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1

Microfabric analysis of laminated diatom ooze (Holocene) from the eastern Bransfield Strait, Antarctic Peninsula  

Microsoft Academic Search

Selected intervals of laminated diatom ooze (Holocene) from the eastern Bransfield Strait, Antarctic Peninsula were analyzed\\u000a using high-resolution section images of impregnated samples to reveal potential annual-to-seasonal scale signatures of the\\u000a lamination. The results show a probable seasonality within individual diatom ooze laminae which mainly reflects spring blooms\\u000a ofChaetoceros followed by summer production ofCorethron orRhizosolenia. Alternating monospecific diatom ooze and

Jang Jun Bahk; Ho Il Yoon; Yeadong Kim; Cheon Yun Kang; Sung Ho Bae

2003-01-01

2

I. Grigorov et al. / Deep-Sea Research II 49 (2002) 33913407, DOI: 10.1016/S0967-0645(02)00089-9 Southern Ocean laminated diatom ooze: mat deposits and  

E-print Network

I. Grigorov et al. / Deep-Sea Research II 49 (2002) 3391­3407, DOI: 10.1016/S0967-0645(02)00089-9 Southern Ocean laminated diatom ooze: mat deposits and potential for palaeo-flux studies, ODP leg 177, Site 1093 Ivo Grigorov*, Richard B. Pearce, Alan E.S. Kemp *School of Ocean and Earth Science, National

Paris-Sud XI, Université de

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

Persisting maximum Agulhas leakage during MIS 14 indicated by massive Ethmodiscus oozes in the subtropical South Atlantic  

NASA Astrophysics Data System (ADS)

The glacial marine isotope stage 14 (MIS 14) appears in many climate records as an unusually warm glacial. During this period an almost monospecific, up to 1.5 m thick, laminated layer of the giant diatom Ethmodiscus rex has been deposited below the South Atlantic Subtropical Gyre. This oligotrophic region is today less favorable for diatom growth with sediments typically consisting of calcareous nannofossil oozes. We have reconstructed temperatures and the stable oxygen isotopic compositions of sea surface and thermocline water (?18Ow) from planktonic foraminiferal (Globigerinoides ruber and Globorotalia inflata) Mg/Ca and stable oxygen isotopes to test whether perturbations in surface ocean conditions contributed to the deposition of the diatom layer at 530 kyr B.P. Temperatures and ?18Ow values reconstructed from this diatom ooze interval are highly variable, with maxima similar to interglacial values. Since the area of the Ethmodiscus oozes resembles the region where Agulhas rings are present, we interpret these hydrographic changes to reflect the varying influence of warm and saline water of Indian Ocean origin that entered the Subtropical Gyre trapped in Agulhas rings. The formation of the Ethmodiscus oozes is associated with a period of maximum Agulhas leakage and a maximum frequency of Agulhas ring formation caused by a termination-type position of the Subtropical Front during the unusual warm MIS 14. The input of silica through the Agulhas rings enabled the shift in primary production from calcareous nannoplankton to diatoms, leading to the deposition of the massive diatom oozes.

Rackebrandt, Nick; Kuhnert, Henning; Groeneveld, Jeroen; Bickert, Torsten

2011-09-01

5

A laminated sediment sequence from the northern North Atlantic Ocean and its climatic record  

Microsoft Academic Search

A remarkable 3-m-thick sequence of laminated diatom ooze (LDO) has been recovered in the North Atlantic Ocean. The LDO is monospecific and consists of the pennate diatom Thalassiothrix longissima. Biostratigraphy and benthic oxygen isotope stratigraphy indicate that the LDO was deposited during substage 5e (Eem). In analogy to recent observations of massive surface concentrations of diatoms in the equatorial Pacific

Per Bodn; Jan Backman

1996-01-01

6

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

NASA Astrophysics Data System (ADS)

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

Ishikawa, S.; Kaoru, K.

2013-12-01

7

Choose Your Ooze  

NSDL National Science Digital Library

During this activity, learners will make different versions of "ooze" using varied proportions of detergent and glue. Learners will observe, evaluate, and document different ooze properties by varying their recipes. Extensions provided on page 13. Part of the 21-activity guide published by OMSI, No Hassle Messy Science with a Wow. All activities in this guide use household materials and all lesson plans include preparation directions, demonstrations, procedure sheets, cross-curricular connections, and scientific explanation of content.

Industry, Oregon M.

2007-01-01

8

Diatoms  

USGS Multimedia Gallery

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

9

Diatoms  

USGS Multimedia Gallery

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

10

Diatoms  

USGS Multimedia Gallery

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

11

Diatoms  

USGS Multimedia Gallery

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

12

Diatoms  

USGS Multimedia Gallery

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

13

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

14

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

15

Early Middle Eocene Palaeoenvironments and Biostratigraphy of the Lomonosov Ridge: A Diatom and Chrysophyte Perspective  

NASA Astrophysics Data System (ADS)

The Arctic Coring Expedition (ACEX), Integrated Ocean Drilling Program Leg 302 recovered sediment cores from the Lomonosov Ridge to >400 meters below seafloor (mbsf). Dark grey mud-bearing organic-rich laminated biosiliceous ooze, between ~200-300 mbsf in Holes M0002A and M0004A, are Middle Eocene in age and contain shallow water marine diatoms in good preservation with abundances on the order of 106-107 valves/gram. The highest levels of biogenic silica, and the best siliceous microfossil preservation, occur below 220 mbsf, corresponding to Lithostratigraphic Unit 2. The diatoms occur in conjunction with variable abundances of other marine to brackish siliceous microfossils (ebridians, silicoflagellates and endoskeletal dinoflagellates) as well as diverse assemblages of freshwater chrysophyte cysts and marine and terrestrial palynomorphs. There are clear and frequent changes in dominance between the main siliceous microfossil groups, reflecting of an extraordinary depositional environment where both shallow marine and freshwater influences prevailed. We quantify these changes for the diatoms and chrysophytes. While the cyclical nature of these inferred salinity changes is under investigation, we report here on the broad scale variation in biosiliceous components through the Middle Eocene focusing in particular on the diatom and chrysophyte changes. Our initial results highlight the potential for an integrated regional diatom biostratigraphy for the Middle Eocene of the Arctic and Barents Sea, and indicate basin-wide palaeo-environmental fluctuations on long and short timescales. This poster outlines the various lines of work we are currently exploring in more detail.

Stickley, C.; Koc, N.; Jordan, R.; Suto, I.

2006-12-01

16

Sound velocities in calcareous oozes and chalks from sonobuoy data: Ontong Java plateau, western equatorial Pacific  

Microsoft Academic Search

The Ontong Java Plateau, in the western equatorial Pacific Ocean, is blanketed by over 1 km of flatlying, highly stratified calcareous ooze, chalk, and limestone. Wide-angle reflection data from 17 sonobuoys deployed over the plateau were analyzed for compressional wave velocities in these sediments. No particular velocity horizons stand out as prominent features that can be correlated from one sonobuoy

Thomas C. Johnson; Edwin L. Hamilton; Richard T. Bachman; Wolfgang H. Berger

1978-01-01

17

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

18

Laminate article  

DOEpatents

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

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

2002-01-01

19

Diatoms (50 Species)  

USGS Multimedia Gallery

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

20

Diatoms (50 Species)  

USGS Multimedia Gallery

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

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

Paleoenvironmental inferences from diatom assemblages of the middle Miocene Shanwang Formation, Shandong, China  

Microsoft Academic Search

Diatoms were analyzed in a laminated sediment sequence from the middle Miocene, lacustrine Shanwang Formation, Shandong Province,\\u000a eastern China, to reconstruct past conditions in the lake and evaluate relationships between inferred changes in the aquatic\\u000a and terrestrial environments. Changes in the diatom assemblages over the 22.9-m-long sediment sequence were used to assign\\u000a 19 lithologic layers to five zones. In Zone

Ya-Meng Li; David K. Ferguson; Yu-Fei Wang; Cheng-Sen Li

2010-01-01

23

Diatoms (50 Species)  

USGS Multimedia Gallery

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

24

Diatomic Spectral Database  

National Institute of Standards and Technology Data Gateway

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

25

Lamin-binding Proteins  

PubMed Central

A- and B-type lamins are the major intermediate filaments of the nucleus. Lamins engage in a plethora of stable and transient interactions, near the inner nuclear membrane and throughout the nucleus. Lamin-binding proteins serve an amazingly diverse range of functions. Numerous inner-membrane proteins help anchor lamin filaments to the nuclear envelope, serving as part of the nuclear lamina network that is essential for nuclear architecture and integrity. Certain lamin-binding proteins of the inner membrane bind partners in the outer membrane and mechanically link lamins to the cytoskeleton. Inside the nucleus, lamin-binding proteins appear to serve as the adaptors by which the lamina organizes chromatin, influences gene expression and epigenetic regulation, and modulates signaling pathways. Transient interactions of lamins with key components of the transcription and replication machinery may provide an additional level of regulation or support to these essential events. PMID:20452940

Wilson, Katherine L.; Foisner, Roland

2010-01-01

26

Flex circuit lamination  

NASA Astrophysics Data System (ADS)

Lamination process characteristics -- load, relative humidity, and lamination press pad -- were investigated as they relate to dimensional stability, voids, and 90-degree peel strength. Quantitative data was gathered for dimensional stability and voids. A predictive model was developed for peel strength. At the completion of the above activities, it was evident that a better understanding of the fundamental lamination process was needed. A Machine/Process Capability Study will be performed on the lamination process.

Wolfe, L.

1992-06-01

27

The lamin protein family.  

PubMed

The lamins are the major architectural proteins of the animal cell nucleus. Lamins line the inside of the nuclear membrane, where they provide a platform for the binding of proteins and chromatin and confer mechanical stability. They have been implicated in a wide range of nuclear functions, including higher-order genome organization, chromatin regulation, transcription, DNA replication and DNA repair. The lamins are members of the intermediate filament (IF) family of proteins, which constitute a major component of the cytoskeleton. Lamins are the only nuclear IFs and are the ancestral founders of the IF protein superfamily. Lamins polymerize into fibers forming a complex protein meshwork in vivo and, like all IF proteins, have a tripartite structure with two globular head and tail domains flanking a central ?-helical rod domain, which supports the formation of higher-order polymers. Mutations in lamins cause a large number of diverse human diseases, collectively known as the laminopathies, underscoring their functional importance. PMID:21639948

Dittmer, Travis A; Misteli, Tom

2011-01-01

28

The lamin protein family  

PubMed Central

Summary The lamins are the major architectural proteins of the animal cell nucleus. Lamins line the inside of the nuclear membrane, where they provide a platform for the binding of proteins and chromatin and confer mechanical stability. They have been implicated in a wide range of nuclear functions, including higher-order genome organization, chromatin regulation, transcription, DNA replication and DNA repair. The lamins are members of the intermediate filament (IF) family of proteins, which constitute a major component of the cytoskeleton. Lamins are the only nuclear IFs and are the ancestral founders of the IF protein superfamily. Lamins polymerize into fibers forming a complex protein meshwork in vivo and, like all IF proteins, have a tripartite structure with two globular head and tail domains flanking a central ?-helical rod domain, which supports the formation of higher-order polymers. Mutations in lamins cause a large number of diverse human diseases, collectively known as the laminopathies, underscoring their functional importance. PMID:21639948

2011-01-01

29

Nuclear Lamins and Neurobiology  

PubMed Central

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

Jung, Hea-Jin; Lee, John M.

2014-01-01

30

Sr / Ca ratios as indicators of varying modes of pelagic carbonate diagenesis in the ooze, chalk and limestone realms  

NASA Astrophysics Data System (ADS)

There has been an interest in the application of Sr / Ca ratios in pelagic carbonates to reconstruct paleoceanographic conditions such as changes in the oceanic Ca and Sr budgets or calcareous nannoplankton productivity, but the effect of burial diagenesis on primary Sr / Ca records has not been sufficiently understood. In order to clearly document Sr / Ca records of pelagic carbonates relative to original paleoceanography or secondary diagenetic processes, Sr / Ca analyses were performed on bulk sediments from an 822.5 m-thick ooze-chalk-limestone sequence at the Mid-Pacific Mountains, Deep Sea Drilling Project Site 463. The Sr / Ca ratios exponentially decrease from 2.3 to 1.1 mmol/mol with increasing burial depth in the ooze-chalk interval (0-452.0 m below seafloor (mbsf)). The Sr / Ca ratios further decline to as low as 0.4 mmol/mol in the limestone interval (> 452.0 mbsf), with relatively high values of > 1.1 mmol/mol at carbonate-poor lithology around 620 mbsf. The stratigraphic Sr / Ca trends appear to be consistent with porosity profile, and similar Sr / Caporosity covariation in association with diagnetic changes in lithologies is also common in Ontong Java Plateau sections. By adopting a recent diagenetic model from backscattered electron image analysis of Ontong Java Plateau sections, it is postulated for Site 463 that exponential Sr / Ca decrease in the ooze-chalk interval is due to the release of Sr into interstitial water via recrystallization (i.e., purification effect), and that further decrease in Sr / Ca ratios in the limestone interval is most likely due to acquisition of Sr-depleted calcite cement at the 'chalk-limestone transition' (newly proposed as the dilution effect). Specifically, Sr / Ca ratios of deeply buried pelagic limestones are sensitive to the amount of calcite cement that is acquired in proportion to CaCO 3 content; i.e., carbonate-rich lithology facilitates precipitation of secondary calcite at the chalk-limestone transition. Therefore, paleoceanographic interpretation by means of Sr / Ca ratios in pelagic carbonates will become valid only when these diagenetic effects are appropriately constrained.

Ando, Atsushi; Kawahata, Hodaka; Kakegawa, Takeshi

2006-09-01

31

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

32

Flexible thermal laminate  

NASA Technical Reports Server (NTRS)

Lightweight flexible laminate of interwoven conducting and insulating yarns, designed to provide localized controlled heating for propellant tanks on space vehicles, is useful for nonspace applications where weight, bulk, and flexibility are critical concerns.

Dawn, F. S.; Sauers, D. G.

1977-01-01

33

Lamination cooling system formation method  

SciTech Connect

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

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

2012-06-19

34

Lamination cooling system formation method  

DOEpatents

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

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

2009-05-12

35

Diatomic gasdynamic lasers.  

NASA Technical Reports Server (NTRS)

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

Mckenzie, R. L.

1972-01-01

36

Diatomic gasdynamic lasers  

NASA Technical Reports Server (NTRS)

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

Mckenzie, R. L.

1971-01-01

37

A historical perspective of laminitis.  

PubMed

The causes of laminitis are many-often interrelated, sometimes direct opposites. The history of laminitis has been a search for the cause or causes of laminitis and for effective treatment. Going in and out of fashion, many treatments have lasted for centuries, some for millennia, but very few have been proven. PMID:20381731

Heymering, Henry W

2010-04-01

38

Laminates and reinforced metals  

NASA Technical Reports Server (NTRS)

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

Chamis, C. C.

1980-01-01

39

Characteristics and temporal significance of middle Eocene laminated sediments from the central Arctic  

NASA Astrophysics Data System (ADS)

We present initial microfabric analysis of organic-rich, finely-laminated middle Eocene biosiliceous sediments from the Integrated Ocean Drilling Program Expedition 302 ACEX cores (central Arctic, Lomonosov Ridge). Scanning electron microscope backscattered electron imagery (BSEI) of polished thin sections and secondary electron imagery (SEI) of lamina-parallel fracture surfaces are used to analyse the laminations in several short sedimentary intervals dated as 49-44 Ma. Our data offer insight into the early cryospheric history of the central Arctic from a siliceous microfossil perspective during a significant phase in Cenozoic climate evolutionthe start of the transition from a greenhouse to an icehouse world. The sediments are rich in heavily-silicified endemic marine to brackish (diatoms, ebridians, silicoflagellates) and in-situ freshwater (chrysophyte cysts) siliceous microfossils. They also contain the weakly silicified needle-like diatom Synedropsis spp., an indicator of sea ice and the worlds oldest known fossil record of sea ice diatoms. Their presence highlights an exceptional preservational environment along the Lomonosov Ridge at this time. Synedropsis spp. show the Arctic Ocean supported sea ice-based life in the middle Eocene, and that melting episodes allowed their preservation in the sediments. Initial investigations indicate Synedropsis spp. form mono-specific laminations or elongate lenses normally always in association with sea ice rafted debris, that likely indicate discrete episodes of productivity and flux of this enigmatic diatom. We attempt to understand the temporal significance of these productivity events by examining their thickness, continuity and sequential relationship with other laminations/lenses in the scanning electron microscope. The task is challenging since the ACEX sediments are highly disturbed/desiccated in places. However, the BSEI technique offers an extraordinary detail of information, which can not be achieved by bulk sediment analysis alone. Our initial investigations give clues about the formation of this rich sediment archive before and after sea ice initiation, and the effects that global cooling had on the central Arctic marine ecosystem.

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

2010-12-01

40

Teen Moon: Moon Ooze  

NSDL National Science Digital Library

In this activity, learners model how the Moon's volcanic period reshaped its earlier features. Learners consider that the broad, shallow impact basins--which had formed earlier while it was a "kid Moon"--contained cracks through which magma seeped up. A plate in which slits have been cut is used to represent an impact basin and a dish of red-colored water is used to represent the pockets of magma within the Moon's upper layers. When the model impact basin is pressed into the magma, "lava" fills in the low areas through the same process that produced the dark patches, or maria, on the Moon. Learners may examine a type of Earth rock (named basalt) that is also found on the Moon and that would have been shaped by the processes explored here. This activity investigates the Moon's "teen years," when it was one to three billion years old.

This activity station is part of a sequence of stations that can be set up to help learners trace the Moon's 4.5-billion-year history from "infancy" to the imagined future. Learners tie together major events in the Moon's geologic history as a series of comic panels in their Marvel Moon comic books.

2014-07-01

41

Thermally stable laminating resins  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

42

Fast mixing by lamination  

Microsoft Academic Search

A micro mixer based on multi-stage multi-layer lamination is presented. The micro mixer has been designed as an integrated part of a micromachined chemical analysis system. The fabrication technology is based on wet chemical etching of PYREX-glass and silicon substrates which are subsequently bonded anodically. The micro mixer is designed to work in the flow range 1-10 ?l\\/min with a

Jens Branebjerg; Peter Gravesen; Jens Peter Krog; Claus Rye Nielsen

1996-01-01

43

Laminated piezoelectric transformer  

NASA Technical Reports Server (NTRS)

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

Vazquez Carazo, Alfredo (Inventor)

2006-01-01

44

Solar cell module lamination process  

DOEpatents

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

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

2002-01-01

45

Beach lamination: Nature and origin  

USGS Publications Warehouse

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

Clifton, H.E.

1969-01-01

46

Thermal conductivity of graphene laminate.  

PubMed

We have investigated thermal conductivity of graphene laminate films deposited on polyethylene terephthalate substrates. Two types of graphene laminate were studied, as deposited and compressed, in order to determine the physical parameters affecting the heat conduction the most. The measurements were performed using the optothermal Raman technique and a set of suspended samples with the graphene laminate thickness from 9 to 44 ?m. The thermal conductivity of graphene laminate was found to be in the range from 40 to 90 W/mK at room temperature. It was found unexpectedly that the average size and the alignment of graphene flakes are more important parameters defining the heat conduction than the mass density of the graphene laminate. The thermal conductivity scales up linearly with the average graphene flake size in both uncompressed and compressed laminates. The compressed laminates have higher thermal conductivity for the same average flake size owing to better flake alignment. Coating plastic materials with thin graphene laminate films that have up to 600 higher thermal conductivity than plastics may have important practical implications. PMID:25111490

Malekpour, H; Chang, K-H; Chen, J-C; Lu, C-Y; Nika, D L; Novoselov, K S; Balandin, A A

2014-09-10

47

Experimental Studies on Sexual Reproduction in Diatoms  

Microsoft Academic Search

The diatoms are the most speciose group of algae, having global ecological significance in the carbon and silicon cycles. They are almost unique among algae in being diplontic, and sexual reproduction is an obligate stage in the life cycle of most diatom species. It is unclear which are the principal factors that have fostered the evolutionary success of diatoms, but

Victor A. Chepurnov; David G. Mann; Koen Sabbe; Wim Vyverman

2004-01-01

48

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....

49

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.

LuAnn Dahlman

50

Vacuum lamination of photovoltaic modules  

NASA Technical Reports Server (NTRS)

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

Burger, D. R.

1982-01-01

51

Laminated electromagnetic pump stator core  

DOEpatents

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

Fanning, A.W.

1995-08-08

52

Laminated electromagnetic pump stator core  

SciTech Connect

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

Fanning, Alan W. (San Jose, CA)

1995-01-01

53

DIATOMS: One-Celled Wonders  

NSDL National Science Digital Library

Diatoms (DIE-a-toms) are one of the most important things you never knew about. They are everywhere there is water. A drop of lake water is packed with them. You probably swallow millions every time you go swimming. These tiny, one-celled life forms populate the world's ponds, rivers, and oceans (and anywhere else that's the least bit wet). They spend their invisible lives quietly using sunlight to turn carbon dioxide and water into food and oxygen. Diatoms are the basis of the food chain, and they produce much of the oxygen you breathe. This free selection about this one-celled wonder includes Part I of a sample activity from the book.

Allison, Linda; Disbrow, Sarah

2006-01-01

54

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

55

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

PubMed

The diatoms are ubiquitous, exist in large numbers and show a great diversity of features on their porous silica structures. Therefore, they inspire the fabrication of nanostructured templates for nanoimprint processes (NIL), where large structured areas with nanometer precision are required. In this study, two approaches regarding the respective challenges and potential exploitations are followed and discussed: the first one takes advantage of a template that is directly made of natural occurring diatoms. Here, two replication steps via soft lithography are needed to obtain a template which is subsequently used for NIL. The second approach exploits the technical capabilities of the precise 3D laser lithography (3DLL) based on two-photon polymerization of organic materials. This method enables the fabrication of arbitrary artificial diatom-inspired micro- and nanostructures and the design of an inverse structure. Therefore, only one replication step is needed to obtain a template for NIL. In both approaches, a replication technique for true 3D structures is shown. PMID:24343246

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

2014-03-01

56

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

57

Lamin A, farnesylation and aging  

SciTech Connect

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.

Reddy, Sita [Department of Biochemistry and Molecular Biology, Institute for Genetic Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033 (United States)] [Department of Biochemistry and Molecular Biology, Institute for Genetic Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033 (United States); Comai, Lucio, E-mail: comai@usc.edu [Department of Molecular Microbiology and Immunology, Institute for Genetic Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033 (United States)] [Department of Molecular Microbiology and Immunology, Institute for Genetic Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033 (United States)

2012-01-01

58

Manufacture and Mechanical Properties of Nanocomposite Laminates  

Microsoft Academic Search

This work mainly aims to manufacture nanocomposite laminates at first. The prepreg AS-4 graphite\\/PolyEtherEtherKetone laminates were used to make a 16-layered APC-2 laminate of 2 mm thick via curing the modified diaphragm. The nanoparticles of Silica (SiO2) were uniformly spread on the specific interfaces totally about 1-3% by weight of a laminate by sol-gel method. Second, by the results of

Ming-Hwa R. Jen; Yu-Chung Tseng; Chun-Hsien Wu

59

Collisions (2D) between diatomic molecules  

Microsoft Academic Search

The formalism to deal with collisions between two rigid bodies of arbitrary shape in two dimensions is described. This formalism is applied to the collision between rigid diatomic molecules. A simulation to show the behavior of a diatomic gas has been developed, and the Principle of Equipartition of Energy is explicitly demonstrated

E. Martin; R. Chicon

1996-01-01

60

Evaluation of European diatom trophic indices  

Microsoft Academic Search

Freshwater diatoms are considered to be reliable indicators of the trophic status of rivers and lakes. In the past 30 years, a number of indicator indices have been developed and used for the assessment of trophic conditions all over Europe. It is however still not clear whether the ecologic signature of diatoms differs between these indicator indices. The present study

Anna Besse-Lototskaya; Piet F. M. Verdonschot; Michel Coste; Bart Van de Vijver

2011-01-01

61

Structureandmetalexchangeinthecadmium carbonic anhydrase of marine diatoms  

E-print Network

ARTICLES Structureandmetalexchangeinthecadmium carbonic anhydrase of marine diatoms Yan Xu1 *, Liang Feng2 *{, Philip D. Jeffrey2 *, Yigong Shi2 & Franc¸ois M. M. Morel3 Carbonic anhydrase, a zinc, diatoms use cadmium as a catalytic metal atom in cadmium carbonic anhydrase (CDCA). Here we report

Morel, François M. M.

62

Basic mechanics of laminated composite plates  

NASA Technical Reports Server (NTRS)

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

Nettles, Alan T.

1994-01-01

63

Steady state response of unsymmetrically laminated plates  

SciTech Connect

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

Hosokawa, Kenji; Kawashima, Katsuya; Sakata, Toshiyuki [Chubu Univ., Kasugai, Aichi (Japan). Dept. of Mechanical Engineering

1995-11-01

64

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; Frderic 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; Jrome Fournet; Miyoshi Haruta; Marie J. J. Huysman; Bethany D. Jenkins; Katerina Jiroutova; Richard E. Jorgensen; Yolaine Joubert; Aaron Kaplan; Nils Krger; Peter G. Kroth; Julie La Roche; Erica Lindquist; Markus Lommer; Vronique Martin-Jzquel; 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

65

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

66

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

67

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.

2007-09-01

68

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

69

Diatoms in biotechnology: modern tools and applications.  

PubMed

Diatoms have played a decisive role in the ecosystem for millions of years as one of the foremost set of oxygen synthesizers on earth and as one of the most important sources of biomass in oceans. Previously, diatoms have been almost exclusively limited to academic research with little consideration of their practical uses beyond the most rudimentary of applications. Efforts have been made to establish them as decisively useful in such commercial and industrial applications as the carbon neutral synthesis of fuels, pharmaceuticals, health foods, biomolecules, materials relevant to nanotechnology, and bioremediators of contaminated water. Progress in the technologies of diatom molecular biology such as genome projects from model organisms, as well as culturing conditions and photobioreactor efficiency, may be able to be combined in the near future to make diatoms a lucrative source of novel substances with widespread relevance. PMID:19082585

Bozarth, Andrew; Maier, Uwe-G; Zauner, Stefan

2009-02-01

70

Laminated composite disc flywheel development  

NASA Astrophysics Data System (ADS)

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

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

1980-02-01

71

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

Federal Register 2010, 2011, 2012, 2013

...337-TA-874] Certain Products Having Laminated Packaging, Laminated Packaging, and Components Thereof; Commission Decision...complaint and amended complaint filed by Lamina Packaging Innovations, Inc. of Longview, Texas...

2013-08-12

72

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

73

Geometrically nonlinear analysis of laminated elastic structures  

NASA Technical Reports Server (NTRS)

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

Reddy, J. N.

1984-01-01

74

Lamins at the crossroads of mechanosignaling  

PubMed Central

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

Osmanagic-Myers, Selma; Dechat, Thomas

2015-01-01

75

Primordial Ooze and Continental Drift  

NSDL National Science Digital Library

In this lesson, students will learn that continental plates drift and this affects the layers of the earth. Following a directed reading and discussion, they will perform an experiment in which they use chocolate frosting and graham crackers to simulate tectonic plates sliding about on the mantle.

76

Symmetries in laminated composite plates  

NASA Technical Reports Server (NTRS)

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

Noor, A. K.

1976-01-01

77

Impact damage in composite laminates  

NASA Technical Reports Server (NTRS)

Damage tolerance requirements have become an important consideration in the design and fabrication of composite structural components for modern aircraft. The ability of a component to contain a flaw of a given size without serious loss of its structural integrity is of prime concern. Composite laminates are particularly susceptible to damage caused by transverse impact loading. The ongoing program described is aimed at developing experimental and analytical methods that can be used to assess damage tolerance capabilities in composite structures subjected to impulsive loading. Some significant results of this work and the methodology used to obtain them are outlined.

Grady, Joseph E.

1988-01-01

78

Extremophile Diatoms: Implications to the Drake Equation  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

79

Improved Fire-Resistant Resins for Laminates  

NASA Technical Reports Server (NTRS)

Fire-resistant resins for fabricating laminates with inorganic fibers, especially graphite fibers, are formed from bisimides containing main-chain phosphorus and olefinic end groups. Bisimides are thermally polymerized to form resins and laminates virtually imcombustible in pure oxygen at 300 degrees C. New resins are suitable for many applications requiring good adhesion and excellent resistance to heat, fire, solvents and chemicals.

Fohlen, G. M.; Parker, J. A.; Varma, I. K.

1982-01-01

80

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

PubMed

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

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

2014-07-01

81

A capillarity mechanism for diatom gliding locomotion.  

PubMed

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

Gordon, R; Drum, R W

1970-09-01

82

A Capillarity Mechanism for Diatom Gliding Locomotion  

PubMed Central

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

Gordon, Richard; Drum, Ryan W.

1970-01-01

83

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

84

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...

85

Nitrogen isotopic relationship between diatom-bound and bulk organic matter of cultured polar diatoms  

NASA Astrophysics Data System (ADS)

Using batch cultures, the 15N/14N (hereafter ?15N) of diatom-bound organic matter was measured and compared to the ?15N of total diatom biomass during the progressive consumption of a nitrate pool in four polar diatom species (Fragilariopsis cylindrus, Fragilariopsis kerguelensis, Pseudo-nitzschia seriata, and Thalassiosira nordenskioeldii) and one temperate species (Thalassiosira aestivalis). In general, the ?15N of the dissolved nitrate in seawater was greater than that of the biomass, which was greater than that of the diatom-bound N. Rayleigh-type relationships were observed, allowing for estimation of the isotope effect (?) for each species, with a range from 1.0 to 14.0 across all species. For all cultured strains, the ?15N values of the diatom-bound (?15NDB) fraction was lower than those of the total diatom biomass (?15Nbiomass). The isotopic offset between the biomass and diatom-bound N (?15NDBoffset = ?15Nbiomass - ?15NDB) was relatively constant along the growth curve for each individual species but varied among species, with a range of 1.9-11.2. Weak relationships were determined when ? and the ?15NDBoffset were compared to cellular size and surface area:volume ratio. More significantly, with the exception of Pseudo-nitzschia seriata, a strong positive relationship was found between ? and ?15NDBoffset. While the culture data indicate a positive ?15NDBoffset across all studied diatom species, surface sediment data suggest a negative ?15NDBoffset for sedimentary assemblages. This indicates that either (1) the growth conditions of our cultures had some effect on ?15NDBoffset or (2) a low-?15N component of the N that we measure as diatom frustule-bound is lost during early diagenesis. Given documented assemblage changes, our culture data for relevant species do not suggest that the higher ?15NDB observed in the Antarctic during ice ages can be explained by species related changes in the sedimentary bulk-to-diatom-bound isotopic difference. Future work on the diatom-bound material in cultured diatoms grown under in situ nutrient conditions, analysis of sediment trap and net tow material, and frustule dissolution experiments will more completely assess this paleoproxy.

Horn, Matthew G.; Robinson, Rebecca S.; Rynearson, Tatiana A.; Sigman, Daniel M.

2011-09-01

86

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

87

Energy Saving Glass Lamination via Selective Radio Frequency Heating  

Microsoft Academic Search

This project focused on advancing radio-frequency (RF) lamination technology closer to commercial implementation, in order to reduce the energy intensity of glass lamination by up to 90%. Lamination comprises a wide range of products including autoglass, architectural safety and innovative design glass, transparent armor (e.g. bullet proof glass), smart glass, mirrors, and encapsulation of photovoltaics. Lamination is also the fastest

Shawn M

2012-01-01

88

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

PubMed Central

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

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

2014-01-01

89

Systematic identification of pathological lamin A interactors  

PubMed Central

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

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

2014-01-01

90

[Chloroplast ultrastructure in some diatoms from different classes].  

PubMed

Diatoms significantly differ from other groups of heterokont algae in the diversity of chloroplast forms, their number, and location in a cell and in the structure of pyrenoids. The information on the fine structure of chloroplast is recognized to be important for taxonomic and phylogenetic studies of diatoms. Six species of diatoms belonging to different classes have been examined using transmission electron microscopy. New data on the structure of chloroplast have been obtained and characteristics of pyrenoid ultrastructure of diatoms belonging to different phylogenetic clades have been specified. The results enlarge the data obtained earlier and specify a set of features of chloroplast ultrastructure for different phylogenetic clades of diatoms. PMID:19505053

Bedoshvili, E D; Popkova, T P; Likhoshva?, E V

2009-01-01

91

A Live Bioprobe for Studying Diatom-Surface Interactions  

PubMed Central

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

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

2004-01-01

92

Thermal stresses in laminated beams  

E-print Network

12. 35 ? 88. 32 29. 69 ? 25. 64 34. 81 25. 32 40. 00 140. 24 159. 49 i 158. 47 139. 26 47. 33 257. 61 92. 23 54. 23 413. 21 41. 26 -11. 8 15. 10 -22. 15, 4 38 ]5 18 -13. 9 38. 10 - 9. 0 -10. 2 46. 71 -16. 7 14 52. 13 10. 14 ? 8 8 63. 00... -18 76. 24 97. 01 121. 95 ?20 i -122. 66 -14. ? 97. 01 -18. 1 76 3] 36. 6 ? 54. 00 26. 3 54. 33 -5. 1 -5. 5 -3. 7 -3. 7 -5 1 -5. 1 -3. .2 Load: Sinusoidal Table 11. Stress Field for a Simply-Supported Laminated Beam Under Mechanical...

Marcano, Victor Manuel

1983-01-01

93

Indentation law for composite laminates  

NASA Technical Reports Server (NTRS)

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

Yang, S. H.

1981-01-01

94

Indentation law for composite laminates  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

95

Oscillator strength of instantaneous diatomic sodium molecules  

NASA Astrophysics Data System (ADS)

We introduce definitely the notion of instantaneous molecules, real or fictitious, in spite of its utilization in certain fields of the supraconductivity, genetics and advanced medical research. Calculation of the oscillator strength of instantaneous sodium diatomic molecules gives [ f mol]Na 2( i)=6,86. This method is transposable at lithium and other Ia elements.

Perny, G.

1991-12-01

96

Floating assembly of diatom Coscinodiscus sp. microshells.  

PubMed

Diatoms have silica frustules with transparent and delicate micro/nano scale structures, two dimensional pore arrays, and large surface areas. Although, the diatom cells of Coscinodiscus sp. live underwater, we found that their valves can float on water and assemble together. Experiments show that the convex shape and the 40 nm sieve pores of the valves allow them to float on water, and that the buoyancy and the micro-range attractive forces cause the valves to assemble together at the highest point of water. As measured by AFM calibrated glass needles fixed in manipulator, the buoyancy force on a single floating valve may reach up to 10 ?N in water. Turning the valves over, enlarging the sieve pores, reducing the surface tension of water, or vacuum pumping may cause the floating valves to sink. After the water has evaporated, the floating valves remained in their assembled state and formed a monolayer film. The bonded diatom monolayer may be valuable in studies on diatom based optical devices, biosensors, solar cells, and batteries, to better use the optical and adsorption properties of frustules. The floating assembly phenomenon can also be used as a self-assembly method for fabricating monolayer of circular plates. PMID:22387476

Wang, Yu; Pan, Junfeng; Cai, Jun; Zhang, Deyuan

2012-03-30

97

Paleointensity-assisted chronology for 0-130 ka from the southern Gardar Drift (North Atlantic)  

Microsoft Academic Search

Piston core KN166-14-JPC13 was collected from the southern Gardar Drift at 3024 m water depth during a cruise of the RV Knorr in the summer of 2002. Sediments from the ~25 meter long piston core comprise silty clays and laminated diatom oozes. The core extends to the base of marine isotope substage (MIS) 5e and has a mean sedimentation rate

H. F. Evans; D. A. Hodell; J. E. Channell

2006-01-01

98

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

99

Method for fabricating laminated uranium composites  

DOEpatents

The present invention is directed to a process for fabricating laminated composites of uranium or uranium alloys and at least one other metal or alloy. The laminated composites are fabricated by forming a casting of the molten uranium with the other metal or alloy which is selectively positioned in the casting and then hot-rolling the casting into a laminated plate in or around which the casting components are metallurgically bonded to one another to form the composite. The process of the present invention provides strong metallurgical bonds between the laminate components primarily since the bond disrupting surface oxides on the uranium or uranium alloy float to the surface of the casting to effectively remove the oxides from the bonding surfaces of the components.

Chapman, L.R.

1983-08-03

100

Manufacturing and mechanical response of nanocomposite laminates  

Microsoft Academic Search

A newly developed methodology is proposed first to manufacture AS-4\\/PEEK APC-2 nano-composite laminates. The improvement of mechanical properties of nano-laminates is verified by a series of testings systematically. The achievement of empirical results is highlighted as follows. From tensile tests it is found that the optimal content of nanoparticles (SiO2) is 1% by total wt. The ultimate strength increases about

Ming-Hwa R. Jen; Yu-Chung Tseng; Chun-Hsien Wu

2005-01-01

101

Smooth indentation of a composite laminate  

NASA Technical Reports Server (NTRS)

Finite difference method is used to analyze the problem of smooth contact between a rigid indenter and a laminated circular plate clamped at the edges. The plate consists of transversely isotropic layers. The interlaminar shear stresses in the contact region are found to be much different from the laminate plate theory solutions. It has been found that low-modulus interlayers cause significant reduction in the maximum interlaminar shear stresses.

Sankar, B. V.

1988-01-01

102

Evaluation of polybenzimidazole glass-fabric laminates  

Microsoft Academic Search

Laminates prepared from polybenzimidazole and 1581-994S glass fabric have excellent short-time heat resistance to 800 deg F., and 100-hr. thermal stability at 600 deg F. These characteristics are based on mechanical-property strength retention and low resin weight loss. In spite of high cost and processing difficulties, polybenzimidazoles are being applied as laminates and adhesives for nose fairing, thermal insulation, aircraft

Mackay

1966-01-01

103

Lamin proteolysis facilitates nuclear events during apoptosis  

PubMed Central

Expression of the adenovirus E1A oncogene stimulates both cell proliferation and p53-dependent apoptosis in rodent cells. p53 implements apoptosis in all or in part through transcriptional activation of bax, the product of which promotes cell death. The adenovirus E1B 19K product is homologous in sequence and in function to Bcl-2, both of which bind to and inhibit the activity of Bax and thereby suppress apoptosis. The E1B 19K protein also interacts with the nuclear lamins, but the role of this interaction in the regulation of apoptosis is not known. Lamins are, however, substrates for members of the interleukin-1 beta-converting enzyme (ICE) family of cysteine proteases that are activated during apoptosis and function downstream of Bcl-2 in the cell death pathway. lamins are degraded during E1A- induced p53-dependent apoptosis. Lamin A and C are cleaved into 47- and 37-kD fragments, respectively, and the site of proteolysis is mapped to a conserved aspartic acid residue at position 230. The cleavage of lamins during apoptosis is consistent with the activation of an ICE- related cysteine protease down-stream of p53. No lamin protease activity was detected in cells expressing the E1B 19K protein, indicating that 19K functions upstream of protease activation in inhibiting apoptosis. Substitution of the aspartic acid at the cleavage site produced a mutant lamin protein that was resistant to proteolysis both in vitro and in vivo. Expression of uncleavable mutant lamin A or B attenuated apoptosis, delaying cell death and the associated DNA fragmentation by 12 h. Mutant lamin expressing cells failed to show the signs of chromatin condensation and nuclear shrinkage typical of cell death by apoptosis. Instead, the nuclear envelope collapsed and the nuclear lamina remained intact. However, the late stage of apoptosis was morphologically unaltered and formation of apoptotic bodies was evident. Thus, lamin breakdown by proteolytic degradation facilitates the nuclear events of apoptosis perhaps by facilitating nuclear breakdown. PMID:8978814

1996-01-01

104

A diatom gene regulating nitric-oxide signaling and susceptibility to diatom-derived aldehydes.  

PubMed

Diatoms are unicellular phytoplankton accounting for approximately 40% of global marine primary productivity [1], yet the molecular mechanisms underlying their ecological success are largely unexplored. We use a functional-genomics approach in the marine diatom Phaeodactylum tricornutum to characterize a novel protein belonging to the widely conserved YqeH subfamily [2] of GTP-binding proteins thought to play a role in ribosome biogenesis [3], sporulation [4], and nitric oxide (NO) generation [5]. Transgenic diatoms overexpressing this gene, designated PtNOA, displayed higher NO production, reduced growth, impaired photosynthetic efficiency, and a reduced ability to adhere to surfaces. A fused YFP-PtNOA protein was plastid localized, distinguishing it from a mitochondria-localized plant ortholog. PtNOA was upregulated in response to the diatom-derived unsaturated aldehyde 2E,4E/Z-decadienal (DD), a molecule previously shown to regulate intercellular signaling, stress surveillance [6], and defense against grazers [7]. Overexpressing cell lines were hypersensitive to sublethal levels of this aldehyde, manifested by altered expression of superoxide dismutase and metacaspases, key components of stress and death pathways [8, 9]. NOA-like sequences were found in diverse oceanic regions, suggesting that a novel NO-based system operates in diatoms and may be widespread in phytoplankton, providing a biological context for NO in the upper ocean [10]. PMID:18538570

Vardi, Assaf; Bidle, Kay D; Kwityn, Clifford; Hirsh, Donald J; Thompson, Stephanie M; Callow, James A; Falkowski, Paul; Bowler, Chris

2008-06-24

105

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.

etin, Arda; Krebs, Jrme; Durussel, Alexandre; Rossoll, Andreas; Inoue, Junya; Koseki, Toshihiko; Nambu, Shoichi; Mortensen, Andreas

2011-11-01

106

Classical Analogs of a Diatomic Chain  

SciTech Connect

Using one dimensional rods with different configurations classical analogs of quantum mechanical systems frequently used in solid state physics can be obtained. Among this analogs we have recently discussed locally periodic rods which lead to band spectra; the effect of a topological defect, and the Wannier Stark ladders. In this paper, we present an elastic analog of the diatomic chain and show how the acoustical and optical bands emerge, as well of the nature of the wave amplitudes.

Gutierrez, L.; Diaz-de-Anda, A.; Mendez-Sanchez, R. A.; Morales, A. [Instituto de Ciencias Fisicas, Universidad Nacional Autonoma de Mexico, A.P. 48-3, 62251, Cuernavaca, Morelos (Mexico); Flores, J.; Monsivais, G. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, A. P. 20-364, 01000, Mexico, D. F. (Mexico)

2010-12-21

107

Silicon diatom frustules as nanostructured photoelectrodes.  

PubMed

In the quest for solutions to meeting future energy demands, solar fuels play an important role. A particularly promising example is photocatalysis since even incremental improvements in performance in this process are bound to translate into significant cost benefits. Here, we report that semiconducting and high surface area 3D silicon replicas prepared from abundantly available diatom fossils sustain photocurrents and enable solar energy conversion. PMID:25061637

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

2014-09-18

108

Semitransparent Organic Photovoltaic Cells with Laminated Top Electrode  

E-print Network

Semitransparent Organic Photovoltaic Cells with Laminated Top Electrode Jung-Yong Lee, Steve T demonstrate semitransparent small molecular weight organic photovoltaic cells using a laminated silver metal cathode due to differences in optical absorption. KEYWORDS Organic photovoltaics, transparent

Cui, Yi

109

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

Federal Register 2010, 2011, 2012, 2013

...Enforcement)] Certain Prepregs, Laminates, and Finished Circuit Boards AGENCY: U.S. International Trade Commission. ACTION...importation of certain prepregs, laminates, and finished circuit boards that infringe certain claims of United States...

2013-04-19

110

Plated lamination structures for integrated magnetic devices  

SciTech Connect

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

Webb, Bucknell C.

2014-06-17

111

Silicone modified resins for graphite fiber laminates  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

112

Thermographic imaging of disbonds in laminated structures  

NASA Technical Reports Server (NTRS)

The presence of disbonds significantly decreases the integrity of many laminated structures used in aerospace applications. Critical for the assessment of the effect of these disbonds on structural integrity is a determination of the disbond area. Thermography is able to detect local variations in temperature after external heating resulting from subsurface delaminations. One limitation of thermography is that the heat diffuses within the laminates, causing difficulty in determining the area of the disbond from the thermographic image. A technique has been developed for reducing the thermographic image to an image of subsurface delaminations for some laminated structures. The technique clearly delineates regions of disbond and is able to resolve disbonds which are unresolvable in the thermographic image. The limits of this technique for resolving the area and separation of disbonds are investigated using both experimental measurements and numerical calculations.

Winfree, William P.; Cramer, Elliot; Howell, P. A.

1990-01-01

113

Stochastic damage evolution in textile laminates  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

114

Diatom community structure on in-service cruise ship hulls.  

PubMed

Diatoms are an important component of marine biofilms found on ship hulls. However, there are only a few published studies that describe the presence and abundance of diatoms on ships, and none that relate to modern ship hull coatings. This study investigated the diatom community structure on two in-service cruise ships with the same cruise cycles, one coated with an antifouling (AF) system (copper self-polishing copolymer) and the other coated with a silicone fouling-release (FR) system. Biofilm samples were collected during dry docking from representative areas of the ship and these provided information on the horizontal and vertical zonation of the hull, and intact and damaged coating and niche areas. Diatoms from the genera Achnanthes, Amphora and Navicula were the most common, regardless of horizontal ship zonation and coating type. Other genera were abundant, but their presence was more dependent on the ship zonation and coating type. Samples collected from damaged areas of the hull coating had a similar community composition to undamaged areas, but with higher diatom abundance. Diatom fouling on the niche areas differed from that of the surrounding ship hull and paralleled previous studies that investigated differences in diatom community structure on static and dynamically exposed coatings; niche areas were similar to static immersion and the hull to dynamic immersion. Additionally, diatom richness was greater on the ship with the FR coating, including the identification of several new genera to the biofouling literature, viz. Lampriscus and Thalassiophysa. These results are the first to describe diatom community composition on in-service ship hulls coated with a FR system. This class of coatings appears to have a larger diatom community compared to copper-based AF systems, with new diatom genera that have the ability to stick to ship hulls and withstand hydrodynamic forces, thus creating the potential for new problematic species in the biofilm. PMID:25377486

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

2014-10-01

115

Stiffness and thermoelastic coefficients for composite laminates  

NASA Technical Reports Server (NTRS)

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

Noor, Ahmed K.; Tenek, Lazarus H.

1992-01-01

116

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

117

Fatigue of Wind Blade Laminates:Fatigue of Wind Blade Laminates: Effects of Resin and Fabric Structure  

E-print Network

Fatigue of Wind Blade Laminates:Fatigue of Wind Blade Laminates: Effects of Resin and Fabric University MCARE 2012 #12;Outline · Overview of MSU Fatigue Program on Wind Blade MaterialsWind Blade for Infused Laminates · Comparison of Fatigue Trends for Various· Comparison of Fatigue Trends for Various

118

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

119

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

120

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

121

The Central Carbon and Energy Metabolism of Marine Diatoms  

PubMed Central

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

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

2013-01-01

122

Benthic diatoms in lakes: environmental drivers and ecological  

E-print Network

Benthic diatoms in lakes: environmental drivers and ecological assessment Steffi Gottschalk Faculty #12;Benthic diatoms in lakes: environmental drivers and ecological assessment Abstract In order are frequently used for assessing ecological status in streams and for reconstructing water quality of lakes

123

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...

124

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

125

The diatom flora of the Salton Sea, California  

Microsoft Academic Search

We report on diatom species of the Salton Sea, a highly saline (43 g l-1) inland lake in California. We identified and photographed all diatom taxa encountered in the phytoplankton and benthos of the Salton Sea and its immediate tributaries. Ninety-four taxa were distinguished based on their morphological features using light- and electron microscopy. In the Salton Sea, there are

Carina B. Lange; Mary Ann Tiffany

2002-01-01

126

Continental diatoms as indicators of long-term environmental change  

USGS Publications Warehouse

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

Bradbury, J. Platt

1999-01-01

127

Spectroscopic Studies of Diatomic Indium Halides  

NASA Astrophysics Data System (ADS)

A critical review of the available spectroscopic information about diatomic indium halides has been performed. The literature was surveyed till early 2002 and the data on the molecular constants for the ground state, as well as excited states of these molecules has been presented. A brief discussion on the dissociation energies, ionization potentials, and the nature of the bonding in the ground state is given. The energy level diagram and Rydberg-Klein-Rees potential curves for the different electronic states of these molecules are also presented. Mechanism of laser emission/fluorescence due to atomic indium in the ultraviolet photodissociation of indium monohalides has also been discussed.

Mishra, S. K.; Yadav, Raj K. S.; Singh, V. B.; Rai, S. B.

2004-06-01

128

Applications of Diatoms as Potential Microalgae in Nanobiotechnology  

PubMed Central

Introduction Diatoms are single cell eukaryotic microalgae, which present in nearly every water habitat make them ideal tools for a wide range of applications such as oil explora-tion, forensic examination, environmental indication, biosilica pattern generation, toxicity testing and eutrophication of aqueous ecosystems. Methods Essential information on diatoms were reviewed and discussed towards impacts of diatoms on biosynthesis and bioremediation. Results In this review, we present the recent progress in this century on the application of diatoms in waste degradation, synthesis of biomaterial, biomineraliza-tion, toxicity and toxic effects of mineral elements evaluations. Conclusion Diatoms can be considered as metal toxicity bioindicators and they can be applied for biomineralization, synthesis of biomaterials, and degradation of wastes. PMID:23678445

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

2012-01-01

129

Prediction of Composite Laminate Fracture: Micromechanics and Progressive Fracture  

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

130

HYGROTHERMAL AGING OF POLYIMIDE MATRIX COMPOSITE LAMINATES  

E-print Network

HYGROTHERMAL AGING OF POLYIMIDE MATRIX COMPOSITE LAMINATES John A. Nairn and Man-Hee Han Materials-0560, USA SUMMARY: Two polyimide-matrix systems were subjected to a series of hygrothermal aging experiments at various temperatures and relative humidities. For each aging condition, we measured the microcracking

Nairn, John A.

131

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

132

Theory of laminated turbulence: open questions  

E-print Network

Theory of laminated turbulnece includes continuous layer of turbulence (statistical description, kinetic equations, Zakharov-Kolmogorov spectra, etc) AND discrete layer of turbulence (isolated groups of interacting waves, no statisticaldescription). This theory is presented, examples of possible applications are given, important open questions are formulated.

E. Kartashova

2006-07-30

133

Probabilistic sizing of laminates with uncertainties  

NASA Technical Reports Server (NTRS)

A reliability based design methodology for laminate sizing and configuration for a special case of composite structures is described. The methodology combines probabilistic composite mechanics with probabilistic structural analysis. The uncertainties of constituent materials (fiber and matrix) to predict macroscopic behavior are simulated using probabilistic theory. Uncertainties in the degradation of composite material properties are included in this design methodology. A multi-factor interaction equation is used to evaluate load and environment dependent degradation of the composite material properties at the micromechanics level. The methodology is integrated into a computer code IPACS (Integrated Probabilistic Assessment of Composite Structures). Versatility of this design approach is demonstrated by performing a multi-level probabilistic analysis to size the laminates for design structural reliability of random type structures. The results show that laminate configurations can be selected to improve the structural reliability from three failures in 1000, to no failures in one million. Results also show that the laminates with the highest reliability are the least sensitive to the loading conditions.

Shah, A. R.; Liaw, D. G.; Chamis, C. C.

1993-01-01

134

Doped LZO buffer layers for laminated conductors  

DOEpatents

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

2010-03-23

135

DELAMINATION ANALYSIS OF CARBON FIBRE REINFORCED LAMINATES  

Microsoft Academic Search

Drilling of carbon\\/epoxy laminates is normally carried out using standard drills, like twist or Brad drills. However, it is necessary to bear in mind the need to adapt the processes and\\/or tooling as the risk of delamination, or other damages, is high. These problems can affect the mechanical properties of the produced parts, hence, lower reliability. Production of higher quality

Antnio T. Marques; Lus M. Duro; Antnio G. Magalhes; Joo M. Tavares

136

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

NASA Astrophysics Data System (ADS)

The giant diatom Ethmodiscus was examined along an east-west transect at 28-30N 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=50.83.7 and 3.70.8 nmol N and P cell -1) and yielded N:P ratios that closely clustered around the Redfield ratio (average=14.61.1). 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=0.730.04 for 2003, and 0.690.05 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

137

Compression failure of angle-ply laminates  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

138

The effect of bacteria on diatom community structure the antibiotics approach  

Microsoft Academic Search

To investigate the effect of bacteria on diatoms at the community level, sediment samples from an intertidal tropical environment were treated with penicillin (a ?-lactam antibiotic that can affect diatoms only through bacteria). Streptomycin (an aminoglycoside) and chloramphenicol, antibiotics that can potentially affect protein synthesis in diatom organelles and photosynthesis, were also used for comparison. The changes in diatom community

Priya M. DCosta; Arga Chandrashekar Anil

2011-01-01

139

Diatoms from surface sediments of the northern part of Lake Tanganyika  

Microsoft Academic Search

227 Diatom taxa were observed in the surface sediments of the northern part of Lake Tanganyika, including 1 new to science: Amphora tanganyikae. The diatom community of these sediments is mainly composed of benthic organisms while planktonic diatoms are rather rare. Many brackish-water and a few marine organisms were observed. Cosmopolitan organisms (77.1%) dominate the diatom flora but tropical, tropical

A. G. Caljon; C. Z. Cocquyt

1992-01-01

140

Diatom assemblages promote ice formation in large lakes.  

PubMed

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

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

2013-08-01

141

Diatom-based label-free optical biosensor for biomolecules.  

PubMed

Diatoms are unicellular algae, which fabricates ornate biosilica shells called frustules that possess a surface rich in reactive silanol (Si-OH) groups. The intrinsic patterned porous structure of diatom frustules at nanoscale can be exploited in the effective detection of biomolecules. In this study, the frustules of a specific diatom Amphora sp. has been functionalized to detect bovine serum albumin (BSA). The functionalization of the diatom frustule substrate is achieved by using 3-aminopropyltriethoxysilane (APES). The field emission scanning electron microscopy (FESEM) results showed an ornately patterned surface of the frustule valve ordered at nanoscale. The Fourier transform infrared (FTIR) spectra confirmed the N-H bending and stretching of the amine group after amine functionalization. The emission peaks in the photoluminescence (PL) spectra of the amine-functionalized diatom biosilica selectively enhanced the intensity by a factor of ten when compared to that of a bare diatom biosilica. The result showed a significant quenching of PL intensity of BSA at around 445nm due to the interaction of amine-functionalized diatom-BSA protein complex. The detection limit was found to be 3??10(-5)M of BSA protein. Hence, the study proves that the functionalized frustule of Amphora sp. is an effective quantitative analytical tool for optical label-free biosensing applications. PMID:24989453

Viji, S; Anbazhagi, M; Ponpandian, N; Mangalaraj, D; Jeyanthi, S; Santhanam, P; Devi, A Shenbaga; Viswanathan, C

2014-10-01

142

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. PMID:23056617

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

2012-01-01

143

Diatom assemblages promote ice formation in large lakes  

PubMed Central

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

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

2013-01-01

144

Modeling diatomic potential energy curves through the generalized exponential function  

NASA Astrophysics Data System (ADS)

In the present work, an alternative family of analytical potential energy curves (PECs) has been developed for diatomic systems. These kinds of functions, that are based on q-exponential, are used here to generalize the usual Bond Order (BO) and Rydberg analytical PECs of diatomic molecular systems. The diatomic systems H2+ and Li 2 have been examined by means of this alternative approach. In particular, the computed vibrational spectra and spectroscopic constants were found to be in good agreement with the available experimental data.

Esteves, C. S.; de Oliveira, H. C. B.; Ribeiro, L.; Gargano, R.; Mundim, K. C.

2006-08-01

145

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

146

Relationships between dipole moments of diatomic molecules.  

PubMed

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

Hou, Shilin; Bernath, Peter F

2015-01-28

147

Magnetoelectric nonlinearity in magnetoelectric laminate sensors  

NASA Astrophysics Data System (ADS)

A nonlinearity in the magnetoelectric coefficient, ?MENonlin, of Metglas/Pb(Zr,Ti)O3 (PZT) and Metglas/Pb(Mg1/3,Nb2/3)O3-PbTiO3 (PMN-PT) laminate sensors has been observed. This nonlinearity was found to be dependent on the dc magnetic bias (Hdc) and frequency of the ac drive field (Hac). The maximum value of ?MENonlin for both types of composites was found near the electromechanical resonance. For Metglas/PZT laminates, the maximum occurred under a finite bias of Hdc ?5 Oe; whereas, for Metglas/PMN-PT, the maximum was found near zero dc bias. One application for ?MENonlin is a cross-modulation scheme that can shift low frequency signals to higher frequency to achieve lower noise floor. For Metglas/PMN-PT, ?MENonlin has another application: removal of the necessity of a dc bias, which helps to design high-sensitivity sensor arrays and gradiometers.

Shen, Liangguo; Li, Menghui; Gao, Junqi; Shen, Ying; Li, J. F.; Viehland, D.; Zhuang, X.; Lam Chok Sing, M.; Cordier, C.; Saez, S.; Dolabdjian, C.

2011-12-01

148

Investigating Delamination Migration in Composite Tape Laminates  

NASA Technical Reports Server (NTRS)

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

Ratcliffe, James G.; DeCarvalho, Nelson V.

2014-01-01

149

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.

Mller, Daniel W.; Schrader, Hans

1989-02-01

150

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

NASA Astrophysics Data System (ADS)

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

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

2009-01-01

151

Process Yields Strong, Void-Free Laminates  

NASA Technical Reports Server (NTRS)

Need for lightweight materials as structural components for future space transportation systems stimulated development of systematic method for manufacturing a polyimide/graphite composite. Laminates manufactured by process are void-free, exhibit excellent thermo-oxidative stability up to 315 degrees C (600 degrees F) and are 40 percent lighter than aluminum. Process is precise, repeatable, and ideally suited for researchers and small-lot producers of composite materials.

Bryant, L. E.; Covington, E. W., III; Dale, W. J.; Hall, E. T., Jr; Justice, J. E.; Taylor, E. C.; Wilson, M. L.

1983-01-01

152

Optimal design of laminated composite beam structures  

Microsoft Academic Search

This work deals with design sensitivity analysis and optimal design of composite structures modelled as thin-walled beams.\\u000a The structures are treated as a torsion-bending resistant beams. The analysis problem is discretized by a finite element technique.\\u000a A two-node Hermitean beam element is used. The beam sections are made from an assembly of elements that correspond to flat\\u000a layered laminated composite

J. B. Cardoso; L. G. Sousa; J. A. Castro; A. J. Valido

2002-01-01

153

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

154

Modeling Composite Laminate Crushing for Crash Analysis  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

155

Improved damage tolerance of titanium by adhesive lamination  

NASA Technical Reports Server (NTRS)

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

Johnson, W. S.

1982-01-01

156

Tailored metal matrix laminates for high-temperature performance  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

157

Genomic footprints of a cryptic plastid endosymbiosis in diatoms.  

PubMed

Diatoms and other chromalveolates are among the dominant phytoplankters in the world's oceans. Endosymbiosis was essential to the success of chromalveolates, and it appears that the ancestral plastid in this group had a red algal origin via an ancient secondary endosymbiosis. However, recent analyses have turned up a handful of nuclear genes in chromalveolates that are of green algal derivation. Using a genome-wide approach to estimate the "green" contribution to diatoms, we identified >1700 green gene transfers, constituting 16% of the diatom nuclear coding potential. These genes were probably introduced into diatoms and other chromalveolates from a cryptic endosymbiont related to prasinophyte-like green algae. Chromalveolates appear to have recruited genes from the two major existing algal groups to forge a highly successful, species-rich protist lineage. PMID:19556510

Moustafa, Ahmed; Beszteri, Bnk; Maier, Uwe G; Bowler, Chris; Valentin, Klaus; Bhattacharya, Debashish

2009-06-26

158

No microzooplankton grazing during a Mediopyxis helysia dominated diatom bloom  

NASA Astrophysics Data System (ADS)

The new diatom species Mediopyxis helysia was described to science from clones found in 2003 in the North Sea, northern Wadden Sea, and the Gulf of Maine. Seven years after its first occurrence, we observed Mediopyxis to contribute up to almost 50% of the biovolume of the diatoms during a diatom spring bloom in the western Wadden Sea. Grazing experiments based on the dilution technique could not detect any microzooplankton grazing impact on the bloom community. Mediopyxis is now also well established in the western Wadden Sea and does have the potential to become a dominant species. The reasons for its success remain largely unresolved but avoidance of being grazed might be one factor. Future research on this new species is needed to understand the success and forecast the ecological footprint of this large diatom species arriving in the western European Seas.

Loebl, Martina; van Beusekom, Justus E. E.; Philippart, Catharina J. M.

2013-09-01

159

A Simplified Quantum Mechanical Model of Diatomic Molecules  

ERIC Educational Resources Information Center

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

Nielsen, Lars Drud

1978-01-01

160

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

161

Rolling of ARALL laminates (an alternative method for post-stretching ARALL laminates)  

NASA Astrophysics Data System (ADS)

A rolling process is presented as an alternative to post stretching aramide reinforced aluminum laminates (ARALL) in order to set fibers under tension and the aluminum layers under compression. It is found that the reversion of the thermal residual stress system in ARALL laminates can easily be achieved by rolling the material to a permanent setting (for instance 0.4 percent). The fatigue properties of the material are as good as the post-stretched version and some of the mechanical properties show significant improvement without losing any advantage. The main advantage of this process is that conventional rolling equipment can be used which means lower costs and higher productivity for the materials manufacturer. The process may be used to treat wide panels which is essential if the ARALL laminates are to be used as aircraft fuselage skin materials. Test results are presented.

Chen, D.; Smulders, F. E. H. M.; Vogelesang, L. B.

1988-07-01

162

Mechanical behavior of lightweight thermoplastic fibermetal laminates  

Microsoft Academic Search

Lightweight thermoplastic-based fibermetal laminates were developed based on self-reinforced polypropylene and glass fiber-reinforced polypropylene composite materials and an aluminum alloy 2024-T3. The laminates were manufactured using a fast one-step cold press manufacturing procedure. The mechanical behavior of the laminates was then investigated under tensile and fatigue loading conditions. The tensile properties of the plain aluminum, the composite materials and the

G. Reyes; H. Kang

2007-01-01

163

Antibacterial performance of colloidal silver-treated laminate wood flooring  

Microsoft Academic Search

In this study both the anti-bacterial properties and strength of cockroach avoidance of laminate wood floorings containing colloidal silver is evaluated. The laminate wood flooring manufactured with the overlay added with resin containing colloidal silver ion showed an antibacterial activity of up to 98.9%. For colloidal silver-treated, laminate wood flooring, the relative avoidance rate was 871%. With colloidal silver treatment

Sumin Kim; Hyun-Joong Kim

2006-01-01

164

Energy Saving Glass Lamination via Selective Radio-Frequency Heating  

SciTech Connect

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

Shulman, Holly S.; Allan, Shawn M.

2009-11-11

165

Seasonal Climate Dynamics Inferred From High Resolution Modern Diatom Data  

NASA Astrophysics Data System (ADS)

keywords: seasonal, sediment-traps, diatoms, lakes To understand and predict future climatic changes, we study past climate dynamics, using subfossil diatoms deposited in lake sediments. A training set consisting of surface lake sediments integrating diatom assemblages over recent years is the classical approach to reconstruct past environmental conditions in palaeolimnological research. However, not only annual temperatures and average limnological conditions are relevant but also seasonal thermal and limnological variability, as evidenced by spring and autumn diatom blooms. As high temporal resolution plays an important role in understanding the diatom ecology and its use in palaeolimnological reconstructions, we investigated diatom succession and seasonal limnological variability on a bi-weekly basis using sediment traps. In order to better understand the impact of climate on the seasonality of diatoms we studied 6 lakes distributed over an altitudinal gradient from 330 to 950 m a.s.l., in the Laurentides Provincial Park region north of Quebec-City, Canada. Multivariate statistics was applied to explore the main biological and limnological patterns in the modern data, revealing that the climatic gradient explained most of the biological variance. One advantage of sediment traps is that, compared to surface sediment samples, the time of deposition is exactly known, thus changes in environmental variables can be better related to shifts in the biological assemblages. From one of the study lakes, at 830 m altitude, a sediment core was taken. Fossil diatoms of the past 9500 years were analysed at high resolution (about 15 years/sample) and modern seasonal diatom distribution was used to interpret changes in fossil diatom assemblages. From ca. 9.5 until ca. 8 ka cal. BP, spring bloom species that are presently found in the low altitude lakes occurred with ca. 30%, whereas an autumn bloom species typical of autumnal diatom communities in the highest elevation lake occurred with 50%. In the more recent sediments of the core, autumn bloom taxa typical of the lowest altitude lakes increased upcore to 20%. These patterns could be related to a cooling of spring temperatures and warming of autumn temperatures during the Holocene, which are in agreement with changes in spring and autumn solar insolation patterns of the Milankovitch orbital cycles. Contrary to the surface sediment sample technique, our novel approach using sediment traps with high temporal resolution of modern data may allow inferences about past seasonal climate dynamics.

Hausmann, S.; Pientiz, R.

2004-12-01

166

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

167

Diatom frustule photonic crystal geometric and optical characterization  

NASA Astrophysics Data System (ADS)

Diatom algae are single-celled, photosynthetic organisms with a cell wall called a frustulea periodically patterned nano-structure made of silica. Throughout the last decade, diatom frustules have been studied for their potential uses as photonic crystals and biomimetic templates for artificially developed metamaterials. A MATLAB program characterizing their pore structure as a function of angle was developed, potentially giving insight into how their geometric characteristics determine their optical properties.

Mishler, Jonathan; Blake, Phillip; Alverson, Andrew J.; Roper, D. K.; Herzog, Joseph B.

2014-08-01

168

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

169

Colocalization of intranuclear lamin foci with RNA splicing factors.  

PubMed

The lamins form a fibrous network underlying the inner nuclear membrane termed the nuclear lamina. In order to gain insights into the role of lamins in nuclear organization, we have characterized a monoclonal antibody (LA-2H10) raised against recombinant rat lamin A that labels nuclei in a speckled pattern in all cells of unsynchronized populations of HeLa and rat F-111 fibroblast cells, unlike the typical nuclear periphery staining by another monoclonal antibody to lamin A, LA-2B3. In immunolocalization studies the lamin A speckles or foci were found to colocalize with the RNA splicing factors SC-35 and U5-116 kD, but not with p80 coilin found in coiled bodies. Lamin B1 was also associated with these foci. These foci dispersed when cells entered mitosis and reformed during anaphase. The differential reactivity of LA-2H10 and LA-2B3 was retained after nuclei were extracted with detergents, nucleases and salt to disrupt interactions of lamins with chromatin and other nuclear proteins. Using deletion fragments of recombinant lamin A, the epitope recognized by LA-2H10 was located between amino acids 171 and 246. Our findings are consistent with a structural role for lamins in supporting nuclear compartments containing proteins involved in RNA splicing. PMID:10574713

Jagatheesan, G; Thanumalayan, S; Muralikrishna, B; Rangaraj, N; Karande, A A; Parnaik, V K

1999-12-01

170

Sound transmission into a laminated composite cylindrical shell  

NASA Technical Reports Server (NTRS)

In the context of the transmission of airborne noise into an aircraft fuselage, a mathematical model is presented for the transmission of an oblique plane sound wave into a laminated composite circular cylindrical shell. Numerical results are obtained for geometry typical of a narrow-bodied jet transport. Results indicate that from the viewpoint of noise attenuation on laminated composite shell does not appear to offer any significant advantage over an aluminum shell. However, the transmission loss of a laminated composite shell is sensitive to the orientation of the fibers and this suggests the possibility of using a laminated composite shell to tailor the noise attenuation characteristics to meet a specific need.

Koval, L. R.

1980-01-01

171

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

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

2013-01-01

172

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, Loc; de Vargas, Colomban; Pawlowski, Jan

2011-07-01

173

Growth form defines physiological photoprotective capacity in intertidal benthic diatoms.  

PubMed

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

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

2015-01-01

174

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

175

Regularities in molecular properties of ground state stable diatomics  

NASA Astrophysics Data System (ADS)

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.

Zavitsas, Andreas A.

2004-06-01

176

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

177

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

178

Seasonal changes of diatom species in the Hooghly estuary, India  

NASA Astrophysics Data System (ADS)

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

Goswami, P. K.

2013-12-01

179

Cenozoic Planktonic Marine Diatom Diversity and Correlation to Climate Change  

PubMed Central

Marine planktonic diatoms export carbon to the deep ocean, playing a key role in the global carbon cycle. Although commonly thought to have diversified over the Cenozoic as global oceans cooled, only two conflicting quantitative reconstructions exist, both from the Neptune deep-sea microfossil occurrences database. Total diversity shows Cenozoic increase but is sample size biased; conventional subsampling shows little net change. We calculate diversity from a separately compiled new diatom species range catalog, and recalculate Neptune subsampled-in-bin diversity using new methods to correct for increasing Cenozoic geographic endemism and decreasing Cenozoic evenness. We find coherent, substantial Cenozoic diversification in both datasets. Many living cold water species, including species important for export productivity, originate only in the latest Miocene or younger. We make a first quantitative comparison of diatom diversity to the global Cenozoic benthic ?18O (climate) and carbon cycle records (?13C, and 20-0 Ma pCO2). Warmer climates are strongly correlated with lower diatom diversity (raw: rho?=?.92, p<.001; detrended, r?=?.6, p?=?.01). Diatoms were 20% less diverse in the early late Miocene, when temperatures and pCO2 were only moderately higher than today. Diversity is strongly correlated to both ?13C and pCO2 over the last 15 my (for both: r>.9, detrended r>.6, all p<.001), but only weakly over the earlier Cenozoic, suggesting increasingly strong linkage of diatom and climate evolution in the Neogene. Our results suggest that many living marine planktonic diatom species may be at risk of extinction in future warm oceans, with an unknown but potentially substantial negative impact on the ocean biologic pump and oceanic carbon sequestration. We cannot however extrapolate our my-scale correlations with generic climate proxies to anthropogenic time-scales of warming without additional species-specific information on proximate ecologic controls. PMID:24465441

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

2014-01-01

180

Direct laser cooling of a diatomic molecule  

NASA Astrophysics Data System (ADS)

We have experimentally observed transverse laser cooling of the polar, diatomic molecule strontium monofluoride (SrF) using the X^2&+circ; ^2?1/2 optical cycling scheme previously demonstrated [1]. In general molecules are not amenable to direct laser cooling because their vibrational and rotational degrees of freedom typically lead to high branching probabilities into a large number of unwanted sublevels. Our scheme takes advantage of SrF's highly diagonal Franck-Condon factors which suppress vibrational branching. We eliminate rotational branching by employing a quasi-cycling N ^' type transition in conjunction with magnetic field remixing of dark Zeeman sublevels. One complication of this scheme is that the large number of X^2 &+circ; ground levels in this system leads to a photon scattering rate which is a factor of 3.5 smaller than that of a comparable two-level system. The reduced scattering rate requires that the cooling region be significantly longer than that typically used in atomic systems. [4pt] [1] E. S. Shuman, J. F. Barry, D. R. Glenn, and D. P. DeMille, Phys. Rev. Lett. 103, 223001 (2009).

Shuman, Edward; Barry, John; Demille, Dave

2010-03-01

181

Vibrational nonequilibrium effects on diatomic dissociation rates  

NASA Technical Reports Server (NTRS)

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

Hansen, C. F.

1993-01-01

182

Laminated anisotropic reinforced plastic plates and shells  

NASA Technical Reports Server (NTRS)

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

Korolev, V. I.

1981-01-01

183

Micromechanics of composite laminate compression failures  

NASA Technical Reports Server (NTRS)

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

Guynn, E. Gail; Bradley, Walter L.

1988-01-01

184

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.

2010-04-01

185

Laminated rare earth structure and method of making  

Microsoft Academic Search

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

David J. Senor; Roger N. Johnson; Bruce D. Reid; Love Jr. Edward F; Sandra Larson; Andrew W. Prichard

2002-01-01

186

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

187

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

188

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

189

A Development of Laminating Mulberry Paper by Biodegradable Films  

Microsoft Academic Search

Currently, the light has shed on the ecological-friendly products. The mulberry products, especially hand-made paper, are wildly facilitated as general wares or decoration. The research on the lamination of the mulberry paper with biodegradable films can ameliorate the usability, corresponding to the modernisation and green products. Meticulously, the laminating machine is designed and created in this research, with the size

Anin Memon; Somsak Ithisoponakul; Supaeak Pramoonmak; Montip lawsuriyonta; Dhanon Leenoi; Nateechai Passadee

2011-01-01

190

Prediction of Multilayer Printed Wiring Board Temperatures During Lamination  

Microsoft Academic Search

Measurements of temperature histories of epoxy\\/glass prepreg layers during multilayer printed wiring board lamination have been recently obtained. It is shown that the temperature histories may be predicted by an analysis of the transient heat flow process within the multilayer board (MLB). The analysis requires a knowledge of the press platen temperature history during laminations and the thermal resistance of

Win Aung

1975-01-01

191

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. Milaien?; V. Jankauskait?; R. Arciauskait?

192

Atomic Layer Deposited Aluminum Oxide \\/ Tantalum Oxide Laminate Films  

Microsoft Academic Search

Nanolaminates offer the possibility of tuning the electrical properties of a dielectric film for specific applications. The use of multiple materials can influence the electrical properties of a film stack and spatial confinement, due to the laminate structure, can affect the crystallization. The conformal, self limiting nature of atomic layer deposition (ALD) makes it ideal for producing thin laminates. ALD

Sean W. Smith; John F. Conley Jr.

2010-01-01

193

Self-heating forecasting for thick laminate specimens in fatigue  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

194

A theory for predicting composite laminate warpage resulting from fabrication  

NASA Technical Reports Server (NTRS)

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 macrohyphenmechanics are used with laminate theory to assess the contribution of factors such as ply misorientation, fiber migration, and fiber and/or void volume ratio nonuniformity on the laminate warpage. Using these equations, it was found that a 1 deg error in the orientation angle of one ply was sufficient to produce warpage end deflection equal to two laminate thicknesses in a 10 inch by 10 inch laminate made from 8 ply Mod-I/epoxy. Using a sensitivity analysis on the governing parameters, it was found that a 3 deg fiber migration or a void volume ratio of three percent in some plies is sufficient to produce laminate warpage corner deflection equal to several laminate thicknesses. Tabular and graphical data are presented which can be used to identify possible errors contributing to laminate warpage and/or to obtain an a priori assessment when unavoidable errors during fabrication are anticipated.

Chamis, C. C.

1974-01-01

195

Composite laminate tailoring with probabilistic constraints and loads  

NASA Technical Reports Server (NTRS)

A reliability-based structural synthesis procedure was developed to tailor laminates to meet reliability-based (ply) strength requirements and achieve desirable laminate responses. The main thrust is to demonstrate how to integrate the optimization technique in the composite laminate tailoring process to meet reliability design requirements. The question of reliability arises in fiber composite analysis and design because of the inherent scatter that is observed in the constituent (fiber and matrix) material properties during experimentation. Symmetric and asymmetric composite laminates subject to mechanical loadings are considered as application examples. These application examples illustrate the effectiveness and ease with which reliability considerations can be integrated in the design optimization model for composite laminate tailoring.

Thanedar, P. B.; Chamis, C. C.

1990-01-01

196

Buckling analysis of laminated thin shells in a hot environment  

NASA Technical Reports Server (NTRS)

Results are presented of parametric studies to assess the effects of various parameters on the buckling behavior of angle-ply, laminated thin shells in a hot environment. These results were obtained by using a three-dimensional finite element analysis. An angle-ply, laminated thin shell with fiber orientation of (theta/-theta)(sub 2) was subjected to compressive mechanical loads. The laminated thin shell had a cylindrical geometry. The laminate contained T300 graphite fibers embedded in an intermediate-modulus, high-strength (IMHS) matrix. The fiber volume fraction was 55 percent and the moisture content was 2 percent. The residual stresses induced into the laminate structure during the curing were taken into account. Parametric studies were performed to examine the effect on the critical buckling load of the following parameters: cylinder length and thickness, internal hydrostatic pressure, different ply thicknesses, different temperature profiles through the thickness of the structure, and different lay up configurations and fiber volume fractions. In conjunction with these parameters the ply orientation was varied from 0 deg to 90 deg. Seven ply angles were examined: 0 deg, 15 deg, 30 deg, 45 deg, 60 deg, 75 deg, and 90 deg. The results show that the ply angle theta and the laminate thickness had significant effects on the critical buckling load. The fiber volume fraction, the fiber orientations, and the internal hydrostatic pressure had important effects on the critical buckling load. The cylinder length had a moderate influence on the buckling load. The thin shell with (theta/-theta)(sub 2) or (theta/-theta)(sub s) angle-ply laminate had better buckling-load performance than the thin shell with (theta)(sub 4) angle-ply laminate. The temperature profiles through the laminate thickness and various laminates with the different ply thicknesses has insignificant effects on the buckling behavior of the thin shells.

Gotsis, Pascal K.; Guptil, James D.

1993-01-01

197

Grasslands, silicate weathering and diatoms: Cause and effect  

SciTech Connect

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

Johansson, A.K. (Columbia Univ., Palisades, NY (United States). Dept. of Geological Sciences)

1993-03-01

198

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. PMID:21321195

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

2011-01-01

199

Lamins as mediators of oxidative stress  

SciTech Connect

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

Sieprath, Tom; Darwiche, Rabih [Cell Systems and Cellular Imaging Group, Department of Molecular Biotechnology, Ghent University, Ghent (Belgium)] [Cell Systems and Cellular Imaging Group, Department of Molecular Biotechnology, Ghent University, Ghent (Belgium); De Vos, Winnok H., E-mail: Winnok.DeVos@UGent.be [Cell Systems and Cellular Imaging Group, Department of Molecular Biotechnology, Ghent University, Ghent (Belgium); NB-Photonics, Ghent University, Ghent (Belgium)

2012-05-18

200

Geometrically nonlinear behavior of piezoelectric laminated plates  

NASA Astrophysics Data System (ADS)

The geometrically nonlinear behavior of piezo-laminated plates actuated with isotropic or anisotropic piezoelectric layers is analytically investigated. The analytical model is derived using the variational principle of virtual work along with the lamination and plate theories, the von Karman large displacement and moderate rotation kinematic relations, and the anisotropic piezoelectric constitutive laws. A solution strategy that combines the approach of the method of lines, the advantages of the finite element concept, and the variational formulation is developed. This approach yields a set of nonlinear ordinary differential equations with nonlinear boundary conditions, which are solved using the multiple-shooting method. Convergence and verification of the model are examined through comparison with linear and nonlinear results of other approximation methods. The nonlinear response of two active plate structures is investigated numerically. The first plate is actuated in bending using monolithic piezoceramic layers and the second one is actuated in twist using macro-fiber composites. The results quantitatively reveal the complicated in-plane stress state associated with the piezoelectric actuation and the geometrically nonlinear coupling of the in-plane and out-of-plane responses of the plate. The influence of the nonlinear effects ranges from significant stiffening in certain combinations of electrical loads and boundary conditions to amplifications of the induced deflections in others. The paper closes with a summary and conclusions.

Rabinovitch, Oded

2005-08-01

201

Influence of cobalamin scarcity on diatom molecular physiology and identification of a cobalamin acquisition protein  

E-print Network

Diatoms are responsible for ?40% of marine primary production and are key players in global carbon cycling. There is mounting evidence that diatom growth is influenced by cobalamin (vitamin B12) availability. This ...

Bertrand, Erin Marie

202

H2SOLV: Fortran solver for diatomic molecules in explicitly correlated exponential basis  

E-print Network

H2SOLV: Fortran solver for diatomic molecules in explicitly correlated exponential basis K; hydrogen molecule PROGRAM SUMMARY Manuscript Title: H2SOLV: Fortran code for diatomic molecules Journal Reference: Catalogue identifier: Licensing provisions: None. Programming language: Fortran 90

Pachucki, Krzysztof

203

Diatom communities as ecological indicators of recovery in restored prairie wetlands  

Microsoft Academic Search

Diatoms were employed to assess the recovery of northern prairie wetlands restored after drainage. We predicted that diatom\\u000a species diversity and equitability are lower in restored wetlands than in reference wetlands and that diatom communities are\\u000a similar among reference wetlands because communities should be relatively stable over time. Conversely, we predicted that\\u000a diatom communities in restored and reference wetlands differ

Paul M. Mayer; Susan M. Galatowitsch

1999-01-01

204

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, Lela; Bowler, Chris

2012-02-01

205

Long-term decomposition of DOC from experimental diatom blooms  

SciTech Connect

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

Fry, B.; Hopkinson, C.S. Jr.; Nolin, A. [Ecosystems Center, Woods Hole, MA (United States)

1996-09-01

206

Circular random motion in diatom gliding under isotropic conditions  

NASA Astrophysics Data System (ADS)

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

Gutirrez-Medina, Braulio; Jimnez Guerra, Andrs; Pea Maldonado, Ana Iris; Covarrubias Rubio, Yadiralia; Viridiana Garca Meza, Jessica

2014-12-01

207

The coupled states approximation for scattering of two diatoms  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

208

Circular random motion in diatom gliding under isotropic conditions.  

PubMed

How cells migrate has been investigated primarily for the case of trajectories composed by joined straight segments. In contrast, little is known when cellular motion follows intrinsically curved paths. Here, we use time-lapse optical microscopy and automated trajectory tracking to investigate how individual cells of the diatom Nitzschia communis glide across surfaces under isotropic environmental conditions. We find a distinct kind of random motion, where trajectories are formed by circular arcs traveled at constant speed, alternated with random stoppages, direction reversals and changes in the orientation of the arcs. Analysis of experimental and computer-simulated trajectories show that the circular random motion of diatom gliding is not optimized for long-distance travel but rather for recurrent coverage of limited surface area. These results suggest that one main biological role for this type of diatom motility is to efficiently build the foundation of algal biofilms. PMID:25393453

Gutirrez-Medina, Braulio; Guerra, Andrs Jimnez; Maldonado, Ana Iris Pea; Rubio, Yadiralia Covarrubias; Meza, Jessica Viridiana Garca

2014-12-01

209

Silica Use Through Time: Macroevolutionary Change in the Morphology of the Diatom Fustule  

Microsoft Academic Search

Diatoms have evolved an obligate requirement for silica for their ornamented cell wall. Diatom productivity and subsequent burial of their siliceous remains on the ocean floor is a major control on the marine silica cycle. The ecological success of the diatoms over the Mesozoic and Cenozoic is associated with biogeographic shifts in siliceous sponges, decreasing silicification in the radiolarians, and

Zoe V. Finkel; Benjamin Kotrc

2010-01-01

210

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

211

Regional distribution of diatom assemblages in the headwater streams of Luxembourg  

Microsoft Academic Search

The aim of this study was to determine the influence of environmental variables on the structure of benthic diatom assemblages, and to propose type assemblages of diatoms characterizing unpolluted headwater streams of Luxembourg. A total of 289 diatom samples were collected in the headwater streams of Luxembourg. At each sampling site, physical and chemical variables were also measured. The relationships

F. Rimet; L. Ector; H. M. Cauchie; L. Hoffmann

2004-01-01

212

Spectrometric constraint in analysis of benthic diatom biomass using monospecific cultures  

Microsoft Academic Search

Among microphytobenthic species (unicellular algae and cyanobacteria), benthic diatoms are often the most common photosynthetic organisms colonizing shallow marine environment such as an intertidal flat. As such areas, particularly mudflats of limited access for point sampling, remote sensing techniques have the potential to map diatom biomass. This study used two monospecific cultures of the benthic diatoms Navicula ramosissima and Entomoneis

V. Mlder; L. Barill; P. Launeau; V. Carrre; Y. Rinc

2003-01-01

213

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

214

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.

215

Marine diatoms in polar and sub-polar environments and their application to Late Pleistocene paleoclimate  

E-print Network

of the diatom population. At a given threshold, physiologically dictated, diatoms undergo sexual reproduction division at a rate of 0.1-8 times per day [3]. Vegetative reproduction involves the formation of two new diminution continues in diatoms that did not reproduce sexually until they eventually die. Some species have an

216

COPPER-UPTAKE KINETICS OF COASTAL AND OCEANIC DIATOMS1 , Amber L. Annett3  

E-print Network

COPPER-UPTAKE KINETICS OF COASTAL AND OCEANIC DIATOMS1 Jian Guo2 , Amber L. Annett3 , Rebecca L We investigated copper (Cu) acquisition mecha- nisms and uptake kinetics of the marine diatoms organic Cu complexes. Key index words: copper; Cu; diatom; Fe; iron; kinetics; Thalassiosira; transport

217

Ballistic Penetration and Perforation of Thick FRP Laminates by Ogival-Nosed Projectiles  

Microsoft Academic Search

This article examines penetration and perforation of thick fiber-reinforced plastic (FRP) laminates struck by ogival-nosed projectiles at normal incidence. A forcing function representing the interaction between the projectile and the FRP laminates is derived by assuming that the deformation of FRP laminates is localized and that the pressure offered by the laminate targets to resist the projectiles is velocity dependent

T. He; H. M. Wen; Y. Qin

2007-01-01

218

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

219

Cenozoic planktonic marine diatom diversity and correlation to climate change  

USGS Publications Warehouse

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

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

2014-01-01

220

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 diatoms 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. PMID:19829762

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

2009-01-01

221

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

222

Role of nuclear Lamin A/C in cardiomyocyte functions.  

PubMed

Lamin A/C is a structural protein of the nuclear envelope (NE) and cardiac involvement in Lamin A/C mutations was one of the first phenotypes to be reported in humans, suggesting a crucial role of this protein in the cardiomyocytes function. Mutations in LMNA gene cause a class of pathologies generically named 'Lamanopathies' mainly involving heart and skeletal muscles. Moreover, the well-known disease called Hutchinson-Gilford Progeria Syndrome due to extensive mutations in LMNA gene, in addition to the systemic phenotype of premature aging, is characterised by the death of patients at around 13 typically for a heart attack or stroke, suggesting again the heart as the main site sensitive to Lamin A/C disfunction. Indeed, the identification of the roles of the Lamin A/C in cardiomyocytes function is a key area of exploration. One of the primary biological roles recently conferred to Lamin A/C is to affect contractile cells lineage determination and senescence. Then, in differentiated adult cardiomyocytes both the 'structural' and 'gene expression hypothesis' could explain the role of Lamin A in the function of cardiomyocytes. In fact, recent advances in the field propose that the structural weakness/stiffness of the NE, regulated by Lamin A/C amount in NE, can 'consequently' alter gene expression. PMID:25055884

Carmosino, Monica; Torretta, Silvia; Procino, Giuseppe; Gerbino, Andrea; Forleo, Cinzia; Favale, Stefano; Svelto, Maria

2014-10-01

223

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. PMID:22986494

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

2012-01-01

224

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

225

Bifurcations as dissociation mechanism in bichromatically driven diatomic molecules  

E-print Network

We discuss the influence of periodic orbits on the dissociation of a model diatomic molecule driven by a strong bichromatic laser fields. Through the stability of periodic orbits we analyze the dissociation probability when parameters like the two amplitudes and the phase lag between the laser fields, are varied. We find that qualitative features of dissociation can be reproduced by considering a small set of short periodic orbits. The good agreement with direct simulations demonstrates the importance of bifurcations of short periodic orbits in the dissociation dynamics of diatomic molecules.

S. Huang; C. Chandre; T. Uzer

2008-03-27

226

Effects of diatomic reagent alignment on the A + BC reaction  

NASA Technical Reports Server (NTRS)

A computational study is reported on the A + BC - AB + C bimolecular exchange reaction in which BC is aligned with respect to the approach direction of atom A so that the initial rotational angular momentum vector of BC is either parallel (or equivalently antiparallel) or perpendicular to the initial velocity vector of A. The calculations employ a modification of the extended LEPS potential, which permits straightforward generation of noncollinear minimum energy reaction paths. The calculations clearly demonstrate that diatomic reagent alignment can markedly affect the nature of reaction product early partitioning; they also demonstrate that diatomic reagent alignment affects reactive cross sections.

Pattengill, M. D.; Zare, R. N.; Jaffe, R. L.

1987-01-01

227

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

2011-03-15

228

Multi-Layer Laminated Thin Films for Inflatable Structures  

NASA Technical Reports Server (NTRS)

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

Yavrouian, Andre; Plett, Gary; Mannella, Jerami

2005-01-01

229

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

230

Accurate stress resultants equations for laminated composite deep thick shells  

SciTech Connect

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

Qatu, M.S. [Franklin Univ., Columbus, OH (United States)

1995-11-01

231

Vibration analysis of rotating thin laminated composite shell of revolution  

SciTech Connect

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

Suzuki, K.; Shikanai, G.; Takayama, K. [Yamagata Univ., Yonezawa (Japan). Faculty of Engineering

1995-11-01

232

Axisymmetric vibrations of laminated composite conical shells with varying thickness  

SciTech Connect

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

Shikanai, G.; Suzuki, K. [Yamagata Univ., Yonezawa (Japan). Faculty of Engineering; Kojima, M. [NEC Corporation, Tokyo (Japan)

1995-11-01

233

Diatom-induced silicon isotopic fractionation in Antarctic sea ice  

NASA Astrophysics Data System (ADS)

We measured silicon-isotopic composition of dissolved silicon and biogenic silica collected by sequential melting from spring 2003 Antarctic pack ice (Australian sector). Sea ice is a key ecosystem in the Southern Ocean and its melting in spring has been often thought to have a seeding effect for the surface waters, triggering blooms in the mixed layer. This work is the first investigation of the silicon isotopes' proxy in sea ice and allows to estimate the activity of sea-ice diatoms in the different brine structures and the influence of sea- ice diatoms on the spring ice edge blooms. The relative use of the dissolved silicon pool by sea-ice diatoms is usually assessed by calculating nutrient:salinity ratios in the brines. However such an approach is biased by difficulties in evaluating the initial nutrient concentrations in the different brines structures, and by the impossibility to account for late sporadic nutrient replenishments. The silicon-isotopic composition of biogenic silica is a convenient alternative since it integrates an average Si utilization on all generations of diatoms. Measurements were performed on a MC-ICP-MS, in dry plasma mode using external Mg doping. Results are expressed as delta29Si relative to the NBS28 standard. From three sea ice cores with contrasted physico-chemical characteristics, we report significant isotopic fractionations linked to the diatoms activity, with distinct silicon biogeochemical dynamics between different brine structure. The diatoms in snow ice and in brine pockets of frazil or congelation ice have the most positive silicon-isotopic composition (+0.53 to +0.86 p.mil), indicating that they grow in a closed system and use a significant part of the small dissolved silicon pool. In the brine channels and skeletal layer, diatoms display a relatively less positive Si-isotopic composition (+0.41 to +0.70 p.mil), although it is still heavier compared to equilibrium fractionation (+0.38 p.mil). This suggests that they have grown in a semi-closed system in which the dissolved silicon pool (i.e. brines) is partially replenished. Finally, we show that the average silicon-isotopic composition of the sea-ice diatoms (+0.63 p.mil) is very distinct from the one of biogenic silica in the seasonal ice zone mixed layer (+0.08 p.mil) indicating that sea- ice diatoms either contribute to an insignificant part of the whole diatoms biomass in the upper water layer (without affecting the silicon-isotopic budget), and/or that they are directly exported below the mixed layer. In this latter case, we will study the possibility to use the distinct signature of the sea ice diatoms as a tracer of paleo-sea ice extension in oceanic sediments.

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

2006-12-01

234

Analysis of "Kiss" Bonds Between Composite Laminates  

NASA Astrophysics Data System (ADS)

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

Poveromo, Scott L.; Earthman, James C.

2014-06-01

235

The Creep of Laminated Synthetic Resin Plastics  

NASA Technical Reports Server (NTRS)

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

Perkuhn, H

1941-01-01

236

Compression failure of angle-ply laminates  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

237

Combining ordination techniques and geostatistics to determine the patterns of diatom distributions at Lake Lama, Central Siberia  

Microsoft Academic Search

The patterns of spatial variation of diatom assemblages from surface sediments in Lake Lama were quantified using a combined approach of ordination and geostatistics. The aims were (i) to estimate the amount of variation between diatom assemblages within the lake, (ii) to model the spatial variability of the diatom assemblages and their diversity, and (iii) to map the diatom distributions

Ulrike Kienel; Thomas Kumke

2002-01-01

238

Diatom plastids depend on nucleotide import from the cytosol.  

PubMed

Diatoms are ecologically important algae that acquired their plastids by secondary endosymbiosis, resulting in a more complex cell structure and an altered distribution of metabolic pathways when compared with organisms with primary plastids. Diatom plastids are surrounded by 4 membranes; the outermost membrane is continuous with the endoplasmic reticulum. Genome analyses suggest that nucleotide biosynthesis is, in contrast to higher plants, not located in the plastid, but in the cytosol. As a consequence, nucleotides have to be imported into the organelle. However, the mechanism of nucleotide entry into the complex plastid is unknown. We identified a high number of putative nucleotide transporters (NTTs) in the diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum and characterized the first 2 isoforms (NTT1 and NTT2). GFP-based localization studies revealed that both investigated NTTs are targeted to the plastid membranes, and that NTT1 most likely enters the innermost plastid envelope via the stroma. Heterologously expressed NTT1 acts as a proton-dependent adenine nucleotide importer, whereas NTT2 facilitates the counter exchange of (deoxy-)nucleoside triphosphates. Therefore, these transporters functionally resemble NTTs from obligate intracellular bacteria with an impaired nucleotide metabolism rather than ATP/ADP exchanging NTTs from primary plastids. We suggest that diatoms harbor a specifically-adapted nucleotide transport system and that NTTs are the key players in nucleotide supply to the complex plastid. PMID:19221027

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

2009-03-01

239

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...

240

Contrasting size evolution in marine and freshwater diatoms  

PubMed Central

Diatoms are key players in the global carbon cycle and most aquatic ecosystems. Their cell sizes impact carbon sequestration and energy transfer to higher trophic levels. We report fundamental differences in size distributions of marine and freshwater diatoms, with marine diatoms significantly larger than freshwater species. An evolutionary game theoretical model with empirical allometries of growth and nutrient uptake shows that these differences can be explained by nitrogen versus phosphorus limitation, nutrient fluctuations and mixed layer depth differences. Constant and pulsed phosphorus supply select for small sizes, as does constant nitrogen supply. In contrast, intermediate frequency nitrogen pulses common in the ocean select for large sizes or the evolutionarily stable coexistence of large and small sizes. Size-dependent sinking interacts with mixed layer depth (MLD) to further modulate optimal sizes, with smaller sizes selected for by strong sinking and shallow MLD. In freshwaters, widespread phosphorus limitation, together with strong sinking and shallow MLD produce size distributions with smaller range, means and upper values, compared with the ocean. Shifting patterns of nutrient limitation and mixing may alter diatom size distributions, affecting global carbon cycle and the structure and functioning of aquatic ecosystems. PMID:19202058

Litchman, E.; Klausmeier, C. A.; Yoshiyama, K.

2009-01-01

241

The diatom Chaetoceros in ships' ballast waters - survivorship of stowaways  

Microsoft Academic Search

Ship ballast water discharged by vessels into the receiving port is recognised today as an important vector for the spread of non-indigenous species and facilitates the introduction of potential invasive species. Here, we report on 18 species (of about 30 identified), both vegetative cells and spores, of the diatom genus Chaetoceros Ehrenberg found in ballast water collected from ships arriving

GEORGIA KLEIN; I RENA KACZMARSKA; J AMES M. EHRMAN

2009-01-01

242

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

243

Human error and quality assurance in diatom analysis  

E-print Network

Kelly,M.G. Bayer,M.M. Hürlimann,J. Telford,R.J. In: Automatic Diatom Identification. Series in Machine Perception and Artificial Intelligence. Eds. du Buf, J M H & Bayer, M M. pp 75-92 World Scientific

Kelly, M.G.; Bayer, M.M.

244

CHECKLIST OF DIATOMS FROM THE LAURENTIAN GREAT LAKES  

EPA Science Inventory

An updated diatom checklist for the Great Lakes is provided. The present checklist supplants the preliminary checklist published in The Journal for Great Lakes Research in 1978 and effectively represents a 20-year update. A series of procedures were used in this update which incl...

245

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 Descls; Mathieu Vartanian; Abdeslam El Harrak; Michelle Quinet; Nicolas Bremond; Guillaume Sapriel; Jrome Bibette; Pascal J. Lopez

2008-01-01

246

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

247

UV effects on invertebrate and diatom assemblages of Greece.  

PubMed

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 developing periphytic communities during the study period. Exposure to solar UVB initially reduced the biomass and altered the structure of the diatom assemblages. The highest biomass of diatom assemblages was observed under PAR (49.2 g/m2). This value was significantly higher than the biomass of assemblages growing under PAR+UVA+UVB, but not significantly different compared to the biomass of assemblages exposed to PAR+UVA. These differences, however, did not persist at later stages. The most abundant invertebrate groups present were Polychaetes and Crustaceans. Solar UVB did not have significant effects on invertebrate biomass. Analysis of the invertebrate assemblage structure revealed time-course differences but no clear trends among the different treatments. PMID:11079478

Reizopoulou, S; Santas, P; Danielidis, D; Hder, D P; Santas, R

2000-07-01

248

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

249

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

250

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

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

251

Controlling Performance of Laminated Composites Using Piezoelectric Materials  

E-print Network

in tailoring the desired performance in the design of structures. The present study focuses on the failure analysis and shape control of smart composite laminates under coupled hygrothermal, electric and mechanical stimuli. A linear thermo...

Hasan, Zeaid

2012-02-14

252

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

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

253

Progressive Failure Analysis Methodology for Laminated Composite Structures  

NASA Technical Reports Server (NTRS)

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

Sleight, David W.

1999-01-01

254

Nuclear lamins during gametogenesis, fertilization and early development  

NASA Technical Reports Server (NTRS)

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

Maul, G. G.; Schatten, G.

1986-01-01

255

Mechanics of fatigue damage in titanium-graphite hybrid laminates  

E-print Network

Titanium-graphite hybrid laminates are being developed for high-temperature aerospace applications. Experimental observations have indicated that cracks in the titanium facesheets initiate at free edges as well as in areas ...

Burianek, Dennis Arthur

2001-01-01

256

Vibration analysis of composite laminate plate excited by piezoelectric actuators.  

PubMed

Piezoelectric materials can be used as actuators for the active vibration control of smart structural systems. In this work, piezoelectric patches are surface bonded to a composite laminate plate and used as vibration actuators. A static analysis based on the piezoelectricity and elasticity is conducted to evaluate the loads induced by the piezoelectric actuators to the host structure. The loads are then employed to develop the vibration response of a simply supported laminate rectangular plate excited by piezoelectric patches subjected to time harmonic voltages. An analytical solution of the vibration response of a simply supported laminate rectangular plate under time harmonic electrical loading is obtained and compared with finite element results to validate the present approach. The effects of location and exciting frequency of piezoelectric actuators on the vibration response of the laminate plate are investigated through a parametric study. Numerical results show that modes can be selectively excited, leading to structural vibration control. PMID:23529121

Her, Shiuh-Chuan; Lin, Chi-Sheng

2013-01-01

257

Optimal Synthesis of Hot Composite Laminates with Interphase Layers  

NASA Technical Reports Server (NTRS)

A method for the optimal grading of a single interphase layer in metal matrix composite laminates for the minimization of residual stresses is described. The capability to simultaneously tailor some fabrication parameters is also incorporated. Applications for unidirectional, cross-ply and quasi-isotropic Graphite/Copper laminates are investigated to assess the potential of interphase layer in reducing matrix residual stresses in various laminate configurations. Simultaneous optimization of interphase and fabrication characteristics appears to be more effective in decreasing residual stresses. The results also indicate that the interphase layer is more effective in lowering residual stresses in unidirectional composites and selectively within individual plies of a laminate. Embedded interphase layers in all the plies did not produce a significant global reduction in residual stresses.

Rabzak, Christopher; Saravanos, Dimitris A.; Chamis, Christos C.

1993-01-01

258

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

259

Observation of damage growth in compressively loaded laminates  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

260

Vibration Analysis of Composite Laminate Plate Excited by Piezoelectric Actuators  

PubMed Central

Piezoelectric materials can be used as actuators for the active vibration control of smart structural systems. In this work, piezoelectric patches are surface bonded to a composite laminate plate and used as vibration actuators. A static analysis based on the piezoelectricity and elasticity is conducted to evaluate the loads induced by the piezoelectric actuators to the host structure. The loads are then employed to develop the vibration response of a simply supported laminate rectangular plate excited by piezoelectric patches subjected to time harmonic voltages. An analytical solution of the vibration response of a simply supported laminate rectangular plate under time harmonic electrical loading is obtained and compared with finite element results to validate the present approach. The effects of location and exciting frequency of piezoelectric actuators on the vibration response of the laminate plate are investigated through a parametric study. Numerical results show that modes can be selectively excited, leading to structural vibration control. PMID:23529121

Her, Shiuh-Chuan; Lin, Chi-Sheng

2013-01-01

261

Finite Element Analyses for Radial Piezoelectric Mode Laminated Transducer  

Microsoft Academic Search

A novel laminated piezoelectric transducer was mainly composed of the piezoelectric ceramics, metal bolt, rubber gasket, copper electrode, waterproof layer and output cable. The transducer finite-element modeling was built, separately in the air and water, with ANSYS10.0 to calculate the resonance frequency, conductance, transmitting voltage response and directivity. The simulation showed that the laminated structure effectively improved the sensitivity of

Dong TianXiao; Wang LiKun; Qin Lei; Wu WeiWei; Wang Gang

2008-01-01

262

Fatigue life prediction of composite laminates by FEA simulation method  

Microsoft Academic Search

This paper is to simulate the fatigue damage evolution in composite laminates and predict fatigue life of the laminates with different lay-up sequences on the basis of the fatigue characteristics of longitudinal, transverse and in-plane shear directions by finite element analysis (FEA) method. In FEA model, considering the scatter of the materials properties, each element was assigned with different materials

Wei Lian; Weixing Yao

2010-01-01

263

Laminated microchannel devices, mixing units and method of making same  

DOEpatents

A laminated microchannel device is described in which there is a unit operation process layer that has longitudinal channel. The longitudinal channel is cut completely through the layer in which the unit process operation resides. Both the device structure and method of making the device provide significant advantages in terms of simplicity and efficiency. A static mixing unit that can be incorporated in the laminated microchannel device is also described.

Bennett, Wendy D [Kennewick, WA; Hammerstrom, Donald J [West Richland, WA; Martin, Peter M [Kennewick, WA; Matson, Dean W [Kennewick, WA

2002-10-17

264

Transverse Cracking and Stiffness Reduction in Composite Laminates  

Microsoft Academic Search

A systematic classification of the effects of transverse cracking on the stress-strain response of composite laminates is presented. Stiffness reductions resulting from transverse cracking in glass\\/epoxy and graphite\\/epoxy laminates from crack initiation to crack saturation are predicted using the stiffness-damage relationships developed by the author in a previous work. Good agreement with the experimental results is found. An assessment of

Ramesh Talreja

1985-01-01

265

Fracture analysis of local delaminations in laminated composites  

NASA Technical Reports Server (NTRS)

A shear deformation model was developed to analyze local delaminations growing from transverse cracks in 90 degree plies located around the mid plane of symmetric laminates. The predictions of the model agree reasonably with experimental data from T300/934 graphite epoxy laminates. The predicted behavior is such that, in combination with an edge delamination model, the critical loads can be predicted accurately in the range of n from .5 to 8.

Sriram, P.; Armanios, Erian A.

1988-01-01

266

A Lamination Micro Mixer for -Immunomagnetic Cell Sorter  

Microsoft Academic Search

We report successful design, fabrication and testing of a novel lamination micro mixer to be integrated in the micro-scale immunomagnetic cell sorter (-IMCS), which should be a key device for clinical applications of regenerative medicine. This paper covers, (i) the concept of -IMCS, (ii) design and fabrication of lamination mixer using MEMS technologies, (iii) numerical analysis for the evaluation of

Wei-Heong Tan; Yuji Suzuki; Nobuhide Kasagi; Naoki Shikazono; Katsuko Furukawa; Takashi Ushida

2005-01-01

267

Determination of the technical constants of laminates in oblique directions  

NASA Technical Reports Server (NTRS)

An off-axis tensile test theory based on Hooke's Law is applied to glass fiber reinforced laminates. A corrective parameter dependent on the characteristics of the strain gauge used is introduced by testing machines set up for isotropic materials. Theoretical results for a variety of strain gauges are compared with those obtained by a finite element method and with experimental results obtained on laminates reinforced with glass.

Vidouse, F.

1979-01-01

268

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. 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.

2013-01-01

269

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

2013-01-01

270

Three dimensional inelastic finite element analysis of laminated composites  

NASA Technical Reports Server (NTRS)

Formulations of the inelastic response of laminated composites to thermal and mechanical loading are used as the basis for development of the computer NALCOM (Nonlinear Analysis of Laminated Composites) computer program which uses a fully three dimensional isoparametric finite element with 24 nodes and 72 degrees of freedom. An incremental solution is performed with nonlinearities introduced as pseudoloads computed for initial strains. Equilibrium iteration may be performed at every step. Elastic and elastic-plastic response of boron/epoxy and graphite/epoxy graphite/epoxy and problems of curing 0/90 sub s Gr/Ep laminates with and without circular holes are analyzed. Mechanical loading of + or - 45sub s Gr/Ep laminates is modeled and symmetry conditions which exist in angle-ply laminates are discussed. Results are compared to experiments and other analytical models when possible. All models are seen to agree reasonably well with experimetnal results for off-axis tensile coupons. The laminate analyses show the three dimensional effects which are present near holes and free corners.

Griffin, O. H., Jr.; Kamat, M. P.

1980-01-01

271

Role of lamin b1 in chromatin instability.  

PubMed

Nuclear lamins play important roles in the organization and structure of the nucleus; however, the specific mechanisms linking lamin structure to nuclear functions are poorly defined. We demonstrate that reducing nuclear lamin B1 expression by short hairpin RNA-mediated silencing in cancer cell lines to approximately 50% of normal levels causes a delay in the cell cycle and accumulation of cells in early S phase. The S phase delay appears to be due to the stalling and collapse of replication forks. The double-strand DNA breaks resulting from replication fork collapse were inefficiently repaired, causing persistent DNA damage signaling and the assembly of extensive repair foci on chromatin. The expression of multiple factors involved in DNA replication and repair by both nonhomologous end joining and homologous repair is misregulated when lamin B1 levels are reduced. We further demonstrate that lamin B1 interacts directly with the promoters of some genes associated with DNA damage response and repair, including BRCA1 and RAD51. Taken together, the results suggest that the maintenance of lamin B1 levels is required for DNA replication and repair through regulation of the expression of key factors involved in these essential nuclear functions. PMID:25535332

Butin-Israeli, Veronika; Adam, Stephen A; Jain, Nikhil; Otte, Gabriel L; Neems, Daniel; Wiesmller, Lisa; Berger, Shelly L; Goldman, Robert D

2015-03-01

272

Effects of growth and dissolution on the fractionation of silicon isotopes by estuarine diatoms  

NASA Astrophysics Data System (ADS)

Studies of silicon (Si) isotope fractionation during diatom growth in open ocean systems have documented lower Si isotopic values (?30Si) in the biogenic silica of diatom frustules compared to dissolved silicon. Recent findings also indicate that Si isotope fractionation occurs during dissolution of diatom frustules, producing higher ?30Si values in the remaining biogenic silica. This study focuses on diatoms from high production areas in estuarine and coastal areas that represent approximately 30-50% of the global marine primary production. Two species of diatoms, Thalassiosira baltica and Skeletonema marinoi, were isolated from the brackish Baltic Sea, one of the largest estuarine systems in the world. These species were used for laboratory investigations of Si isotope fractionation during diatom growth and the subsequent dissolution of the diatom frustules. Both species of diatoms give an identical Si isotope fractionation factor during growth of -1.50 0.36 (2?) for 30Si, which falls in the range of -2.09 to -0.55 of published data. Our results also suggest a dissolution-induced Si isotope fractionation factor of -0.86 at early stage of dissolution, but this effect was observed only in DSi and no significant Si isotope change was observed for BSi. The growth and dissolution results are applied to a Baltic Sea sediment core to reconstruct DSi utilization by diatoms, and found to be in agreement with the observed DSi uptake rates in the overlying water column during diatom growth.

Sun, Xiaole; Olofsson, Martin; Andersson, Per S.; Fry, Brian; Legrand, Catherine; Humborg, Christoph; Mrth, Carl-Magnus

2014-04-01

273

Using diatom indices for water quality assessment in a subtropical river, China.  

PubMed

Diatoms have been regularly used as bioindicators to assess water quality of surface waters. However, diatom-based indices developed for a specific geographic region may not be appropriate elsewhere. We sampled benthic diatom assemblages in the upper Han River, a subtropical river in China, to evaluate applicability of 14 diatom-based indices used worldwide for water quality assessment. A total of 194 taxa from 31 genera were identified in the dry season and 139 taxa from 23 genera in the wet season. During the dry season, significant relationships were found for all but one of the diatom-based indices (Index Diatom Artois-Picardie) with one or more physical and chemical variables including nutrients and ion concentrations in river waters. The Biological Diatom Index (IBD) and diatom-based eutrophication/pollution index (EPI-D) were strongly related to trophic status and ionic content, while Watanabe's Index was related to organic pollution and conductivity. Yet, the diatom indices showed weak relationships with physical and chemical variables during the wet season. It suggests that diatom-based indices developed in Europe can be applied with confidence as bioindicators of water quality in subtropical rivers of China, at least during base-flow conditions. PMID:23247517

Tan, Xiang; Sheldon, Fran; Bunn, Stuart E; Zhang, Quanfa

2013-06-01

274

Analysis of damage in composite laminates under bending  

NASA Astrophysics Data System (ADS)

The focus of this research was damage formation in composite laminates subjected to bending. Matrix cracking and internal delamination are common damage modes before final failure for a composite laminate under thermo-mechanical loading. Two configurations of cross-ply laminates, namely [0m/90 n]s and [90m/0n]s, were considered for the study. Approximate analytical solutions for the stress states in the two laminates subjected to constant bending moment, with matrix cracks in the 90 layers, were derived using a variational approach. The evolution of matrix cracking under monotonically increasing load was studied for a number of composite materials. The analytical predictions showed an initial stage of rapid matrix crack multiplication followed by a slowing down in the crack multiplication. In the case of [0m/90n] s laminate, 0 ply failure in tension or compression was found to be likely even at the initial stages of matrix cracking for laminates with thin 90 layer. The 0 ply failure is delayed for laminates with thicker 90 layer. The analytical model for the stress state in the [90m/0 n]s laminate was extended to include delamination from the matrix crack-tip along the 0/90 interface. The bending moment required to initiate crack-tip delamination was computed as a function of the crack density. By comparing this result with matrix crack evolution, the relative dominance of the two modes of damage could be determined. The critical crack density beyond which delamination dominates matrix cracking is obtained from the analysis. The critical crack density is interpreted as the stage beyond which growth of delamination rather than matrix cracking is likely to occur. Parametric studies conducted by varying the laminate configuration showed that the critical crack density for delamination onset strongly depends on the thickness of the 90 layer and the distance of the 90 layer from the laminate mid-plane. Quasi-static growth of delamination under monotonic loading was studied for the laminate with matrix cracking of critical density. Comparison of the load for delamination growth with the load for possible formation of further matrix cracking was done to determine the possibility of matrix cracking after delamination. Predictions for different laminate lay-ups of a graphite/epoxy system showed the possibility of matrix cracking after delamination grew to a critical length. This critical delamination length was found to be close to the crack spacing in most of the cases considered, i.e. further matrix cracking is likely to occur only after a large portion of the laminate between two consecutive cracks delaminates. Possible failure of 0 layer before further matrix cracking was predicted for laminates with thin 90 layer.

Kuriakose, Sunil

275

Damage growth in composite laminates with interleaves  

NASA Technical Reports Server (NTRS)

The influence of placing interleaves between fiber reinforced plies in multilayered composite laminates is investigated. The geometry of the composite is idealized as two dimensional, isotropic, linearly elastic media made of a damaged layer bonded between two half planes and separated by thin interleaves of low extensional and shear moduli. The damage in the layer is taken in the form of a symmetric crack perpendicular to the interface and may extend up to the interface. The case of an H-shaped crack in the form of a broken layer with delamination along the interface is also analyzed. The interleaves are modeled as distributed shear and tension springs. Fourier integral transform techniques are used to develop solutions in terms of singular integral equations. An asymptotic analysis of the integral equations based on Muskhelishvili's techniques reveals logarithmically singular axial stresses in the half plane at the crack tips for the broken layer. For the H shaped crack, similar singularities are found to exist in the axial stresses at the interface crack tips in the layer and the half plane. The solution of the equations is found numerically for the stresses and displacements by using the Hadamard's concept of direct differentiation of Cauchy integrals as well as Gaussian integration techniques.

Goree, James G.

1987-01-01

276

40 CFR 63.5865 - What data must I generate to demonstrate compliance with the standards for continuous lamination...  

...compliance with the standards for continuous lamination/casting operations? 63.5865 Section...compliance with the standards for continuous lamination/casting operations? (a) For continuous lamination/casting affected sources...

2014-07-01

277

40 CFR 63.5865 - What data must I generate to demonstrate compliance with the standards for continuous lamination...  

Code of Federal Regulations, 2011 CFR

...compliance with the standards for continuous lamination/casting operations? 63.5865 Section...compliance with the standards for continuous lamination/casting operations? (a) For continuous lamination/casting affected sources...

2011-07-01

278

40 CFR 63.5865 - What data must I generate to demonstrate compliance with the standards for continuous lamination...  

Code of Federal Regulations, 2013 CFR

...compliance with the standards for continuous lamination/casting operations? 63.5865 Section...compliance with the standards for continuous lamination/casting operations? (a) For continuous lamination/casting affected sources...

2013-07-01

279

40 CFR 63.5820 - What are my options for meeting the standards for continuous lamination/casting operations?  

Code of Federal Regulations, 2011 CFR

...meeting the standards for continuous lamination/casting operations? 63.5820...lamination line and each continuous casting line complies with the applicable...continuous lamination and continuous casting lines combined, comply...

2011-07-01

280

40 CFR Table 11 to Subpart Wwww of... - Data Requirements for New and Existing Continuous Lamination and Continuous Casting Lines...  

Code of Federal Regulations, 2011 CFR

...Existing Continuous Lamination and Continuous Casting Lines Complying With a Percent...Existing Continuous Lamination and Continuous Casting Lines Complying With a Percent...continuous lamination lines and continuous casting lines you must determine...

2011-07-01

281

40 CFR 63.5865 - What data must I generate to demonstrate compliance with the standards for continuous lamination...  

Code of Federal Regulations, 2010 CFR

...compliance with the standards for continuous lamination/casting operations? 63.5865 Section...compliance with the standards for continuous lamination/casting operations? (a) For continuous lamination/casting affected sources...

2010-07-01

282

40 CFR Table 11 to Subpart Wwww of... - Data Requirements for New and Existing Continuous Lamination and Continuous Casting Lines...  

Code of Federal Regulations, 2013 CFR

...Existing Continuous Lamination and Continuous Casting Lines Complying With a Percent...Existing Continuous Lamination and Continuous Casting Lines Complying With a Percent...continuous lamination lines and continuous casting lines you must determine...

2013-07-01

283

40 CFR Table 11 to Subpart Wwww of... - Data Requirements for New and Existing Continuous Lamination and Continuous Casting Lines...  

Code of Federal Regulations, 2012 CFR

...Existing Continuous Lamination and Continuous Casting Lines Complying With a Percent...Existing Continuous Lamination and Continuous Casting Lines Complying With a Percent...continuous lamination lines and continuous casting lines you must determine...

2012-07-01

284

40 CFR 63.5820 - What are my options for meeting the standards for continuous lamination/casting operations?  

...meeting the standards for continuous lamination/casting operations? 63.5820...lamination line and each continuous casting line complies with the applicable...continuous lamination and continuous casting lines combined, comply...

2014-07-01

285

40 CFR 63.5865 - What data must I generate to demonstrate compliance with the standards for continuous lamination...  

Code of Federal Regulations, 2012 CFR

...compliance with the standards for continuous lamination/casting operations? 63.5865 Section...compliance with the standards for continuous lamination/casting operations? (a) For continuous lamination/casting affected sources...

2012-07-01

286

40 CFR 63.5820 - What are my options for meeting the standards for continuous lamination/casting operations?  

Code of Federal Regulations, 2012 CFR

...meeting the standards for continuous lamination/casting operations? 63.5820...lamination line and each continuous casting line complies with the applicable...continuous lamination and continuous casting lines combined, comply...

2012-07-01

287

40 CFR 63.5820 - What are my options for meeting the standards for continuous lamination/casting operations?  

Code of Federal Regulations, 2010 CFR

...meeting the standards for continuous lamination/casting operations? 63.5820...lamination line and each continuous casting line complies with the applicable...continuous lamination and continuous casting lines combined, comply...

2010-07-01

288

40 CFR Table 11 to Subpart Wwww of... - Data Requirements for New and Existing Continuous Lamination and Continuous Casting Lines...  

...Existing Continuous Lamination and Continuous Casting Lines Complying With a Percent...Existing Continuous Lamination and Continuous Casting Lines Complying With a Percent...continuous lamination lines and continuous casting lines you must determine...

2014-07-01

289

40 CFR 63.5820 - What are my options for meeting the standards for continuous lamination/casting operations?  

Code of Federal Regulations, 2013 CFR

...meeting the standards for continuous lamination/casting operations? 63.5820...lamination line and each continuous casting line complies with the applicable...continuous lamination and continuous casting lines combined, comply...

2013-07-01

290

Tape cast bioactive metal-ceramic laminates for structural application  

NASA Astrophysics Data System (ADS)

Bioglass 45S5, is a silica based glass which is able to rapidly form strong bonds with bone and soft tissue in vivo. It is used clinically to replace damaged ear ossicles and in dental surgery to help maintain the structural integrity of the jaw bone. The goal of the research was to demonstrate that Bioglass can be toughened by lamination with metallic layers while maintaining bioactivity. Improvement of the mechanical properties of Bioglass 45SS would allow for additional clinical applications, such as fracture fixation plates, or vertebral spacers. Bioglass 45S5 was tape cast and laminated with clinically relevant metals (316L, stainless steel and titanium) as well as copper in an effort to demonstrate that the effective toughness, or area under the load-deflection diagram can be increased significantly through ductile layer lamination. The average strength of monolithic tape cast sintered Bioglass was as high as 150 MPa and the toughness measured approximately 1.0 MPa m1/2. Copper-Bioglass laminates clearly demonstrated the toughening effect of metal layers on tape cast sintered Bioglass 45S5. Steel-Bioglass laminates, although less tough than the copper-Bioglass laminates, showed higher strengths. In vitro bioactivity tests of both titanium and steel Bioglass laminates showed the formation of mature and thick hydroxyapatite layers after 24 hours in Tris buffer solution. Under the standard test conditions, the bioactivity of monolithic tape cast sintered Bioglass increased with increasing sintering temperature. For samples sintered at 1000C, thick crystalline layers of hydroxyapatite formed within 24 hours in Tris buffer solution. The bioactivity of these samples approached that of amorphous bulk Bioglass. Samples processed at 800C were able to form thick crystalline hydroxyapatite layer after 24 hours when the test solution volume was increased by eight times.

Clupper, Daniel Christopher

291

Do diatoms run downhill? Using biodiversity of terrestrial and aquatic diatoms to identify hydrological connectivity between aquatic zones in Luxembourg  

NASA Astrophysics Data System (ADS)

Diatoms are siliceous unicellular algae, and range in size between a few and more than 500 micrometers. Diatoms are spread worldwide, live in many aquatic habitats, have many life forms and their short generation time make them respond rapidly to environmental changes. Their taxonomic diversity represents a valuable tool to assess water quality as each taxon has specific responses to environmental factors. Recently, diatoms have been used as tracers to detect the onset/cessation of surface runoff through binary classification of terrestrial and aquatic species in the Attert basin in Luxembourg. In order to continue the validation of these first results, we have collected samples during rain events at different seasons of the year using automatic stream water samplers, grab samples of diatoms from various terrestrial and subaerial substrates (bryophytes, litter and leaves), as well as from aquatic habitats (epilithon, epipelon and drift samples). This new type of information will be used to constrain assumptions of the conventional tracer-based hydrograph separation technique (i.e. using geochemistry and stable isotopes). The first results concerning the diatom flora, based on 39 samples, revealed 152 species belonging to 38 genera. The most species-rich genera were Pinnularia (15.8% - 24 taxa), Eunotia (13.2% - 20 taxa), Gomphonema (8.6% - 13 taxa), Navicula (7.2% - 11 taxa) and Stauroneis (5.3% - 8 taxa). The flora are mainly composed of oligotrophic and/or acidophilic taxa (32.0%), ubiquitous (14.0%) or poorly known ecologically species (43.0%). The most important taxa found in drift samples were Fragilariforma virescens, Fragilaria capucina sensu lato, Planothidium lanceolatum, Eunotia minor, Achnanthidium kranzii, Karayevia oblongella and Eunotia incisa. In the riparian zone (n = 10), 102 species were observed, with Eunotia exigua var. tenella, Eunotia botuliformis and Pinnularia perirrorata being among the most frequent. Epilithic samples from the main channel have been represented mainly by monoraphid species such as Achnanthidium subatomoides and Achnanthidium minutissimum. A general qualitative overview of the diatom flora - concerning specific ecological requirements of the taxa - showed that most diatom species are characteristic of the riparian zone (30%), while 12% are typical of the riparian/upland transition zone. Only 3% of species are strictly freshwater (Aquatic zone) forms and 8% stem from the aquatic/riparian zone. The qualitative analysis of drift collected by automatic samplers showed that during floods the origin of diatom species partly stems from riparian and/or terrestrial-upland habitats. Additional investigations over a longer period and range of events are being conducted. Furthermore, the study of the biodiversity of diatoms in this small catchment will also contribute to a better definition of the ecological preferences of many species which are still poorly known to date.

Pfister, L.; Wetzel, C. E.; Martinez-Carreras, N.; Frentress, J.; Ector, L.; Hoffmann, L.; McDonnell, J. J.

2011-12-01

292

Muscle dystrophy-causing ?K32 lamin A/C mutant does not impair functions of nucleoplasmic LAP2? - lamin A/C complexes in mice  

PubMed Central

Summary A-type lamins are components of the nuclear lamina, a filamentous network of the nuclear envelope in metazoans that supports nuclear architecture. In addition, lamin A/C can also be found in the nuclear interior. This nucleoplasmic lamin pool is soluble in physiological buffer, depends on the presence of the lamin-binding protein, Lamina-associated polypeptide 2? (LAP2?) and regulates cell cycle progression in tissue progenitor cells. ?K32 mutations in A-type lamins cause severe congenital muscle disease in humans and a muscle maturation defect in Lmna?K32/?K32 knock-in mice. At molecular level, mutant ?K32 lamin A/C protein levels were reduced and all mutant lamin A/C was soluble and mislocalized to the nucleoplasm. To test the role of LAP2? in nucleoplasmic ?K32 lamin A/C regulation and functions, we deleted LAP2? in Lmna?K32/?K32 knock-in mice. In double mutant mice the Lmna?K32/?K32- linked muscle defect was unaffected. LAP2? interacted with mutant lamin A/C, but unlike wild-type lamin A/C, the intranuclear localization of ?K32 lamin A/C was not affected by loss of LAP2?. In contrast, loss of LAP2? in Lmna?K32/?K32 mice impaired the regulation of tissue progenitor cells like in lamin A/C wild type animals. These data indicate that a LAP2?-independent assembly defect of ?K32 lamin A/C is predominant for the mouse pathology, while the LAP2?-linked functions of nucleoplasmic lamin A/C in the regulation of tissue progenitor cells are not affected in Lmna?K32/?K32 mice. PMID:23444379

Pilat, Ursula; Dechat, Thomas; Bertrand, Anne T; Woisetschlger, Nikola; Gotic, Ivana; Spilka, Rita; Biadasiewicz, Katarzyna; Bonne, Gisle; Foisner, Roland

2015-01-01

293

Neural Network predictions of Diatomic and Triatomic Molecular Data  

NASA Astrophysics Data System (ADS)

The arrangement of molecules in periodic systems offers an enhanced comprehension of trends in molecular properties, a more efficient method of sorting and searching of molecular databases, and bases for the prediction of new data. Neural networks have the ability to "learn" existing data and to forecast a large amount of new data without a smoothing equation.(R. Hefferlin, B. Davis, W. B. Laing, "The Learning and Prediction of Triatomic Molecular Data with Neural Networks," International Arctic Seminar 1997, Murmansk, Russia)(J. Wohlers, W. B. Laing, R. Hefferlin, and B. Daivs, "Least-Squares and Neural-Network Forecasting from Citical Data: Diatomic Molecular Internuclear Separations and Triatomic Heats of Atomization and Ionization Potentials," Advances in Molecular Similarity: JIA book series, in press) This report will present periodic systems of molecules as well as neural network predictions for additional properties of diatomic and triatomic molecules.

Blake Laing, W.

1997-11-01

294

Photosynthetic energy conversion in the diatom Phaeodactylum tricornutum  

Microsoft Academic Search

Isothermal microcalorimetry can be used to investigate the photosynthetic energy conversion of autotrophic organisms. In this\\u000a study, for the first time a diatom alga was used to compare the calorimetrically measured heat flux with measurements of the\\u000a photosynthetic performance by oxygen evolution and pulse-amplitude modulated fluorescence. The presented experimental setup\\u000a proved suitable to compare calorimetric data with those of conventional

Steffen Oroszi; Torsten Jakob; Christian Wilhelm; Hauke Harms; Thomas Maskow

2011-01-01

295

Molecular dynamics study for the thermal conductivity of diatomic liquid  

Microsoft Academic Search

The thermal conductivity of diatomic liquids was analyzed using a nonequilibrium molecular dynamics (NEMD) method. Five liquids, namely, O2, CO, CS2, Cl2 and Br2, were assumed. The two-center Lennard-Jones (2CLJ) model was used to express the intermolecular potential acting on liquid molecules. First, the equation of state of each liquid was obtained using MD simulation, and the critical temperature, density

Takashi Tokumasu; Kenjiro Kamijo

2004-01-01

296

Direct imaging of quantum wires nucleated at diatomic steps  

SciTech Connect

Atomic steps at growth surfaces are important heterogeneous sources for nucleation of epitaxial nano-objects. Here we report on the direct imaging of a diatomic interface step between a horizontal nanowire and the substrate on which this nano-object has been formed by a self-assembly process. The nucleation process of this nano-object is shown to take place preferentially on the upper terrace surface of the step as a result of the local stress relaxation.

Molina Rubio, Sergio I [ORNL; Varela del Arco, Maria [ORNL; Sales Lerida, David [ORNL; Ben, Teresa [Universidad de Cadiz, Spain; Pizarro, Joaquin [Universidad de Cadiz, Spain; Galindo, Pedro [Universidad de Cadiz, Spain; Fuster, David [Instituto de Microelectronica de Madrid (CNM, CSIC); Gonzalez, Yolanda [Instituto de Microelectronica de Madrid (CNM, CSIC); Gonzalez, Luisa [Instituto de Microelectronica de Madrid (CNM, CSIC); Pennycook, Stephen J [ORNL

2007-01-01

297

Configurations of polyunsaturated sesterterpenoids from the diatom, Haslea ostrearia.  

PubMed

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 beta-diketonate complexes and enantioselective gas chromatography of oxidation products of the alkenes was used. Unexpected differences in highly branched isoprenoid isomer configurations were observed between different laboratory cultures of the alga. PMID:10724188

Johns, L; Belt, S; Lewis, C A; Rowland, S; Mass, G; Robert, J M; Knig, W A

2000-03-01

298

Novel Sex Cells and Evidence for Sex Pheromones in Diatoms  

PubMed Central

Background Diatoms belong to the stramenopiles, one of the largest groups of eukaryotes, which are primarily characterized by a presence of an anterior flagellum with tubular mastigonemes and usually a second, smooth flagellum. Based on cell wall morphology, diatoms have historically been divided into centrics and pennates, of which only the former have flagella and only on the sperm. Molecular phylogenies show the pennates to have evolved from among the centrics. However, the timing of flagellum loss whether before the evolution of the pennate lineage or after is unknown, because sexual reproduction has been so little studied in the araphid basal pennate lineages, to which Pseudostaurosira belongs. Methods/Principal Finding Sexual reproduction of an araphid pennate, Pseudostaurosira trainorii, was studied with light microscopy (including time lapse observations and immunofluorescence staining observed under confocal scanning laser microscopy) and SEM. We show that the species produces motile male gametes. Motility is mostly associated with the extrusion and retrieval of microtubule-based threads, which are structures hitherto unknown in stramenopiles, their number varying from one to three per cell. We also report experimental evidence for sex pheromones that reciprocally stimulate sexualization of compatible clones and orientate motility of the male gametes after an initial random walk. Conclusions/Significance The threads superficially resemble flagella, in that both are produced by male gametes and contain microtubules. However, one striking difference is that threads cannot beat or undulate and have no motility of their own, and they do not bear mastigonemes. Threads are sticky and catch and draw objects, including eggs. The motility conferred by the threads is probably crucial for sexual reproduction of P. trainorii, because this diatom is non-motile in its vegetative stage but obligately outbreeding. Our pheromone experiments are the first studies in which gametogenesis has been induced in diatoms by cell-free exudates, opening new possibilities for molecular dissection of sexualization. PMID:22046412

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

2011-01-01

299

ADIAC: Using computer vision technology for automatic diatom identification  

E-print Network

Bayer,M.M. Pullan,M. Mann,D. Juggins,S. Ciobanu,A. Santos,L. Shahbazkia,H. du Buf,H. Fischer,S. Bunke,H. Wilkinson,M. Roerdink,J.B.T.M. Pech-Pacheco,J-L. Cristobal,G. Cirimele,V. Ludes,B. Proceedings of the 16th International Diatom Symposium (A. Economou - Amilli, ed.), University of Athens, Greece. pp 537-562

Bayer, M.M.

300

Nuclear-spin dependent parity violation in diatomic molecular ions  

E-print Network

Nuclear-spin-dependent (NSD) parity violating (PV) effects can be strongly enhanced in diatomic molecules containing heavy atoms. Future measurements are anticipated to provide nuclear anapole moments and strength constants for PV nuclear forces. In light molecules, the NSD electroweak electron-nucleus interaction may also be detected. Here we calculate NSD PV effects for molecular ions. Our calculations are motivated by rapid developments in trapping techniques for such systems at low temperatures.

Borschevsky, A; Dzuba, V A; Beloy, K; Flambaum, V V; Schwerdtfeger, P A

2012-01-01

301

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

PubMed

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 (241)Am from water. In our experiments large particles of seston (>8mum), comparable in size with diatoms, took up most of americium from water. The accumulation of americium by isolated diatom algae (Asterionella formosa and Diatoma vulgare) was lower than by total seston. The concentration factors (CFs) of (241)Am for seston of the Yenisei River in our experiments were (2.8-6.9).10(5); for diatoms - (1.5-4.2).10(4). The CFs for aquatic plant Elodea canadensis were within the same order of magnitude as those for diatoms. Activity concentration and CFs of (241)Am were nearly the same in experiments under dark and light conditions. This is indicative of an energy independent mechanism of americium uptake from the water by diatoms and submerged macrophytes. PMID:19879676

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

2010-02-01

302

Analytical study for deformability of laminated sheet metal  

PubMed Central

While a freestanding high-strength sheet metal subject to tension will rupture at a small strain, it is anticipated that lamination with a ductile sheet metal will retard this instability to an extent that depends on the relative thickness, the relative stiffness, and the hardening exponent of the ductile sheet. This paper presents an analytical study for the deformability of such laminate within the context of necking instability. Laminates of high-strength sheet metal and ductile low-strength sheet metal are studied assuming: (1) sheets are fully bonded; and (2) metals obey the power law material model. The effect of hardening exponent, volume fraction and relative stiffness of the ductile component has been studied. In addition, stability of both uniform and nonuniform deformations has been investigated under plane strain condition. The results have shown the retardation of the high-strength layer instability by lamination with the ductile layer. This has been achieved through controlling the aforementioned key parameters of the ductile component, while the laminate exhibits marked enhancement in strengthductility combination that is essential for metal forming applications.

Serror, Mohammed H.

2012-01-01

303

Dynamic Stability of Uncertain Laminated Beams Under Subtangential Loads  

NASA Technical Reports Server (NTRS)

Because of the inherent complexity of fiber-reinforced laminated composites, it can be challenging to manufacture composite structures according to their exact design specifications, resulting in unwanted material and geometric uncertainties. In this research, we focus on the deterministic and probabilistic stability analysis of laminated structures subject to subtangential loading, a combination of conservative and nonconservative tangential loads, using the dynamic criterion. Thus a shear-deformable laminated beam element, including warping effects, is derived to study the deterministic and probabilistic response of laminated beams. This twenty-one degrees of freedom element can be used for solving both static and dynamic problems. In the first-order shear deformable model used here we have employed a more accurate method to obtain the transverse shear correction factor. The dynamic version of the principle of virtual work for laminated composites is expressed in its nondimensional form and the element tangent stiffness and mass matrices are obtained using analytical integration The stability is studied by giving the structure a small disturbance about an equilibrium configuration, and observing if the resulting response remains small. In order to study the dynamic behavior by including uncertainties into the problem, three models were developed: Exact Monte Carlo Simulation, Sensitivity Based Monte Carlo Simulation, and Probabilistic FEA. These methods were integrated into the developed finite element analysis. Also, perturbation and sensitivity analysis have been used to study nonconservative problems, as well as to study the stability analysis, using the dynamic criterion.

Goyal, Vijay K.; Kapania, Rakesh K.; Adelman, Howard (Technical Monitor); Horta, Lucas (Technical Monitor)

2002-01-01

304

Bending Boundary Layers in Laminated-Composite Circular Cylindrical Shells  

NASA Technical Reports Server (NTRS)

A study of the attenuation of bending boundary layers in balanced and unbalanced, symmetrically and unsymmetrically laminated cylindrical shells is presented for nine contemporary material systems. The analysis is based on the linear Sanders-Koiter shell equations and specializations to the Love-Kirchhoff shell equations and Donnell's equations are included. Two nondimensional parameters are identified that characterize the effects of laminate orthotropy and anisotropy on the bending boundary-layer decay length in a very general manner. A substantial number of structural design technology results are presented for a wide range of laminated-composite cylinders. For all laminates considered, the results show that the differences between results obtained with the Sanders-Koiter shell equations, the Love-Kirchhoff shell equations, and Donnell's equations are negligible. The results also show that the effect of anisotropy in the form of coupling between pure bending and twisting has a negligible effect on the size of the bending boundary-layer decay length of the balanced, symmetrically laminated cylinders considered. Moreover, the results show that coupling between the various types of shell anisotropies has a negligible effect on the calculation of the bending boundary-layer decay length in most cases. The results also show that, in some cases, neglecting the shell anisotropy results in underestimating the bending boundary-layer decay length and, in other cases, results in an overestimation.

Nemeth, Michael P.; Smeltzer, Stanley S., III

2000-01-01

305

Leukocyte emigration in the early stages of laminitis.  

PubMed

The mechanisms that initiate the pathophysiologic changes in the digital laminae in equine laminitis are poorly understood. Due to the fact that (1) the horse at risk of laminitis has many similarities clinically to the human sepsis patient and (2) our recent finding of marked laminar proinflammatory cytokine expression at the developmental time point of the black walnut extract (BWE) model of laminitis, we tested the possibility that, similar to organ damage in human sepsis, leukocyte emigration is an early event in laminitis. Using immunoperoxidase methods with an anti-equine CD13 monoclonal antibody that recognizes neutrophils and monocytes, we discovered that, whereas the dermal microvasculature of the skin commonly has a marginal pool of leukocytes, the normal laminar dermal microvasculature has minimal to no perivascular leukocytes. However, increases in leukocyte numbers occurred around the dermal vasculature of both the laminae and the skin in the majority of BWE-treated horses in the developmental stage and at the onset of clinical signs of lameness in the BWE model. These findings indicate that, similar to organ failure in human sepsis, leukocyte emigration is likely to play a significant role in initiating numerous pathophysiologic mechanisms that lead to the development of laminitis. PMID:16169600

Black, Samuel J; Lunn, D Paul; Yin, Cailing; Hwang, Misako; Lenz, Stephen D; Belknap, James K

2006-01-15

306

Paleoenvironmental impact of volcanic eruptions indicated by diatoms  

SciTech Connect

Cores of postglacial sediment obtained from small ponds/marshes in west central Montana include several tephra layers representing the series of eruptions of Glacier Peak of about 11,200 years B.P. and of Mount Mazama of about 6600 years B.P. The sediment consists of a basal unit of rock flour overlain by diatomite and other biogenic sediment. Analysis of the palynoflora and the diverse diatom flora indicate that the water was very low in dissolved solid and slightly acid from the time of the beginning of biogenic sedimentation until the present except for times immediately following deposition of each of the two layers of Glacier Peak tephra. Large numbers of Navicula simplex Krasske occur immediately above each of these layers of tephra. This halophilous and alkaliphilous diatom species indicates a short-term change in the chemistry of the pond. After a short period, the solutes carried to the pond by the tephra were washed out of the system allowing it to return to its normal condition, and the halophilous species disappeared. No occurrence of such indicator species was found associated with the younger Mazama tephra. The diatom flora at this site appears to have recorded a paleoenvironmental impact of the eruptions of Glacier Peak hundreds of kilometers from the volcano.

Brant, L.A.; Bahls, L.L.

1985-01-01

307

PCB-resistant diatoms in the Hudson River estuary  

NASA Astrophysics Data System (ADS)

Diatom cells that are resistant, as well as sensitive, to the toxicity of polychlorinated biphenyls (PCB) are widespread throughout the highly polluted Hudson River estuary. A study of the distribution of PCB resistance among populations of the diatoms, Thalassiosira nordenskioldii and Asterionella glacialis, revealed few spatial or temporal patterns for the trait during spring and summer. The number of estuarine clones of A. glacialis tolerant of more than 25 ppb of PCB was greater than twice the number of clones isolated from nearshore waters at Sandy Hook, NJ. This suggests that selection pressure for PCB resistance is greater in the estuary than in the New York Bight apex. If specific sites of selection exist, the mixing of cells within the estuary may be rapid enough to distribute resistant clones throughout the estuary, or the selection process may involve a generalized response to a multitude of pollutants. Several clones of both species tested were not only tolerant of PCB, but were actually enhanced in their growth in the presence of PCB. Such clones were distributed throughout the estuary during both seasons. Selection in the estuary favours not only resistant strains of diatoms, but forms that may utilize organic pollutants.

Cosper, Elizabeth M.; Wurster, Charles F.; Bautista, Mark F.

1988-02-01

308

Variable stereochemistry in highly branched isoprenoids from diatoms.  

PubMed

C(25) highly branched isoprenoid (HBI) alkenes are ubiquitous lipids found in geochemical samples around the globe. The origins of these widespread geochemicals are believed to be restricted to a limited number of diatoms, including Haslea ostrearia (and related species), Rhizosolenia setigera, and Pleurosigma intermedium. The unsaturation of the HBI alkenes ranges from 2-6 in different species and cultures. The number of stereogenic centres is usually limited to two in the HBI alkenes due to double bond positions. The relative and/or absolute configurations for these have been determined for a range of HBI alkenes produced from different diatoms cultured under a number of growth conditions. These determinations have involved a combined spectroscopic and chromatographic analysis using NMR spectroscopy and chiral gas chromatography, respectively. HBIs isolated from Haslea spp. belong to a specific structural type which exhibit configurational diastereoisomerism, while those isolated from P. intermedium and R. setigera represent a different structural type and usually exist as mixtures of geometric isomers only. HBIs are reported from a new species of diatom whose stereochemical properties lie between those found for Haslea spp. and P. intermedium. PMID:11466760

Belt, S T; Allard, W G; Johns, L; Knig, W A; Mass, G; Robert, J M; Rowland, S

2001-08-01

309

A Late Quaternary diatom record of tropical climatic history from Lake Titicaca (Peru and Bolivia)  

Microsoft Academic Search

A composite high-resolution diatom stratigraphy from three piston cores and one box-core in the deep sub-basin of Lake Titicaca reveals large moisture variations during the past 30 kyr in the Altiplano region. Diatom sequences indicate orbital and millennial-scale variability in water level and salinity. The pelagic freshwater diatom species Cyclotella andina and Cyclotella stelligera dominate Glacial-age sediments, suggesting that the

Pedro M Tapia; Sherilyn C Fritz; Paul A Baker; Geoffrey O Seltzer; Robert B Dunbar

2003-01-01

310

Diatoms as indicators in the Environmental Monitoring and Assessment Program-Surface Waters (EMAP-SW)  

Microsoft Academic Search

As a part of the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program-Surface Waters (EMAP-SW), sedimentary diatom assemblages were studied from 66 lakes in the northeastern U.S.A. to evaluate the applicability of diatoms for this nation-wide monitoring program. Sediment cores were collected from the study lakes and diatoms were analyzed from the top (present-day) and bottom (pre-industrial) sediment samples.

Sushil S. Dixit; John P. Smol

1994-01-01

311

Toxigenic effects of diatoms on grazers, phytoplankton and other microbes: a review  

Microsoft Academic Search

Traditionally, diatoms have been regarded as providing the bulk of the food that sustains the marine food chain and important\\u000a fisheries. However, this view was challenged almost two decades ago on the basis of laboratory and field studies showing that\\u000a when copepods, the principal predators of diatoms, feed on certain diatom diets, they produce abnormal eggs that either fail\\u000a to

Adrianna Ianora; Antonio Miralto

2010-01-01

312

Role of delamination and interlaminar fatigue in the failure of laminates with ply dropoffs  

E-print Network

Analytical and experimental investigations were conducted on laminates with ply dropoffs to better understand the interlaminar stress field and delamination/damage characteristics in such laminates, as well as the relationship ...

Shim, Dong Jin, 1972-

2002-01-01

313

Response of grooved composite laminates to out-of-plane contact loading via numerical models  

E-print Network

The response of grooved composite laminates to out-of-plane contact loading is examined using numerical modeling through the consideration of contact pressure and stresses within the laminate, with particular focus on the ...

Iqbal, Jaffar S

2011-01-01

314

77 FR 61025 - Certain Prepregs, Laminates, and Finished Circuit Boards: Notice of Institution of Formal...  

Federal Register 2010, 2011, 2012, 2013

...337-TA-659] Certain Prepregs, Laminates, and Finished Circuit Boards: Notice of Institution of Formal Enforcement Proceeding...importation of certain prepregs, laminates, and finished circuit boards that infringe certain claims of United States...

2012-10-05

315

A mathematical model for the stressed state analysis of cylindrical laminated-composite pressure vessels  

NASA Astrophysics Data System (ADS)

An algorithm and a computer program have been developed for calculating the strength of pressure vessels made of laminated composites. Numerical results for pressure vessels of Kevlar 49 laminates are compared with experimental data in the literature.

Bak, Roman; Matyja, Tomasz

316

The effect of temperature on the bending of laminated glass beams  

E-print Network

Laminated glass is comprised of multiple plates of glass bonded together with polymorphous interlayers. The interest in the use of architectural laminated glass in the construction industry has increased due to its possible advantages over...

Edel, Matthew Thomas

2012-06-07

317

Plug repairs of marine glass fiber / vinyl ester laminates subjected to uniaxial tension  

E-print Network

Glass fiber/vinyl ester composite laminates are currently being used and proposed for the hulls, bulkheads, and superstructures of large ships. This thesis examines the effectiveness of the repair of such laminates using ...

Michelis, Alexandros

2009-01-01

318

How-to-Do-It: Diatoms: The Ignored Alga in High School Biology.  

ERIC Educational Resources Information Center

Provides historical background, descriptions, uses and basis for identification of diatoms. Explains collection, dry-mount cleaning, and preparation procedures of the algae. Cites additional resources. (RT)

Hungerford, James J.

1988-01-01

319

Hierarchical and size dependent mechanical properties of silica and silicon nanostructures inspired by diatom algae  

E-print Network

Biology implements fundamental principles that allow for attractive mechanical properties, as observed in biomineralized structures. For example, diatom algae contain nanoporous hierarchical silicified shells that provide ...

Garca, Andre Phillip

2010-01-01

320

Grazing-induced changes in cell wall silicification in a marine diatom.  

PubMed

In aquatic environments, diatoms (Bacillariophyceae) constitute a central group of microalgae which contribute to about 40% of the oceanic primary production. Diatoms have an absolute requirement for silicon to build-up their silicified cell wall in the form of two shells (the frustule). To date, changes in diatom cell wall silicification have been only studied in response to changes in the growth environment, with consistent increase in diatom silica content when specific growth rates decrease under nutrient or light limitations. Here, we report the first evidence for grazing-induced changes in cell wall silicification in a marine diatom. Cells grown in preconditioned media that had contained both diatoms and herbivores are significantly more silicified than diatoms grown in media that have contained diatoms alone or starved herbivores. These observations suggest that grazing-induced increase in cell wall silicification can be viewed as an adaptive reaction in habitats with variable grazing pressure, and demonstrate that silicification in diatoms is not only a constitutive mechanical protection for the cell, but also a phenotypically plastic trait modulated by grazing. In turn, our results corroborate the idea that plant-herbivore interactions, beyond grazing sensu stricto, contribute to drive ecosystem structure and biogeochemical cycles in the ocean. PMID:17081802

Pondaven, Philippe; Gallinari, Morgane; Chollet, Sophie; Bucciarelli, Eva; Sarthou, Graldine; Schultes, Sabine; Jean, Frdric

2007-01-01

321

Development of a design procedure for architectural laminated glass window units  

E-print Network

. 23 , 24 . 26 . 31 . 46 . 53 . . 56 56 59 , 60 . 60 LAMINATED GLASS FAILURE PREDICTION MODEL. . . . . . 65 Annealed Glass Failure Prediction Model. . . . . 65 Laminated Glass Failure Prediction Model. . . . 70 Page VI DEVELOPING A... models. These theoretical laminated glass performance models are examined in Chapter IV. The following step in this process was to combine the selected laminated glass performance model with the glass failure prediction model (GFPN) (Beason 1980...

Dice, Jeffrey Aaron

1992-01-01

322

Stacking-sequence optimization using fractal branch-and-bound method for unsymmetrical laminates  

Microsoft Academic Search

The fractal branch-and-bound method has been developed by the authors for stacking-sequence optimizations of symmetric and balanced composite laminates comprise of two in-plane and two out-of-plane lamination parameters. Cylindrical structures such as tanks or pipes, however, are usually made from balanced laminates. In the present study, therefore, we focus on the stacking-sequence optimizations of unsymmetrical composite laminates. In the unsymmetrical

Ryosuke Matsuzaki; Akira Todoroki

2007-01-01

323

Origins and paleoceanographic significance of laminated muds from the Ulleung Basin, East Sea (Sea of Japan)  

Microsoft Academic Search

A detailed facies analysis of long piston-core sediments from the Ulleung Basin reveals four mud facies: laminated mud, crudely laminated mud, bioturbated mud, and homogenous mud. The laminated and homogeneous muds were most likely deposited from turbidity currents, whereas the bioturbated and crudely laminated muds were formed by hemipelagic\\/pelagic sedimentation under well-oxygenated and poorly oxygenated bottom-water conditions, respectively. A detailed

J. J Bahk; S. K Chough; S. J Han

2000-01-01

324

Snap-Through of Unsymmetric Laminates Using Piezocomposite Actuators  

NASA Technical Reports Server (NTRS)

The paper discusses the concept of using a piezoceramic actuator bonded to one side of a two-layer unsymmetric cross-ply [0/90]T laminate to provide the moments necessary to snap the laminate from one stable equilibrium shape to another. This concept could be applied to the morphing of structures. A model of this concept, which is based on the Rayleigh-Ritz technique and the use of energy and variational methods, is developed. The experimental phase of the study is discussed, including the measurement of the voltage level needed to snap the laminate. The voltage measurements and shapes are compared with predictions of the models and the agreement between measurements and the predictions are reasonable, both qualitatively and quantitatively. Suggestions for future activities are presented.

Schultz, Marc R.; Hyer, Michael W.; Williams, R. Brett; Wilkie, W. Keats; Inman, Daniel J.

2006-01-01

325

Low-temperature mechanical properties of glass/epoxy laminates  

SciTech Connect

Selected mechanical properties of glass/epoxy laminate candidates for use in the electrical turn and ground insulation of the ITER Central solenoid (CS) modules were measured. Short-beam shear and flexural tests have been conducted on various E-glass cloth weaves/epoxy laminates at 295 and 77 K. Types of glass weave include 1581, 7500, 7781, and 38050, which represent both satin and plain weaves. The epoxy, planned for use for vacuum-pressure impregnation of the CS module, consists of an anhydride-cured bisphenol F resin system. Inter-laminar shear strength, flexural elastic modulus, and flexural strength have been measured. The data indicate that these properties are dependent on the volume percent of glass. Short-beam shear strength was measured as a function of the span-to-thickness ratio for all laminates at 77 K. Comprehensive fractography was conducted to obtain the failure mode of each short-beam shear test sample.

Reed, R. P. [Cryogenic Materials, Inc., Boulder, CO 80305 (United States); Madhukar, M.; Thaicharoenporn, B. [Magnet Development Laboratory, Knoxville, TN 37996 (United States); Martovetsky, N. N. [US-ITER Project, Oak Ridge National Laboratory, Oak Ridge, TN 37830 (United States)

2014-01-27

326

Proteins that associate with lamins: Many faces, many functions  

SciTech Connect

Lamin-associated polypeptides (LAPs) comprise inner nuclear membrane proteins tightly associated with the peripheral lamin scaffold as well as proteins forming stable complexes with lamins in the nucleoplasm. The involvement of LAPs in a wide range of human diseases may be linked to an equally bewildering range of their functions, including sterol reduction, histone modification, transcriptional repression, and Smad- and {beta}-catenin signaling. Many LAPs are likely to be at the center of large multi-protein complexes, components of which may dictate their functions, and a few LAPs have defined enzymatic activities. Here we discuss the definition of LAPs, review their many binding partners, elaborate their functions in nuclear architecture, chromatin organization, gene expression and signaling, and describe what is currently known about their links to human disease.

Schirmer, Eric C. [Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR (United Kingdom)]. E-mail: e.schirmer@ed.ac.uk; Foisner, Roland [Max F. Perutz Laboratories, Department of Medical Biochemistry, Medical University of Vienna, Dr. Bohr-Gasse 9, A-1030 Vienna (Austria)]. E-mail: roland.foisner@meduniwien.ac.at

2007-06-10

327

Multiscale modeling of damage in multidirectional composite laminates  

NASA Astrophysics Data System (ADS)

The problem of damage accumulation in laminated composite materials has received much attention due to their widespread application in the aerospace, automotive, civil, and sports industries. In the aerospace industry, composites are used to make light weight and efficient structural components. In the Boeing 787, for example, more than 50% of the structure is made of composite materials. Although there have been significant developments in analyzing cross-ply laminates, none of the present approaches provides reasonable predictions for multidirectional laminates in which intralaminar cracks may form in multiple orientations. Nevertheless, the prediction of damage accumulation and its effect on structural performance is a very difficult problem due to complexity of the cracking processes. This study presents a synergistic damage mechanics (SDM) methodology to analyze damage behavior in multidirectional composite laminates with intralaminar cracks in plies of multiple orientations. SDM combines the strengths of micro-damage mechanics (MDM) and continuum damage mechanics (CDM) in predicting the stiffness degradation due to these cracks. The micromechanics is performed on a representative unit cell using a three-dimensional finite element analysis to calculate the crack opening displacement accounting for the influence of the surrounding plies, the so-called constraint effect. This information is then incorporated in the CDM formulation dealing with laminates containing cracks in different ply orientations through a 'constraint parameter'. Following CDM, a separate damage mode is defined for each type of crack and the expressions for engineering moduli of the damaged laminate are then derived in terms of crack density and the constraint parameter. The SDM methodology is implemented for [0 m/+/- thetan/0 m/2]s laminates containing cracks in +/-theta plies. It is then extended to [0m /+/- thetan/90 r]s and [0m/90 r/+/- thetan] s laminates with cracks additionally in the 90-plies. The predictions agree well with published experimental data as well as independent FE computations. Limited parametric studies are performed to show usability of SDM for more general laminates. To predict the initiation and growth of intralaminar cracks, an energy based model is proposed in which these cracks initiate and multiply when the work required to form new set of cracks exceeds a laminate dependent critical energy release rate. The approach requires determination of average crack opening and sliding displacements at varying crack spacing. This task is performed through a suitable 3-D FE analysis. In case of off-axis ply cracking, a mixed mode fracture criterion is utilized, where the critical energy release rates in normal and shear modes are determined by fitting the damage model with the experimental data for a reference laminate. The predictions from the model for [0/+/-theta4/01/2]s and [0/90/?45]s laminates show remarkable agreement with the experimental results. The methodology and the results covered in this dissertation will be of interest to mechanics of materials researchers as well as to engineers in industry where composite materials for structural applications are of interest.

Singh, Chandra Veer

328

Nonlinear response of resin matrix laminates using endochronic theory  

NASA Technical Reports Server (NTRS)

The nonlinear response of laminated, resin matrix fibrous composites is modeled using orthotropic endochronic theory. The theory is formulated in terms of elastic constants and endochronic parameters characterizing the linear and nonlinear response, respectively, of unidirectional composites. All constants and parameters can be determined from normal (tension and/or compression) and shear tests on unidirectional and off-axis specimens. The nonlinear constitutive response relations for the unidirectional lamina are presented and the procedure for determining constants and parameters from test is described. The results are then used to predict the nonlinear response of unidirectional laminae and angle-ply laminates. Comparison between theory and experiment for compression loading of AS4/3502 graphite-epoxy, angle-ply laminates shows excellent correlation.

Mathison, S. R.; Pindera, M. J.; Herakovich, C. T.

1991-01-01

329

Thermal modeling of carbon-epoxy laminates in fire environments.  

SciTech Connect

A thermal model is developed for the response of carbon-epoxy composite laminates in fire environments. The model is based on a porous media description that includes the effects of gas transport within the laminate along with swelling. Model comparisons are conducted against the data from Quintere et al. Simulations are conducted for both coupon level and intermediate scale one-sided heating tests. Comparisons of the heat release rate (HRR) as well as the final products (mass fractions, volume percentages, porosity, etc.) are conducted. Overall, the agreement between available the data and model is excellent considering the simplified approximations to account for flame heat flux. A sensitivity study using a newly developed swelling model shows the importance of accounting for laminate expansion for the prediction of burnout. Excellent agreement is observed between the model and data of the final product composition that includes porosity, mass fractions and volume expansion ratio.

McGurn, Matthew T. (University at Buffalo, the State University of New York (SUNY Buffalo), Buffalo, NY); DesJardin, Paul Edward (University at Buffalo, the State University of New York (SUNY Buffalo), Buffalo, NY); Dodd, Amanda B.

2010-10-01

330

Compression and compression fatigue testing of composite laminates  

NASA Technical Reports Server (NTRS)

The effects of moisture and temperature on the fatigue and fracture response of composite laminates under compression loads were investigated. The structural laminates studied were an intermediate stiffness graphite-epoxy composite (a typical angle ply laimna liminate had a typical fan blade laminate). Full and half penetration slits and impact delaminations were the defects examined. Results are presented which show the effects of moisture on the fracture and fatigue strength at room temperature, 394 K (250 F), and 422 K (300 F). Static tests results show the effects of defect size and type on the compression-fracture strength under moisture and thermal environments. The cyclic tests results compare the fatigue lives and residual compression strength under compression only and under tension-compression fatigue loading.

Porter, T. R.

1982-01-01

331

Mechanisms of compressive failure in woven composites and stitched laminates  

NASA Technical Reports Server (NTRS)

Stitched laminates and angle interlock woven composites have been studied in uniaxial, in-plane, monotonic compression. Failure mechanisms have been found to depend strongly on both the reinforcement architecture and the degree of constraint imposed by the loading grips. Stitched laminates show higher compressive strength, but are brittle, possessing no load bearing capacity beyond the strain for peak load. Post-mortem inspection shows a localized shear band of buckled and broken fibers, which is evidently the product of an unstably propagating kink band. Similar shear bands are found in the woven composites if the constraint of lateral displacements is weak; but, under strong constraint, damage is not localized but distributed throughout the gauge section. While the woven composites tested are weaker than the stitched laminates, they continue to bear significant loads to compressive strains of approx. 15 percent, even when most damage is confined to a shear band.

Cox, B. N.; Dadkhah, M. S.; Inman, R. V.; Morris, W. L.; Schroeder, S.

1992-01-01

332

Influence of mechanical load bias on converse magnetoelectric laminate composites  

NASA Astrophysics Data System (ADS)

A piezofiber/Metglas (PFM) magnetoelectric (ME) laminate has been integrated into a graphite epoxy composite (GEC) to study the converse ME effect (CME). Experimental data on a PFM/GEC subjected to both a dc magnetic field bias and a dc mechanical load bias while exciting it with an ac electric driving voltage are presented. Results of these tests indicate that both the mechanical load and the dc magnetic field strongly influence the CME response. Furthermore, an optimum mechanical load exists to maximize the CME coefficient, which should also be present in standalone ME laminates. These results reveal that the CME coefficient can be further increased with a proper mechanical load bias. Therefore, the selection of an appropriate mechanical preload as well as dc magnetic bias will maximize the CME response and sensitivity in ME laminates as well as integrated structural systems.

Wu, Tao; Emmons, Michael; Chung, Tien-Kan; Sorge, Jian; Carman, Gregory P.

2010-05-01

333

Low-temperature mechanical properties of glass/epoxy laminates  

NASA Astrophysics Data System (ADS)

Selected mechanical properties of glass/epoxy laminate candidates for use in the electrical turn and ground insulation of the ITER Central solenoid (CS) modules were measured. Short-beam shear and flexural tests have been conducted on various E-glass cloth weaves/epoxy laminates at 295 and 77 K. Types of glass weave include 1581, 7500, 7781, and 38050, which represent both satin and plain weaves. The epoxy, planned for use for vacuum-pressure impregnation of the CS module, consists of an anhydride-cured bisphenol F resin system. Inter-laminar shear strength, flexural elastic modulus, and flexural strength have been measured. The data indicate that these properties are dependent on the volume percent of glass. Short-beam shear strength was measured as a function of the span-to-thickness ratio for all laminates at 77 K. Comprehensive fractography was conducted to obtain the failure mode of each short-beam shear test sample.

Reed, R. P.; Madhukar, M.; Thaicharoenporn, B.; Martovetsky, N. N.

2014-01-01

334

Fracture behavior of unidirectional boron/aluminum composite laminates  

NASA Technical Reports Server (NTRS)

An experimental investigation of the fracture behavior of unidirectional boron/aluminum composite laminates was conducted in order to verify the results of mathematical models. These models predict the fiber stresses and displacements and the amount of damage growth in a center-notched lamina as a function of the applied remote stress and the matrix and fiber material properties. A brittle lacquer coating was used to detect the yielding in the matrix while X-ray techniques were used to determine the number of broken fibers in the laminate. The notched strengths and the amounts of damage found in the specimens agreed well with those predicted by the models. It was shown that for thin laminates the amount of damage and the fiber displacements do not depend strongly on the number of plies for a given notch width.

Jones, F. W.; Goree, J. G.

1983-01-01

335

Elastic Buckling of Laminated Plates Under Varying Axial Stresses  

NASA Technical Reports Server (NTRS)

The elastic buckling load of simply supported rectangular composite plates subjected to a second degree parabolic variation of axial stresses in the longitudinal direction is calculated using analytical methods. The variation of axial stresses is equilibrated by nonuniform shear stresses along the plate edges and transverse normal stresses. Numerical results are reported for three different cases: (1) orthotropic plates, (2) symmetrically laminated plates with multiple generally orthotropic layers exhibiting coupling between normal moments and twist, and twisting moment and normal curvatures, and (3) unsymmetrically laminated plates. Rayleigh-Ritz method is used to calculate the buckling load. An approximate solution using "reduced bending stiffness" is adopted for unsymmetrically laminated plates. The influence of the aspect ratio is examined, and the results are compared with plates subjected to uniform axial stresses.

Badir, A.; Hu, H.

1998-01-01

336

A New Approach to the Architecture of Diatomic Molecules  

NASA Astrophysics Data System (ADS)

In our previous work, we established that, in an atomic or molecular wave-like description embodying a potential energy term made of Coulomb Potentials, if the mass M of the object (or different masses the object involves) is multiplied by the hypothetical number ?, then the size of space R in which this object is installed, shrinks as much, and the total energy E of the object, is increased as much [1]. This occurance yields at once the quantum mechanical invariance of the quantity EMR^2; furthermore this quantity happens to be girdled to h^2, so that we end up with the relationship EMR^2 h^2 [1]. Note that this is in no way a dimension analysis. Anyhow, the occurance we disclose would not work, if the wave-like description embodies other potentials than Coulomb Potentials, though of course, there still would be no problem in regards to a dimension analysis. Herein, we consider the above relationship, together with the equation related to the electronic motion of the molecule (for fixed nuclei), obtained through the Born and Oppenheimer Approximation [2], when this is applied to the Schrodinger description of a diatomic molecule. Our approach thus leads to an essential relationship for the vibrational period of the diatomic molecule in hand, namely T=4? ^2/[h(n_in_j)^1/2][gM_redm_e]^1/2R^2, where M_red is the reduced mass of the nuclei of the diatomic molecule of concern, me the mass of the electron, and g, a dimensionless coefficient; ni and nj (essentially on the basis of the study of the hydrogen molecule vibrational excited electronic data together with the study of the ground state vibrational data related to alkali hydrides and alkali molecules), are disclosed to be the numbers identifying the rows of The Periodic Table of The Elements, to which the atoms making up the molecule belong; this finding is further checked throughout the entire body of diatomic molecules. From the above relationship, it appears immediately that g, necessesarily related to the electronic bond structure of the molecule, should remain practically constant for chemically alike bonds. This allows us to draw the architectural layout of diatomic molecules since the above relationship reduces to T [M_red]^1/2R^2, for a family of chemicaly alike molecules, and further to T R^2, for different electronic states of a given molecule. This latter is a relationship known since 1925 [3], but never disclosed so far. Henceforth T versus [M_red]^1/2R^2 for such molecules, should exhibit a linear behaviour, the slope of which shall furnish g (for the chemical family in consideration). Various applications, in excellent agreement with our finding are already drawn [4], though through a totally different approach, and a publication that embodies a complete set will follow. The related g's vary between 0.17 and 0.74. Our approach is applied successfully to triatomic and poliatomic molecules, since each bond can be considered to work like a diatomic molecule bond, even though now more complex elements than atoms make up the bond [5]. REFERENCES 1. T. Yarman, Invariances Based on Mass And Charge Variation, Manufactured by Wave Mechanics, Making up The Rules of Universal Matter Architecture, Paper Accepted for Publication in Chimica Acta Turcica (23 September 1998). 2. Born and Oppenheimer, Ann. Physik, 84, 457 (1927). 3. Birge, Physic Rev. 25, 240 (1925). 4. T. Yarman, Chimica Acta Turcica, Vol 26, No 3, 1999. 5. N. Zaim, An Approach to The Systematization of Diatomic And Three Atomic Molecules, Ph. D. Thesis Directed by T. Yarman, Trakya University (Edirne, Turkey), September 2000.

Yarman, Tolga

2001-05-01

337

Fatigue reliability evaluation for composite laminates via a direct numerical integration technique  

Microsoft Academic Search

A direct numerical integration technique for evaluating fatigue reliability of composite laminates under varying stress amplitudes is presented. A number of cumulative damage models are adopted to construct the limit state equation for the laminates in the reliability analysis. Existing fatigue life distributions of composite laminates under cyclic stresses of constant amplitude are used in the reliability assessment of the

T. Y. Kam; K. H. Chu; S. Y. Tsai

1998-01-01

338

Nuclear lamins and peripheral nuclear antigens during fertilization and embryogenesis in mice and sea urchins  

NASA Technical Reports Server (NTRS)

Nuclear structural changes during fertilization and embryogenesis in mice and sea urchins are traced using four antibodies. The oocytes from virgin female mice, morulae and blastocytes from mated females, and gametes from the sea urchin Lytechnius variegatis are studied using mouse monoclonal antibodies to nuclear lamin A/C, monoclonal antibody to P1, human autoimmune antibodies to lamin A/C, and to lamin B. The mouse fertilization data reveal no lamins on the oocyte; however, lamins are present on the pronuclei, and chromosomes are found on the oocytes and pronuclei. It is detected that on the sea urchin sperm the lamins are reduced to acrosomal and centriolar fossae and peripheral antigens are around the sperm nucleus. The mouse sperm bind lamin antibodies regionally and do not contain antigens. Lamins and antigens are observed on both pronuclei and chromosomes during sea urchin fertilization. Mouse embryogenesis reveals that lamin A/C is not recognized at morula and blastocyst stages; however, lamin B stains are retained. In sea urchin embryogenesis lamin recognition is lost at the blastrula, gastrula, and plutei stages. It is noted that nuclear lamins lost during spermatogenesis are restored at fertilization and peripheral antigens are associated with the surface of chromosomes during meiosis and mitosis and with the periphery of the pronuclei and nuclei during interphase.

Schatten, G.; Schatten, H.; Simerly, C.; Maul, G. G.; Chaly, N.

1985-01-01

339

Effects of Glass Fabric and Laminate Construction on the Fatigue of Resin Infused Blade Materials  

E-print Network

Effects of Glass Fabric and Laminate Construction on the Fatigue of Resin Infused Blade Materials are presented for infusion molded laminates, providing a comparison of several commercial E-glass reinforcing reinforcing fabrics used in blade infusion processes. II. Background The fatigue behavior of laminates based

340

Calculation of eddy currents and associated losses in electrical steel laminations  

Microsoft Academic Search

Starting from the well known analytical formula for the eddy current losses in electrical steel laminations, saturation and edge effects are studied by means of 1D and 2D finite element models of a single lamination. A novel method for directly including the laminated core energy dissipation in a time stepped 2D model of a complete (rotating) machine is proposed. By

J. Gyselinck; L. Vandevelde; J. Melkebeek; P. Dular; F. Henrotte; W. Legros

1999-01-01

341

Torsion of Open and Closed Thin-Walled Laminated Composite Sections  

Microsoft Academic Search

Vlasovs theory is expanded to perform the linear analysis of open and closed sections made of general laminated composites. Following the guidelines of Mechanics of Laminated Beams, the transverse shear deformations are included in the formulation. To overcome the overestimation of stiffness by the often assumption of negligible tangential stress, the laminate resultant force and moment are instead set to

Hani A. Salim; Julio F. Davalos

2005-01-01

342

Nuclear lamins and peripheral nuclear antigens during fertilization and embryogenesis in mice and sea urchins  

SciTech Connect

Nuclear structural changes during fertilization and embryogenesis in mice and sea urchins are traced using four antibodies. The oocytes from virgin female mice, morulae and blastocytes from mated females, and gametes from the sea urchin Lytechnius variegatis are studied using mouse monoclonal antibodies to nuclear lamin A/C, monoclonal antibody to P1, human autoimmune antibodies to lamin A/C, and to lamin B. The mouse fertilization data reveal no lamins on the oocyte; however, lamins are present on the pronuclei, and chromosomes are found on the oocytes and pronuclei. It is detected that on the sea urchin sperm the lamins are reduced to acrosomal and centriolar fossae and peripheral antigens are around the sperm nucleus. The mouse sperm bind lamin antibodies regionally and do not contain antigens. Lamins and antigens are observed on both pronuclei and chromosomes during sea urchin fertilization. Mouse embryogenesis reveals that lamin A/C is not recognized at morula and blastocyst stages; however, lamin B stains are retained. In sea urchin embryogenesis lamin recognition is lost at the blastrula, gastrula, and plutei stages. It is noted that nuclear lamins lost during spermatogenesis are restored at fertilization and peripheral antigens are associated with the surface of chromosomes during meiosis and mitosis and with the periphery of the pronuclei and nuclei during interphase. 32 references.

Schatten, G.; Schatten, H.; Simerly, C.; Maul, G.G.; Chaly, N.

1985-07-01

343

Dynamic changes in circulating leukocytes during the induction of equine laminitis with black walnut extract  

Microsoft Academic Search

Administration of black walnut heartwood extract (BWHE) via nasogastric tube induces acute laminitis in horses. However, the processes responsible for the development of laminitis, including laminitis induced with BWHE, remain unclear. The results of recent studies indicate that administration of BWHE initiates an inflammatory response in the laminar tissues and that this response may be due to extravasation of activated

David J. Hurley; Robert J. Parks; Adrian J. Reber; Douglas C. Donovan; Tatsuyuki Okinaga; Michel L. Vandenplas; John F. Peroni; James N. Moore

2006-01-01

344

Damage detection of CFRP laminates using electrical resistance measurement and neural network  

Microsoft Academic Search

As carbon fibers are electrical conductors, the measurement of the electrical resistance appears to be a valuable technique for the in situ detection of various types of damage in carbon fiber reinforced polymers (CFRP) laminates. In such cases, carbon fibers are both the reinforcement and the sensor to detect damage in CFRP laminates. The damage-detecting method of CFRP laminates by

Dae-Cheol Seo; Jung-Ju Lee

1999-01-01

345

COMPRESSION STRENGTH OF CARBON FIBER LAMINATES CONTAINING FLAWS WITH FIBER WAVINESS  

E-print Network

1 COMPRESSION STRENGTH OF CARBON FIBER LAMINATES CONTAINING FLAWS WITH FIBER WAVINESS Darrell P, Montana, 59717 ABSTRACT Recent studies of carbon fiber and carbon/glass hybrid laminates have reported in This Study. Figure 4. In-Plane Waviness in a Single-Ply Laminate of Fortafil 652 Carbon Fiber/Epoxy Processed

346

Mechanics and finite elements for the damped dynamic characteristics of curvilinear laminates and composite shell structures  

Microsoft Academic Search

Integrated mechanics and a finite element method are presented for predicting the damping of doubly curved laminates and laminated shell composite structures. Damping mechanics are formulated in curvilinear co-ordinates from ply to structural level and the structural modal loss factors are calculated using the energy dissipation method. The modelling of damping at the laminate level is based on first order

T. S. Plagianakos; D. A. Saravanos

2003-01-01

347

Reliability analysis of laminated CMC components through shell subelement techniques  

NASA Technical Reports Server (NTRS)

An updated version of the integrated design program C/CARES (composite ceramic analysis and reliability evaluation of structures) was developed for the reliability evaluation of CMC laminated shell components. The algorithm is now split in two modules: a finite-element data interface program and a reliability evaluation algorithm. More flexibility is achieved, allowing for easy implementation with various finite-element programs. The new interface program from the finite-element code MARC also includes the option of using hybrid laminates and allows for variations in temperature fields throughout the component.

Starlinger, A.; Duffy, S. F.; Gyekenyesi, J. P.

1992-01-01

348

Complex response of a bistable laminated plate: Multiscale entropy analysis  

NASA Astrophysics Data System (ADS)

The use of bistable laminates is a potential approach to realize more broadband piezoelectric based energy harvesting systems. Based on the experimental time series of a bistable laminate plate we have examined its dynamic response. The system was subjected to harmonic excitations showing the existence of single well and snap-through vibrations of periodic and chaotic character. To identify the dynamics of the system response we examine the frequency spectrum, phase portraits and multi-scaled entropy. It is observed that the composite multiscale entropy analysis can be used to identify complexity within the dynamic response successfully.

Borowiec, M.; Rysak, A.; Betts, D. N.; Bowen, C. R.; Kim, H. A.; Litak, G.

2014-10-01

349

Modeling localized properties of E-rated laminating lumber  

E-print Network

Committee: Dr. Donald A. Bender The objective of this research was to develop stochastic models for localized modulus of elasticity (MOE) and tensile strength (T) of E-rated 2" x 6" Douglas-fir laminating lumber. The E-rated grades in the study were C14..., 2. 3 1/6, 2. 3 1/3, 2. 0 1/6, 2. 0 1/3, and 1. 7 1/4. L2 and L3 visual grades were also included. Localized property data are needed as input f' or stochastic Monte Carlo simulation models of glued-laminated (glulam) beam strength. Results...

Richburg, Brent Allen

2012-06-07

350

When Lamins Go Bad: Nuclear Structure and Disease  

PubMed Central

When mutations in nuclear lamins were first identified in skeletal and cardiac muscle diseases, the molecular events underlying pathogenesis were mere points of speculation. As more and more unrelated diseases were linked to lamins and other nuclear envelope proteins, nuclear structure and disease became an increasingly prominent research focus. Today, the disease mechanisms remain unresolved, but incredible progress has occurred. Nuclear envelope dysfunction is not only associated with altered nuclear activity, but also impaired structural dynamics and aberrant cell signaling. Building on these findings, small molecules are being discovered in animal models that may become effective therapeutic agents. PMID:23498943

Schreiber, Katherine H.; Kennedy, Brian K.

2013-01-01

351

Metal Matrix Laminate Tailoring (MMLT) code: User's manual  

NASA Technical Reports Server (NTRS)

The User's Manual for the Metal Matrix Laminate Tailoring (MMLT) program is presented. The code is capable of tailoring the fabrication process, constituent characteristics, and laminate parameters (individually or concurrently) for a wide variety of metal matrix composite (MMC) materials, to improve the performance and identify trends or behavior of MMC's under different thermo-mechanical loading conditions. This document is meant to serve as a guide in the use of the MMLT code. Detailed explanations of the composite mechanics and tailoring analysis are beyond the scope of this document, and may be found in the references. MMLT was developed by the Structural Mechanics Branch at NASA Lewis Research Center (LeRC).

Murthy, P. L. N.; Morel, M. R.; Saravanos, D. A.

1993-01-01

352

Diatom productivity in the eastern Gulf of Guinea during the last 20,000 years  

NASA Astrophysics Data System (ADS)

Biogenic silica and diatom accumulation rates are used to document siliceous productivity in the Gulf of Guinea in relation to oceanographic and climatic changes. Diatom assemblages were identified in core GeoB4905-4, retrieved off the Sanaga River, to congruently track oceanographic changes in the eastern Gulf of Guinea, precipitation and wind regime changes in equatorial Africa. Diatom productivity was greatest during the 12000-11000 and 9000-6000 calendar years BP periods (cal yr BP) when sea-surface temperature were warmer (Weldeab et al., 2007). At the assemblage level, greater diatom productivity periods demonstrated higher relative abundances of sub-tropical and freshwater diatoms and lower relative abundances of meroplanktonic diatoms and brackish water diatoms. Windblown diatoms were also absent during these periods. Diatom productivity was lowest during the 20000-12000 and 5000-0 cal yr BP periods when relative abundances of sub-tropical and freshwater diatoms decreased and abundances of meroplanktonic and brackish water diatoms increased. Windblown diatoms appeared solely during these periods. These results indicate that diatom productivity and oceanography in the eastern part of the Gulf of Guinea (governed by the Guinea Current in surface and the Equatorial Under-Current in sub-surface) are decoupled. Similarly, the wind regime can not explain the Holocene pattern of diatom productivity recorded here. Siliceous productivity is rather controlled by riverine input by the Sanaga and Niger rivers and therefore precipitation over western/central equatorial Africa. More precisely, diatom accumulation rates and assemblages argue for enhanced precipitation during the Early and Mid-Holocene periods and drier conditions during the last glacial, the Younger Dryas and the Late Holocene in agreement with studies of lake levels in eastern equatorial Africa (Gasse, 2000; Gasse et al., 2009) and geochemical data from the Gulf of Guinea (Schefuss et al., 2005; Weldeab et al., 2005; Weijers et al., 2009). Late glacial and Holocene changes in precipitation and wind activity may result from the combined influence of the Asian monsoon and the Inter-Tropical Convergence Zone (ITCZ) latitudinal migration. Gasse, 2000, Quaternary Science Reviews 19, 189-211. Gasse et al., 2009, Quaternary Science Reviews 27, 2316-2340. Schefuss et al., 2005, Nature 437, 1003-1006. Weldeab et al., 2005, Geology 33(12), doi: 10.1130/G21874. Weldeab et al., 2007, G-Cubed 8(5), Q05P22, doi:10.1029/2006GC001360. Weijers et al., 2009, Geochimica and Cosmochimica Acta 73, 119-132.

Crosta, Xavier; Schneider, Ralph; Weldeab, Syee; Mller, Peter

2010-05-01

353

Settling fluxes of diatoms to the interior of the Antarctic circumpolar current along 170 W  

NASA Astrophysics Data System (ADS)

An array of four sediment trap moorings recorded the particulate flux across the Antarctic Circumpolar Current (ACC) at 170 W, between November 1996 and January 1998, as part of the US JGOFS-Antarctic Environment and Southern Ocean Process Study (AESOPS) program. The trap locations represent sampling within the Polar Frontal Zone, the Antarctic Polar Front, the Antarctic Zone and the Southern Antarctic Zone. Here we report observations from 1000 m below the sea-surface compared to seafloor and surface water distributions. Sub-sample splits from each trap were obtained and total diatom flux and species composition were determined. The diatom fluxes were quantified using both a dilution and a spike' method to allow for the rapid repeatability of measurements. Diatom flux was found to be highly seasonal across the ACC particularly at higher latitudes. Marine snow aggregates of intact diatom cells and chains were the major components of the biogenic flux. Siliceous particle size was noted to decrease with increasing latitude, which could be aligned with a shift of the diatom assemblage to small-size species/sea-ice affiliated species. A double-structured' diatom flux was recorded at the location of the Antarctic Polar Front trap, with a shift in the diatom assemblage from larger to smaller diatoms in the second flux episode. The sediment trap assemblage shows deviations from the surface water assemblage, while surface sediment samples indicate that significant dissolution occurs after 1000 m and at the sediment-water interface. Estimation of diatom biovolumes across the ACC shows that large diatoms have the potential to greatly impact biogenic fluxes to the ocean interior despite their low fluxes. Small species of the genus Fragilariopsis could potentially export as much Corg as Fragilariopsis kerguelensis near the retreating ice edge. However, their low abundance in the surface sediments also suggests that these diatoms are a shallow export species.

Grigorov, Ivo; Rigual-Hernandez, Andrs S.; Honjo, Susumu; Kemp, Alan E. S.; Armand, Leanne K.

2014-11-01

354

Evolution and metabolic significance of the urea cycle in photosynthetic diatoms.  

PubMed

Diatoms dominate the biomass of phytoplankton in nutrient-rich conditions and form the basis of some of the world's most productive marine food webs. The diatom nuclear genome contains genes with bacterial and plastid origins as well as genes of the secondary endosymbiotic host (the exosymbiont), yet little is known about the relative contribution of each gene group to diatom metabolism. Here we show that the exosymbiont-derived ornithine-urea cycle, which is similar to that of metazoans but is absent in green algae and plants, facilitates rapid recovery from prolonged nitrogen limitation. RNA-interference-mediated knockdown of a mitochondrial carbamoyl phosphate synthase impairs the response of nitrogen-limited diatoms to nitrogen addition. Metabolomic analyses indicate that intermediates in the ornithine-urea cycle are particularly depleted and that both the tricarboxylic acid cycle and the glutamine synthetase/glutamate synthase cycles are linked directly with the ornithine-urea cycle. Several other depleted metabolites are generated from ornithine-urea cycle intermediates by the products of genes laterally acquired from bacteria. This metabolic coupling of bacterial- and exosymbiont-derived proteins seems to be fundamental to diatom physiology because the compounds affected include the major diatom osmolyte proline and the precursors for long-chain polyamines required for silica precipitation during cell wall formation. So far, the ornithine-urea cycle is only known for its essential role in the removal of fixed nitrogen in metazoans. In diatoms, this cycle serves as a distribution and repackaging hub for inorganic carbon and nitrogen and contributes significantly to the metabolic response of diatoms to episodic nitrogen availability. The diatom ornithine-urea cycle therefore represents a key pathway for anaplerotic carbon fixation into nitrogenous compounds that are essential for diatom growth and for the contribution of diatoms to marine productivity. PMID:21562560

Allen, Andrew E; Dupont, Christopher L; Obornk, Miroslav; Hork, Ale; Nunes-Nesi, Adriano; McCrow, John P; Zheng, Hong; Johnson, Daniel A; Hu, Hanhua; Fernie, Alisdair R; Bowler, Chris

2011-05-12

355

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

EPA Science Inventory

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

356

A Micromechanics-Based Damage Model For The Strength Prediction of Composite Laminates  

NASA Technical Reports Server (NTRS)

A new damage model based on a micromechanical analysis of cracked [+/-0deg/90deg(sub n)]s laminates subjected to multiaxial loads is proposed. The model predicts the onset and accumulation of transverse matrix cracks in uniformly stressed laminates, the effect of matrix cracks on the stiffness of the laminate, as well as the ultimate failure of the laminate. The model also accounts for the effect of the ply thickness on the ply strength. Predictions relating the elastic properties of several laminates and multiaxial loads are presented.

Camanho, Pedro P.; Mayugo, Joan A.; Maimi, Pere; Davila, Carlos G.

2006-01-01

357

FEA OF THE HORSETAIL CREEK BRIDGE STRENGTHENED WITH FRP LAMINATES  

E-print Network

discrete cracks in ANSYS [4] and occurs as soon as stresses in the concrete exceed the tensile strength beams. #12;In this paper, three-dimensional finite element bridge models using ANSYS software strengthening with FRP laminates. Nonlinear finite element analysis is performed using the ANSYS finite element

Yim, Solomon C.

358

FINITE ELEMENT MODELING OF RC CONNECTIONS STRENGTHENED WITH FRP LAMINATES  

Microsoft Academic Search

Use of fiber reinforced plastic (FRP) composites for strengthening of beams and columns in RC structures has attracted great attention in recent decades. However, less attention has been paid to strengthening RC connections with FRP laminates. In the current study, a finite element (FE) modeling has been proposed for the non-linear analysis of RC joints covered with FRP overlays. The

D. MOSTOFINEJAD; S. B. TALAEITABA

359

Low Velocity Impact Damage to Carbon/Epoxy Laminates  

NASA Technical Reports Server (NTRS)

Impact damage tends to be more detrimental to a laminate's compression strength as compared to tensile strength. Proper use of Non Destructive Evaluation (NDE) Techniques can remove conservatism (weight) from many structures. Test largest components economically feasible as coupons. If damage tolerance is a driver, then consider different resin systems. Do not use a single knockdown factor to account for damage.

Nettles, Alan T.

2011-01-01

360

Monitoring of impact damages in composite laminates using wavelet transform  

Microsoft Academic Search

Low-velocity impact damage is a major concern in the design of structures made of advanced laminated composites, because such damage is mostly hidden inside and cannot be detected by visual inspection. It is found that the acoustic emission (AE) waves generated by impact loads are undistinguishable from each mode and amount of damage by the conventional analysis methods in time

Dae-Un Sung; Chun-Gon Kim; Chang-Sun Hong

2002-01-01

361

Shear behavior of masonry panels strengthened by FRP laminates  

Microsoft Academic Search

The present experimental study, performed on brick masonry panels strengthened by Fiber Reinforced Polymer (FRP) laminates, was aimed to investigate the efficiency of an alternative shear reinforcement technique. A series of nine unreinforced masonry (URM) panels and 24 strengthened panels have been subjected to diagonal compression tests. Different reinforcement configurations were evaluated. Experimental results pointed out that FRP reinforcement applied

M. R. Valluzzi; D. Tinazzi; C. Modena

2002-01-01

362

Bending behavior of shape memory polymer based laminates  

Microsoft Academic Search

Shape memory polymers (SMP) are smart materials was characterized by the recoverability of shape memory effect, but its mechanical property such as the strength is low. In this study, for industrial applications, a carbon fiber fabric reinforced shape memory polymer was developed. Four kinds of specimens with different laminations of carbon fiber fabric and shape memory polymer sheet were prepared.

Chun-Sheng Zhang; Qing-Qing Ni

2007-01-01

363

Modeling of ductile and brittle/brittle laminates  

SciTech Connect

A micro-mechanical ``spring``-network model was used to simulate the deformation and fracture behaviors of ductile/brittle and brittle/brittle laminates. Effects of interfacial cohesion, moduli, grain boundary cohesion, yield stress are presented and compared with available experiments. We found that composites with higher yield stress and lower interfacial cohesion are tougher.

Chen, S.P.

1996-02-01

364

Three-dimensional vibration analysis of rotating laminated composite blades  

SciTech Connect

This work offers the first known three-dimensional continuum vibration analysis for rotating, laminated composite blades. A cornerstone of this work is that the dynamic energies of the rotating blade are derived from a three-dimensional elasticity based, truncated quadrangular pyramid model incorporating laminated orthotropicity, full geometric nonlinearity using an updated Lagrangian formulation and Coriolis acceleration terms. These analysis sophistications are included to accommodate the nonclassical directions of modern blade designs comprising thin, wide chord-lifting surfaces of laminated composite construction. The Ritz method is used to minimize the dynamic energies with displacements approximated by mathematically complete polynomials satisfying the vanishing displacement conditions at the blade root section exactly. Several tables and graphs are presented that describe numerical convergence studies showing the validity of the assumed displacement polynomials used herein. Nondimensional frequency data are presented for various rotating, truncated quadrangular pyramids, serving as first approximations of practical blades employed in aircraft engines and fans. A wide scope of results explain the influence of a number of parameters coined to rotating, laminated composite blade dynamics, namely aspect ratio (a/b), chord ratio (c/b), thickness ratio (b/h), variable thickness distribution (h[sub l]/h[sub t]), blade pretwist angle ([phi][sub 0]), composite fiber orientation angle ([theta]), and angular velocity ([Omega]). Additional examples are given that elucidate the significance of the linear and nonlinear kinematics used in the present three-dimensional formulation along with the importance of the Coriolis acceleration terms included in the analysis.

McGee, O.G. (Georgia Inst. of Tech., Atlanta, GA (United States). School of Civil Engineering); Chu, H.R. (Ohio State Univ., Columbus, OH (United States). Dept. of Civil Engineering)

1994-07-01

365

A method for observing gas evolution during plastic laminate cure  

NASA Technical Reports Server (NTRS)

Polyimide, phenolic, and other resins which develop volatiles during laminating or molding cure are studied using optimum cure cycles. The specimen is placed on a platen and sealed in a plastic bag, then heated and observed for gas evolution using a binocular microscope. A cover plate is added to sumulate an autoclave.

Nicholls, A. H.

1969-01-01

366

Development of fibre metal laminates for advanced aerospace structures  

Microsoft Academic Search

Fibre metal laminates offer significant improvements over current available materials for aircraft structures. While weight reduction and improved damage tolerance characteristics were the prime drivers to develop these new family of materials, it turns out that they have additional benefits which become more and more important for todays designers, e.g. cost reduction and improved safety. The combination of these aspects

L. B Vogelesang; A Vlot

2000-01-01

367

On the mechanics of thin-walled laminated composite beams  

Microsoft Academic Search

A formal engineering approach of the mechanics of thin-walled laminated beams based on kinematic assumptions consistent with Timoshenko beam theory is presented. Thin-walled composite beams with open or closed cross section subjected to bending and axial load are considered. A variational formulation is employed to obtain a comprehensive description of the structural response. Beam stiffness coefficients, which account for the

Ever J. Barbero; Roberto Lopez-Anido; Julio F. Davalos

1993-01-01

368

On the Mechanics of Thin-Walled Laminated Composite Beams  

Microsoft Academic Search

A formal engineering approach of the mechanics of thin-walled laminated beams based on kinematic assumptions consistent with Timoshenko beam theory is pre sented. Thin-walled composite beams with open or closed cross section subjected to bend ing and axial load are considered. A variational formulation is employed to obtain a com prehensive description of the structural response. Beam stiffness coefficients, which

Ever J. Barbero; Roberto Lopez-Anido; Julio F. Davalos

1993-01-01

369

Thermoviscoelastic characterization and prediction of Kevlar/epoxy composite laminates  

NASA Technical Reports Server (NTRS)

The thermoviscoelastic characterization of Kevlar 49/Fiberite 7714A epoxy composite lamina and the development of a numerical procedure to predict the viscoelastic response of any general laminate constructed from the same material were studied. The four orthotropic material properties, S sub 11, S sub 12, S sub 22, and S sub 66, were characterized by 20 minute static creep tests on unidirectional (0) sub 8, (10) sub 8, and (90) sub 16 lamina specimens. The Time-Temperature Superposition-Principle (TTSP) was used successfully to accelerate the characterization process. A nonlinear constitutive model was developed to describe the stress dependent viscoelastic response for each of the material properties. A numerical procedure to predict long term laminate properties from lamina properties (obtained experimentally) was developed. Numerical instabilities and time constraints associated with viscoelastic numerical techniques were discussed and solved. The numerical procedure was incorporated into a user friendly microcomputer program called Viscoelastic Composite Analysis Program (VCAP), which is available for IBM PC type computers. The program was designed for ease of use. The final phase involved testing actual laminates constructed from the characterized material, Kevlar/epoxy, at various temperatures and load level for 4 to 5 weeks. These results were compared with the VCAP program predictions to verify the testing procedure and to check the numerical procedure used in the program. The actual tests and predictions agreed for all test cases which included 1, 2, 3, and 4 fiber direction laminates.

Gramoll, K. C.; Dillard, D. A.; Brinson, H. F.

1990-01-01

370

Statistical Theory of Strength of Laminated Composites II  

Microsoft Academic Search

The statistical theory for fracture of laminated composites devel oped previously has been extended to take account of stress enhance ment in neighboring elements around primary fractures. The results show that: a) the effective stress enhancement is less for an elastic matrix than for a rigid-plastic matrix, b) for constant length the strength of the composites rise with increasing numbers

Peter M. Scop; Ali S. Argon

1969-01-01

371

Durability of compression molded sisal fiber reinforced mortar laminates  

Microsoft Academic Search

This paper presents an experimental research on the durability performance of compression molded sisal fibercement mortar laminates (SFRML). To obtain a material with enhanced performance, the used methodology was to replace the Portland cement (PC) by calcined clay (metakaolin and calcined waste crushed clay brick) in order to produce a matrix totally free of calcium hydroxide (CH). The content of

Romildo Dias Toledo Filho; Flvio de Andrade Silva; E. M. R. Fairbairn; Joo de Almeida Melo Filho

2009-01-01

372

Aging of GFRP laminates and confinement of concrete columns  

Microsoft Academic Search

Mechanical properties of fiber reinforced polymers (GFRP) laminates change with water sorption, solar rays or cycles of lowhigh humidity and their degradation is studied under accelerated aging. The results showed that (i) the Youngs modulus of plates suffers only minor changes; (ii) moisture exposure by immersion in water causes only minor degradation; (iii) thermal cycles of small amplitude, around room

Manuel A. G. Silva

2007-01-01

373

Distance Decay of Similarity in Neotropical Diatom Communities  

PubMed Central

Background The regression of similarity against distance unites several ecological phenomena, and thus provides a highly useful approach for illustrating the spatial turnover across sites. Our aim was to test whether the rates of decay in community similarity differ between diatom growth forms suggested to show different dispersal ability. We hypothesized that the diatom group with lower dispersal ability (i.e. periphyton) would show higher distance decay rates than a group with higher dispersal ability (i.e. plankton). Methods/Principal findings Periphyton and phytoplankton samples were gathered at sites distributed over an area of approximately 800 km length in the Negro River, Amazon basin, Brazil, South America (308?00?S; 5954?30?W). Distance decay relationships were then estimated using distance-based regressions, and the coefficients of these regressions were compared among the groups with different dispersal abilities to assess our predictions. We found evidence that different tributaries and reaches of the Negro River harbor different diatom communities. As expected, the rates of distance decay in community similarity were higher for periphyton than for phytoplankton indicating the lower dispersal ability of periphytic taxa. Conclusions/Significance Our study demonstrates that the comparison of distance decay relationships among taxa with similar ecological requirements, but with different growth form and thus dispersal ability provides a sound approach to evaluate the effects of dispersal ability on beta diversity patterns. Our results are also in line with the growing body of evidence indicating that microorganisms exhibit biogeographic patterns. Finally, we underscore that clumbing all microbial taxa into one group may be a flawed approach to test whether microbes exhibit biogeographic patterns. PMID:23028767

Wetzel, Carlos E.; Bicudo, Denise de C.; Ector, Luc; Lobo, Eduardo A.; Soininen, Janne; Landeiro, Victor L.; Bini, Luis M.

2012-01-01

374

Hierarchical Silica Nanostructures Inspired by Diatom Algae Yield Superior Deformability, Toughness, and Strength  

E-print Network

Hierarchical Silica Nanostructures Inspired by Diatom Algae Yield Superior Deformability, Toughness algae that is mainly composed of amorphous silica, which features a hierarchical structure that ranges in diatom algae as a basis to study a bioinspired nanoporous material implemented in crystalline silica. We

Buehler, Markus J.

375

The Development and Application of a Diatom-Based Quantitative Reconstruction Technique in Forensic Science  

Microsoft Academic Search

Diatoms are a group of unicellular algae that have been recorded and classified for over 200 years and have been used in a range of applications in forensic science. We have developed a quantitative diatom-based reconstruction technique to confirm drowning as a cause of death and localize the site of drowning in two recent, high-profile, case studies. In both case

Benjamin P. Horton; Steve Boreham; Caroline Hillier

2006-01-01

376

Revised Miocene and Pliocene diatom biostratigraphy of Upper Newport Bay, Newport Beach, California  

USGS Publications Warehouse

North Pacific diatom zones XXIII through IX of Schrader are recognizable in the middle Miocene to lower Pliocene stratigraphic section exposed around Upper Newport Bay in Newport Beach, California. Correlation with DSDP Site 173 and other stratigraphic sections in California allows the selection of diatom datums that are the most reliable for long-distance correlation. Individual diatom datums are proposed as markers for North Pacific diatom zones XXIII through IX. Correlations with DSDP Site 173 reveal a hiatus in the lower part of Core 15 that corresponds with a distinct lithologic and floral change in the core. Preliminary silicoflagellate data for the Upper Newport Bay stratigraphic section supports the diatom correlations. Correlation with calcareous nannofossil, radiolarian, and silicoflagellate zones at Upper Newport Bay and at DSDP Site 173 suggests that the boundary between North Pacific diatom zones XVII and XVI approximates the middle Miocene/upper Miocene boundary. The Miocene/Pliocene boundary is estimated to be in North Pacific diatom zone X. One new stratigraphically useful diatom species is described, Lithodesmium reynoldsii. ?? 1976.

Barron, J.A.

1976-01-01

377

Ammonium accumulation during a silicate-limited diatom bloom indicates the potential for ammonia emission events  

E-print Network

Ammonium accumulation during a silicate-limited diatom bloom indicates the potential for ammonia of air­sea ammonia (NH3) flux under assumed `normal' `peak bloom' and `post-diatom-bloom' conditions will lead to changes in the magnitude and direction of air­sea ammonia flux. If our results are generally

Hansell, Dennis

378

Role of rotational-translational coupling in vibrational relaxation of matrix-isolated diatomic molecules  

NASA Astrophysics Data System (ADS)

Vibrational-rotational coupling, due to the fact that the center of interaction is displaced from the center of mass in a heteronuclear diatomic molecule, provides a mechanism for nonradiative vibrational relaxation of diatomic impurities in matrices. A theoretical expression for the rate constant in semiquantitative agreement with experiment is derived.

Diestler, D. J.; Ladouceur, H. Douglas

1980-03-01

379

Spatio-temporal structure of diatom assemblages in a temperate estuary. A STATICO analysis  

Microsoft Academic Search

This study examines the spatio-temporal structure of diatom assemblages in a temperate estuary (Ria de Aveiro, Western Portugal). Eighteen monthly surveys were conducted, from January 2002 to June 2003, at three sampling sites (at both high and low tide) along the estuarine salinity gradient. The relationship of diatom assemblages and environmental variables was analysed using the STATICO method, which has

Susana Mendes; Ma Jos Fernndez-Gmez; Paula Resende; Mrio Jorge Pereira; Ma Purificacin Galindo-Villardn; Ulisses Miranda Azeiteiro

2009-01-01

380

Iron enrichment stimulates toxic diatom production in high-nitrate, low-chlorophyll areas  

E-print Network

Iron enrichment stimulates toxic diatom production in high-nitrate, low-chlorophyll areas Charles G-scale iron fertilizations to help mitigate global climate change. Controversy surrounds these initiatives experiments have shown that iron additions stimulate growth of the toxigenic diatom genus Pseudonitzschia

Cochlan, William P.

381

DIATOM INDICES OF STREAM ECOSYSTEM CONDITIONS: COMPARISON OF GENUS VS. SPECIES LEVEL IDENTIFICATIONS  

EPA Science Inventory

Diatom assemblage data collected between 1993 and 1995 from 233 Mid-Appalachian streams were used to compare indices of biotic integrity based on genus vs. species level taxonomy. Thirty-seven genera and 197 species of diatoms were identified from these samples. Metrics included...

382

Effects of physical disturbance and canopy cover on attached diatom community structure in an Idaho stream  

Microsoft Academic Search

A field experiment was conducted to determine the effect of disturbance frequency on diatom communities established on artificial substrates within an open canopy site and a closed canopy site of a 3rd order stream. The open canopy site (OCS) had a total of 80 diatom taxa colonizing the substrates, while the closed canopy site (CCS) had only 55 taxa. Cluster

Christopher T. Robinson; Samuel R. Rushforth

1987-01-01

383

DIATOM SPECIES RICHNESS IN STREAMS OF THE EASTERN US: STREAM SIZE AND HABITAT EFFECTS  

EPA Science Inventory

We analyzed the relationship between benthic diatom assemblages, stream size, and habitat characteristics in 445 first through seventh order streams in the Mid-Atlantic (n=230), South Atlantic (n=61), Ohio (n=140), and Tennessee (n=14) hydrologic regions. Diatom samples were col...

384

Simple Bond-Charge Model for Potential-Energy Curves of Heteronuclear Diatomic Molecules  

Microsoft Academic Search

A model for the vibrational potential-energy functions of diatomic molecules, previously applied to homonuclear molecules only, is extended to 54 heteronuclear diatomic molecules in 93 different electronic states. Experimental Re and ke values are used to determine for each species the empirical bond-charge and bond-length parameters, q and ?, in the homopolar model potential W = W0 + (e2 ?

Raymond F. Borkman; Gary Simons; Robert G. Parr

1969-01-01

385

Automatic segmentation of diatom images Andrei C. Jalba, Jos B. T. M. Roerdink  

E-print Network

Automatic segmentation of diatom images Andrei C. Jalba, Jos B. T. M. Roerdink Institute of diatom images. The proposed method belongs to the class of hybrid segmentation techniques, and is based as watershed lines) are extracted. 1 Introduction Segmentation is one of the critical aspects in many image

Roerdink, Jos B.T.M.

386

Architecture and material properties of diatom shells provide effective mechanical protection  

Microsoft Academic Search

Diatoms are the major contributors to phytoplankton blooms in lakes and in the sea and hence are central in aquatic ecosystems and the global carbon cycle. All free-living diatoms differ from other phytoplankton groups in having silicified cell walls in the form of two `shells' (the frustule) of manifold shape and intricate architecture whose function and role, if any, in

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

2003-01-01

387

ASSESSMENT OF WATER QUALITY USING EPIPHYTIC DIATOM ASSEMBLAGES ON CLADOPHORA FROM THE ST. LAWRENCE RIVER (CANADA)  

Microsoft Academic Search

Diatoms epiphytic on Cladophora were examined from 36 sites in the Saint Lawrence River between Salaberry-de-Valleyfield and Ile d'Orleans (Qubec, Canada). A total of 129 diatom taxa were identified from Cladophora in June 1995, and of these, 34 species were present at a relative abundance ? 1% at three or more sites. The four most abundant taxa were Cocconeis pediculus,

Jacqueline M. OConnell; Euan D. Reavie; John P. Smol

1997-01-01

388

Calibration of diatoms along a nutrient gradient in Florida Everglades Water Conservation Area2A, USA  

Microsoft Academic Search

The relationship between diatom taxa preserved in surface soils and environmental variables at 31 sites in Water Conservation Area 2A (WCA-2A) of the Florida Everglades was explored using multivariate analyses. Surface soils were collected along a phosphorus (P) gradient and analyzed for diatoms, total P, % nitrogen (N), %carbon (C), calcium (Ca), and biogenic silica (BSi). Phosphorus varied from 315-1781

Sherri R. Cooper; Jacqueline Huvane; Panchabi Vaithiyanathan; Curtis J. Richardson

1999-01-01

389

A biological function for cadmium in marine diatoms Todd W. Lane* and Francois M. M. Morel  

E-print Network

A biological function for cadmium in marine diatoms Todd W. Lane* and Franc¸ois M. M. Morel a biological function. Herein, we pro- vide evidence of a biological role for Cd in the marine diatom Thalassiosira weissflogii under conditions of low zinc, typical of the marine environment. Addition of Cd to Zn

Morel, François M. M.

390

Diatoms as an aid in identifying late-Holocene tsunami deposits  

Microsoft Academic Search

Diatoms (Bacillariophyta) help identify the onshore deposits of tsunamis from earthquakes on the Cascadia subduction zone along the Pacific coast of Oregon, Washington, and British Columbia, and on faults high in the North American plate in the Puget Sound area of Washington. At the Copalis River, Washington, diatom analyses suggest that a tsunami deposit about 300 calendric years old (300

Eileen Hemphill-Haley

1996-01-01

391

Epilithic and epipelic diatoms in the Sandusky River, with emphasis on species diversity and water pollution  

Microsoft Academic Search

Benthic diatom communities were collected seasonally from silty and rocky substrates to survey the water quality of the Sandusky River. Even though species composition was highly variable along the river, recurrent changes in relative abundance of specific diatom taxa and changes in overall community composition delineated areas where discharge of treated sewage affected water quality of the river. Changes in

R. Jan Stevenson

1984-01-01

392

Lamin B2 prevents chromosome instability by ensuring proper mitotic chromosome segregation  

PubMed Central

The majority of human cancer shows chromosomal instability (CIN). Although the precise mechanism remains largely uncertain, proper progression of mitosis is crucial. B-type lamins were suggested to be components of the spindle matrix of mitotic cells and to be involved in mitotic spindle assembly; thus, B-type lamins may contribute to the maintenance of chromosome integrity. Here, using a proteomic approach, we identified lamin B2 as a novel protein involved in CIN. Lamin B2 expression decreased in colorectal cancer cell lines exhibiting CIN, as compared with colorectal cancer cell lines exhibiting microsatellite instability (MIN), which is mutually exclusive to CIN. Importantly, lamin B2 knockdown in MIN-type colorectal cancer cells induced CIN phenotypes such as aneuploidy, chromosome mis-segregation and aberrant spindle assembly, whereas ectopic expression of lamin B2 in CIN-type colorectal cancer cells prevented their CIN phenotypes. Additionally, immunohistochemical analysis showed a lower expression of lamin B2 in cancer tissues extracted from patients with sporadic colorectal cancer (CIN-type) than that from patients with hereditary non-polyposis colorectal cancer (HNPCC; MIN type). Intriguingly, mitotic lamin B2 in MIN cancer cells was localized outside the spindle poles and mitotic lamin B2 localization was diminished in CIN cancer cells, suggesting an important role of lamin B2 in proper mitotic spindle formation. The obtained results suggest that lamin B2 maintains chromosome integrity by ensuring proper spindle assembly and that its downregulation causes CIN in colorectal cancer. PMID:24637494

Kuga, T; Nie, H; Kazami, T; Satoh, M; Matsushita, K; Nomura, F; Maeshima, K; Nakayama, Y; Tomonaga, T

2014-01-01

393

Nuclear Lamin-A Scales with Tissue Stiffness and Enhances Matrix-Directed Differentiation  

PubMed Central

Tissues can be soft like fat, which bears little stress, or stiff like bone, which sustains high stress, but whether there is a systematic relationship between tissue mechanics and differentiation is unknown. Here, proteomics analyses revealed that levels of the nucleoskeletal protein lamin-A scaled with tissue elasticity, E, as did levels of collagens in the extracellular matrix that determine E. Stem cell differentiation into fat on soft matrix was enhanced by low lamin-A levels, whereas differentiation into bone on stiff matrix was enhanced by high lamin-A levels. Matrix stiffness directly influenced lamin-A protein levels, and, although lamin-A transcription was regulated by the vitamin A/retinoic acid (RA) pathway with broad roles in development, nuclear entry of RA receptors was modulated by lamin-A protein. Tissue stiffness and stress thus increase lamin-A levels, which stabilize the nucleus while also contributing to lineage determination. PMID:23990565

Swift, Joe; Ivanovska, Irena L.; Buxboim, Amnon; Harada, Takamasa; Dingal, P. C. Dave P.; Pinter, Joel; Pajerowski, J. David; Spinler, Kyle R.; Shin, Jae-Won; Tewari, Manorama; Rehfeldt, Florian; Speicher, David W.; Discher, Dennis E.

2014-01-01

394

Dissociation rate of bromine diatomics in an argon heat bath  

NASA Technical Reports Server (NTRS)

The evolution of a collection of 300 K bromine diatomics embedded in a heat bath of argon atoms at 1800 K was studied by computer, and a dissociation-rate constant for the reaction Br2 + BR + Ar yields Br + Ar was determined. Previously published probability distributions for energy and angular momentum transfers in classical three-dimensional Br2-Ar collisions were used in conjunction with a newly developed Monte Carlo scheme for this purpose. Results are compared with experimental shock-tube data and the predictions of several other theoretical models. A departure from equilibrium is obtained which is significantly greater than that predicted by any of these other theories.

Razner, R.; Hopkins, D.

1973-01-01

395

Coherent control of mesoscopic superpositions in a diatomic molecule  

E-print Network

A phase controlled wave packet, recently used in experiment of wave packet interferometry of adiatomic molecule, is investigated to obtain mesoscopic superposition structures, useful in quantum metrology. This analysis provides a new way of obtaining sub-Planck scale structures at smaller time scale of revival dynamics. We study a number of situations for delineating the smallest interference structures and their control by tailoring the relative phase between two subsidiary wave packets. We also find the most appropriate state, so far, for high precision parameter estimation in a system of diatomic molecule.

Suranjana Ghosh

2012-04-27

396

Rotating Morse wave packet dynamics of diatomic molecule  

E-print Network

We investigate the dynamics of a rotating Morse wave packet, appropriate for a ro-vibrating diatomic molecule. The coupling between vibrational and rotational degrees of freedom is explicated in real position space as well as in phase space Wigner distribution of a SU(2) coherent state at various dynamically evolved times. We choose the well studied $I_{2}$ molecule with the parameter values in good agrement with experiments. A quantitative measure of the angles of rotations for different angular momenta is also given.

Utpal Roy; Suranjana Ghosh

2009-07-17

397

Shedding light on diatom photonics by means of digital holography.  

PubMed

Diatoms are among the dominant phytoplankters in the world's oceans, and their external silica investments, resembling artificial photonic crystals, are expected to play an active role in light manipulation. Digital holography allowed studying the interaction with light of Coscinodiscus wailesii cell wall reconstructing the light confinement inside the cell cytoplasm, condition that is hardly accessible via standard microscopy. The full characterization of the propagated beam, in terms of quantitative phase and intensity, removed a long-standing ambiguity about the origin of the light confinement. The data were discussed in the light of living cell behavior in response to their environment. PMID:23242911

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

2014-05-01

398

Diatomic molecules in optical and microwave dipole traps  

SciTech Connect

The dipole forces on rotating diatomic molecules are worked out in detail for optical as well as microwave radiation fields. The objective is in particular to investigate how the dipole forces and potentials depend on the subtle internal structure of the molecule, with special emphasis on hyperfine and Zeeman states. Dipole potentials are obtained from computations of the real part of the complex molecular polarizability, whereas the imaginary part yields the scattering force. Numerical examples are presented for {sup 23}Na{sub 2} and OH for optical (laser) fields related to strong electronic transitions and for microwave fields for the {Lambda} doubling in the OH ground state.

Lysebo, Marius [Faculty of Engineering, Oslo University College, NO-0130 Oslo (Norway); Veseth, Leif [Department of Physics, University of Oslo, NO-0316 Oslo (Norway)

2011-03-15

399

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

E-print Network

Dynamics of late spring and summer phytoplankton communities on Georges Bank, with emphasis o Keywords: Georges Bank Alexandrium Dinoflagellates Diatoms Phytoplankton community a b s t r a c appeared to support a post-spring-bloom diatom community on the central crest of the Bank (total diatom

Townsend, David W.

400

Biochemical and Genetic Engineering of Diatoms for Polyunsaturated Fatty Acid Biosynthesis  

PubMed Central

The role of diatoms as a source of bioactive compounds has been recently explored. Diatom cells store a high amount of fatty acids, especially certain polyunsaturated fatty acids (PUFAs). However, many aspects of diatom metabolism and the production of PUFAs remain unclear. This review describes a number of technical strategies, such as modulation of environmental factors (temperature, light, chemical composition of culture medium) and culture methods, to influence the content of PUFAs in diatoms. Genetic engineering, a newly emerging field, also plays an important role in controlling the synthesis of fatty acids in marine microalgae. Several key points in the biosynthetic pathway of PUFAs in diatoms as well as recent progresses are also a critical part and are summarized here. PMID:24402175

Li, Hong-Ye; Lu, Yang; Zheng, Jian-Wei; Yang, Wei-Dong; Liu, Jie-Sheng

2014-01-01

401

Antarctic climate cooling and response of diatoms in glacial meltwater streams  

USGS Publications Warehouse

To understand biotic responses to an Antarctic cooling trend diatom samples from glacial meltwater streams in the McMurdo Dry Valleys, the largest ice-free area in Antarctica. Diatoms are abundant in these streams, and 24 of 40 species have only been found in the Antarctic. The percentage of these Antarctic diatom species increased with decreasing annual stream flow and increasing harshness of the stream habitat. The species diversity of assemblages reached a maximum when the Antarctic species accounted for 40-60% of relative diatom abundance. Decreased solar radiation and air-temperatures reduce annual stream flow, raising the dominance of these Antarctic species to levels above 60%. Thus, cooling favors the Antarctic species, and lowers diatom species diversity in this region. Copyright 2006 by the American Geophysical Union.

Esposito, R.M.M.; Horn, S.L.; McKnight, D.M.; Cox, M.J.; Grant, M.C.; Spaulding, S.A.; Doran, P.T.; Cozzetto, K.D.

2006-01-01

402

Variable frequency microwave (VFM) curing, processing of thermoset prepreg laminates. Final report  

SciTech Connect

The objective of this work was to investigate the beneficial effect of the variable frequency microwave (VFM) technology to cure thermosetting prepreg laminates. Further, it was to investigate the interrelationship and effect on the curing process of frequency, band width, and curing time with different types of laminates. Previous studies of microwave-assisted curing of neat resins (epoxy) and unidirectional glass and carbon fiber laminates with a fixed frequency of 2.45 GHz, have shown that a substantial reduction in the curing time was obtained. Results of this earlier work indicate that the microwave-assisted curing of multidirectional glass fiber laminates also show a substantial reduction of the required curing time. This may be explained by the penetration of microwave energy directly and throughout the laminate with enhancement of the kinetics of the chemical reaction. The fixed frequency microwave radiation of 2.45 GHz has been demonstrated to be a partially acceptable method to cure unidirectional carbon fiber laminates. 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. In addition to this short coming, the unidirectional laminate samples cured with the fixed frequency are visually nonuniform. Localized areas of darker colors (burn, hot spots, overheating) are attributed to the formation of standing waves within the microwave cavity. For this reason, the laminates are subject to proper rotation while curing through fixed frequency. The present research indicates that variable frequency microwave technology is a sound and acceptable processing method to effectively cure uni-, bi- or multi-directional thermosetting glass fiber laminates. Also, this methodology will effectively cure unidirectional thermosetting carbon fiber laminates. For all these cases, this technology yielded a substantial reduction in the required cure time of these laminates. Multidirectional carbon fiber laminates demonstrated a lack of coupling of VFM energy during the curing process.

Paulauskas, F.L.

1996-09-30

403

Laminated sediments in the Bering Sea reveal atmospheric teleconnections to Greenland climate on millennial to decadal timescales during the last deglaciation  

NASA Astrophysics Data System (ADS)

During the last glacial termination, the upper North Pacific Ocean underwent dramatic and rapid changes in oxygenation that lead to the transient intensification of Oxygen Minimum Zones (OMZs), recorded by the widespread occurrence of laminated sediments on circum-Pacific continental margins. We present a new laminated sediment record from the mid-depth (1100 m) northern Bering Sea margin that provides insight into these deglacial OMZ maxima with exceptional, decadal-scale detail. Combined ultrahigh-resolution micro-XRF data and sediment facies analysis of laminae reveals an alternation between predominantly terrigenous and diatom-dominated opal sedimentation. The diatomaceous laminae are interpreted to represent spring/summer productivity events that occur at the retreating sea ice margin. We identified five laminated sections in the deglacial part of our site. Laminae counts were carried out on these sections and correlated to the Blling-Allerd and Preboreal phases in North Greenland Ice Core (NGRIP) oxygen isotope record, indicating an annual deposition of individual laminae couplets. The observed rapid intra-decadal intensifications of anoxia, in particular within the Blling-Allerd, are tightly coupled to short-term warm events through increases in regional biogenic productivity. By correlating the counted laminated sections with Bering Sea Surface Temperature records (SST) and NGRIP ?18O data, we propose a deglacial minimum SST of 6-7 C for the preservation of laminae, which we call the deglacial temperature threshold for anoxia occurrence, a process that strongly implies a close atmospheric teleconnection between the North Pacific and North Atlantic regions. We suggest that concomitant increases in Bering Sea biogenic productivity, in combination with oxygen-poor waters entering the Being Sea, drove down oxygen concentrations to values below 0.1 mL L-1 and caused laminae preservation. Calculated benthic-planktic ventilation ages show no significant variations throughout the last deglaciation, indicating that changes in formation rates or differing sources of North Pacific mid-depth waters are not prime candidates for strengthening the OMZ at our site. The age models established by our correlation procedure allow to determine calendar age control points for the Blling-Allerd and the Preboreal that are independent of the initial radiocarbon-based chronology. Resulting calculated reservoir ages are 875 yr during the Blling-Allerd, and 910-770 yr for the Younger Dryas and the Preboreal, respectively.

Kuehn, H.; Lembke-Jene, L.; Gersonde, R.; Esper, O.; Lamy, F.; Arz, H.; Tiedemann, R.

2014-06-01

404

35. PALEOCLIMATIC SIGNIFICANCE OF DIACHRONOUS BIOGENIC FACIES, LEG 28, DEEP SEA DRILLING PROJECT  

Microsoft Academic Search

At Sites 265, 266, 267, and 268, in the southeast Indian Ocean, siliceous sediments, consisting of diatom oozes or diatom silty clays, overlie calcareous nannoplankton oozes and chalks. The boundary between siliceous and calcareous sediments shows a pronounced diachronism, younging towards the north. At the southern sites, 267 and 268, the tran- sition from a calcareous to a siliceous sedimentary

Elizabeth M. Kemp; Lawrence A. Frakes; Dennis E. Hayes

405

Potential role of large oceanic diatoms in new primary production  

NASA Astrophysics Data System (ADS)

Very large phytoplankton species >50 ?m in size, particularly diatoms, generally are found in background numbers throughout the euphotic zone of oceanic waters. Yet, when responding to episodic injections of new nutrients across the nutricline at the base of the euphotic zone these phototrophs may make a disproportionately large contribution to new primary production. To test this concept, we isolated a group of large diatoms from the Sargasso Sea and found that the specific growth rate of several of these species in culture was great enough at the ?2% light level in oligotrophic waters to meet the requirements of several hypothetical scenarios in which annual rates of new production from the sum of one or more episodic blooms were equal to contemporary estimates. Two of the fast-growing species, Stephanopyxis palmeriana (Greville) Grunow and Pseudoguinardia recta von Stosch, formed giant flocculant masses while growing. Such masses could sink rapidly out of the euphotic zone or be a direct food source for invertebrates or fish higher up the food chain. Not only would a short, simple trophic system with low losses result, but the events would virtually be impossible to observe with conventional sampling.

Goldman, Joel C.

1993-01-01

406

Diatom diversity in chronically versus episodically acidified adirondack streams  

USGS Publications Warehouse

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

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

2006-01-01

407

Use of diatom motility features as endpoints of metolachlor toxicity.  

PubMed

Many recent ecotoxicological studies suggest a relationship between freshwater contamination and increasing abundances of motile diatoms (potentially able to move). The capacity to escape would present advantages to species in polluted environments. However, actual motility as a response to toxicants had not been described and required experimental validation. We designed a specific experiment to assess how a field-isolated diatom (Gomphonema gracile) distributes energy to in situ resistance (increased population growth or photosynthesis) and escape (behavioral changes), when exposed to increasing concentrations of the herbicide metolachlor. We report here the dose-time dependent responses of G. gracile populations. They coped with low contamination by resisting in situ, with early hormetic responses highlighted by stimulation of chlorophyll-a fluorescence. At a higher dose, harmful impacts were observed on growth after a few days, but an earlier behavioral response suggested that higher motility (percentage of motile individuals and mean distance crossed) could be involved in escape. Our findings bring new arguments to support the implementation of real measurements instead of motility traits in toxicity assessment. Specifically, motion descriptors have been used as early-warning indicators of contamination in our study. Further works should address the reliability of these endpoints in more complex conditions (interspecific variability, behavior in the field). PMID:25481786

Coquill, Nathalie; Jan, Gwilherm; Moreira, Aurlie; Morin, Soizic

2015-01-01

408

Underwater locomotion strategy by a benthic pennate diatom Navicula sp.  

PubMed

The mechanism of diatom locomotion has been widely researched but still remains a hypothesis. There are several questionable points on the prevailing model proposed by Edgar, and some of the observed phenomena cannot be completely explained by this model. In this paper, we undertook detailed investigations of cell structures, locomotion, secreted mucilage, and bending deformation for a benthic pennate diatom Navicula species. According to these broad evidences, an updated locomotion model is proposed. For Navicula sp., locomotion is realized via two or more pseudopods or stalks protruded out of the frustules. The adhesion can be produced due to the pull-off of one pseudopod or stalk from the substratum through extracellular polymeric substances. And the positive pressure is generated to balance the adhesion because of the push-down of another pseudopod or stalk onto the substratum. Because of the positive pressure, friction is generated, acting as a driving force of locomotion, and the other pseudopod or stalk can detach from the substratum, resulting in the locomotion. Furthermore, this model is validated by the force evaluation and can better explain observed phenomena. This updated model would provide a novel aspect on underwater locomotion strategy, hence can be useful in terms of artificial underwater locomotion devices. PMID:23645345

Wang, Jiadao; Cao, Shan; Du, Chuan; Chen, Darong

2013-10-01

409

A review of the oxygen isotope composition of lacustrine diatom silica for palaeoclimate reconstruction  

NASA Astrophysics Data System (ADS)

Diatom silica (frustules) are a form of biogenic opal and contain oxygen isotopes that are being increasingly used in palaeoclimate studies. Frustules are comprised of an inner tetrahedrally bonded silica skeleton (Si-O-Si) with an outer, hydrous layer. The hydrous layer is freely exchangeable and must be removed prior to oxygen isotope measurement using oxidising reagents and/or high temperatures. Analysis of the oxygen isotope composition of diatom silica requires samples that are almost pure diatomite since extraction techniques will liberate oxygen from all the components in the sediment. There is a generally acceptable protocol involving chemistry, sieving and settling techniques and more recently laminar flow separation. Recent studies of lacustrine diatoms have shown that even a small proportion of contaminant can have a significant influence on the oxygen isotope value. All lake sediments require their own specific procedure and every sample must be scrutinised by microscopy to check for the level of contamination prior to analysis. Where sediment cannot be purified sufficiently, a semi-quantitative assessment of the diatom content can facilitate mass balance techniques. When robust preparation methods are used, diatom silica offers an important palaeoclimate proxy, providing an additional complementary, rather than an alternative, host of oxygen isotopes in carbonates. In lacustrine isotope studies it is often assumed, but rarely proven, that diatom silica form in isotope equilibrium and hence empirically derived palaeotemperature equations, usually made in vitro, can be used. Most studies lack the detailed investigation of contemporaneous materials from natural waters of the region under study to test these equations. Further investigations need to be conducted in order to understand the systematic relationship between temperature, water isotope composition and diatom isotope composition to enable quantitative interpretation of the sediment record. Experiments to test for vital effects and inter-specific differences have so far revealed little variation. It is useful to know when and where the diatom silica is formed in the modern environment, so details of diatom ecology are important in the interpretation of isotope data. Here we show that valuable palaeoclimate data can be gained from the oxygen isotope composition of diatom silica (? 18O diatom), especially since diatoms are abundant in many lakes sensitive to climate variation where other hosts (e.g., carbonates) are absent. To date the most successful studies have been conducted in areas where the ? 18O diatom registers changes in the oxygen isotope composition of the lake water (rather than temperature) which is then related to other aspects of climate. In these studies, the range of values obtained is often greater than the error introduced by contaminating materials.

Leng, Melanie J.; Barker, Philip A.

2006-03-01

410

Ancient and Modern Laminated Composites - From the Great Pyramid of Gizeh to Y2K  

SciTech Connect

Laminated metal composites have been cited in antiquity; for example, a steel laminate that may date as far back as 2750 B.C., 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 400 B.C. can be found in the literature. The Japanese sword is a laminated composite at several different levels and Merovingian blades were composed of laminated steels. Other examples are also available, including composites from China, Thailand, Indonesia, Germany, Britain, Belgium, France, and Persia. The concept of lamination to provide improved properties has also found expression in modern materials. Of particular interest is the development of laminates including high carbon and low carbon layers. These materials have unusual properties that are of engineering interest; they are similar to ancient welded Damascus steels. The manufacture of collectable knives, labeled ''welded Damascus'', has also been a focus of contemporary knifemakers. Additionally, in the Former Soviet Union, laminated composite designs have been used in engineering applications. Each of the above areas will be briefly reviewed, and some of the metallurgical principles will be described that underlie improvement in properties by lamination. Where appropriate, links are made between these property improvements and those that may have been present in ancient artifacts.

Wadsworth, J.; Lesuer, D.R.

2000-03-14

411

Behaviour of the germ cell specific lamin through mammalian spermatogenesis as probed with monoclonal antibodies.  

PubMed

We had earlier identified a 60 kDa nuclear lamin protein (lamin(g)) unique to the germ cells of rat testis which was subsequently shown to be antigenically conserved in germ cells of grasshopper, rooster, frog and plants. We have now obtained eight monoclonal antibodies in mouse against this lamin(g) antigen. While all the eight Mabs reacted with lamin(g) antigen in an immunoblot analysis, only three Mabs (A11C7, A11D4, C1F7) showed strong reactivity in the immunofluorescence analysis of the germ cells. The Mabs A11C7 and A11D4 showed a slight cross-reactivity with rat liver lamin B. Indirect immunofluorescence analysis of pre-meiotic, meiotic and post-meiotic germ cells with Mabs have shown that while the lamin(g) is localized in the lamina structures of spermatogonia and round spermatids, it is localized to the phase dense regions of pachytene spermatocytes which is in conformity with our previous observations using rabbit polyclonal antibodies. The localization of the antigen in the germ cells was also confirmed by immunohistochemical staining of the thin sections of seminiferous tubules. By immunostaining the surface spread pachytene spermatocytes, the antigen was further localized to the telomeric ends of the paired homologous chromosomes. Using anti-somatic lamin B antibodies, we have also demonstrated the absence of somatic lamins in meiotic and post-meiotic germ cells. The lamina structure of pre-meiotic spermatogonial nucleus contains both somatic lamin B and lamin(g) as evidenced by immunofluorescence studies with two differently fluorochrome labelled anti-lamin B and anti-lamin(g) antibodies. The selective retention of lamin(g) in the pachytene spermatocytes is probably essential for anchoring the telomeric ends of the paired chromosomes to the inner nuclear membrane. PMID:7820872

Manjula, K; Karande, A; Rao, M R

1994-08-01

412

Detection of diatoms in water and tissues by combination of microwave digestion, vacuum filtration and scanning electron microscopy.  

PubMed

The detection of diatoms has been proposed to be useful in the diagnosis of drowning. In the presented paper, we describe a novel method for qualitative and quantitative analysis of diatoms in water and organs. Samples were treated by microwave digestion. The fluid obtained was vacuum-filtrated; its sediment on the membrane was coated and examined under the scanning electron microscope with the mode of automatic field scanning; and qualitative and quantitative diatom analysis was performed based on the images captured automatically and on manual identification of the suspected diatoms at a required higher magnification. The method is rapid, sensitive, labor-saving, and accurate for qualitative and quantitative diatom analysis. However, further scientific research in the field of automatic diatom identification using SEM images has to be done in order to automate the process of detection and identification of diatoms in water and tissues for the diagnosis of drowning. PMID:23374881

Hu, Sunlin; Liu, Chao; Wen, Jinfeng; Dai, Weilie; Wang, Songcai; Su, HuiFang; Zhao, Jian

2013-03-10

413

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

PubMed

There is a considerable body of information regarding bacterially enhanced corrosion, however, this review focuses on diatoms (unicellular algae) whose contribution to biocorrosion is less well studied. The reasons why diatoms have been neglected in studies of biocorrosion in natural waters are discussed and the question whether diatoms should be considered as inert with respect of electrochemical processes is considered. A particular focus is given to the case of stainless steels (SS), which are widely used in variety of applications in natural waters. Basic information on the cell biology of diatoms is included in the review, particularly with respect to their ability to 'sense' and adhere to surfaces. Investigations at the nanoscale are reviewed as these studies provide information about the behavior of cells at interfaces. Recent advances include the use of atomic force microscopy (AFM), although only a few studies have been applied to diatoms. Regarding the electrochemical behavior of SS, the mechanisms by which diatoms influence the potential ennoblement process is discussed. Such studies reveal the association of diatoms, in addition to bacteria, with biocorrosion processes. PMID:22050233

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

2011-11-01

414

Metabarcoding vs. morphological identification to assess diatom diversity in environmental studies.  

PubMed

Diatoms are frequently used for water quality assessments; however, identification to species level is difficult, time-consuming and needs in-depth knowledge of the organisms under investigation, as nonhomoplastic species-specific morphological characters are scarce. We here investigate how identification methods based on DNA (metabarcoding using NGS platforms) perform in comparison to morphological diatom identification and propose a workflow to optimize diatom fresh water quality assessments. Diatom diversity at seven different sites along the course of the river system Odra and Lusatian Neisse from the source to the mouth is analysed with DNA and morphological methods, which are compared. The NGS technology almost always leads to a higher number of identified taxa (270 via NGS vs. 103 by light microscopy LM), whose presence could subsequently be verified by LM. The sequence-based approach allows for a much more graduated insight into the taxonomic diversity of the environmental samples. Taxa retrieval varies considerably throughout the river system, depending on species occurrences and the taxonomic depth of the reference databases. Mostly rare taxa from oligotrophic parts of the river systems are less well represented in the reference database used. A workflow for DNA-based NGS diatom identification is presented. 28000 diatom sequences were evaluated. Our findings provide evidence that metabarcoding of diatoms via NGS sequencing of the V4 region (18S) has a great potential for water quality assessments and could complement and maybe even improve the identification via light microscopy. PMID:25270047

Zimmermann, Jonas; Glckner, Gernot; Jahn, Regine; Enke, Neela; Gemeinholzer, Birgit

2014-09-30

415

Climate dependent diatom production is preserved in biogenic Si isotope signatures  

NASA Astrophysics Data System (ADS)

Climate change is likely to have the greatest impact on high-latitude ecosystems which are sensitive to climate fluctuations due to the relatively short growth season of diatoms. Biogenic silica (BSi) derived from diatoms provides a direct measure for tracking these processes although the knowledge gained from the amount of BSi preserved may be limited. In this study we report an application of a method based on Si isotope analyses of diatoms derived from a Gulf of Bothnia sediment core to reconstruct diatom production during the last two hundred years. During this time period large scale anthropogenic disturbances, such as the damming of rivers, can be observed. There is a relationship between measured Si isotope values of BSi, e.g. the silica incorporated into diatom frustules, in Bothnian Bay sediments and air temperature. This relationship suggests that the diatom Si isotope composition can be used to trace temperature variations over time. This method can be applied to other diatom dominated aquatic systems, i.e., a large part of the world's ocean and coastal seas, in order to improve our knowledge of impacts of temperature variations and thus also climate change and anthropogenic disturbance.

Sun, X.; Andersson, P.; Humborg, C.; Conley, D. J.; Crill, P.; Mrth, C.-M.

2011-04-01

416

Decoupling of nutrient and grazer impacts on a benthic estuarine diatom assemblage  

PubMed Central

Strong interactions between top-down (consumptive) and bottom-up (resource supply) trophic factors occur in many aquatic communities, but these forces can act independently in some microphytobenthic communities. Within benthic estuarine diatom assemblages, the dynamics of these interactions and how they vary with abiotic environmental conditions are not well understood. We conducted a field experiment at two sites with varying habitat characteristics to investigate the interactive effects of grazers and nutrients on benthic estuarine diatoms. We crossed snail (Cerithidea californica) and nutrient (nitrogen and phosphorus) addition treatments in enclosures on a restored tidal sandflat and a reference tidal mudflat in Mugu Lagoon, southern California. We repeated the study in summer 2000 and spring 2001 to assess temporal variation in the interactions. Snails caused a large decrease in diatom relative abundance and biomass (estimated as surface area); nutrients increased diatom abundance but did not alter diatom biomass. Snails and nutrients both reduced average diatom length, although the nutrient effect was weaker and temporally variable, occurring in the reference mudflat in the spring. There were few interactions between snail and nutrient addition treatments, suggesting that links between top-down and bottom-up forces on the diatom community were weak. There were no consistent differences in diatom assemblage characteristics between the two study sites, despite marked differences in sediment grain size and other abiotic characteristics between the sites. The strong diatom response to herbivores and weaker responses to enrichment differed from the previous studies where cyanobacteria increased in response to nutrient enrichment, further dissolving the black box perception of microphytobenthic communities.

Armitage, Anna R.; Gonzalez, Vanessa L.; Fong, Peggy

2014-01-01

417

Tracking changes in silicon isotopic composition during diatom descent and dissolution in the Cariaco Basin  

NASA Astrophysics Data System (ADS)

We measured the Si isotopic composition (i.e. ?30Si) of sinking diatom opal in Cariaco Basin to evaluate primary controls on diatom ?30Si values. The Cariaco Basin time series consists of five sediment traps at progressively greater depths on a single mooring and monthly hydrographic and dissolved nutrient measurements throughout the water column. Monthly measurements of diatom ?30Si from sediment traps between 225-m and 1200-m were made over a full seasonal cycle (May 2005-March 2006). Diatom ?30Si values from the suite of traps are compared directly to silicic acid concentrations in the overlying surface waters, opal flux values for each trap, and in-situ nutrient measurements. Preliminary data suggests a seasonal pattern with higher overall ?30Si during pronounced diatom bloom periods (i.e., elevated opal flux). With progressive dissolution (i.e., depth) diatom ?30Si becomes isotopically lighter. The greatest decrease in ?30Si values generally occurs between 400-m and 800-m and does not show a consistent relationship with decreasing opal flux (i.e., dissolution). These results suggest that diatom opal ?30Si decreases with opal dissolution, opposite of what is observed in laboratory dissolution experiments. A potential explanation is selective dissolution of ?30Si-enriched species, where preferential dissolution of lightly silicified late blooming diatoms with higher 30Si isotope leaves species with lower isotopic values and hence an overall lower ?30Si value for the assemblage. Future work will quantify changes in the diatom species assemblage with increasing depth to test this hypothesis.

Buckley, W. P.; Scher, H. D.; Thunell, R.; Brzezinski, M. A.; Peterson, T. D.

2011-12-01

418

Failure analysis of composite laminates including biaxial compression  

NASA Technical Reports Server (NTRS)

This report describes a continued effort on the development and application of the tensor polynomial failure criterion for composite laminate analysis. In particular, emphasis is given to the design, construction and testing of a cross-beam laminate configuration to obtain "pure' biaxial compression failure. The purpose of this test case was to provide to permit "closure' of the cubic form of the failure surface in the 1-2 compression-compression quadrant. This resulted in a revised set of interaction strength parameters and the construction of a failure surface which can be used with confidence for strength predictions, assuming a plane stress state exists. Furthermore, the problem of complex conjugate roots which can occur in some failure regions is addressed and an "engineering' interpretation is provided. Results are presented illustrating this behavior and the methodology for overcoming this problem is discussed.

Tennyson, R. C.; Elliott, W. G.

1983-01-01

419

Development of lightweight reinforced plastic laminates for spacecraft interior applications  

NASA Technical Reports Server (NTRS)

Lightweight, Kevlar - reinforced laminating systems that are non-burning, generate little smoke in the space shuttle environment, and are physically equivalent to the fiberglass/polyimide system used in the Apollo program for non-structural cabin panels, racks, etc. Resin systems representing five generic classes were screened as matrices for Kevlar 49 reinforced laminates. Of the systems evaluated, the polyimides were the most promising with the phenolics a close second. Skybond 703 was selected as the most promising resin candidate. With the exception of compression strength, all program goals of physical and mechanical properties were exceeded. Several prototype space shuttle mobility and translation handrail segments were manufactured using Kevlar/epoxy and Kevlar-graphite/epoxy. This application shows significant weight savings over the baseline aluminum configuration used previous. The hybrid Kevlar-graphite/epoxy is more suitable from a processing standpoint.

Hertz, J.

1975-01-01

420

Passively Damped Laminated Piezoelectric Shell Structures with Integrated Electric Networks  

NASA Technical Reports Server (NTRS)

Multi-field mechanics are presented for curvilinear piezoelectric laminates interfaced with distributed passive electric components. The equations of motion for laminated piezoelectric shell structures with embedded passive electric networks are directly formulated and solved using a finite element methodology. The modal damping and frequencies of the piezoelectric shell are calculated from the poles of the system. Experimental and numerical results are presented for the modal damping and frequency of composite beams with a resistively shunted piezoceramic patch. The modal damping and frequency of plates, cylindrical shells and cylindrical composite blades with piezoelectric-resistor layers are predicted. Both analytical and experimental studies illustrate a unique dependence of modal damping and frequencies on the shunting resistance and show the effect of structural shape and curvature on piezoelectric damping.

Saravanos, Dimitris A.

1999-01-01

421

Power losses in thick steel laminations with hysteresis  

NASA Astrophysics Data System (ADS)

Magnetic power losses have been experimentally investigated and theoretically predicted over a range of frequencies (direct current1.5 kHz) and peak inductions (0.5-1.5 T) in 1-mm-thick FeSi 2 wt. % laminations. The direct current hysteresis properties of the system are described by the Preisach model, with the Preisach distribution function reconstructed from the measurement of the recoil magnetization curve (Bp=1.7 T). On this basis, the time behavior of the magnetic induction vs frequency at different lamination depths is calculated by a finite element method numerical solution of Maxwell equations, which takes explicitly into account the Preisach model hysteretic B(H) relationship. The computed loop shapes are, in general, in good agreement with the measured ones. The power loss dependence on frequency is predicted and experimentally found to change from a f3/2 to a f2 law with increasing peak induction.

Appino, C.; Bertotti, G.; Bottauscio, O.; Fiorillo, F.; Tiberto, P.; Binesti, D.; Ducreux, J. P.; Chiampi, M.; Repetto, M.

1996-04-01

422

Iosipescu shear properties of graphite fabric/epoxy composite laminates  

NASA Technical Reports Server (NTRS)

The Iosipescu shear test method is used to measure the in-plane and interlaminar shear properties of four T300 graphite fabric/934 epoxy composite materials. Different weave geometries tested include an Oxford weave, a 5-harness satin weave, an 8-harness satin weave, and a plain weave with auxiliary warp yarns. Both orthogonal and quasi-isotropic layup laminates were tested. In-plane and interlaminar shear properties are obtained for laminates of all four fabric types. Overall, little difference in shear properties attributable to the fabric weave pattern is observed. The auxiliary warp material is significantly weaker and less stiff in interlaminar shear parallel to its fill direction. A conventional strain gage extensometer is modified to measure shear strains for use with the Iosipescu shear test. While preliminary results are encouraging, several design iterations failed to produce a reliable shear transducer prototype. Strain gages are still the most reliable shear strain transducers for use with this test method.

Walrath, D. E.; Adams, D. F.

1985-01-01

423

Vibration Control of Shear Deformable Laminated PLATESMODELING Implications  

NASA Astrophysics Data System (ADS)

A modal control approach is applied to control the vibration of homogeneous and laminated plates. The controller is designed using the linear optimal control theory. The performance of the controller designed according to a structural model of the plant based on the classical plate theory is evaluated and compared with that derived in the context of a higher order plate theory. It is found that the use of the classical plate model in the design of vibration control systems could lead to erroneous conclusions concerning the performance of the actual controlled system. The strong influence played by transverse shear deformation and lamination on the controlled system is clearly demonstrated and pertinent conclusions are outlined.

CHANG, MIN-YUNG; LIBRESCU, LIVIU

1999-12-01

424

Contact law and impact responses of laminated composites  

NASA Technical Reports Server (NTRS)

Static identation tests were performed to determine the law of contact between a steel ball and glass/epoxy and graphite/epoxy laminated composites. For both composites the power law with an index of 1.5 was found to be adequate for the loading curve. Substantial permanent deformations were noted after the unloading. A high order beam finite element was used to compute the dynamic contact force and response of the laminated composite subjected to the impact of an elastic sphere. This program can be used with either the classical Hertzian contact law or the measured contact law. A simple method is introduced for estimating the contact force and contact duration in elastic impacts.

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

1980-01-01

425

Development of failure criterion for Kevlar-epoxy fabric laminates  

NASA Technical Reports Server (NTRS)

The development of the tensor polynomial failure criterion for composite laminate analysis is discussed. In particular, emphasis is given to the fabrication and testing of Kevlar-49 fabric (Style 285)/Narmco 5208 Epoxy. The quadratic-failure criterion with F(12)=0 provides accurate estimates of failure stresses for the Kevlar/Epoxy investigated. The cubic failure criterion was re-cast into an operationally easier form, providing the engineer with design curves that can be applied to laminates fabricated from unidirectional prepregs. In the form presented no interaction strength tests are required, although recourse to the quadratic model and the principal strength parameters is necessary. However, insufficient test data exists at present to generalize this approach for all undirectional prepregs and its use must be restricted to the generic materials investigated to-date.

Tennyson, R. C.; Elliott, W. G.

1984-01-01

426

Fiberglass epoxy laminate fatigue properties at 300 and 20 K  

NASA Technical Reports Server (NTRS)

A subcritical liquid hydrogen orbital storage and supply experiment is being designed for flight in the Space Shuttle cargo bay. The Cryogenic Fluid Management Experiment (CFME) includes a liquid hydrogen tank supported in a vacuum jacket by two fiberglass epoxy composite trunnion mounts. The ability of the CFME to last for the required seven missions depends primarily on the fatigue life of the composite trunnions at cryogenic temperatures. To verify the trunnion design and test the performance of the composite material, fatigue property data at 300 and 20 K were obtained for the specific E-glass fabric/S-glass unidirectional laminate that will be used for the CFME trunnions. The fatigue life of this laminate was greater at 20 K than at 300 K, and was satisfactory for the intended application.

Toth, J. M., Jr.; Bailey, W. J.; Boyce, D. A.

1985-01-01

427

Transverse shear deformation effects in composite laminated plates  

E-print Network

j 16 '26' V ) 'y 'y -W xx 2w xy B u', 16 " 'x x, (14) Consider a cross-p1y laminate of any general stacking sequence with f1bers parallel to the axes x or y. For such laminates C 16 026 0 fo?ach ply ln the st~ok, so A16 A26 - B16 B26..., y N v'; N u'; '1 w', ; M w , ; (0, + M )w' on y = O, b (16. 2) ' y ' ' xy ' ' y 'y' xy 'x' ' y xy, x' If equations (15) are continuous at, the boundary, we see immediately that N = w', = w' = v = 0 on x = 0 a and N = w', = w' = u' = 0 x 'y y...

Coulter, Brett Ainsley

2012-06-07

428

Experimental determination of material constants of a hybrid composite laminate  

SciTech Connect

This paper discusses the results of the experimental study that was conducted in order to determine the material properties of a hybrid composite laminate made from Fiberite material MXM-7714/120 (a fabric prepreg consisting of woven Kevlar{reg_sign} 49 reinforcement impregnated with Fiberite 250 F (121 C) curing 7714 epoxy resin) and HYE-2448AIE (a 250 F (121 C) curing epoxy resin impregnated unidirectional graphite tape). First, each of the materials that comprise the hybrid laminate was fabricated separately according to ASTM-D-3039 specification in order to determine their material properties. The materials were then hybridized and the properties were determined. Data from this experiment reveal that a new class of material that can meet desired specifications can be created through hybridization. The data also revealed that the properties of the materials bonded together as a hybrid complement the properties of the constituent members of the hybrid.

Ihekweazu, S.N.; Lari, S.B.; Unanwa, C.O. [South Carolina State Univ., Orangeburg, SC (United States)

1999-07-01

429

Reliability after inspection. [of flaws on laminate surface  

NASA Technical Reports Server (NTRS)

The investigation is concerned with the derivation of relationships between the probability of having manufacturing defects, the probability of detecting a flaw, and the final reliability. Equations for the simple situation in which only one flaw can be present are used to introduce the relationships in a Bayes' theorem approach to the assessment of the final reliability. Situations which are prevalent in composites manufacturing are considered. Attention is given to a case involving the random occurrence of flaws on a laminate surface.

Davidson, J. R.

1975-01-01

430

Fiber Metal Laminates Made by the VARTM Process  

NASA Technical Reports Server (NTRS)

Fiber metal laminates (FMLs) are multi-component materials utilizing metals, fibers and matrix resins. Tailoring their properties is readily achievable by varying one or more of these components. Established FMLs like GLARE utilize aluminum foils, glass fibers and epoxy matrices and are manufactured using an autoclave. Two new processes for manufacturing FMLs using vacuum assisted resin transfer molding (VARTM) have been developed at the NASA Langley Research Center (LaRC). A description of these processes and the resulting FMLs are presented.

Jensen, Brian J.; Cano, Roberto J.; Hales, Stephen J.; Alexa, Joel A.; Weiser, Erik S.; Loos, Alfred; Johnson, W.S.

2009-01-01

431

Fast Neutron Transport through Laminated Iron-Water Shield  

Microsoft Academic Search

Reaction rates were measured in a laminated iron-water shield by threshold detectors, from which the neutron spectra were obtained with the aid of the SAND-II code. The error analysis for the unfolding of the spectra proved that the spectra obtained satisfactorily in the energy range of 110.5 MeV. One-dimensional calculations were made by the discrete ordinates transport codes ANISN-JR and

Toshimasa MIURA; Kiyoshi TAKEUCHI; Naoki YAMANO

1979-01-01

432

Improved serpentine laminating micromixer with enhanced local advection  

Microsoft Academic Search

It is a complicated task to achieve high level of mixing inside a microchannel because the flow is characterized by low Reynolds\\u000a number (Re). Recently, the serpentine laminating micromixer (SLM) was reported to achieve efficient chaotic mixing by introducing F-shape\\u000a mixing units successively in two layers such that two mixing mechanisms, namely splitting\\/recombination and chaotic advection,\\u000a enhance the mixing performance

Jang Min Park; Dong Sung Kim; Tae Gon Kang; Tai Hun Kwon

2008-01-01

433

A life prediction model for laminated composite structural components  

NASA Technical Reports Server (NTRS)

A life prediction methodology for laminated continuous fiber composites subjected to fatigue loading conditions was developed. A summary is presented of research completed. A phenomenological damage evolution law was formulated for matrix cracking which is independent of stacking sequence. Mechanistic and physical support was developed for the phenomenological evolution law proposed above. The damage evolution law proposed above was implemented to a finite element computer program. And preliminary predictions were obtained for a structural component undergoing fatigue loading induced damage.

Allen, David H.

1990-01-01

434

Test evaluation of a laminated wood wind turbine blade concept  

NASA Technical Reports Server (NTRS)

A series of tests conducted on a root end section of a laminated wood wind turbine blade are reported. The blade to hub transition of the wood blade uses steel studs cast into the wood D spar with a filled epoxy. Both individual studs and a full scale, short length, root section were tested. Results indicate that the bonded stud concept is more than adequate for both the 30 year life fatigue loads and for the high wind or hurricane gust loads.

Faddoul, J. R.

1981-01-01

435

Micromechanics-based structural analysis of thick laminated composites  

NASA Astrophysics Data System (ADS)

Thick filament wound cylinders, or local regions in structural laminates around cut-outs, fasteners, or stiffeners, may require three-dimensional (3D) analysis and evaluation, in order to fully characterize behavior and evaluate safety margins. This paper describes a particular approach to the 3D structural-level analysis of thick laminated composites that utilizes homogenization concepts and standard displacement-based finite element modeling. Hierarchical material modeling forms the basis of the procedure. The material model consists of two modules: (1) a micro-model of a unidirectional lamina, containing the basic 3D constitutive information for fiber and matrix constituents; and (2) a sublaminate model that enforces equilibrium of tractions between laminae, and delivers 3D homogenized stresses and strains and material tangent stiffnesses. This integrated approach provides the information required for evaluating damage and failure conditions at the microstructural level, and is essential for nonlinear analysis because of possible interactions between damage and failure modes. A nonlinear elastic material model is formulated, as an example; this nonlinear model, which is suitable for epoxy matrices, has been successfully implemented in a standard finite element code and used quite extensively. However, only elastic analysis results are presented, because the important characteristics of the modeling approach are clearly revealed in this setting. Comparisons are made between material model predictions and analytical, numerical, and experimental results for a unidirectional lamina, a thick laminate, and a thick cylinder under compression and bending. These results show that the accuracy of the procedure for thick laminates is quite satisfactory for practical purposes.

Pecknold, D. A.; Rahman, S.

1994-04-01

436

A Shear Deformable Shell Element for Laminated Composites  

NASA Technical Reports Server (NTRS)

A three-dimensional element based on the total Lagrangian description of the motion of a layered anisotropic composite medium is developed, validated, and used to analyze layered composite shells. The element contains the following features: geometric nonlinearity, dynamic (transient) behavior, and arbitrary lamination scheme and lamina properties. Numerical results of nonlinear bending, natural vibration, and transient response are presented to illustrate the capabilities of the element.

Chao, W. C.; Reddy, J. N.

1984-01-01

437

A mesomacro finite element modelling of laminate structures  

Microsoft Academic Search

A mesomacro modelling is proposed for laminates made of unidirectional layers of a polymer matrix reinforced with long fibres. The time-independent behaviour introduced in the first part of this article is improved herein to account for viscous phenomena through viscoelasticity and viscoplasticity. A spectrum-type viscoelastic model is considered, which is based on the definition of elementary viscoelastic mechanisms. Its mathematical

M. L. Boubakar; L. Vang; F. Trivaudey; D. Perreux

2003-01-01

438

Effect of damage on elastically tailored composite laminates  

Microsoft Academic Search

A variationally consistent theory is derived in order to predict the response of anisotropic thin-walled closed sections subjected to axial load, torsion and bending. The theory is valid for arbitrary cross-sections made of laminated composite materials with variable thickness and stiffness. Closed form expressions for the stiffness coefficients are provided as integrals in terms of lay-ups parameters and cross-sectional geometry.

Erian Armanios; Ashraf Badir; Victor Berdichevsky

1991-01-01

439

Flux distraction effect on magnetoelectric laminate sensors and gradiometer  

NASA Astrophysics Data System (ADS)

A magnetic flux distraction effect caused by a nearby metallic material was investigated for Metglas/Pb(Mg1/3Nb2/3)O3-PbTiO3 laminated magnetoelectric (ME) sensors. Using flux distraction, a ME sensor can perform an accurate search for metallic targets of different dimensions at various distances. Detection results and simulations were in good agreement. The findings demonstrate an effective means to employ stationary ME sensors and gradiometers for magnetic search applications.

Shen, Ying; Gao, Junqi; Wang, Yaojin; Hasanyan, Davresh; Finkel, Peter; Li, Jiefang; Viehland, D.

2013-10-01

440

Low-impulse blast behavior of fibre-metal laminates  

Microsoft Academic Search

This paper presents three dimensional (3D) finite element (FE) models of the low-impulse localised blast loading response of fibre-metal laminates (FMLs) based on an 2024-O aluminium alloy and a woven glass-fibre\\/polypropylene composite (GFPP). A vectorized user material subroutine (VUMAT) is developed to define the mechanical constitutive behaviour and Hashins 3D failure criteria incorporating strain-rate effects in the GFPP. In order

T. P. Vo; Z. W. Guan; W. J. Cantwell; G. K. Schleyer

441

Some frequency and damping measuements of laminated beryllium beams  

SciTech Connect

A quantum leap in vibration performance of beryllium structure has been experimentally investigated. Laminations, segmentation, and sandwich syntactic foam core have been demonstrated to have both high specific flexural structural stiffness and high damping for reduced vibratory response. Acquisition cost, weight, machinability and environmental benefits are also expected. Applications to structure of optical and inertial navigation equipment would lead to reductions in jitter levels and other vibratory response measures.

Andriulli, J.; Rogers, L.C.

1993-01-01

442

Some frequency and damping measuements of laminated beryllium beams  

SciTech Connect

A quantum leap in vibration performance of beryllium structure has been experimentally investigated. Laminations, segmentation, and sandwich syntactic foam core have been demonstrated to have both high specific flexural structural stiffness and high damping for reduced vibratory response. Acquisition cost, weight, machinability and environmental benefits are also expected. Applications to structure of optical and inertial navigation equipment would lead to reductions in jitter levels and other vibratory response measures.

Andriulli, J.; Rogers, L.C.

1993-06-01

443

Post-Lamination Manufacturing Process Automation for Photovoltaic Modules  

Microsoft Academic Search

This report describes work performed by Spire Corporation during Phase 1 of this three-phase PVMaT subcontract to develop new automated post-lamination processes for PV module manufacturing. These processes are applicable to a very broad range of module types, including those made with wafer-based and thin-film solar cells. No off-the-shelf automation was available for these processes prior to this program. Spire

M. J. Nowlan; J. M. Murach; T. W. McCormick; E. R. Lewis; S. J. Hogan

1999-01-01

444

Testing the utility of the diatom-bound N isotope proxy using batch cultures  

NASA Astrophysics Data System (ADS)

Changes in the isotopic composition of nitrogen bound in diatom frustules have been used to characterize past variation in surface nitrate utilization. The diatom-bound nitrogen in preserved frustules within sediments has been hypothesized to be a more stable archive of organic nitrogen, due to decreased alteration during sinking and early burial. Previous work has characterized the changes in isotopic composition of nitrogen in the seawater substrate and bulk product over the course of a diatom cultures growth. However, changes in the isotopic composition of nitrogen in the more stable diatom-bound fraction have not been directly compared to that of the dissolved inorganic substrate or bulk biomass in culture experiments, to date. This study aimed to examine the relationships between the isotopic composition of nitrogen within the seawater substrate, the bulk organic material, and the diatom-bound fraction in several species of living marine diatom cultures over varying degrees of fractional utilization of nitrate, whereby f was the fraction of nitrate remaining. Several species, including Fragilariopsis cylindrus, Fragilariopsis kerguelensis, Pseudo-nitzschia sp., Thalassiosira aestivalis, and Thalassiosira nordenskioeldii, were grown in order to evaluate these relationships in general and elucidate any differences between organisms. The studied group encompassed a range of sizes, degrees of silicification, growth rates, and morphologies. Centric, pennate, and chain-forming diatoms were included. Eleven closed-system, 20L batch cultures of individual diatom species were grown at their maximum acclimated growth rate in sterile filtered F/2 seawater stock at 2C or 14C and 100?E of 24-hour light and were sampled 5-10 times over their growth curve. The average f was 0.31 0.22 with a range from 0.78 to 0.01. An average enrichment factor of 5.7 3.3 was calculated for the substrate (?substrate) over all eleven experiments. The diatom-bound ?15N was on average 6.4 2.2 lower than the bulk ?15N over the entire growth curve. Thalassiosira aestivalis and Fragilariopsis cylindrus demonstrated remarkably significant increasing trends in the diatom-bound ?15N while Pseudo-nitzschia sp. had slightly more variability, and Thalassiosira nordenskioeldii showed nearly no change. These results suggest that changes in sedimentary diatom assemblages may also contribute to the diatom-bound ?15N signal.

Horn, M. G.; Robinson, R. S.; Rynearson, T.

2009-12-01

445

Hydrology and Diatom Phytoplankton of High Arctic Lakes and Ponds on Store Koldewey, Northeast Greenland  

NASA Astrophysics Data System (ADS)

We document hydrological and phytoplankton characteristics of nine lakes and two ponds on Store Koldewey, a culturally undisturbed island off Northeast Greenland. The limnological survey included the recording of temperature, conductivity, oxygen concentration and saturation, pH, ionic composition, transparency, and the diatom phytoplankton community. In summer 2003, the lakes were cold, monomictic, thermally unstratified, alkaline and likely oligotrophic water bodies. Diatom phytoplankton was present in six lakes and consisted of four dominant species (Aulacoseira tethera, Cyclotella pseudostelligera, C. rossii, and Fragilaria tenera). The concentration of planktonic diatoms varied distinctly between the lakes.

Cremer, Holger; Bennike, Ole; Hkansson, Lena; Hultzsch, Nadja; Klug, Martin; Kobabe, Svenja; Wagner, Bernd

2005-02-01

446

Regulation of Nucleotide Excision Repair by Nuclear Lamin B1  

PubMed Central

The nuclear lamins play important roles in the structural organization and function of the metazoan cell nucleus. Recent studies on B-type lamins identified a requirement for lamin B1 (LB1) in the regulation of cell proliferation in normal diploid cells. In order to further investigate the function of LB1 in proliferation, we disrupted its normal expression in U-2 OS human osteosarcoma and other tumor cell lines. Silencing LB1 expression induced G1 cell cycle arrest without significant apoptosis. The arrested cells are unable to mount a timely and effective response to DNA damage induced by UV irradiation. Several proteins involved in the detection and repair of UV damage by the nucleotide excision repair (NER) pathway are down-regulated in LB1 silenced cells including DDB1, CSB and PCNA. We propose that LB1 regulates the DNA damage response to UV irradiation by modulating the expression of specific genes and activating persistent DNA damage signaling. Our findings are relevant to understanding the relationship between the loss of LB1 expression, DNA damage signaling, and replicative senescence. PMID:23894423

Butin-Israeli, Veronika; Adam, Stephen A.; Goldman, Robert D.

2013-01-01

447

The shock response of float-glass laminates  

NASA Astrophysics Data System (ADS)

Interfaces within glass targets give rise to variations in the mode of failure of material components. The wide use of such laminates merits further investigation of the failure mechanism. It is already known that when shocked above a threshold of 4 GPa, glass fails under compression behind a propagating front following the compression front. Work is presented which indicates how this failure process is altered by bonding together two plates to introduce an interface, rather than leaving a monolithic target. After crossing an internal interface, the failure wave propagates only after a delay in soda-lime glass and the failed strength of the material is increased at the inner interface compared with that at the impact face. Addition of a second interface illustrates these effects. Recent work has shown that failure of more than two plates bonded together during impact shapes the pulse transmitted through materials. Indeed it has been suggested that glass sheets bonded together show some of the features of polycrystalline brittle materials. In this work, the stress has been monitored at different stations in the laminate to ascertain the effect of varying the number of tiles within the laminate. It is found that the pulse rises to ca. 4 GPa quickly and then is ramped more gradually as the number of glass sheets is increased.

Bourne, N. K.

2005-09-01

448

Dynamic characterization of a laminated composite magnetorheological fluid sandwich plate  

NASA Astrophysics Data System (ADS)

This study investigates the dynamic properties of a laminated composite magnetorheological (MR) fluid sandwich plate. The governing differential equations of motion of a sandwich plate embedding a MR fluid layer as the core layer and laminated composite plates as the face layers are presented in a finite element formulation. The validity of the developed finite element formulation is demonstrated by comparing the results in terms of the natural frequencies derived from the present finite element formulation with those in the available literature. Various parametric studies are also performed to investigate the effect of a magnetic field on the variation of the natural frequencies and loss factors of the MR fluid composite sandwich plate under various boundary conditions. Furthermore, the effect of the thickness of the MR fluid layer and the ply orientation of the composite face layers on the variation of the natural frequencies and loss factors are studied. The free vibration mode shapes under various boundary conditions of a MR fluid laminated composite sandwich plate are also presented. The forced vibration response of a MR fluid composite plate is investigated to study the dynamic response of the sandwich plate under harmonic force excitations in various magnetic fields. The study suggests that the natural frequency increases with increasing magnetic field, irrespective of the boundary conditions. The reduction in peak deflection at each mode under a harmonic excitation force with variation of the applied magnetic field shows the effectiveness of the MR fluid layer in reducing the vibration amplitude of the composite sandwich plate.

Manoharan, R.; Vasudevan, R.; Jeevanantham, A. K.

2014-02-01

449

A serpentine laminating micromixer combining splitting/recombination and advection.  

PubMed

Mixing enhancement has drawn great attention from designers of micromixers, since the flow in a microchannel is usually characterized by a low Reynolds number (Re) which makes the mixing quite a difficult task to accomplish. In this paper, a novel integrated efficient micromixer named serpentine laminating micromixer (SLM) has been designed, simulated, fabricated and fully characterized. In the SLM, a high level of efficient mixing can be achieved by combining two general chaotic mixing mechanisms: splitting/recombination and chaotic advection. The splitting and recombination (in other terms, lamination) mechanism is obtained by the successive arrangement of "F"-shape mixing units in two layers. The advection is induced by the overall three-dimensional serpentine path of the microchannel. The SLM was realized by SU-8 photolithography, nickel electroplating, injection molding and thermal bonding. Mixing performance of the SLM was fully characterized numerically and experimentally. The numerical mixing simulations show that the advection acts favorably to realize the ideal vertical lamination of fluid flow. The mixing experiments based on an average mixing color intensity change of phenolphthalein show a high level of mixing performance was obtained with the SLM. Numerical and experimental results confirm that efficient mixing is successfully achieved from the SLM over the wide range of Re. Due to the simple and mass producible geometry of the efficient micromixer, SLM proposed in this study, the SLM can be easily applied to integrated microfluidic systems, such as micro-total-analysis-systems or lab-on-a-chip systems. PMID:15970967

Kim, Dong Sung; Lee, Se Hwan; Kwon, Tai Hun; Ahn, Chong H

2005-07-01

450

Lamination of the Lateral Geniculate Nucleus of Catarrhine Primates  

PubMed Central

The lateral geniculate nucleus (LGN) of catarrhines with the exception of gibbons is typically described as a six-layered structure, comprised of two ventral magnocellular layers, and four dorsal parvocellular layers. The parvocellular layers of the LGN are involved in color vision. Therefore, it is hypothesized that a six-layered LGN is a shared-derived trait among catarrhines. This might suggest that in gibbons the lack of further subdivisions of the parvocellular layers is a recent change, and could be related to specializations of visual information processing in this taxon. To address these hypotheses, the lamination of the LGN was investigated in a range of catarrhine species, including several taxa not previously described, and the evolution of the LGN was reconstructed using phylogenetic information. The findings indicate that while all catarrhine species have four parvocellular leaflets, two main patterns of LGN parvocellular lamination occur: two undivided parvocellular layers in some species, and four parvocellular leaflets (with occasional subleaflets) in other species. LGN size was not found to be related to lamination pattern. Both patterns were found to occur in divergent clades, which is suggestive of homoplasy within the catarrhines in LGN morphology. PMID:23467282

de Sousa, Alexandra A.; Sherwood, Chet C.; Hof, Patrick R.; Zilles, Karl

2013-01-01

451

Flutter of buckled shape memory alloy reinforced laminates  

NASA Astrophysics Data System (ADS)

The effect of shape memory alloys (SMA) on the linear and nonlinear flutter behaviors of buckled cross-ply and angle-ply laminates was investigated in the frequency and time domains using the finite element method. In particular, this study takes the first move toward examining the effect of varying the SMA fiber spacing. Von Karman large deformation assumptions and quasi-steady aerodynamic theory were employed. The flutter boundary, stability boundary, time history response, and phase plane plots of SMA reinforced cross-ply and angle-ply laminates are presented. The numerical results show that increase in the SMA fiber volume fraction and prestrain may generate more recovery stress, and increase the stiffness of the SMA reinforced laminates. Therefore, the flutter boundary and critical load of the plate may be increased significantly. All five types of panel behavior, namely flat, buckled, limit-cycle, periodic, and chaotic motion, are clearly displayed and successively identified. This study sheds light on improving the flutter boundary efficiently by increasing the SMA fiber volume fraction to reinforce the center of the plate.

Kuo, Shih-Yao; Shiau, Le-Chung; Lai, Chin-Hsin

2012-03-01

452

3D guided wave motion analysis on laminated composites  

NASA Astrophysics Data System (ADS)

Ultrasonic guided waves have proved useful for structural health monitoring (SHM) and nondestructive evaluation (NDE) due to their ability to propagate long distances with less energy loss compared to bulk waves and due to their sensitivity to small defects in the structure. Analysis of actively transmitted ultrasonic signals has long been used to detect and assess damage. However, there remain many challenging tasks for guided wave based SHM due to the complexity involved with propagating guided waves, especially in the case of composite materials. The multimodal nature of the ultrasonic guided waves complicates the related damage analysis. This paper presents results from parallel 3D elastodynamic finite integration technique (EFIT) simulations used to acquire 3D wave motion in the subject laminated carbon fiber reinforced polymer composites. The acquired 3D wave motion is then analyzed by frequencywavenumber analysis to study the wave propagation and interaction in the composite laminate. The frequencywavenumber analysis allows for the study of individual modes and visualization of mode conversion. Delamination damage has been incorporated into the EFIT model to generate "damaged" data. The possibility of mode isolation is also explored and potential for damage detection in laminated composites is discussed in this paper.

Tian, Zhenhua; Leckey, Cara A. C.; Yu, Lingyu

2014-02-01

453

Dual mode fracture of composite laminates penetrated by spherical projectiles  

NASA Astrophysics Data System (ADS)

The basic for delamination initiation and propagation within an impacted laminate was studied, with an explanation provided for the fracture mode transformation along the projectile's path. Post-impact observations of graphite/epoxy (AS4/3501-6) laminates penetrated by steel spheres (0.5-inch diameter) reveal a fracture mode, similar to shear plugging adjacent to the impacted surface. This fracture mode is contrasted with that of delamination adjacent to the rear surface. The sudden transition from shear plugging to delamination is believed to occur when the projectile interacts with the returning impact-generated tensile wave. To demonstrate the transition, results are presented from ballistically impacted laminates containing a series of imbedded carbon stress and constantan strain gages. Results are based on impact velocities of 1300, 1850, and 2380 f/s. Transverse stress waves are shown capable of creating delamination until attenuated by a local zone of compressed material associated with the on-coming projectile. Based on experimental results, the location of the fracture mode transition plane is predicted both graphically and through a simple equation of motion.

Czarnecki, G. J.

454

Thermoviscoelastic characterization and predictions of Kevlar/epoxy composite laminates  

SciTech Connect

This study consisted of two main parts, the thermoviscoelastic characterization of Kevlar 49/Fiberite 7714A epoxy composite lamina and the development of a numerical procedure to predict the viscoelastic response of any general laminate constructed from the same material. The four orthotropic material properties, S{sub 11}, S{sub 12}, S{sub 22}, and S{sub 66}, were characterized by 20-minute static creep tests on unidirectional ((0){sub s}, (10){sub s}, and (90){sub 16}) lamina specimens. A new numerical procedure to predict long-term laminate properties from lamina properties (obtained experimentally) was developed. Numerical instabilities and time constraints associated with viscoelastic numerical techniques were discussed and solved. The numerical procedure was incorporated into a user-friendly microcomputer program called Viscoelastic Composite Analysis Program (VCAP), which is available for IBM PC type computers. The program was designed for ease of use and includes graphics, menus, help messages, etc. The final phase of the study involved testing actual laminates constructed from the characterized material, Kevlar/epoxy, at various temperature and load levels for 4 to 5 weeks.

Gramoll, K.C.

1988-01-01

455

Buckling response of laminates with spatially varying fiber orientations  

NASA Technical Reports Server (NTRS)

The buckling response of a symmetrically laminated composite panel with a spatially varying fiber orientation has been analyzed. Variation of the fiber orientation angle as a function of the position in the panel results in a composite laminate with stiffness properties that are functions of the panel coordinates. The laminates are therefore termed variable stiffness panels. The fiber orientation is assumed to vary only in one spatial direction, although the analysis can be extended to fiber orientations that vary in two spatial directions. The Ritz Method has been used to find the buckling loads and buckling modes for the variable stiffness panels for two different cases. In one of the cases the fiber orientation is assumed to change in the direction of the applied load. The other case is the one in which the fiber orientation varies in a direction perpendicular to the loading direction. Improvements in the buckling load of up to 80 percent over straight fiber configurations were found. Results for three different panel aspect ratios are presented.

Olmedo, Reynaldo; Gurdal, Zafer

1993-01-01

456

Studies in Cup Drawing Behavior of Polymer Laminated Sheet Metal  

NASA Astrophysics Data System (ADS)

Axisymmetric deep drawing behavior of a polymer laminated sheet metal (PLSM) is investigated using an axisymmetric cup drawing test. PLSMs are of interest as a replacement for painted finishes for automotive applications as they have the potential to achieve good quality long lasting and aesthetically appealing surfaces on stamped parts. However, there is limited understanding of PLSMs in automotive deep drawing situations to produce complex 3-D parts. The tests are carried out using well-controlled, laboratory-based, dual-action, servo-hydraulic forming presses under blank-holder force and punch displacement control conditions. An optical strain mapping system is used to measure the surface strains (and to construct 3D strain maps) from the film side of the deformed samples for a range of forming conditions. Deep drawing characteristics such as punch load versus punch displacement traces, strain distribution along the cup profile, flange wrinkling and fracture characteristics are experimentally assessed for stainless steel-plastic film laminated sheet materials. Also the effect of lamination pressure on wrinkling and delamination is investigated for a decorative pressure sensitive adhesive film affixed to the stainless steel sheet.

Elnagmi, M.; Jain, M.; Bruhis, M.; Nielsen, K.

2011-08-01

457

Coupled mixed-field laminate theory and finite element for smart piezoelectric composite shell structures  

NASA Technical Reports Server (NTRS)

Mechanics for the analysis of laminated composite shells with piezoelectric actuators and sensors are presented. A new mixed-field laminate theory for piezoelectric shells is formulated in curvilinear coordinates which combines single-layer assumptions for the displacements and a layerwise representation for the electric potential. The resultant coupled governing equations for curvilinear piezoelectric laminates are described. Structural mechanics are subsequently developed and an 8-node finite-element is formulated for the static and dynamic analysis of adaptive composite structures of general laminations containing piezoelectric layers. Evaluations of the method and comparisons with reported results are presented for laminated piezoelectric-composite plates, a closed cylindrical shell with a continuous piezoceramic layer and a laminated composite semi-circular cantilever shell with discrete cylindrical piezoelectric actuators and/or sensors.

Saravanos, Dimitris A.

1996-01-01

458

Fracture mechanics of matrix cracking and delamination in glass/epoxy laminates  

NASA Technical Reports Server (NTRS)

This study focused on characterizing matrix cracking and delamination behavior in multidirectional laminates. Static tension and tension-tension fatigue tests were conducted on two different layups. Damage onset, accumulation, and residual properties were measured. Matrix cracking was shown to have a considerable influence on residual stiffness of glass epoxy laminates, and could be predicted reasonably well for cracks in 90 deg piles using a simple shear lag analysis. A fracture mechanics analysis for the strain energy release rate associated with 90 deg ply-matrix crack formation was developed and was shown to correlate the onset of 90 deg ply cracks in different laminates. The linear degradation of laminate modulus with delamination area, previously observed for graphite epoxy laminates, was predicted for glass epoxy laminates using a simple rule of mixtures analysis. The strain energy release rate associated with edge delamination formation under static and cyclic loading was difficult to analyze because of the presence of several contemporary damage phenomena.

Caslini, M.; Zanotti, C.; Obrien, T. K.

1986-01-01

459

Diatom thanatocoenosis in a middle Galician Ra: Spatial patterns and their relationship to the seasonal diatom cycle in the water column and hydrographic conditions  

NASA Astrophysics Data System (ADS)

Modern diatom distribution patterns in the surface sediment of the Ferrol Ra and their relationship to the hydrography and diatom patterns in the water column were studied to determine the hydrographic influence on the record of these biogenic components. Diatom abundance in the water column was assessed for different oceanographic periods and compared with the biosiliceous sedimentary record. Very low abundances were found in the water column during the winter, whereas in spring and summer, diatoms proliferated. Chaetoceros spp. formed the bulk of the water column community during spring and summer, followed by Thalassionema nitzschioides and Rhizosolenia spp. Nitzschia longissima represented a significant portion of the winter assemblage, together with Paralia sulcata and benthic taxa . Leptocylindrus danicus, N. longissima and Skeletonema costatum characterized the autumn campaign, when stratification of the waters occurs, with L. danicus being especially abundant in the outer ra. Seasonal hydrographic and associated productivity patterns govern the abundance and assemblage of the diatoms preserved in surface sediments. Samples located in the inner ra area and its margins exhibited the highest abundances of diatoms, and were primarily dominated by benthic species. The freshwater group, crysophycean cysts and phytoliths were present in the landward stations influenced by river runoff. The middle ra was characterized by P. sulcata and Thalassiosira spp., with minor occurrences of the benthic and freshwater group. Chaetoceros R.S., L. danicus R.S. and T. nitzschioides typified the outer ra, an assemblage that corresponds to nutrient-rich coastal areas of high productivity influenced by oceanic waters, demonstrating the impact of oceanic waters flowing into the embayment due to enhanced tidal mixing through the narrow channel. Therefore, sediment diatom assemblages reflect diatom production patterns in the water column of the Ra. However, we must proceed with caution when interpreting the paleorecord in the inner area due to the high contribution of allochthonous taxa, which is indicative of low water depths. This paper contributes to a better understanding of diatom thanatocoenosis in the Galician Ras, where very few studies of this kind have been done to date.

Bernrdez, Patricia; Prego, Ricardo; Varela, Manuel; Francs, Guillermo

2008-10-01

460

Global Expression for Representing Diatomic Potential-Energy Curves  

NASA Technical Reports Server (NTRS)

A three-parameter expression that gives an accurate fit to diatomic potential curves over the entire range of separation for charge transfers between 0 and 1. It is based on a generalization of the universal binding-energy relation of Smith et al. (1989) with a modification that describes the crossover from a partially ionic state to the neutral state at large separations. The expression is tested by comparison with first-principles calculations of the potential curves ranging from covalently bonded to ionically bonded. The expression is also used to calculate spectroscopic constants form a curve fit to the first-principles curves. A comparison is made with experimental values of the spectroscopic constants.

Ferrante, John; Schlosser, Herbert; Smith, John R.

1991-01-01

461

Spectral analysis of two coupled diatomic rotor molecules.  

PubMed

In a previous article the theory of frame transformation relation between Body Oriented Angular (BOA) states and Lab Weakly Coupled states (LWC) was developed to investigate simple rotor-rotor interactions. By analyzing the quantum spectrum for two coupled diatomic molecules and comparing it with spectrum and probability distribution of simple models, evidence was found that, as we move from a LWC state to a strongly coupled state, a single rotor emerges in the strong limit. In the low coupling, the spectrum was quadratic which indicates the degree of floppiness in the rotor-rotor system. However in the high coupling behavior it was found that the spectrum was linear which corresponds to a rotor deep in a well. PMID:25353181

Crogman, Horace T; Harter, William G

2014-01-01

462

Atom-diatom scattering dynamics of spinning molecules.  

PubMed

We present full quantum mechanical scattering calculations using spinning molecules as target states for nuclear spin selective atom-diatom scattering of reactive D+H2 and F+H2 collisions. Molecules can be forced to rotate uni-directionally by chiral trains of short, non-resonant laser pulses, with different nuclear spin isomers rotating in opposite directions. The calculations we present are based on rotational wavepackets that can be crea