hence, oxygen incorporation may be beneficial in many ways. Not only can it make a material more stable, but it also can act as a reservoir for internal self-healing with shorter diffusion paths. PMID:26941112

  6. Progressive Fracture of Laminated Composite Stiffened Plate

    NASA Technical Reports Server (NTRS)

    Gotsis, Pascalis K.; Chamis, Christos C.; David, Kostantinos; Abdi, Frank

    2007-01-01

    Laminated fiber-reinforced composite stiffened plate with [0/90/plus or minus 45]s plies made of S-Glass/epoxy are evaluated via computational simulation to study damage and fracture progression. The loads are pressure and temperature which varies from 21 to 65.5 C (case I) and from 143.3 to 21 C (case II). An integrated computer code is used for the simulation of the damage progression. Results show that damage initiation begins at low load level, with matrix cracking at the 0 deg. (bottom and top) plies, fiber fracture at the bottom (0 deg.) ply and interply delamination at the top (0 deg. ) ply. Increasing the applied pressure, the damage growth is expended resulting in fracture through the thickness of the structure. At this stage, 90 percent of the plies damage at applied pressure 15.306 MPa for the case I and 15.036 MPa for the case II. After this stage the cracks propagate rapidly and the structure collapses.

  7. Testing and simulation of composite laminates under impact loading

    NASA Astrophysics Data System (ADS)

    Dang, Xinglai

    Owing to their high stiffness-to-weight and high strength-to-weight ratios, fiber-reinforced polymer-matrix composite laminates are excellent materials for high-performance structures. However, their properties in the thickness direction are very poor as they are weakly bonded by polymeric matrices through laminate interfaces. Accordingly, when a composite laminate is subjected to impact loading, high interlaminar stresses along with the low interlaminar strengths could easily result in interlaminar damage such as delamination. This thesis investigated the response of composite laminates under low-velocity impact and presented numerical techniques for impact simulation. To begin with, instrumented drop-weight impacts ranging from subperforation to perforation levels were introduced to composite laminates having various dimensions and thicknesses. Damaged composite laminates were then subjected to compression-after-impact tests for evaluations of residual properties. Experimental results revealed that perforation was an important damage milestone since impact parameters such as peak force, contact duration, maximum deflection and energy absorption, and residual properties such as compressive stiffness, strength and energy absorption all reached critical levels as perforation took place. It was also found that thickness played a more important role than in-plane dimensions in perforation process. In order to understand more about the relationship between laminate thickness and perforation resistance and to present an economical method to improve perforation resistance, thick laminated composite plates and their assembled counterparts were investigated and compared. An energy profile correlating the impact energy and absorbed energy at all energy levels for each type of composite plates investigated was established and found to be able to address the relationship between energy and damage. Experimental results concluded that increasing thickness was more efficient than improving assembling stiffness in raising perforation resistance. As a first step to simulate composite response to impact loading, LS-DYNA3D was used for numerical analysis. However, due to its inability to describe interlaminar stresses, no delamination simulation could be achieved. As delamination played a very important role in damage process, a computational scheme capable of identifying interlaminar stresses and considering both numerical accuracy and computational efficiency was required for impact simulation. Accounting for interlaminar shear stress continuity and having degrees of freedom independent of layer number, a laminate theory named Generalized Zigzag Theory was formulated into a finite element subroutine and integrated into ABAQUS code. The computational scheme was able to present reasonable interlaminar shear stresses via an updated Lagragian algorithm. Combining the calculated interlaminar stresses with a delamination failure criterion, the computer program was able to predict the response of composite laminates up to the onset of delamination. Further computational simulation involving all damage modes should be considered in future studies.

  8. Diatom plastids depend on nucleotide import from the cytosol.

    PubMed

    Ast, Michelle; Gruber, Ansgar; Schmitz-Esser, Stephan; Neuhaus, Horst Ekkehard; Kroth, Peter G; Horn, Matthias; Haferkamp, Ilka

    2009-03-01

    Diatoms are ecologically important algae that acquired their plastids by secondary endosymbiosis, resulting in a more complex cell structure and an altered distribution of metabolic pathways when compared with organisms with primary plastids. Diatom plastids are surrounded by 4 membranes; the outermost membrane is continuous with the endoplasmic reticulum. Genome analyses suggest that nucleotide biosynthesis is, in contrast to higher plants, not located in the plastid, but in the cytosol. As a consequence, nucleotides have to be imported into the organelle. However, the mechanism of nucleotide entry into the complex plastid is unknown. We identified a high number of putative nucleotide transporters (NTTs) in the diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum and characterized the first 2 isoforms (NTT1 and NTT2). GFP-based localization studies revealed that both investigated NTTs are targeted to the plastid membranes, and that NTT1 most likely enters the innermost plastid envelope via the stroma. Heterologously expressed NTT1 acts as a proton-dependent adenine nucleotide importer, whereas NTT2 facilitates the counter exchange of (deoxy-)nucleoside triphosphates. Therefore, these transporters functionally resemble NTTs from obligate intracellular bacteria with an impaired nucleotide metabolism rather than ATP/ADP exchanging NTTs from primary plastids. We suggest that diatoms harbor a specifically-adapted nucleotide transport system and that NTTs are the key players in nucleotide supply to the complex plastid. PMID:19221027

  9. CHECKLIST OF DIATOMS FROM THE LAURENTIAN GREAT LAKES

    EPA Science Inventory

    An updated diatom checklist for the Great Lakes is provided. The present checklist supplants the preliminary checklist published in The Journal for Great Lakes Research in 1978 and effectively represents a 20-year update. A series of procedures were used in this update which incl...

  10. Self-Entanglement and the Dissociation of Homonuclear Diatomic Molecules

    SciTech Connect

    Gonis, Antonios; Zhang, Xiaoguang; Nicholson, Don M; Stocks, George Malcolm

    2014-01-01

    The concept of self-entanglement is introduced to describe a mixed state or ensemble density as a pure state in an augmented Hilbert space formed by the products of the individual states forming a mixed state (or ensemble). We use this representation of mixed states to show that upon dissociation a neutral homonuclear diatomic molecule will separate into two neutral atoms.

  11. Contrasting size evolution in marine and freshwater diatoms.

    PubMed

    Litchman, E; Klausmeier, C A; Yoshiyama, K

    2009-02-24

    Diatoms are key players in the global carbon cycle and most aquatic ecosystems. Their cell sizes impact carbon sequestration and energy transfer to higher trophic levels. We report fundamental differences in size distributions of marine and freshwater diatoms, with marine diatoms significantly larger than freshwater species. An evolutionary game theoretical model with empirical allometries of growth and nutrient uptake shows that these differences can be explained by nitrogen versus phosphorus limitation, nutrient fluctuations and mixed layer depth differences. Constant and pulsed phosphorus supply select for small sizes, as does constant nitrogen supply. In contrast, intermediate frequency nitrogen pulses common in the ocean select for large sizes or the evolutionarily stable coexistence of large and small sizes. Size-dependent sinking interacts with mixed layer depth (MLD) to further modulate optimal sizes, with smaller sizes selected for by strong sinking and shallow MLD. In freshwaters, widespread phosphorus limitation, together with strong sinking and shallow MLD produce size distributions with smaller range, means and upper values, compared with the ocean. Shifting patterns of nutrient limitation and mixing may alter diatom size distributions, affecting global carbon cycle and the structure and functioning of aquatic ecosystems. PMID:19202058

  12. Contrasting size evolution in marine and freshwater diatoms

    PubMed Central

    Litchman, E.; Klausmeier, C. A.; Yoshiyama, K.

    2009-01-01

    Diatoms are key players in the global carbon cycle and most aquatic ecosystems. Their cell sizes impact carbon sequestration and energy transfer to higher trophic levels. We report fundamental differences in size distributions of marine and freshwater diatoms, with marine diatoms significantly larger than freshwater species. An evolutionary game theoretical model with empirical allometries of growth and nutrient uptake shows that these differences can be explained by nitrogen versus phosphorus limitation, nutrient fluctuations and mixed layer depth differences. Constant and pulsed phosphorus supply select for small sizes, as does constant nitrogen supply. In contrast, intermediate frequency nitrogen pulses common in the ocean select for large sizes or the evolutionarily stable coexistence of large and small sizes. Size-dependent sinking interacts with mixed layer depth (MLD) to further modulate optimal sizes, with smaller sizes selected for by strong sinking and shallow MLD. In freshwaters, widespread phosphorus limitation, together with strong sinking and shallow MLD produce size distributions with smaller range, means and upper values, compared with the ocean. Shifting patterns of nutrient limitation and mixing may alter diatom size distributions, affecting global carbon cycle and the structure and functioning of aquatic ecosystems. PMID:19202058

  13. Continental erosion and the Cenozoic rise of marine diatoms.

    PubMed

    Cermeño, Pedro; Falkowski, Paul G; Romero, Oscar E; Schaller, Morgan F; Vallina, Sergio M

    2015-04-01

    Marine diatoms are silica-precipitating microalgae that account for over half of organic carbon burial in marine sediments and thus they play a key role in the global carbon cycle. Their evolutionary expansion during the Cenozoic era (66 Ma to present) has been associated with a superior competitive ability for silicic acid relative to other siliceous plankton such as radiolarians, which evolved by reducing the weight of their silica test. Here we use a mathematical model in which diatoms and radiolarians compete for silicic acid to show that the observed reduction in the weight of radiolarian tests is insufficient to explain the rise of diatoms. Using the lithium isotope record of seawater as a proxy of silicate rock weathering and erosion, we calculate changes in the input flux of silicic acid to the oceans. Our results indicate that the long-term massive erosion of continental silicates was critical to the subsequent success of diatoms in marine ecosystems over the last 40 My and suggest an increase in the strength and efficiency of the oceanic biological pump over this period. PMID:25831504

  14. CHECKLIST OF DIATOMS FROM THE LAURENTIAN GREAT LAKES

    EPA Science Inventory

    An updated diatom (Bacillariophyta) checklist for the Great Lakes has been completed (J. Great Lakes Res. 1999) and supplants the preliminary checklist (J. Great Lakes Res. 1978). The present list is effectively a 20-year update. The updated list is based upon: 1) the 1978 checkl...

  15. Diatoms: unique eukaryotic extremophiles providing insights into planetary change

    NASA Astrophysics Data System (ADS)

    Kociolek, J. P.

    2007-09-01

    The diatoms (Division Bacillariophyta) are aquatic, pigmented single-celled photosynthetic eukaryotes. They are a major component of the food chain in marine, estuarine and freshwater ecosystems. These diploid organisms have the ability to take dissolved silica out of the water column, and use it to create their cell walls. The taxonomy and classification system for the group is based to a large part on cell wall symmetry, as well as the number, type, position and organization of the many perforations in the glass. As a group, diatoms are found in almost every water type of water body around the globe, including a wide range of extreme environments. Individual species, however, have limited distributions and ecological requirements. Preservation of the glass cell walls in sedimentary basins has left nearly a 120 million year record. Species-related distributions, and well-preserved record make diatoms an excellent tool for environmental reconstruction and monitoring. New research on diatoms includes applications to conservation biology, astrobiology, nanotechnology, and biofuels.

  16. Diatom plastids depend on nucleotide import from the cytosol

    PubMed Central

    Ast, Michelle; Gruber, Ansgar; Schmitz-Esser, Stephan; Neuhaus, Horst Ekkehard; Kroth, Peter G.; Horn, Matthias; Haferkamp, Ilka

    2009-01-01

    Diatoms are ecologically important algae that acquired their plastids by secondary endosymbiosis, resulting in a more complex cell structure and an altered distribution of metabolic pathways when compared with organisms with primary plastids. Diatom plastids are surrounded by 4 membranes; the outermost membrane is continuous with the endoplasmic reticulum. Genome analyses suggest that nucleotide biosynthesis is, in contrast to higher plants, not located in the plastid, but in the cytosol. As a consequence, nucleotides have to be imported into the organelle. However, the mechanism of nucleotide entry into the complex plastid is unknown. We identified a high number of putative nucleotide transporters (NTTs) in the diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum and characterized the first 2 isoforms (NTT1 and NTT2). GFP-based localization studies revealed that both investigated NTTs are targeted to the plastid membranes, and that NTT1 most likely enters the innermost plastid envelope via the stroma. Heterologously expressed NTT1 acts as a proton-dependent adenine nucleotide importer, whereas NTT2 facilitates the counter exchange of (deoxy-)nucleoside triphosphates. Therefore, these transporters functionally resemble NTTs from obligate intracellular bacteria with an impaired nucleotide metabolism rather than ATP/ADP exchanging NTTs from primary plastids. We suggest that diatoms harbor a specifically-adapted nucleotide transport system and that NTTs are the key players in nucleotide supply to the complex plastid. PMID:19221027

  17. Effect of dissociation on thermodynamic properties of pure diatomic gases

    NASA Technical Reports Server (NTRS)

    Woolley, Harold W

    1955-01-01

    A graphical method is described by which the enthalpy, entropy, and compressibility factor for the equilibrium mixture of atoms and diatomic molecules for pure gaseous elements may be obtained and shown for any dissociating element for which the necessary data exist. Results are given for hydrogen, oxygen, and nitrogen. The effect of dissociation on the heat capacity is discussed briefly.

  18. FLUORESCENCE QUENCHING AND THE DIADINOXANTHIN CYCLE IN A MARINE DIATOM

    EPA Science Inventory

    The diadinoxanthin cycle (DD-cycle) in chromophyta algae involves the interconversion of two carotenoids, diadinoxanthin (DD) and diatoxanthin (DT). e investigated the kinetics of light-induced DD-cycling in the marine diatom Phaeodactylum triconutum and its role in dissipating e...

  19. Continental erosion and the Cenozoic rise of marine diatoms

    PubMed Central

    Cermeño, Pedro; Falkowski, Paul G.; Romero, Oscar E.; Schaller, Morgan F.; Vallina, Sergio M.

    2015-01-01

    Marine diatoms are silica-precipitating microalgae that account for over half of organic carbon burial in marine sediments and thus they play a key role in the global carbon cycle. Their evolutionary expansion during the Cenozoic era (66 Ma to present) has been associated with a superior competitive ability for silicic acid relative to other siliceous plankton such as radiolarians, which evolved by reducing the weight of their silica test. Here we use a mathematical model in which diatoms and radiolarians compete for silicic acid to show that the observed reduction in the weight of radiolarian tests is insufficient to explain the rise of diatoms. Using the lithium isotope record of seawater as a proxy of silicate rock weathering and erosion, we calculate changes in the input flux of silicic acid to the oceans. Our results indicate that the long-term massive erosion of continental silicates was critical to the subsequent success of diatoms in marine ecosystems over the last 40 My and suggest an increase in the strength and efficiency of the oceanic biological pump over this period. PMID:25831504

  20. Biopattern transfer using diatom frustules for fabrication of functional micro/nanostructures

    NASA Astrophysics Data System (ADS)

    Jiang, Yonggang; Fu, Jianchao; Pan, Junfeng; An, Zhonglie; Cai, Jun; Zhang, Deyuan

    2015-01-01

    Diatom frustules exhibit various sophisticated shapes with highly ordered hierarchical porous nanostructures, which are promising for applications in the biomimetic fabrication of nanostructured materials. We propose a universal biopattern transfer process for the fabrication of functional micro/nanostructures using diatom frustules as the biotemplates. Porous silicon microcylinders with a thickness of 20 ?m are fabricated by deep reactive ion etching of a silicon substrate, which is covered by a layer of diatom frustules. With a similar process, a fast atom beam technique is used to etch the silicon substrate and silicon nanolattices are obtained. By depositing a thin layer of gold film on the diatom bonded silicon substrate, followed by releasing the diatom frustules by diluted HF, gold nanodisks with a thickness of 30 nm are successfully fabricated. The nanodisk array arranges in diamond or radial patterns, replicating the nanostructure of diatom frustules. In addition, a parylene nanodot array is also demonstrated using this diatom-based biopattern transfer process.

  1. Supramolecular organization of fucoxanthin-chlorophyll proteins in centric and pennate diatoms.

    PubMed

    Gardian, Zdenko; Litvn, Radek; Bna, David; Vcha, Frantiek

    2014-07-01

    Fucoxanthin-chlorophyll proteins (FCP) are the major light-harvesting proteins of diatom algae, a major contributor to marine carbon fixation. FCP complexes from representatives of centric (Cyclotella meneghiniana) and pennate (Phaeodactylum tricornutum) diatoms were prepared by sucrose gradient centrifugation and studied by means of electron microscopy followed by single particle analysis. The oligomeric FCP from a centric diatom were observed to take the form of unusual chain-like or circular shapes, a very unique supramolecular assembly for such antennas. The existence of the often disputed oligomeric form of FCP in pennate diatoms has been confirmed. Contrary to the centric diatom FCP, pennate diatom FCP oligomers are very similar to oligomeric antennas from related heterokont (Stramenopila) algae. Evolutionary aspects of the presence of novel light-harvesting protein arrangement in centric diatoms are discussed. PMID:24715699

  2. Tape cast bioactive metal-ceramic laminates for structural application

    NASA Astrophysics Data System (ADS)

    Clupper, Daniel Christopher

    Bioglass 45S5, is a silica based glass which is able to rapidly form strong bonds with bone and soft tissue in vivo. It is used clinically to replace damaged ear ossicles and in dental surgery to help maintain the structural integrity of the jaw bone. The goal of the research was to demonstrate that Bioglass can be toughened by lamination with metallic layers while maintaining bioactivity. Improvement of the mechanical properties of Bioglass 45SS would allow for additional clinical applications, such as fracture fixation plates, or vertebral spacers. Bioglass 45S5 was tape cast and laminated with clinically relevant metals (316L, stainless steel and titanium) as well as copper in an effort to demonstrate that the effective toughness, or area under the load-deflection diagram can be increased significantly through ductile layer lamination. The average strength of monolithic tape cast sintered Bioglass was as high as 150 MPa and the toughness measured approximately 1.0 MPa m1/2. Copper-Bioglass laminates clearly demonstrated the toughening effect of metal layers on tape cast sintered Bioglass 45S5. Steel-Bioglass laminates, although less tough than the copper-Bioglass laminates, showed higher strengths. In vitro bioactivity tests of both titanium and steel Bioglass laminates showed the formation of mature and thick hydroxyapatite layers after 24 hours in Tris buffer solution. Under the standard test conditions, the bioactivity of monolithic tape cast sintered Bioglass increased with increasing sintering temperature. For samples sintered at 1000°C, thick crystalline layers of hydroxyapatite formed within 24 hours in Tris buffer solution. The bioactivity of these samples approached that of amorphous bulk Bioglass. Samples processed at 800°C were able to form thick crystalline hydroxyapatite layer after 24 hours when the test solution volume was increased by eight times.

  3. Fossilized diatoms in meteorites from recent falls in Sri Lanka

    NASA Astrophysics Data System (ADS)

    Hoover, Richard B.; Wallis, Jamie; Wickramarathne, Keerthi; Samaranayake, Anil; Williams, George; Jerman, Gregory; Wallis, D. H.; Wickramasinghe, N. C.

    2013-09-01

    On December 29, 2012, a bright yellow and green fireball was observed to disintegrate over the Polonnaruwa District of North Central, Sri Lanka. Many low density, black stones were recovered soon after the observed fall from rice paddy fields near the villages of Aralaganwila and Dimbulagala. These stones were initially studied by optical microscopy methods at the Medical Research Institute in Colombo, Sri Lanka. Soon thereafter, samples were sent to the UK and to the United States. More extensive Field Emission Scanning Electron Microscopy studies were then carried out at Cardiff University and the NASA/Marshall Space Flight Center. The physico-chemical properties, elemental abundances, mineralogy and stable isotope data clearly indicate that these stones are non-terrestrial. Freshly fractured interior surfaces of the black stones have also been observed to contain the remains of fossilized diatom. Many of the diatom frustules are clearly embedded in the meteorite rock matrix and exhibit nitrogen levels below the EDX detection limits. Some of the fossil diatoms are araphid marine pennates and planktonic forms that are inconsistent with conditions associated with rice paddy fields. These observations indicate the fossilized diatoms are indigenous to the meteorites rather than post-arrival biological contaminants. The carbon content and mineralogy suggests that these stones may represent a previously ungrouped clan of carbonaceous meteorites. The extremely low density (~0.6) of the stones and their observed mineralogy was inconsistent with known terrestrial rocks (e.g., pumice, diatomite and fulgurites). The minerals detected suggest that the parent body of the Polonnaruwa stones may have been the nucleus of a comet. These observations are interpreted as supporting the Hoyle-Wickramasinghe Panspermia hypothesis and the hypothesis that diatoms and other microorganisms might be capable of living and growing in water ice and brines in comets.

  4. Diatom Proteomics Reveals Unique Acclimation Strategies to Mitigate Fe Limitation

    PubMed Central

    Nunn, Brook L.; Faux, Jessica F.; Hippmann, Anna A.; Maldonado, Maria T.; Harvey, H. Rodger; Goodlett, David R.; Boyd, Philip W.; Strzepek, Robert F.

    2013-01-01

    Phytoplankton growth rates are limited by the supply of iron (Fe) in approximately one third of the open ocean, with major implications for carbon dioxide sequestration and carbon (C) biogeochemistry. To date, understanding how alteration of Fe supply changes phytoplankton physiology has focused on traditional metrics such as growth rate, elemental composition, and biophysical measurements such as photosynthetic competence (Fv/Fm). Researchers have subsequently employed transcriptomics to probe relationships between changes in Fe supply and phytoplankton physiology. Recently, studies have investigated longer-term (i.e. following acclimation) responses of phytoplankton to various Fe conditions. In the present study, the coastal diatom, Thalassiosira pseudonana, was acclimated (10 generations) to either low or high Fe conditions, i.e. Fe-limiting and Fe-replete. Quantitative proteomics and a newly developed proteomic profiling technique that identifies low abundance proteins were employed to examine the full complement of expressed proteins and consequently the metabolic pathways utilized by the diatom under the two Fe conditions. A total of 1850 proteins were confidently identified, nearly tripling previous identifications made from differential expression in diatoms. Given sufficient time to acclimate to Fe limitation, T. pseudonana up-regulates proteins involved in pathways associated with intracellular protein recycling, thereby decreasing dependence on extracellular nitrogen (N), C and Fe. The relative increase in the abundance of photorespiration and pentose phosphate pathway proteins reveal novel metabolic shifts, which create substrates that could support other well-established physiological responses, such as heavily silicified frustules observed for Fe-limited diatoms. Here, we discovered that proteins and hence pathways observed to be down-regulated in short-term Fe starvation studies are constitutively expressed when T. pseudonana is acclimated (i.e., nitrate and nitrite transporters, Photosystem II and Photosystem I complexes). Acclimation of the diatom to the desired Fe conditions and the comprehensive proteomic approach provides a more robust interpretation of this dynamic proteome than previous studies. PMID:24146769

  5. Genome Properties of the Diatom Phaeodactylum tricornutum[w

    PubMed Central

    Scala, Simona; Carels, Nicolas; Falciatore, Angela; Chiusano, Maria Luisa; Bowler, Chris

    2002-01-01

    Diatoms are a ubiquitous class of microalgae of extreme importance for global primary productivity and for the biogeochemical cycling of minerals such as silica. However, very little is known about diatom cell biology or about their genome structure. For diatom researchers to take advantage of genomics and post-genomics technologies, it is necessary to establish a model diatom species. Phaeodactylum tricornutum is an obvious candidate because of its ease of culture and because it can be genetically transformed. Therefore, we have examined its genome composition by the generation of approximately 1,000 expressed sequence tags. Although more than 60% of the sequences could not be unequivocally identified by similarity to sequences in the databases, approximately 20% had high similarity with a range of genes defined functionally at the protein level. It is interesting that many of these sequences are more similar to animal rather than plant counterparts. Base composition at each codon position and GC content of the genome were compared with Arabidopsis, maize (Zea mays), and Chlamydomonas reinhardtii. It was found that distribution of GC within the coding sequences is as homogeneous in P. tricornutum as in Arabidopsis, but with a slightly higher GC content. Furthermore, we present evidence that the P. tricornutum genome is likely to be small (less than 20 Mb). Therefore, this combined information supports the development of this species as a model system for molecular-based studies of diatom biology. The nucleotide sequence data reported has been deposited in GenBank Nucleotide Sequence Database (dbEST section) under accession nos. BI306757 through BI307753. PMID:12114555

  6. Adiabatic principles in atom-diatom collisional energy transfer

    SciTech Connect

    Hovingh, W.J.

    1993-01-01

    This work describes the application of numerical methods to the solution of the time dependent Schroedinger equation for non-reactive atom-diatom collisions in which only one of the degrees of freedom has been removed. The basic method involves expanding the wave function in a basis set in two of the diatomic coordinates in a body-fixed frame (with respect to the triatomic complex) and defining the coefficients in that expansion as functions on a grid in the collision coordinate. The wave function is then propagated in time using a split operator method. The bulk of this work is devoted to the application of this formalism to the study of internal rotational predissociation in NeHF, in which quasibound states of the triatom predissociate through the transfer of energy from rotation of the diatom into translational energy in the atom-diatom separation coordinate. The author analyzes the computed time dependent wave functions to calculate the lifetimes for several quasibound states; these are in agreement with time independent quantum calculations using the same potential. Moreover, the time dependent behavior of the wave functions themselves sheds light on the dynamics of the predissociation processes. Finally, the partial cross sections of the products in those processes is determined with multiple exit channels. These show strong selectivity in the orbital angular momentum of the outgoing fragments, which the author explains with an adiabatic channel interpretation of the wave function's dynamics. The author also suggests that the same formalism might profitably be used to investigate the quantum dynamics of [open quotes]quasiresonant vibration-rotation transfer[close quotes], in which remarkably strong propensity rules in certain inelastic atom-diatom collision arise from classical adiabatic invariance theory.

  7. Understanding amine catalyzed silica polymerization : diatoms as bioarchitects.

    SciTech Connect

    Spoerke, Erik David; Aubry, Sylvie; Lane, Pamela; Robinson, David B; Bauer, Christina A.; Zendejas, Frank; Tran, Huu; Lane, Todd W.; Simmons, Blake Alexander

    2007-10-01

    Current state-of-the-art biomimetic methodologies employed worldwide for the realization of self-assembled nanomaterials are adequate for certain unique applications, but a major breakthrough is needed if these nanomaterials are to obtain their true promise and potential. These routes typically utilize a 'top-down' approach in terms of controlling the nucleation, growth, and deposition of structured nanomaterials. Most of these techniques are inherently limited to primarily 2D and simple 3D structures, and are therefore limited in their ultimate functionality and field of use. Zeolites, one of the best-known and understood synthetic silica structures, typically possess highly ordered silica domains over very small length scales. The development of truly organized and hierarchical zeolites over several length scales remains an intense area of research world wide. Zeolites typically require high-temperature and complex synthesis routes that negatively impact certain economic parameters and, therefore, the ultimate utility of these materials. Nonetheless, zeolite usage is in the tons per year worldwide and is quickly becoming ubiquitous in its applications. In addition to these more mature aspects of current practices in materials science, one of the most promising fields of nanotechnology lies in the advent and control of biologically self-assembled materials, especially those involved with silica and other ceramics such as hydroxyapatite. Nature has derived, through billions of years of evolutionary steps, numerous methods by which fault-tolerant and mechanically robust structures can be created with exquisite control and precision at relatively low temperature ranges and pressures. Diatoms are one of the best known examples that exhibit this degree of structure and control known that is involved with the biomineralization of silica. Diatoms are eukaryotic algae that are ubiquitous in marine and freshwater environments. They are a dominant form of phytoplankton critical to global carbon fixation. The silicified cell wall of the diatom is called the frustule, and the intricate silica structure characteristic of a given species is known as the valve. There are two general classes of diatoms, based on their overall morphologies, the pennate and centric. Diatoms achieve their silicified structures in exact fashion through genetically inspired design rules coupled with precisely directed biochemistry occurring at temperatures ranging from a few degrees Celsius (polar species) to temperatures just over room temperature (tropical species). Different species of diatoms produce markedly different structures. To start with, there are two basic types of frustule macromorphologies: pennate diatoms display bilateral symmetry and centric diatoms show radial symmetry. There are thousands of permutations of these two basic forms and the micromorphology of the valve can be quite complex with all types of pore arrangements and morphologies (Figure 1.1). The detailed morphology of the cell wall of a given diatom species is reproduced with exactness, because the process is genetically encoded. Three types of cell wall proteins have been identified in diatoms; the frustulins, pleuralins, and silaffins. Frustulins are cell wall proteins that form an organic coat to protect the silica structures from dissolution into the aqueous environment. Pleuralins are associated with a specific subcomponent of the frustule during cell division, and play a role in hypotheca-epitheca development. Silaffins from Cylindrotheca fusiformis are short chain-length peptides that play a direct role in the silica polymerization process, and possess unique biochemical post-translation functionalization. Larger proteins with silaffin activity have recently been described in Thalassiosira pseudonana. Frustulins and pleuralins play no role in silica polymerization or structure formation in diatoms, whereas the silaffins are one of the primary polymerization determinants. In addition to the silaffins, a class of long-chain polyamines associated with diatom silica has been identified, and shown to also be involved in the silica polymerization process. The silaffins and polyamines are likely to be the two major determinants of silica polymerization in diatoms. Their involvement in the formation of higher order structure is unclear; there have been suggestions that they self-assemble in various combinations to form the final frustule structure but these are highly speculative as there is no substantial data to support this. It is clear from a long history of electron microscopic observations that a major determinant of silica structure in diatoms is generated by growth and molding of the silica deposition vesicle (SDV), the specialized intracellular compartment were the frustule is made. Diatoms are the focus of research activity on several fronts, including the processes by which their distinct silica frustules are formed.

  8. The structure and diversity of freshwater diatom assemblages from Franz Josef Land Archipelago: a northern outpost for freshwater diatoms.

    PubMed

    Pla-Rabs, Sergi; Hamilton, Paul B; Ballesteros, Enric; Gavrilo, Maria; Friedlander, Alan M; Sala, Enric

    2016-01-01

    We examined diatom assemblages from 18 stream and pond samples in the Franz Josef Land Archipelago (FJL), the most northern land of Eurasia. More than 216 taxa were observed, revealing a rich circumpolar diatom flora, including many undescribed taxa. Widely distributed taxa were the most abundant by cell densities, while circumpolar taxa were the most species rich. Stream and pond habitats hosted different assemblages, and varied along a pH gradient. Diatoma tenuis was the most abundant and ubiquitous taxon. However, several circumpolar taxa such as Chamaepinnularia gandrupii, Cymbella botellus, Psammothidium sp. and Humidophila laevissima were also found in relatively high abundances. Aerophilic taxa were an important component of FJL diatom assemblages (Humidophila spp., Caloneis spp. and Pinnularia spp.), reflecting the large and extreme seasonal changes in Arctic conditions. We predict a decrease in the abundance of circumpolar taxa, an increase in local (?-) freshwater diatom diversity, but a decrease in regional diversity (circumpolar homogenization) as a result of current warming trends and to a lesser extent the increasing human footprint in the region. PMID:26925329

  9. The structure and diversity of freshwater diatom assemblages from Franz Josef Land Archipelago: a northern outpost for freshwater diatoms

    PubMed Central

    Hamilton, Paul B.; Ballesteros, Enric; Gavrilo, Maria; Friedlander, Alan M.; Sala, Enric

    2016-01-01

    We examined diatom assemblages from 18 stream and pond samples in the Franz Josef Land Archipelago (FJL), the most northern land of Eurasia. More than 216 taxa were observed, revealing a rich circumpolar diatom flora, including many undescribed taxa. Widely distributed taxa were the most abundant by cell densities, while circumpolar taxa were the most species rich. Stream and pond habitats hosted different assemblages, and varied along a pH gradient. Diatoma tenuis was the most abundant and ubiquitous taxon. However, several circumpolar taxa such as Chamaepinnularia gandrupii, Cymbella botellus, Psammothidium sp. and Humidophila laevissima were also found in relatively high abundances. Aerophilic taxa were an important component of FJL diatom assemblages (Humidophila spp., Caloneis spp. and Pinnularia spp.), reflecting the large and extreme seasonal changes in Arctic conditions. We predict a decrease in the abundance of circumpolar taxa, an increase in local (α-) freshwater diatom diversity, but a decrease in regional diversity (circumpolar homogenization) as a result of current warming trends and to a lesser extent the increasing human footprint in the region. PMID:26925329

  10. [Animal welfare in prevention and therapy of laminitis].

    PubMed

    Winkelsett, S; Vervuert, I

    2008-03-01

    Laminitis is a systemic disease which is manifested as a non infectious condition in the foot. The management of feeding and housing conditions is necessary to treat the endocrinological and metabolic disturbances of laminitic horses. The Equine Metabolic Syndrome (EMS) is predisposing for developing laminitis, and it is characterised by obesity, insulin resistance, hypertension and dyslipidaemia. A genetical predisposition is supposed and EMS is accompanied by a lack of exercise and inadequate energy intake. Laboratory examinations are of great importance for diagnosis. Analyses of insulin, glucose and ACTH are of interest. Several approaches to treat laminitis are available, including pharmacological and orthopaedic strategies as well as the management of the feeding and housing conditions. However, the prophylaxis to prevent laminitis has to be emphasised. Predisposed horses should be detected and adequately treated; especially weight reduction in obese horses is in the focus of interest. Horses in the acute stage of laminitis have to be stabled. Furthermore redistributing weight from the most stressed wall is necessary to prevent pain and to minimise laminar damage and displacement of the distal phalanx. In cases of displacement of the distal phalanx a close communication between the veterinarian and the authorised farrier is necessary, in these cases treatment should be supported by x-ray diagnosis. Horses have to be treated with NSAISs to ensure a proper therapy to consider animal welfare. Horses have to be fed with hay and supplemented with minerals and vitamins. Feeding exclusively straw and feed restriction has to be avoided. PMID:18444467

  11. Analytical study for deformability of laminated sheet metal.

    PubMed

    Serror, Mohammed H

    2013-01-01

    While a freestanding high-strength sheet metal subject to tension will rupture at a small strain, it is anticipated that lamination with a ductile sheet metal will retard this instability to an extent that depends on the relative thickness, the relative stiffness, and the hardening exponent of the ductile sheet. This paper presents an analytical study for the deformability of such laminate within the context of necking instability. Laminates of high-strength sheet metal and ductile low-strength sheet metal are studied assuming: (1) sheets are fully bonded; and (2) metals obey the power law material model. The effect of hardening exponent, volume fraction and relative stiffness of the ductile component has been studied. In addition, stability of both uniform and nonuniform deformations has been investigated under plane strain condition. The results have shown the retardation of the high-strength layer instability by lamination with the ductile layer. This has been achieved through controlling the aforementioned key parameters of the ductile component, while the laminate exhibits marked enhancement in strength-ductility combination that is essential for metal forming applications. PMID:25685405

  12. Tension fatigue analysis and life prediction for composite laminates

    NASA Technical Reports Server (NTRS)

    Obrien, T. K.; Rigamonti, M.; Zanotti, C.

    1988-01-01

    A tension fatigue life prediction methodology for composite laminates is presented. Tension fatigue tests were conducted on quasi-isotropic and orthotropic glass epoxy, graphite epoxy, and glass/graphite epoxy hybrid laminates. Edge delamination onset data were used to generate plots of strain energy release rate as a function of cycles to delamination onset. These plots were then used along with strain energy release rate analyses of delaminations initiating at matrix cracks to predict local delamination onset. Stiffness loss was measured experimentally to account for the accumulation of matrix cracks and for delamination growth. Fatigue failure was predicted by comparing the increase in global strain resulting from stiffness loss to the decrease in laminate failure strain resulting from delaminations forming at matrix cracks through the laminate thickness. Good agreement between measured and predicted lives indicated that the through-thickness damage accumulation model can accurately describe fatigue failure for laminates where the delamination onset behavior in fatigue is well characterized, and stiffness loss can be monitored in real time to account for damage growth.

  13. Dynamic Stability of Uncertain Laminated Beams Under Subtangential Loads

    NASA Technical Reports Server (NTRS)

    Goyal, Vijay K.; Kapania, Rakesh K.; Adelman, Howard (Technical Monitor); Horta, Lucas (Technical Monitor)

    2002-01-01

    Because of the inherent complexity of fiber-reinforced laminated composites, it can be challenging to manufacture composite structures according to their exact design specifications, resulting in unwanted material and geometric uncertainties. In this research, we focus on the deterministic and probabilistic stability analysis of laminated structures subject to subtangential loading, a combination of conservative and nonconservative tangential loads, using the dynamic criterion. Thus a shear-deformable laminated beam element, including warping effects, is derived to study the deterministic and probabilistic response of laminated beams. This twenty-one degrees of freedom element can be used for solving both static and dynamic problems. In the first-order shear deformable model used here we have employed a more accurate method to obtain the transverse shear correction factor. The dynamic version of the principle of virtual work for laminated composites is expressed in its nondimensional form and the element tangent stiffness and mass matrices are obtained using analytical integration The stability is studied by giving the structure a small disturbance about an equilibrium configuration, and observing if the resulting response remains small. In order to study the dynamic behavior by including uncertainties into the problem, three models were developed: Exact Monte Carlo Simulation, Sensitivity Based Monte Carlo Simulation, and Probabilistic FEA. These methods were integrated into the developed finite element analysis. Also, perturbation and sensitivity analysis have been used to study nonconservative problems, as well as to study the stability analysis, using the dynamic criterion.

  14. Analytical study for deformability of laminated sheet metal

    PubMed Central

    Serror, Mohammed H.

    2012-01-01

    While a freestanding high-strength sheet metal subject to tension will rupture at a small strain, it is anticipated that lamination with a ductile sheet metal will retard this instability to an extent that depends on the relative thickness, the relative stiffness, and the hardening exponent of the ductile sheet. This paper presents an analytical study for the deformability of such laminate within the context of necking instability. Laminates of high-strength sheet metal and ductile low-strength sheet metal are studied assuming: (1) sheets are fully bonded; and (2) metals obey the power law material model. The effect of hardening exponent, volume fraction and relative stiffness of the ductile component has been studied. In addition, stability of both uniform and nonuniform deformations has been investigated under plane strain condition. The results have shown the retardation of the high-strength layer instability by lamination with the ductile layer. This has been achieved through controlling the aforementioned key parameters of the ductile component, while the laminate exhibits marked enhancement in strengthductility combination that is essential for metal forming applications. PMID:25685405

  15. Fracture behavior of unidirectional boron/aluminum composite laminates

    NASA Technical Reports Server (NTRS)

    Goree, J. G.; Jones, W. F.

    1983-01-01

    An experiment was conducted to verify the results of mathematical models which predict the stresses and displacements of fibers and the amount of damage growth in a center-notched lamina as a function of the applied remote stress and the matrix and fiber material properties. A brittle lacquer coating was used to detect the yielding in the matrix while X-ray techniques were used to determine the number of broken fibers in the laminate. The notched strengths and the amounts of damage found in the specimens agree well with those predicted by the mathematical model. It is shown that the amount of damage and the crack opening displacement does not depend strongly on the number of plies in the laminate for a given notch width. By heat-treating certain laminates to increase the yield stress of the alumina matrix, the effect of different matrix properties on the fracture behavior was investigated. The stronger matrix is shown to weaken the notched laminate by decreasing the amount of matrix damage, thereby making the laminate more notch sensitive.

  16. Tungsten foil laminate for structural divertor applications - Basics and outlook

    NASA Astrophysics Data System (ADS)

    Reiser, Jens; Rieth, Michael; Dafferner, Bernhard; Hoffmann, Andreas

    2012-04-01

    It has been attempted for several years to synthesize a tungsten material with a low brittle-to-ductile transition temperature and a high fracture toughness that can be used for structural parts. In this work, we show how to realize the ductilization of tungsten: by synthesizing a laminate made of tungsten foil. This paper shows that tungsten foil is ductile in a tensile test performed at room temperature. The idea now is to expand the ductile material properties of the tungsten foil to a bulk, by assembling several layers of this ductile tungsten foil. By doing this, a tungsten laminate can be synthesized. This laminate is characterized by a Charpy impact test and the results are compared to tungsten plate material. The results of the tungsten laminate are excellent: nearly 2 J of energy absorption at room temperature, 5 J at 100 C and 10 J at 300 C (measured by KLST standard). Even more overwhelming are the results obtained from a tungsten laminate synthesized with recrystallized tungsten foil (annealed for 1 h/1800 C). Here, the brittle ductile transition is at 500 C, which is an improvement of at least 500 C compared to recrystallized plate material (1 h/2000 C). As a last step we present the first ductile tungsten pipe that can be used for structural applications: a tungsten pipe made of tungsten foil.

  17. Bending Boundary Layers in Laminated-Composite Circular Cylindrical Shells

    NASA Technical Reports Server (NTRS)

    Nemeth, Michael P.; Smeltzer, Stanley S., III

    2000-01-01

    A study of the attenuation of bending boundary layers in balanced and unbalanced, symmetrically and unsymmetrically laminated cylindrical shells is presented for nine contemporary material systems. The analysis is based on the linear Sanders-Koiter shell equations and specializations to the Love-Kirchhoff shell equations and Donnell's equations are included. Two nondimensional parameters are identified that characterize the effects of laminate orthotropy and anisotropy on the bending boundary-layer decay length in a very general manner. A substantial number of structural design technology results are presented for a wide range of laminated-composite cylinders. For all laminates considered, the results show that the differences between results obtained with the Sanders-Koiter shell equations, the Love-Kirchhoff shell equations, and Donnell's equations are negligible. The results also show that the effect of anisotropy in the form of coupling between pure bending and twisting has a negligible effect on the size of the bending boundary-layer decay length of the balanced, symmetrically laminated cylinders considered. Moreover, the results show that coupling between the various types of shell anisotropies has a negligible effect on the calculation of the bending boundary-layer decay length in most cases. The results also show that, in some cases, neglecting the shell anisotropy results in underestimating the bending boundary-layer decay length and, in other cases, results in an overestimation.

  18. Using diatom indices for water quality assessment in a subtropical river, China.

    PubMed

    Tan, Xiang; Sheldon, Fran; Bunn, Stuart E; Zhang, Quanfa

    2013-06-01

    Diatoms have been regularly used as bioindicators to assess water quality of surface waters. However, diatom-based indices developed for a specific geographic region may not be appropriate elsewhere. We sampled benthic diatom assemblages in the upper Han River, a subtropical river in China, to evaluate applicability of 14 diatom-based indices used worldwide for water quality assessment. A total of 194 taxa from 31 genera were identified in the dry season and 139 taxa from 23 genera in the wet season. During the dry season, significant relationships were found for all but one of the diatom-based indices (Index Diatom Artois-Picardie) with one or more physical and chemical variables including nutrients and ion concentrations in river waters. The Biological Diatom Index (IBD) and diatom-based eutrophication/pollution index (EPI-D) were strongly related to trophic status and ionic content, while Watanabe's Index was related to organic pollution and conductivity. Yet, the diatom indices showed weak relationships with physical and chemical variables during the wet season. It suggests that diatom-based indices developed in Europe can be applied with confidence as bioindicators of water quality in subtropical rivers of China, at least during base-flow conditions. PMID:23247517

  19. Using benthic diatom assemblages to assess human impacts on streams across a rural to urban gradient.

    PubMed

    Yang, Ying; Cao, Jin-Xiang; Pei, Guo-Feng; Liu, Guo-Xing

    2015-11-01

    Benthic diatom assemblages on the natural substrata were investigated at 21 sites of the Ganhe River watershed (China) once per season and in addition, early spring in 2013. A total of 487 diatom taxa from 36 genera were identified during five investigations. The assemblages were dominated by Achnanthidium minutissimum (Ktzing) Czarnecki and Cocconeis placentula in the rural reach, whereas Navicula, Nitzschia, and Gomphonema species were characteristic of urbanized sites. Our results suggest that biodiversity was positively related to high nutrient levels and strongly negatively related to diatom-based indices. The periphyton biomass (expressed as chlorophyll a and ash-free dry mass) was not related to water quality. Canonical correspondence analysis (CCA) showed that the nutrient concentration gradient was the most important factor that affected the diatom assemblage composition and species distribution. The diatom-based indices (specific pollution sensitivity index (IPS), biological diatom index (IBD), and trophic diatom index (TDI)) were significantly positively correlated with water quality and are adequate for use in China. Slight changes in the biodiversity and diatom-based indices followed a temporal pattern. The species composition was less related to the season or hydrological characteristics of the river but more strongly related to differences in the trophic status. In this region, urbanization masked the impact of rural land use on benthic diatoms. The research will expand the understanding of using benthic diatom assemblages for water quality monitoring in urban streams and improve watershed-scale management and conservation efforts in the Ganhe River, China. PMID:26174985

  20. Growth and release of extracellular organic compounds by benthic diatoms depend on interactions with bacteria.

    PubMed

    Bruckner, Christian G; Rehm, Charlotte; Grossart, Hans-Peter; Kroth, Peter G

    2011-04-01

    Phototrophic epilithic biofilms harbour a distinct assemblage of heterotrophic bacteria, cyanobacteria and photoautotrophic algae. Secretion of extracellular polymeric substances (EPS) by these organisms and the physicochemical properties of the EPS are important factors for the development of the biofilms. We have isolated representative diatom and bacteria strains from epilithic biofilms of Lake Constance. By pairwise co-cultivating these strains we found that diatom growth and EPS secretion by diatoms may depend on the presence of individual bacteria. Similar results were obtained after addition of spent bacterial medium to diatom cultures, suggesting that soluble substances from bacteria have an impact on diatom physiology. While searching for putative bacterial signal substances, we found that concentrations of various dissolved free amino acids (DFAA) within the diatom cultures changed drastically during co-cultivation with bacteria. Further, the secretion of extracellular carbohydrates and proteins can be influenced by bacteria or their extracellular substances. We have performed mass spectrometric peptide mapping to identify proteins which are secreted when co-cultivating the diatom Phaeodactylum tricornutum Bohlin and Escherichia coli. The identified proteins are possibly involved in signalling, extracellular carbohydrate modification and uptake, protein and amino acid modification, and cell/cell aggregation of diatom and bacteria strains. Our data indicate that diatom-bacteria biofilms might be regulated by a complex network of chemical factors involving EPS, amino acid monomers and other substances. Thus interactions with bacteria can be considered as one of the main factors driving biofilm formation by benthic diatoms. PMID:21244599