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1

Diatom Ooze: Ooze Clues  

NSDL National Science Digital Library

In this activity, learners will plot the distribution of various oozes using information from sediment maps. When skeletal remains of microscopic organisms make up more than 30% of the sediment, it is called "ooze." During this activity, learners will describe the characteristics of different types of seafloor sediments and oozes, predict the distribution of calcareous and siliceous oozes and compare and discuss locations of sediments and oozes.

Lawrence, Lisa A.

2013-01-04

2

Seasonal and subseasonal climate changes recorded in laminated diatom ooze sediments, Adélie Land, East Antarctica  

Microsoft Academic Search

A 40 m long sediment core covering the 1000–9600 years BP period was retrieved from the Dumont d'Urville Trough off Adélie Land, East Antarctica, during the MD 130–Images X-CADO cruise. This sedimentary sequence allows the documentation of changes in climate seasonality during the Holocene. Here we show preliminary results of diatom communities, lithic grain distribution and titanium content measured on

D. Denis; X. Crosta; S. Zaragosi; O. Romero; B. Martin; V. Mas

2006-01-01

3

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

USGS Publications Warehouse

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.

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

1997-01-01

4

Diatomaceous oozes of the Middle Caspian Sea  

NASA Astrophysics Data System (ADS)

Ten cores taken by a gravity corer from an area 5 × 5 km in size at the foot of the western slope of the Derbent Basin recovered uniform sections composed of variegated clotted diatomaceous oozes and soft gray clays with hydrotroilite-enriched spots, lenses, and laminae, the abundance of which increases downward. The diatom assemblages indicate a strongly freshened basin, which was replaced in the Holocene (Novocaspian time) by the brackish-water and then present-day saline sea. The grain-size composition of the sediments was determined by the gravitational deposition of suspended particles and by the near-bottom currents. The latter likely promoted the concentration of diatom frustules and accumulation of diatomaceous oozes.

Sval'Nov, V. N.; Kazarina, G. Kh.

2008-08-01

5

Experimental Erosion of Calcareous Ooze  

Microsoft Academic Search

Flume experiments on the erosion of abyssal calcareous ooze in shallow uniform flows of sea water show that erosion velocities range from 7-10 cm\\/sec soon after rapid deposition of the bed to 15-20 cm\\/sec after a few tens of hours. Continuing erosion produces shallow irregular longstream linearions but no sediment ripples. On the assumption of a hydrodynamically smooth boundary in

J. B. SOUTI-IARD; R. A. Young; C. D. Hollister

1971-01-01

6

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

USGS Publications Warehouse

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.

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

1994-01-01

7

Laminates  

NASA Astrophysics Data System (ADS)

The use of phenolic resin for the impregnation of a carrier material such as paper or fabric based on either organic or inorganic fibers was and still is one of the most important application areas for liquid phenolic resins. Substrates like paper, cotton, or glass fabric impregnated with phenolic resins are used as core layers for decorative and technical laminates and for many other different industrial applications. Nowadays, phenolic resins for decorative laminates used for furniture, flooring, or in the construction and transportation industry have gained significant market share. The Laminates chapter mainly describes the manufacture of decorative laminates especially the impregnation and pressing process with special emphasis to new technological developments and recent trends. Moreover, the different types of laminates are introduced, combined with some brief comments as they relate to the market for decorative surfaces.

Lepedat, Karin; Wagner, Robert; Lang, Jürgen

8

Occurrence of thick Ethmodiscus oozes associated with a terminal Mid-Pleistocene Transition event in the oligotrophic subtropical South Atlantic  

Microsoft Academic Search

Within generally calcareous sediment sequences, layers of variable thickness of the giant diatom Ethmodiscus were found in five cores recovered in the Subtropical South Atlantic between 23° and 33°S from both sides of the Mid-Atlantic Ridge. Two types of oozes occur: (almost) monospecific layers of Ethmodiscus and layers dominated by Ethmodiscus, with several accompanying tropical\\/subtropical, oligotrophic-water diatoms. The two thickest

Oscar Romero; Frank Schmieder

2006-01-01

9

Diatoms (Class Bacillariophyceae) and geochemistry from annually laminated mid-Holocene sediments, west coast Canada: insights into abrupt climate change in the past  

NASA Astrophysics Data System (ADS)

A 115-year record of annually laminated sediments from Effingham Inlet, a small anoxic fjord on the west coast of Vancouver Island, British Columbia (49?N, 125?W), was analyzed for diatoms (species and abundances) and geochemistry (C and N isotopes, organic C and trace elements Ag, Cd, Re and Mo) from a piston core. The sediments were radiocarbon dated at approx. 4200-4400 years before present (yr BP) and show diatom enriched varves in the lower 70 years, with a sudden transition to diatom impoverished varves above. In the lower section, varves are thick (2-5 mm) and consist of well-defined Thalassiosira-Skeletonema-Chaetoceros spring bloom successions. Diatom concentrations average at 787 ± 733 million valves/g of dry sediment, del 15N at 7.0 ± 0.5 per mil, and organic C at 5.2 ± 0.5 wt. %. In the upper section, the varves are thinner (1-2 mm), do not clearly show the seasonal diatom succession, and contain increased terrigenous detritus. Diatom concentrations average at 388 ± 202 million valves/g with an increased relative abundance of benthic and freshwater taxa, del 15N at 7.3 ± 0.6 per mil and organic C at 5.7 ± 0.5 wt. %. Values of del 13C for both sections are similar, averaging at -24.0 ± 0.5 per mil. The trace element concentrations are quite variable throughout the section. However, several thin (<1 cm) nonlaminated intervals show decreased diatom abundances with concomitant increases in trace element concentrations, suggesting short-lived changes in surface productivity, upwelling and nutrient delivery, and/or anoxic conditions. The abrupt transition from diatom-rich to diatom-poor varves could reflect a shift in dominance of the North Pacific High and Aleutian Low atmospheric pressure systems over the northeast Pacific Ocean, not unlike the well-documented 1976/1977 climate regime shift which showed a change in upwelling and nutrient delivery. A transition between warm and sunny climates to cooler and wetter regimes at around 4000 yr BP has been noted in previous paleoenvironmental studies from British Columbia and the northern hemisphere in general. The Effingham Inlet sediment record data will also be compared with modern sediment trap data from the inlet.

Chang, A.; Pedersen, T. F.

2009-04-01

10

Experimental formation of chalk from calcareous ooze. Technical progress report  

SciTech Connect

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)

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

1981-02-15

11

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

NASA Astrophysics Data System (ADS)

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.

Betzler, Christian; Lüdmann, Thomas; Hübscher, Christian; Fürstenau, Jörn

2013-05-01

12

Invertebrate lamins  

SciTech Connect

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.

Melcer, Shai [Department of Genetics, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem 91904 (Israel); Gruenbaum, Yosef [Department of Genetics, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem 91904 (Israel)]. E-mail: gru@vms.huji.ac.il; Krohne, Georg [Division of Electron Microscopy, Biocenter of the University Am Hubland, D-97074 Wuerzburg (Germany)]. E-mail: krohne@biozentrum.uni-wuerzburg.de

2007-06-10

13

Unsymmetric laminates  

NASA Astrophysics Data System (ADS)

In order to take full advantage of the tailorability of composite materials, the response of unsymmetric composite materials must be understood. To further the understanding of these unique laminates, a finite element program is used to determine the strain energy release rates and stress distributions of unsymmetric laminates subjected to tension and torsion loads and hygroscopic gradients. The (0(4)/45(4))(T) layup is studied with (0(2)/45(2))(s) results presented for a baseline. The laminates are constructed of IM7/977-2 graphite epoxy. Preliminary experimental results are presented for comparison.

Ochoa, Ozden O.; Ross, George R.

14

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)

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.

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

2011-12-01

15

Laminate Stiffnesses and Classical Laminate Theory.  

National Technical Information Service (NTIS)

A method by which the stiffness properties of a combined laminate can be calculated directly from the known stiffnesses of two individually symmetric laminates making up this combined laminate was extended to the general case of stacking an unrestricted n...

J. W. Gunnink

1985-01-01

16

Fate of corrosion products released from stainless steel in marine sediments and seawater. Part 3. Calcareous ooze  

Microsoft Academic Search

The physicochemical forms and partitioning of corrosion products released from stainless steel upon exposure to selected environmental conditions is the subject of this investigation. This report describes the influence of calcareous sediment on the rate of release and fate of corrosion products produced when neutron-activated stainless steel specimens were exposed to a Globigerina ooze taken from the Northeast Pacific Ocean.

1982-01-01

17

Paleolimnological studies of annually-laminated sediments in Loe Pool, Cornwall, U.K  

Microsoft Academic Search

The sediments of Loe Pool, a eutrophic coastal lake in south west England, consist largely of laminated clays and clay-gyttjas. Studies of the diatom microstratigraphy of frozen sediment cores from the Pool indicate that the laminations are annual, and that they contain pairs of light and dark bands formed by seasonal variations in the supply of sediment to the Pool

M. A. Coard; S. M. Cousen; A. H. Cuttler; H. J. Dean; J. A. Dearing; T. I. Eglinton; A. M. Greaves; K. P. Lacey; P. E. O'Sullivan; D. A. Pickering; M. M. Rhead; J. K. Rodwell; H. Simola

1983-01-01

18

Lipid Components of Diatoms.  

National Technical Information Service (NTIS)

The total lipids of five species of marine diatoms and one fresh-water diatom were studied chromatographically and the major components identified. All species contained glycerides, sulfoquinovosyl diglyceride, diglyceride, monogalactosyl diglyceride, pho...

M. Kates B. E. Volcani

1965-01-01

19

Laminating the hippocampus  

Microsoft Academic Search

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

Eckart Förster; Shanting Zhao; Michael Frotscher

2006-01-01

20

Fate of corrosion products released from stainless steel in marine sediments and seawater. Part 3. Calcareous ooze  

SciTech Connect

The physicochemical forms and partitioning of corrosion products released from stainless steel upon exposure to selected environmental conditions is the subject of this investigation. This report describes the influence of calcareous sediment on the rate of release and fate of corrosion products produced when neutron-activated stainless steel specimens were exposed to a Globigerina ooze taken from the Northeast Pacific Ocean. The calcareous ooze used in this study consists largely of planktonic formanifera tests and was found to be about 90% CaCO/sub 3/. The trace metal content of this sediment was typical of average deep-sea carbonate sediments, and the ratios of trace elements to Ti were not remarkably different from a coastal clayey silt or a Northeast Pacific pelagic red clay. Most (>80%) of the trace metals extracted by sequential chemical treatment were associated with reductant-soluble materials, i.e., amorphous Mn and Fe oxides, or were incorporated in the carbonate substrate. Specimens of neutron-activated stainless steel exposed to calcareous ooze suspended in seawater under aerated and non-oxygenated conditions released corrosion products at rates of 1.7 and 4.2 ..mu..g year/sup -1/ cm/sup -2/, respectively. Almost 90% of the corrosion products (/sup 60/Co activity) released under aerated conditions were relatively labile. Of these materials, over 80% were soluble upon treatment with a strong complexing agent, DTPA, indicating that adsorption of corrosion products as cations had been the major mechanism of incorporation into the sediment. In the absence of O/sub 2/, a large fraction (approx. 80%) of the corrosion products were also relatively labile. Larger fractions of the corrosion products were soluble, easily dissolved, or present as carbonates or sulfides under non-oxygenated conditions than they were for the aerated treatment.

Schmidt, R.L.

1982-04-01

21

Carbon acquisition by diatoms  

Microsoft Academic Search

Diatoms are responsible for up to 40% of primary productivity in the ocean, and complete genome sequences are available for\\u000a two species. However, there are very significant gaps in our understanding of how diatoms take up and assimilate inorganic\\u000a C. Diatom plastids originate from secondary endosymbiosis with a red alga and their Form ID Rubisco (ribulose-1,5-bisphosphate\\u000a carboxylase-oxygenase) from horizontal gene

Karen Roberts; Espen Granum; Richard C. Leegood; John A. Raven

2007-01-01

22

Diatoms Without Siliceous Frustules  

Microsoft Academic Search

DIATOM material freshly gathered during February 1946 from Chichester Harbour was identified as Navicula ramosissima (Agardh) Cleve. The organism was arranged in files within a filamentous muco-gelatinous sheath forming frondose colonies up to 10 cm. in length. When the filaments were placed in diluted sea-water, differences in osmotic pressure caused the diatom cells to be extruded from the envelope. These

N. Ingram Hendey

1946-01-01

23

Laminated Fresnel Lenses.  

National Technical Information Service (NTIS)

A fabrication method for making plastic-on-glass laminated Fresnel lenses is discussed. These Fresnel lenses are for application in an RCA solar photovoltaic concentrator array now in the prototype stage of development. This laminated Fresnel lens fabrica...

R. W. Jebens

1980-01-01

24

Diatom-based interpretation of sediment banding in an urbanized lake  

Microsoft Academic Search

Sediment stratigraphy and diatom succession were studied in an 80.5-cm core taken from the deepest part of Third Sister Lake, a small kettle hole in a recently urbanized landscape of southeastern Michigan. Alternating light clay and dark organic bands documented sporadic inputs of clay from outside the basin during rain events, rather than annual laminations. Urban construction activity also disrupted

Brian K. Hammer; Eugene F. Stoermer

1997-01-01

25

Prospects in diatom research.  

PubMed

Diatoms are unicellular photosynthetic eukaryotes that play a major role in the global cycling of carbon and silicon. They are believed to have arisen from a secondary endosymbiotic event between two eukaryotes, a red alga and a flagellated heterotroph. Recent analysis of a diatom genome indeed reveals a 'mosaic' nature, with genes derived from plant, animal and bacterial lineages. Advances in molecular genomics are facilitating the use of diatom-specific genes or pathways for biotechnology. Another interest is in understanding the artistry of the amorphous silica shell and the underlying biomineralization process. Materials scientists and chemists are now exploiting diatoms to develop new biomimetic approaches and to create silicon-based microdevices with specific features. PMID:15831384

Lopez, Pascal J; Desclés, Julien; Allen, Andrew E; Bowler, Chris

2005-04-01

26

DIATOM: A DIALOG Simulator.  

ERIC Educational Resources Information Center

|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)|

Waldstein, Robert

1981-01-01

27

Photosynthesis in diatoms  

Microsoft Academic Search

(1)Pure cultures of N. closterium and N. palea have been isolated and used in a manometric study of photosynthesis and respiration in diatoms.(2)The influence of light intensity, temperature, carbon dioxide concentration and culture age upon rate of photosynthesis have been investigated.(3)Photosynthetic and respiratory quotients have been determined as a function of temperature and light intensity. Fat production in diatoms is

H. Albert Barker

1935-01-01

28

Origin of convolute lamination  

Microsoft Academic Search

Many syndepositional soft-sediment folds form by processes unrelated to mass movement, chemical change or tectonism. One such group of folds, convolute laminations, characteristically develops at the tops of the fine-grained, cross-laminated sand beds in flysch, prodelta, and alluvial point bar sequences. Most convolute lamination forms during the late stages of deposition of individual sedimentation units. As current velocity wanes, cohesive

Lowe

1975-01-01

29

Laminated reflective panels  

SciTech Connect

A laminated reflective panel comprises at least one mirror sheet which is less than 2.0 mm in thickness and which bears a reflective coating on its rear face. Each mirror sheet is laminated to a flat glass backing sheet which is thicker than the mirror sheet. The backing sheet is preferably of float glass.

Duchene, E.; Laroche, P.

1985-04-16

30

Environmental investigations using diatom microfossils  

USGS Publications Warehouse

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.

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

2010-01-01

31

Treatise on diatoms.  

PubMed

In R. E. Norris's review of The Diatoms of the United States Exclusive of Alaska and Hawaii, volume 1, by Ruth Patrick and Charles; W. Reimer [153, 1369 (16 Sept. 1966)], the Introduction, which was signed only by Patrick, was erroneously attributed to Patrick and Reimer. PMID:17737557

Norris, R E

1967-01-27

32

Fossil diatoms and neogene paleolimnology  

USGS Publications Warehouse

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.

Platt, Bradbury, J.

1988-01-01

33

Automation of Optimal Laminate Design  

Microsoft Academic Search

Composite laminates are in widespread use in the aerospace industry. As well as satisfying strength and stiffness criteria, the final laminate design has to be manufacturable in terms of compatibility between adjacent panels, thus introducing conflicting constraints on the allowed laminate stacking sequences. An attempt to automate the laminate design process is described. The method uses a mixture of a

T. Coates; A. Smith; M. Emanuel; B. Peterson

2007-01-01

34

Thermally Stable Laminating Resins.  

National Technical Information Service (NTIS)

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 autoc...

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

1972-01-01

35

The lamin protein family  

Microsoft Academic Search

Summary  The lamins are the major architectural proteins of the animal cell nucleus. Lamins line the inside of the nuclear membrane,\\u000a where they provide a platform for the binding of proteins and chromatin and confer mechanical stability. They have been implicated\\u000a in a wide range of nuclear functions, including higher-order genome organization, chromatin regulation, transcription, DNA\\u000a replication and DNA repair. The

Travis Dittmer; Tom Misteli

2011-01-01

36

Diatom DNA as historical information  

NASA Astrophysics Data System (ADS)

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.

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

2009-04-01

37

Asymptotic neutrality of diatomic molecules  

Microsoft Academic Search

We use the no-binding theorem of Thomas-Fermi theory to prove that a large diatomic molecule is “almost” neutral. That is to say, that if the total nuclear charge isZ then the numberN of electrons required for the diatomic molecule to be stable satisfies\\u000a

Jan Philip Solovej

1990-01-01

38

Interactions between Diatoms and Bacteria  

PubMed Central

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.

Amin, Shady A.; Parker, Micaela S.

2012-01-01

39

Planktonic diatoms of Lake Ontario  

USGS Publications Warehouse

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.

Reinwand, Jerry F.

1969-01-01

40

Persistent Laminations from Seifert Surfaces  

Microsoft Academic Search

A persistent lamination for a knot K is an essential lamination in the\\u000acomplement of K, which remains essential after every non-trivial Dehn surgery\\u000aalong K. Having a persistent lamination implies, for example, that every\\u000amanifold obtained by non-trivial Dehn surgery along K has universal cover R^3.\\u000aIn this paper we present a method for building persistent laminations for knots

Mark Brittenham

2001-01-01

41

Laminate armor and related methods  

DOEpatents

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.

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

2013-02-26

42

The Diatom EST Database.  

PubMed

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

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

2005-01-01

43

Moisture ingress into organic laminates  

Microsoft Academic Search

The electronic industry's most common laminates (FR-4, HTFR-4, PI, CE, and BT) were investigated for their equilibrium levels of moisture and diffusion rates and monitored for their moisture content as a function of electrical capacitance. Isothermal sorption tests were performed on the laminates to find the equilibrium moisture content in each laminate at various environmental conditions. The moisture content of

Michael G. Pecht; Haleh Ardebili; Anand A. Shukla; John K. Hagge; David Jennings

1999-01-01

44

Laminated BEAM loops  

NASA Astrophysics Data System (ADS)

BEAM sensors include treated loops of optical fiber that modulate optical throughput with great sensitivity and linearity, in response to curvature of the loop out of its plane. This paper describes BEAM sensors that have two loops treated in opposed fashion, hermetically sealed in flexible laminations. The sensors include an integrated optoelectronics package that extracts curvature information from the treated portion of the loops while rejecting common mode errors. The laminated structure is used to sense various parameters including displacement, force, pressure, flow, and acceleration.

Danisch, Lee A.

1996-10-01

45

Heat insulating laminate  

SciTech Connect

The disclosure concerns a heat insulating laminate which is comprised of a contractile thin film, a first noncontractile metal reflecting thin film at at least one side of the contractile film and at least a second noncontractile metal reflecting thin film beyond the first one of those films. Adjacent films are bonded together at scattered areas. In one version, the density of the bonding areas between the contractile film and the first noncontractile film is greater and the density of the bonding areas between successive noncontractile layers away from the contractile layer decreases stepwise. Shrinking of the contractile film causes wrinkles in the noncontractile films. An additional protective film may be laminated to the contractile film.

Yoshikawa, Y.

1983-05-31

46

Laminated plastic material  

US Patent & Trademark Office Database

A laminated plastic material comprises surface layers of paper impregnated with amino formaldehyde resin and inner layers of paper containing a flame retardant material and impregnated with phenol formaldehyde resin. The flame retardant material is a product of interaction of an aluminum or copper compound with phosphoric acid and nitrogen bases and contains, in weight percent: where MO is at least one metallic oxide, the flame retardant material content ranging from 4 to 8 weight percent, with the following ratio of the laminated plastic components, in weight percent: ______________________________________ paper for surface layers 9 to 26 paper for inner layers 26 to 49 phenol-formaldehyde resin 16 to 30 amino-formaldehyde resin 5 to 26 ______________________________________

1981-09-08

47

Diatoms: Powerful Indicators of Environmental Change.  

National Technical Information Service (NTIS)

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

S. S. Dixit J. P. Smol J. C. Kingston D. F. Charles

1992-01-01

48

Marine Diatom Plasmids and their Biotechnological Applications.  

National Technical Information Service (NTIS)

The long-range objective of the proposed research is to achieve transformation of marine diatoms. The more immediate objectives pertain to the characterization of two small plasmids we have discovered in a marine diatom, Cylindrotheca fusiformis, a specie...

F. G. Plumley

1992-01-01

49

Temperature dependence of association of diatomic ions in diatomic gases  

NASA Astrophysics Data System (ADS)

The present study compares the experimental rate coefficient temperature dependences for the association of diatomic ions in diatomic gases with the results of model calculations in which it is assumed that the stabilization of the initially formed unstable association complex occurs through the formation of a 'supercomplex'. The acceptable degree of agreement obtained between model and experimental data for the cases of four sample reactions, on the basis of a minimum of plausible assumptions, indicates that earlier theoretical models furnishing an accurate description of the formation and destruction of the association complex, but failing to reproduce experimental data, inadequately treated the temperature dependence of the stabilization step.

Johnsen, R.

1986-10-01

50

Design of variable–stiffness laminates using lamination parameters  

Microsoft Academic Search

Benefits of the directional properties of fiber reinforced composites could be fully utilized by proper placement of the fibers in their optimal spatial orientations. This paper investigates the optimal design of fiber reinforced rectangular composite plates for minimum compliance. The classical minimum compliance design problem is formulated in the lamination parameters space. The use of lamination parameters guarantees that the

Shahriar Setoodeh; Mostafa M. Abdalla; Zafer Gürdal

2006-01-01

51

Renaissance in diatomic spectroscopy  

NASA Astrophysics Data System (ADS)

New technological developments resulted in several periods of renaissances of spectroscopy, the period on microwaves and later the period with lasers, and led to developments of new models for description of observations, thus to understanding the underlying physics. Today, the exciting period of cold molecules has started and demands for new data from molecular spectroscopy and completion in their modeling. This contribution will describe the status of understanding before the era of ``cold molecules'' and note open questions when entering the field of cold molecules. Because large varieties of cold molecules are studied, like deeply bound (about 1eV) or very weakly bound (less than 10-7 eV) ones, the spectroscopic tools and the theoretical descriptions have to be largely extended. We will describe recent success regarding different molecules of diatomic alkaliand alkaline-earth atoms as examples and will show how to use the often huge body of spectroscopic data for obtaining predictions for optimal paths to produce ultra cold molecules in a desired molecular state. It is very exciting to combine the results of spectroscopy and of studies of ultra cold ensembles which are influenced by their atom-to-molecule changeover. This allows already to complete the understanding of the electronic structure of atom pairs from infinite internuclear separation down to the range of strongly overlapping electronic distribution in some cases (e.g. KRb or KCs). However, enhanced effort is required for describing quantitatively the discoveries, already published or expected, like a contribution to the field hunting for signatures of time dependence of fundamental constants. For molecules with their rotational and vibrational motion the ratio of electron mass-to-nuclear mass as a fundamental constant shows up as an obvious attraction for spectroscopic studies.

Tiemann, Eberhard; Knöckel, Horst

2013-07-01

52

Lamin A, farnesylation and aging  

Microsoft Academic Search

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

Sita Reddy; Lucio Comai

53

The Diatom Collection of the California Academy of Sciences  

NSDL National Science Digital Library

The California Academy of Sciences provides this useful site on the "taxonomic information, images, records of collections, and references pertaining to diatoms." Although minimal in graphic imagery, the site does a nice job of describing these microscopic aquatic organisms via four main sections: Diatom Identification (Glossary, some Light Miscroscope Images), Diatom databases (Taxon, Types, Locality and Publications), Diatom research (Diatom Genus Project), and Diatom Links. Students, researchers, and anyone interested in diatoms will find an abundance of information at this site.

54

Luminescence properties of a nanoporous freshwater diatom.  

PubMed

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

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

2011-05-27

55

Driven Diatomic Oscillator Chain Model  

NSDL National Science Digital Library

The Driven Diatomic Oscillator Chain model displays a one-dimensional diatomic chain of coupled harmonic oscillators with one end driven by an external force and the other end attached to a sliding rod shock absorber. The mass and Stoke's Law damping for the shock absorber are chosen to eliminate reflections at the driving frequency. The frequency of the driving force and the masses can be changed using the text boxes provided. You can change the initial position of the masses by dragging individual oscillators. You can also change the number of oscillators in the chain. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. The Driven Diatomic Oscillator Chain model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_osc_chains_OscillatorChainDrivenDiatomic.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for Newtonian mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Christian, Wolfgang

2008-07-05

56

Dead Diatoms Do Tell Tales  

NSDL National Science Digital Library

This activity engages learners to make a model of sediment cores using different kinds of glass beads and sand. They learn how to examine the types, numbers, and conditions of diatom skeletons in the model sediment cores and tell something about the hypothetical paleoclimate that existed when they were deposited. The students get to be climate detectives.

Dahlman, Luann; Andrill

57

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....

2010-06-08

58

Molded and laminated infrared imager  

NASA Astrophysics Data System (ADS)

In previous work, laminated midwave infrare imagers were designed and manufactured. These systems used the technique of laminating a piece of plastic on to a silicon substrate lens and then single-point diamond turning an aspheric/diffractive surface on the plastic. These lenses had a focal length of 50 mm and f/# of 2.6. This paper updates the progress of the developing prototype to show initial results of compression molding the aspheric/diffractive surface onto the plastic laminated surface. The results of the previous built imagers will be compared to the ones that have been molded.

Vicker, Del E.

2003-09-01

59

Black walnut induced laminitis.  

PubMed

A 5-y-old Paint horse gelding was evaluated for acute laminitis after exposure to black walnut shavings. The gelding's feet were previously soaked in an ice bath continuously for approximately 24 h. Treatment consisted of anti-inflammatory and vasodilator therapy. Serial radiographs revealed progressive palmar deviation of the third phalanx and subsolar abscesses in both forefeet. The gelding developed purulent discharge from the right coronary band and the hoof wall detached circumfrentially. Euthanasia was elected after 54 days. Continual exposure of the gelding's feet to ice water temperatures may have caused decreased perfusion and increased edema formation in the laminae resulting in decreased blood flow and exacerbating the existing ischemic necrosis. PMID:10670077

Thomsen, M E; Davis, E G; Rush, B R

2000-02-01

60

Edge Delamination of Composite Laminates.  

National Technical Information Service (NTIS)

A review of the literature and the research performed at the Institute for Aerospace Research on the subject of delamination in composite laminates are presented. Delamination is known to initiate at free edges where the influence of interlaminar stresses...

C. Poon N. C. Bellinger Y. Xiong R. W. Gould

1992-01-01

61

Creep of laminated aluminum composites  

Microsoft Academic Search

The creep behavior of a laminate system consisting of alternate layers of pure aluminum and SAP (sintered aluminum powder)\\u000a sheet has been examined in the temperature range 323 to 473 K and in the stress range 35 to 68 MN m?2. It was observed that secondary creep strain in the laminates was greater than in elemental SAP; the secondary creep

W. Moore; T. J. Davies

1980-01-01

62

Metallic laminates for engine applications  

SciTech Connect

Laminated metal composites consist of alternating metal (or metal matrix composite) layers that are bonded together. This paper reviews the processing of these materials and the properties relevant to engine applications. These properties include strength, toughness and damping capacity. Laminates can have very attractive properties relative to other structural materials for weight critical applications requiring high stiffness, strength and fracture toughness. The structure-property correlations that determine these properties are described.

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

1994-06-01

63

Marine diatoms as optical biosensors.  

PubMed

We have chemically modified the frustules of the marine diatom Coscinodiscus concinnus Wm. Smith to properly bind a highly selective bioprobe such as an antibody. By measuring the changes in the photoluminescence emission of diatoms frustules, we have monitored the molecular recognition event between the antibody and its ligand: the dissociation constant estimated is of the same order of that measured by standard Biacore. The nanostructured silica frustules, a low-cost and natural available material, have shown high sensitivity, equal to 1.2+/-0.2 nm microM(-1), and a detection limit of 100 nM, and thus are quite ideal candidates for lab-on-particle applications. PMID:18809311

De Stefano, L; Rotiroti, L; De Stefano, M; Lamberti, A; Lettieri, S; Setaro, A; Maddalena, P

2008-08-20

64

Luminescence studies of fresh water diatom frustules  

Microsoft Academic Search

Siliceous frustules were extracted from fresh water diatoms by treating with concentrated HCl. The diatom frustules consist\\u000a of nano-porous silica structures that exhibit unique optoelectronic and photonic properties. Photoluminescence (PL) properties\\u000a of diatom frustules at various excitation wavelengths were done. A visible PL band centered at 440 nm was observed when excited\\u000a at 300 nm, 370 nm and 380 nm

Nirmal Mazumder; Ankur Gogoi; Ranjan Dutta Kalita; Gazi A. Ahmed; Alak K. Buragohain; Amarjyoti Choudhury

2010-01-01

65

Diatom Frustules: Physical, Optical, and Biotechnological Applications  

Microsoft Academic Search

\\u000a Diatoms are unicellular photosynthetic eurkaryotes within the class Bacillariophyceae whose peculiarity amongst other microalgae\\u000a is a siliceous cell wall (Round et al., 1990). Traditionally, diatoms have been subdivided into two major groups based upon\\u000a their symmetry: the centrales have radial symmetry, whilst the pennales have bilateral symmetry. Diatoms are found in both freshwater and marine environments, as well as in

Helen E. Townley

66

Some Observations of Diatoms Under Turbulence  

Microsoft Academic Search

The effect of turbulence on several freshwater diatom taxa was investigated and our findings are described herein. We have\\u000a compared diatom morphology in shallow natural systems that experience turbulence due to wind and in river\\/waterfall systems\\u000a where turbulence is due to high flow rates. We have also introduced turbulence into diatom laboratory cultures by mechanical\\u000a shaking and by forcing air

Stephen J. Clarson; Miriam Steinitz-Kannan; Siddharth V. Patwardhan; Ramamurthi Kannan; Ryan Hartig; Louis Schloesser; Douglas W. Hamilton; Jeffrey K. A. Fusaro; Ryan Beltz

2009-01-01

67

Milking Diatoms for Sustainable Energy: Biochemical Engineering versus Gasoline-Secreting Diatom Solar Panels  

Microsoft Academic Search

In the face of increasing CO2 emissions from conventional energy (gasoline), and the anticipated scarcity of crude oil, a worldwide effort is underway for cost-effective renewable alternative energy sources. Here, we review a simple line of reasoning: (a) geologists claim that much crude oil comes from diatoms; (b) diatoms do indeed make oil; (c) agriculturists claim that diatoms could make

T. V. Ramachandra; Durga Madhab Mahapatra; Karthick B; Richard Gordon

2009-01-01

68

Diatom Paleolimnology Data Cooperative Home Page  

NSDL National Science Digital Library

The Phycology Section of the Patrick Center for Environmental Research, part of Philadelphia's Academy of Natural Science, presents the Diatom Paleolimnology Data Cooperative (DPDC). This database contains information on diatoms and related ecological and paleolimnological data applicable to the study of global climate change. Users have three search options: browse and download stratigraphic and calibration data sets; view individual diatom counts; or search for occurrences of specific taxa in all data sets. The site includes links to algae databases, also from the Academy of Natural Science. Researchers are encouraged to submit diatom core and surface sediment data to the DPDC.

1998-01-01

69

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

SciTech Connect

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.

Broers, Jos L.V. [Department of Molecular Cell Biology, Box 17, Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, PO Box 616, NL-6200 MD Maastricht (Netherlands) and Department of Biomedical Engineering, Biomechanics and Tissue Engineering Eindhoven University of Technology (Netherlands)]. E-mail: jos.broers@molcelb.unimaas.nl; Kuijpers, H.J.H. [Department of Molecular Cell Biology, Box 17, Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, PO Box 616, NL-6200 MD Maastricht (Netherlands); Oestlund, C. [Departments of Medicine and of Anatomy and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, NY 10027 (United States); Worman, H.J. [Departments of Medicine and of Anatomy and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, NY 10027 (United States); Endert, J. [Department of Molecular Cell Biology, Box 17, Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, PO Box 616, NL-6200 MD Maastricht (Netherlands); Ramaekers, F.C.S. [Department of Molecular Cell Biology, Box 17, Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, PO Box 616, NL-6200 MD Maastricht (Netherlands)

2005-04-01

70

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

PubMed

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. PMID:15748902

Broers, Jos L V; Kuijpers, H J H; Ostlund, C; Worman, H J; Endert, J; Ramaekers, F C S

2004-12-20

71

Lamin A, farnesylation and aging.  

PubMed

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. PMID:21871450

Reddy, Sita; Comai, Lucio

2011-08-16

72

Failure Strengths of Laminated Glass Units.  

National Technical Information Service (NTIS)

Laminated glass units have gained popularity as an architectural glazing product. Their safety and versatility are being used to satisfy many design situations. This usage has established a need for increased understanding of the behavior of laminated gla...

P. L. Reznik J. E. Minor

1986-01-01

73

Fracture and Crack Growth in Orthotropic Laminates.  

National Technical Information Service (NTIS)

A mathematical model based on the classical shear-lag assumptions is used to study the residual strength and fracture behavior of composite laminates with symmetrically placed buffer strips. The laminate is loaded by a uniform remote longitudinal tensile ...

J. G. Goree A. K. Kaw

1985-01-01

74

Oceanographic and Biogeochemical Insights from Diatom Genomes  

Microsoft Academic Search

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

Chris Bowler; Assaf Vardi

2010-01-01

75

Beyond micromachining: the potential of diatoms.  

PubMed

Diatoms are microscopic, single-celled algae that possess rigid cell walls (frustules) composed of amorphous silica. Depending on the species of diatom and the growth conditions, these frustules can display a wide range of different morphologies. It is possible to design and produce specific frustule morphologies that have potential applications in nanotechnology. PMID:10322443

Parkinson, J; Gordon, R

1999-05-01

76

Do diatom algae frustules accumulate uranium?  

Microsoft Academic Search

Neutron Activation Analysis (NAA) and Synchrotron Radiation X-ray Fluorescent Analysis (SRXRFA) were used to measure the content of uranium and a few other trace elements in samples of bottom sediments of Lake Baikel separated into biogenic (diatom algae frustules) and clastic components by an aerodynamic method. Uranium is rejected, rather than accumulated by diatom algae frustules.

E. L. Goldberg; M. A. Grachev; V. A. Bobrov; A. V. Bessergenev; B. V. Zolotaryov; Ye. V. Likhoshway

1998-01-01

77

Hypothesized resource relationships among African planktonic diatoms  

Microsoft Academic Search

Several hypotheses are advanced for resource relationships among planktonic diatoms in African freshwater lakes that are consistent with the light and nutrient conditions of the lakes and the extant and fossil distributions of the diatom species in them. The hypotheses are all testable and are potentially powerful tools for interpreting past climatic conditions. A ranking is proposed along a Si

Peter Kilham; Susan S. Kilham; Robert E. Hecky

1985-01-01

78

Assessing subglacial processes from diatom fragmentation patterns  

USGS Publications Warehouse

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.

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

2004-01-01

79

The rise of the rhizosolenid diatoms.  

PubMed

The 18S ribosomal DNA molecular phylogeny and lipid composition of over 120 marine diatoms showed that the capability to biosynthesize highly branched isoprenoid (HBI) alkenes is restricted to two specific phylogenetic clusters, which independently evolved in centric and pennate diatoms. The molecular record of C25 HBI chemical fossils in a large suite of well-dated marine sediments and petroleum revealed that the older cluster, composed of rhizosolenid diatoms, evolved 91.5 +/- 1.5 million years ago (Upper Turonian), enabling an accurate dating of the pace of diatom evolution that is unprecedented. The rapid rise of the rhizosolenid diatoms probably resulted from a major reorganization of the nutrient budget in the mid-Cretaceous oceans, triggered by plate tectonics. PMID:15105500

Damsté, Jaap S Sinninghe; Muyzer, Gerard; Abbas, Ben; Rampen, Sebastiaan W; Massé, Guillaume; Allard, W Guy; Belt, Simon T; Robert, Jean-Michel; Rowland, Steven J; Moldowan, J Michael; Barbanti, Silvana M; Fago, Frederick J; Denisevich, Peter; Dahl, Jeremy; Trindade, Luiz A F; Schouten, Stefan

2004-04-23

80

DDD: Dynamic Database for Diatomics  

NASA Astrophysics Data System (ADS)

We have developed as web-based database containing spectra of diatomic molecules. All data is computed from first principles, and if a user requests data for a molecule/ion that is not in the database, new calculations are automatically carried out on that species. Rotational, vibrational, and electronic transitions are included. Different levels of accuracy can be selected from qualitatively correct to the best calculations that can be carried out. The user can view and modify spectroscopic constants, view potential energy curves, download detailed high temperature linelists, or view synthetic spectra.

Schwenke, David

2004-03-01

81

Impedances of Laminated Vacuum Chambers  

SciTech Connect

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].

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

2011-06-22

82

The role of mat-forming diatoms in the formation of Mediterranean sapropels  

NASA Astrophysics Data System (ADS)

The origins of sapropels (sedimentary layers rich in organic carbon) are unclear, yet they may be a key to understanding the influence of climate on ocean eutrophication, the mechanisms of sustaining biological production in stratified waters and the genesis of petroleum source rocks. Recent microfossil studies of foraminifera and calcareous nannofossils have focused attention on a deep chlorophyll maximum as a locus for the high production inferred for sapropel formation, but have not identified the agent responsible. Here we report the results of a high-resolution, electron-microscope-based study of a late Quaternary laminated sapropel in which the annual flux cycle has been preserved. We find that much of the production was by diatoms, both mat-forming and other colonial forms, adapted to exploit a deep nutrient supply trapped below surface waters in a stratified water column. Reconstructed organic-carbon and opal fluxes to the sediments are comparable to those at high-productivity sites in today's oceans, and calculations based on diatom Si/C ratios suggest that the high organic-carbon content of sapropels may be entirely accounted for by sedimenting diatoms. We propose that this style of production may have been common in ancient Palaeogene and Cretaceous seas, environments for which conventional appeals to upwelling-driven production to account for the occurrence of diatomites, and some organic-carbon-rich sediments, have never seemed wholly appropriate.

Kemp, Alan E. S.; Pearce, Richard B.; Koizumi, Itaru; Pike, Jennifer; Rance, S. Jae

1999-03-01

83

CHARACTERISATION OF THE ADHESION OF FOULING DIATOMS ONTO TEST SURFACES  

Microsoft Academic Search

The dominant presence of marine diatoms fouling the latest non-toxic, antifoul coatings has increased interest in characterising diatom adhesives and the mechanisms of their adhesion. In this study the adhesion of two benthic, fouling diatoms [Craspedostauros australis Cox and Haslea sp. Simonsen (Bacillariophyceae, Ochrophyta)] was measured on 23 test surfaces with different chemical properties. The adhesion of the diatoms was

A. Willis; J. Pacifico; T. M. Dugdale; R. Wetherbee

2007-01-01

84

Marine chronology based on 14C dating on diatoms proteins  

Microsoft Academic Search

We present a new method of obtaining radiocarbon dates for proteins intrinsic to diatom frustules (sillafin). By asserting age models for sediment core samples that lack calcium carbonate, this method will improve interpretations of diatom-based paleoproxies for either marine or lacustrine. In preparation for radiocarbon dating by Accelerator Mass Spectrometry, diatoms were concentrated from core sediment samples. The diatoms frustules

Christine Hatté; Gregory Hodgins; A. J. Timothy Jull; Bongi Bishop; Benoit Tesson

2008-01-01

85

The Phaeodactylum genome reveals the evolutionary history of diatom genomes  

Microsoft Academic Search

Diatoms are photosynthetic secondary endosymbionts found throughout marine and freshwater environments, and are believed to be responsible for around one-fifth of the primary productivity on Earth. The genome sequence of the marine centric diatom Thalassiosira pseudonana was recently reported, revealing a wealth of information about diatom biology. Here we report the complete genome sequence of the pennate diatom Phaeodactylum tricornutum

Chris Bowler; Jonathan H. Badger; Jane Grimwood; Kamel Jabbari; Alan Kuo; Uma Maheswari; Cindy Martens; Florian Maumus; Robert P. Otillar; Edda Rayko; Asaf Salamov; Klaas Vandepoele; Bank Beszteri; Ansgar Gruber; Marc Heijde; Michael Katinka; Thomas Mock; Klaus Valentin; Fréderic Verret; John A. Berges; Colin Brownlee; Jean-Paul Cadoret; Anthony Chiovitti; Chang Jae Choi; Sacha Coesel; Alessandra de Martino; J. Chris Detter; Colleen Durkin; Angela Falciatore; Jérome Fournet; Miyoshi Haruta; Marie J. J. Huysman; Bethany D. Jenkins; Katerina Jiroutova; Richard E. Jorgensen; Yolaine Joubert; Aaron Kaplan; Nils Kröger; Peter G. Kroth; Julie La Roche; Erica Lindquist; Markus Lommer; Véronique Martin-Jézéquel; Pascal J. Lopez; Susan Lucas; Manuela Mangogna; Karen McGinnis; Linda K. Medlin; Anton Montsant; Marie-Pierre Oudot-Le Secq; Carolyn Napoli; Miroslav Obornik; Micaela Schnitzler Parker; Jean-Louis Petit; Betina M. Porcel; Nicole Poulsen; Matthew Robison; Leszek Rychlewski; Tatiana A. Rynearson; Jeremy Schmutz; Harris Shapiro; Magali Siaut; Michele Stanley; Michael R. Sussman; Alison R. Taylor; Assaf Vardi; Peter von Dassow; Wim Vyverman; Anusuya Willis; Lucjan S. Wyrwicz; Daniel S. Rokhsar; Jean Weissenbach; E. Virginia Armbrust; Beverley R. Green; Yves van de Peer; Igor V. Grigoriev

2008-01-01

86

Dimensional control of polymer composite laminate  

NASA Astrophysics Data System (ADS)

In order to manufacture high quality composites, the dimensional control of composite laminate is required. Composite laminate dimension is greatly affected by curing processing parameters such as applied pressure, heat-up rate, bleeder quantities, and temperature. This paper investigates the dimensional stability of a C/E composite laminate under autoclave curing conditions by using the economical and highly reproducible Taguchi Method. The optimum curing conditions for stabilizing the laminate thickness were obtained from dynamic characteristic analysis. An equation accurately predicting the laminate thickness was postulated after analyzing the experimental data with the statistical method.

Chen, Ming-Yang; Chen, Shih-Ming; Zeng, Long-Zeng; Chen, Jong-Pyng

1992-05-01

87

Multilayer printed wiring board lamination  

SciTech Connect

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.

Lula, J.W.

1980-06-01

88

Synthesis and characterization of diatom inspired nanocomposites  

NASA Astrophysics Data System (ADS)

This dissertation addresses the investigation of two novel methods to synthesize composite nanomaterials inspired by marine microalgae called diatoms. Diatoms are inspirational sources of silica structures, ordered at micro- to nanoscale, that possess unique optical properties. The fabrication of nanomaterials with well-defined and controllable micro-to nanoscale features has been of great interest for chemical, optical, electronic, catalytic, environmental, and medical applications. While bottom-up and top-down approaches have been extensively used to fabricate two-dimensional structures and devices, there is a need for inexpensive methods to mass-produce complex micro- to nanoscale structures with a variety of three-dimensional (3D) morphologies at high degrees of precision, reproducibility, and chemical tailorability. To explore the fabrication of 3D nanostructures, this study harnessed the biomineralization capacity of diatom cell cultures to fabricate Si-Ge oxide nanocomposites on one hand and the chemical bath deposition on the other hand. A two-stage photobioreactor strategy was used to metabolically insert nanostructured germanium into the silica microstructure of diatom of diatom Pinnularia sp. In the first stage, diatom cells were grown to the point of silicon starvation. In the second stage, a pulse of silicon and germanium solution was added to the silicon-starved cells. Various electron microscopy techniques were utilized to validate the extent of the insertion and the subsequent incorporation of germanium into the diatom silica matrix. In the second method to form diatom inspired nanocomposites, we utilize a simple, inexpensive chemical bath deposition technique to deposit a cadmium sulfide nanocrystals on the patterned surface of diatom biosilica. A parametric investigation of the factors affecting the chemical bath process was carried out. The morphology, structural and compositional properties of the composites were characterized by electron microscopy. Absorption spectroscopy, photoluminescence and Raman spectroscopy were used to study the properties of the deposited CdS thin films.

Gutu, Timothy

89

Diatom Community Response to Global Change  

NASA Astrophysics Data System (ADS)

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.

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

2008-12-01

90

Disruption of lamin B1 and lamin B2 processing and localization by farnesyltransferase inhibitors.  

PubMed

Lamin A and the B-type lamins, lamin B1 and lamin B2, are translated as pre-proteins that are modified at a carboxyl terminal CAAX motif by farnesylation, proteolysis and carboxymethylation. Lamin A is further processed by proteolysis to remove the farnesyl, but B-type lamins remain permanently farnesylated. Two childhood diseases, Hutchinson Gilford Progeria Syndrome and restrictive dermopathy are caused by defects in the processing of lamin A, resulting in permanent farnesylation of the protein. Farnesyltransferase inhibitors, originally developed to target oncogenic Ras, have recently been used in clinical trials to treat children with Hutchinson Gilford Progeria Syndrome. Lamin B1 and lamin B2 play important roles in cell proliferation and organ development, but little is known about the role of farnesylation in their functions. Treating normal human fibroblasts with farnesyltransferase inhibitors causes the accumulation of unprocessed lamin B2 and lamin A and a decrease in mature lamin B1. Normally, lamins are concentrated at the nuclear envelope/lamina, but when farnesylation is inhibited, the peripheral localization of lamin B2 decreases as its nucleoplasmic levels increase. Unprocessed prelamin A distributes into both the nuclear envelope/lamina and nucleoplasm. Farnesyltransferase inhibitors also cause a rapid cell cycle arrest leading to cellular senescence. This study suggests that the long-term inhibition of protein farnesylation could have unforeseen consequences on nuclear functions. PMID:23475125

Adam, Stephen A; Butin-Israeli, Veronika; Cleland, Megan M; Shimi, Takeshi; Goldman, Robert D

2013-03-01

91

CHEMISTRY: Harnessing the Power of Diatomics  

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required. When a diatomic molecule is broken up into its constituent atoms, these very energetic atoms provide a large driving force for further reaction. Diatomic molecules often do not undergo productive chemistry, however, because the energy needed to break the diatomic bond is also high. In his Perspective, Thorp discusses the work by MacBeth et al., who have synthesized a nonheme iron complex that reacts with O2 to produce two equivalents of a metal-oxo complex. The complex elegantly mimic the ability of some enzymes to influence metal ion coordination spheres.

H. Holden Thorp (University of North Carolina at Chapel Hill;Department of Chemistry)

2000-08-11

92

Diatomic Hoenl-London factor computer program  

SciTech Connect

A new method is presented for computation of diatomic rotational line strengths, or Hoenl-London factors. The traditional approach includes separately calculating line positions and Hoenl-London factors and assigning parity labels. The present approach shows that one merely computes the line strength for all possible term differences and discards those differences for which the strength vanishes. Numerical diagonalization of the upper and lower Hamiltonians is used, which directly obtains the line positions, Hoenl-London factors, total parities, and e/f parities for both heteronuclear and homonuclear diatomic molecules. The fortran computer program discussed is also applicable for calculating n-photon diatomic spectra.

Hornkohl, James O.; Parigger, Christian G.; Nemes, Laszlo

2005-06-20

93

Diatoms.  

ERIC Educational Resources Information Center

|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)|

Hungerford, James J.

1988-01-01

94

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

NASA Astrophysics Data System (ADS)

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.

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.

2007-10-01

95

Oceanographic and biogeochemical insights from diatom genomes.  

PubMed

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. PMID:21141668

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

2010-01-01

96

Ultraviolet Lasing Transitions in Diatomic Molecules.  

National Technical Information Service (NTIS)

The work performed is primarily directed toward a better spectroscopic understanding of UV laser transitions in selected diatomic molecules. Specifically the work emphasizes the analysis of spectroscopic data for discrete (bound-bound) and diffuse (bound-...

J. Tellinghuisen

1980-01-01

97

Oceanographic and Biogeochemical Insights from Diatom Genomes  

NASA Astrophysics Data System (ADS)

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.

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

2010-01-01

98

The Ecology of Diatoms in Hardwater Habitats.  

National Technical Information Service (NTIS)

Diatoms comprise the major group of algae in Iowa waters. Their ecological significance, important in pollution evaluation studies, cannot be fully appreciated without a thorough knowledge of their taxonomy. A scale for abundance rating was used giving at...

J. D. Dodd

1971-01-01

99

Modeling of Atom-Diatom Scattering.  

National Technical Information Service (NTIS)

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 severa...

J. M. Sindoni

1992-01-01

100

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...

101

Characterization of the Hydra lamin and its gene: A molecular phylogeny of metazoan lamins.  

PubMed

We report sequences for nuclear lamins from the teleost fish Danio and six invertebrates. These include two cnidarians (Hydra and Tealia), one priapulid, two echinoderms, and the cephalochordate Branchiostoma. Combining these results with earlier data on Drosophila, Caenorhabditis elegans, and various vertebrates, the following conclusions on lamin evolution can be drawn. First, all invertebrate lamins resemble in size the vertebrate B-type lamin. Second, all lamins described previously for amphibia, birds and mammals as well as the first lamin of a fish, characterized here, show a cluster of 7 to 12 acidic residues in the tail domain. Since this acidic cluster is absent from all invertebrate lamins including that of the cephalochordate Branchiostoma, it was acquired with the vertebrate lineage. The larger A-type lamin of differentiated cells must have arisen subsequently by gene duplication and insertion of an extra exon. This extra exon of the vertebrate A-lamins is the only major change in domain organization in metazoan lamin evolution. Third, the three introns of the Hydra and Priapulus genes correspond in position to the last three introns of vertebrate B-type lamin genes. Thus the entirely different gene organization of the C. elegans and Drosophila Dmo genes seems to reflect evolutionary drift, which probably also accounts for the fact that C. elegans has the most diverse lamin sequence. Finally we discuss the possibility that two lamin types, a constitutively expressed one and a developmentally regulated one, arose independently on the arthropod and vertebrate lineages. PMID:10441677

Erber, A; Riemer, D; Hofemeister, H; Bovenschulte, M; Stick, R; Panopoulou, G; Lehrach, H; Weber, K

1999-08-01

102

Lamins A and C but not lamin B1 regulate nuclear mechanics.  

PubMed

Mutations in the nuclear envelope proteins lamins A and C cause a broad variety of human diseases, including Emery-Dreifuss muscular dystrophy, dilated cardiomyopathy, and Hutchinson-Gilford progeria syndrome. Cells lacking lamins A and C have reduced nuclear stiffness and increased nuclear fragility, leading to increased cell death under mechanical strain and suggesting a potential mechanism for disease. Here, we investigated the contribution of major lamin subtypes (lamins A, C, and B1) to nuclear mechanics by analyzing nuclear shape, nuclear dynamics over time, nuclear deformations under strain, and cell viability under prolonged mechanical stimulation in cells lacking both lamins A and C, cells lacking only lamin A (i.e. "lamin C-only" cells), cells lacking wild-type lamin B1, and wild-type cells. Lamin A/C-deficient cells exhibited increased numbers of misshapen nuclei and had severely reduced nuclear stiffness and decreased cell viability under strain. Lamin C-only cells had slightly abnormal nuclear shape and mildly reduced nuclear stiffness but no decrease in cell viability under strain. Interestingly, lamin B1-deficient cells exhibited normal nuclear mechanics despite having a significantly increased frequency of nuclear blebs. Our study indicates that lamins A and C are important contributors to the mechanical stiffness of nuclei, whereas lamin B1 contributes to nuclear integrity but not stiffness. PMID:16825190

Lammerding, Jan; Fong, Loren G; Ji, Julie Y; Reue, Karen; Stewart, Colin L; Young, Stephen G; Lee, Richard T

2006-07-05

103

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

SciTech Connect

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.

Sylvius, Nicolas [Laboratory of Genetics of Cardiac Diseases, University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, K1Y 4W7 (Canada)], E-mail: sylvius@cng.fr; Hathaway, Andrea; Boudreau, Emilie; Gupta, Pallavi; Labib, Sarah; Bolongo, Pierrette M. [Laboratory of Genetics of Cardiac Diseases, University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, K1Y 4W7 (Canada); Rippstein, Peter; McBride, Heidi [University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, K1Y 4W7 (Canada); Bilinska, Zofia T. [First Department of Cardiac Disease, Institute of Cardiology, Alpejska 42, 04-628 Warsaw (Poland); Tesson, Frederique [Laboratory of Genetics of Cardiac Diseases, University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, K1Y 4W7 (Canada)

2008-08-01

104

Biocide activity of diatom-silver nanocomposite  

Microsoft Academic Search

Diatom-nAg composites containing 1wt.% of metallic silver nanoparticles (?20nm) have been obtained by a colloidal route and chemical reduction. This nanostructured powder has proved to be a selective green inorganic biocide which reduces the starting concentrations of Escherichia coli and Micrococcus luteus cultures by at least 5 orders of magnitude, while completely inactive against yeast. Diatom-nAg can be considered as

M. Suárez; L. Esteban-Tejeda; F. Malpartida; A. Fernández; J. S. Moya

2010-01-01

105

The chemical composition of the diatom frustule  

Microsoft Academic Search

Summary  This paper describes the X-ray diffraction studies carried out on a large number of present-day, as well as fossil diatom\\u000a frustules. From the diffraction patterns given by the various specimens, it has been concluded that the silica present in\\u000a diatom frustules is not in an amorphous or sub-colloidal state as was spposed by previous workers but that it is crystalline

T. V. Desikachary; N. E. Dweltz

1961-01-01

106

Spines on diatoms:Do copepods care?  

Microsoft Academic Search

CaZanus$nmarchicus was allowed to feed on two forms of the diatom Thalassiosira weiss- flogii (=T. fluviatilis): normal cells, which are spinose, and cells which did not have spines. Filtration rates of Calanus on the spinose form were on average 1.7 times higher than on cells with no spines. The diatom Thalassiosira weissflogii (Grunow) G. Fryxell and Hasle Comb. nov. (=Thalassiosira

DIAN J. GIFFORD; RICHARD N. BOHRER; CARL M. BOYD

1981-01-01

107

Growth of copper on diatom silica by electroless deposition technique  

NASA Astrophysics Data System (ADS)

In this study, the growth of copper on porous diatom silica by electroless deposition method has been demonstrated for the first time. Raman peaks of copper (145, 213, and 640 cm-1) appeared in the copper-coated, Amphora sp. and Skeletonema sp. diatom samples, confirming the successful deposition of copper. Scanning electron microscopy (SEM) indicated the presence of copper on the diatom silica surface. The 3D intricate structure of diatom was still evident by optical and scanning electron microscopy analyses when the diatom samples were immersed in the copper bath for only 5 hours. Incubating the diatom samples in the copper bath for 24 h produced a dense coating on the diatom surface and covered the intricate 3D structure of the diatom silica. These results present possibilities of the fabrication of hierarchically organized copper with 3D diatom replica structures.

Dalagan, Juliet Q.; Enriquez, Erwin P.; Li, Lain-Jong; Lin, Cheng-Te

2013-04-01

108

Rapid Automated Induction Lamination (RAIL) for High-Volume Production of Carbon/Thermoplastic Laminates.  

National Technical Information Service (NTIS)

An innovative Rapid Automated Induction Lamination (RAIL) process has been developed that can fabricate fully consolidated 8-ply AS4/polyetherimide (PEI) laminates in high volumes. The process relies on induction-based rapid volumetric heating for multila...

N. Shevchenko B. K. Fink D. Heider J. W. Gillespie S. Yarlagadda

2001-01-01

109

Elastoacoustic response of laminated plates  

NASA Astrophysics Data System (ADS)

The application of composite materials in the aerospace and naval structures has increased enormously due to high specific strength and specific stiffness afforded by these materials. In this paper a formulation is developed based on Hamilton's Principle and laminated composite plate theory to study the elasto-acoustical response of composite plates under heavy fluid loadings. The formulation starts by using Hamilton's principle in conjunction with shear deformable theory of laminated composite plates. The acoustic pressure described by wave equation is computed similar to Sandman and Nelisse. Using the Rayleigh Ritz method and symbolic mathematics for evaluation of integrals, the formulation provides efficient approach for the problem defined. Typical results include radiation impedance as a function of driving frequency, vibroacoustic indicators such as radiated sound power and mean square velocity for a model problem. Such results are very important in studying constrained layer damping when viscolastic dampers are used in structural components.

Kolar, Ramesh

2005-04-01

110

Plastic Laminate Pulsed Power Development  

SciTech Connect

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.

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

111

Flat laminated microbial mat communities  

Microsoft Academic Search

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.,

Jonathan Franks; John F. Stolz

2009-01-01

112

Impact of diatoms on fabric and chemical stability of diatom–kaolin mixtures  

Microsoft Academic Search

Natural soils containing diatoms tend to have high compressibility, low shear strength, and difficulty of compaction. Yet, given their unique characteristics (i.e., high water absorption, liquid limit, and friction angle), there is great potential for utilizing diatoms and natural diatomaceous soils in the development of engineered particulate materials for geotechnical and geoenvironmental engineering applications. One of these applications is the

Angelica M. Palomino; Sungho Kim; Alex Summitt; Dante Fratta

2011-01-01

113

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

Microsoft Academic Search

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

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

2007-01-01

114

Characterization of the Hydra Lamin and Its Gene: A Molecular Phylogeny of Metazoan Lamins  

Microsoft Academic Search

.   We report sequences for nuclear lamins from the teleost fish Danio and six invertebrates. These include two cnidarians (Hydra and Tealia), one priapulid, two echinoderms, and the cephalochordate Branchiostoma. Combining these results with earlier data on Drosophila, Caenorhabditis elegans, and various vertebrates, the following conclusions on lamin evolution can be drawn. First, all invertebrate lamins resemble\\u000a in size the

Andreas Erber; Dieter Riemer; Helmut Hofemeister; Marc Bovenschulte; Reimer Stick; Georgia Panopoulou; Hans Lehrach; Klaus Weber

1999-01-01

115

Updated diatom biostratigraphy for Monterey Formation  

SciTech Connect

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.

Barron, J.A.

1986-04-01

116

High-resolution diatom records of climate and hydrological variability over the last two millennia along coastal British Columbia (Canada)  

NASA Astrophysics Data System (ADS)

High-resolution ocean archives covering the last 2000 years are essential for assessments of modern-day and future climate, and better understanding of the response of marine environments to global change. Sedimentary records recovered from coastal locations yield information on both terrestrial and marine conditions and permit detailed reconstructions of past climatic and environmental variability. Anoxic basins within coastal inlets favour the preservation of varved (annually laminated) sediment records, permitting high-resolution analysis of past environmental change. Although a number of marine records have been recovered from the west coast of British Columbia, Canada, few studies have focused on conditions over the last 2000 years. Here we present siliceous microfossil (diatom) records from a pair of anoxic fjords located along the southwestern coast of British Columbia. The record from Effingham Inlet (Vancouver Island) represents 1500 years of regional climate and hydrological variability at sub-decadal resolution. Fossil diatom assemblages from the inlet are sensitive to changes in freshwater inputs from nearby rivers and creeks. Increased freshwater discharge into the inlet between 825 and 925 AD, 1000 and 1325 AD and again from ca. 1550 to 1850 AD favoured deep water renewal events in the fjord. The timing of these periods correlates with reconstructed periods of cooler and moister conditions and a negative Pacific Decadal Oscillation (PDO) index in the North Pacific. A second site in Frederick Sound (Seymour-Belize inlet complex) represents a preliminary evaluation of the sensitivity of fossil diatom assemblages to regional climate variability in this inlet over the last two millennia. Analysis of the diatom assemblages between 1650 and 550 AD from Frederick Sound suggests that diatom assemblages within this basin are sensitive to changes in regional climate, matching the conditions observed within the more southern Effingham Inlet. Differences between the two records also highlight the critical importance of site selection for the reconstruction of environmental change over the last 2000 years.

Hay, M. B.; Pienitz, R.; Dallimore, A.; Calvert, S. E.; Thomson, R.; Baumgartner, T. R.; Enkin, R.; Cooke, K.

2010-12-01

117

Exotic diatomic molecules of cesium  

NASA Astrophysics Data System (ADS)

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.

Tallant, Jonathan E.

118

Energy transfer in diatom/diatom molecular collisions  

SciTech Connect

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

Sohlberg, K.W.

1992-01-01

119

Investigation into the Optical Properties of Nanostructured Silica from Diatoms.  

National Technical Information Service (NTIS)

The overall objective of this project was to investigate the optical properties of silica isolated from the unicellular algae known as diatoms. The diatom species used in this study were Cylindrotheca fusiformis, Cyclotella meneghiana, Navicula pelliculos...

M. Hildebrand B. Palenik

2003-01-01

120

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

NASA Astrophysics Data System (ADS)

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).

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

2007-12-01

121

Wall Curl in Bending of Laminated Steel  

Microsoft Academic Search

Laminated steel sheets consist of thin visco-elastic polymer layers sandwiched between sheets of steel and are used primarily in products where sound and vibration need to be damped. Although laminated steel products have been successfully manufactured by stamping, these parts are relatively flat. Problems arise, however, when using the material in bending operations. The main problem is the fact that

Edmundo Corona; Travis Eisenhour; Shengjun Yin; James J. Mason

2004-01-01

122

Residual strength of laminated composites after impact  

Microsoft Academic Search

This article deals with the residual strength assessment on completely as well as partially penetrated laminated composites due to impact loads by idealizing the damage locations as holes and cracks. Modifications are made in the inherent flaw model (IFM) of Waddoups, Eisenman, and Kaminski (known as the WEK model) to correlate the fracture data of laminated composites. For velocities above

V. Kamala Kannan; A. Rajadurai; B. Nageswara Rao

2011-01-01

123

Fatigue/Impact Studies in Laminated Composites.  

National Technical Information Service (NTIS)

The residual strength of the impact-damaged laminates can be predicted using an analytical model. Both the power law and the wearout models appear to be useful in predicting the fatigue life of the composite laminates. However, because of the slope parame...

V. S. Avva

1983-01-01

124

Testing Laminated Glass for Impact Resistance  

Microsoft Academic Search

Comparative testing of laminated glass made up by different combinations for impact resistance has been performed. The testing corroborates the possibility of using glass subjected to special thermal treatment (STT) in the production of impact-resistant laminated glass. Glasses based on STT glass satisfy the impact resistance requirements of GOST R 51136–98, and their thickness and weight are a factor of

A. I. Shutov; A. N. Frank; I. A. Novikov; A. S. Ostapko; A. S. Bonchuk; A. N. Burdov

2004-01-01

125

DIATOM COMMUNITIES OF SPRINGS IN THE SOUTHERN ALPS  

Microsoft Academic Search

In the Adamello-Brenta Regional Park (Trentino, Italy), the diatom communities of 30 mountain springs, 15 on crystalline and 15 on carbonate substratum, were studied between 1993 and 1996. Two of them, one from each substratum type, were sampled monthly for a more detailed investigation of seasonal changes in community structure. The diatom flora of these springs consisted of 250 diatom

Marco Cantonati

1998-01-01

126

Tychoplanktonic diatoms from a stenothermal spring in Iraqi Kurdistan  

Microsoft Academic Search

Seasonal variations in the tychoplanktonic diatoms are described from Serchinar, a stenothermal spring in Iraqi Kurdistan. The flora was poor in species with only 22 taxa being recorded. Cymbella affinis, Achnanthes amphicephala and Cocconeis placentula var. euglypta dominated the diatom flora and only three other taxa were commonly represented. The total number of suspended diatoms exceeded 250,000 cells 1 during

B. K. Maulood; G. C. F. Hinton

1979-01-01

127

Diatom community structure on commercially available ship hull coatings  

Microsoft Academic Search

Diatoms are primary colonizers of both antifouling and fouling-release ship hull coatings. There are few published studies which report on diatom community development on modern ship hull coatings. This study reports diatom communities on eight commercial marine ship hull coatings exposed at three static immersion sites along the east coast of Florida, viz. Daytona, Sebastian, and Miami. The coatings tested

Kelli A. Zargiel; Jeffrey S. Coogan; Geoffrey W. Swain

2011-01-01

128

The role of aggregation for the dissolution of diatom frustules  

Microsoft Academic Search

Observations that the majority of silica dissolution occurs within the upper 200 m of the ocean, and that sedimentation rates of diatom frustules generally do not decrease significantly with depth, suggested reduced dissolution rates of diatoms embedded within sinking aggregates. To investigate this hypothesis, silica dissolution rates of aggregated diatom cells were compared to those of dispersed cells during conditions

Uta Passow; Anja Engel; Helle Ploug

2003-01-01

129

Radiocarbon dating of diatom-bound organic compounds  

Microsoft Academic Search

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

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

2006-01-01

130

Are diatoms a food source for Antarctic sponges?  

Microsoft Academic Search

Living diatoms are commonly found within Antarctic Porifera, and generally interpreted as additional food source, or as mutualists or parasites of sponge tissues. However, no data are available about temporal variations of the abundance of diatoms inside sponges especially during the winter period. In this paper we analysed the amount of diatom frustules and chlorophaeopigment concentration in six species of

C. Cerrano; B. Calcinai; E. Cucchiari; C. Di Camillo; M. Nigro; F. Regoli; A. Sarà; S. Schiaparelli; C. Totti; G. Bavestrello

2004-01-01

131

Radiocarbon dating of diatom-bound organic compounds  

Microsoft Academic Search

Here we present a new method for obtaining radiocarbon dates for the organic compounds intrinsic to diatom frustules. This method will improve age models for sediment cores that lack calcium carbonate and improve current interpretations of diatom-based paleoproxies. In preparation for radiocarbon dating by Accelerator Mass Spectrometry, compounds intrinsic to diatom frustules are released from their opal matrix by dissolution

Anitra E. Ingalls; Robert F. Anderson; Ann Pearson

2004-01-01

132

Modified Ribose Receptor Response in Isolated Diatom Frustules  

Microsoft Academic Search

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

Fairbanks; Carly R

2011-01-01

133

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...

134

AFM nanoindentations of diatom biosilica surfaces.  

PubMed

Diatoms have intricately and uniquely nanopatterned silica exoskeletons (frustules) and are a common target of biomimetic investigations. A better understanding of the diatom frustule structure and function at the nanoscale could provide new insights for the biomimetic fabrication of nanostructured ceramic materials and lightweight, yet strong, scaffold architectures. Here, we have mapped the nanoscale mechanical properties of Coscinodiscus sp. diatoms using atomic force microscopy (AFM)-based nanoindentation. Mechanical properties were correlated with the frustule structures obtained from high-resolution AFM and scanning electron microscopy (SEM). Significant differences in the micromechanical properties for the different frustule layers were observed. A comparative study of other related inorganic material including porous silicon films and free-standing membranes as well as porous alumina was also undertaken. PMID:17397194

Losic, Dusan; Short, Ken; Mitchell, James G; Lal, Ratnesh; Voelcker, Nicolas H

2007-03-31

135

From diatoms to silica-based biohybrids.  

PubMed

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

Nassif, Nadine; Livage, Jacques

2010-12-21

136

Edge stresses in alumina/zirconia laminates  

SciTech Connect

Using the technique of fluorescence piezospectroscopy, the authors determine the distribution of thermal residual stresses across the edges of three laminated alumina/zirconia composites. They develop a methodology for separating the measured stress state into microstresses that result from grain-to-grain thermal mismatch and macrostresses that result from lamination-induced thermal mismatch between individual plies. Comparison between the measured edge-stress distributions and those calculated based on a simple force-superposition model shows good agreement, indicating that the laminate system is well approximated as linear elastic. Given the experimental confirmation of significant edge stresses in multi-ply laminates, the possibility of failure initiating at composite edges must be considered in the design of surface-compressed laminate structures with the aim of mediating the detrimental effect of surface flaws.

Sergo, V. [Univ. di Trieste (Italy). Dipt. di Ingegneria dei Materiali; Lipkin, D.M.; Clarke, D.R. [Univ. of California, Santa Barbara, CA (United States). Materials Dept.; Portu, G. de [CNR-IRTEC, Faenza (Italy)

1997-07-01

137

Stationary turbine component with laminated skin  

SciTech Connect

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.

James, Allister W. (Orlando, FL)

2012-08-14

138

Bending analysis of angle-ply laminates  

NASA Astrophysics Data System (ADS)

The accuracy and the applicability of the higher-order theory developed by Savithri and Varadan (1990) for the analysis of symmetric angle-ply laminates were assessed by comparing results obtained with this theory, which incorporates the continuity of transverse shear stresses at the interfaces, with results obtained with the smeared laminate theory of Reddy (1984). For this comparison a laminate plate is used which is composed of a finite number of anisotropic layers, each of which has only a single plane of elastic symmetry parallel to the XY plane; the plate is assumed to be simply supported on the boundaries and subjected to normal traction (q(X,Y)) on the upper surface. It was found that the new theory is highly accurate for symmetric laminates, and, for comparable accuracies, the computation cost is much less than that of the corresponding smeared laminate theory.

Savithri, S.; Varadan, T. K.

1991-05-01

139

Strength of tape cast and laminated ceramics  

SciTech Connect

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.

Ham-Su, R.; Wilkinson, D.S. [McMaster Univ., Hamilton, Ontario (Canada). Dept. of Materials Science and Engineering

1995-06-01

140

Sedimentary diatom assemblages and their utility in computing diatom-inferred pH in Sudbury Ontario lakes  

Microsoft Academic Search

Surface sediment diatoms from 30 Sudbury lakes were analyzed to establish a relationship between diatoms and limnological\\u000a characteristics of these lakes. Factor analysis of various chemical and physical variables suggested that most of the variance\\u000a was associated with the pH, pH-metal, and conductivity factors. Factor analysis of common diatom taxa indicated that the distribution\\u000a of most of these diatoms is

Sushil S. Dixit; Aruna S. Dixit; R. Douglas Evans

1988-01-01

141

Engineering and medical applications of diatoms.  

PubMed

Biologists, and diatomists in particular, have long studied the properties of single-cell algae, and engineers are just discovering how to exploit features unique to these organisms. Their uniform nanopore structure, microchannels, chemical inertness, and silica microcrystal structure suggest many nanoscale applications. This paper proposes three potential research initiatives taking advantage of diatom morphology and mechanical and chemical properties: (1) embedding diatom frustules in a metal-film membrane; (2) magnetizing frustules for pinpoint drug delivery; and (3) producing silica nanopowders from frustules. The potential benefits of each initiative and its technical challenges are outlined. PMID:15762165

Wee, Kit Mun; Rogers, Tony N; Altan, Burhanettin S; Hackney, Stephen A; Hamm, Christian

2005-01-01

142

Crystal palaces--diatoms for engineers.  

PubMed

A survey of diatom research from the mid-19th century to modern times shows that it has always been closely linked to technological (especially: imaging) progress. Perfection of the light-microscope led to a plethora of studies which--whilst being mostly of a descriptive nature--furnished a solid basis for informative practical applications in biostratigraphy and ecology, for instance. When the electron-microscope (transmission- and scanning-) was invented, diatoms belonged to the very first objects examined and this led to attempts at a more profound structural, functional and morphogenetic interpretation of these fascinating natural Crystal Palaces. PMID:15762168

Sterrenburg, Frithjof A S

2005-01-01

143

Changes in diatom-dominated biofilms during simulated improvements in water quality: implications for diatom-based monitoring in rivers  

Microsoft Academic Search

Although benthic diatoms are used to assess river water quality, there are few data on the rate at which diatom assemblages react to changes in water quality. The aim of this study was to assess the reaction time of diatoms and to discuss the changes occurring during water quality improvement on the basis of their autecological characteristics. In order to

Frédéric Rimet; Luc Ector; Henry-Michel Cauchie; Lucien Hoffmann

2009-01-01

144

Seasonally resolved diatom ?18O records from the West Antarctic Peninsula over the last deglaciation  

NASA Astrophysics Data System (ADS)

Understanding the response of the Antarctic ice sheets during the rapid climatic change that accompanied the last deglaciation has implications for establishing the susceptibility of these regions to future 21st Century warming. A unique diatom ?18O record derived from a high-resolution deglacial seasonally laminated core section off the west Antarctic Peninsula (WAP) is presented here. By extracting and analysing single species samples from individual laminae, season-specific isotope records were separately generated to show changes in glacial discharge to the coastal margin during spring and summer months. As well as documenting significant intra-annual seasonal variability during the deglaciation, with increased discharge occurring in summer relative to spring, further intra-seasonal variations are apparent between individual taxa linked to the environment that individual diatom species live in. Whilst deglacial ?18O are typically lower than those for the Holocene, indicating glacial discharge to the core site peaked at this time, inter-annual and inter-seasonal alternations in excess of 3‰ suggest significant variability in the magnitude of these inputs. These deglacial variations in glacial discharge are considerably greater than those seen in the modern day water column and would have altered both the supply of oceanic warmth to the WAP as well as regional marine/atmospheric interactions. In constraining changes in glacial discharge over the last deglaciation, the records provide a future framework for investigating links between annually resolved records of glacial dynamics and ocean/climate variability along the WAP.

Swann, George E. A.; Pike, Jennifer; Snelling, Andrea M.; Leng, Melanie J.; Williams, Maria C.

2013-02-01

145

A Progressive Damage Model for Laminated Composites Containing Stress Concentrations  

Microsoft Academic Search

A progressive damage model is presented for notched laminated composites subjected to tensile loading. The model is capable of assessing damage in laminates with arbitrary ply-orientations and of predicting the ultimate tensile strength of the notched laminates. The model consists of two parts, namely, the stress analysis and the failure analysis. Stresses and strains in laminates were analyzed on the

Fu-Kuo Chang; Kuo-Yen Chang

1987-01-01

146

Probabilistic methods for the calculation of laminate properties  

SciTech Connect

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.

Mcmanus, H.L. (MIT, Cambridge, MA (United States))

1993-06-01

147

Direct composite laminate veneers: three case reports.  

PubMed

Re-establishing a patient's lost dental esthetic appearance is one of the most important topics for contemporary dentistry. New treatment materials and methods have been coming on the scene, day by day, in order to achieve such an aim. Most dentists prefer more conservative and aesthetic approaches, such as direct and indirect laminate veneer restorations, instead of full-ceramic crowns for anteriors where aesthetics is really important. Laminate veneers are restorations which are envisioned to correct existing abnormalities, esthetic deficiencies and discolo-rations. Laminate veneer restorations may be processed in two different ways: direct or indirect. Direct laminate veneers have no need to be prepared in the laboratory and are based on the principle of application of a composite material directly to the prepared tooth surface in the dental clinic. Indirect laminate veneers may be produced from composite materials or ceramics, which are cemented to the tooth with an adhesive resin. In this case report, direct composite laminate veneer technique used for three patients with esthetic problems related to fractures, discolorations and an old prolapsed restoration, is described and six-month follow-ups are discussed. As a conclusion, direct laminate veneer restorations may be a treatment option for patients with the esthetic problems of anterior teeth in cases similar to those reported here. PMID:23875090

Korkut, Bora; Yan?ko?lu, Funda; Günday, Mahir

2013-05-30

148

Diatom Analysis and the Acidification of Lakes  

Microsoft Academic Search

Diatom microfossils preserved in lake sediments can be used to provide evidence for lake acidification. Unlike documentary methods of historical reconstruction, the sediment record is potentially useful at all sites, it is usually continuous and it can be extended backwards in time as desired. Cores can be taken with little disturbance, by freezing in situ if necessary, and sediments deposited

R. W. Battarbee

1984-01-01

149

Incoherent Scattered Radiation in Diatomic Molecules  

Microsoft Academic Search

Raman spectra excited in diatomic gases by the line lambda2536 of mercury have been photographed with a quartz spectrograph. An apparatus for using gases at pressures from ten to fifteen atmospheres has been built, with great improvement as compared with the use of gases at atmospheric pressure. Results obtained with H2, N2, O2, NO are reported. A particularly complete investigation

F. Rasetti

1929-01-01

150

Missing solar ultraviolet opacity and diatomic molecules  

Microsoft Academic Search

The solar atmospheric model calculations incorporating absorption by hydrogen and metals and Rayleigh scattering by hydrogen give larger specific intensity in the solar ultraviolet spectrum than that observed. This discrepancy has been interpreted as due to some unknown source(s) of opacity in this spectral region. We have, therefore, compared the absorption coefficient due to bands of nine diatomic molecules with

S. P. Tarafdar; M. S. Vardya

1972-01-01

151

Vibrational Transition Probabilities of Diatomic Molecules: I  

Microsoft Academic Search

An approximation is made which allows analytic integration of the `overlap', and other, integrals of vibrational wave functions in Morse potentials that arise in the study of the electronic spectra of diatomic molecules. The heavy and lengthy work that goes into numerical integration is thus avoided for many bands of many systems. The necessity for the type of approximation made

P A Fraser; W R Jarmain

1953-01-01

152

Vibrational Spectrum of a Disordered Diatomic Chain.  

National Technical Information Service (NTIS)

A partially diatomic chain with a long-range order (a non-Markoff chain) consists of two sublattices and is determined by the probability of finding an atom of the given type in the strange sublattice. The frequency spectrum of the non-Markoff chain is fo...

K. Breter V. B. Priezhev

1975-01-01

153

Phenanthrene accumulation kinetics in marine diatoms.  

PubMed

Cell surface and intracellular accumulation kinetics of phenanthrene were studied in two coastal marine diatoms. Cell surface uptake and depuration rate constants were two to three times greater in the smaller Thalassiosira pseudonana than in T. weissflogii, reflecting the 2.8-fold difference in surface-area-to-volume ratio (A/V) between the two species. However, cell surface accumulation was faster than most other environmental and biological process, supporting the assumption that cell surfaces are in equilibrium with the water. Intracellular depuration rate constants of phenanthrene were similar (0.56 d(-1), 0.62 d(-1)) for both diatoms and for other hydrophobic organic contaminants (ca 1 d(-1)) with a range of hydrophobicities and chemical structures in other microalgae. Biodilution could be a significant factor in the internal accumulation of phenanthrene, as phenanthrene loss rate constants were on the order of phytoplankton growth rates in the spring and summer (1-3 d(-1)). Organic carbon-normalized phenanthrene bioconcentration factors were not significantly different for the two diatom species. The fraction of phenanthrene in the cell surface compartment at steady-state (x1) was directly related to the A/V of the two diatoms and a Chlorophyte microalga, showing that intracellular partitioning, which may affect phenanthrene trophic transfer, depends on phytoplankton cell size. PMID:12966988

Fan, Cheng-Wei; Reinfelder, John R

2003-08-01

154

Fine Structure of a Diatom Centrosome  

Microsoft Academic Search

The centrosome of the diatom Surirella ovalis is a dense spherical structure 500 mmu in diameter with filaments 15 mmu in diameter connected to it. The interior is filled with uniform granules but does not contain a typical centriole or clear area. The filaments emanating from it resemble the filaments of the mitotic apparatus, but they are present during interphase

Ryan W. Drum; H. Stuart Pankratz

1963-01-01

155

Seasonal fluctuations of Lake Michigan diatoms  

USGS Publications Warehouse

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.

Holland, Ruth E.

1969-01-01

156

Thermal buckling of symmetrically laminated composite plates  

NASA Astrophysics Data System (ADS)

This paper discusses an investigation into the thermal buckling of symmetrically laminated composite plates. In this study thermal buckling is investigated for laminates under two different simple support conditions, fixed and sliding. These laminates are subjected to the conditions of a uniform temperature change, and a temperature change varying linearly along the length of the plate. The effects of the principal material axes not being aligned with the edges of the plate are also investigated. The buckling response is studied using variational methods, specifically the Trefftz criterion. A Rayleigh-Ritz formulation is used to obtain numerical results from the formulations for the prebuckling response and the buckling response.

Meyers, C. A.; Hyer, M. W.

157

Neuropathic pain management in chronic laminitis.  

PubMed

Managing pain in horses afflicted by chronic laminitis is one of the greatest challenges in equine clinical practice because it is the dreadful suffering of the animals that most often forces the veterinarian to end the battle with this disease. The purpose of this review is to summarize our current understanding of the complex mechanisms involved in generating and amplifying pain in animals with laminitis and, based on this information, to propose a modified approach to pain therapy. Furthermore, a recently developed pain scoring technique is presented that may help better quantify pain and the monitoring of responses to analgesic treatment in horses with laminitis. PMID:20699178

Driessen, Bernd; Bauquier, Sébastien H; Zarucco, Laura

2010-06-11

158

Environmental effects on unsymmetric composite laminates  

SciTech Connect

In order to take full advantage of the tailorability of composite materials, the response of unsymmetric composite laminates is studied in an integrated analytical/experimental program. The laminates tested include a symmetric and an unsymmetric layup constructed of the IM7/977-2 graphite epoxy material system. The test conditions simulated include both ambient and hot/wet conditions in addition to tension and torsion. A quasi-three-dimensional finite element program is used to evaluate the stress-strain response of these laminates. These responses are compared with experimental observations. 14 refs.

Ochoa, O.O.; Ross, G.R. (Texas A M University, College Station (USA))

1991-07-01

159

Effect of loading and lamination parameters on the optimum design of laminated plates  

Microsoft Academic Search

This paper illustrates the effect of loading conditions and lamination parameters on the optimum design of the laminated composite\\u000a plates. Optimum design procedure based on the flexibility criterion is presented in this paper. The objective is to determine\\u000a the optimum thickness of the laminate layers and its optimum orientations without exhibiting any failure. The finite element\\u000a method based on Mindlin

A. E. Assie; A. M. Kabeel; F. F. Mahmoud

2011-01-01

160

Damage of hybrid composite laminates  

NASA Astrophysics Data System (ADS)

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.

Haery, Haleh A.; Kim, Ho Sung

2013-08-01

161

Flat laminated microbial mat communities  

NASA Astrophysics Data System (ADS)

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.

Franks, Jonathan; Stolz, John F.

2009-10-01

162

Laminated Anisotropic Reinforced Plastic Plates and Shells.  

National Technical Information Service (NTIS)

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 pla...

V. I. Korolev

1981-01-01

163

Static Behaviour of Laminated Composite Shells  

NASA Astrophysics Data System (ADS)

With the advancement of aerospace engineering and the progress made in the allied industries, new forms of structural components having high strength-to-weight ratio have been developed. Fibre-reinforced laminate structures are one such type of construction. In the present study, linear behaviour of laminated composite shells under static loading is investigated using ANSYS, the finite element software, by varying the parameters such as laminate thickness, fibre orientation, stacking sequence, fibre strength and radius-to-thickness ratio. It has been observed that the deflection remains constant beyond four layers in the case of anti-symmetric arrangement and for the same angle of fibre orientation, deflection is not influenced by the lamination sequence. The non-dimensional deflection decreases with increase in material anisotropy and included angle, while it increases with increase in radius-to-thickness ratio.

Kuriakose, B.; Sathyabhama, L.; Valsarajan, K. V.

2012-12-01

164

Nuclear mechanics: lamin webs and pathological blebs.  

PubMed

Anomalies in the three-dimensional shape of the nucleus are associated with a number of genetic diseases. These shape distortions include lobulated structures, with localized bulges referred to as nuclear blebs. Blebbing can result from mutations in genes encoding lamin intermediate filaments that form the lamin cortex, a thin meshwork lining the nuclear envelope. However, the biophysical origins of nuclear blebs remain a mystery. A recent study by Funkhouser et al. provides a theoretical model in which the lamin cortex is modeled as a thin, inhomogeneous elastic shell. This model shows that partial segregation of different lamin sub-networks-each with distinct mechanical properties-can lead to shell morphologies similar to blebbed nuclei in living cells. PMID:23697996

Broedersz, Chase P; Brangwynne, Clifford P

2013-05-15

165

Fatigue Resistance Criteria for Laminated Composite Structures.  

National Technical Information Service (NTIS)

This work investigated criteria for prevention of fatigue damage in metal matrix composite laminates. The approach was based on an earlier observation that, in as-fabricated unidirectional composites with elastic-brittle fibers and soft elastic-plastic ma...

G. J. Dvorak

1978-01-01

166

Nonlinear Effects on Composite Laminate Thermal Expansion.  

National Technical Information Service (NTIS)

Analyses of Graphite/Polyimide laminates shown that the thermomechanical strains cannot be separated into mechanical strain and free thermal expansion strain. Elastic properties and thermal expansion coefficients of unidirectional Graphite/Polyimide speci...

Z. Hashin B. W. Rosen R. B. Pipes

1979-01-01

167

Structural Reliability Analysis of Laminated CMC Components.  

National Technical Information Service (NTIS)

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 analy...

S. F. Duffy J. L. Palko J. P. Gyekenyesi

1991-01-01

168

Wrapped Laminated Felted Monolithic Combustible Cartridge Case.  

National Technical Information Service (NTIS)

The patent application relates to a combustible cartridge case for use with a fully telescoped round of ammunition wherein the laminated case is fabricated by wrapping thin sheets of felted combustible material. Flame penetration is moderated by applying ...

R. I. Brabets

1974-01-01

169

Lamination Residual Stresses in Fiber Composites.  

National Technical Information Service (NTIS)

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, g...

I. M. Daniel T. Liber

1975-01-01

170

Geometrically Nonlinear Analysis of Laminated Elastic Structures.  

National Technical Information Service (NTIS)

The research deals with the analysis of laminated composite plates and shells that can be used to model automobile bodies, aircraft wings and fuselages, and pressure vessels among many others. The finite element method, a numerical technique for engineeri...

J. N. Reddy

1984-01-01

171

Elastic constants of layers in isotropic laminates  

Microsoft Academic Search

The individual laminae elastic constants in multilayer laminates composed of dissimilar isotropic layers were determined using ultrasonic-resonance spectroscopy and the linear theory of elasticity. Ultrasonic resonance allows one to measure the free-vibration response spectrum of a traction-free solid under periodic vibration. These frequencies depend on pointwise density, laminate dimensions, layer thickness, and layer elastic constants. Given a material with known

Paul R. Heyliger; Hassel Ledbetter; Sudook Kim; Ivar Reimanis

2003-01-01

172

High energy impact on woven laminates  

Microsoft Academic Search

The influence of high velocity impacts on CFRPs was studied by launching Spherical steel masses, at velocities from 60 m\\/s to 550 m\\/s, against carbon fiber\\/epoxy woven laminates. The extension of the damage induced in the laminate was measured by C-Scan. Finite element numerical simulation of the impact test used a failure model based on the Chang-Chang model. A comparison

J. López-Puente; R. Zaera; C. Navarro

2003-01-01

173

Cofiring of integrated magnetic/dielectric laminates  

NASA Astrophysics Data System (ADS)

Stress development during cofiring a bi-layer ferrite/dielectric laminate has been investigated by measuring camber development and shrinkage rate difference. The trend of camber development follows a similar pattern to the linear shrinkage rate difference between ferrite and dielectric ceramics. No cofiring defects are observed in the multilayer structure of ferrite and dielectric laminates, indicating that good sintering compatibility between BZN and NiCuZn ferrite exists during cofiring.

Tung, Y. N.; Peng, T. M.; Jean, J. H.; Lin, S. C.

2011-10-01

174

Diatoms in the Gulf of California: Seasonal flux patterns and the sediment record for the last 15,000 years  

NASA Astrophysics Data System (ADS)

Flux and taxonomic composition of the diatom assemblage was determined for biweekly sediment traps in the central Gulf of California over a 2-year period. Fluxes and relative abundance of taxa are not significantly different in traps from the eastern side of the Guaymas Basin and the western side of the Carmen Basin, indicating that patterns of diatom production are uniform across the central gulf at all seasons of the year. The annual maximum in diatom flux occurred during the winter season of both years, either as a sustained event over many weeks (1990) or as a series of short blooms (1991-1992). Of the most abundant taxa, only hyalochaete Chaetoceros species showed a clear seasonal cycle, with a flux maximum in the spring of both years. Factor analysis defines five assemblages representing (1) summer and fall conditions of surface stratification and nutrient limitation, (2) winter bloom triggered by onset of strong northwesterly winds, (3) late spring to summer production probably related to sporadic events during periods of weak southeasterly winds, (4) spring 1991 inferred to reflect the distal edge of a coastal upwelling phase, (5) lateral advection of resuspended sediments from the continental shelf, possibly resulting from trapped coastal waves during summer hurricanes and from storms during the 1991-1992 El Niño-Southern Oscillation (ENSO). The diatom data support the inference that subtropical Pacific water penetrates deeper into the gulf during ENSO events. In order to compare the sediment trap record to a sediment core, a second factor analysis was done using only the taxa which are preserved in the sediment and omitting the most abundant taxa, which showed little downcore variation. This produces five factors representing (1) summer-fall low production, (2) early winter bloom, (3) late winter-spring upwelling, (4) ENSO conditions and (5) a late spring-summer assemblage of uncertain significance. Variation of species characterisic of each factor was examined in piston core Atlantis II 125-8 56JPC taken from the oxygen minimum zone in Guaymas Basin. Correlation to nearby Deep Sea Drilling Project Hole 480 indicates that the core penetrates to about 15 ka, with laminated sediments in the Holocene (0-10 ka) and late deglacial (11-13 ka) and massive (nonlaminated) sediments around Younger Dryas time (10-11 ka) and before 13 ka. Downcore variations in the diatom assemblage do not correspond directly to presence of laminations, implying that the processes controlling bottom water oxygen content are not determined by conditions of surface water production. Presence of calcareous nannofossils downcore correlates inversely with two diatom assemblages (ENSO and winter bloom indicators) and not with occurrence of laminations, suggesting that occurrence of calcareous nannofossils in the sediment is at least partly a function of surface water production. Prior to 12 ka, production was lower than at present during all seasons, implying weaker winds throughout the year; subtropical waters extended to the midgulf as they do today during ENSO events. Between 11 and 12 ka, conditions were similar to those of the present, with relatively high winter and spring production resulting from northwesterly winds. ENSO events were still common, although less so than during the preceding period. Younger Dryas time was one of transition with intermediate conditions: a slackening of winter-spring northwesterly winds and reduction of total annual production, and increased occurrence of ENSO conditions. In the early to middle Holocene winter, northwesterlies increased to a maximum, resulting in very high production, but apparently did not persist into spring; subtropical waters mostly disappeared from the gulf. In the late Holocene, northwesterly winds have supported high production during both winter and spring seasons.

Sancetta, Constance

1995-02-01

175

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

SciTech Connect

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.

Huebner, S. [Department of Biochemistry and Molecular Biology, Nuclear Signalling Laboratory, PO Box 13D, Monash University, Clayton, Victoria 3800 (Australia)]. E-mail: stefan.huebner@med.monash.edu.au; Eam, J.E. [Department of Biochemistry and Molecular Biology, Nuclear Signalling Laboratory, PO Box 13D, Monash University, Clayton, Victoria 3800 (Australia); Huebner, A. [Department of Biochemistry and Molecular Biology, Nuclear Signalling Laboratory, PO Box 13D, Monash University, Clayton, Victoria 3800 (Australia); Jans, D.A. [Department of Biochemistry and Molecular Biology, Nuclear Signalling Laboratory, PO Box 13D, Monash University, Clayton, Victoria 3800 (Australia)

2006-01-15

176

The nuclear lamins: flexibility in function.  

PubMed

The nuclear lamina is an important structural determinant for the nuclear envelope as a whole, attaching chromatin domains to the nuclear periphery and localizing some nuclear envelope proteins. The major components of the lamina are the A-type and B-type lamins, which are members of the intermediate filament protein family. Whereas the expression of A-type lamins is developmentally regulated, B-type lamins, as a class, are found in all cells. The association of B-type lamins with many aspects of nuclear function has led to the view that these are essential proteins, and there is growing evidence suggesting that they regulate cellular senescence. However, B-type lamins are dispensable in certain cell types in vivo, and neither A-type nor B-type lamins may be required in early embryos or embryonic stem cells. The picture that is beginning to emerge is of a complex network of interactions at the nuclear periphery that may be defined by cell- and tissue-specific functions. PMID:23212477

Burke, Brian; Stewart, Colin L

2012-12-05

177

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

PubMed

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

Wang, Peili; Shen, Hong; Xie, Ping

2011-08-03

178

Analysis of nanoindentation response of diatom frustules.  

PubMed

Diatom frustules have been suggested for numerous nanotechnological applications. Experimental studies using nanoindenter have shown that the hardness and the stiffness of the frustules vary with location of indentation. To gain further insight, a computational framework has been developed where the Berkovich nanoindentation experiments were simulated by a rigid-deformable contact process. Three different approaches that provide progressively increasing level of understanding of the deformation behavior of frustules were adopted. The differences in the mechanical responses of the frustule due to variation of indentation location, size of pores, and distribution of pores were analyzed. It has been found that the effective stiffness of the frustule is linearly related to the porosity level and does not depend on the frustule size or its pore architecture. It has been shown that a 3D porous shell computational model is more appropriate to simulate the experimentally obtained mechanical response of diatom frustules. PMID:18283829

Yao, S; Subhash, G; Maiti, S

2007-12-01

179

Functionalization of the living diatom Thalassiosira weissflogii with thiol moieties.  

PubMed

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 (29)Si-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. PMID:24177724

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

2013-11-01

180

Molecular Tools for Discovering the Secrets of Diatoms  

NSDL National Science Digital Library

Diatoms are photosynthetic unicellular eukaryotes found in most aquatic environments. They are major players in global biogeochemical cycles, and generate as much oxygen through photosynthesis as terrestrial rainforests do. Insights into their evolutionary origins have been revealed by the whole-genome sequencing of Thalassiosira pseudonana and Phaeodactylum tricornutum. We now know that diatoms contain unusual assortments of genes derived from different sources, including those acquired by horizontal gene transfer from bacteria. These genes confer novel metabolic and signaling capacities that may underlie the extraordinary ecological success of diatoms on Earth today. The availability of a suite of techniques that can be used to monitor and manipulate diatom genes is enhancing our knowledge of their novel characteristics. We highlight these recent developments and illustrate how they are being used to understand different aspects of diatom biology. We also discuss the use of diatoms in commercial applications, such as for nanotechnology and biofuel production.

Anastasia Saade (ÃÂcole Normale Supérieure in Paris;Department of Biology); Chris Bowler (ÃÂcole Normale Supérieure in Paris;Department of Biology)

2009-10-01

181

Marine diatom biostratigraphy in Pacific Coast neogene basins  

SciTech Connect

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.

Barron, J.A.

1988-03-01

182

Woven ply thermoplastic laminates under severe conditions: Notched laminates and bolted joints  

Microsoft Academic Search

This work is aimed at investigating the influence of environmental conditions on the mechanical behavior of carbon fiber fabric reinforced PPS laminates. Changes in the strength and in the failure mechanisms of notched laminates and bolted joints were investigated for different environmental conditions: room temperature\\/dry – 120°C\\/hygrothermally aged. These conditions help enhance the ductile behavior of the PPS matrix but

Benoit Vieille; Jérémie Aucher; Lakhdar Taleb

2011-01-01

183

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

Microsoft Academic Search

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

S.. Huebner; J. E. Eam; A. Huebner; D. A. Jans

2006-01-01

184

Star Trek replicators and diatom nanotechnology  

Microsoft Academic Search

Diatoms are single celled algae, the 105–106 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

Ryan W. Drum; Richard Gordon

2003-01-01

185

Multiphoton Processes in Homopolar Diatomic Molecules  

Microsoft Academic Search

Within the framework of time-dependent perturbation theory and the Born-Oppenheimer approximation, general expressions are derived for the cross sections of multiphoton processes induced by radiation acting on a homopolar diatomic molecule. A Morse-type model of potential-energy curves of excited electronic states is proposed which gives a good representation of true curves. The procedure used to evaluate the sums over intermediate

F. V. Bunkin; I. I. Tugov

1973-01-01

186

Previously Unknown Virus Infects Marine Diatom  

PubMed Central

Diatoms are a major phytoplankton group that play important roles in maintaining oxygen levels in the atmosphere and sustaining the primary nutritional production of the aquatic environment. Among diatoms, the genus Chaetoceros is one of the most abundant and widespread. Temperature, climate, salinity, nutrients, and predators were regarded as important factors controlling the abundance and population dynamics of diatoms. Here we show that a viral infection can occur in the genus Chaetoceros and should therefore be considered as a potential mortality source. Chaetoceros salsugineum nuclear inclusion virus (CsNIV) is a 38-nm icosahedral virus that replicates within the nucleus of C. salsugineum. The latent period was estimated to be between 12 and 24 h, with a burst size of 325 infectious units per host cell. CsNIV has a genome structure unlike that of other viruses that have been described. It consists of a single molecule of covalently closed circular single-stranded DNA (ssDNA; 6,005 nucleotides), as well as a segment of linear ssDNA (997 nucleotides). The linear segment is complementary to a portion of the closed circle creating a partially double-stranded genome. Sequence analysis reveals a low but significant similarity to the replicase of circoviruses that have a covalently closed circular ssDNA genome. This new host-virus system will be useful for investigating the ecological relationships between bloom-forming diatoms and other viruses in the marine system. Our study supports the view that, given the diversity and abundance of plankton, the ocean is a treasury of undiscovered viruses.

Nagasaki, Keizo; Tomaru, Yuji; Takao, Yoshitake; Nishida, Kensho; Shirai, Yoko; Suzuki, Hidekazu; Nagumo, Tamotsu

2005-01-01

187

FINE STRUCTURE OF A DIATOM CENTROSOME.  

PubMed

The centrosome of the diatom Surirella ovalis is a dense spherical structure 500 mmicro in diamneter with filaments 15 mmicro in diamneter connected to it. The interior is filled with uniform granules but does not contain a typical centriole or clear area. The filaments emanating from it resemble the filaments of the mitotic apparatus, but they are present during interphase and appear to terminate at pores in the nuclear envelope. PMID:14057356

DRUM, R W; PANKRATZ, H S

1963-10-01

188

Role of silicon in diatom metabolism  

Microsoft Academic Search

1.In silicic acid-starved cells of the diatom Nitzschia alba, 68Ge(OH)4 is transported against a concentration gradient, leading to intracellular concentrations of germanic acid up to 3500 times greater than the exogenous concentrations. The accumulated substrate is osmotically active, as determined by its efflux into germanic acid-free medium.2.Metabolic energy is required for Ge(OH)4 transport, since uptake is completely inhibited by 1

Farooq Azam; Benjamin E. Volcani

1974-01-01

189

Photodissociation Imaging of Diatomic Sulfur (S2)  

Microsoft Academic Search

The photodissociation of diatomic sulfur, S2, in the region of the first dissociation limit is studied with velocity map imaging. Correlated fine structure distributions P(J1,J2) for the two S(3PJ) fragments are determined at selected photolysis wavelengths. Image analysis of the speed distributions of the atomic fragments following product-state-specific detection results in a revision of the bond energy to D0 )

Pim W. J. M. Frederix; Chung-Hsin Yang; Gerrit C. Groenenboom; David H. Parker; K. Alnama; Andrew J. Orr-Ewing

2009-01-01

190

Treating laminitis: beyond the mechanics of trimming and shoeing.  

PubMed

Laminitis is typically classified into developmental or prodromal, acute, subacute, and chronic phases. Scientific evidence regarding the pathophysiology of laminitis does exist, but it is often conflicting and dependent on the clinician's interpretation/understanding of the study or the model used for inducing laminitis. The diagnosis of laminitis consists of obtaining an accurate history, performing a thorough physical examination, and taking good-quality radiographs. The use of radiographs for diagnosis and interpretation of laminitis is an absolute necessity for the clinician. Laminitis is one disease that requires the assembly of a team consisting of the veterinarian, the farrier, and the owner to be successfully treated. PMID:22981200

Baker, William R

2012-08-01

191

Diatom Cells Grown and Baked on a Functionalized Mica Surface  

Microsoft Academic Search

We demonstrate the cultivation of diatom cells on a functionalized mica surface and the preparation of frustules on a mica\\u000a surface by baking. Diatom cells were successfully grown on a mica surface treated with 3-aminopropyltriethoxysilane. After\\u000a baking at 400?C for 2 h, frustule structures without the organic components of the diatom cells were successfully observed\\u000a by scanning electron microscopy and atomic

Kazuo Umemura; Yusuke Noguchi; Takuya Ichinose; Yo Hirose; Reiko Kuroda; Shigeki Mayama

2008-01-01

192

Diatoms accompanying vivianite from the Auckland Province (Note)  

Microsoft Academic Search

Organic matter occurs intimately associated with authigenic vivianite deposits in the Auckland Province, New Zealand. Where macroscopic organic debris is absent, diatoms have been found to be present.

Grant Henderson; Kerry Rodgers; Vivienne Cassie

1983-01-01

193

Laminated Metal Composites by Infiltration  

NASA Astrophysics Data System (ADS)

We show that steel-magnesium alloy laminated metal composites (LMCs) can be produced by gas pressure infiltration of a liquid magnesium alloy between layers of stacked dimpled steel sheets. Resulting LMCs are amenable to subsequent warm rolling. The LMCs are free of pores or brittle intermetallics and feature, in the as-cast condition, metal layers of uniform thickness and spacing. The ultimate tensile strength of the as-cast LMCs, of 260 MPa, obeys the "rule-of-mixtures" (ROM). The uniform tensile elongation, of around 20 pct, makes the infiltrated LMC nearly as ductile as the bulk steel it contains, implying that the magnesium alloy in the as-cast LMCs has a substantially increased tensile ductility in comparison to its metallurgically equivalent bulk state. Rolling reduces the metal layer thicknesses, causes waviness in the interface, and makes the LMCs stronger but less ductile, by factors in the vicinity of 2 for both properties; the main cause for this is work hardening in the steel layers.

Çetin, Arda; Krebs, Jérôme; Durussel, Alexandre; Rossoll, Andreas; Inoue, Junya; Koseki, Toshihiko; Nambu, Shoichi; Mortensen, Andreas

2011-11-01

194

Thermal Buckling and Postbuckling of Symmetrically Laminated Composite Plates.  

National Technical Information Service (NTIS)

The paper discusses an investigation into thermal buckling and postbuckling of symmetrically laminated composite plates. In the study thermal buckling is investigated for laminates under two different simple support conditions, fixed and sliding. These la...

C. A. Meyers M. W. Hyer M. J. Shuart

1991-01-01

195

Stress Distributions in Fibre Reinforced Plastic Laminates under Simple Loadings.  

National Technical Information Service (NTIS)

Numerical examples are presented to illustrate the character of the stress distributions occurring in laminated plates of fiber reinforced plastics under simple plane loadings. Two types of laminates are considered: the first comprises equal numbers of la...

B. C. Hoskin B. Green

1973-01-01

196

Response of Automated TOW Placed Laminates to Stress Concentrations.  

National Technical Information Service (NTIS)

In this study, the response of laminates with stress concentrations is explored. Automated Tow Placed (ATP, also known as Fiber Placement) laminates are compared to conventional tape layup manufacturing. Previous tensile fracture tests on fiber placed lam...

D. S. Cairns L. B. Ilcewicz T. Walker

1993-01-01

197

Comparative Evaluation of Failure Analysis Methods for Composite Laminates.  

National Technical Information Service (NTIS)

Over the last three decades, there have been continuous efforts in developing failure criteria for unidirectional fiber composites and their laminates. Currently, there exist a large number of lamina failure criteria and laminate failure analysis methods....

1996-01-01

198

Bolted Joints in a Laminated Composite Strut Design Expert System.  

National Technical Information Service (NTIS)

A knowledge based expert system (for the design and analysis of composite laminated struts) is part of a composite design expert (CODEX) system that not only performs analysis and design of composite laminated plates and struts, but also assesses competin...

C. M. L. Wu

1990-01-01

199

Three Dimensional Inelastic Finite Element Analysis of Laminated Composites.  

National Technical Information Service (NTIS)

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 dimensiona...

M. P. Kamat O. H. Griffin

1980-01-01

200

Compositional and fluorescence characteristics of the giant diatom Ethmodiscus along a 3000 km transect (28°N) in the central North Pacific gyre  

NASA Astrophysics Data System (ADS)

The giant diatom Ethmodiscus was examined along an east-west transect at 28-30°N during 2002 and 2003 to determine if abundance, chemical composition or physiological status of this largest of diatoms varied on the scale of 100's-1000's of km in North Pacific gyre. Abundance ranged from <0.1->2.0 cells m -3 and supported the notion of an abundance mosaic reported previously. However, there was only minimal support for the relationship between abundance and nutrient concentration at 125 m reported previously. Cellular chlorophyll varied little along the transect (7.3-10.9 ng chl cell -1) except at the westernmost station. Cellular N and P quotas co-varied 3-4.5 fold (mean=50.8±3.7 and 3.7±0.8 nmol N and P cell -1) and yielded N:P ratios that closely clustered around the Redfield ratio (average=14.6±1.1). Only low levels of chlorophyll-normalized alkaline phosphatase (APase) activity were observed (0.4-2.5 nmol P ?g chl -1 h -1) with APase activity lower than that in either the bulk water, or co-occurring Trichodesmium spp. and Pyrocystis noctiluca. The active fluorescence parameter Fv: Fm, a property sensitive to Fe stress, was uniformly high at all stations (average=0.73±0.04 for 2003, and 0.69±0.05 for 2002), indicating sufficient Fe for optimum photosynthetic competence. These results contrasted sharply with results from Rhizosolenia mats reported along the same transect where there was a significant decline westward in Fv: Fm. Both ferredoxin (Fd) and flavodoxin accumulated in cells of Ethmodiscus, resulting in Fd Index values of<0.6. Iron cell quotas ranged from 0.7-5.1 pmol Fe cell -1. When normalized to cytoplasmic volume, the Fe ?m -3 was comparable to that of Escherichia coli. We note that the disproportionate contribution of the vacuole (with its high organic content) to total volume typical of large diatoms is a potentially significant source of error in Fe:C ratios and suggest that Fe should be normalized to cytoplasmic volume whenever possible to permit valid intercomparisons between studies. The composition, Fv: Fm data and Fe:C ratio suggest a relatively uniform population experiencing little N, P or Fe stress. The uncoupling of the Fd Index from these measures is consistent with previous findings showing that the expression of flavodoxin can be characterized as an early stress response and that its accumulation is not necessarily correlated with physiological deficit. Ethmodiscus appears to be well adapted to some of the most oligotrophic waters in the ocean. Because it is an important sedimentary marker, the biology of living Ethmodiscus provides insights into the source of extensive Ethmodiscus oozes. Mass sedimentation after frontal accumulation has been suggested as a source for these oozes. Our data contain no evidence that the flux is linked directly to Fe, N or P stress.

Villareal, Tracy A.; McKay, R. M. L.; Al-Rshaidat, M. M. D.; Boyanapalli, R.; Sherrell, R. M.

2007-08-01

201

Fracture behavior of laminated discontinuously reinforced aluminum material  

SciTech Connect

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.

Osman, T.M. [Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Materials Science and Engineering]|[Lawrence Livermore National Lab., CA (United States); Lewandowski, J.J. [Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Materials Science and Engineering; Lesuer, D.R.; Syn, C.K. [Lawrence Livermore National Lab., CA (United States); Hunt, W.H. Jr [Aluminum Co. of America, Alcoa Center, PA (United States). Alcoa Technical Center

1994-05-01

202

Progressive damage and fracture of laminated glass beams  

Microsoft Academic Search

The use of laminated glass is increasing due to the realization of transparent load-bearing elements for architectural glazing applications. In laminated glass, two or more layers of glass are bonded to thin thermoplastic interlayers to improve the post-breakage characteristics of the glass. After breakage, the residual load-carrying capacity of the laminate depends on the mechanical properties of the laminate constituents.

Luigi Biolzi; Sara Cattaneo; Gianpaolo Rosati

2010-01-01

203

Damage initiation and propagation in metal laminates  

SciTech Connect

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.

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

1996-07-26

204

Nuclear Actin and Lamins in Viral Infections  

PubMed Central

Lamins are the best characterized cytoskeletal components of the cell nucleus that help to maintain the nuclear shape and participate in diverse nuclear processes including replication or transcription. Nuclear actin is now widely accepted to be another cytoskeletal protein present in the nucleus that fulfills important functions in the gene expression. Some viruses replicating in the nucleus evolved the ability to interact with and probably utilize nuclear actin for their replication, e.g., for the assembly and transport of capsids or mRNA export. On the other hand, lamins play a role in the propagation of other viruses since nuclear lamina may represent a barrier for virions entering or escaping the nucleus. This review will summarize the current knowledge about the roles of nuclear actin and lamins in viral infections.

Cibulka, Jakub; Fraiberk, Martin; Forstova, Jitka

2012-01-01

205

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

Microsoft Academic Search

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

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

2009-01-01

206

Fracture Mechanics of Sublaminate Cracks in Composite Laminates.  

National Technical Information Service (NTIS)

This paper presents an overview of a fracture mechanics approach to some of the most frequently encountered matrix-dominated, sub-laminate cracks in epoxy-based composite laminates. By 'sub-laminate', it is meant that the cracks are internal to the lamina...

A. S. D. Wang

1983-01-01

207

Characterization of Wave Propagation in Thin Laminated Plates  

Microsoft Academic Search

The formulae including the in-plane stiffness and bending stiffness coefficients and coupling effect in out-plane were presented for analyzing characterization of wave propagation. Using the present formulae, the wave velocities can be calculated in any case of laminated plates including nonsymmetric lamination. In this study, the characteristics of wave propagation in thin laminated plates were investigated in detail. Five modes

Chao Du; Qing-Qing Ni; Toshiaki Natsuki

2010-01-01

208

Development and characterization of ceramic fibre-polyester laminates  

Microsoft Academic Search

Ceramic fibre waste generated during the production of ceramic fibres has been utilized for the development of laminates. The effect of resin to fibre ratio, concentration of catalyst and comonomer and process parameters have been studied. Various physico-mechanical properties of the laminates have been determined and comparative evaluation with commercially available fibre glass decorative laminates and gypsum board has been

M. Q. Parwez; Khursheed Fatma; S. K. Maiti; R. K. Khandal

2002-01-01

209

Fracture behavior of laminated discontinuously reinforced aluminum material  

Microsoft Academic Search

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

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

1994-01-01

210

A mathematical model for the behavior of laminated glass beams  

Microsoft Academic Search

Two-ply laminated architectural glass used in automotive industry since 1914, now become an important element in construction industry as well. Regarding its importance, a theoretical model is needed for the laminated glass beams investigated mostly experimentally so far. In this paper, a mathematical model for the behavior of laminated glass beams is introduced. The minimum total potential energy principle is

Mehmet Zülfü A??k; Selim Tezcan

2005-01-01

211

Stresses in laminated glass subject to low velocity impact  

Microsoft Academic Search

Finite element analysis is used to study small, low velocity missile impact of laminated architectural glass. The impact situation models that commonly observed during severe windstorms in which small, hard missiles impact laminated glass windows in large buildings. Architectural laminated glass is typically made of two soda-lime glass plies separated by a clear, sticky, polyvinyl butyral (PVB) interlayer. In order

F. W. Flocker; L. R. Dharani

1997-01-01

212

Copepod hatching success in marine ecosystems with high diatom concentrations  

Microsoft Academic Search

Diatoms dominate spring bloom phytoplankton assemblages in temperate waters and coastal upwelling regions of the global ocean. Copepods usually dominate the zooplankton in these regions and are the prey of many larval fish species. Recent laboratory studies suggest that diatoms may have a deleterious effect on the success of copepod egg hatching. These findings challenge the classical view of marine

Xabier Irigoien; Roger P. Harris; Hans M. Verheye; Pierre Joly; Jeffrey Runge; Michel Starr; David Pond; Robert Campbell; Rachael Shreeve; Peter Ward; Amy N. Smith; Hans G. Dam; William Peterson; Valentina Tirelli; Marja Koski; Tania Smith; Derek Harbour; Russell Davidson

2002-01-01

213

Diatom survivorship in ballast water during trans-Pacific crossings  

Microsoft Academic Search

Ship ballast water is believed to be responsible for global dispersal of alien biota; mid- ocean ballast water exchange is most commonly used to mitigate this process. Diatoms are among the most abundant biotic-component in ballast water, yet their invasive biology is poorly understood. To test effectiveness of MOE we examined diatom species composition and cell density in two sets

Georgia Klein; Kayleigh MacIntosh; Irena Kaczmarska; James M. Ehrman

2009-01-01

214

Molecular Fossils as Time Indicators for the Evolution of Diatoms  

Microsoft Academic Search

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

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

2004-01-01

215

Diatom aggregation in the sea: mechanisms and ecological implications  

Microsoft Academic Search

Marine snow is a ubiquitous feature of the ocean and an important agent in the transport of energy and nutrients through marine ecosystems. Diatom aggregates, which form during blooms and, to a lesser extent, by the resuspension of benthic biofilms, are a primary source of marine snow. Genera commonly found in diatom aggregates are: Nitzschia, Chaetoceros, Rhizosolenia, Leptocylindricus, Skeletonema and

2002-01-01

216

Diatoms respire nitrate to survive dark and anoxic conditions  

PubMed Central

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 11–274 mM NO3? 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 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.

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

2011-01-01

217

A palaeolimnological assessment of diatom production responses to lake acidification.  

PubMed

To quantify diatom palaeoproduction responses to lake acidification, a whole-basin diatom accumulation rate was calculated for the small acidified lake Gaffeln, in the Gårdsjön catchment in south-west Sweden. Changes in the relative frequency of diatom assemblages to acidification were typical of other lakes in the area, notably a decline in planktonic diatoms after approximately 1900 and increase in acid-tolerant benthic species (e.g. Eunotia spp. and Tabellaria binalis). Single deep-water cores could be used to infer past changes in diatom production because of changed sediment-microfossil deposition patterns, probably due to the development of a benthic algal mat in the littoral zone. The basin mean total diatom accumulation rate (based on eight cores) was approximately constant over the last 150 years, while planktonic diatoms decreased from 0.3 x 10(6) frustules cm(-2) year(-1) prior to 1900 to trace levels in the 1970s. There was, however, a corresponding increase in the accumulation of benthic diatoms over the same period, from 0.5 to 1 x 10(6) frustules cm(-2) year(-1) between 1950 and the present, together with changed community structure. The increase in benthic species probably reflects an expansion of the littoral zone as light transparency increased. PMID:15091936

Anderson, N J; Renberg, I

1992-01-01

218

Adhesion and motility of fouling diatoms on a silicone elastomer  

Microsoft Academic Search

Recent demands for non-toxic antifouling technologies have led to increased interest in coatings based on silicone elastomers that ‘release’ macrofouling organisms when hydrodynamic conditions are sufficiently robust. However, these types of coatings accumulate diatom slimes, which are not released even from vessels operating at high speeds ( > 30 knots). In this study, adhesion strength and motility of three common fouling diatoms

R Holland; T M Dugdale; R Wetherbee; A B Brennan; J A Finlay; J A Callow; Maureen E Callow

2004-01-01

219

Analytic Quantum Mechanics of Diatomic Molecules with Empirical Potentials  

Microsoft Academic Search

The Schrödinger equations of diatomic molecules with empirical potential functions are solved approximately by means of the hypergeometric series method. The potential functions may fit the experimental Rydberg-Klein-Rees curve more closely than the Morse function. Rigorous solutions of Schrödinger equations are also obtained with a similar method for zero total angular momentum. The eigenfunctions of diatomic molecules, expressed in terms

Jun Lu

2005-01-01

220

Gene silencing in the marine diatom Phaeodactylum tricornutum  

Microsoft Academic Search

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 endo- symbionts, 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

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

2009-01-01

221

Modified Ribose Receptor Response in Isolated Diatom Frustules.  

National Technical Information Service (NTIS)

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 s...

C. R. Fairbanks

2011-01-01

222

Chitin in Diatoms and Its Association with the Cell Wall ? †  

PubMed Central

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.

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

2009-01-01

223

Diatom frustules as light traps enhance DSSC efficiency.  

PubMed

Diatoms are one of the most successful photosynthetic organisms and given the important role that their shells (frustules) play in light trapping we explored their use in multilayered materials for application as photoanodes in dye sensitised solar cells (DSSCs). We find a substantial improvement in energy conversion efficiency of 30%, increasing from 3.5% to 4.6% with diatom incorporation. PMID:23152116

Toster, Jeremiah; Iyer, K Swaminathan; Xiang, Wanchun; Rosei, Federico; Spiccia, Leone; Raston, Colin L

2012-11-15

224

Carbohydrate metabolism in the marine diatom Skeletonema costatum  

Microsoft Academic Search

This is a study on the metabolism of the algal biochemical constituents of a marine diatom, Skeletonema costatum. The carbohydrates, protein, and lipid, of the diatom grown under light and dark conditions were analyzed. The composition of the organic compounds did not vary in the alga grown under continuous light conditions throughout the experiment, although a little accumulation of carbohydrate

N. Handa

1969-01-01

225

Lake warming favours small-sized planktonic diatom species  

PubMed Central

Diatoms contribute to a substantial portion of primary production in the oceans and many lakes. Owing to their relatively heavy cell walls and high nutrient requirements, planktonic diatoms are expected to decrease with climate warming because of reduced nutrient redistribution and increasing sinking velocities. Using a historical dataset, this study shows that diatoms were able to maintain their biovolume with increasing stratification in Lake Tahoe over the last decades; however, the diatom community structure changed. Increased stratification and reduced nitrogen to phosphorus ratios selected for small-celled diatoms, particularly within the Cyclotella genus. An empirical model showed that a shift in phytoplankton species composition and cell size was consistent within different depth strata, indicating that altered nutrient concentrations were not responsible for the change. The increase in small-celled species was sufficient to decrease the average diatom size and thus sinking velocity, which strongly influences energy transfer through the food web and carbon cycling. Our results show that within the diverse group of diatoms, small-sized species with a high surface area to volume ratio were able to adapt to a decrease in mixing intensity, supporting the hypotheses that abiotic drivers affect the size structure of planktonic communities and that warmer climate favours small-sized diatom cells.

Winder, Monika; Reuter, John E.; Schladow, S. Geoffrey

2008-01-01

226

Adiabatic Principles in Atom-Diatom Collisional Energy Transfer  

Microsoft Academic Search

This work describes the application of numerical methods to the solution of the time dependent Schrodinger 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

William John Hovingh

1993-01-01

227

Testing attachment point theory: diatom attachment on microtextured polyimide biomimics  

Microsoft Academic Search

This paper explores diatom attachment to a range of laser etched polyimide surfaces to directly test ‘attachment point theory’. Static bioassays were conducted on microtextured polyimide surfaces using four diatom species, Fallacia carpentariae, Nitzschia cf. paleacea, Amphora sp. and Navicula jeffreyi with cell sizes ranging from 1 – 14 ?m. The microtextured polyimides were modelled from natural fouling resistant bivalve surfaces and had

A. J. Scardino; E. Harvey; R. De Nys

2006-01-01

228

Do benthic and planktonic diatoms produce equivalent effects in crustaceans?  

Microsoft Academic Search

Hippolyte inermis Leach 1814 is a benthic shrimp characterized by a peculiar mechanism of sex reversal influenced by diatom foods. In fact, the appearance of primary females in spring is due to an apoptotic early disruption of the androgenic gland and of the male gonad, triggered by still unknown compounds present in diatoms of the genus Cocconeis. The influence of

Valerio Zupo; Patrizia Messina; Isabella Buttino; Amir Sagi; Conxita Avila; Michela Nappo; Jaume Bastida; Carles Codina; Simonetta Zupo

2007-01-01

229

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...

230

Biogeochemistry of silica in Devils Lake: implications for diatom preservation  

Microsoft Academic Search

Diatom-salinity records from sediment cores have been used to construct climate records of saline-lake basins. In many cases, this has been done without thorough understanding of the preservation potential of the diatoms in the sediments through time. The purpose of this study was to determine the biogeochemistry of silica in Devils Lake and evaluate the potential effects of silica cycling

Robert M. Lent; Berry Lyons

2001-01-01

231

The Phaeodactylum genome reveals the evolutionary history of diatom genomes.  

PubMed

Diatoms are photosynthetic secondary endosymbionts found throughout marine and freshwater environments, and are believed to be responsible for around one-fifth of the primary productivity on Earth. The genome sequence of the marine centric diatom Thalassiosira pseudonana was recently reported, revealing a wealth of information about diatom biology. Here we report the complete genome sequence of the pennate diatom Phaeodactylum tricornutum and compare it with that of T. pseudonana to clarify evolutionary origins, functional significance and ubiquity of these features throughout diatoms. In spite of the fact that the pennate and centric lineages have only been diverging for 90 million years, their genome structures are dramatically different and a substantial fraction of genes ( approximately 40%) are not shared by these representatives of the two lineages. Analysis of molecular divergence compared with yeasts and metazoans reveals rapid rates of gene diversification in diatoms. Contributing factors include selective gene family expansions, differential losses and gains of genes and introns, and differential mobilization of transposable elements. Most significantly, we document the presence of hundreds of genes from bacteria. More than 300 of these gene transfers are found in both diatoms, attesting to their ancient origins, and many are likely to provide novel possibilities for metabolite management and for perception of environmental signals. These findings go a long way towards explaining the incredible diversity and success of the diatoms in contemporary oceans. PMID:18923393

Bowler, Chris; Allen, Andrew E; Badger, Jonathan H; Grimwood, Jane; Jabbari, Kamel; Kuo, Alan; Maheswari, Uma; Martens, Cindy; Maumus, Florian; Otillar, Robert P; Rayko, Edda; Salamov, Asaf; Vandepoele, Klaas; Beszteri, Bank; Gruber, Ansgar; Heijde, Marc; Katinka, Michael; Mock, Thomas; Valentin, Klaus; Verret, Fréderic; Berges, John A; Brownlee, Colin; Cadoret, Jean-Paul; Chiovitti, Anthony; Choi, Chang Jae; Coesel, Sacha; De Martino, Alessandra; Detter, J Chris; Durkin, Colleen; Falciatore, Angela; Fournet, Jérome; Haruta, Miyoshi; Huysman, Marie J J; Jenkins, Bethany D; Jiroutova, Katerina; Jorgensen, Richard E; Joubert, Yolaine; Kaplan, Aaron; Kröger, Nils; Kroth, Peter G; La Roche, Julie; Lindquist, Erica; Lommer, Markus; Martin-Jézéquel, Véronique; Lopez, Pascal J; Lucas, Susan; Mangogna, Manuela; McGinnis, Karen; Medlin, Linda K; Montsant, Anton; Oudot-Le Secq, Marie-Pierre; Napoli, Carolyn; Obornik, Miroslav; Parker, Micaela Schnitzler; Petit, Jean-Louis; Porcel, Betina M; Poulsen, Nicole; Robison, Matthew; Rychlewski, Leszek; Rynearson, Tatiana A; Schmutz, Jeremy; Shapiro, Harris; Siaut, Magali; Stanley, Michele; Sussman, Michael R; Taylor, Alison R; Vardi, Assaf; von Dassow, Peter; Vyverman, Wim; Willis, Anusuya; Wyrwicz, Lucjan S; Rokhsar, Daniel S; Weissenbach, Jean; Armbrust, E Virginia; Green, Beverley R; Van de Peer, Yves; Grigoriev, Igor V

2008-10-15

232

Investigation of Phosphorus Uptake Capability in the Diatom Didymosphenia geminata  

Microsoft Academic Search

Abstract Didymosphenia geminata , commonly known as Didymo, is a species of diatom that thrives in a variety of waters worldwide but has been especially observed in cold, shallow, nutrient poor waters. Didymo has been observed growing in Rapid Creek in South Dakota at an increasing rate over the past few years ,. The diatom is considered an invasive species

Kyle Maurer

233

Late Neogene changes in diatom sedimentation in the North Pacific  

USGS Publications Warehouse

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.

Barron, J. A.

1998-01-01

234

Diatoms respire nitrate to survive dark and anoxic conditions.  

PubMed

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

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

2011-03-14

235

Diatomic Analytic Molecular Partition Functions for Stellar Atmospheres  

NASA Astrophysics Data System (ADS)

Approximate partition functions and their derivatives for diatomic molecules are formulated taking into account the finite number of levels. A procedure is developed to derive compact analytic expressions, without free parameters, necessary for the efficient evaluation of some thermodynamic coefficients from the partition functions for diatomic molecules useful in modeling low temperature stellar atmospheres.

Cardona, O.; Corona-Galindo, M. G.

2013-10-01

236

Ultrasonic transducer with laminated coupling wedge  

DOEpatents

An ultrasonic transducer capable of use in a high-temperature environment incorporates a laminated metal coupling wedge including a reflecting edge shaped as a double sloping roof and a transducer crystal backed by a laminated metal sound absorber disposed so as to direct sound waves through the coupling wedge and into a work piece, reflections from the interface between the coupling wedge and the work piece passing to the reflecting edge. Preferably the angle of inclination of the two halves of the reflecting edge are different.

Karplus, Henry H. B. (Hinsdale, IL)

1976-08-03

237

Prescribing diatom morphology: toward genetic engineering of biological nanomaterials.  

PubMed

The formation of inorganic materials with complex form is a widespread biological phenomenon (biomineralization). Among the most spectacular examples of biomineralization is the production by diatoms (a group of eukaryotic microalgae) of intricately nanopatterned to micropatterned cell walls made of silica (SiO2). Understanding the molecular mechanisms of diatom silica biomineralization is not only a fundamental biological problem, but also of great interest in materials engineering, as the biological self-assembly of three-dimensional (3D) inorganic nanomaterials has no man-made analog. Recently, insight into the molecular mechanism of diatom silica formation has been obtained by structural and functional analysis of biomolecules that are involved in this process. Furthermore, the rapid development of diatom molecular genetics has provided new tools for investigating the silica forming machinery of diatoms and for manipulating silica biogenesis. This has opened the door for the production, through genetic engineering, of unique 3D nanomaterials with designed structures and functionalities. PMID:17991447

Kröger, Nils

2007-11-26

238

Regulated growth of diatom cells on self-assembled monolayers  

PubMed Central

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.

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

2007-01-01

239

First evidence for the existence of pennate diatom viruses  

PubMed Central

Diatoms are considered the most successful and widespread group of photosynthetic eukaryotes. Their contribution to primary production is remarkably significant to the earth's ecosystems. Diatoms are composed of two orders: Centrales and Pennales. Thus far, viruses infecting centric diatom species have been isolated and characterized; however, viruses infecting pennates have not been reported. Here, we describe the first isolations and preliminary characterizations of two distinct pennate diatom viruses, AglaRNAV (31?nm in diameter, accumulates in the host cytoplasm) and TnitDNAV (35?nm in diameter, accumulates in the host nuclei) infecting Asterionellopsis glacialis and Thalassionema nitzschioides, respectively. Their genomes contain a single-stranded RNA of approximately 9.5?kb, and a closed, circular single-stranded DNA of approximately 5.5?kb harboring a partially double-stranded region, respectively. Further analysis of these viruses may elucidate many aspects of diatom host–virus relationships.

Tomaru, Yuji; Toyoda, Kensuke; Kimura, Kei; Hata, Naotsugu; Yoshida, Mikihide; Nagasaki, Keizo

2012-01-01

240

Fluorescence correlation spectroscopy to study diffusion through diatom nanopores.  

PubMed

The intricate pore architecture of diatom frustules has been extensively studied mainly as the basis of diatom classification. There have, however, been very few reports on understanding the effect of the pore architecture on the movement of molecules through the pores. Information on molecular transport though diatom membrane pores has the potential to help develop more efficient membrane filtration systems. In this paper the transport of molecules through individual diatom nanopores is investigated. Fluorescence correlation spectroscopy (FCS) is used to determine diffusion coefficients. Thus, for the very first time, we measure the effect of the three dimensional pore structure of the diatom Coscinodiscus wailesii, on the mean diffusion coefficient through the pores. The results show almost a 50% decrease in the diffusion coefficient relative to that in the free solution. PMID:19908596

Bhatta, Hemant; Enderlein, Jörg; Rosengarten, Gary

2009-11-01

241

Biotemplated diatom silica-titania materials for air purification.  

PubMed

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

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

2013-04-01

242

Carbene-stabilized main group diatomic allotropes.  

PubMed

While transition metals are well known for assuming the formal oxidation state of zero in various compounds main group elements have rarely engaged in this practice. Recent reports of N-heterocyclic carbene-stabilized main group diatomic allotropes (i.e., Si(2), Ge(2), P(2), As(2)) denote a breakthrough of zero-oxidation state main group chemistry. This Perspective addresses the synthesis and characterization of these highly reactive main group molecules, with a particular emphasis on the very recent progress in the reactivity study of carbene-stabilized Si(2) and P(2). PMID:21904737

Wang, Yuzhong; Robinson, Gregory H

2011-09-09

243

Periodic Traveling Waves in Diatomic Granular Chains  

NASA Astrophysics Data System (ADS)

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.

Betti, Matthew; Pelinovsky, Dmitry E.

2013-10-01

244

Three dimensional thermal stresses in angle-ply composite laminates  

SciTech Connect

The room temperature stress distributions and shapes of a family of angle ply graphite/epoxy laminates have been obtained using a three-dimensional linear finite element analysis. The sensitivity of the corners to fiber angle variations is examined, in addition to the errors introduced by assuming planes of symmetry which do not exist in angle-ply laminates. The results show that angle ply laminates with clustered plies will tend to delaminate at diagonally opposite corners, and that matrix cracks in this family of laminates will be initiated in the laminate interior. 20 references.

Griffin, O.H. Jr.

1988-01-01

245

Strength and flaw elimination assessment in tape cast ceramic laminates  

SciTech Connect

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.

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

1992-10-01

246

Modelling diatom growth in turbulent waters.  

PubMed

Algal models used as tools in the management of algal blooms may be inaccurate because representation of mixing processes is often oversimplified. A testable 3-D algal model for prediction of algal growth in turbulent surface waters was developed based on the Eulerian water quality model, HYDRO-3D. Out-door mesocosm experiments on the growth of the diatom Skeletonema costatum showed no evidence that diatom growth is significantly affected by light/dark fluctuations brought about by turbulent mixing, and no direct effects of turbulence on phytoplankton physiology were required in the algal model. The algal model was successfully calibrated and validated against mesocosm data and field data from Poplar Dock, London Docklands. Application of the model gave credible results for the hypothetical growth of S. costatum in Poplar Dock under a wide range of wind speeds and surface irradiances. However, differences between the results of a full 3-D simulation and a simplified 1-D representation of Poplar Dock were minimal, and no clear conclusions could be drawn on the superiority of 3-D models over 1-D models for simulation of complex flows in natural water bodies. PMID:15207602

Patel, Dipen; Guganesharajah, K; Thake, Brenda

2004-06-01

247

Variation in morphology with serial dissolution of common Southern Ocean diatoms  

Microsoft Academic Search

Diatoms play a key role in silica cycling in nearly all environments capable of biological activity, and the sedimentary record of diatom production is altered by variable preservation over space and time. Diatom frustule preservation is poorly understood, and no test currently exists for determining the amount of silica leached from a water column or sedimentary diatom sample. In order

J. Warnock; R. Scherer

2009-01-01

248

Genome size differentiates co-occurring populations of the planktonic diatom Ditylum brightwellii (Bacillariophyta)  

Microsoft Academic Search

BACKGROUND: Diatoms are one of the most species-rich groups of eukaryotic microbes known. Diatoms are also the only group of eukaryotic micro-algae with a diplontic life history, suggesting that the ancestral diatom switched to a life history dominated by a duplicated genome. A key mechanism of speciation among diatoms could be a propensity for additional stable genome duplications. Across eukaryotic

Julie A Koester; Jarred E Swalwell; Peter von Dassow; E Virginia Armbrust

2010-01-01

249

The roles of environment and space in shaping stream diatom communities  

Microsoft Academic Search

Diatoms are widely used in stream quality assessment due to their response to the local environment. Diatoms are also influenced by many large-scale processes and so the diatom communities of boreal streams incorporate a strong spatial component at a regional level. What is not properly known yet is whether the variation in diatom communities between regions is larger than the

Laura Virtanen; Janne Soininen

2012-01-01

250

Quantitative evidence concerning the stabilization of sediments by marine benthic diatoms  

Microsoft Academic Search

Six species of benthic diatoms and a natural benthic diatom community were cultured in flasks on a variety of sediments. Diatom species which secreted large quantities of mucilage were effective sediment stabilizers. These mucilage-secreting species significantly reduced resuspension and retarded laminar flow of the sediments when the culture flasks were agitated. Diatom species which secreted little or no mucilage were

A. F. Holland; R. G. Zingmark; J. M. Dean

1974-01-01

251

Laminate analogy for composites enhanced concrete structures  

Microsoft Academic Search

A new and effective method is described to design composites to repair damage or enhance the overload strength of concrete infrastructures. The method is based on laminate analogy which is derivable from composite mechanics and available in computer codes. It is used to simulate structural sections made from reinforced concrete which are typical in infrastructures as well as select reinforced

C. C. Chamis; P. K. Gotsis

1997-01-01

252

Kerto-Laminated Veneer Lumber Truss.  

National Technical Information Service (NTIS)

Kerto laminated veneer lumber truss is a long span roof header. Members of Kerto-LVL-truss are all constructed of two separate Kerto-LVL-members which are joined together with twin grip plates, a joint method especially developed for this purpose. All mem...

J. Kalliomaeki H. Hirsi P. Kanerva

1987-01-01

253

Property Optimisation in Fibre Metal Laminates  

Microsoft Academic Search

Fibre Metal Laminates (FMLs) are hybrid materials, which consist of thin metal sheets bonded together with alternating unidirectional fibre layers. This material concept has resulted in superior fatigue characteristics with respect to the metallic counterpart. Several static characteristics (specifically tension, shear, bearing, blunt and sharp notch behaviour) are however negatively influenced due to the fibre addition. This paper investigates the

R. van Rooijen; J. Sinke; T. J. De Vries; S. van der Zwaag

2004-01-01

254

Guided waves in laminated isotropic circular cylinder  

Microsoft Academic Search

This paper investigates, analytically and numerically, the dispersion characteristics of a laminated isotropic circular cylinder. The propagator matrix, which relates the stresses and displacements of one interface of a layer to those of another interface, is formulated based upon the three-dimensional theory of elasticity. The dispersion relation of the cylinder is implicitly established from this propagator matrix. The numerical evaluation

N. Rattanawangcharoen; A. H. Shah

1992-01-01

255

Integration of sensing networks into laminated composites  

Microsoft Academic Search

We summarize the methodology that we have used to address integrating sensing network into composite materials for structural self diagnosis. First, we have examined the effect of stress concentration that arises due to the embedment of sensors and external devices on the strength and endurance of laminated glass fiber composites. To analyze the mechanical response of the composite material under

Fabrizia Ghezzo; Patrick Rye; Yi Huang; Sia Nemat-Nasser

2008-01-01

256

Asymptotic homogenization of laminated piezocomposite materials  

Microsoft Academic Search

The objective of this paper is to apply the technique of asymptotic homogenization to determine the effective elastic, piezoelectric and dielectric moduli of a laminated piezocomposite medium with a periodic structure. Each periodic cell of the medium can possess any finite number of piezoelectric layers. The general formulae obtained are a generalization of those that appear in chapter 5 of

Alain Bourgeat

1998-01-01

257

Synthetic multifunctional metallic-intermetallic laminate composites  

Microsoft Academic Search

The field of material microstructure design targeted for a specific set of structural and functional properties is now a recognized field of focus in materials science and engineering. This paper describes a new class of structural materials called metallic-intermetallic laminate (MIL) composites, which can have their micro-, meso- and macrostructure designed to achieve a wide array of material properties and

Kenneth S. Vecchio

2005-01-01

258

Finite element modelling of architectural laminated glass  

Microsoft Academic Search

Laminated glass (LG) comprises two or more glass plates bonded together with elastomeric interlayer. Automobile and aircraft industries have used LG for years because of its ability to maintain closure of window openings following fracture. In the last decade, the architectural industry began to utilise the potential of LG as the best glazing material for building fenestrations that might experience

M. M. El-Shami; H. S. Norville

2011-01-01

259

Elastic Wave Dispersion in Laminated Composite Plate,  

National Technical Information Service (NTIS)

In this paper we use the stiffness method that was presented in to study dispersion of waves in a laminated plate. In this approach each lamina is divided into several sublayers and the displacement distribution through the thickness of each sublayer is a...

S. K. Datta A. H. Shah Y. Al-Nassar R. L. Bratton

1987-01-01

260

Laminated Root Rot in Western North America.  

National Technical Information Service (NTIS)

Laminated root rot, caused by Phellinus weirii (Murr.) Gib., is a serious root disease affecting Douglas-fir and other commercially important species of conifers in northwestern North America. This report gives an overview of the disease as it occurs in t...

W. G. Thies R. N. Sturrock

1995-01-01

261

Tevatron I: Large Bore Quad lamination analysis  

SciTech Connect

Stacking, compression, and welding of the laminations for the TeV I Large Bore Quad results in a deformation due to springback which is unacceptable due to magnetic field requirements. ANSYS has been used to analyze a solution to this problem.

Leininger, M.

1982-10-26

262

Laminated insulators having heat dissipation means  

DOEpatents

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.

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

1980-04-24

263

Doped LZO buffer layers for laminated conductors  

SciTech Connect

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.

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

264

A unified theory for laminated plates  

Microsoft Academic Search

A literature survey on plate and beam theories show how the advent of the finite element method and the variational method circa 1940 have been a great stimulant for the research in this field. The initial thin plate formulation has been incrementally expanded to treat the isotropic thick plate, the anisotropic single layer, and then laminated plates. It appears however

Irene Guiamatsia Tafeuvoukeng

2007-01-01

265

Ultrasonic monitoring of asymmetric carbon fibre reinforced aluminum laminates  

NASA Astrophysics Data System (ADS)

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.

Zhao, Junqing; Yang, Fan; Wang, Rongguo

2013-08-01

266

Copepod Population-Specific Response to a Toxic Diatom Diet  

PubMed Central

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.

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

2012-01-01

267

Unicellular C4 photosynthesis in a marine diatom.  

PubMed

Nearly 50 years ago, inorganic carbon was shown to be fixed in microalgae as the C3 compound phosphoglyceric acid. The enzyme responsible for C3 carbon fixation, ribulose-1,5-bisphosphate carboxylase (Rubisco), however, requires inorganic carbon in the form of CO2 (ref. 2), and Rubisco enzymes from diatoms have half-saturation constants for CO2 of 30-60 microM (ref. 3). As a result, diatoms growing in seawater that contains about 10 microM CO2 may be CO2 limited. Kinetic and growth studies have shown that diatoms can avoid CO2 limitation, but the biochemistry of the underlying mechanisms remains unknown. Here we present evidence that C4 photosynthesis supports carbon assimilation in the marine diatom Thalassiosira weissflogii, thus providing a biochemical explanation for CO2-insensitive photosynthesis in marine diatoms. If C4 photosynthesis is common among marine diatoms, it may account for a significant portion of carbon fixation and export in the ocean, and would explain the greater enrichment of 13C in diatoms compared with other classes of phytoplankton. Unicellular C4 carbon assimilation may have predated the appearance of multicellular C4 plants. PMID:11069177

Reinfelder, J R; Kraepiel, A M; Morel, F M

2000-10-26

268

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

USGS Publications Warehouse

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.

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

1999-01-01

269

Diatom auxospore scales and early stages in diatom frustule morphogenesis: their potential for use in nanotechnology.  

PubMed

Incomplete, forming diatom cell wall components have potential uses in nanotechnology that differ from those of mature frustules. Diminutive, discoid auxospore scales, produced after sexual reproduction, could also be evaluated for their value. The structure of developing diatom valves and girdle bands is generally simple, since features such as cribra and other ornamentation have yet to be added. They are also more lightly silicified. Bullulae and honeycomb structures give strength to the final framework of some species using a minimal amount of silica. The morphogenesis of girdle bands is shown to be unidirectional in a marine centric species, forming open-ended cylinders, another potential shape for the arsenal of structures useful to nanotechnologists. PMID:15762171

Tiffany, Mary Ann

2005-01-01

270

Surface-enhanced Raman scattering on diatom biosilica photonic crystals  

NASA Astrophysics Data System (ADS)

Diatoms are a group of single-celled photosynthetic algae that make skeletal shells of hydrated amorphous silica, called frustules, which possess hierarchical nanoscale photonic crystal features made by a bottom-up approach at ambient temperature and pressure. In this paper, we theoretically investigate electric field enhancements of plasmonic nanoparticles coated on the surface of diatom skeletal shells. Surface-Enhanced Raman Scattering substrates are prepared by evaporating 10 nm thick silver film and self-assembling silver nanoparticles on diatom surfaces, which show significantly better SERS signals than silver nanoparticles on flat glass substrates.

Ren, Fanghui; Campbell, Jeremy; Hasan, Dihan; Wang, Xiangyu; Rorrer, Gregory L.; Wang, Alan X.

271

A Proton Buffering Role for Silica in Diatoms  

NASA Astrophysics Data System (ADS)

For 40 million years, diatoms have dominated the reverse weathering of silica on Earth. These photosynthetic protists take up dissolved silicic acid from the water and precipitate opaline silica to form their cell wall. We show that the biosilica of diatoms is an effective pH buffer, enabling the enzymatic conversion of bicarbonate to CO2, an important step in inorganic carbon acquisition by these organisms. Because diatoms are responsible for one-quarter of global primary production and for a large fraction of the carbon exported to the deep sea, the global cycles of Si and C may be linked mechanistically.

Milligan, Allen J.; Morel, François M. M.

2002-09-01

272

A simple method for SEM examination of sectioned diatom frustules.  

PubMed

We describe an innovative yet straightforward method to obtain high quality thin sections of diatom exoskeletons for observation by scanning electron microscopy (SEM). The use of this new technique allows for clear observations of some ultrastructural valve features, including the raphe, which are generally difficult to observe and describe accurately using transmission electron microscopy analysis of thin sections or SEM of randomly fractured diatom valves. In addition, because this method involves the complete removal of the organic content of the diatom cells, resulting in clean and mostly undisturbed skeletal thin cross-sections, even the intact valvar structures of weak girdle bands can be studied. PMID:11580816

Massé, G; Poulin, M; Belt, S T; Robert, J M; Barreau, A; Rincé, Y; Rowland, S J

2001-10-01

273

Spatial paradigms of lotic diatom distribution: A landscape ecology perspective  

USGS Publications Warehouse

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.

Passy, S. I.

2001-01-01

274

Direct observations of the mass flocculation of diatom blooms: characteristics, settling velocities and formation of diatom aggregates  

NASA Astrophysics Data System (ADS)

Blooms of chain-forming marine diatoms were observed in the process of aggregating into centimeter-sized flocs of marine snow in surface waters of the Santa Barbara Channel, California. These aggregates were composed of a rich assemblage of living, actively photosynthesizing diatoms dominated by the setose genus Chaetoceros and by chain-forming Nitzschia spp. Flocculation of one bloom occurred in as little as 24 h, and bloom flocculation apparently was not triggered by nitrogen-limitation. Marine snow of diatom origin was also abundant during spring, summer and early autumn throughout the Southern California Bight, suggesting that diatom flocculation is a seasonally significant source of marine snow. Resting spores rarely occurred within either newly formed or aged diatom flocs. The mean in situ settling velocity (± S.D.) of newly formed flocs was 117 ± 56 m d -1, two orders of magnitude faster than unaggregated Chaetoceros. Rapid, episodic export of surface-derived primary production to the ocean bottom via mass flocculation and settlement of diatom blooms can occur prior to consumption by pelagic grazers and significantly effects marine food webs, oceanic flux processes, and diatom biology.

Alldredge, A. L.; Gotschalk, C. C.

1989-02-01

275

Diatoms of the Fortuna Basin, southeast Spain: Evidence for the intra-Messinian inundation  

NASA Astrophysics Data System (ADS)

The Fortuna Basin in southeast Spain, part of the Betic Strait, was one of the connecting pathways between the Atlantic Ocean and the Mediterranean Sea during the late Miocene. The basin contains a remarkable record of Messinian marine sediments. Two well-laminated, marly, diatomaceous sections were examined: the 1-m-thick El Fenazar section (F section) and the 36-m-thick Rio Chicamo Diatomite Member (RCD section). Both sections are intercalated with gypsum horizons. The diatoms in the Rio Chicamo Diatomite suggest an Atlantic origin and strong coastal upwelling associated with high productivity. On the basis of event stratigraphy, the diatomites correlate to the intra-Messinian inundation of the Mediterranean Sea during the Messinian salinity crisis. Four biostratigraphically useful species, Nitzchia jouseae, Thalassiosira oestrupii/T. praeoestrupii, Denticulopsis hustedtii, and Asterolampra acutiloba, occur in the west Pacific between ˜5.35 and 4.5 Ma (lower reversed Gilbert chron). This interpretation places the subsequent Upper Evaporite deposition into the lower reversed Gilbert chron. Our results indicate (1) the existence of a marine connection between the Atlantic Ocean and the Mediterranean Sea through the Betic Strait (southeast Spain) during the Messinian salinity crisis, (2) a possible earlier first appearance of Nitzchia jouseae in the Betic Strait compared to the Atlantic and Pacific oceans according to the stratigraphy of the Fortuna Basin, and (3) the probability that many of the "Tripolilike" and younger diatomites in the Mediterranean are local deposits and diachronous with each other.

Müller, Daniel W.; Schrader, Hans

1989-02-01

276

Perturbation of nuclear lamin A causes cell death in chondrocytes  

PubMed Central

Objective Mutations in LMNA encoding the A-type lamins cause several diseases including those with features of premature aging and skeletal abnormalities. We therefore examined the expression of lamin A in cartilage from humans with osteoarthritis (OA) and studied the effects of its overexpression on chondrocyte senescence and apoptosis. Methods Human chondrocyte-like cells (SW1353) were utilized in this study. RNA isolated from human OA and non-OA cartilages were used for profiling mRNA expression using Affymetrix microarray. Effects of lamin A overexpression on mitochondrial function and apoptosis were examined by assessing mitochondrial membrane potential, ATP levels, cytochrome C release and TUNEL assay. Western blots were performed for protein expression. Results Lamin A expression was markedly elevated in OA cartilage samples compared with non-OA controls. Western analysis confirmed elevated levels of lamin A expression in OA compared to non-OA cartilage. IL-1? treatment inhibited, whereas PGE2 caused a marked increase in lamin A accumulation. These effects of exogenous PGE2 on lamin A expression were mediated via EP2/4 receptor. Transfected chondrocytes that expressed lamin A displayed markers of early senescence/apoptosis. Conclusion Our results suggest that lamin A is upregulated in OA chondrocytes, and increased nuclear accumulation of lamin A in response to catabolic stress may account for the premature aging phenotype and apoptosis of chondrocytes in OA.

Attur, Mukundan; Ben-Artzi, Ami; Yang, Qing; Al-Mussawir, Hayf E.; Worman, Howard J.; Palmer, Glyn; Abramson, Steven B.

2012-01-01

277

Formal Theory of Atom-Diatomic Molecule Reactions.  

National Technical Information Service (NTIS)

Low energy atom-diatomic molecule scattering is formulated in the adiabatic representation. Explicit care is taken to describe the scattering boundary conditions and the Pauli principle correctly. A set of coupled three body equations is obtained for the ...

M. H. Mittleman

1974-01-01

278

Complex gold nanostructures derived by templating from diatom frustules.  

PubMed

Diatom frustules have been used for the first time as templates for the fabrication of gold nanostructures; high-precision replicas featuring complex three-dimensional gold nanostructures from the nano- to the microscale were achieved. PMID:16205794

Losic, Dusan; Mitchell, James G; Voelcker, Nicolas H

2005-09-07

279

Diatom cells grown and baked on a functionalized mica surface.  

PubMed

We demonstrate the cultivation of diatom cells on a functionalized mica surface and the preparation of frustules on a mica surface by baking. Diatom cells were successfully grown on a mica surface treated with 3-aminopropyltriethoxysilane. After baking at 400 degrees C for 2 h, frustule structures without the organic components of the diatom cells were successfully observed by scanning electron microscopy and atomic force microscopy. Furthermore, the frustules deformed and became slender when a sample was baked at 800 degrees C for 2 h. Our method is effective for the direct characterization of frustule structures and physical properties without changing the configuration of the diatom cells grown on the mica surface. PMID:19669502

Umemura, Kazuo; Noguchi, Yusuke; Ichinose, Takuya; Hirose, Yo; Kuroda, Reiko; Mayama, Shigeki

2008-06-24

280

Nonequilibrium Nozzle Flows of Monatomic and Diatomic Gases.  

National Technical Information Service (NTIS)

Chemically nonequilibrium, quasi-one-dimensional flows of partially ionized, monatomic and diatomic gases through a convergent-divergent nozzle were studied theoretically. In the flow of monatomic gas, ionization-recombination nonequilibrium flow of argon...

R. Matsuzaki N. Hirabayashi

1974-01-01

281

Enhancing surface plasmon resonances of metallic nanoparticles by diatom biosilica.  

PubMed

Diatoms are single-celled algaes that make photonic-crystal-like silica shells or frustules with hierarchical micro- & nano-scale features consisting of two-dimensional periodic pores. This article reports the use of diatom frustules as an integration platform to enhance localized surface plasmon resonances of self-assembled silver nanoparticles (NPs) on the surface of diatom frustules. Theoretical and experimental results show enhanced localized surface plasmons due to the coupling with the guided-mode resonances of the frustules. We observed 2 × stronger optical extinction and over 4 × higher sensitivity of surface-enhanced Raman scattering of Rhodmine 6G from the NPs-on-diatom than the NPs-on-glass structure. PMID:23842317

Ren, Fanghui; Campbell, Jeremy; Wang, Xiangyu; Rorrer, Gregory L; Wang, Alan X

2013-07-01

282

Investigation of Light Manipulation by the Ultrastructure of Marine Diatoms.  

National Technical Information Service (NTIS)

This report results from a contract tasking University of Exeter as follows: Our investigation will comprise five principle sections: 1. Determination of the ranges and geometries of the most common forms of diatom structures. This will enable selection o...

P. Vukusic

2009-01-01

283

Modified Ribose Receptor Response in Isolated Diatom Frustules  

SciTech Connect

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.

Fairbanks, Carly R.

2011-08-26

284

Thermomechanical postbuckling analysis of laminated composite shells  

SciTech Connect

The nonlinear response of laminated composite structures subjected to thermal loads is investigated. Analysis is performed using a refined theory and an associated finite element model for geometrically nonlinear analysis of laminated composite shell structures. The model is based on a third-order displacement field which accounts for both transverse shear and transverse normal deformations. Numerical studies of simply-supported plates and cylindrical panels indicate that when the panels are free to expand or contract in the transverse direction, the predicted critical buckling temperatures do not depend significantly upon whether or not transverse normal deformations are explicitly accounted for in the analysis model. However, the critical buckling temperatures are strongly dependent upon whether or not the transverse normal deformations are restrained along the boundaries of the panels. 25 refs.

Averill, R.C.; Reddy, J.N.

1993-01-01

285

Indirect laminate veneer: a conservative novel approach.  

PubMed

Various treatment options and materials are available for restoration of an endodontically treated tooth. Laminate veneer is conservative treatment usually employed for aesthetic correction or improvement. The indirect composite is available in a wide range of shades and specific characterisation is easily performed chair side in the operatory area, which makes it a quick procedure and time saving for both the patient and the dentist. The physical properties and optical properties are good enough to use it as indirect restorative material, so in this particular case it was the material of choice for fabrication of laminate veneer on anterior tooth. In this case, the endodontically treated tooth with a fractured incisal edge was restored with indirect composite material. PMID:23975914

Prajapati, Paranjay; Sethuraman, Rajesh; Naveen, Y G; Patel, Jayanti R

2013-08-23

286

Impact behavior of thick laminated composite beams  

NASA Astrophysics Data System (ADS)

A higher-order shear deformation theory (HST) and the conventional first-order theory (FST) are used to develop a finite element method to analyze the impact behavior of laminated composite beams. The higher-order theory assumes all the displacement components u, v, w that contain variation up to cubic power of z. The effects of various parameters, such as span to thickness ratios, support conditions, and stacking sequence, on the impact behavior of laminated composite beams are studied. Both eight-noded and nine-noded isoparametric elements are employed to compare the computational efficiency. However, to save computational time, numerical results are generated using only eight-noded isoparametric elements. The present results compare well with those of W. Goldsmith. It is observed that stresses computed using HST and FST exhibit wide variations.

Maiti, Dipak Kr.; Sinha, P. K.

1995-03-01

287

High energy impact on woven laminates  

NASA Astrophysics Data System (ADS)

The influence of high velocity impacts on CFRPs was studied by launching Spherical steel masses, at velocities from 60 m/s to 550 m/s, against carbon fiber/epoxy woven laminates. The extension of the damage induced in the laminate was measured by C-Scan. Finite element numerical simulation of the impact test used a failure model based on the Chang-Chang model. A comparison was made of the damaged areas resulting from non-destructive inspection of the specimens and those predicted by numerical simulation. To conclue the analysis, an analytical model developed by Cantwell-Morton was used to calculate the residual velocity of the projectile after perforation. The residual velocities predicted by numerical and by analytical models, were also compared.

López-Puente, J.; Zaera, R.; Navarro, C.

2003-09-01

288

Diatom survivorship in ballast water during trans-Pacific crossings  

Microsoft Academic Search

Ship ballast water is believed to be responsible for global dispersal of alien biota; mid-ocean ballast water exchange is\\u000a most commonly used to mitigate this process. Diatoms are among the most abundant biotic-component in ballast water, yet their\\u000a invasive biology is poorly understood. To test effectiveness of MOE we examined diatom species composition and cell density\\u000a in two sets of

Georgia Klein; Kayleigh MacIntosh; Irena Kaczmarska; James M. Ehrman

2010-01-01

289

REVIVAL CAPACITY OF DIATOMS IN BIVALVE PSEUDOFAECES AND FAECES  

Microsoft Academic Search

The revival capacity of eight species of diatoms rejected in pseudofaeces and faeces of a filter-feeder, the Pacific oyster Crassostrea gigas Thunberg, was assessed by experimental culture tests. Isolated from oyster fattening ponds near Bourgneuf Bay on the French Atlantic coast (46–47°N, 1–2°W), the eight diatom species were: Amphora sp., Chaetoceros sp., Entomoneis alata, Haslea ostrearia, Nitzschia acicularis, Nitzschia closterium,

Laurent Barillé; Bruno Cognie

2000-01-01

290

Epilithic diatoms of mountain lakes of the Tatra Mountains (Slovakia)  

Microsoft Academic Search

In the framework of the international project EMERGE, species composition of epilithic diatoms of 34 selected high mountain\\u000a lakes of Slovak part of the Tatra Mountains were investigated. In all, 127 taxa of diatoms belonging to 26 genera were recorded.\\u000a Comparison of the epilithic assemblages of the investigated lakes showed differences both in relative abundance and taxa present\\u000a in the

Elena Štefková

2006-01-01

291

The biogeography of major diatom taxa in Southern Ocean sediments  

Microsoft Academic Search

Diatoms from 228 Southern Ocean core-top sediment samples were examined to determine the geographic distributions of 32 major diatom species\\/taxa preserved in the sediments of three zonally-distinct regions; Sea Ice, Open Ocean and the Tropical\\/Subtropical. In the first of three papers, 14 species\\/taxa occurring in the region where sea ice covers the ocean surface on an annual basis are geographically

Leanne K. Armand; Xavier Crosta; Oscar Romero; Jean-Jacques Pichon

2005-01-01

292

Late Quaternary Diatom Assemblages from Prydz Bay, Eastern Antarctica  

Microsoft Academic Search

The paleo-depositional environment of inner Prydz Bay, East Antarctica, has been reconstructed for the past 21,320 14C yr B.P., using diatom assemblages and sediment facies from a short, 352-cm-long gravity core. Between 21,320 and 11,650 14C yr B.P., compact tillite and diamicton are present in the core, and diatom frustules are rare to absent. These data suggest that an ice

Fiona Taylor; Andrew McMinn

2002-01-01

293

UV effects on invertebrate and diatom assemblages of Greece  

Microsoft Academic Search

The effects of solar radiation (PAR, UVA, UVB) on the productivity and structure of diatom and invertebrate assemblages were assessed during primary succession on artificial substrate near a rocky shore of the Saronikos Gulf, Greece. Three light treatments were performed (PAR, PAR+UVA, and PAR+UVA+UVB) at 0.5, 1.0 and 1.5 m of depth. Pennate diatoms were the major component of the

Sophia Reizopoulou; Photeinos Santas; Daniel Danielidis; Donat-P Häder; Regas Santas

2000-01-01

294

Dissolution rates of silica from diatoms decomposing at various temperatures  

Microsoft Academic Search

In a study of silica dissolution from diatoms, the rate coefficient (K) h-1 of raw diatom cells was estimated as 4 to 5 times smaller than that of the acid-digested siliceous skeletons. The dissolution rate coefficient at early stage (K1) can be predicted as a function of temperature (T°C): in K1=a+ßT, where a is the frequency factor depending on the

A. Kamatani

1982-01-01

295

Opening the gateways for diatoms primes Earth for Antarctic glaciation  

NASA Astrophysics Data System (ADS)

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 (?30Si) 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 ?30Si 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 ?30Si 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.

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

2013-08-01

296

Progressive fracture of laminated composite stiffened plate  

Microsoft Academic Search

Laminated fiber-reinforced composite stiffened plate with [0\\/90\\/±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

Pascalis K. Gotsis; Christos C. Chamis; Kostantinos David; F. Abdi

2009-01-01

297

Vacuum flashover characteristics of laminated polystyrene insulators  

Microsoft Academic Search

Laminated insulators consist of multiple layers of thin dielectric material stacked with metal films or thin metal layers. The formed stack withstands higher voltage than an equivalent, thick single-layer insulator. In the past materials like polyester, polycarbonate and polyamides have been used with values as high as 350 kV\\/cm for short pulse duration (50 to 100 nsec). Other materials, such

J. M. Elizondo; A. Dragt; M. Krogh; D. Brooks; R. Smelser; P. Aragon; H. Happek; D. Torres; K. D. Ware; K. R. Prestwich

1999-01-01

298

Aging and nuclear organization: lamins and progeria  

Microsoft Academic Search

The discoveries of at least eight human diseases arising from mutations in LMNA, which encodes the nuclear A-type lamins, have revealed the nuclear envelope as an organelle associated with a variety of fundamental cellular processes. The most recently discovered diseases associated with LMNA mutations are the premature aging disorders Hutchinson–Gilford progeria syndrome (HGPS) and atypical Werner’s syndrome. The phenotypes of

Leslie C Mounkes; Colin L Stewart

2004-01-01

299

Behavior of bolted joints in composite laminates  

Microsoft Academic Search

This investigation characterizes bolted joint strength in Kevlar\\/epoxy and graphite\\/epoxy (0\\/45\\/90\\/-45)ââ 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

Jurf

1986-01-01

300

Synthetic multifunctional metallic-intermetallic laminate composites  

Microsoft Academic Search

The field of material microstructure design targeted for a specific set of structural and functional properties is now a recognized\\u000a field of focus in materials science and engineering. This paper describes a new class of structural materials called metallic-intermetallic\\u000a laminate (MIL) composites, which can have their micro-, meso- and macrostructure designed to achieve a wide array of material\\u000a properties and

Kenneth S. Vecchio

2005-01-01

301

THE DAMAGE THRESHOLD OF LAMINATED GLASS STRUCTURES  

Microsoft Academic Search

The effect of varying the thickness of the individual glass layers on the impact resistance of a range of laminated glass constructions has been examined. Chippings, similar to those used in traditional road construction, have been accelerated to velocities in excess of 20m\\/s using a purpose-built catapult system. Tests have been conducted at both normal and 45° angles to the

P. V Grant; W. J Cantwell; H McKenzie; P Corkhill

1998-01-01

302

Hypervelocity impact on laminate composite panels  

Microsoft Academic Search

Phenomenological results on the damage of flat glass-, aramid- and carbon-fiber reinforced epoxy laminated composites under the impact of steel and glass projectiles at velocity up to 8–11 km\\/s are presented. The damage of composite panels under hypervelocity impact is shown to differ significally from that observed for elastoplastic materials. However, it is shown that a number of qualititative results

V. V. Silvestrov; A. V. Plastinin; N. N. Gorshkov

1995-01-01

303

Laminated grid and web magnetic cores  

DOEpatents

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.

Sefko, John (Monroeville, PA); Pavlik, Norman M. (Plum Borough, PA)

1984-01-01

304

Eastern Guaymas Basin: laminated but not anoxic  

NASA Astrophysics Data System (ADS)

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.

Cheshire, H.; Thurow, J. W.

2009-12-01

305

Laminate analogy for composites enhanced concrete structures  

SciTech Connect

A new and effective method is described to design composites to repair damage or enhance the overload strength of concrete infrastructures. The method is based on laminate analogy which is derivable from composite mechanics and available in computer codes. It is used to simulate structural sections made from reinforced concrete which are typical in infrastructures as well as select reinforced concrete structures. The structural sections are represented by a number of layers through the thickness where different layers are used for the concrete, for the reinforcing steel in concrete, and for the composite. The reinforced concrete structures are represented with finite elements where the element stiffness parameters are from the structural sections which are represented by the laminate analogy. The load carrying capability of the structure is determined by progressive structural fracture. Results show up to 40 percent improvements for damage and for overload enhancement with relatively small laminate thickness for the structural sections and up to three times for the composite enhanced select structures (arch and dome).

Chamis, C.C.; Gotsis, P.K. [NASA Lewis Research Center, Cleveland, OH (United States)

1997-10-01

306

Regularities in molecular properties of ground state stable diatomics.  

PubMed

A simple relationship is reported between vibrational frequencies, bond lengths, and reduced masses for many families of stable, ground state diatomics: the frequency is proportional to the reciprocal of the product of the bond length and the square root of the reduced mass. This is demonstrated with each of the following related families: the alkali metal diatomics, the group 15 diatomics, the group 16 diatomics, the halogen diatomics, the alkali metal hydrides, the alkaline earth oxides, the group 14 oxides and their sulfides, the diatomics of carbon, of silicon and of germanium with group 16 elements, the hydrogen halides, the halides of lithium, of sodium, of potassium, of rubidium and of cesium, the chlorides of the alkali metals and of silver, and the polyatomic hydrides of groups 14 and 15. Although correlation coefficients of 0.99 or greater in each of the 21 families examined demonstrate the validity of the correlation, the deviations found are significantly larger than can be attributed to experimental uncertainties. PMID:15268024

Zavitsas, Andreas A

2004-06-01

307

Role of diatoms in regulating the ocean's silicon cycle  

NASA Astrophysics Data System (ADS)

Among phytoplankton the diatoms are strong competitors and contribute significantly to total global primary production. Aspects of their life history, notably their high sinking rates, make them important to the export flux of carbon into the ocean interior. Unlike the majority of other phytoplankton, they utilize silicic acid (=silicate) to construct their cell walls and are controlled by its availability and distribution. Here a simple model is developed to study the relationship between the diatoms and the ocean's silicon cycle. The ecological component of this model pits the slightly superior diatoms against all other algae, with both groups competing for phosphate while the diatoms additionally require silicic acid. The model agrees reasonably with observed distributions of nutrients and with their biogeochemical fluxes. While theoretically superior, the diatoms are held in check by the availability of silicic acid, allowing the persistence and numerical dominance of the other algae. The concentrations of both nutrients are homeostatically controlled by the phytoplankton, and resist perturbations. Analysis finds that primary production in the model is ultimately controlled by phosphate, with silicic acid abundance controlling the fraction of the total produced by diatoms. Sensitivity analyses using more ecologically detailed variants of the model find that these results are generally robust. The model's treatment of the "silica pump" hypothesis [, 1998] is also examined.

Yool, Andrew; Tyrrell, Toby

2003-12-01

308

Marine polysaccharide networks and diatoms at the nanometric scale.  

PubMed

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

Svetli?i?, Vesna; Zuti?, Vera; Pletikapi?, Galja; Radi?, Tea Miši?

2013-10-09

309

Changes in marine dinoflagellate and diatom abundance under climate change  

NASA Astrophysics Data System (ADS)

Marine diatoms and dinoflagellates play a variety of key ecosystem roles as important primary producers (diatoms and some dinoflagellates) and grazers (some dinoflagellates). Additionally some are harmful algal bloom (HAB) species and there is widespread concern that HAB species may be increasing accompanied by major negative socio-economic impacts, including threats to human health and marine harvesting. Using 92,263 samples from the Continuous Plankton Recorder survey, we generated a 50-year (1960-2009) time series of diatom and dinoflagellate occurrence in the northeast Atlantic and North Sea. Dinoflagellates, including both HAB taxa (for example, Prorocentrum spp.) and non-HAB taxa (for example, Ceratium furca), have declined in abundance, particularly since 2006. In contrast, diatom abundance has not shown this decline with some common diatoms, including both HAB (for example, Pseudo-nitzschia spp.) and non-HAB (for example, Thalassiosira spp.) taxa, increasing in abundance. Overall these changes have led to a marked increase in the relative abundance of diatoms versus dinoflagellates. Our analyses, including Granger tests to identify criteria of causality, indicate that this switch is driven by an interaction effect of both increasing sea surface temperatures combined with increasingly windy conditions in summer.

Hinder, Stephanie L.; Hays, Graeme C.; Edwards, Martin; Roberts, Emily C.; Walne, Anthony W.; Gravenor, Mike B.

2012-04-01

310

Molecular identification of sequestered diatom chloroplasts and kleptoplastidy in foraminifera.  

PubMed

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

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

2010-12-03

311

Testing and simulation of composite laminates under impact loading  

Microsoft Academic Search

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

Xinglai Dang

2000-01-01

312

Altered protein dynamics of disease-associated lamin A mutants  

PubMed Central

Background Recent interest in the function of the nuclear lamina has been provoked by the discovery of lamin A/C mutations in the laminopathy diseases. However, it is not understood why mutations in lamin A give such a range of tissue-specific phenotypes. Part of the problem in rationalising genotype-phenotype correlations in the laminopathies is our lack of understanding of the function of normal and mutant lamin A. To investigate this we have used photobleaching in human cells to analyse the dynamics of wild-type and mutant lamin A protein at the nuclear periphery. Results We have found that a large proportion of wild-type lamin A at the nuclear periphery is immobile, but that there is some slow movement of lamin A within the nuclear lamina. The mobility of an R482W mutant lamin A was indistinguishable from wild-type, but increased mobility of L85R and L530P mutant proteins within the nuclear lamina was found. However, the N195K mutant shows the most enhanced protein mobility, both within the nucleoplasm and within the lamina. Conclusion The slow kinetics of lamin A movement is compatible with its incorporation into a stable polymer that only exchanges subunits very slowly. All of the myopathy-associated lamin A mutants that we have studied show increased protein movement compared with wild-type. In contrast, the dynamic behaviour of the lipodystrophy-associated lamin A mutant was indistinguishable from wild-type. This supports the hypothesis that the underlying defect in lamin A function is quite distinct in the laminopathies that affect striated muscle, compared to the diseases that affect adipose tissue. Our data are consistent with an alteration in the stability of the lamin A molecules within the higher-order polymer at the nuclear lamina in myopathies.

Gilchrist, Susan; Gilbert, Nick; Perry, Paul; Ostlund, Cecilia; Worman, Howard J; Bickmore, Wendy A

2004-01-01

313

Perforation of flexible laminates by projectiles of different geometry  

Microsoft Academic Search

This paper investigates the response of flexible laminates to ballistic impacts by projectiles of various geometries, namely, flat-ended, hemispherical, ogival (CRH 2.5) and conical (30° half-angle) projectiles. The laminate of interest is Spectra Shield® comprising [0°\\/90°] extended chain polyethylene filaments embedded in a thermoplastic resin. Ballistic tests show that flat-ended projectiles cut the laminate through a shearing action, effectively punching

V. B. C. Tan; K. J. L. Khoo

2005-01-01

314

Analysis of adhesion and interface debonding in laminated safety glass  

Microsoft Academic Search

Abstraet-A tension adhesion test is developed and analyzed to characterize polymer\\/glass adhesion in laminated safety glass. Laminated safety glass typically consists of two sheets of glass bonded by a polymer adhesive interlayer, usually plasticized poly(vinyl butyral). In the tension test, a rectangular laminate specimen is cracked on both glass sides, and loaded under a remote tension P at a constant

Y. Sha; C. Y. Hui; E. J. Kramer; P. D. Garrett; J. W. Knapczyk

1997-01-01

315

Delamination in FRP laminates with holes under transverse impact  

Microsoft Academic Search

The present paper deals with the study of hybridization on impact response and impact induced delamination of laminated composite plates with holes. Three dimensional finite element analysis has been done to evaluate the response of graphite\\/epoxy laminate as well as graphite\\/epoxy–kevlar\\/epoxy hybrid laminate subjected to impact loading, and stress based delamination criterion has been used to assess the chances of

Tarapada Roy; Debabrata Chakraborty

2008-01-01

316

Thermal shock resistance of laminated ceramic matrix composites  

Microsoft Academic Search

The thermal shock resistance capability of laminated ceramic matrix composites is investigated through the study of three-dimensional transient thermal stresses and laminate failure mechanisms. A (-45°\\/45°)s SiC\\/borosilicate glass laminate is utilized as a reference composite system to demonstrate the analytical results. The maximum allowable temperature change, ?Tmax, has been taken as a measure of the thermal shock resistance capability of

Y. R. Wang; T.-W. Chou

1991-01-01

317

Tape casting of AlâOâ\\/ZrOâ laminated composites  

Microsoft Academic Search

Fracture toughness of ZrOâ toughened alumina could be increased by macroscopic interfaces. Such as those existing in laminated composites. In this work, tape casting was used to produce A\\/A or A\\/B laminates, where A and B can be AlâOâ, ALâOâ\\/5 vol% ZrOâ, and AlâOâ\\/10 vol% ZrOâ. An increase in toughness is observed, even in the AlâOâ\\/AlâOâ laminates.

Philippe Boch; Thierry Chartier; Muriel Huttepain

1986-01-01

318

COMPOS: A Computer Program for the Property Synthesis and Hygrothermal Stress Analysis of Laminated Composites.  

National Technical Information Service (NTIS)

A FORTRAN computer program for the property synthesis and hygrothermal stress analysis of composite laminates is described. Its basis is the mathematics and assumptions of classical laminated plate theory. The program synthesizes laminate properties by us...

A. M. Lindrose

1978-01-01

319

Silicon and the ecology of marine plankton diatoms. II. Silicate-uptake kinetics in five diatom species  

Microsoft Academic Search

The variation of the rate of silicate uptake with varying silicate concentration in the medium was investigated in short-term experiments with the following marine diatom species:Skeletonema costatum, Thalassiosira pseudonana, T. decipiens, Ditylum brightwellii, andLicmophora sp. The uptake conformed to Michaelis-Menten kinetics only after a correction had been made for reactive silicate that apparently could not be utilized by the diatoms.

E. Paasche

1973-01-01

320

Mechanical model of blebbing in nuclear lamin meshworks  

PubMed Central

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 Hutchinson–Gilford 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.

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

2013-01-01

321

Mechanical model of blebbing in nuclear lamin meshworks.  

PubMed

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 Hutchinson-Gilford 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

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

2013-02-11

322

An Elastic Model of Blebbing in Nuclear Lamin Meshworks  

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

323

Mapping of lamin A- and progerin-interacting genome regions.  

PubMed

Mutations in the A-type lamins A and C, two major components of the nuclear lamina, cause a large group of phenotypically diverse diseases collectively referred to as laminopathies. These conditions often involve defects in chromatin organization. However, it is unclear whether A-type lamins interact with chromatin in vivo and whether aberrant chromatin-lamin interactions contribute to disease. Here, we have used an unbiased approach to comparatively map genome-wide interactions of gene promoters with lamin A and progerin, the mutated lamin A isoform responsible for the premature aging disorder Hutchinson-Gilford progeria syndrome (HGPS) in mouse cardiac myoytes and embryonic fibroblasts. We find that lamin A-associated genes are predominantly transcriptionally silent and that loss of lamin association leads to the relocation of peripherally localized genes, but not necessarily to their activation. We demonstrate that progerin induces global changes in chromatin organization by enhancing interactions with a specific subset of genes in addition to the identified lamin A-associated genes. These observations demonstrate disease-related changes in higher order genome organization in HGPS and provide novel insights into the role of lamin-chromatin interactions in chromatin organization. PMID:22610065

Kubben, Nard; Adriaens, Michiel; Meuleman, Wouter; Voncken, Jan Willem; van Steensel, Bas; Misteli, Tom

2012-05-19

324

The Displacement Perspective During Ultimate Failure of Composite Laminates  

NASA Astrophysics Data System (ADS)

This paper deals with the studies on the state of displacement of symmetric and anti-symmetric angle-ply and cross-ply laminated composite plates during its ultimate failure, subjected to transverse static load. First-order shear deformation theory (FSDT) is employed in conjunction with the finite element approach using eight-noded quadratic isoparametric element. The free vibration analyses of isotropic and laminated composite plates are carried out to ensure the overall validity of the present finite element formulation. The mid surface of the laminate is considered as the reference plane. The principal material directions in different laminae are oriented to produce a laminated structural element capable of resisting loads in several directions. The stiffness of a composite laminate is obtained from the properties of the constituent laminae. The affected stiffness of the failed lamina is discarded completely after the failure of weakest ply. The rigidity matrix of the laminate with remaining laminae is re-established. The re-evaluation process continues until the laminate fails completely. To investigate the displacement behaviour of laminates during the ultimate failure, parametric studies are carried out for different cases by varying the stacking sequences, fiber orientations, layer thicknesses, aspect ratios and the number of layers in the laminate. The comparison of results in terms of non-dimensional natural frequencies and ply-by-ply failure analyses obtained from the present investigation are made with those available in the reported literature.

Pal, P.; Bhar, A.

2013-04-01

325

Extrinsic fracture mechanisms in two laminated metal composites  

SciTech Connect

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.

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

1994-11-29

326

Processing and mechanical characterization of alumina laminates  

NASA Astrophysics Data System (ADS)

Single-phase ceramics that combine property gradients or steps in monolithic bodies are sought as alternatives to ceramic composites made of dissimilar materials. This work describes novel processing methods to produce stepped-density (or laminated) alumina single-phase bodies that maintain their mechanical integrity. One arrangement consists of a stiff, dense bulk material with a thin, flaw tolerant, porous exterior layer. Another configuration consists of a lightweight, low-density bulk material with a thin, hard, wear resistant exterior layer. Alumina laminates with strong interfaces have been successfully produced in this work using two different direct-casting processes. Gelcasting is a useful near-net shape processing technique that has been combined with several techniques, such as reaction bonding of aluminum oxide and the use of starch as a fugative filler, to successfully produced stepped-density alumina laminates. The other direct casting process that has been developed in this work is thermoreversible gelcasting (TRG). This is a reversible gelation process that has been used to produce near-net shape dense ceramic bodies. Also, individual layers can be stacked together and heated to produce laminates. Bilayer laminate samples were produced with varied thickness of porous and dense layers. It was shown that due to the difference in modulus and hardness, transverse cracking is found upon Hertzian contact when the dense layer is on the exterior. In the opposite arrangement, compacted damage zones formed in the porous material and no damage occurred in the underlying dense layer. Flaw tolerant behavior of the porous exterior/dense underlayer was examined by measuring biaxial strength as a function of Vickers indentation load. It was found that the thinnest layer of porous material results in the greatest flaw tolerance. Also, higher strength was exhibited at large indentation loads when compared to dense monoliths. The calculated stresses on the surfaces and interface afforded an explanation of the behavior that failure initiates at the interface between the layers for the thinnest configuration, rather than the sample surface.

Montgomery, John K.

2002-08-01

327

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

PubMed Central

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.

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

2008-01-01

328

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

SciTech Connect

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.

Reyes, N.E.

1993-01-01

329

Dynamics of nuclear lamina as monitored by GFP-tagged A-type lamins  

Microsoft Academic Search

The behavior of chimeric proteins consisting of A-type lamins and green fluorescent protein (GFP) was studied to investigate the localization and dynamics of nuclear lamins in living cells. Cell line CHO-K1 was transfected with cDNA constructs encoding fusion proteins of lamin A-GFP, lamin A? ?10-GFP, or lamin C-GFP. In the interphase nucleus lamin-GFP fluorescence showed a perinuclear localization and incorporation

Jos L. V. Broers; Barbie M. Machiels; Eys van G. J. J. M; Helma J. H. Kuijpers; F. C. Ramaekers; Roel van Driel

1999-01-01

330

Temporal changes of diatoms in marine biofilm developed on acrylic panels submerged in a tropical coast  

NASA Astrophysics Data System (ADS)

The colonization of diatom groups on the acrylic panels submerged in Kudankulam coastal waters, east coast of India, was studied for one year from October 2004 to August 2005. Results showed temporal variability in the abundance of dominant diatom groups. Diatoms belonging to 19 genera colonized the panels. Navicula and Nitzschia were the dominant diatoms observed throughout the present study. The abundance of diatoms on test panels increased with the length of exposure. Significant variations in the abundance of Navicula and Nitzschia were observed between the sampling months. Temporal changes in biofilm diatom community composition in this study attain significance from the view point of macrofouling community recruitment on marine structures.

Satheesh, Sathianeson; Wesley, Samuel Godwin

2012-12-01

331

A unified theory for laminated plates  

NASA Astrophysics Data System (ADS)

A literature survey on plate and beam theories show how the advent of the finite element method and the variational method circa 1940 have been a great stimulant for the research in this field. The initial thin plate formulation has been incrementally expanded to treat the isotropic thick plate, the anisotropic single layer, and then laminated plates. It appears however that current formulations still fall into one of two categories: (1) The formulation is tailored for a specific laminate and/or loading case; (2) or the formulation is too complicated to be of practical relevance. In this work a new unifying approach to laminated plate formulation is presented. All laminated plates, including sandwich panels, subjected to any surface load and with any boundary conditions are treated within a single model. In addition, the fundamental behavior of the plate as a two-dimensional structural element is explained. The novel idea is the introduction of fundamental state solutions, which are analytical far field stress and strain solutions of the laminated plate subjected to a set of hierarchical primary loads, the fundamental loads. These loads are carefully selected to form a basis of the load space, and corresponding solutions are superposed to obtain extremely accurate predictions of the three dimensional solution. six,y,z =aklx,y sikl z where i = 1,..., 6; 1=1,...,l max is a substate of the kth fundamental state k=1,2,3,... Typically, a fundamental state solution is expressed as a through-thickness function (z), while the amplitudes of each fundamental load are found from two dimensional finite element solution as a function of in-plane coordinates (x,y). Three major contributions are produced in this work: (1) A complete calibration of the plate as a two-dimensional structure is performed with pure bending and constant shear fundamental states. (2) There are four independent ways to apply a constant shear resultant on a plate, as opposed to one for a beam. This makes it impossible to define a unique 2 x 2 transverse shear stiffness matrix. Therefore the traditional problem of the shear correction factor loses all relevance. It is however shown that an explicit transverse constitutive relation can be obtained for isotropic-layered laminates or single-layers. (3) Higher accuracy, three-dimensional solutions are obtained using a two-dimensional finite element model with a complexity level (degrees of freedom) similar to the Reissner-Mindlin plate. The proof of concept is realized using Pagano solution for rectangular plates under sinusoidal load, for a sandwich panel. Additional comparisons are also performed for four and six-layer symmetric and antisymmetric laminates, between the new plate theory results and full three-dimensional finite element solutions.

Guiamatsia Tafeuvoukeng, Irene

332

Vibrational Excitation of Diatomic Molecular Ions in Strong Field Ionization of Diatomic Molecules  

SciTech Connect

A model based on the strong-field and Born-Oppenheimer approximations qualitatively describes the distribution over vibrational states formed in a diatomic molecular ion following ionization of the neutral molecule by intense laser pulses. Good agreement is found with a recent experiment [X. Urbain et al., Phys. Rev. Lett. 92, 163004 (2004)]. In particular, the observed deviation from a Franck-Condon-like distribution is reproduced. Additionally, we demonstrate control of the vibrational distribution by a variation of the peak intensity or a change of frequency of the laser pulse.

Kjeldsen, Thomas K.; Madsen, Lars Bojer [Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus C (Denmark)

2005-08-12

333

Effects of lamination and changes in layer thickness on fatigue-crack propagation of lightweight laminated metal composites  

Microsoft Academic Search

The effects of lamination and changes in the laminae thickness on the fatigue-crack propagation of 6090\\/SiC\\/25p-6013 laminates\\u000a tested in the crack-arrestor orientation were investigated. The fatigue-crack propagation behavior of the individual monolithic\\u000a and discontinuously reinforced aluminum alloy (DRA) layers was compared to that of the laminates. The fatigue behavior of\\u000a the laminates was different than that of the individual laminae

Hala A. Hassan; J. J. Lewandowski; M. H. Abd El-Latif

2004-01-01

334

Nanopatterned protein microrings from a diatom that direct silica morphogenesis  

PubMed Central

Diatoms are eukaryotic microalgae that produce species-specifically structured cell walls made of SiO2 (silica). Formation of the intricate silica structures of diatoms is regarded as a paradigm for biomolecule-controlled self-assembly of three-dimensional, nano- to microscale-patterned inorganic materials. Silica formation involves long-chain polyamines and phosphoproteins (silaffins and silacidins), which are readily soluble in water, and spontaneously form dynamic supramolecular assemblies that accelerate silica deposition and influence silica morphogenesis in vitro. However, synthesis of diatom-like silica structure in vitro has not yet been accomplished, indicating that additional components are required. Here we describe the discovery and intracellular location of six novel proteins (cingulins) that are integral components of a silica-forming organic matrix (microrings) in the diatom Thalassiosira pseudonana. The cingulin-containing microrings are specifically associated with girdle bands, which constitute a substantial part of diatom biosilica. Remarkably, the microrings exhibit protein-based nanopatterns that closely resemble characteristic features of the girdle band silica nanopatterns. Upon the addition of silicic acid the microrings become rapidly mineralized in vitro generating nanopatterned silica replicas of the microring structures. A silica-forming organic matrix with characteristic nanopatterns was also discovered in the diatom Coscinodiscus wailesii, which suggests that preassembled protein-based templates might be general components of the cellular machinery for silica morphogenesis in diatoms. These data provide fundamentally new insight into the molecular mechanisms of biological silica morphogenesis, and may lead to the development of self-assembled 3D mineral forming protein scaffolds with designed nanopatterns for a host of applications in nanotechnology.

Scheffel, Andre; Poulsen, Nicole; Shian, Samuel; Kroger, Nils

2011-01-01

335

Stress relaxation in a diatomic liquid  

NASA Astrophysics Data System (ADS)

By the use of nonequilibrium molecular dynamics we have studied the stress relaxation following imposition of a constant-volume elongation in the x1 direction on a model diatomic liquid. Three consecutive modes of relaxation of the stress difference ?=t11-12(t22+t33) are found, each governed by exponentials e-?it with ?1>?2>?3. Each mode is shown to correspond to the return to isotropy of a different characteristic of the liquid structure that has been rendered anisotropic by the deformation, namely (1) r(?), the mean distance from a generic atom of interacting atoms in the ? direction, with the angle ? measured from the stretch axis x1; (2) N(?), the mean number density of interacting atoms in the ? direction; and (3) <>, a measure of the orientation ?b of molecular axes with respect to x1. The first two modes are identical in form to those studied previously [R. C. Picu and J. H. Weiner, J. Chem. Phys. 107, 7214 (1997)] for stress relaxation in a monatomic liquid, but their rates of decay differ because of differences in packing and in atomic mobility. During the third mode of relaxation it is found that ?=C<>, where C may be understood in terms of the intrinsic stress tensor, a tensor referred to a coordinate system fixed to the molecule [J. Gao and J. H. Weiner, J. Chem. Phys. 90, 6749 (1989)]. The relevance of these results to stress relaxation in polymer melts is discussed.

Picu, R. C.; Weiner, J. H.

1998-03-01

336

Ultraviolet lasing transitions in diatomic molecules  

NASA Astrophysics Data System (ADS)

The work performed is primarily directed toward a better spectroscopic understanding of UV laser transitions in selected diatomic molecules. Specifically the work emphasizes the analysis of spectroscopic data for discrete (bound-bound) and diffuse (bound-free) transitions in the rare gas monohalide (RgX) molecules and discrete transitions in the homonuclear halogens. The primary accomplishments of the work include detailed rotational and vibrational analyses of the lasing B to X transition in XeF (3500 A) and the lasing D: to A: transition in Br2 (2900 A); (2) vibrational analyses of the lasing transitions B to X in XeCl (3100 A) and D: to A: in I2 (3400 A), and the nonlasing D to X transitions in XeF (2600 A) and XeCl (2350 A); analysis of the bound-free B to X and D to X transitions in other RgX molecules, with emphasis on KrCl; reanalysis of the D to X UV fluorescence spectrum of I2; determination of potential curves and intensity factors (Franck-Condon factors, stimulated emission cross sections) for all analyzed systems; determination of the energy ordering of the B and C states in KrCl, XeCl, and XeBr, using temperature-dependent emission spectroscopy; and characterization of a tesla discharge with respect to its temporal and thermal properties and its total radiant output.

Tellinghuisen, J.

1980-01-01

337

Photodissociation imaging of diatomic sulfur (S2).  

PubMed

The photodissociation of diatomic sulfur, S(2), in the region of the first dissociation limit is studied with velocity map imaging. Correlated fine structure distributions P(J1,J2) for the two S((3)P(J)) fragments are determined at selected photolysis wavelengths. Image analysis of the speed distributions of the atomic fragments following product-state-specific detection results in a revision of the bond energy to D(0) = 35636.9 +/- 2.5 cm(-1) with respect to the lowest rovibrational level. This value arises from reinterpretation of previous spectroscopic data showing onset of predissociation in the B(3)Sigma(u)(-) state, as the measurements presented here demonstrate that the long-range correlation of the excited state invoked as causing the dissociation is S((3)P(2)) + S((3)P(2)) rather than S((3)P(2)) + S((3)P(1)). The wavelength dependence of data for the S((3)P(2)) + S((3)P(2)) channel suggests involvement of photoexcitation through the optically forbidden Herzberg continuum bands in addition to dissociation initiated via the optically allowed B(3)Sigma(u)(-)-X(3)Sigma(g)(-) and B''(3)Pi(u)-X(3)Sigma(g)(-) bands. Changes in product recoil velocity angular distributions and atomic angular momentum polarization were also measured as a function of dissociation wavelength. The results are compared with predictions from an adiabatic model for dissociation, which provides a basis for interpretation but does not explain quantitatively the experimental results. PMID:19754091

Frederix, Pim W J M; Yang, Chung-Hsin; Groenenboom, Gerrit C; Parker, David H; Alnama, Koutayba; Western, Colin M; Orr-Ewing, Andrew J

2009-12-31

338

Impulse formalism for atom-diatom collisions  

SciTech Connect

An exact formulation of the impulse approach (IA), or quantum-mechanical spectator model, is applied to atom-diatom collisions. Results are compared with previous work on the IA, which has always involved the peaking approximation (PA). The PA is seen to overestimate (underestimate) differential cross sections for processes involving projectile atom energy loss (gain). The internal consistency of the IA is explored by subjecting it to semidetailed balancing. For small scattering angles the IA is seen to be an inadequate theory, probably due to the neglect of double- and higher-collision terms in the multiple-collision expansion of the three-body {ital T} matrix. For large scattering angles, where the IA does appear to describe the scattering process accurately, the exact calculation is shown to give the same results as when only the energy-conserving on-the-energy-shell two-body processes are considered. An accurate approximation method is also developed for rapid computation of inelastic differential cross sections. Finally, the calculated results are compared with the experimental measurements, and the need to explore two-body potentials more complicated than the hard-core potential is pointed out.

Sharma, R.D. (Optical/Infrared Technology Division, Geophysics Laboratory, Hanscom Air Force Base, Massachusetts 01731 (US)); Bakshi, P.M. (Physics Department, Boston College, Chestnut Hill, Massachusetts 02167 (USA)); Sindoni, J.M. (Yap Analytics, Inc., 594 Marrett Road, Lexington, Massachusetts 02173 (USA))

1991-01-01

339

The aging characteristics of laminated pressboard and laminated wood in oil cooled power transformers  

Microsoft Academic Search

Presspaper and pressboard products made from pure kraft pulp have been used successfully for decades for the solid insulation of power transformers. Many researchers have investigated the aging behavior of such cellulose products in the past. In the recent years, the transformer industry started to use significantly higher quantities of laminated wood (plywood) products. Yet, manufacturers and users have not

H. P. Gasser; C. Krause; T. A. Prevost

2006-01-01

340

A-type lamins: Guardians of the soma?  

Microsoft Academic Search

The gene LMNA encodes the proteins lamins A and C and is implicated in nine different laminopathies — inherited diseases that are linked to premature ageing. Recent evidence has demonstrated that lamins A and C have essential functions in protecting cells from physical damage, as well as in maintaining the function of transcription factors required for the differentiation of adult

Howard J. Worman; Chris J. Hutchison

2004-01-01

341

A Theory of Laminated Composite Plates and Rods.  

National Technical Information Service (NTIS)

This paper is concerned with small deformations of a class of laminated layered composite plates and a class of laminated layered composite rods utilizing a direct formulation of thermomechanical theories of shells and rods. The paper is arranged in two p...

A. E. Green P. M. Naghdi

1981-01-01

342

Prediction of Stress Relaxation in Laminated Leather Layers  

Microsoft Academic Search

Laminated leather, obtained by the bonding of the microporous polyurethane film to split leather surface, was used for investigation. Such hybrid leather is resistant to water penetration, but shows high breathable properties. The effect of different nature layers on mechanical properties and viscoelastic behaviour of laminated leather was examined. It was shown that leather backing mainly determines the strength of

D. Milašien?; V. Jankauskait?; R. Arcišauskait?

343

LACTIC ACIDOSIS: A FACTOR ASSOCIATED WITH EQUINE LAMINITIS 1 ,2  

Microsoft Academic Search

SUMMARY Plasma L-lactate was measured in 31 horses subsequent to carbohydrate overload of the gastrointestinal tract. The greatest increase in lactate was observed in horses dying of circula- tory collapse; horses developing laminitis had a lesser increase, while horses with neither syndrome had only a slight increase. In retro- spect, either death associated with complete circulatory collapse or laminitis associated

H. E. Garner; D. P. Hutcheson; J. R. Coffman; A. W. Hahn; Carol Salem

2010-01-01

344

STRESS CONCENTRATIONS OF SYMMETRICALLY LAMINATED COMPOSITE PLATES CONTAINING CIRCULAR HOLES  

Microsoft Academic Search

In this study, an analysis of fiber reinforced, symmetrically laminated composite plates containing circular holes has been carried out. First, the stress state of a layer in a laminated plate is studied. After obtaining the stress state for each layer due to the uniaxial loading of a plate, the stress concentrations around a circular hole are studied. A number of

M. YASAR KALTAKCI; H. M. ARSLAN

345

Delamination threshold loads for low velocity impact on composite laminates  

Microsoft Academic Search

An investigation of the low velocity impact load level at which a composite laminate will delaminate is presented. The delamination threshold load is described as the load level, obtained from the load–time history or load–displacement plot, at which a sudden load drop occurs due to specimen stiffness loss as a result of laminate level damage. Approximately 500 low velocity impact

G. A. Schoeppner; S. Abrate

2000-01-01

346

Core Delamination and Shear Tests for Laminated Wood.  

National Technical Information Service (NTIS)

A delamination and a shear test method using small cores drilled from wood laminates provide for non-destructive and potentially low cost testing of glueline quality throughout the length and depth of laminated wood members. Cores 3/8 in. diameter obtaine...

R. F. England W. H. Miles

1964-01-01

347

Curvature-Stress Factor in Laminated Wood BEAMS.  

National Technical Information Service (NTIS)

This study was undertaken in an attempt to isolate the influence of prestress induced in laminating curved members and to determine curvature-stress factors applicable to the laminated product. Curvature-stress factor represents the ratio of curved beam s...

C. Kostukevich F. F. Wangaard

1964-01-01

348

A-type nuclear lamins, progerias and other degenerative disorders  

Microsoft Academic Search

Nuclear lamins were identified as core nuclear matrix constituents over 20 years ago. They have been ascribed structural roles such as maintaining nuclear integrity and assisting in nuclear envelope formation after mitosis, and have also been linked to nuclear activities including DNA replication and transcription. Recently, A-type lamin mutations have been linked to a variety of rare human diseases including

Erica D. Smith; Brian A. Kudlow; Richard L. Frock; Brian K. Kennedy

2005-01-01

349

Processing of thermoset prepreg laminate via exposure to microwave radiation  

SciTech Connect

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.

Paulauskas, F.L. [Oak Ridge National Lab., TN (United States); Meek, T.T. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering

1994-06-01

350

Identification of differential protein interactors of lamin A and progerin.  

PubMed

The nuclear lamina is an interconnected meshwork of intermediate filament proteins underlying the nuclear envelope. The lamina is an important regulator of nuclear structural integrity as well as nuclear processes, including transcription, DNA replication and chromatin remodeling. The major components of the lamina are A- and B-type lamins. Mutations in lamins impair lamina functions and cause a set of highly tissue-specific diseases collectively referred to as laminopathies. The phenotypic diversity amongst laminopathies is hypothesized to be caused by mutations affecting specific protein interactions, possibly in a tissue-specific manner. Current technologies to identify interaction partners of lamin A and its mutants are hampered by the insoluble nature of lamina components. To overcome the limitations of current technologies, we developed and applied a novel, unbiased approach to identify lamin A-interacting proteins. This approach involves expression of the high-affinity OneSTrEP-tag, precipitation of lamin-protein complexes after reversible protein cross-linking and subsequent protein identification by mass spectrometry. We used this approach to identify in mouse embryonic fibroblasts and cardiac myocyte NklTAg cell lines proteins that interact with lamin A and its mutant isoform progerin, which causes the premature aging disorder Hutchinson-Gilford progeria syndrome (HGPS). We identified a total of 313 lamina-interacting proteins, including several novel lamin A interactors, and we characterize a set of 35 proteins which preferentially interact with lamin A or progerin. PMID:21327095

Kubben, Nard; Voncken, Jan Willem; Demmers, Jeroen; Calis, Chantal; van Almen, Geert; Pinto, Yigal; Misteli, Tom

2010-09-03

351

Oxydative stress alters nuclear shape through lamins dysregulation  

PubMed Central

Progeroid phenotypes are mainly encountered in 2 types of syndromes: in laminopathies, which are characterized by nuclear shape abnormalities due to lamin A alteration, and in DNA damage response defect syndromes. Because lamin A dysregulation leads to DNA damages, it has been proposed that senescence occurs in both types of syndromes through the accumulation of damages. We recently showed that elevated oxidative stress is responsible for lamin B1 accumulation, nuclear shape alteration and senescence in the DDR syndrome, ataxia telangiectasia (A-T). Interestingly, overexpression of lamin B1 in wild type cells is sufficient to induce senescence without the induction of DNA damages. Here, we will discuss the importance of controlling the lamins level in order for maintenance nuclear architecture and we will comment the relationships of lamins with other senescence mechanisms. Finally, we will describe emerging data reporting redox control by lamins, leading us to propose a general mechanism by which reactive oxygen species can induce senescence through lamin dysregulation and NSA.

Barascu, Aurelia; Le Chalony, Catherine; Pennarun, Gaelle; Genet, Diane; Zaarour, Nancy; Bertrand, Pascale

2012-01-01

352

Fracture toughness and impact properties of laminated metal composites  

Microsoft Academic Search

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.

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

1996-01-01

353

Characterisation of fibre metal laminates under thermomechanical loadings  

Microsoft Academic Search

Fibre metal laminates, such as Arall or Glare, can offer improved properties compared to monolithic materials. Glare for example shows improved fatigue, residual strength, burn-through, impact and corrosion properties with respect to aluminium 2024, together with a considerable weight reduction and competitive costs. A large research program has proven the technological readiness of Glare and the fibre metal laminate has

M. Hagenbeek

2005-01-01

354

Prediction of progressive failure in multidirectional composite laminated panels  

Microsoft Academic Search

A mechanism-based progressive failure analyses (PFA) approach is developed for fiber reinforced composite laminates. Each ply of the laminate is modeled as a nonlinear elastic degrading lamina in a state of plane stress according to Schapery theory (ST). In this theory, each lamina degrades as characterized through laboratory scale experiments. In the fiber direction, elastic behavior prevails, however, in the

Shiladitya Basu; Anthony M. Waas; Damodar R. Ambur

2007-01-01

355

Bolted joints in a laminated composite strut design expert system  

Microsoft Academic Search

A knowledge-based expert system for the design and analysis of composite laminated struts with bolted joints is described. This system is part of a Composite Design Expert System aimed at performing analysis and design of composite laminated plates and struts and at assessing designs. The system uses a minimum weight optimization that satisfies the failure criteria of local and overall

C. M. L. Wu

1992-01-01

356

Identification of differential protein interactors of lamin A and progerin  

PubMed Central

The nuclear lamina is an interconnected meshwork of intermediate filament proteins underlying the nuclear envelope. The lamina is an important regulator of nuclear structural integrity as well as nuclear processes, including transcription, DNA replication and chromatin remodeling. The major components of the lamina are A- and B-type lamins. Mutations in lamins impair lamina functions and cause a set of highly tissue-specific diseases collectively referred to as laminopathies. The phenotypic diversity amongst laminopathies is hypothesized to be caused by mutations affecting specific protein interactions, possibly in a tissue-specific manner. Current technologies to identify interaction partners of lamin A and its mutants are hampered by the insoluble nature of lamina components. To overcome the limitations of current technologies, we developed and applied a novel, unbiased approach to identify lamin A-interacting proteins. This approach involves expression of the high-affinity OneSTrEP-tag, precipitation of lamin-protein complexes after reversible protein cross-linking and subsequent protein identification by mass spectrometry. We used this approach to identify in mouse embryonic fibroblasts and cardiac myocyte NklTAg cell lines proteins that interact with lamin A and its mutant isoform progerin, which causes the premature aging disorder Hutchinson-Gilford progeria syndrome (HGPS). We identified a total of 313 lamina-interacting proteins, including several novel lamin A interactors, and we characterize a set of 35 proteins which preferentially interact with lamin A or progerin.

Kubben, Nard; Voncken, Jan Willem; Demmers, Jeroen; Calis, Chantal; van Almen, Geert

2010-01-01

357

Fracture toughness and impact properties of laminated metal composites  

SciTech Connect

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.

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

1996-03-04

358

Strength and Modulus Degradation of CFRP Laminates from Fiber Misalignment  

Microsoft Academic Search

Fiber reinforced polymer (FRP) laminates are being used as external reinforcement for strengthening concrete members. The performance of unidirectional FRP laminates is highly dependent on fiber orientation with respect to applied load direction. In the case of fabrication by manual lay-up, it is possible to have fiber plies installed with improper orientation. In this project, the degradation of strength and

Xinbao Yang; Antonio Nanni; Stephen Haug; Chung Leung Sun

359

Composite laminate applications in magnetic fusion energy superconducting magnet systems  

Microsoft Academic Search

The application of advanced composite laminates in the cryogenic portion of magnetic fusion energy systems is considered. It is suggested that laminates, characterized by high modulus, low thermal conductivity, and high electrical conductivity, can substitute for stainless steel in some components of superconducting magnets. Thermal insulation, nonmetallic dewars, and superconducting composites are discussed. Problems associated with the use of current

M. B. Kasen

1978-01-01

360

A variational model of ferroelectric rank-2 laminate domain structures  

Microsoft Academic Search

The equilibrium domain arrangements of ferroelectric single crystals are significantly affected by loads and boundary conditions. Domain structures evolve towards a minimum energy state. In this paper, a variational method, which minimizes a functional based on free energy and dissipation, is developed to model the evolution of several typical rank-2 laminate domain patterns in the tetragonal crystal system. Periodic laminates

N. T. Tsou; J. E. Huber

2010-01-01

361

Fracture mechanics of laminated glass subjected to blast loading  

Microsoft Academic Search

A failure criterion based on energy balance approach is introduced for the laminated glass panel subjected to blast loading. Based on this failure criterion, a damage factor is developed to assess the failure of the laminated glass panel. If the damage factor is less than one, the plate is safe otherwise unsafe. Trigonometric function is employed to express the transverse

J. Wei; L. R. Dharani

2005-01-01

362

A finite element model for impact simulation with laminated glass  

Microsoft Academic Search

A computational technique for the modelling of laminated safety glass is presented using an explicit finite element solver. Coincident finite elements are used to model the layered set-up of laminated glass: shell elements with brittle failure for the glass components and membrane elements to simulate the ultimate load carrying capacity of the PVB-interlayer. Two different approaches are considered to model

M. Timmel; S. Kolling; P. Osterrieder; P. A. Du Bois

2007-01-01

363

Testing Of Laminated Glass for Bullet-Proof Capacity  

Microsoft Academic Search

The results of comparative testing of laminated glass fired at using a Makarov pistol are given. It is demonstrated that the use of glass sheets after special thermal treatment in laminated glass articles makes it possible to reduce their weight and the energy consumption and to improve the light transmission.

A. I. Shutov; I. A. Novikov; A. S. Bonchuk; A. N. Burdov; I. A. Shchetinina

2002-01-01

364

Comparison between laminated and integrated glass fibre reinforced plastics  

Microsoft Academic Search

Glass fibre reinforced honeycomb-like cores (I beam and T beam) with laminated and integrated structures were processed. They were tested for strength, and various analyses were carried out. Conventional glass fibre reinforced plastics are obtained by laminating two-dimensional fabrics with added resin. The material is liable to be broken or peeled apart between adjacent layers under repeated imposition of stress

Huang Gu

2000-01-01

365

The nucleoporin Nup88 is interacting with nuclear lamin A.  

PubMed

Nuclear pore complexes (NPCs) are embedded in the nuclear envelope (NE) and mediate bidirectional nucleocytoplasmic transport. Their spatial distribution in the NE is organized by the nuclear lamina, a meshwork of nuclear intermediate filament proteins. Major constituents of the nuclear lamina are A- and B-type lamins. In this work we show that the nuclear pore protein Nup88 binds lamin A in vitro and in vivo. The interaction is mediated by the N-terminus of Nup88, and Nup88 specifically binds the tail domain of lamin A but not of lamins B1 and B2. Expression of green fluorescent protein-tagged lamin A in cells causes a masking of binding sites for Nup88 antibodies in immunofluorescence assays, supporting the interaction of lamin A with Nup88 in a cellular context. The epitope masking disappears in cells expressing mutants of lamin A that are associated with laminopathic diseases. Consistently, an interaction of Nup88 with these mutants is disrupted in vitro. Immunoelectron microscopy using Xenopus laevis oocyte nuclei further revealed that Nup88 localizes to the cytoplasmic and nuclear face of the NPC. Together our data suggest that a pool of Nup88 on the nuclear side of the NPC provides a novel, unexpected binding site for nuclear lamin A. PMID:21289091

Lussi, Yvonne C; Hügi, Ilona; Laurell, Eva; Kutay, Ulrike; Fahrenkrog, Birthe

2011-02-02

366

The nucleoporin Nup88 is interacting with nuclear lamin A  

PubMed Central

Nuclear pore complexes (NPCs) are embedded in the nuclear envelope (NE) and mediate bidirectional nucleocytoplasmic transport. Their spatial distribution in the NE is organized by the nuclear lamina, a meshwork of nuclear intermediate filament proteins. Major constituents of the nuclear lamina are A- and B-type lamins. In this work we show that the nuclear pore protein Nup88 binds lamin A in vitro and in vivo. The interaction is mediated by the N-terminus of Nup88, and Nup88 specifically binds the tail domain of lamin A but not of lamins B1 and B2. Expression of green fluorescent protein–tagged lamin A in cells causes a masking of binding sites for Nup88 antibodies in immunofluorescence assays, supporting the interaction of lamin A with Nup88 in a cellular context. The epitope masking disappears in cells expressing mutants of lamin A that are associated with laminopathic diseases. Consistently, an interaction of Nup88 with these mutants is disrupted in vitro. Immunoelectron microscopy using Xenopus laevis oocyte nuclei further revealed that Nup88 localizes to the cytoplasmic and nuclear face of the NPC. Together our data suggest that a pool of Nup88 on the nuclear side of the NPC provides a novel, unexpected binding site for nuclear lamin A.

Lussi, Yvonne C.; Hugi, Ilona; Laurell, Eva; Kutay, Ulrike; Fahrenkrog, Birthe

2011-01-01

367

Experimental Design on Laminated Veneer Lumber Fiber Composite: Surface Enhancement  

Microsoft Academic Search

Thick laminate veneer lumber(LVL) fibre reinforced composites were constructed from the alternated perpendicularly arrayed of peeled rubber woods. Glass woven was laid in between the layers. Native golden teak veneers were used as faces. In house formulae epoxy was employed as wood adhesive. The hand lay-up laminate was cured at 150° C for 45 mins. The cut specimen was post

U. Meekum; Y. Mingmongkol

2010-01-01

368

Micro-crack ultrasound scattering in anisotropic composite laminates  

NASA Astrophysics Data System (ADS)

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.

Roberts, R. A.

2013-01-01

369

Application of the finite element method to laminated fiber composites  

Microsoft Academic Search

This thesis deals with the application of the Finite Element Method to the analysis of laminated fiber composites. Specifically, it addresses the problem of representing the variation of material properties through the element volume in order to reduce the number of degrees of freedom required to represent a laminated composite. This is accomplished by a modification in the evaluation of

Sohail A Umar-Khitab

1991-01-01

370

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

PubMed

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

Bere, T; Tundisi, J G

2010-11-01

371

Dissolution of Diatom Frustules and Silicon Cycling in Lake Michigan, U.S.A.  

National Technical Information Service (NTIS)

Diatoms require dissolved silicon for the formation of the silicate frustule that surrounds the cell. Potential sources of this silicon include dissolution of frustules produced by previous diatom communities, inputs of dissolved silicon from land drainag...

J. I. Parker H. L. Conway E. M. Yaguchi D. N. Edgington

1977-01-01

372

Numerical Comparison between Electronically Adiabatic and Diabatic Representations for Collinear Atom-Diatom Collisions.  

National Technical Information Service (NTIS)

Within the framework of quantum coupled-channel calculations on nonreactive atom-diatom collision systems involving two electronic potential surfaces, we test the electronically adiabatic representation obtained within the diatomics-in-molecules approxima...

I. H. Zimmerman T. F. George

1975-01-01

373

Development of New Genetic Manipulation Tools for Metabolic Engineering of Diatoms.  

National Technical Information Service (NTIS)

This project's goal was to develop genetic manipulation tools for metabolic engineering of diatoms for biodiesel lipid production and other purposes. New diatom selectable markers were tested, relying on mutations to antibiotic resistance in two ribosomal...

M. Hildebrand

2008-01-01

374

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...

375

Magnetoelectric laminate composites with prestress consideration  

NASA Astrophysics Data System (ADS)

The converse magnetoelectric effect of an asymmetric Piezo-fiber/Metglas bilayer laminate composite subjected to mechanical prestress is presented. The mechanical prestress is applied by either dc electric voltage bias or direct mechanical load bias. It is found that a mechanical prestress strongly influences the converse magnetoelectric coupling response. The optimum dc magnetic field bias shifts with different prestress and compressive stress requires higher dc magnetic field bias. Additionally, an optimum prestress exists to maximize the converse magnetoelectric response under certain dc magnetic field bias ranges. Therefore, in order to integrate magnetoelectric composite into actual structures, a proper prestress needs to be employed to maximize the CME coefficient.

Wu, Tao; Emmons, Michael; Bur, Alexandre; Sorge, Jian; Carman, Gregory P.

2010-03-01

376

Diatom Oxygen Isotope Vital Effects: Evidence From The Palaeo Record  

NASA Astrophysics Data System (ADS)

Diatom oxygen isotope measurements are commonly made on bulk mixed species assemblages due to the difficulty in purifying and separating individual taxa. As such, it is essential for vital effects in diatoms to be fully understood. Existing studies have suggested diatom oxygen isotope vital effects to be either non-existent or negligible. Here, we present a suite of diatom oxygen isotope data from the onset of major Northern Hemisphere Glaciation at ODP site 882 in the North West Pacific Ocean which display large offsets of up to 3.51 ‰ (mean = 1.14 ‰) between two different size fractions (75-150 ?m and >150 ?m) that are dominated by only two species: Coscinodiscus marginatus and Coscinodiscus radiatus. These offsets are most likely size related, although additional inter-species effects may also be important in determining the exact magnitude of the offsets. Consequently considerable care is needed when interpreting bulk diatom oxygen isotope data in relation to palaeoenvironmental change, especially when the amount of stratigraphical change is small.

Swann, G. E.; Leng, M. J.; Sloane, H. J.; Maslin, M. A.; Onodera, J.

2006-12-01

377

Diatoms in Southeast Pacific surface sediments reflect environmental properties  

NASA Astrophysics Data System (ADS)

Diatom abundance and assemblage composition determined for 47 surface sediment samples from the Southeast Pacific (50°S 15°N), combined with existing data for the Peru and Chile margins, demonstrate responses to regional temperature, upwelling, and productivity. High diatom abundances (# valves/g) mark the eastern equatorial Pacific upwelling and the coastal upwelling areas, in particular the upwelling centers off Peru. Freshwater diatoms reflect the low-salinity tongue off the Chilean fjords. Diatom species composition distinguishes between coastal and eastern equatorial Pacific upwelling conditions, and records sea-surface temperatures. Q-mode factor analysis defines five floral assemblages. Factors 1 and 4 determined by the genus Chaetoceros (F1) and Thalassionema (F4) reflect coastal and equatorial upwelling conditions, respectively. Factors 2 and 3 characterized by the genus Thalassiosira and Azpetia nodulifera can be associated with El Niño conditions. A 5th factor, described by Paralia sulcata, records a near-shore upwelling center off Point Concepción, central Chile. Statistical transfer functions relate diatom species percentages to sea-surface temperature and productivity with error estimates of ±0.9 °C and ±23 gC/m2 yr, respectively, and provide new tools for estimating past temperature and productivity along the west coast of South America.

Abrantes, F.; Lopes, C.; Mix, A.; Pisias, N.

2007-01-01

378

Developing a methodology for carbon isotope analysis of lacustrine diatoms.  

PubMed

Stable isotope analysis of sedimentary carbon in lakes can help reveal changes in terrestrial and aquatic carbon cycles. A method based on a single, photosynthetic organism, where host effects are minimised, should offer more precision than carbon isotope studies of bulk lake sediments. Here we report the development of a systematic method for use on fossil lacustrine diatom frustules, adapted from previous studies in marine environments. A step-wise cleaning experiment on diatomaceous lake sediments from Lake Challa, near Mount Kilimanjaro, was made to demonstrate the necessary treatment stages to remove external sedimentary carbon. Changes in soluble carbon compounds during these cleaning experiments were measured using gas chromatography/mass spectrometry (GC/MS). The mass spectrometry methods were refined to measure the small percentage of carbon in these samples and details of these methods are presented. Samples of cleaned diatoms containing <1% carbon yielded robust results. Carbon isotope analyses of diatom samples containing different species mixtures were performed and suggested that differences existed, although the effects lay within current experimental error and require further work. Unlike what was found in work on oxygen and silicon isotopes from diatom frustules, mineral contamination had no discernible impact on the diatom carbon isotope ratios from these sediments. The range of values found in the lakes investigated thus far can be interpreted with reference to the supply and nature of carbon from the catchment as well as to the demand generated from lake primary productivity. PMID:21594931

Hurrell, Elizabeth R; Barker, Philip A; Leng, Melanie J; Vane, Christopher H; Wynn, Peter; Kendrick, Chris P; Verschuren, Dirk; Street-Perrott, F Alayne

2011-06-15

379

Efficiency of the CO2-concentrating mechanism of diatoms  

PubMed Central

Diatoms are responsible for a large fraction of CO2 export to deep seawater, a process responsible for low modern-day CO2 concentrations in surface seawater and the atmosphere. Like other photosynthetic organisms, diatoms have adapted to these low ambient concentrations by operating a CO2 concentrating mechanism (CCM) to elevate the concentration of CO2 at the site of fixation. We used mass spectrometric measurements of passive and active cellular carbon fluxes and model simulations of these fluxes to better understand the stoichiometric and energetic efficiency and the physiological architecture of the diatom CCM. The membranes of diatoms are highly permeable to CO2, resulting in a large diffusive exchange of CO2 between the cell and external milieu. An active transport of carbon from the cytoplasm into the chloroplast is the main driver of the diatom CCM. Only one-third of this carbon flux is fixed photosynthetically, and the rest is lost by CO2 diffusion back to the cytoplasm. Both the passive influx of CO2 from the external medium and the recycling of the CO2 leaking out of the chloroplast are achieved by the activity of a carbonic anhydrase enzyme combined with the maintenance of a low concentration of HCO3? in the cytoplasm. To achieve the CO2 concentration necessary to saturate carbon fixation, the CO2 is most likely concentrated within the pyrenoid, an organelle within the chloroplast where the CO2-fixating enzyme is located.

Hopkinson, Brian M.; Dupont, Christopher L.; Allen, Andrew E.; Morel, Francois M. M.

2011-01-01

380

Neogene diatom and silicoflagellate biostratigraphy of Naples Beach, California  

SciTech Connect

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.

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

1986-04-01

381

Bacterial mediation of carbon fluxes during a diatom bloom in a mesocosm  

Microsoft Academic Search

Bacteria-diatom interactions were studied during a diatom bloom produced in a mesocosm, in the absence of metazoan grazers, in order to examine the significance of bacterial hydrolytic ectoenzymes in mediating carbon fluxes and influencing diatom aggregation. The abundances of bacteria and protozoa, the production rates and hydrolytic ectoenzyme activities (protease, ? and ? glucosidase and chitobiase) of attached and free

David C. Smith; Grieg F. Steward; Richard A. Long; Farooq Azam

1995-01-01

382

A comparison of diatom community structure on natural and artificial substrata  

Microsoft Academic Search

Artificial substrata have been used in diatom studies for almost 100 years. However, concern still exists over whether diatom communities developing on artificial substrata accurately represent communities developing on natural substrata. This study compares the diatom communities colonising glass slides and clay tiles in two coastal dune lakes, and compares these communities to the naturally occurring communities in the epipelon,

Kathryn H. Taffs; Jamie L. Corfield

2003-01-01

383

Influence of light and temperature on the growth rate of estuarine benthic diatoms in culture  

Microsoft Academic Search

Four species of estuarine benthic diatoms: Amphiprora c. f. paludosa W. Smith, Nitzschia c. f. dissipata (Kützing) Grunow, Navicula arenaria Donkin, and Nitzschia sigma (Kützing) W. Smith were grown in unialgal cultures. The growth rates of the diatoms were determined as the rate of increase of the chlorophyll a content of the cultures. The diatoms were cultured at different combinations

W. Admiraal

1976-01-01

384

The structure of diatom assemblages associated with Cladophora and sediments in a highland stream in Kenya  

Microsoft Academic Search

Epiphytic and epipelic diatoms were collected from six sites in the Njoro River, Kenya, during the dry season between January and March 1997. Diatom assemblage descriptors, such as composition, distribution, species diversity as well as diatom habitat preferences and growth-form guilds were considered. Human activities in the Njoro River watershed included small-scale livestock keeping, subsistence farming, horticultural farming, and canning

B. Mpawenayo; J. M. Mathooko

2005-01-01

385

Accumulation of 241Am by suspended matter, diatoms and aquatic weeds of the Yenisei River  

Microsoft Academic Search

In this work we experimentally estimated the capacities of the key components of the Yenisei River (Russia): particulate suspended matter (seston), diatom microalgae, and submerged macrophytes for accumulating 241Am from water. In our experiments large particles of seston (>8?m), comparable in size with diatoms, took up most of americium from water. The accumulation of americium by isolated diatom algae (Asterionella

T. A. Zotina; A. Ya. Bolsunovsky; L. G. Bondareva

2010-01-01

386

Diatom frustules show increased mechanical strength and altered valve morphology under iron limitation  

Microsoft Academic Search

Iron limitation often results in increased cellular silica contents of diatoms, suggesting that diatoms grow thicker and possibly mechanically stronger frustules when limited. We performed stability measurements for six diatom species grown under iron-limitation and iron-sufficient conditions. Frustule strength increased in all species when grown under iron limitation, with this effect being statistically significant for four of them. Valve morphology

S. Wilken; B. Hoffmann; N. Hersch; N. Kirchgessner; S. Dieluweit; W. Rubner; L. J. Hoffmann; R. Merkel; I. Peeken

2011-01-01

387

Dissolution of diatom frustules and silicon cycling in Lake Michigan, U. S. A  

Microsoft Academic Search

Diatoms require dissolved silicon for the formation of the silicate frustule that surrounds the cell. Potential sources of this silicon include dissolution of frustules produced by previous diatom communities, inputs of dissolved silicon from land drainage, and dissolution of silicate minerals. Results are reported from investigations on the relationship between diatom-frustule production, sedimentation, and dissolution to determine the importance and

J. I. Parker; H. L. Conway; E. M. Yaguchi; D. N. Edgington

1977-01-01

388

Diatom-inferred salinity in palaeolakes: An indirect tracer of climate change  

Microsoft Academic Search

Lakes in arid and semi-arid regions respond to climatic change through shifts in lake water volume and ionic concentration. Because diatom distribution is highly correlated with lake hydrochemistry, diatoms can be used to infer changes in salinity and brine composition and thus to infer past climates. Here we critically examine the use of diatom-inferred salinity as a climate proxy, with

Françoise Gasse; Philip Barker; Peter A. Gell; Sherilyn C. Fritz; Françoise Chalie

1997-01-01

389

Taxonomic composition of the epilithic diatom flora from rivers Vit and Osum, Bulgaria  

Microsoft Academic Search

This paper presents the epilithic diatom flora from rivers Vit and Osum. Twenty-eight sampling sites were chosen along the river catchments, from the springs to the inflows (the Danube River). A total of 114 diatom taxa (103 species and 11 varieties) from 36 genera were identified in the epilithon of the studied rivers. The epilithic diatom floras from rivers Vit

Rosalina Stancheva; Antonia Mancheva; Plamen Ivanov

2007-01-01

390

Benthic diatom communities in boreal streams: community structure in relation to environmental and spatial gradients  

Microsoft Academic Search

An important goal for community ecology is the characterization and prediction of changes in community patterns along environmental gradients. We aimed to identify the major environmental correlates of diatom distribution patterns in boreal running waters. We classified 197 stream sites based on their diatom flora. Direct ordination methods were then used to identify the key environmental determinants of this diatom-

Janne Soininen; Riku Paavola; Timo Muotka

2004-01-01

391

The amino acid and sugar composition of diatom cell-walls  

Microsoft Academic Search

The cell walls of diatoms consist of a silica frustule encased in an organic coating. Biochemical characterization of this coating should allow insight into: (1) the mechanism of silicification; (2) taxonomy and evolution of diatoms; (3) preservation of fossil frustules. The amino acid and sugar composition of cell walls from 6 diatom species have been elucidated. When compared to cellular

R. E. Hecky; K. Mopper; P. Kilham; E. T. Degens

1973-01-01

392

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

ERIC Educational Resources Information Center

|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…

Weber, Cornelius I.

393

Diatoms as a tool for reconstructing sedimentary environments in coastal wetlands; methodological aspects  

Microsoft Academic Search

This paper presents a method for reconstructing sedimentary environments on the basis of diatoms in clastic deposits of coastal wetlands. The method includes improvements and updates of previously described approaches of coding ecological data on diatom species for computer utilization and of combining diatom species into ecological groups, which are related to specific environments.

Peter C. Vos; Hein Wolf

1993-01-01

394

Extracellular Matrix Assembly in Diatoms (Bacillariophyceae)1  

PubMed Central

Achnanthes longipes is a marine, biofouling diatom that adheres to surfaces via adhesive polymers extruded during motility or organized into structures called stalks that contain three distinct regions: the pad, shaft, and collar. Four monoclonal antibodies (AL.C1–AL.C4) and antibodies from two uncloned hybridomas (AL.E1 and AL.E2) were raised against the extracellular adhesives of A. longipes. Antibodies were screened against a hot-water-insoluble/hot-bicarbonate-soluble-fraction. The hot-water-insoluble/hot-bicarbonate-soluble fraction was fractionated to yield polymers in three size ranges: F1, ? 20,000,000 Mr; F2, ?100,000 Mr; and F3, <10,000 Mr relative to dextran standards. The ?100,000-Mr fraction consisted of highly sulfated (approximately 11%) fucoglucuronogalactans (FGGs) and low-sulfate (approximately 2%) FGGs, whereas F1 was composed of O-linked FGG (F2)-polypeptide (F3) complexes. AL.C1, AL.C2, AL.C4, AL.E1, and AL.E2 recognized carbohydrate complementary regions on FGGs, with antigenicity dependent on fucosyl-containing side chains. AL.C3 was unique in that it had a lower affinity for FGGs and did not label any portion of the shaft. Enzyme-linked immunosorbent assay and immunocytochemistry indicated that low-sulfate FGGs are expelled from pores surrounding the raphe terminus, creating the cylindrical outer layers of the shaft, and that highly sulfated FGGs are extruded from the raphe, forming the central core. Antibody-labeling patterns and other evidence indicated that the shaft central-core region is related to material exuded from the raphe during cell motility.

Wustman, Brandon A.; Lind, Jan; Wetherbee, Richard; Gretz, Michael R.

1998-01-01

395

Barium uptake and adsorption in diatoms  

NASA Astrophysics Data System (ADS)

Using trace metal-defined culture conditions, we measured the cellular barium concentration in cultures of the diatom Thalassiosira weissflogii. In cultures with low Fe concentration, at a typical surface seawater Ba concentration of 35 to 40 nmol/L, the cellular Ba was 0.5 ?mol/mol P (˜0.04 ?g/g dw), much below all previously published values for phytoplankton. When the Fe concentration in the growth medium was increased, the measured "cellular" Ba increased proportionally to the particulate Fe. Under conditions of ferric hydroxide precipitation, similar particulate Ba concentrations were measured in the absence and the presence of cells for a given concentration of particulate Fe. Thus, the bulk of the particulate Ba in such experiments was not truly intracellular but adsorbed on precipitated Fe hydroxides associated with the cell surface. A similar mechanism likely explains the high cellular Ba concentrations reported by previous investigators who utilized relatively high ratios of Fe to EDTA concentrations in the growth medium, resulting in Fe precipitation. On the basis of our results, it seems highly unlikely that intracellular uptake by living phytoplankton explains the vertical flux of Ba in oceanic waters. But the adsorption of Ba on Fe hydroxides that is seen in laboratory experiments must also occur in the oceans and contribute to Ba transport in the upper part of the water column. To be significant, however, such a mechanism would require that the particles that transport Ba out of the surface have a markedly lower Ba/Fe ratio than is measured in the average suspended material.

Sternberg, Erika; Tang, Degui; Ho, Tung-Yuan; Jeandel, Catherine; Morel, François M. M.

2005-06-01

396

Chloroplast-mitochondria cross-talk in diatoms.  

PubMed

Diatoms are unicellular, mainly photosynthetic, eukaryotes living within elaborate silicified cell walls and believed to be responsible for around 40% of global primary productivity in the oceans. Their abundance in aquatic ecosystems is such that they have on different occasions been described as the insects, the weeds, or the cancer cells of the ocean. In contrast to higher plants and green algae which derive from a primary endosymbiosis, diatoms are now believed to originate from a serial secondary endosymbiosis involving both green and red algae and a heterotrophic exosymbiont host. As a consequence of their dynamic evolutionary history, they appear to have red algal-derived chloroplasts empowered largely by green algal proteins, working alongside mitochondria derived from the non-photosynthetic exosymbiont. This review will discuss the evidence for such an unusual assemblage of organelles in diatoms, and will present the evidence implying that it has enabled them with unorthodox metabolisms that may have contributed to their profound ecological success. PMID:22268145

Prihoda, Judit; Tanaka, Atsuko; de Paula, Wilson B M; Allen, John F; Tirichine, Leïla; Bowler, Chris

2012-01-20

397

Diatom response to extremely low-frequency magnetic fields  

SciTech Connect

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.

Parkinson, W.C.; Sulik, G.L. (Department of Physics, University of Michigan, Ann Arbor (United States))

1992-06-01

398

Understanding amine catalyzed silica polymerization : diatoms as bioarchitects.  

SciTech Connect

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

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

399

Integration of sensing networks into laminated composites  

NASA Astrophysics Data System (ADS)

We summarize the methodology that we have used to address integrating sensing network into composite materials for structural self diagnosis. First, we have examined the effect of stress concentration that arises due to the embedment of sensors and external devices on the strength and endurance of laminated glass fiber composites. To analyze the mechanical response of the composite material under study subjected to in-plane or impact loads, we have fabricated a series of samples, with and without embedded (dummy) sensors/micro-processors, using S2 glass fiber/epoxy, and have characterized their response by acoustic emission. Guided by the corresponding results, we can select sensors and other necessary components in such way as to minimize the impact of the embedded electronics on the material integrity and, at the same time, to implement acoustic sensing monitoring functionalities within the material. A 4-tree hierarchical network of PVDF sensors capable of acquiring signals typically related to resin micro cracking phenomena has been developed and partially integrated into a cross ply laminate. The achieved results and ongoing research will be discussed.

Ghezzo, Fabrizia; Rye, Patrick; Huang, Yi; Nemat-Nasser, Sia

2008-05-01

400

Laminated ceramic components for microfluidic applications  

NASA Astrophysics Data System (ADS)

Applications for micro fluidic components continue to expand as the benefits resulting from the small volumes and light weight of such devices are recognized. Such benefits are particularly attractive for man-portable and automotive devices where reduction of weight is critical. As applications expand, so too does the need for the development of methods for producing micro fluidic components from unconventional materials (i.e., materials other than silicon). At the Pacific Northwest National Laboratory, we are currently developing processes for producing laminated multilevel ceramic components containing microchannel features that will find applications in micro fluidic chemical processing and energy management systems. Thin layers of green ceramic tape are patterned with micro fluidic flow features using one of a number of cutting processes. The patterned layers are then stacked and laminated with other layers of green tape, ceramic plate, or other materials using a series of processing steps. The resulting monolithic, leak-tight micro fluidic ceramic components are capable of tolerating high temperature or chemically corrosive environments. Fabrication issues associated with the use of the green ceramic tape for this type of application will be discussed, and examples of test components produced using these processes will be presented.

Matson, Dean W.; Martin, Peter M.; Bennett, Wendy D.; Stewart, Donald C.; Bonham, Charles C.

1999-08-01

401

Deciphering diatom biochemical pathways via whole-cell proteomics  

PubMed Central

Diatoms play a critical role in the oceans’ carbon and silicon cycles; however, a mechanistic understanding of the biochemical processes that contribute to their ecological success remains elusive. Completion of the Thalassiosira pseudonana genome provided ‘blueprints’ for the potential biochemical machinery of diatoms, but offers only a limited insight into their biology under various environmental conditions. Using high-throughput shotgun proteomics, we identified a total of 1928 proteins expressed by T. pseudonana cultured under optimal growth conditions, enabling us to analyze this diatom’s primary metabolic and biosynthetic pathways. Of the proteins identified, 70% are involved in cellular metabolism, while 11% are involved in the transport of molecules. We identified all of the enzymes involved in the urea cycle, thereby describing the complete pathway to convert ammonia to urea, along with urea transporters, and the urea-degrading enzyme urease. Although metabolic exchange between these pathways remains ambiguous, their constitutive presence suggests complex intracellular nitrogen recycling. In addition, all C4 related enzymes for carbon fixation have been identified to be in abundance, with high protein sequence coverage. Quantification of mass spectra acquisitions demonstrated that the 20 most abundant proteins included an unexpectedly high expression of clathrin, which is the primary structural protein involved in endocytic transport. This result highlights a previously overlooked mechanism for the inter- and intra-cellular transport of nutrients and macromolecules in diatoms, potentially providing a missing link to organelle communication and metabolite exchange. Our results demonstrate the power of proteomics, and lay the groundwork for future comparative proteomic studies and directed analyses of specifically expressed proteins and biochemical pathways of oceanic diatoms.

Nunn, Brook L.; Aker, Jocelyn R.; Shaffer, Scott A.; Tsai, Shannon; Strzepek, Robert F.; Boyd, Philip W.; Freeman, Theodore Larson; Brittnacher, Mitchell; Malmstrom, Lars; Goodlett, David R.

2009-01-01

402

Diatom data from Bradley Lake, Oregon: downcore analyses  

USGS Publications Warehouse

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.

Hemphill-Haley, Eileen; Lewis, Roger C.

2003-01-01

403

The number of bound vibrational levels in a diatomic molecule  

NASA Astrophysics Data System (ADS)

A simple semiempirical expression has been developed for estimating the effective non-integer vibrational index at dissociation, ?D, in diatomic systems. The expression is given by,?D=1.78349×D?-58, where the dissociation energy and the fundamental vibrational frequency must be expressed in the same units. This expression gives reliable results for a wide variety of ground electronic states of neutral systems, but underestimates the vibrational index for diatomic cations, most excited states and zero bond-order molecules. The expression is successful for electronic states that have a Birge-Sponer plot displaying a downward curvature as the dissociation limit is approached.

Hajigeorgiou, Photos G.

2013-04-01

404

Biological monitoring of lotic ecosystems: the role of diatoms.  

PubMed

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

Bere, T; Tundisi, J G

2010-03-19

405

Distribution of Epiphytic Diatoms in a Sub-Tropical Estuary  

NASA Astrophysics Data System (ADS)

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.

Frankovich, T. A.; Gaiser, E. E.; Wachnicka, A.; Zieman, J. C.

2005-05-01

406

Ab initio calculations of the photoionization of diatomic molecules  

NASA Astrophysics Data System (ADS)

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.

Lefebvre-Brion, Helene; Ra?eev, Georges

2003-01-01

407

Modeling of atom-diatom scattering. Technical report  

SciTech Connect

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.

Sindoni, J.M.

1992-05-30

408

Ancient and modern laminated composites — from the Great Pyramid of Gizeh to Y2K  

Microsoft Academic Search

Laminated metal composites (LMCs) have been cited in antiquity; for example, an iron laminate that may date as far back as 2750 BC was found in the Great Pyramid in Gizeh in 1837. A laminated shield containing bronze, tin, and gold layers is described in detail by Homer. Well-known examples of steel laminates, such as an Adze blade, dating to

Jeffrey Wadsworth; Donald R Lesuer

2000-01-01

409

Electric Current Analysis for Thick Laminated CFRP Composites  

NASA Astrophysics Data System (ADS)

This paper deals with a new lamination theory to calculate the electric current density on carbon fiber reinforced plastic (CFRP) laminates. Unidirectional CFRP has strong orthotropic electric conductance. When electric current is applied to the surface of a CFRP plate, the electric voltage field is not uniform in the thickness direction for thick CFRP. The electric current concentrates near the surface where the electric current is applied to thick CFRP laminates. In this study, a new lamination theory for thick CFRP laminates is proposed. The theory for thick CFRP assumes a non-uniform electric voltage distribution in the thickness direction. For non-thick and non-thin CFRP plates, an approximation method is proposed. To obtain the shape of the non-uniform voltage distribution, the analytical results of thick unidirectional ply from a previous paper is adopted as a contribution function to calculate the effective conductance of the thick CFRP laminate. Cross-sectional two-dimensional (2D) FEM analysis is used to obtain the contribution function for the non-thick CFRP plate. The proposed methods are applied to two cases of the thick CFRP plates, and the results are compared with the three-dimensional (3D) FEM results. Consequently, the new lamination theory is shown to be very effective for the CFRP plates.

Todoroki, Akira

410

Interlaminate Deformation in Thermoplastic Composite Laminates: Experimental-Numerical Correlation  

NASA Astrophysics Data System (ADS)

The interlaminar deformation behaviors of thermoplastic AS4/PEEK composite laminates subjected to static tensile loading are investigated by means of microscopic moiré interferometry with high spatial resolution. The fully threedimensional orthotropic elastic-plastic analysis of interlaminar deformation for the thermoplastic laminates is developed in this paper, and used to simulate the stress-strain curves of tensile experiment for its angle-ply laminates. Under uniaxial tensile loading, the 3D orthotropic elastic-plastic FE analysis and microscopic moiré interferometry of interlaminar deformations are carried out for the [±25]S4 laminates. The quantitative local-filed experimental results of interlaminar shear strain and displacements at freeedge surface of the laminate are compared with corresponding numerical results of the orthotropic elastic-plastic FE model. It is indicated that the numerical tensile stressstrain curves of angle-ply laminates computed with 3D orthotropic elastic-plastic model are agree with experimental results. The numerical interlaminar displacement U and shear strain ?xz are also consistent with the experimental results obtained by moiré interferometry. It is expected the elastic-plastic interlaminar stresses and deformations analysis for the optimal design and application of AS4/PEEK laminates and its structures.

Shen, M.; Tong, J.; Wang, S.; Fang, Y.

2010-06-01

411

Mitotic lamin disassembly is triggered by lipid-mediated signaling  

PubMed Central

Disassembly of the nuclear lamina is a key step during open mitosis in higher eukaryotes. The activity of several kinases, including CDK1 (cyclin-dependent kinase 1) and protein kinase C (PKC), has been shown to trigger mitotic lamin disassembly, yet their precise contributions are unclear. In this study, we develop a quantitative imaging assay to study mitotic lamin B1 disassembly in living cells. We find that CDK1 and PKC act in concert to mediate phosphorylation-dependent lamin B1 disassembly during mitosis. Using ribonucleic acid interference (RNAi), we showed that diacylglycerol (DAG)-dependent PKCs triggered rate-limiting steps of lamin disassembly. RNAi-mediated depletion or chemical inhibition of lipins, enzymes that produce DAG, delayed lamin disassembly to a similar extent as does PKC inhibition/depletion. Furthermore, the delay of lamin B1 disassembly after lipin depletion could be rescued by the addition of DAG. These findings suggest that lipins activate a PKC-dependent pathway during mitotic lamin disassembly and provide evidence for a lipid-mediated mitotic signaling event.

Mall, Moritz; Walter, Thomas; Gorjanacz, Matyas; Davidson, Iain F.; Nga Ly-Hartig, Thi Bach; Ellenberg, Jan

2012-01-01

412

Nurturing the genome: A-type lamins preserve genomic stability.  

PubMed

A-type lamins provide a scaffold for tethering chromatin and protein complexes regulating nuclear structure and function. Interest in lamins increased after mutations in the LMNA gene were found to be associated with a variety of human disorders termed laminopathies. These include muscular dystrophy, cardiomyopathy, lipodystrophy, peripheral neuropathy and premature aging syndromes such as progeria. In addition, altered expression of A-type lamins is emerging as a contributing factor to tumorigenesis. How different alterations in a gene that is ubiquitously expressed can cause such an array of systemic as well as tissue specific diseases remains an enigma. Several lines of evidence indicate that mutant forms of A-type lamins impact on genome function and integrity. A current model suggests that genomic instability plays a major part in the pathophysiology of some lamin-related diseases. However, this model remains to be fully investigated. Here we discuss recent studies revealing novel functions for A-type lamins in the maintenance of telomeres and in the DNA damage response (DDR) pathway. These findings have shed some light onto the putative molecular mechanisms by which alterations in A-type lamins induce genomic instability and contribute to disease. PMID:21326943

Gonzalez-Suarez, Ignacio; Gonzalo, Susana

2009-11-29

413

The biology of biofouling diatoms and their role in the development of microbial slimes.  

PubMed

Diatoms are a major component of microbial slimes that develop on man-made surfaces placed in the marine environment. Toxic antifouling paints, as well as environmentally friendly, fouling-release coatings, tend to be effective against most fouling organisms, yet fail badly to diatom slimes. Biofouling diatoms have been found to tenaciously adhere to and colonise even the most resistant of artificial surfaces. This review covers the basic biology of fouling marine diatoms, their mechanisms of adhesion and the nature of their adhesives, as well as documenting the various approaches that have been utilised to understand the formation and maintenance of diatom biofouling layers. PMID:18604655

Molino, Paul J; Wetherbee, Richard

2008-01-01

414

Design and Experiments of Two Glued Axially-Laminated Synchronous Reluctance Permanent Magnetic Motors  

Microsoft Academic Search

Two axially-laminated glued axially-laminated synchronous reluctance permanent magnetic (SR-PM) motors are designed and tested. Compared to general axially-laminated synchronous reluctance (SR) motors, the steel bracket is replaced with iron lamination for reduction of iron loss in rotor. The axially-laminated iron and magnet are glued on the bracket with high strength cement with the help of special clamping device. Then the

Wei Guo; Zhengming Zhao

2005-01-01

415

Thermal buckling of thick antisymmetric angle-ply laminates  

SciTech Connect

The buckling behavior of moderately thick antisymmetric angle-ply laminates that are simply supported and subject to a uniform temperature rise is analyzed. Transverse shear deformation is accounted for by employing the thermoelastic version of the Reissner-Mindlin theory. Results for the classical thin-plate theory are obtained as a special case. Numerical results are presented for fiber-reinforced laminates and show the effects of ply orientation, number of layers, plate thickness, and aspect ratio on the critical buckling temperature. Finally, an optimization procedure is proposed for the design of laminates having maximum resistance to thermal buckling. 17 references.

Tauchert, T.R.

1987-01-01

416

Laminated metals composites fracture and ballistic impact behavior  

SciTech Connect

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.

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

1998-01-20

417

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

PubMed

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

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

2010-08-27

418

[Research on the universal analytic potential function applied to diatomic molecules].  

PubMed

A new method on constructing analytical potential energy functions is presented, and from this a analytical potential energy function applied to both neutral diatomic molecules and charged diatomic molecular ions is obtained. In this paper, the potential energy function is examined by 21 examples of eight different basic kinds of diatomic molecules or ions--homonuclear ground-state for neutral diatomic molecule Na2-X1 sigma g+, homonuclear excitation-state for neutral diatomic molecule C2-A1 pi(u), homonuclear ground-state for charged diatomic molecular ion He2+ -X2 sigma u+, homonuclear excitation-state for charged diatomic molecular ion N2+ -B2 sigma(u), heteronuclear ground-state for neutral diatomic molecule NaLi-X1 sigma g+, heteronuclear excitation-state neutral diatomic molecule BH-B1 sigma+, heteronuclear ground-state for charged diatomic molecular ion (BC)- -X3 pi, and heteronuclear excitation-state for charged diatomic molecular ion (CS)+ -A2 pi etc. The theoretical values of the vibrational energy level of molecules calculated by the potential energy function are compared with RKR (Rydberg-Klein-Rees) or experimental data, and as a consequence, all the results are precisely consistent with RKR data. PMID:23156751

Yu, Chang-feng

2012-08-01

419

Eddy current losses in ferromagnetic laminations  

SciTech Connect

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.

Serpico, C. [Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742 (United States); Visone, C. [Department of Electrical Engineering, University of Naples ''Federico II'', I-80152 Napoli, (Italy); Mayergoyz, I. D. [Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742 (United States); Basso, V. [IEN Galileo Ferraris, Corso M. d'Azeglio 41, I-10125 Torino, (Italy); Miano, G. [Department of Electrical Engineering, University of Naples ''Federico II'', I-80152 Napoli, (Italy)

2000-05-01

420

Laminated substrate for catalytic combustor reactor bed  

SciTech Connect

This patent describes a laminated catalyst element. It comprises a metal support substrate; a catalytically active noble metal oxidation resistant layer selected from the group consisting of platinum, palladium, rhodium, iridium, osmium and ruthenium, provided over the metal support substrate for preventing high temperature oxidation of the metal support substrate; a metal oxide coating, selected from the group consisting of alumina, zirconia and thoria, provided over the noble metal oxidation resistant layer; and a combustion catalyst selected from the group consisting of platinum, palladium, rhodium, iridium, chromium oxides, iron oxides, cobalt oxides, lanthanum oxides, terbium-cerium-thorium, ruthenium, osmium, nickel oxides, magnesium oxides and copper oxides, the combustion catalyst being provided on the metal oxide coating, and wherein the noble metal oxidation resistant layer provides a secondary source of combustion catalyst due to the catalytic activity thereof.

Beebe, K.W.

1991-09-10

421

Heterothallism in the pennate diatom Haslea ostrearia (Bacillariophyta)  

Microsoft Academic Search

Twelve clonal cultures of the marine pennate diatom Haslea ostrearia (Gaillon) Simonsen were used to study sexual reproduction and auxosporulation. After crossing, compatible gametangia paired girdle to girdle, with no visible surrounding mucilage. Two gametes were formed per gametangium; these were not attached to the thecae of the parental frustule and gametes from one gametangium fused with the gametes from

Nickolai A. Davidovich; Jean-Luc Mouget; Pierre Gaudin

2009-01-01

422

Configurations of polyunsaturated sesterterpenoids from the diatom, Haslea ostrearia  

Microsoft Academic Search

The partial configurations of C25 isoprenoid alkenes isolated from the diatom Haslea ostrearia Gaillon (Simonsen) have been established. A combination of NMR spectroscopy studies of the alkenes with chiral shift reagents in conjunction with soluble silver ?-diketonate complexes and enantioselective gas chromatography of oxidation products of the alkenes was used. Unexpected differences in highly branched isoprenoid isomer configurations were observed

Lesley Johns; Simon Belt; C. Anthony Lewis; Steven Rowland; Guillaume Massé; Jean-Michel Robert; Wilfried A. König

2000-01-01

423

Carbonic anhydrase activity and photosynthesis in marine diatoms  

Microsoft Academic Search

The photosynthesis and carbonic anhydrase activity of four marine diatoms currently found in oyster-ponds near the French Atlantic coast, Haslea ostrearia, Navicula phyllepta, Entomoneis paludosa and Amphora coffeaeformis, were investigated. Photosynthetic parameters determined from photosynthesis versus irradiance curves showed that A. coffeaeformis (a benthic species) had lower maximum net photosynthesis but a higher light utilization coefficient than the other species

Annick Morant-Manceau; Thi Le Nhung Nguyen; Elisabeth Pradier; Gerard Tremblin

2007-01-01

424

Distribution of copper in the diatom Haslea ostrearia simonsen  

Microsoft Academic Search

Haslea ostrearia is a pennate diatom important for oysters culture. This species was selected to study experimentally the distribution of copper in algal cells since the phytoplankton exhibits a high capacity for metal accumulation and thus influences metal transfer to consumers. This alga was grown in batch culture and exposed to copper (30 ?g\\/l) added in the medium on the

L. Joux-Arab; B. Berthet; J. M. Robert

1998-01-01

425

The paleoclimatology of Lake Baikal: A diatom synthesis and prospectus  

Microsoft Academic Search

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

Anson W. Mackay

2007-01-01

426

Authigenic smectite on diatom frustules in Bolivian saline lakes  

Microsoft Academic Search

Observation under the electron microscope of diatom frustules from Bolivian Altiplano saline lakes shows that many of these are coated with particles occurring as tiny sheets. The frustules can be found to be almost completely replaced by these sheets. Isolated sheet aggregates seem to have resulted from completely transformed frustules. Section observations of altered frustules bear out that the sheets

Denise Badaut; François Risacher

1983-01-01

427

THERMAL SCATTERING OF ATOMS BY HOMONUCLEAR DIATOMIC MOLECULES  

Microsoft Academic Search

The formal theory of scattering by a rigid rotator is applied to the ; problem of the rotational excitation and elastic scattering of homonuclear ; diatomic molecules by atoms. A statistical theory is employed to analyze the ; effects of the strong coupling that occurs between the different scattering ; channels. Numerical results are presented for the collision of argon

R. B. Bernstein; A. Dalgarno; H. Massey; I. C. Percival

1963-01-01

428

DIATOMIC MOLECULES OF ASTROPHYSICAL INTEREST: IONIZATION POTENTIALS AND DISSOCIATION ENERGIES  

Microsoft Academic Search

A critical analysis was made of the ionization potentials and ; dissociation energies of 148 diatomic molecules and molecular ions that have ; astrophysical significance. This summary provides useful data for the ; calculation of molecular abundances and for discussions of dissociation ; equllibria and ionization processes. It also points out the great need for ; further experimental and theoretical

P. G. Wilkinson

1963-01-01

429

Resonances of diatomic molecules in the born-oppenheimer approximation  

Microsoft Academic Search

We study the spectral properties of general diatomic molecules near a scattering level. We prove that in the Born-Oppenheimer approximation, this study can be reduced to the one of a a matrix of semiclassical pseudodifferential operators. More precisely, we provide a link between the resonances of the molecule which are close enough to the real axis, and the discrete spectrum

André Martinez; Bekkai Messirdi

1994-01-01

430

The noneouilibrium dissociation of diatomic molecules in a boundary layer  

Microsoft Academic Search

A study is made of the influence of the process of diffusion of diatomic molecules on the rate of their thermal dissociation. On the basis of the ladder model of the dissociation of molecules — truncated harmonic oscillators — an expression is obtained for the macroscopic reaction rate which depends explicitly and exponentially on the square of the gradient of

N. K. Makashev; V. P. Provotorov

1985-01-01

431

Two-photon absorption by rotating diatomic molecules  

Microsoft Academic Search

Explicit forms for the two-photon absorption cross section in linearly and circularly polarized light for rotating diatomic molecules have been developed. The ratio (???\\/?cc) of the cross sections for individual rotational transitions is precisely two-thirds for all branches of ?? = 0, ±1, ±2 transitions except for the unique case—the Q branch of a ??=0 transition. In the latter case

R. G. Bray; R. M. Hochstrasser

1976-01-01

432

Studies of dissociation of diatomic molecules with isotope spectroscopy  

Microsoft Academic Search

A method for studying dissociation of diatomic molecules by isotope spectroscopy is presented both theoretically and practically. A theory based on combinatorial analysis is presented for molecules of the form B2 and BC. Molecular dissociation rates can be calculated from measurements of isotope exchange provided the isotopes in the molecules can be considered as chemically equivalent. Dissociation measurements of O2

Erik Hörnlund

2002-01-01

433

Functionalized diatom silica microparticles for removal of mercury ions  

NASA Astrophysics Data System (ADS)

Diatom silica microparticles were chemically modified with self-assembled monolayers of 3-mercaptopropyl-trimethoxysilane (MPTMS), 3-aminopropyl-trimethoxysilane (APTES) and n-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPTMS), and their application for the adsorption of mercury ions (Hg(II)) is demonstrated. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy analyses revealed that the functional groups (-SH or -NH2) were successfully grafted onto the diatom silica surface. The kinetics and efficiency of Hg(II) adsorption were markedly improved by the chemical functionalization of diatom microparticles. The relationship among the type of functional groups, pH and adsorption efficiency of mercury ions was established. The Hg(II) adsorption reached equilibrium within 60 min with maximum adsorption capacities of 185.2, 131.7 and 169.5 mg g-1 for particles functionalized with MPTMS, APTES and AEAPTMS, respectively. The adsorption behavior followed a pseudo-second-order reaction model and Langmuirian isotherm. These results show that mercapto- or amino-functionalized diatom microparticles are promising natural, cost-effective and environmentally benign adsorbents suitable for the removal of mercury ions from aqueous solutions.

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

2012-02-01

434

Intrinsic photoluminescence of diatom shells in sensing applications  

NASA Astrophysics Data System (ADS)

Diatoms are monocellular micro-algae provided with external valves, the frustules, made of amorphous hydrated silica. Frustules present patterns of regular arrays of holes, the areolae, characterized by sub-micrometric dimensions. Frustules from centric diatoms are characterized by a radial disposition of areolae and exhibit several optical properties, such as photoluminescence, lens-like behavior and, in general, photonic-crystal-like behavior as long as confinement of electromagnetic field is concerned. In particular, intrinsic photoluminescence from frustules is strongly influenced by the surrounding atmosphere: on exposure to gases, the induced luminescence changes both in the optical intensity and peaks positions. To give specificity against a target analyte, a key feature for an optical sensor, a biomolecular probe, which naturally recognizes its ligand, can be covalently linked to the diatom surface. We explored the photoluminescence emission properties of frustules of Coscinodiscus wailesii centric species, characterized by a diameter of about 100-200 ?m, on exposure to different vapours and in presence of specific bioprobes interacting with target analytes. Very high sensitivities have been observed due to the characteristic morphology of diatoms shells. Particular attention has been devoted to the emission properties of single frustules.

de Tommasi, E.; Rendina, I.; Rea, I.; de Stefano, M.; Lamberti, A.; de Stefano, L.

2009-05-01

435

Trace Elements in Diatom Frustules as a Paleochemical Proxy  

Microsoft Academic Search

The calibration in modern environments of the different proxies used in any paleoenvironmental study is a critical aspect leading to more realistic reconstructions of past conditions. Diatoms are among the main contributors to phytoplankton blooms in both lakes and oceans. They have been widely used as ecological and biogeochemical indicators of present and former environmental conditions. During the formation of

T. Jaccard; D. Ariztegui

2003-01-01

436

The insidious effect of diatoms on copepod reproduction  

NASA Astrophysics Data System (ADS)

The productive regions of the ocean are characterized by seasonal blooms of phytoplankton which are generally dominated by diatoms. This algal class has, therefore, traditionally been regarded as providing the bulk of the food that sustains the marine food chain to top consumers and important fisheries. However, this beneficial role has recently been questioned on the basis of laboratory studies showing that although dominant zooplankton grazers such as copepods feed extensively on diatoms, the hatching success of eggs thus produced is seriously impaired. Here we present evidence from the field showing that the hatching success of wild copepods feeding on a diatom-dominated bloom is also heavily compromised, with only 12% of the eggs hatching compared with 90% in post-bloom conditions. We report on the structure of the three aldehydes isolated from diatoms that are responsible for this biological activity, and show that these compounds arrest embryonic development in copepod and sea urchin bioassays and have antiproliferative and apoptotic effects on human carcinoma cells.

Miralto, A.; Barone, G.; Romano, G.; Poulet, S. A.; Ianora, A.; Russo, G. L.; Buttino, I.; Mazzarella, G.; Laabir, M.; Cabrini, M.; Giacobbe, M. G.

1999-11-01

437

Does sediment grain size affect diatom grazing by harpacticoid copepods?  

PubMed

Estuarine soft sediments support a diverse group of eukaryotic and prokaryotic organisms though the role of the sediment per se for the functioning of these organisms remains largely unknown. The present study aimed to test the effect of sediment grain size on the grazing activities of harpacticoid copepods. In controlled experiments, two common intertidal harpacticoid species (Paramphiascella fulvofasciata and Nitokra spinipes) were each offered a mix of two benthic diatom species (Navicula phyllepta and Seminavis robusta) in different sedimentary conditions. Several microcosms were created using a variety of sediment types, including fine silt (<63 microm), coarser grained sands (125-250, 250-450, 100-300 microm), artificial 'sediments' of glass beads (250-500, 2000 microm) and even the absence of sediment was tested. The diatoms were enriched in the stable carbon (13)C to facilitate tracing in the harpacticoids. Both copepod species were able to graze on the diatoms with highest uptake when sediment was absent. In contrast, both harpacticoid species showed no uptake in silty conditions. In general, grazing was favoured when mean sediment grain size increased. The strong negative effect of fine grains on the grazer's efficiency can be explained by the resulting differences in the structure (and accessibility) of the diatom biofilm on the one hand and the mobility of the grazer on the other hand. In view of the subtle equilibrium between primary producers and grazers, these results might have important implications for the effect of siltation of tidal flats due to, e.g., human activities. PMID:16343608

De Troch, Marleen; Houthoofd, Lieven; Chepurnov, Victor; Vanreusel, Ann

2005-12-15

438

A Diatom-based, Paleolimnological Study Of Rush Lake, Wisconsin  

NASA Astrophysics Data System (ADS)

Rush Lake, located in Winnebago County, Wisconsin, is a shallow, eutrophic, lake/wetland dominated by cattails. This system has historically been important for fishing and waterfowl production. But recently the general public view the lake as degraded from increased sedimentation, contamination from lead shot, and perceived reduction in fish and wildlife. A sediment core (374cm) was taken by employing a modified Livingstone piston corer. The core sample was dated with carbon-14 yielding a date at the base of the core of 4110 +/- 40 yr. B.P. The core sediments were sampled for diatoms starting at 5cm for every 10cm after that (37 samples). Diatoms were counted for a total of 300 per sample. Typical of shallow lakes, the core showed signs of being extensively reworked. Despite this, multivariate analysis of diatoms (PCA) suggests that this system has become more eutrophic. This is consistent with a pollen analysis and is likely due to agricultural activities in the watershed. There is no evidence (i.e., increase in % planktonic diatoms) that the lake had ever developed a pelagic zone for an extended period of time. Results of this study may be useful in making future management decisions to restore Rush Lake.

Fischer-Guex, L.; Pillsbury, R. W.; Mode, W.

2005-05-01

439

Dissociation of Diatomic Molecule by Speed-Gradient Feedback Control  

Microsoft Academic Search

New method for dissociation of diatomic molecule based on nonperiodic excitation generated by speed-gradient feedback control mechanism is proposed. The speed-gradient algorithm does not depend on the shape of the potential energy of molecule. It is shown that the feedback control is more ecien t then methods based on constant frequency and linear chirping excitations. Eciency of the proposed method

Fradkov Alexander; Krivtsov Anton

440

The Buoyancy of Plankton Diatoms: A Problem of Cell Physiology  

Microsoft Academic Search

Observations on pure cultures of diatoms and the results of centrifuge experiments showed that under optimal conditions the vegetative cells have the same specific gravity as sea water. The specific gravity of resting spores is significantly higher than that of sea water. Hence the specific gravity of the cell sap which fills the bulk of the vegetative cell and is

F. Gross; E. Zeuthen

1948-01-01

441

Diatom assemblages from Costa Rican lakes: an initial ecological assessment  

Microsoft Academic Search

We compared the distributions of 59 diatom species in surface sediments of 25 Costa Rican lakes with 21 environmental variables using canonical correspondence analysis (CCA). The distribution of taxa was related to the chemical and physical characteristics of the lakes. The most influential chemical variables were cation concentrations (especially magnesium) and related variables such as water hardness, pH, and temperature.

Kurt A. Haberyan; Sally P. Horn; Brian F. Cumming

1997-01-01

442

Infrared Spectroscopy of Diatomic Molecules — a Fractional Calculus Approach  

NASA Astrophysics Data System (ADS)

The eigenvalue spectrum of the fractional quantum harmonic oscillator is calculated numerically, solving the fractional Schrödinger equation based on the Riemann and Caputo definition of a fractional derivative. The fractional approach allows a smooth transition between vibrational and rotational type spectra, which is shown to be an appropriate tool to analyze IR spectra of diatomic molecules.

Herrmann, Richard

2013-03-01

443

Collective excitations in a three-dimensional diatomic Penrose lattice  

Microsoft Academic Search

We present detailed investigations of the vibrational modes in a three-dimensional diatomic Penrose lattice. The vibrational densities of states are calculated using a recursion technique. These spectra show an apparently branched structure, we classify the branches by means of the same convention as used for crystals. The acoustic branches appear to be smooth and continuous and exhibit a linear feature

Ying Hu; Decheng Tian; Zhengyou Liu

1994-01-01

444

Diatom frustules as light traps enhance DSSC efficiency  

NASA Astrophysics Data System (ADS)

Diatoms are one of the most successful photosynthetic organisms and given the important role that their shells (frustules) play in light trapping we explored their use in multilayered materials for application as photoanodes in dye sensitised solar cells (DSSCs). We find a substantial improvement in energy conversion efficiency of 30%, increasing from 3.5% to 4.6% with diatom incorporation.Diatoms are one of the most successful photosynthetic organisms and given the important role that their shells (frustules) play in light trapping we explored their use in multilayered materials for application as photoanodes in dye sensitised solar cells (DSSCs). We find a substantial improvement in energy conversion efficiency of 30%, increasing from 3.5% to 4.6% with diatom incorporation. Electronic supplementary information (ESI) available: Materials and method, AFM of pristine frustules and frustules after a single cycle. XRD of the frustules after 1 cycle and calcination at 500 °C for four hours. See DOI: 10.1039/c2nr32716c

Toster, Jeremiah; Iyer, K. Swaminathan; Xiang, Wanchun; Rosei, Federico; Spiccia, Leone; Raston, Colin L.

2013-01-01

445

Diatom plastids depend on nucleotide import from the cytosol  

PubMed Central

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.

Ast, Michelle; Gruber, Ansgar; Schmitz-Esser, Stephan; Neuhaus, Horst Ekkehard; Kroth, Peter G.; Horn, Matthias; Haferkamp, Ilka

2009-01-01

446

HISTORICAL PROCESSES CONSTRAIN PATTERNS IN GLOBAL DIATOM DIVERSITY  

Microsoft Academic Search

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

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

2007-01-01

447

THE CONCEPTUAL BASIS OF ECOLOGICAL-STATUS ASSESSMENTS USING DIATOMS  

Microsoft Academic Search

Most member states of the EU have chosen to use existing diatom-based metrics for assessment of ecological status, as required by the Water Framework Directive (WFD), rather than develop new methods. In this paper we assess the suitability of such methods in light of the requirements of the normative defi nitions of ecological status. In particular, we focus on the

Martyn Kelly; Lydia King; Bernadette Ní Chatháin

2009-01-01

448

Comparison of two domoic acid-producing diatoms: a review  

Microsoft Academic Search

In the past five years, awareness of domoic acid has increased from localized problems in Canada to outbreaks along both North American coasts. The phycotoxin domoic acid causes Amnesic Shellfish Poisoning (ASP) in humans and can be fatal. The known species of phytoplankton responsible for production of domoic acid include some pennate diatom species of the genus Nitzschia, sensu latu,

M. C. Villac; D. L. Roelke; T. A. Villareal; G. A. Fryxell

1993-01-01

449

Transformation of Nonselectable Reporter Genes in Marine Diatoms.  

PubMed

: We report the genetic transformation of two marine diatoms by microparticle bombardment. The pennate diatom Phaeodactylum tricornutum was transformed with the bacterial gene Sh ble from Streptoalloteichus hindustanus, which confers resistance to the antibiotics phleomycin and zeocin. Transformants contained between 1 and 10 copies of the exogenous DNA integrated into the genome by illegitimate recombination at apparently random locations. Transformation efficiencies were around 10(-6), and individual cell lines could be maintained at -80 degrees C following cryopreservation. Also, P. tricornutum could be transformed simultaneously with two different plasmids, one containing the Sh ble gene and another containing the firefly luciferase gene (LUC) under control of a promoter derived from a fucoxanthin, chlorophyll a/c-binding protein gene (FCP). In these cotransformants, LUC activity was light inducible. The transient transformation of the centric diatom Thalassiosira weissflogii with the bacterial beta-glucuronidase (GUS) gene has also been achieved using similar transformation technology. The availability of gene transfer protocols for marine diatoms, together with a range of functional reporter genes and regulated expression systems, will permit molecular dissection of their biology and allow an assessment of the biotechnological potential of these organisms. PMID:10383998

Falciatore; Casotti; Leblanc; Abrescia; Bowler

1999-05-01

450

Cadmium: A nutrient for the marine diatom Thalassiosira weissflogii  

Microsoft Academic Search

Although cadmium is known to be very toxic, it exhibits nutrientlike vertical concentration profiles in the open ocean. Recent work has shown that under conditions of zinc limitation, cadmium enhances the growth of the marine diatom Thalassiosira weissflogii. Here, we conclusively demonstrate that Cd is a nutrient for T. weissjlogii at inorganic Zn and Cd concentrations typical of surface seawater,

JENNIFER G. LEE; SAMANTHA B. ROBERTS; FRANÇOIS M. M. MOREL

1995-01-01

451

Using laser scattering to identify diatoms and conduct aggregation experiments  

Microsoft Academic Search

Laser in situ scattering and transmissometry (LISST) instruments are used to measure particle size distributions (PSDs) and volume concentrations in water. For populations of regularly shaped non-spherical particles, such as phytoplankton, the PSD produces a ‘scattering signature’ that corresponds to the shape of the particles. The objectives of this research were to describe the scattering signatures of six diatom species

Charles E. Rzadkowolski; Daniel C. O. Thornton

2012-01-01

452

The life of diatoms in the world's oceans  

Microsoft Academic Search

Marine diatoms rose to prominence about 100 million years ago and today generate most of the organic matter that serves as food for life in the sea. They exist in a dilute world where compounds essential for growth are recycled and shared, and they greatly influence global climate, atmospheric carbon dioxide concentration and marine ecosystem function. How these essential organisms

E. Virginia Armbrust

2009-01-01

453

The effect of drugs on diatom valve morphogenesis  

Microsoft Academic Search

Summary The effects of various drugs on cell wall (valve) morphogenesis was investigated in three species of diatoms (Pinnularia spp., Surirella robusta, andHantzschia amphioxys) using light microscopy (LM) and scanning electron microscopy (SEM). Treatment ofSurirella with the microtubule (MT) disrupting agent colchicine during early valve formation results in a characteristic malformation of the valve, whereby part of the normally circumferential

S. A. Cohn; Juli Nash; J. D. Pickett-Heaps

1989-01-01

454

Diatom Data from Bradley Lake, Oregon: Downcore Analyses.  

National Technical Information Service (NTIS)

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 d...

E. Hemphill-Haley R. C. Lewis

2003-01-01

455

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...

456

Fecal Pellets: Role in Sedimentation of Pelagic Diatoms  

Microsoft Academic Search

Membrane-enclosed fecal pellets of planktonic herbivores were sampled at several depths in the Baltic Sea (459 meters deep) and off Portugal (4000 meters deep) by means of a Simonsen multinet. Pellets contained mainly empty shells of planktonic diatoms and silicoflagellates. Two kinds of fecal pellets were found, those with the remains of one species (for example, Thalassiosira baltica) and those

Hans-Joachim Schrader

1971-01-01

457

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...

458

New tools for labeling silica in living diatoms  

Microsoft Academic Search

Summary • Silicon biomineralization is a widespread mechanism found in several kingdoms that concerns both unicellular and multicellular organisms. As a result of genomic and molecular tools, diatoms have emerged as a good model for biomineralization studies and have provided most of the current knowledge on this process. However, the number of techniques available to study its dynamics at the

Julien Desclés; Mathieu Vartanian; Abdeslam El Harrak; Michelle Quinet; Nicolas Bremond; Guillaume Sapriel; Jérome Bibette; Pascal J. Lopez

2008-01-01

459

Fracture of Ti-Al 3 Ti metal-intermetallic laminate composites: Effects of lamination on resistance-curve behavior  

Microsoft Academic Search

The fracture toughness and resistance-curve (R-curve) behavior of Ti-Al3Ti metal-intermetallic laminate (MIL) composites have been studied in the crack-divider orientation, by examining the effect\\u000a of ductile-laminate-layer thickness and volume fraction. The MIL composites were fabricated in open air by a novel one-step\\u000a process, and the final structure consists of alternating layers of ductile Ti and brittle Al3Ti. Such a laminate

Raghavendra R. Adharapurapu; Kenneth S. Vecchio; Fengchun Jiang; Aashish Rohatgi

2005-01-01

460

Diatom proteomics reveals unique acclimation strategies to mitigate fe limitation.  

PubMed

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

Nunn, Brook L; Faux, Jessica F; Hippmann, Anna A; Maldonado, Maria T; Harvey, H Rodger; Goodlett, David R; Boyd, Philip W; Strzepek, Robert F

2013-10-16

461

Diatom Proteomics Reveals Unique Acclimation Strategies to Mitigate Fe Limitation  

PubMed Central

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.

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

462

Adiabatic principles in atom-diatom collisional energy transfer  

SciTech Connect

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.

Hovingh, W.J.

1993-01-01

463

Fossilized diatoms in meteorites from recent falls in Sri Lanka  

NASA Astrophysics Data System (ADS)

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.

Hoover, Richard B.; Wallis, Jamie; Wickramarathne, Keerthi; Samaranayake, Anil; Williams, George; Jerman, Gregory; Wallis, D. H.; Wickramasinghe, N. C.

2013-09-01

464

Damage Processes and Fracture Surface Morphology in Laminated Composites.  

National Technical Information Service (NTIS)

Because of complex mechanical behavior of laminated composite materials, the failure processes of these materials are often ill-understood. This is of particular importance when the issue of composite fracture testing is considered. Without an adequate un...

B. H. Fortson

1990-01-01

465

Performance of stress-laminated timber highway bridges in cold ...  

Treesearch

Bar-force and temperature data from a subset of bridges were continuously monitored ... testing, composite materials, loads, temperature, laminated wood, moisture, ... weathering, weather, cold, low temperatures, preservatives, timber bridges, ...

466

Fineblanking, Diffusion Bonding, and Testing of Fluidic Laminates.  

National Technical Information Service (NTIS)

Two manufacturing processes that show promise of improving the performance of laminated aluminum fluidic components are fineblanking and semi-solid-state diffusion bonding. A representative three-stage amplifier design was used as the basis for evaluating...

L. K. Pecan

1980-01-01

467

Optimal Design of Pitched Tapered Laminated Wood Beams.  

National Technical Information Service (NTIS)

The optimal design of a pitched tapered laminated woood beam is considered. An engineering formulation is given in which the volume of the beam is minimized. The problem is then reformulated and solved as a generalized geometric (signomial) program. Sampl...

J. D. Barrett M. Avriel

1976-01-01

468

Species Response to Prestress in Curved Laminated Wood BEAMS.  

National Technical Information Service (NTIS)

Individual species differ in their response to the prestressing that is involved in the forming of curved laminated members. These differences can be attributed to the magnitude of the stress developed which varies with species, to possible damage that ma...

F. F. Wangaard G. E. Woodson M. R. Murray

1968-01-01

469

Soy adhesives that can form durable bonds for plywood, laminated ...  

Treesearch

Title: Soy adhesives that can form durable bonds for plywood, laminated ... dispersing/denaturating conditions, cross-linking chemistry, and bonding conditions. ... upon flour type, as well as adhesive formulation and processing conditions.

470

A Theory for Predicting Composite Laminate Warpage Resulting from Fabrication.  

National Technical Information Service (NTIS)

Linear laminate theory is used with the moment-curvature relationship to derive equations for predicting end deflections due to warpage without solving the coupled fourth-order partial differential equations of the plate. Composite micro- and macrohyphenm...

C. C. Chamis

1974-01-01

471

Laminated rare earth structure and method of making  

DOEpatents

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.

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

2002-07-30

472

Comparison of Goretex Laminated and Dermoflex Coated Fabrics.  

National Technical Information Service (NTIS)

Two fabrics, a polyester/cotton fabric laminated with Goretex, and a nylon fabric coated with Dermoflex, were proposed for the prototype Arctic clothing system. Samples of each fabric were subjected to various physical tests, both before and after launder...

P. A. Dolhan

1989-01-01

473

Comparison of Goretex Laminated and Dermoflex Coated Fabrics.  

National Technical Information Service (NTIS)

Two fabrics, a polyester/cotton fabric laminated with Goretex, and a nylon fabricated coated with Dermoflex, were proposed for the prototype Arctic clothing system. Samples of each fabric were subjected to various physical tests, both before and after lau...

P. A. Dolhan

1989-01-01

474

Buckling of Cylindrical Sandwich Panels with Laminated Faces.  

National Technical Information Service (NTIS)

General stability of a cylindrically curved sandwich panel with laminated composite face sheets is considered. The analysis accounts for axial compression, edgewise shear, or combined loadings. A mathematical model is formulated, based upon a linear poten...

R. A. Brockman

1977-01-01

475

78 FR 23591 - Certain Prepregs, Laminates, and Finished Circuit Boards  

Federal Register 2010, 2011, 2012, 2013

...issued notice of its determination not to review an ID terminating the investigation as to respondents VENTEC Electronics (Suzhou) Co., Ltd., VENTEC Electronics (HK) Co., Ltd., and VENTEC-Global Laminates USA LLC based on a consent order....

2013-04-19

476

Higher-Order Shear Deformation Theory of Laminated Elastic Shells.  

National Technical Information Service (NTIS)

A higher-order shear deformation theory of elastic shells is developed for shells laminated of orthotropic layers. The theory is a modification of the Sanders' theory and accounts for parabolic distribution of the transverse shear strains through thicknes...

J. N. Reddy C. F. Liu

1985-01-01

477

Laminated Object Manufacturing-Based Design Ceramic Matrix Composites.  

National Technical Information Service (NTIS)

Tbis report summarizes the significant accomplishments of the Laminated Object Manufacturing Based Design for Ceramic Matrix Composites Program. The overall objective of the twenty-seven month long effort was to further develop LOM based solid freeform fa...

R. Mailunas

2001-01-01

478

Blunt Notch Behaviour of Metal Laminates: Arall and Glare.  

National Technical Information Service (NTIS)

The use of stress concentration factor to describe blunt notch properties of ARALL is evaluated. The blunt notch theory for aluminum alloys is discussed. Results for ARALL laminates are discussed and a test series is proposed. The stress concentration fac...

C. A. J. R. Vermeeren

1990-01-01