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1

Diatom Ooze: Ooze Clues  

NSDL National Science Digital Library

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

Lawrence, Lisa A.

2014-04-08

2

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

3

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

4

Diatoms  

Microsoft Academic Search

The basic requirements for diatom analysis have changed little over the last few decades in terms of sampling, slide preparation,\\u000a microscopy and taxonomy but, on the other hand, there have been major improvements in our knowledge of diatom distribution\\u000a and ecology and a revolution in our ability to analyse diatom data. These changes have been driven by the increasing recognition

Richard W. Battarbee; Vivienne J. Jones; Roger J. Flower; Nigel G. Cameron; Helen Bennion; Laurence Carvalho; Stephen Juggins

5

Late Holocene climate of the Eastern Mediterranean inferred from diatom analysis of annually-laminated lake sediments  

NASA Astrophysics Data System (ADS)

Diatoms from the annually-laminated sediments of Nar crater lake in central Turkey are used to investigate climatic changes throughout the last 1720 years at decadal time resolution. A diatom-conductivity transfer function is employed to infer past water balance. Further information has been extracted from the palaeo-record through calculation of diatom biovolume, rarefaction (species diversity) and concentration, and through the identification of diatom bloom events in core thin sections. The Nar diatom sequence is compared with oxygen isotope (? 18O) and pollen records from the same sediment cores in order to test the respective roles of changes in climate and land cover. Diatom-inferred (DI) conductivity excluding bloom taxa and ? 18O show very good correspondence for the first half of the record and demonstrate that this region experienced a period of century-scale drought prior to AD 540, with a subsequent rapid and simultaneous shift to fresher lake conditions and wetter climate. After a drier phase in the Nar record from AD 800-950, the period of the Medieval Climate Anomaly (AD 950-1400) was generally well watered. During the subsequent Little Ice Age (˜AD 1700-1900), DI-conductivity and ? 18O become decoupled. Thin sections reveal between 20 and 40 distinct diatom bloom events per century since AD 1100, with increasing frequency between AD 1700 and 2000. Human land-use changes evident in the pollen sequence may have influenced the diatom relationship with lake water conductivity in the later part of the record. None the less, diatom DCA axes do show a clear response to multi-decadal drought events within the last six centuries. Differences between the proxy-climate records from Nar Lake may be associated with the dissimilar thresholds to environmental fluctuations and non-stationarity in the response of different proxies through time. The palaeoclimate records from Nar show that arid periods occurred in the Eastern Mediterranean during the last two millennia that were more prolonged and extreme than those experienced in the last century.

Woodbridge, Jessie; Roberts, Neil

2011-11-01

6

The occurrence of triglycerides in Namibian Shelf diatomaceous ooze  

NASA Astrophysics Data System (ADS)

The triglyceride fraction, isolated from extractable lipids of a diatomaceous ooze off shore Walvis Bay (S.W. Africa) by TLC methods, was analyzed by direct probe low and high resolution mass spectrometry. The mass spectral data reveal the fatty acid moieties and their relative distribution in the triglycerides identified. The C 12, C 14, C 15 and C 16 are the major composing fatty acid moieties. The triglycerides are thought to be present in protective structures such as diatom spores, which were found to be present by scanning electron microscopy.

Boon, Jaap J.; Irene, W.; Rijpstra, C.; de Leeuw, J. W.; Burlingame, A. L.

1980-01-01

7

Late Neogene paleoceanography of the Sea of Japan based upon diatoms  

SciTech Connect

The authors identified several time intervals apparent late Neogene stepwise paleoenvironmental change in the southern Sea of Japan. The paleoenvironment of the middle Pliocene and older sediments cannot be characterized because the diatom assemblage is made up of a near monospecific ooze (Coscinodiscus marginatus). The middle Pliocene, prior to 2.4 Ma but after the deposition of the C. marginatus ooze, is characterized by warm water diatoms while the late Pliocene (between approximately 2.4 my and the Pliocene/Pleistocene boundary) is characterized by cool water diatoms belonging to an upwelling assemblage. The Tsushima Strait became emergent at approximately 2.4 Ma owing to sea level drop caused by initiation of continental ice build-up on Greenland and by ongoing tectonic uplift across the southern part of Honshu. Diatoms deposited above the Pliocene/Pleistocene boundary suggest that the Tsushima Strait was again submergent and that a branch of the Kuroshio Current flowed into the Sea of Japan. The early Quaternary is characterized by variable preservation and abundance of diatoms with warm water species predominating. They observed changes in both diatom abundance and preservation in upper Quaternary sediments, probably reflecting changes in productivity induced by major glacial/interglacial oscillations. They found no evidence of the complete isolation of the Sea of Japan from the Pacific but their data do suggest, at least, constriction of the Tsushima Strait during maximum glacial episodes. The late Pliocene-Pleistocene interval is characterized by alternating intervals of laminated/homogenous sediments. There are some 30 laminated intervals within the last 300 kyr suggesting that this signal may be the second harmonic of precession. The laminated layers may reflect salinity changes in the southern Sea of Japan.

Burkle, L.H. (Lamont-Doherty Geological Observatory Palisades, NY (USA))

1990-06-01

8

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

9

Experimental Formation of Chalk from Calcareous Ooze. Technical Progress Report.  

National Technical Information Service (NTIS)

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

W. E. Seyfried T. C. Johnson

1981-01-01

10

Experimental formation of chalk from calcareous ooze. Technical progress report  

SciTech Connect

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

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

1981-02-15

11

Onset and termination of the late-glacial climate reversal in the high-resolution diatom and sedimentary records from the annually laminated SG06 core from Lake Suigetsu, Japan  

Microsoft Academic Search

High-resolution diatom, sediment and pollen analyses of two sections from the annually laminated SG06 core from Lake Suigetsu were used to study the onset and termination of the late-glacial climate reversal in central Japan. Its broadly recognised counterpart is the Younger Dryas or Greenland Stadial-1 (ca. 12.85–11.65cal. kyr BP based on the NGRIP ice core records). Our study suggests that

Annette Kossler; Pavel Tarasov; Gordon Schlolaut; Takeshi Nakagawa; Michael Marshall; Achim Brauer; Christopher Bronk Ramsey; Charlotte Bryant; Henry Lamb; Dieter Demske; Katsuya Gotanda; Tsuyoshi Haraguchi; Yusuke Yokoyama; Hitoshi Yonenobu; Ryuji Tada

2011-01-01

12

Erodibility of pelagic carbonate ooze in the northeast Atlantic  

Microsoft Academic Search

Shipboard erosion experiments were conducted on retrieved carbonate ooze sediments using the suction-stirring flume instrument of Gust and Muller [Gust, G., Muller, V., 1997. Interfacial hydrodynamics and entertainment functions of currently used erosion devices. Burt, N.T., et al. (Eds.) Cohesive Sediments. Wiley, Chichester, pp. 149–176] at two differing localities (site A, 3800 m water depth; site B, 1100 m water

K. S Black; O. C Peppe; G Gust

2003-01-01

13

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

14

The use of oxygen isotopes of diatom silica in a decadal to centennial palaeonvironmental reconstruction  

NASA Astrophysics Data System (ADS)

The Lateglacial-early Holocene transition from the Lago Chungará record (northern Chilean Altiplano) is made up of laminated sediments composed by light and dark pluriannual couplets of diatomaceous ooze. Light sediment laminae accumulated during short-term diatom blooms whereas dark sediment laminae represent the baseline limnological conditions during several years of deposition. Diatom oxygen isotope data (_18Odiatom) of dark diatom laminae from Lago Chungará show evidence that the Lateglacial-early Holocene transition (11,990-11,475 cal years BP) occurred in a series of decadal-to-centennial wet-dry oscillations. Dry periods are marked by relatively high isotope values whereas wet episodes are indicated by lower isotope values. This fact is supported by data on allochtonous inputs and water availability curves from Lago Chungará previously published (Giralt et al. 2008). They highlight the sedimentological and environmental processes that occurred during these wet and dry episodes. The delta_18Odiatom record documents at least two episodes of increased effective moisture at a centennial-scale (ca.11,800 and 11,550 cal years BP) and only one important period of increasing aridity (between ca. 11,990 and 11,800 cal years BP). However, up to seven wet episodes and at least six dry events at a decadal scale are superimposed to the normal conditions. The spectral analyses of the delta_18Odiatom values suggest that these changes could be triggered by both El Niño-Southern Oscillation (ENSO) and solar activity. Time-frequency analysis shows that the activity of these two forcings was more intense during Lateglacial than during the onset of the Holocene. This last period could be governed by La Niña-like conditions that correspond to wet conditions over the Andean Altiplano.

Hernández, A.; Giralt, S.; Bao, R.; Sáez, A.; Leng, M. J.; Barker, P. A.

2009-04-01

15

Experimental Formation of Chalk from Calcareous Ooze. Final Report, February 15, 1981-October 14, 1983.  

National Technical Information Service (NTIS)

Hydrothermal experiments on three calcareous oozes of different compositions were performed at the University of Minnesota in a flow-through apparatus and a squeezer assembly. Both apparati allow unconsolidated sediment to be compacted and dewatered in th...

W. E. Seyfried T. C. Johnson

1983-01-01

16

Early Holocene decadal-scale ocean variability recorded in Gulf of California laminated sediments  

Microsoft Academic Search

Scanning electron microscope examination of Holocene laminated sediment from Guaymas Basin, Gulf of California, resolves up to five depositional events per year. Each lamina\\/sublamina of an early Holocene section of continuously laminated sediment was recorded from backscattered electron imagery photomosaic analysis. Diatom mat laminae, composed predominantly of Thalassiothrix longissima, are associated with early winter mixed diatom flora laminae. Mats are

Jennifer Pike; Alan E. S. Kemp

1997-01-01

17

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

18

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

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

19

Nuclear Lamins  

PubMed Central

The nuclear lamins are type V intermediate filament proteins that are critically important for the structural properties of the nucleus. In addition, they are involved in the regulation of numerous nuclear processes, including DNA replication, transcription and chromatin organization. The developmentally regulated expression of lamins suggests that they are involved in cellular differentiation. Their assembly dynamic properties throughout the cell cycle, particularly in mitosis, are influenced by posttranslational modifications. Lamins may regulate nuclear functions by direct interactions with chromatin and determining the spatial organization of chromosomes within the nuclear space. They may also regulate chromatin functions by interacting with factors that epigenetically modify the chromatin or directly regulate replication or transcription.

Dechat, Thomas; Adam, Stephen A.; Taimen, Pekka; Shimi, Takeshi; Goldman, Robert D.

2010-01-01

20

Laminate Stiffnesses and Classical Laminate Theory.  

National Technical Information Service (NTIS)

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

J. W. Gunnink

1985-01-01

21

Lipid Components of Diatoms.  

National Technical Information Service (NTIS)

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

M. Kates B. E. Volcani

1965-01-01

22

Frictional properties of silicic to calcareous ooze on the Cocos Plate entering the Costa Rica Subduction Zone  

NASA Astrophysics Data System (ADS)

Here we report experimental results on the frictional properties of the cover sediments on the Cocos plate incoming into the erosive Costa Rica subduction zone. Mechanical properties of the incoming sediments to subduction plate boundaries are essential to constrain subduction-related faulting processes. However, knowledge of the frictional properties of sediments composed of abundant biogenic component, such as spicules, diatoms, and radiolarians are limited. Experimental samples were silicic to calcareous ooze collected at a reference site (Site U1381) off shore Osa Peninsula during IODP Expedition 334 (Vannucchi et al., 2012). To be used in the experiments, the discrete samples was disaggregated, oven dried at 60 degrees centigrade for 24 hours. The experimental fault is composed of a 24.9 mm diameter cylinder of gabbro cut perpendicularly to the cylinder axis in two halves that are ground to obtain rough wall surfaces, and re-assembled with an intervening thin layer (~1.0 mm) disaggregated sample. Frictional experiments have been performed using a rotary-shear friction testing machine, at normal stresses up to 5 MPa, over a range of slip velocities from 0.0026 mm/s to 1.3 m/s, with more than ~150 mm of displacements for water saturated condition. Experimental results reveal that friction values at slow slip velocities (v < ~30 mm/s) are about ~0.7, of which level is comparable to the typically reported friction values for rocks. The experimental faults exhibited velocity-weakening at v < 0.3 mm/s and neutral to velocity-strengthening at 0.3 < v < ~3 mm/s. At higher velocities (v > ~30 mm/s), steady state friction decreases dramatically. For example, at a velocity of 260 mm/s, the friction coefficient for samples U1381A-9R and -10R show a gradual decrease with a large weakening displacement toward the establishment of a nearly constant level of friction at ~0.1. The velocity weakening behavior at slow velocities could provide a condition to initiate unstable fault motion at shallow depths along the subduction channel if the input sediments are incorporated into faulting. On the contrary, neutral to velocity strengthening behavior observed for intermediate velocities could stabilize the propagation process of earthquake nuclei that emerges in the velocity weakening portion along the fault. It is important to note also that a dramatic slip weakening at velocities of v > ~30 mm/s characterizes the frictional behavior of the examined input sediments to the Costa Rica subduction zone. The relatively slower velocity condition for the onset of high-velocity weakening and the extremely low friction values (~0.1) observed at high velocities are comparable to the frictional properties reported for silicic fault (e.g., Goldsby and Tullis, 2002, GRL; Hayashi and Tsutsumi, 2010,GRL). Presented frictional properties of the incoming sediments may offer an important constraint for improving models of subduction-related faulting processes within the Costa Rica subduction channel.

Tsutsumi, A.; Kameda, J.; Ujiie, K.

2012-12-01

23

Beyond Lamins  

Microsoft Academic Search

The nucleus is bordered by a double bilayer nuclear envelope, communicates with the cytoplasm via embedded nuclear pore complexes, and is structurally supported by an underlying nucleoskeleton. The nucleoskeleton includes nuclear intermediate filaments formed by lamin proteins, which provide major structural and mechanical support to the nucleus. However, other structural proteins also contribute to the function of the nucleoskeleton and

Zhixia Zhong; Katherine L. Wilson; Kris Noel Dahl

2010-01-01

24

Investigation of Laminating Effects in Glued-Laminated Timber.  

National Technical Information Service (NTIS)

In this study, existing lamination and beam test results were analytically reviewed in an attempt to quantify the laminating effect for glued-laminated (glulam) timber. Laminating effect is defined as the increase in strength of lumber laminations when bo...

F. Colling, R. H. Falk

1994-01-01

25

Hybrid Composite Laminate Structures.  

National Technical Information Service (NTIS)

The invention is related to laminate structures and specifically to essentially anisotropic fiber composite laminates. Metal foils are selectively disposed within the laminate to produce increased resistance to high velocity impact, fracture, surface eros...

C. C. Chamis R. F. Lark

1975-01-01

26

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

SciTech Connect

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

Schmidt, R.L.

1982-04-01

27

DIATOM: A DIALOG Simulator.  

ERIC Educational Resources Information Center

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

Waldstein, Robert

1981-01-01

28

Diatoms in comets  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

29

Synthesis of Diatomic Radicals.  

National Technical Information Service (NTIS)

Free diatomic radicals, studied for many years by the methods of optical spectroscopy, have mostly resisted similar attempts to observe their microwave spectra. Lacking has been a systematic method of producing and maintaining cool, reasonably dense, gase...

H. E. Radford

1964-01-01

30

Environmental investigations using diatom microfossils  

USGS Publications Warehouse

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

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

2010-01-01

31

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

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.

2011-01-01

33

Laminating Polyimide Films  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

34

Distribution of diatom surface sediment assemblages within Effingham Inlet, a temperate fjord on the west coast of Vancouver Island (Canada)  

Microsoft Academic Search

Twenty-nine surface sediment samples from Effingham Inlet, a small fjord on the west coast of Vancouver Island, British Columbia, were analyzed for diatoms. This fjord has been selected for paleoceanographic investigation due to the presence of laminated sediments resulting from the dysoxic to anoxic bottom water conditions in the inner and outer basins of the inlet. Distributional patterns of the

Murray B Hay; Reinhard Pienitz; Richard E Thomson

2003-01-01

35

Interactions between Diatoms and Bacteria  

PubMed Central

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

Amin, Shady A.; Parker, Micaela S.

2012-01-01

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.

1972-01-01

37

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

38

Honeycomb-laminate composite structure  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

39

DNA Damage and Lamins  

PubMed Central

The spatial and temporal organization of the genome has emerged as an additional level of regulation of nuclear functions. Structural proteins associated with the nuclear envelope play important roles in the organization of the genome. The nuclear lamina, a polymeric meshwork formed by lamins (A- and B-type) and lamin-associated proteins, is viewed as a scaffold for tethering chromatin and protein complexes regulating a variety of nuclear functions. Alterations in lamins function impact DNA transactions such as transcription, replication, and repair, as well as epigenetic modifications that change chromatin structure. These data, and the association of defective lamins with a whole variety of degenerative disorders, premature aging syndromes, and cancer, provide evidence for these proteins operating as caretakers of the genome. In this chapter, we summarize current knowledge about the function of lamins in the maintenance of genome integrity, with special emphasis on the role of A-type lamins in the maintenance of telomere homeostasis and mechanisms of DNA damage repair. These findings have begun to shed some light onto molecular mechanisms by which alterations in A-type lamins induce genomic instability and contribute to the pathophysiology of aging and aging-related diseases, especially cancer.

Gonzalo, Susana

2014-01-01

40

SILICON METABOLISM IN DIATOMS  

PubMed Central

1. Cells of the fresh water diatom Navicula pelliculosa may be grown in a mineral medium containing a low concentration of silicon. When transferred to a fresh silicate solution and incubated under non-growing conditions such deficient cells rapidly take up silicon from the medium. 2. The utilization of silicon is an aerobic process. 3. When deficient cells are washed with distilled water or saline, their ability to utilize silicon is impaired whereas respiration is unaffected. 4. The ability of washed cells to take up silicon can be partially restored with sulfate or ascorbic acid, and is completely restored by Na2S, Na2S2O3, glutathione, l-cysteine, dl-methionine, or ascorbic acid plus sulfate. 5. The sulfhydryl reagent, CdCl2, inhibits silicon utilization of unwashed cells at concentrations which do not affect respiration. This inhibition similarly is reversed by glutathione or cysteine. 6. However, sodium iodoacetate or sodium arsenite inhibits respiration and silicon utilization at the same concentrations. 7. The silicon taken up by deficient cells is deposited at the cell surface as a thickening of the existing silica frustules. 8. Sulfhydryl groups in the cell membrane may be involved in silicon uptake by diatoms.

Lewin, Joyce C.

1954-01-01

41

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

42

Laminated Damped Fuselage Structures.  

National Technical Information Service (NTIS)

This paper discusses the application of constrained layer damping, in the form of laminated skins, frames, and equipment racks, to control of acoustical fatigue of structures and vibration of equipment in the aft fuselage sections of large aircraft. Discu...

R. A. Ely

1984-01-01

43

The lamin protein family  

Microsoft Academic Search

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

Travis Dittmer; Tom Misteli

2011-01-01

44

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)

2012-06-19

45

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

46

Marine Polymers. IV, Diatom Polysaccharides.  

National Technical Information Service (NTIS)

Part of a program designed to investigate the properties and utilization of marine-derived polymers, this study is a preliminary examination of the polysaccharide constituents of a number of diatom species. The objective was to identify and characterize t...

G. G. Allans J. Lewin P. G. Johnson

1971-01-01

47

Stuart R. Stidolph diatom atlas  

USGS Publications Warehouse

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

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

2012-01-01

48

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.

Institute, Lunar A.

2010-01-01

49

Laminate armor and related methods  

DOEpatents

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

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

2013-02-26

50

Dissociation of diatomic gases  

NASA Technical Reports Server (NTRS)

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

Hansen, C. F.

1991-01-01

51

Diatoms: Powerful Indicators of Environmental Change.  

National Technical Information Service (NTIS)

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

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

1992-01-01

52

Marine Diatom Plasmids and their Biotechnological Applications.  

National Technical Information Service (NTIS)

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

F. G. Plumley

1992-01-01

53

Fatigue Failure of Laminates.  

National Technical Information Service (NTIS)

A previously developed fatigue failure criterion for laminae in state of plane stress is used to establish a failure criterion for first fatigue failure of balanced laminates. An extensive tension-tension fatigue testing program for E-glass/Epoxy angle-pl...

A. Rotem Z. Hashin

1975-01-01

54

Previously Unknown Virus Infects Marine Diatom  

Microsoft Academic Search

Diatoms are a major phytoplankton group that play important roles in maintaining oxygen levels in the atmosphere and sustaining the primary nutritional production of the aquatic environment. Among diatoms, the genus Chaetoceros is one of the most abundant and widespread. Temperature, climate, salinity, nutrients, and predators were regarded as important factors controlling the abundance and population dynamics of diatoms. Here

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

2005-01-01

55

The Diatom Collection of the California Academy of Sciences  

NSDL National Science Digital Library

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

56

Luminescence properties of a nanoporous freshwater diatom.  

PubMed

Freshwater diatom frustules show special optical properties. In this paper we observed luminescence properties of the freshwater diatom Cyclotella meneghiniana. To confirm the morphological properties we present scanning electron microscopy (SEM) images. X-ray diffraction (XRD) studies were carried out to visualize the structural properties of the frustules, confirming that silica present in diatom frustules crystallizes in an ?-quartz structure. Study of the optical properties of the silica frustules of diatoms using ultra-violet-visible (UV-vis) spectroscopy and photoluminescence spectroscopy confirmed that the diatom C. meneghiniana shows luminescence in the blue region of the electromagnetic spectrum when irradiated with UV light. This property of diatoms can be exploited to obtain many applications in day-to-day life. Also, using time-resolved photoluminescence spectroscopy (TRPL) it was confirmed that this species of diatom shows bi-exponential decay. PMID:21618682

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

2012-01-01

57

Dead Diatoms Do Tell Tales  

NSDL National Science Digital Library

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

Dahlman, Luann; Andrill

58

Heteronuclear Diatomic Molecular Orbital Formation  

NSDL National Science Digital Library

Here is a set of movies that demonstrates heteronuclear diatomic molecular orbital formation. The orbitals start at a distance where there is little or no interatomic interaction and move to the appropriate bond distance. Orbital phase is shown by the different colors.

59

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

60

Dynamics of heterogeneous laminates  

NASA Astrophysics Data System (ADS)

Dielectric relaxation spectroscopy (DRS) was used to assess the dynamics of molecules in the heterogeneous laminate configuration and any practical applications that the arrangement may offer. Two component systems were considered. One of the components was an insulator and served as a barrier layer between the other component and the electrode. Of particular interest was the interpretation of the anomalous polarization phenomena that occurred due to the heterogeneity of the system. It was found that the relaxation processes that manifested as a result of the system being heterogeneous were unique to the material being studied. The cautionary use of effective medium approximations to predict the behaviour of the anomalous polarization phenomena was prescribed. In developing a molecular interpretation of the anomalous polarization processes all the parameters of the Havriliak-Negami equation were employed to ascertain physical aspects of the dielectric relaxation. The anomalous relaxation processes in the heterogeneous laminate configuration was due to the migration of charge that was facilitated by associative dipoles such as hydrogen bonds or ? interactions for example. It was found that surfaces have a discernible effect on the bulk dynamics of a material because the barrier layer controlled the rate at which charge was removed from the material. The heterogeneous laminate configuration showed promise as a simple alternative to assess the effects of spatial limitations on the dynamics of a molecule. In addition to the assessment of relaxation mechanisms of the charge migration processes in a material, the heterogeneous laminate configuration is recommended for studying molecules of a highly conducting nature without the need for indirect methods of extracting molecular dynamics.

McKenzie, Ruel

61

Laminated Fresnel lenses  

SciTech Connect

A fabrication method for making plastic-on-glass laminated Fresnel lenses is discussed. These Fresnel lenses are for application in an RCA solar photovoltaic concentrator array now in the prototype stage of development. This laminated Fresnel lens fabrication method consists of making a Dow Corning J RTV silastic rubber mold of a master lens array. This mold is used to vacuum cast only the lens facets onto a low-iron tempered-glass substrate with an epoxy resin such as Hysol 0S 1000, a bisphenol-A resin with a flexibilizer that is anhydride cured. Cast acrylic Fresnel lens arrays commercialy available have potential cleaning and abrasion problems, have very large thermal expansion, and have dimensional uncertainties in their manufacture. The laminated lens is dimensionally stable with low thermal expansion, has good cleaning characteristics, and is very inexpensive in materials cost. The measured transmission of such a lens on low-iron glass is 80.4% compared with 85.1% for a cast acrylic lens, and the optical quality is good enough for application in the 100X to 200X concentration range. An approach to making large lens arrays (3 by 6 ft) on a commercial scale is explored.

Jebens, R.W.

1980-04-01

62

THERMOELASTIC ANALYSIS OF LAMINATED PLATES. I: SYMMETRIC SPECIALLY ORTHOTROPIC LAMINATES  

Microsoft Academic Search

Thermally induced deformations and stress resultants in symmetric laminated plates are analyzed. The method of M. Levy is used to study the transverse bending of a specially orthotropic laminate having two simply supported edges and subject to a temperature distribution that does not vary in a direction parallel to the simple supports. A solution is also obtained for the problem

C. H. Wu; T. R. Tauchert

1980-01-01

63

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

64

Optimization of composite laminates  

NASA Technical Reports Server (NTRS)

Design of composite structures can be viewed as a multi-faceted task, one which requires integration of issues related to composite mechanics, structural analysis, optimization, and manufacturing. The major coverage of the paper is on the issue of optimization, with special emphasis on the use of optimization for designing with discrete and integer valued variables required for the stacking-sequence optimization. Different techniques that can be used for stacking sequence optimization are introduced, and different aspects of their application are demonstrated for laminate buckling optimization.

Gurdal, Zafer; Haftka, Raphael T.

1993-01-01

65

Laminated, composite flywheel failure analysis  

NASA Astrophysics Data System (ADS)

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

Nimmer, R. P.

1980-06-01

66

Honeycomb-Laminate Composite Structure.  

National Technical Information Service (NTIS)

A honeycomb-laminate composite structure comprising: (1) a cellular core of a polyquinoxaline foam in a honeycomb structure, and (2) a layer of a non-combustible fibrous material impregnated with a polyimide resin laminated on the cellular core, is descri...

W. J. Gilwee J. A. Parker

1976-01-01

67

Nonlinear analysis of composite laminates  

Microsoft Academic Search

Nonlinear static and dynamic responses of composite laminates were investigated using the finite element method. A nine-node isoparametric quadrilateral element was developed to formulate the finite element equations for a laminated plate under initial deformations and initial stresses according to the Mindlin plate theory and von Karman large deflection assumptions. Static large deflection and postbuckling of plates, impact response of

1984-01-01

68

Studying lamins in invertebrate models.  

PubMed

Lamins are nuclear intermediate filament proteins that are conserved in all multicellular animals. Proteins that resemble lamins are also found in unicellular organisms and in plants. Lamins form a proteinaceous meshwork that outlines the nucleoplasmic side of the inner nuclear membrane, while a small fraction of lamin molecules is also present in the nucleoplasm. They provide structural support for the nucleus and help regulate many other nuclear activities. Much of our knowledge on the function of nuclear lamins and their associated proteins comes from studies in invertebrate organisms and specifically in the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster. The simpler lamin system and the powerful genetic tools offered by these model organisms greatly promote such studies. Here we provide an overview of recent advances in the biology of invertebrate nuclear lamins, with special emphasis on their assembly, cellular functions and as models for studying the molecular basis underlying the pathology of human heritable diseases caused by mutations in lamins A/C. PMID:24563351

Lyakhovetsky, Roman; Gruenbaum, Yosef

2014-01-01

69

Laminated, Composite Flywheel Failure Analysis.  

National Technical Information Service (NTIS)

A hybrid, composite flywheel, composed of a laminated, flat S2-glass central disc, with a filament wound, graphite outer ring, has been proposed for vehicle application. The failure mechanism of the laminated central disc of this hybrid design is discusse...

R. P. Nimmer

1980-01-01

70

Diatom Paleolimnology Data Cooperative Home Page  

NSDL National Science Digital Library

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

1998-01-01

71

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

72

Charge formation in PE\\/Polymer laminates  

Microsoft Academic Search

PE (polyethylene)\\/PE laminates were selected as test specimens to simulate the interface of blends, and their charge formation characteristics have been investigated. Charge behavior in PE\\/polymer laminates is shown to differ depending on the type of laminates. In laminates with PE and EVA, the charge tends to be trapped in the PE component and migrate through the interface relatively freely.

K. S. Suh; J. J. Lee; T. Takada

1993-01-01

73

Lamins in development, tissue maintenance and stress  

PubMed Central

Lamins are nuclear intermediate filament proteins. They provide mechanical stability, organize chromatin and regulate transcription, replication, nuclear assembly and nuclear positioning. Recent studies provide new insights into the role of lamins in development, differentiation and tissue response to mechanical, reactive oxygen species and thermal stresses. These studies also propose the existence of separate filament networks for A- and B-type lamins and identify new roles for the different networks. Furthermore, they show changes in lamin composition in different cell types, propose explanations for the more than 14 distinct human diseases caused by lamin A and lamin C mutations and propose a role for lamin B1 in these diseases.

Zuela, Noam; Bar, Daniel Z; Gruenbaum, Yosef

2012-01-01

74

Assessing subglacial processes from diatom fragmentation patterns  

USGS Publications Warehouse

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

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

2004-01-01

75

Design Studies of Primary Aircraft Structures in ARALL (Aramid Reinforced Aluminum Laminates) Laminates,  

National Technical Information Service (NTIS)

Comparison of Aramid Reinforced Aluminum Laminates (ARALL) laminates on a structural level with other aircraft materials shows that ARALL laminate is a very attractive material, especially for fatigue-dominated structural parts, like the lower wing and th...

J. W. Gunnink

1987-01-01

76

Molecular regulation of the diatom cell cycle.  

PubMed

Accounting for almost one-fifth of the primary production on Earth, the unicellular eukaryotic group of diatoms plays a key ecological and biogeochemical role in our contemporary oceans. Furthermore, as producers of various lipids and pigments, and characterized by their finely ornamented silica cell wall, diatoms hold great promise for different industrial fields, including biofuel production, nanotechnology, and pharmaceutics. However, in spite of their major ecological importance and their high commercial value, little is known about the mechanisms that control the diatom life and cell cycle. To date, both microscopic and genomic analyses have revealed that diatoms exhibit specific and unique mechanisms of cell division compared with those found in the classical model organisms. Here, we review the structural peculiarities of diatom cell proliferation, highlight the regulation of their major cell cycle checkpoints by environmental factors, and discuss recent progress in molecular cell division research. PMID:24277280

Huysman, Marie J J; Vyverman, Wim; De Veylder, Lieven

2014-06-01

77

Postbuckling of Laminated Anisotropic Panels.  

National Technical Information Service (NTIS)

A two-part study of the buckling and postbuckling of laminated anisotropic plates with bending-extensional coupling is presented. The first part involves the development and application of a modified Rayleigh-Ritz analysis technique. Modifications made to...

G. L. Jeffrey

1987-01-01

78

Internal stresses in laminated construction  

NASA Technical Reports Server (NTRS)

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

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

1923-01-01

79

Sudden bending of cracked laminates  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

80

Internal Stresses in Laminated Construction  

NASA Technical Reports Server (NTRS)

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

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

1923-01-01

81

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

82

Superplasticity in laminated metal composites  

Microsoft Academic Search

Several studies have shown the possibility of achieving superplastic behavior in laminated metal composites consisting of alternating ;\\u000alayers of superplastic and non-superplastic materials. Achieving high rate sensitivity in such a laminate requires the appropriate choice of ;\\u000acomponent materials and component volume fraction as well as deformation under appropriate conditions of strain rate and temperature. The ;\\u000afirst investigators

D. Lesuer; O. Sherby; C. Syn

1998-01-01

83

Electronic spectroscopy of diatomic molecules  

NASA Technical Reports Server (NTRS)

This article provides an overview of the principal computational approaches and their accuracy for the study of electronic spectroscopy of diatomic molecules. We include a number of examples from our work that illustrate the range of application. We show how full configuration interaction benchmark calculations were instrumental in improving the understanding of the computational requirements for obtaining accurate results for diatomic spectroscopy. With this understanding it is now possible to compute radiative lifetimes accurate to within 10% for systems involving first- and second-row atoms. We consider the determination of the infrared vibrational transition probabilities for the ground states of SiO and NO, based on a globally accurate dipole moment function. We show how we were able to assign the a(sup "5)II state of CO as the upper state in the recently observed emission bands of CO in an Ar matrix. We next discuss the assignment of the photoelectron detachment spectra of NO and the alkali oxide negative ions. We then present several examples illustrating the state-of-the-art in determining radiative lifetimes for valence-valence and valence-Rydberg transitions. We next compare the molecular spectroscopy of the valence isoelectronic B2, Al2, and AlB molecules. The final examples consider systems involving transition metal atoms, which illustrate the difficulty in describing states with different numbers of d electrons.

Partridge, Harry; Langhoff, Stephen R.; Bauschlicher, Charles W., Jr.

1994-01-01

84

The Phaeodactylum genome reveals the evolutionary history of diatom genomes  

Microsoft Academic Search

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

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

2008-01-01

85

Diatom Community Response to Global Change  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

86

Calculation of the Room-Temperature Shapes of Unsymmetric Laminates.  

National Technical Information Service (NTIS)

The cured shape of unsymmetric laminates do not always conform to the predictions of classical lamination theory. Classical lamination theory predicts the room-temperature shapes of all unsymmetric laminates to be a saddle. Experimental observations, howe...

M. W. Hyer

1981-01-01

87

Structural Strength and Deformation of Glass-Reinforced Laminates.  

National Technical Information Service (NTIS)

Contents: Structural glass-reinforced laminates; The elastic properties of glass-reinforced laminates; Strength properties of glass-reinforced laminates; Effect of time on the deformation and strength of glass-reinforced laminates; The temperature effect ...

Y. M. Tarnopolskii A. M. Skudra

1974-01-01

88

Diatoms.  

ERIC Educational Resources Information Center

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

Hungerford, James J.

1988-01-01

89

Effects of pesticides on freshwater diatoms.  

PubMed

The study of pesticide effects on algae, and diatoms in particular, was focused on photosynthesis and biomass growth disturbances. Few studies have been performed to investigate the effects of these toxic agents on intracellular structures of diatom cells. Nuclear alterations and cell wall abnormalities were reported for diatoms exposed to toxic compounds. Nevertheless, the cellular mechanisms implicated in the development of such alterations and abnormalities remain unclear. Sensitivity to pesticides is known to be quite different among different diatom species. Eutrophic and small species are recognized for their tolerance to pesticides exposure. More pronounced cell defenses against oxidative stress may explain this absence of sensitivity in species of smaller physical size. Notwithstanding, on the whole, explaining the rationale behind tolerance variations among species has been quite difficult, thus far. In this context, the understanding of intracellular toxicity in diatoms and the relation between these intracellular effects and the disturbance of species composition in communities represent a key target for further research. The original community species structure determines the response of a diatom community to toxic agent exposure. Diatom communities that have species capable of switching from autotrophic to heterotrophic modes, when photosynthesis is inhibited (e.g., after pesticide exposure), can continue to grow, even in the presence of high pesticide pollution. How diatoms respond to toxic stress, and the degree to which they respond, also depends on cell and community health, on ecological interactions with other organisms, and on general environmental conditions. The general structural parameters of diatom communities (biomass, global cell density) are less sensitive to pesticide effects than are the specific structural parameters of the unicellular organisms themselves (cell density by species, species composition). For benthic species, biofilm development and grazing on this matrix as a source of food for invertebrates and fishes may also modify the response of diatom communities. Environmental parameters (light exposure, nutrient concentrations, and hydraulic conditions) affect, and often interfere with, the response of diatoms to pesticides. Therefore, the complexity of aquatic ecosystems and the complexity of pesticide to easily detect the effects of such pollutants on diatoms. Clearly more research will be required to address this problem. PMID:19957117

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

2010-01-01

90

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

91

Electronic spectroscopy of diatomic VC.  

PubMed

Resonant two-photon ionization spectroscopy has been applied to diatomic VC, providing the first optical spectrum of this molecule. The ground state is determined to be a (2)?3/2 state that arises from the 1?(2)1?(4)2?(2)1?(1) configuration. The r0" ground-state bond length is 1.6167(3) Å. The manifold of excited vibronic states in the visible portion of the spectrum is quite dense, but two possible vibrational progressions have been identified. It is noted that VC joins CrC, NbC, and MoC as species in which the metal ns-based 3? orbital is unoccupied, resulting in large dipole moments in the ground states of these molecules. In the corresponding 5d metal carbides, however, the 3? orbital is occupied, leading to different ground electronic states of the 5d congeners, TaC and WC. PMID:23805938

Krechkivska, Olha; Morse, Michael D

2013-12-19

92

Interphase phosphorylation of lamin A.  

PubMed

Nuclear lamins form the major structural elements that comprise the nuclear lamina. Loss of nuclear structural integrity has been implicated as a key factor in the lamin A/C gene mutations that cause laminopathies, whereas the normal regulation of lamin A assembly and organization in interphase cells is still undefined. We assumed phosphorylation to be a major determinant, identifying 20 prime interphase phosphorylation sites, of which eight were high-turnover sites. We examined the roles of these latter sites by site-directed mutagenesis, followed by detailed microscopic analysis - including fluorescence recovery after photobleaching, fluorescence correlation spectroscopy and nuclear extraction techniques. The results reveal three phosphorylation regions, each with dominant sites, together controlling lamin A structure and dynamics. Interestingly, two of these interphase sites are hyper-phosphorylated in mitotic cells and one of these sites is within the sequence that is missing in progerin of the Hutchinson-Gilford progeria syndrome. We present a model where different phosphorylation combinations yield markedly different effects on the assembly, subunit turnover and the mobility of lamin A between, and within, the lamina, the nucleoplasm and the cytoplasm of interphase cells. PMID:24741066

Kochin, Vitaly; Shimi, Takeshi; Torvaldson, Elin; Adam, Stephen A; Goldman, Anne; Pack, Chan-Gi; Melo-Cardenas, Johanna; Imanishi, Susumu Y; Goldman, Robert D; Eriksson, John E

2014-06-15

93

Lamin A, farnesylation and aging.  

PubMed

Lamin A is a component of the nuclear envelope that is synthesized as a precursor prelamin A molecule and then processed into mature lamin A through sequential steps of posttranslational modifications and proteolytic cleavages. Remarkably, over 400 distinct point mutations have been so far identified throughout the LMNA gene, which result in the development of at least ten distinct human disorders, collectively known as laminopathies, among which is the premature aging disease Hutchinson-Gilford progeria syndrome (HGPS). The majority of HGPS cases are associated with a single point mutation in the LMNA gene that causes the production of a permanently farnesylated mutant lamin A protein termed progerin. The mechanism by which progerin leads to premature aging and the classical HGPS disease phenotype as well as the relationship between this disorder and the onset of analogous symptoms during the lifespan of a normal individual are not well understood. Yet, recent studies have provided critical insights on the cellular processes that are affected by accumulation of progerin and have suggested that cellular alterations in the lamin A processing pathway leading to the accumulation of farnesylated prelamin A intermediates may play a role in the aging process in the general population. In this review we provide a short background on lamin A and its maturation pathway and discuss the current knowledge of how progerin or alterations in the prelamin A processing pathway are thought to influence cell function and contribute to human aging. PMID:21871450

Reddy, Sita; Comai, Lucio

2012-01-01

94

Nonlinear analysis of composite laminates  

SciTech Connect

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

Chen, J.

1984-01-01

95

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

96

Analysis of Diatom Blooms Using DNA Fingerprints.  

National Technical Information Service (NTIS)

My long-term goals are to understand the interaction between the biological and environmental factors that dictate the timing and magnitude of diatom blooms. I am particularly interested in how species behavior is coupled to environmental conditions and h...

E. V. Armbrust

2005-01-01

97

Oceanographic and Biogeochemical Insights from Diatom Genomes  

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

98

Oceanographic and biogeochemical insights from diatom genomes.  

PubMed

Diatoms are the most successful group of eukaryotic phytoplankton in the modern ocean and have risen to dominance relatively quickly over the last 100 million years. Recently completed whole genome sequences from two species of diatom, Thalassiosira pseudonana and Phaeodactylum tricornutum, have revealed a wealth of information about the evolutionary origins and metabolic adaptations that have led to their ecological success. A major finding is that they have incorporated genes both from their endosymbiotic ancestors and by horizontal gene transfer from marine bacteria. This unique melting pot of genes encodes novel capacities for metabolic management, for example, allowing the integration of a urea cycle into a photosynthetic cell. In this review we show how genome-enabled approaches are being leveraged to explore major phenomena of oceanographic and biogeochemical relevance, such as nutrient assimilation and life histories in diatoms. We also discuss how diatoms may be affected by climate change-induced alterations in ocean processes. PMID:21141668

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

2010-01-01

99

Amino Acid Biosynthesis Pathways in Diatoms  

PubMed Central

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

Bromke, Mariusz A.

2013-01-01

100

Some New or Rare Diatoms from Alaska.  

National Technical Information Service (NTIS)

In alphabetical order 29 different diatomaceous forms are mentioned, 20 of which must be considered new and not previously described. They have been found in material of freshwater diatoms collected in Alaska in the summer of 1963. (Author)

N. Foged

1968-01-01

101

The Ecology of Diatoms in Hardwater Habitats.  

National Technical Information Service (NTIS)

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

J. D. Dodd

1971-01-01

102

Modeling of Atom-Diatom Scattering.  

National Technical Information Service (NTIS)

This report entails the work performed on modeling atom-diatom scattering processes utilizing the Impulse Approach (IA). Results of the model, obtained with a computer code, have proven to be in remarkable agreement with laboratory measurements for severa...

J. M. Sindoni

1992-01-01

103

Plankton Diatom Assemblages in Lake Michigan.  

National Technical Information Service (NTIS)

The various elements of Lake Michigan plankton diatom flora, their seasonal cycles, and history of changes were determined and genera and species are listed. Absolute frequency, relative frequency, and contribution to diversity of each taxon were computer...

E. F. Stoermer J. J. Yang

1969-01-01

104

DIATOMS: POWERFUL INDICATORS OF ENVIRONMENTAL CHANGE  

EPA Science Inventory

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

105

Acute laminitis: medical and supportive therapy.  

PubMed

Acute laminitis is a serious complication of many primary conditions in the horse. This article summarizes the most appropriate approach to management of the horse with acute laminitis, based on current information. PMID:20381739

van Eps, Andrew W

2010-04-01

106

Polymer metal lamination by radiation method  

NASA Astrophysics Data System (ADS)

Conventional technology of PE-metal laminate involves the use of adhesives for laminating. Environ pollution has been a big problem not easily resolved and processing is complicated. By radiation peroxidation of the surface of polyethylene a simple polyethylene-metal laminating method has been succeeded. Measurements of the mechanical properties and the electrical properties made according to China's national standards showed the properties of the laminating film conforming well with the national standards. It has been found that the adhesion strength of the PE-metal film is affected by irradiation, the metal surface reactivity and cleaning of the laminating surface. PE-metal film laminated by radiation method is more heat resistant than the film laminated by conventional methods. The laminate materials can be widely used in electrical devices, chemical and packaging industry.

Yizheng, Ma; Maoqing, Chen; Zhixiong, Feng; Dakuan, Sun; Dawei, You

1993-07-01

107

Diatom paleoecology of Laguna Zoncho, Costa Rica  

Microsoft Academic Search

We analyzed diatoms in a sediment profile from Laguna Zoncho in southern Pacific Costa Rica (lake elevation 1190 m asl, depth 2.6 m, area 0.75 ha) spanning some 3240 cal  yr. Diatoms are common in the profile, which we subdivide into three zones. Zone C (~3240–1020 cal  yr B.P.) is dominated by Staurosira construens var. venter and Aulacoseira spp.; during this time, the lake was dilute

Kurt A. Haberyan; Sally P. Horn

2005-01-01

108

Diatoms in river water-monitoring studies  

Microsoft Academic Search

Diatoms grow abundantly in rivers, colonising almost all suitable habitats. They have been used extensively in studies related\\u000a to the monitoring of water quality. This review attempts to draw together data from a wide variety of approaches. The advantage\\u000a of sampling discrete habitats is stressed and particular attention is paid to the diatom flora of stone surfaces (epilithon)\\u000a which is

F. E. Round

1991-01-01

109

The chemical composition of the diatom frustule  

Microsoft Academic Search

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

T. V. Desikachary; N. E. Dweltz

1961-01-01

110

Hydrodynamics of diatom chains and semiflexible fibres.  

PubMed

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

Nguyen, Hoa; Fauci, Lisa

2014-07-01

111

Mechanical Properties and Damping Characteristics of Laminate.  

National Technical Information Service (NTIS)

A laminate fabricated by heat rolling consists of five layers. The value Q(sup -1) of the laminate is measured in a wide temperature range. The results show that the internal friction of the laminates increases monotonously with increasing thickness of th...

B. H. Luo S. Zhou Y. Song

1995-01-01

112

Pressure-Localizing Inserts for Bagging Laminations  

NASA Technical Reports Server (NTRS)

Devices compress composite laminates to conform to tight inside corners of molds. Proposed use of pressure-localizing insert allows composite laminates to be compacted into tight corners by conventional pressure or vacuum-bagging techniques. Because of manufacturing technique, larger selection of part shapes becomes amenable to lamination.

Schmaling, Dave; Carter, Donald

1987-01-01

113

Modeling a Piezothermoelastic Laminated Plate-Membrane  

Microsoft Academic Search

Analysis of laminated piezopolymer actuated circular membranes is presented. The nonlinear equations of motion governing a continuous circular laminate of arbitrary thermal, electrical and mechanical properties are developed. Assuming axisymmetry, a closed-form asymptotic solution is developed using a combination of perturbation techniques. These governing equations are applied to a model laminate of Kapton and PVDF materials where static and dynamic

James W. Rogers; Gregory S. Agnes

2002-01-01

114

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.

115

Multilayer printed wiring board lamination  

SciTech Connect

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

Lula, J.W.

1980-06-01

116

Theory of unsymmetric laminated plates  

Microsoft Academic Search

Timoshenko's shear correction factor for an unsymmetric laminated plate is derived rigorously from a formulation involving the theory of elasticity. This approach includes the effect of nonlinear in-plane displacements and emphasizes the effect of shear deformation. As a consequence of the derivation, physically meaningful quantities including the neutral axis, mean elastic constant, and bending rigidity of a composite plate are

T. S. Chow

1975-01-01

117

Theory of unsymmetric laminated plates  

Microsoft Academic Search

Timoshenko’s shear correction factor for an unsymmetric laminated plate is derived rigorously from a formulation involving the theory of elasticity. This approach includes the effect of nonlinear in?plane displacements and emphasizes the effect of shear deformation. As a consequence of the derivation, physically meaningful quantities including the neutral axis, mean elastic constant, and bending rigidity of a composite plate are

T. S. Chow

1975-01-01

118

Polarization effects in uncharged laminates  

Microsoft Academic Search

It has been suggested that polymer laminates in which a charge has accumulated at the interface of two polymers will exhibit piezoelectric properties. It has also been suggested that a composite which consists of a polymer matrix and dispersed inorganic ferroelectric particles exhibits piezoelectricity after poling. The author proposed a technique of multielement electret preparation that is based on these

K. Mazur

1989-01-01

119

Fracture of laminated composite materials  

Microsoft Academic Search

Cracks occurring in conventional laminates, or artificially bonded composites, and slip bands appearing in lamellar alloys, or naturally bonded composites, are studied. In this analysis, a mixed mode plane crack is modeled by continuous distributions of both climb and glide dislocations. The requirement that the boundary conditions prescribed on the surfaces of this crack must be satisfied results in dual

Omoike

1984-01-01

120

Investigation into the Optical Properties of Nanostructured Silica from Diatoms.  

National Technical Information Service (NTIS)

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

M. Hildebrand B. Palenik

2003-01-01

121

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

122

Classical Breeding in Diatoms: Scientific Background and Practical Perspectives  

Microsoft Academic Search

\\u000a Diatoms are becoming increasingly attractive for scientists and important for various industrial applications. Diatoms are\\u000a diploid sexual organisms and it is generally accepted that controlled genetic manipulations via sexual reproduction are instrumental\\u000a for basic diatom research. For more practical aims, e.g., selection and “improvement” of economically relevant diatom strains,\\u000a the classical breeding approach still remains entirely unexplored. Here, we discuss

Victor A. Chepurnov; Peter Chaerle; Luc Roef; Annemieke Meirhaeghe; Koen Vanhoutte

123

Lamination residual strains and stresses in hybrid laminates  

NASA Technical Reports Server (NTRS)

An investigation is conducted of the effects of hybridization on the magnitude of lamination residual stresses. Eight-ply graphite/Kevlar 49/epoxy and graphite/S-glass/epoxy laminates were studied. The same matrix resin was selected for all basic materials to ensure compatibility and uniform curing of the various plies. The specimens, with inserted strain gages and thermocouples, were subjected to curing and postcuring cycles in an autoclave. Subsequently, the specimens were subjected to a thermal cycle from room temperature to 444 K and down to room temperature. It was found that hydridizing reduces apparently residual strains and stresses in the graphite plies. However, these strains were not affected much by the type and degree of hybridization.

Daniel, I. M.; Liber, T.

1977-01-01

124

The lithologic expression of millennial-scale variability in the Pacific sub-Arctic: IODP Exp. 323, Site U1340  

NASA Astrophysics Data System (ADS)

Prominent variability in physical properties and lithology are observed in late Pleistocene sediment cores collected during IODP Exp. 323 at Site U1340 on the Bowers Ridge (1292m; Bering Sea). Pronounced lithologic cycles in the last 60 ka of the record are expressed by alternations between more or less laminated diatom ooze and clay-dominated intervals. These cycles correspond to high-frequency variability of stable isotopes that represent D-O type events (Schlung et al. 2012). High-resolution sedimentologic analyses that combine an improved method for the quantitative assessment of the sedimentary components on smear slides with other independent methods (e.g., laser particle size analysis, scanning electron microscopy, physical properties), offer new insights on the lithologic expression of millennial-scale variability in the Pacific sub-Arctic. The sedimentologic data, together with stable isotope geochemistry and physical properties, highlight differences between the laminated (LDO) and the homogenous (HDO) diatom ooze layers that alternate with the clays. The LDOs have lower density and higher porosity, with at least 25% of the diatoms valves preserved versus only 10% is in the HDOs. LDOs diatom valve integrity is correlated to the abundance of diatoms (~30%); no correlation exists for the HDOs. These observations suggest millennial-scale variability has developed under distinct oceanographic conditions for the two types of diatom oozes. This is supported by geochemical data that show LDOs have a lighter ?(_^18)O signature compared to the clay interlayers, while the HDOs do not. Overall, we suggest millennial-scale variability in the Bering Sea is expressed by lithologic cycles that are more complex than in coeval basins recording similar high-frequency cycles (e.g., Santa Barbara Basin). This complexity may reflect a difference in depositional conditions during the formation of the diatom oozes, possibly including the influence of sea-ice during LDO deposition.

Drake, M. K.; Aiello, I. W.; Ravelo, A. C.

2013-12-01

125

AFM nanoindentations of diatom biosilica surfaces.  

PubMed

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

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

2007-04-24

126

Diatoms: a fossil fuel of the future.  

PubMed

Long-term global climate change, caused by burning petroleum and other fossil fuels, has motivated an urgent need to develop renewable, carbon-neutral, economically viable alternatives to displace petroleum using existing infrastructure. Algal feedstocks are promising candidate replacements as a 'drop-in' fuel. Here, we focus on a specific algal taxon, diatoms, to become the fossil fuel of the future. We summarize past attempts to obtain suitable diatom strains, propose future directions for their genetic manipulation, and offer biotechnological pathways to improve yield. We calculate that the yields obtained by using diatoms as a production platform are theoretically sufficient to satisfy the total oil consumption of the US, using between 3 and 5% of its land area. PMID:24529448

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

2014-03-01

127

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...

128

Vibration damping characteristics of laminated steel sheet  

NASA Astrophysics Data System (ADS)

The use of laminated steel sheets as vibration damping materials was studied. The laminate consisted of a viscoelastic layer which was sandwiched between two steel sheets. The study sought to identify parameters affecting the damping efficiency of the laminate. Two viscoelastic materials, a copolymer based on ethylene and acrylic acid (PEAA) and polyvinyl butyral (PVB), were used. A frequency analyzer was used to measure the loss factor of the laminates. A theoretical analysis of damping efficiency based on a model described by Ungar[2] was also carried out. The results showed that the loss factor of the PEAA-based laminates increased monotonically with increasing thickness of the viscoelastic layer and leveled off at 25.9 pct of total thickness. Ungar’s theory predicted a higher loss factor than the experimental data. This might have resulted from interfacial adhesive bonding, a nonuniform viscoelastic layer thickness, and the extrapolation of the rheological data from low to high frequencies. The loss factor of the laminate increased with increasing temperature, reached a maximum value, and then decreased. An optimum temperature for maximum damping was found for each laminate configuration. The PEAA-based laminates possessed higher damping efficiency than the PVB-based laminates at room temperature. The symmetric laminate (with the same steel sheet thickness) possessed a better damping efficiency than asymmetric laminates. The maximum damping peak of the laminates using a polymer blend, when compared to the laminates using unblended resin, exhibited a lower loss factor value, became broader, and occurred at a temperature between the T g’s of the individual components of the polymer blend.

Chen, Y. S.; Hsu, T. J.; Chen, S. I.

1991-03-01

129

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

SciTech Connect

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

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

2008-08-01

130

Can Hydrodynamics Change Phosphorus Strategies of Diatoms?—Nutrient Levels and Diatom Blooms in Lotic and Lentic Ecosystems  

Microsoft Academic Search

Diatom blooms occur in many water bodies worldwide, causing significant ecological and social concerns. In order to understand the mechanisms of diatom blooms formation, the effects of varying phosphorus (P) concentration and\\u000a hydrodynamics on the growth of diatoms were studied by combining results from field observations and laboratory experiments.\\u000a The field investigation showed that spring diatom blooms (Cyclotella meneghiniana and

Peili Wang; Hong Shen; Ping Xie

131

Plastic Laminate Pulsed Power Development  

SciTech Connect

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

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

2000-09-01

132

Failure Criteria for FRP Laminates  

Microsoft Academic Search

A new set of six phenomenological failure criteria for fiber-reinforced polymer laminates denoted LaRC03 is described. These criteria can predict matrix and fiber failure accurately, without the curve-fitting parameters. For matrix failure under transverse compression, the angle of the fracture plane is solved by maximizing the Mohr-Coulomb effective stresses. A criterion for fiber kinking is obtained by calculating the fiber

Carlos G. Davila; Pedro P. Camanho; Cheryl A. Rose

2005-01-01

133

Fatigue Behavior of Composite Laminate  

Microsoft Academic Search

The paper discusses a characterization of fatigue behavior of [0\\/±45\\/90]s glass\\/epoxy laminate in terms of the following parameters: static properties; S-N relationship; reliability; effect of thickness variation; damage initiation and growth; temperature increase; secant modulus change; effect of preloading on residual modulus and strength; and effect of ply failure on compression buckling strength. Some of the findings are the following.

H. T. Hahn; R. Y. Kim

1976-01-01

134

Large Glued-Laminated Timber Beams with Two Grades of Tension Laminations.  

National Technical Information Service (NTIS)

Bending strength of 26 glued-laminated timbers were appraised as a basis for more precise design. Part of the beams were manufactured according to present AITC and lumber industry specifications, while the other beams had improved tension laminations. Whe...

B. Bohannan R. C. Moody

1969-01-01

135

Both emerin and lamin C depend on lamin A for localization at the nuclear envelope  

Microsoft Academic Search

Physical interactions between lamins and emerin were investigated by co-immunoprecipitation of in vitro translated proteins. Emerin interacted with in vitro translated lamins A, B1 and C in co-immunprecipitation reactions. Competition reactions revealed a clear preference for interactions between emerin and lamin C. Structural associations between lamins and emerin were investigated in four human cell lines displaying abnormal expression and\\/or localisation

A. Vaughan; M. Alvarez Reyes; Joanna M. Bridger; Jos L. V. Broers; Frans C. S. Ramaekers

2001-01-01

136

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.

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

2014-01-01

137

Laminate delamination due to thermal gradients  

SciTech Connect

Flaw-induced delamination of orthotropic laminates subject to through-thickness temperature gradients is analyzed. A crack-like flaw impedes heat flow through the laminate, producing thermal stresses and crack tip stress intensities. The focus is on delamination cracks which propagate under steady-state conditions. The steady-state analysis becomes accurate for a crack whose length is about one laminate thickness. Moreover, the analysis provides realistic fail-safe criteria for excluding delamination.

Hutchinson, J.W.; Lu, T.J. [Harvard Univ., Cambridge, MA (United States). Div. of Applied Sciences

1995-10-01

138

Process for Preparing High Temperature Polyimide Film Laminates.  

National Technical Information Service (NTIS)

A process for fabricating large area void-free polyimide laminate structures wherein multiple ply polyimide film laminates may be constructed without decreasing the individual film strength is described. Layers of metal foil may be laminated between polyi...

A. K. St.Clair T. L. St.Clair

1980-01-01

139

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...after importation of certain prepregs, laminates, and finished circuit boards that infringe...Co., Ltd., and VENTEC-Global Laminates USA LLC based on a consent order....

2013-04-19

140

Prediction of Material Damping of Laminated Polymer Matrix Composites.  

National Technical Information Service (NTIS)

In this study the material damping of laminated composites is derived analytically. The derivation is based on the classical lamination theory in which there are eighteen material constants in the constitutive equations of laminated composites. Six of the...

C. T. Sun J. K. Wu R. F. Gibson

1987-01-01

141

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

142

An alternative solution of diatomic molecules  

NASA Astrophysics Data System (ADS)

The spectrum of r -1 and r -2 type potentials of diatomic molecules in radial Schrödinger equation are calculated by using the formalism of asymptotic iteration method. The alternative method is used to solve eigenvalues and eigenfunctions of Mie potential, Kratzer-Fues potential, Coulomb potential, and Pseudoharmonic potential by determining the ?, ?, ? and ? parameters.

Öztemel, Özgür; Ol?ar, Eser

2014-02-01

143

Small-Scale Distributions of Oceanic Diatoms.  

National Technical Information Service (NTIS)

A sampling study was designed to investigate small-scale abundance fluctuations of diatoms over a distance of 10 miles. It was carried out at three depths in each of two oceanic environments of the North Pacific. Significant nonrandom distributions were o...

E. L. Venrick

1971-01-01

144

Seasonal fluctuations of Lake Michigan diatoms  

USGS Publications Warehouse

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

Holland, Ruth E.

1969-01-01

145

Differential response of marine diatoms to solvents  

SciTech Connect

Unicellular algae in aquatic ecosystems are subjected to a variety of pollutants from sources such as runoff from agricultural lands and industrial outfalls. Organic solvents are natural components of oil deposits and commonly find their way into surface waters as a result of discharges from refineries, waste oil, disposal, and accidental spills. Organic solvents can make their way into the environment as industrial wastes. Because of their carcinogenic potential, contamination of soil and water by solvents is cause for serious concern. Relatively few reports have been published on the comparative toxicity of solvents towards test organisms, and these dealt primarily with fish and aquatic invertebrates. However, only few data of toxicity effects of solvents on algae have been published. Phytoplankton species vary in their tolerance to trace metals. Diatoms in particular are able to detoxify trace metals by the excretion of organic compounds. A previous study reported that diatoms collected form different sites in the Gulf of Mexico varied in their physiological characteristics. Algae have been considered to be good indicator s of bioactivity of industrial wastes. Unicellular algae vary in their response to a variety of toxicants. Little is known, however, about toxicity of solvents to marine diatoms. The work reported here was done to examine the effect of selected solvents on seven diatom species to determine whether they differed in their responses to these chemicals. 16 refs., 1 fig.

Tadros, M.G.; Phillips, J.; Patel, H.; Pandiripally, V. [Alabama A & M Univ., Huntsville, AL (United States)

1995-06-01

146

Diatom Populations Changes in Lake George (NY).  

National Technical Information Service (NTIS)

The diatom populations in the plankton and periphyton at depths of three, nine and fifteen meters in the north and south basins of Lake George, New York have been characterized and measured over a three year period. Measurements of environmental factors, ...

N. L. Clesceri S. L. Williams

1972-01-01

147

Relativistic Molecular Orbital Calculations for Diatomic Molecules  

Microsoft Academic Search

The relativistic molecular orbital calculations have been made for diatomic molecules by the use of the discrete variational Xa method. The validity of the method has been tested for CO mole- cule and good agreement is obtained between the relativistic and nonrelativistic calculations. The relativistic results for UO molecule are compared with the nonrelativistic ones and the importance of the

Takeshi MUKOYAMA; Hirohiko ADACHI

148

Electron transport through a diatomic molecule  

NASA Astrophysics Data System (ADS)

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

Imran, Muhammad

2014-08-01

149

Machining of fiber-reinforced composite laminates  

NASA Astrophysics Data System (ADS)

As fiber-reinforced composite laminates are becoming considerably popular in a wide range of applications, the necessity for machining such materials is increasing rapidly. Due to their microscopical inhomogeneity, anisotropy, and highly abrasive nature, composite laminates exhibit some peculiar types of machining damage. Consequently, the machining of composite laminates requires a different approach from that used for metals and offers a challenge from both an academic and application point of view. In the present work, the drilling of composite laminated plates and the edge trimming of tubular composite laminates were investigated through theoretical analyses and their experimental verification. First, a drilling process model using linear elastic fracture mechanics and classical plate bending theory was developed to predict the critical thrust value responsible for the onset of delamination during the drilling of composite laminates with pre-drilled pilot holes. Experiments using stepped drills, which can utilize the effectiveness of such pilot holes, were conducted on composite laminates. Reasonably good agreement was found between the results of the process model and the tests. Second, the development of a model-based intelligent control strategy for the efficient drilling of composite laminates was explored by experiments and analyses. In this investigation, mathematical models were created to relate the drilling forces to cutting parameters and to identify the different process stages. These models predicted the degree of thrust force regulation to prevent delamination. Third, the edge trimming of thin-walled tubular composite laminates was modeled and analyzed for estimating the critical cutting force at the initiation of longitudinal cracking. A series of full-scale edge trimming tests were conducted on tubular composite specimens to assess the current approach and to obtain basic machining data for various composite laminates. The present study provides direction for the establishment of machining parameters while preventing machining damage in fiber-reinforced composite laminates through appropriate tool design, selection of cutting conditions, and adaptive control.

Won, Myong-Shik

150

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

151

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

152

Molding a high-density laminate  

NASA Technical Reports Server (NTRS)

Molding press is used to form phenolic resin impregnated glass fiber cloth into a high-density, cylindrical-ring laminate. The press applies clamping pressure and heat to a mold containing the glass fiber cloth laminate, which has hydrostatic pressure applied to it by means of a specially designed pressure plug.

Haraway, W. M.; Heier, W. C.; King, C. B.

1968-01-01

153

Laminated multilayer sheet structure and its utilization  

Microsoft Academic Search

A laminated multilayer sheet structure is described comprising (A) an opaque flexible sheet layer, and (B) a flexible layer laminated on the surface of layer (A) and composed of a transparent thermic ray reflecting layer (Bâ) bonded to a transparent synthetic resin layer (Bâ), said layer (Bâ) being a transparent thermic ray reflecting layer composed of (I) a layer of

K. Chiba; K. Itoh; Y. Mitani; S. Sobajima; U. Yonemura

1980-01-01

154

Failure Modes of Angle Ply Laminates  

Microsoft Academic Search

Experimental investigation of failure of balanced angle-ply laminates under symmetric uniaxial tension revealed three distinct failure modes. The three different modes were observed for reinforcement angles smaller than ±45°, for the ±45° angle ply and for angles larger than ±45°. Comparison of experimental failure loads with theoretical failure loads based on first laminate failure criteria showed good agreement for certain

Assa Rotem; Zvi Hashin

1975-01-01

155

Properties of Low-Expansion Laminates  

NASA Technical Reports Server (NTRS)

Laminate elastic constants and coefficients of thermal expansion calculated for near-zero-expansion graphite/aluminum and graphite/ magnesium composites. Report presents results in graphic form for these properties as function of laminate angle and fiber volume fraction for four high-modulus continuous-pitch fiber.

Kural, M.

1985-01-01

156

Progressive Transverse Cracking of Crossply Composite Laminates  

Microsoft Academic Search

A simplified shear lag analysis using a progressive damage scheme is pro posed for crossply composite laminates under uniaxial tensile loading. Closed form solu tions for stress distributions, transverse crack density and reduced stiffnesses of damaged plies as well as the entire laminate can be obtained as a function of applied load and prop erties of the constituent plies, where

J.-W. Lee; I. M. Daniel

1990-01-01

157

Delamination-free drilling of composite laminates  

Microsoft Academic Search

Composite laminates in significant numbers are rendered unacceptable due to delamination that occurs during the drilling operation. Thrust generated during the drilling operation is identified as responsible for delamination. Expressions developed for critical thrusts and critical feed rates, by modeling the delamination zone as an elliptical plate in unidirectional laminates, appear to be fairly accurate. It has been demonstrated that

S. Jain; D. C. H. Yang

1994-01-01

158

Silicone modified resins for graphite fiber laminates  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

159

On the electroplating of laminated chromium  

Microsoft Academic Search

A microprocessor-controlled flow plating process was developed to deposit laminated chromium consisting of alternating layers of low contraction (LC) and high contraction (HC) chromium. The automated plating system contains a large number of variable parameters designed to allow the use of multiple plating modes. The available modes include a combination of direct current, interrupted, periodic reverse, pulse and laminated chromium

E. S. Chen; G. P. Capsimalis; G. R. Weigle

1987-01-01

160

Do lamins influence disease progression in cancer?  

PubMed

For nearly 60 years, diagnosis of cancer has been based on pathological tests that look for enlargement and distortion of nuclear shape. Because of their involvement in supporting nuclear architecture, it has been postulated that the basis for nuclear shape changes during cancer progression is altered expression of nuclear lamins and in particular lamins A and C. However, studies on lamin expression patterns in a range of different cancers have generated equivocal and apparently contradictory results. This might have been anticipated since cancers are diverse and complex diseases. Moreover, whilst altered epigenetic control over gene expression is a feature of many cancers, this level of control cannot be considered in isolation. Here I have reviewed those studies relating to altered expression of lamins in cancers and argue that consideration of changes in the expression of individual lamins cannot be considered in isolation but only in the context of an understanding of their functions in transformed cells. PMID:24563367

Hutchison, Christopher J

2014-01-01

161

Stationary turbine component with laminated skin  

DOEpatents

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

James, Allister W. (Orlando, FL)

2012-08-14

162

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

PubMed

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

Wang, Peili; Shen, Hong; Xie, Ping

2012-02-01

163

Marine diatom biostratigraphy in Pacific Coast neogene basins  

SciTech Connect

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

Barron, J.A.

1988-03-01

164

Marine diatom growth patterns are correlated with adjoining weather fluctuations  

NASA Astrophysics Data System (ADS)

Diatoms-the most important silicon-utilizing microorganisms show many peculiar behaviors due to presence of a large quantity of silicon in them. Thus temperature and some chemicals which are expected to influence growth of marine diatoms often show bizarre outcomes. It has been found that when diatom population decreases in the sea, sea temperature decreases which leads to shift of sea streams as well as remarkable cooling of the adjoining atmosphere. One can predict future climatic swings or NAO utilizing statistical modeling of this phenomenon particularly when we consider pennate group of diatoms. This modeling can also explain the ENSO phenomenon in Pacific Ocean and the peculiar association of the southerly shift of the Gulf Stream and major storms and heavy rains in the adjoining northern part of the globe. This predictive value is also supported by variance partitioning analysis data of diatom profiles indicating climatic signal imprints in sediments and studies showing exploitation of diatoms as paleoclimatic proxies.

Das, S.

2013-12-01

165

Barium uptake and adsorption in diatoms  

Microsoft Academic Search

Using trace metal-defined culture conditions, we measured the cellular barium concentration in cultures of the diatom Thalassiosira weissflogii. In cultures with low Fe concentration, at a typical surface seawater Ba concentration of 35 to 40 nmol\\/L, the cellular Ba was 0.5 ?mol\\/mol P (?0.04 ?g\\/g dw), much below all previously published values for phytoplankton. When the Fe concentration in the

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

2005-01-01

166

Role of silicon in diatom metabolism  

Microsoft Academic Search

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

Farooq Azam; Benjamin E. Volcani

1974-01-01

167

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

168

The Different Function of Single Phosphorylation Sites of Drosophila melanogaster Lamin Dm and Lamin C  

PubMed Central

Lamins' functions are regulated by phosphorylation at specific sites but our understanding of the role of such modifications is practically limited to the function of cdc 2 (cdk1) kinase sites in depolymerization of the nuclear lamina during mitosis. In our study we used Drosophila lamin Dm (B-type) to examine the function of particular phosphorylation sites using pseudophosphorylated mutants mimicking single phosphorylation at experimentally confirmed in vivo phosphosites (S25E, S45E, T435E, S595E). We also analyzed lamin C (A-type) and its mutant S37E representing the N-terminal cdc2 (mitotic) site as well as lamin Dm R64H mutant as a control, non-polymerizing lamin. In the polymerization assay we could observe different effects of N-terminal cdc2 site pseudophosphorylation on A- and B-type lamins: lamin Dm S45E mutant was insoluble, in contrast to lamin C S37E. Lamin Dm T435E (C-terminal cdc2 site) and R64H were soluble in vitro. We also confirmed that none of the single phosphorylation site modifications affected the chromatin binding of lamin Dm, in contrast to the lamin C N-terminal cdc2 site. In vivo, all lamin Dm mutants were incorporated efficiently into the nuclear lamina in transfected Drosophila S2 and HeLa cells, although significant amounts of S45E and T435E were also located in cytoplasm. When farnesylation incompetent mutants were expressed in HeLa cells, lamin Dm T435E was cytoplasmic and showed higher mobility in FRAP assay.

Zaremba-Czogalla, Magdalena; Piekarowicz, Katarzyna; Wachowicz, Katarzyna; Koziol, Katarzyna; Dubinska-Magiera, Magda; Rzepecki, Ryszard

2012-01-01

169

Nanoplasmonic photonic crystal diatoms and phytoliths  

NASA Astrophysics Data System (ADS)

Evidence is emerging that silica-containing plant cells (phytoliths) and single cell micro-organisms (diatoms) exhibit optical properties reminiscent of photonic crystals. In the latter biosilicates, these properties appear to arise from light interactions with the intricate periodic patterns of micro- and nano-pores called foramina that are distributed over the frustule (outer silica shell). In this report, we show that Nitzschia Closterium pennate diatom frustules can be used to template arrays of nanoplasmonic particles to confer more complex physical properties, as shown by simulation and experiment. Selective templating of silver and gold nanoparticles in and around the array of pores was achieved by topochemical functionalization with nanoparticles deposited from solution, or by differential wetting/dewetting of evaporated gold films. The nanoplasmonic diatom frustules exhibit surface enhanced Raman scattering from chemisorbed 4-aminothiophenol. Thermally induced dewetting of gold films deposited on a frustule produces two classes of faceted gold nanoparticles. Larger particles of irregular shape are distributed with some degree of uniaxial anisotropy on the surface of the frustule. Smaller particles of more uniform size are deposited in a periodic manner in the frustule pores. It is thought that surface curvature and defects drive the hydrodynamic dewetting events that give rise to the different classes of nanoparticles. Finite difference time domain calculations on an idealized nanoplasmonic frustule suggest a complex electromagnetic field response due to coupling between localized surface plasmon modes of the nanoparticles in the foramina and an overlayer gold film.

Andrews, Mark P.; Hajiaboli, Ahmadreza; Hiltz, Jonathan; Gonzalez, Timothy; Singh, Gursimranbir; Lennox, R. Bruce

2011-02-01

170

Edge Effects on Thermally Induced Stresses in Composite Laminates  

Microsoft Academic Search

Thermally induced stresses in fiber composite laminates play an important role in the strength and failure of such laminates as load carrying members. When laminates have free edges, cutouts or holes, interlaminar stress concentration will usually develop near the free-edge region under service loads. An accurate evaluation of thermally induced edge stresses will further the understanding of the laminates' behavior.

A. S. D. Wang; Frank W. Crossman

1977-01-01

171

Fatigue resistance of basalt fibers-reinforced laminates  

Microsoft Academic Search

Fabrics of basalt (BFs), E-glass (GFs), and carbon (CFs) fibers with the same areal density were used to prepare epoxy-based laminates. The BF laminates presented elastic moduli and strength values higher than those of the corresponding GF laminates, with tensile strength values near to that of CF laminates. Investigation of the behavior under fatigue conditions indicated superior performances of BF

A Dorigato; A Pegoretti

2012-01-01

172

Direct Composite Laminate Veneers: Three Case Reports  

PubMed Central

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

Korkut, Bora; Yan?koglu, Funda; Gunday, Mahir

2013-01-01

173

Accelerated dissolution of diatom silica by marine bacterial assemblages  

NASA Astrophysics Data System (ADS)

Downward fluxes of biogenic silica and organic matter in the global ocean derive dominantly from the productivity of diatoms - phytoplankton with cell walls containing silica encased in an organic matrix,. As diatoms have an absolute requirement for silicon (as silicic acid), its supply into the photic zone - largely by silica dissolution and upwelling - controls diatom production (and consequently the biological uptake of atmospheric CO2 by the ocean) over vast oceanic areas. Current biogeochemical models assume silica dissolution to be controlled by temperature, zooplankton grazing and diatom aggregation,, but the role of bacteria has not been established. Yet bacteria utilize about half of the organic matter derived from oceanic primary production by varied strategies, including attack on dead and living diatoms by using hydrolytic enzymes,, and could adventitiously hasten silica dissolution by degrading the organic matrix which protects diatom frustules from dissolution,. Here we report the results of experiments in which natural assemblages of marine bacteria dramatically increased silica dissolution from two species of lysed marine diatoms compared to bacteria-free controls. Silica dissolution accompanied, and was caused by, bacterial colonization and hydrolytic attack. Bacteria-mediated silicon regeneration rates varied with diatom type and bacterial assemblage; observed rates could explain most of the reported upper-ocean silicon regeneration,. Bacteria-mediated silicon regeneration may thus critically control diatom productivity and the cycling and fate of silicon and carbon in the ocean.

Bidle, Kay D.; Azam, Farooq

1999-02-01

174

Testing Prospects for Reliable Diatom Nanotechnology in Microgravity  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

175

Systematic identification of pathological lamin A interactors.  

PubMed

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 genotype-phenotype relationship and the basis for the pronounced tissue specificity of laminopathies are poorly understood. Here we seek to identify on a global scale lamin A-binding partners whose interaction is affected by disease-relevant LMNA mutations. In a screen of a human genome-wide ORFeome library, we identified and validated 337 lamin A-binding 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 Hutchinson-Gilford 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 protein-protein 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

2014-05-01

176

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 genotype–phenotype relationship and the basis for the pronounced tissue specificity of laminopathies are poorly understood. Here we seek to identify on a global scale lamin A–binding partners whose interaction is affected by disease-relevant LMNA mutations. In a screen of a human genome–wide ORFeome library, we identified and validated 337 lamin A–binding 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 Hutchinson–Gilford 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 protein–protein 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.

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

2014-01-01

177

Severe laminitis in multiple zoo species.  

PubMed

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

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

2014-03-01

178

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

179

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

180

Damage of hybrid composite laminates  

NASA Astrophysics Data System (ADS)

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

Haery, Haleh A.; Kim, Ho Sung

2013-08-01

181

Impact damage in composite laminates  

NASA Technical Reports Server (NTRS)

A low-velocity impact-damage model for quasi-symmetric graphite-fiber composite plates is presented. The distribution of damage in each layer of the plate was calculated by employing Di Sciuva's composite laminate theory together with Hashin's failure criterion for fiber-reinforced composites. The dynamic deformation of the target plate was represented by the lower vibrational modes of the plate. The principle of virtual work was applied in the formulation of the problem. In the analysis, the material was regarded as 'damaged' when its designed strength was reduced by the failure of its constituents. The constituent failures consisted of matrix crackings, fiber breakages, and delamination between layers. According to damage modes, the moduli of material in the damaged zone were reduced according to the failure criteria. The interaction between layers and its role in damage propagation were also studied.

Wang, Chung-Yue; Yew, Ching H.

1990-01-01

182

Creep response of glued-laminated beam reinforced with pre-stressed sub-laminated composite  

Microsoft Academic Search

In the past decades, the use of fibre-reinforced polymer (FRP) for enhancement of strength and stiffness of wood-based structural members has been established as an economical method. New developments have been ongoing to further improve the structural performance of glued-laminate beams. Recently, a novel integral sub-laminated composite, referred to as pre-stressed FRP–wood composite laminate (PWCL), was patented (KarisAllen and Tynes,

M. Yahyaei-Moayyed; F. Taheri

2011-01-01

183

Field Performance of Stress-Laminated Highway Bridges Constructed with Glued Laminated Timber  

Microsoft Academic Search

This paper summarizes the field performance of three stress-laminated deck timber bridges located in Wisconsin, New York, and Arizona. The deck superstructures of these single-span highway bridges is comprised of full-span glued laminated timber (glulam) beam laminations manufactured with southern pine, hem fir\\/red maple combination, and\\/or Douglas fir lumber species. These bridge structures were evaluated as part of a National

J. P. Wacker

184

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

185

Failure Modes of Angle Ply Laminates.  

National Technical Information Service (NTIS)

Experimental investigation of failure of balanced angle-ply laminates under symmetric uniaxial tension revealed three distinct failure modes. The three different modes were observed for reinforcement angles smaller than plus or minus 45 degrees, for the p...

A. Rotem Z. Hashin

1974-01-01

186

Composite Laminate Stiffnesses and Their Sensitivities.  

National Technical Information Service (NTIS)

An analysis of composite laminate stiffnesses and their sensitivities is presented within the framework of the design of structures made of composite materials. One of the columns upon which optimization of structures is built is the mathematical search m...

B. Geier

1992-01-01

187

Nonlinear Effects on Composite Laminate Thermal Expansion.  

National Technical Information Service (NTIS)

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

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

1979-01-01

188

Static Behaviour of Laminated Composite Shells  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

189

High energy impact on woven laminates  

Microsoft Academic Search

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

J. López-Puente; R. Zaera; C. Navarro

2003-01-01

190

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

191

Giant magnetoelectric effect in multiferroic laminated composites  

Microsoft Academic Search

Multiferroic laminated composites consisting of Terfenol- D \\/polyvinylidene-fluoride (PVDF) and lead-zirconate titanate (PZT)\\/PVDF particulate composite layers were prepared by a simple hot-molding technique. Magnetoelectric coefficients are characterized for the different measuring angles between the directions of polarization and applied magnetic field and at various frequencies. The results indicate that the three-phase laminated composites exhibit remarkable magnetoelectric effect especially at the

Yuanhua Lin; Ning Cai; Junyi Zhai; Gang Liu; Ce-Wen Nan

2005-01-01

192

Integration of TiO2 into the diatom Thalassiosira weissflogii during frustule synthesis  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

193

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

NASA Astrophysics Data System (ADS)

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

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

2007-08-01

194

Descriptive epidemiological study of equine laminitis.  

PubMed

A descriptive and matched case-control study of laminitis was conducted in 7 private practices and at the Texas Veterinary Medical Centre (TVMC) between May 1992 and July 1993. Out of 108 horses with laminitis, 19 acute (49%) and 20 chronic (51%) cases were seen in private practice and 16 acute (23%) and 53 (77%) cases at the TVMC. Gastrointestinal disease was the most common problem in 19/35 horses (54%), occurring just prior to the onset of acute laminitis in all hospitals. Among all horses in the study, most commonly used drugs were phenylbutazone (68%), acepromazine (34%), dimethyl sulphoxide (DMSO) (27%), antibiotics of various types (19%) and flunixin meglumine (19%). Acepromazine, DMSO and flunixin meglumine were used more commonly in acute cases of laminitis compared to chronic cases. In acutely affected horses, DMSO and flunixin meglumine were used significantly more often at the TVMC. In chronic cases, phenylbutazone and antibiotics were used more often in private practice. Shoeing and trimming were more commonly part of the treatment protocol for chronic cases. There were no significant associations between age, breed, sex or weight and the occurrence of acute laminitis. Horses with chronic laminitis were significantly older (P=0.04) and more females tended to be affected (P=0.08). PMID:8654351

Slater, M R; Hood, D M; Carter, G K

1995-09-01

195

Molecular Fossils as Time Indicators for the Evolution of Diatoms  

Microsoft Academic Search

Bacillariophyta (diatoms) are one of the most abundant divisions of phytoplankton, and contribute to almost 50% of the primary productivity of today's oceans. However, their ecological dominance is relatively young and little is known about the exact pace of their rapid evolution. DNA analyses on diatoms and the use of molecular clock calculations can help to reconstruct their evolution, but

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

2004-01-01

196

Adhesion and motility of fouling diatoms on a silicone elastomer  

Microsoft Academic Search

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

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

2004-01-01

197

Effect of iron limitation on cells of the diatom  

Microsoft Academic Search

The response of the Baltic diatom Cyclotella meneghiniana to iron deficiency was examined. The following growth parameters were measured: cell number, chlorophyll a and protein content. The results demonstrate the ability of this diatom to grow well with minimal iron availability; however, the rate of growth fell markedly at the lowest iron(III) concentration. The results of spectrophotometric chlorophyll a measurements

Jolanta Lewandowska; Alicja Kosakowska

198

Distribution of Displaced Antarctic Diatoms in the Argentine Basin.  

National Technical Information Service (NTIS)

Displaced Antarctic diatoms at the sediment/water interface were studied in deep-sea cores taken from the Argentine Continental Slope and Rise as well as the abyssal floor. The object was to determine, if the distribution of these diatoms in the sediment ...

L. H. Burckle D. Stanton

1975-01-01

199

Using diatom assemblages to assess urban stream conditions  

USGS Publications Warehouse

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

Walker, C. E.; Pan, Y.

2006-01-01

200

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

201

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

202

Cleaning of lake sediment samples for diatom oxygen isotope analysis  

Microsoft Academic Search

Detrital grain contamination in a diatom sample can considerably influence the d18Odiatom signal. In order to obtain a meaningful signal, pure samples must be used. This can be achieved via a series of cleaning stages including organic and carbonate material removal, sieving, differential settling and heavy liquid separation. The method described here works best for sediments with >20% diatom content.

David W. Morley; Melanie J. Leng; Anson W. Mackay; Hilary J. Sloane; Patrick Rioual; Richard W. Battarbee

2004-01-01

203

Investigation of Phosphorus Uptake Capability in the Diatom Didymosphenia geminata  

Microsoft Academic Search

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

Kyle Maurer

204

Transformation of Nonselectable Reporter Genes in Marine Diatoms  

Microsoft Academic Search

:   We report the genetic transformation of two marine diatoms by microparticle bombardment. The pennate diatom Phaeodactylum tricornutum was transformed with the bacterial gene Sh ble from Streptoalloteichus hindustanus, which confers resistance to the antibiotics phleomycin and zeocin. Transformants contained between 1 and 10 copies of the\\u000a exogenous DNA integrated into the genome by illegitimate recombination at apparently random locations.

Angela Falciatore; Raffaella Casotti; Catherine Leblanc; Chiara Abrescia; Chris Bowler

1999-01-01

205

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.

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

2013-01-01

206

Photosynthetic architecture differs in coastal and oceanic diatoms  

Microsoft Academic Search

Diatoms are a key taxon of eukaryotic phytoplankton and a major contributor to global carbon fixation. They are ubiquitous in the marine ecosystem despite marked gradients in environmental properties, such as dissolved iron concentrations, between coastal and oceanic waters. Previous studies have shown that offshore species of diatoms and other eukaryotic algae have evolved lower iron requirements to subsist in

Robert F. Strzepek; Paul J. Harrison

2004-01-01

207

Reactive collisions of atoms with diatomic molecules  

NASA Astrophysics Data System (ADS)

The theory of the reactive collision of an atom with a diatomic molecule is formulated in 'democratic' hyperspherical coordinates. An adiabatic ansatz is used to separate the distance coordinate from the angular coordinates. The angular eigenvalue problem is solved, using the hyperspherical harmonics as basis functions, while the R-matrix propagation method is used to integrate the resulting coupled equations along the distance coordinate. As an example, reactive collision probabilities for H + H2 are computed, using the Porter-Karplus surface. The symmetry requirements, when dealing with three identical Fermions in the collision, are considered explicitly.

Wolniewicz, L.; Hinze, Juergen; Alijah, Alexander

1993-08-01

208

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.

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

2012-01-01

209

Instability of diatomic deuterium in fcc palladium  

NASA Astrophysics Data System (ADS)

To clarify some of the solid-state aspects of cold fusion in deuterated transition metal electrodes, we have carried out first-principles self-consistent total energy calculations for various configurations of atomic and diatomic deuterium inside fcc palladium. We find that the stability of the Pd+D system is controlled by the relative position of the deuterium-induced antibonding level with respect to the Fermi energy. The equilibrium D-D distance in dense PdD ? up to ?=3 is found to be much larger than the free space value. The calculated Born-Oppenheimer energy surface of diatomic D2 in crystalline palladiuim is shown to have but metastable local minima whose internuclear separation is at least 0.2 Å larger than that of the isolated D2 molecule. We conclude that D2 in crystalline Pd will have a substantially lower tunneling probability than hitherto thought and that explanation for fusion mechanisms should be sought elsewhere.

Wei, Su-Huai; Zunger, Alex

1990-12-01

210

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

211

Quantitative evidence concerning the stabilization of sediments by marine benthic diatoms  

Microsoft Academic Search

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

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

1974-01-01

212

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

USGS Publications Warehouse

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

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

1999-01-01

213

Self-assembled diatom substrates with plasmonic functionality  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

214

[Applications of diatom in river health assessment: a review].  

PubMed

Diatom, as a kind of autotrophic photosynthetic eukaryotic algae, is an important primary producer in aquatic ecosystem, and can reflect the average status of water environment. As the bio-indicators of the environment, Nitzschia communis, Navicula minuscula, and Gomphonema parvulum can indicate the eutrophication of waters, whereas Gomphonema angustum, Epithemia adnata, and Diatoma moniliformis can indicate the oligotrophication of waters. Cyclotella bodanica, Neidium affine, and Eunotia exigua are all the eosinophilic species that can indicate waters acidity, Aminutissimum nodusa can indicate water's Cu concentration, and Synedra ulna can indicate the Zn concentration in waters. Some other diatoms can also indicate water' s contamination. This paper reviewed the research progress on the applications of diatom and diatom indices in river health assessment, pointed out the related existing problems, and put forward some future research directions, e. g., further perfect the classification and identification of diatoms, broadly carry out the researches of diatom indices upon different areas and conditions, pay more attention to the screening of diatom bio-integrality indices, and establish a benchmark which suits for the assessment of water quality. PMID:23286024

Li, Guo-Chen; Liu, Lu-San; Wang, Xing; Li, Li

2012-09-01

215

Copepod Population-Specific Response to a Toxic Diatom Diet  

PubMed Central

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

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

2012-01-01

216

Molecular characterization of Xenopus lamin LIV reveals differences in the lamin composition of sperms in amphibians and mammals  

PubMed Central

Lamins are nuclear intermediate filament proteins. They are involved in most nuclear activities and are essential for retaining the mechano-elastic properties of the nucleus. Somatic cells of vertebrates express lamins A, B1 and B2 while lamin LIII, a major component of the amphibian oocyte lamina is absent in mammals. The organization of the lamina of germ cells differs significantly from that of somatic cells. Mammalian spermatogenic cells express two short lamins, C2 and B3, that are splice isoforms of lamin A and B2, respectively. Here we identify the previously described Xenopus lamin LIV as splice variant of the lamin LIII gene. LIV contains 40 extra residues in coil 2A of the rod domain, which results in altered assembly properties. Xenopus lamin LIV and mammalian B3 assemble into short structures rather than into long IF-like filaments. Expression of lamin LIV is restricted to male germ cells suggesting that it might be the functional equivalent of mammalian lamin B3. We provide evidence that lamins C2 and B3 are restricted to the mammalian lineage and describe the lamin composition of Xenopus sperm. Our results show that the evolution of germ cell-specific lamins followed separate and distinctly different paths in amphibians and mammals.

von Moeller, Friederike; Barendziak, Tanja; Apte, Ketaki; Goldberg, Martin W

2010-01-01

217

Composite Laminate Tailoring with Probabilistic Constraints and Loads.  

National Technical Information Service (NTIS)

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 techni...

P. B. Thanedar C. C. Chamis

1990-01-01

218

Design Sensitivity Analysis of an Antisymmetric Angle-Ply Laminate.  

National Technical Information Service (NTIS)

Sensitivity of an optimally designed antisymmetric angle-ply laminate is investigated to determine the effect of variations in the design variables on the performance of the structure. The laminate is optimized with the objectives of minimizing the maximu...

S. Adali

1983-01-01

219

Calculation of the Room-Temperature Shapes of Unsymmetric Laminates.  

National Technical Information Service (NTIS)

A theory explaining the characteristics of the cured shapes of unsymmetric laminates is presented. The theory is based on an extension of classical lamination theory which accounts for geometric nonlinearities. A Rayleigh-Ritz approach to minimizing the t...

M. W. Hyer

1981-01-01

220

Laminated Ferrous Composites Based on Ultrahigh Carbon (UHC) Steels.  

National Technical Information Service (NTIS)

Ferrous laminated composites based on ultrahigh carbon (UHC) steel have been successfully manufactured by roll bonding below the Al transition temperature. Three unique mechanical property characteristics have been achieved by such lamination. First, rema...

O. D. Sherby J. Wadsworth D. W. Kum G. Deahn J. Whittenauer

1987-01-01

221

Behavior of Laminated and Filmed Glass in Severe Windstorm Environments.  

National Technical Information Service (NTIS)

The research addresses the behavior of heat strengthened laminated glass under conditions which represent a severe windstorm. Specimens laminated with two different interlayers were examined. The interlayers were polyvinyl butyral (PVB) 0.060 in. in thick...

C. P. Pantelides A. D. Horst R. B. Shankland J. E. Minor

1991-01-01

222

Hygrothermal Influence on Delamination Behavior of Graphite/Epoxy Laminates.  

National Technical Information Service (NTIS)

The hygrothermal effect on the fracture behavior of graphite-epoxy laminates was investigated to develop a methodology for damage tolerance predictions in advanced composite materials. Several T300/934 laminates were tested using a number of specimen conf...

A. Garg O. Ishai

1984-01-01

223

Nonlinear Laminate Analysis for Metal Matrix Fiber Composites.  

National Technical Information Service (NTIS)

A nonlinear laminate analysis is described for predicting the mechanical behavior (stress-strain relationships) of angleplied laminates in which the matrix is strained nonlinearly by both the residual stress and the mechanical load and in which additional...

C. C. Chamis J. H. Sinclair

1981-01-01

224

Fatigue Damage Mechanisms in Advanced Hybrid Titanium Composite Laminates.  

National Technical Information Service (NTIS)

Hybrid Titanium Composite Laminates (HTCL) are a type of hybrid composite laminate with promise for high-speed aerospace applications, specifically designed for improved damage tolerance and strength at high-temperature (350 F, 177 C). However, in previou...

W. S. Johnson D. W. Rhymer

2000-01-01

225

Oligocene early Miocene Antarctic nearshore diatom biostratigraphy  

NASA Astrophysics Data System (ADS)

Lower Oligocene (ca. 31 Ma) to lower Miocene (ca. 18.5 Ma) biosiliceous microfossils recovered from the Cape Roberts Project (CRP-2/2A) drill cores provide both paleoenvironmental and biostratigraphic information, enhancing our understanding of the geological history of the Victoria Land Basin, Antarctica. The biochronostratigraphic record obtained provides key data with which time-space-facies models may be developed. Assemblages of neritic and pelagic microfossils such as those from the CRP-2/2A drill cores provide links between the primarily pelagic microfossil-derived chronostratigraphy of the Southern Ocean and the facies models of the neritic zone. The CRP-2/2A holes drilled in the Victoria Land Basin, Antarctica during 1998 [Barrett, P.J., et al. (Eds.), 2001. Studies from the Cape Roberts Project, Ross Sea, Antarctica, Scientific Results of CRP-2/2A, Parts I and II: Terra Antartica, vol. 7(4/5), 665pp] include several sections that contain well-preserved and relatively abundant biosiliceous microfossils. Scherer et al. [2001. Oligocene and Lower Miocene Siliceous Microfossil Biostratigraphy of Cape Roberts Project Core CRP-2/2A, Victoria Land Basin, Antarctica. In: Barrett, P.J., Ricci, C.A. (Eds.) Studies from the Cape Roberts Project, Ross Sea, Antarctica, Scientific Report of CRP-2/2A, Terra Antartica, vol. 7(4), pp. 417-442] produced a biostratigraphic zonal framework consisting of 10 biozones; two of the zonal boundaries were correlated with the magnetostratigraphically calibrated Southern Ocean diatom biozonation. Many of the taxa observed and utilized in the above framework could not be assigned categorically to existing taxa, leading to use of informal nomenclature. We present an updated biostratigraphy and zonation scheme based on the latest taxonomic concepts and on new quantitative and qualitative siliceous microfossil data from the CRP-2/2A drill core, including formal description of four new diatom taxa used in the definition of Antarctic nearshore diatom zonal boundaries. New taxa formally proposed are Fragilariopsis truncata, Cymatosira palpebraforma, Rhizosolenia fidicularis, and Hemiaulus angustobrachiatus.

Olney, Matthew P.; Scherer, Reed P.; Harwood, David M.; Bohaty, Steven M.

2007-10-01

226

Improved pair-potential function for diatomic systems  

NASA Astrophysics Data System (ADS)

A three-parameter pair-potential model recently constructed is improved in the short- and long-range interaction regions. We demonstrate that this improved potential function is able to accurately describe the entire potentials of the ground-state van der Waals systems such as rare-gas, triplet H2, Alkali-helium, Alkaline-earth, and group 12 diatomic systems. All these systems show a single binding-energy relation in the attractive region. The improved function suggests a unique form for describing the potentials of diatomic systems ranging from strongly-bound to weakly-bound diatomic systems.

Xie, Jianing Colin; Kar, Tapas; Mishra, Sudhanshu K.; Xie, Rui-Hua

2014-02-01

227

Spatial paradigms of lotic diatom distribution: A landscape ecology perspective  

USGS Publications Warehouse

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

Passy, S. I.

2001-01-01

228

Diatoms on earth, comets, Europa and in interstellar space  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

229

A quantitative review of the Cenozoic diatom deposition history  

NASA Astrophysics Data System (ADS)

Marine planktonic diatoms play an important role today as one of the world's main primary producers, as the main organic carbon exporter to the deep sea and also as the main silica exporter balancing global chemical weathering. They were however a very minor component of the plankton at the beginning of the Cenozoic. Studies to date have focussed mainly on the evolution of their taxonomic diversity. Studies of changes in their actual global abundance over the Cenozoic are few, qualitative, and based on limited amounts of data. Reviewing their depositional pattern during the Cenozoic is therefore of interest in order to understand the modality, the context and, eventually, the cause of their rise; and to understand how diatom evolution affected the Cenozoic functioning of the ocean pump. We present here, based on a review of the literature coupled with a new data analysis of the full global ODP-DSDP Initial Reports smear slides descriptions, a quantitative synthesis of the depositional history of marine diatoms for the last 60 Myr. We also place these data in their paleogeographical context in order to understand the changes in diatom biogeography and what it says about Cenozoic paleoceanography. Diatoms first became widespread during the Middle Eocene. Two temporary major high-abundance events, one at the Eocene-Oligocene transition, another during the Late Oligocene were followed by decreases in the Middle Oligocene and Early Miocene. Diatom abundance in sediments shifted in the Mid-Miocene to globally higher values which have largely persisted to the modern day. Despite appearing initially during the Late Oligocene, the Southern Ocean circumpolar diatom accumulation belt only became a stable feature in the Mid-Miocene. At this time the main diatom deposition loci switched from the Atlantic to the Pacific and Indian Oceans, and mid-latitude upwelling zones appeared. Our findings provide support for the idea that diatoms, through their ecological role in the ocean's carbon pump, are responsible at least in part for Cenozoic changes in atmospheric carbon dioxide pressure and therefore changes in global climate state. Additionally, correlations between diatom abundance peaks and shifts in seawater strontium and osmium isotope composition hint at a strong control of weathering on diatom deposition and therefore indicates that diatom abundance can be useful to reconstruct Cenozoic history of weathering intensity.

Renaudie, Johan; Lazarus, David B.

2014-05-01

230

Flutter of laminated plates in supersonic flow  

NASA Technical Reports Server (NTRS)

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

Sawyer, J. W.

1975-01-01

231

Damage initiation and propagation in metal laminates  

SciTech Connect

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

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

1996-07-26

232

Nonlinear effects on composite laminate thermal expansion  

NASA Technical Reports Server (NTRS)

Analyses of Graphite/Polyimide laminates shown that the thermomechanical strains cannot be separated into mechanical strain and free thermal expansion strain. Elastic properties and thermal expansion coefficients of unidirectional Graphite/Polyimide specimens were measured as a function of temperature to provide inputs for the analysis. The + or - 45 degrees symmetric Graphite/Polyimide laminates were tested to obtain free thermal expansion coefficients and thermal expansion coefficients under various uniaxial loads. The experimental results demonstrated the effects predicted by the analysis, namely dependence of thermal expansion coefficients on load, and anisotropy of thermal expansion under load. The significance of time dependence on thermal expansion was demonstrated by comparison of measured laminate free expansion coefficients with and without 15 day delay at intermediate temperature.

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

1979-01-01

233

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

234

Development of tough, moisture resistant laminating resins  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

235

Structural reliability analysis of laminated CMC components  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

236

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

237

Preliminary evaluation of hybrid titanium composite laminates  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

238

Evaluation of Gas Permeability of CFRP Laminates under Cyclic Loadings  

NASA Astrophysics Data System (ADS)

This paper describes the experimental assessment of gas permeability of carbon fiber/toughened epoxy laminates under cyclic loadings as a fundamental research for the development of composite cryogenic propellant tank for reusable space transportation system. A thin-ply technique, which may contribute to the enhancement of damage resistance of CFRP laminates, is introduced herein, and the damage accumulation behaviors and gas permeability are compared between thin-ply laminates and standard laminates subjected to cyclic tension and impact.

Yokozeki, Tomohiro; Kuroda, Akiko; Yoshimura, Akinori; Ogasawara, Toshio; Aoki, Takahira

239

Edge Effects in Angle-Ply Composite Laminates  

Microsoft Academic Search

This paper presents the results of a zeroth-order solution for edge effects in angle-ply composite laminates obtained using perturbation tech niques and a limiting free body approach. The general solution for [±?]laminates is applied to the special case of a [±45]s graphite\\/epoxy lamin ate. Interlaminar stress distributions are obtained as a function of the laminate thickness-to-width ratio h\\/b and compared

Peter W. Hsu; Carl T. Herakovich

1977-01-01

240

Prediction of Composite Laminate Fracture: Micromechanics and Progressive Fracture  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

241

LZSA glass-ceramic laminates: Fabrication and mechanical properties  

Microsoft Academic Search

The aim of this work was to fabricate LiO2–ZrO2–SiO2–Al2O3 (LZSA) glass-ceramics laminates by laminated object manufacturing (LOM) and to characterise some properties of the laminates before and after sintering. Correlations between green tape properties, produced by aqueous tape casting, and the green and sintered laminate properties were also determined. Processing optimisation was based on a factorial design. The microstructure of

Cynthia M. Gomes; Antonio P. N. Oliveira; Dachamir Hotza; Nahum Travitzky; Peter Greil

2008-01-01

242

Calcium cyclotron resonance and diatom mobility.  

PubMed

The hypothesis that movement of biological ions may be predicted by cyclotron resonance theory applied to cell membranes is tested in these experiments. Diatoms (Amphora coffeaeformis) were chosen as the biosystem since they move or don't move, depending on how much calcium is transported across the membrane. The experiments demonstrate that a particular ion (calcium) is apparently moved across the cell membrane in response to the DC and AC values of magnetic flux densities (B) and the frequency derived from the cyclotron resonance theory. A clear resonance is shown and a rather sharp frequency response curve is demonstrated. The experiments also show a dose response as the AC value of the flux density is varied, and that odd harmonics of the basic cyclotron frequency are also effective. PMID:3663247

Smith, S D; McLeod, B R; Liboff, A R; Cooksey, K

1987-01-01

243

X-ray lasing in diatomic molecules  

NASA Astrophysics Data System (ADS)

We predict high-gain x-ray lasing in diatomic molecules by ultrafast core ionization of the C K- and O K-edges in CO and the N K-edge in N2 with an x-ray free-electron laser source. We solve generalized Maxwell-Bloch equations, keeping track of the electronic and nuclear degrees of freedom. By controlling the molecular alignment and thereby the alignment of the transition dipole moment polarization control of the emitted x-ray radiation is achievable. Despite the broad fluorescence bandwidth, the amplified x-ray emission shows a narrow spectrum. Preparing the initial vibrational quantum state, the x-ray emission frequency can be tuned within the fluorescence band.

Kimberg, Victor; Rohringer, Nina

2014-04-01

244

X-ray lasing in diatomic molecules  

NASA Astrophysics Data System (ADS)

We predict high-gain x-ray lasing in diatomic molecules by ultrafast core ionization of the C K- and O K-edges in CO and the N K-edge in N2 with an x-ray free-electron laser source. To estimate the spectral and temporal output of this molecular x-ray laser, we solve generalized Maxwell-Bloch equations, keeping track of the electronic and nuclear degrees of freedom. Despite the broad fluorescence bandwidth, the amplified x-ray emission shows a narrow spectrum. By controlling the molecular alignment and thereby the alignment of the transition dipole moment polarization and emission energy control of the x-ray laser radiation is achievable.

Kimberg, Victor; Zhang, Song Bin; Rohringer, Nina

2014-04-01

245

Manufacturing of Components of Fibre-Metal Laminates: An Overview.  

National Technical Information Service (NTIS)

To manufacture components of fiber-metal laminates the same processes can be used as for conventional materials. In some cases, however, the tools have to be adapted to this laminated material. The workshop properties of fiber-metal laminates are good for...

J. Sinke

1991-01-01

246

Multi-layer laminate structure and manufacturing method  

DOEpatents

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

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

2013-01-29

247

Multi-layer laminate structure and manufacturing method  

DOEpatents

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

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

2012-04-24

248

Manufacturing of Components of Fibre-Metal Laminates: An Overview.  

National Technical Information Service (NTIS)

To manufacture components of fiber metal laminates the same processes can be used as for conventional materials. In some cases, however, the tools have to be adapted to this laminated material. The workshop properties of fiber metal laminates are good for...

J. Sinke

1991-01-01

249

Antisymmetric Layup Of Precise Composite Laminates  

NASA Technical Reports Server (NTRS)

Warping of precise composite-material (graphite-fiber/epoxy-matrix) laminated panels reduced, according to proposal, by improved combination of design and method of fabrication. Essence of proposal to stack plies during fabrication in such pattern that effects of unavoidable ply-orientation errors in individual layers cancel each other out, on whole, in final product. Emerged from study of warping of composite-material laminated face sheets undergoing development for use as lightweight substrates for precise, curved mirrors in submillimeter-wave astronomical telescopes and optical communication systems.

Rapp, Donald; Lou, Michael C.; Kuo, Chin-Po

1995-01-01

250

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

251

Boedecker al. (2009) Cramton nuclear Lamine undifferentiated mesic maintained fluid state fluorescence recovery after photobleaching (FRAP). Data level Lamine B1 expression significant change throughout differentiation. implies LaminB1 protein undifferentiated ESC undergoing ordering change  

EPA Pesticide Factsheets

Did you mean: Boedecker al. (2009) Cramton nuclear Lamine undifferentiated mesic maintained fluid state fluorescence recovery after photobleaching (FRAP). Data level Lamine B1 expression significant change throughout differentiation. implies LaminB1 protein undifferentiated ESC undergoing ordering change ?

252

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

253

Molecular and Physiological Mechanisms of Diatom Fouling Phenomena.  

National Technical Information Service (NTIS)

This cooperative Augmentation Award for Science and Engineering Research Training has provided training for two doctoral students in several important areas of marine microalgal biofouling, including marine diatom mass culturing and adhesive isolation, bi...

M. R. Gretz K. D. Hoagland

1997-01-01

254

Calculations of some weakly bound diatomic molecular negative ions  

SciTech Connect

We examine the existence of stable bound states of some diatomic molecular ions where the neutral molecule itself is either unbound or barely bound. Two bound states have been found for the HeH[sup [minus

Li, Y.; Lin, C.D. (Department of Physics, Kansas State University, Manhattan, Kansas 66506-2601 (United States))

1999-09-01

255

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

256

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

257

UV effects on invertebrate and diatom assemblages of Greece  

Microsoft Academic Search

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

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

2000-01-01

258

Unicellular C4 photosynthesis in a marine diatom  

Microsoft Academic Search

Nearly 50 years ago, inorganic carbon was shown to be fixed in microalgae as the C3 compound phosphoglyceric acid. The enzyme responsible for C3 carbon fixation, ribulose-1,5-bisphosphate carboxylase (Rubisco), however, requires inorganic carbon in the form of CO2 (ref. 2), and Rubisco enzymes from diatoms have half-saturation constants for CO2 of 30-60µM (ref. 3). As a result, diatoms growing in

John R. Reinfelder; Anne M. L. Kraepiel; François M. M. Morel

2000-01-01

259

Differential response of marine diatoms to trace metals  

SciTech Connect

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

Tadros, M.G.; Mbuthia, P.; Smith, W. (Alabama A M Univ., Normal (USA))

1990-06-01

260

Diatoms Classification with Weighted Averaging Fuzzy Operators for Eutrophication Prevention  

Microsoft Academic Search

\\u000a The level of nutrients determines the triggering point of the eutrophication process, so it is very important to monitor these\\u000a levels. Diatoms react rapidly on nutrient changes and that makes them ideal eutrophication bio-indicators. In the relevant\\u000a literature there is known ecological reference for some diatoms, but for many of them these indicator features remain unidentified.\\u000a In order to fill

Andreja Naumoski; Kosta Mitreski

261

Vibrational energy transfer in diatom-triatom collisions  

Microsoft Academic Search

A quantum-dynamical method is described for calculating exact vibrational transition probabilities for the fixed angle scattering of a diatomic molecule with a linear triatomic molecule. The method can be used for any realistic diatom-triatom potential energy surface. Application of the technique is made to the collisions of N2(u) with CO2(v1v2), where u is the vibrational quantum number of N2 and

D. C. Clary

1981-01-01

262

Fourier transform differences and averaged similarities in diatoms.  

PubMed

Phase contrast photographs of diatoms are characterized from their Fourier transform taken through an optical diffractometer. The system output is placed on line to a PDP11/40 providing digital subtraction of two output spectral distributions due to different species. Differences obtained in this manner are used for characterizing various species. An average Fourier transform taken through coherent additions is also analyzed to find common features in a given set of diatoms. PMID:20212908

Almeida, S P; Fujii, H

1979-05-15

263

The V-T energy transfer in collisions of diatomics  

NASA Technical Reports Server (NTRS)

A general approach evaluating the transition probabilities for the V-T exchange, involving highly excited levels and the Delta-v greater than 1 transitions, in diatomic gases is presented. Examples of numerical results are given for a number of transitions in nitrogen and oxygen molecules in the ground electronic states. The approach can be used for the V-T exchange involving diatomic molecular ions.

Kunc, Joseph A.

1991-01-01

264

Laminating Polyimide Films: New processes yield void-free flexible laminates.  

National Technical Information Service (NTIS)

This citation summarizes a one-page announcement of technology available for utilization. A new process for laminating large areas of high-temperature-polyimide film has applications in vehicle construction and in preparing flexible printed circuits. Line...

1983-01-01

265

Automatic screening and multifocus fusion methods for diatom identification  

NASA Astrophysics Data System (ADS)

The first part of this paper presents a new method for the classification and screening of diatoms in images taken from water samples. The technique can be split into three main stages: segmentation, object feature extraction and classification. The segmentation part consists of two modified thresholding and contour tracing techniques in order to detect the majority of objects present at the sample. From the segmented objects, several features have been extracted and analyzed. For the classification, a diatom training set was considered and the centroids, means and variances of four different classes were found. For the identification process diatoms were classified according with their Mahalanobis distance. The results show the method ability to select at least 80% of usable diatoms from images contaminated with debris. Secondly, full automation of the diatom classification is achieved when multi-focal microscopy is utilized for water sample acquisition. In this case, a necessary preprocessing step is image fusion. A novel wavelet-based fusion method proposed here returns a sharp image that can be directly used for segmentation. For a better understanding of the diatom shape, a 2.5D reconstruction is given.

Forero, Manuel; Sroubek, Filip; Flusser, Jan; Redondo, Rafael; Cristobal, Gabriel

2004-01-01

266

Mapping glycoconjugate-mediated interactions of marine Bacteroidetes with diatoms.  

PubMed

The degradation of diatoms is mainly catalyzed by Bacteroidetes and this process is of global relevance for the carbon cycle. In this study, a combination of catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) and fluorescent lectin binding analysis (FLBA) was used to identify and map glycoconjugates involved in the specific interactions of Bacteroidetes and diatoms, as well as detritus, at the coastal marine site Helgoland Roads (German Bight, North Sea). The study probed both the presence of lectin-specific extracellular polymeric substances (EPS) of Bacteroidetes for cell attachment and that of glycoconjugates on diatoms with respect to binding sites for Bacteroidetes. Members of the clades Polaribacter and Ulvibacter were shown to form microcolonies within aggregates for which FLBA indicated the presence of galactose containing slime. Polaribacter spp. was shown to bind specifically to the setae of the abundant diatom Chaetoceros spp., and the setae were stained with fucose-specific lectins. In contrast, Ulvibacter spp. attached to diatoms of the genus Asterionella which bound, among others, the mannose-specific lectin PSA. The newly developed CARD-FISH/FLBA protocol was limited to the glycoconjugates that persisted after the initial CARD-FISH procedure. The differential attachment of bacteroidetal clades to diatoms and their discrete staining by FLBA provided evidence for the essential role that formation and recognition of glycoconjugates play in the interaction of bacteria with phytoplankton. PMID:23809997

Bennke, Christin M; Neu, Thomas R; Fuchs, Bernhard M; Amann, Rudolf

2013-09-01

267

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

268

Biochemical and Molecular Genetic Studies on Biosilica Morphogenesis in Diatoms  

NASA Astrophysics Data System (ADS)

Diatoms are a large group of unicellular microalgae encased by silica cell walls that exhibit species-specific micro-and nanopatterns. Previously, we have characterized from diatoms unique phosphoproteins (termed silaffins) and unusually long polyamine chains (termed LCPA), which have both been implicated in biosilica formation. While the chemical structures of LCPA are largely conserved among different diatom species, the silaffins exhibit extensive structural variations. In vitro studies on the silica formation activities of silaffins and LCPA from the diatom Thalassiosira pseudonana indicate that silica morphogenesis is primarily determined by silaffins rather than LCPA. Recently, the complete genome sequence of T. pseudonana has become available, which for the first time opens the door to employ functional genomic approaches for studying the mechanism of silica biomineralization. To this end we have established the first genetic transformation system for T. pseudonana, which will be instrumental for analyzing the functions of silaffins in vivo, and for identifying new components of the diatom silica forming machinery. Here we describe the current knowledge on the structures and properties of silaffins and LCPA, the methods for genetic manipulation of T. pseudonana, and the first experimental steps towards functional genomics in diatoms.

Kroger, N.; Poulsen, N.

2006-12-01

269

Marine Polysaccharide Networks and Diatoms at the Nanometric Scale  

PubMed Central

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

Svetlicic, Vesna; Zutic, Vera; Pletikapic, Galja; Radic, Tea Misic

2013-01-01

270

Do benthic diatoms influence erosion thresholds of coastal subtidal sediments?  

NASA Astrophysics Data System (ADS)

This study reports diatom cell abundance, concentrations of water-soluble and water-insoluble carbohydrates, and concentrations of chlorophyll—a equivalents as indicators of microbial exudates and biomass in the uppermost sediment layer of two coastal sites (19 m water depth: fine sand; 25 m water depth: mud) in Mecklenburg Bight, south-western Baltic Sea. Correlation analysis with experimentally determined erosion thresholds measured in five different periods of a year showed that the sediment water content and the content of water-soluble carbohydrates may indicate erosion thresholds for both sediment types. Erosion thresholds were significantly negatively correlated with sediment water content at the mud site. At both sites, colloidal carbohydrates, as indicators for diatom EPS, showed significantly negative correlations with sediment water content and no correlation with diatom biomass. Therefore, following current interpretation, we argue that micro-biostabilsation effects of benthic microalgae play a minor role in the investigation area. Light is likely to be insufficient for phototrophic growth on the seafloor of the investigated sites most of the year, as indicated by in situ measurements and calculated values of photosynthetically active radiation. We consider lateral transport of benthic diatoms from shallower to deeper areas of Mecklenburg Bight and subsequent to be the mechanism influencing diatom abundance. Exhaustive biofilms are absent at these depths and mass erosion is not likely to be affected by benthic diatoms.

Ziervogel, Kai; Forster, Stefan

2006-01-01

271

Fatigue damage development of various CFRP-laminates  

NASA Technical Reports Server (NTRS)

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

Schulte, K.; Baron, CH.

1988-01-01

272

Nonlinear laminate analysis for metal matrix fiber composites  

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

273

Nonlinear laminate analysis for metal matrix fiber composites  

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

274

Progressive delamination in polymer matrix composite laminates: A new approach  

NASA Technical Reports Server (NTRS)

A new approach independent of stress intensity factors and fracture toughness parameters has been developed and is described for the computational simulation of progressive delamination in polymer matrix composite laminates. The damage stages are quantified based on physics via composite mechanics while the degradation of the laminate behavior is quantified via the finite element method. The approach accounts for all types of composite behavior, laminate configuration, load conditions, and delamination processes starting from damage initiation, to unstable propagation, and to laminate fracture. Results of laminate fracture in composite beams, panels, plates, and shells are presented to demonstrate the effectiveness and versatility of this new approach.

Chamis, C. C.; Murthy, P. L. N.; Minnetyan, L.

1992-01-01

275

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

276

Dynamic Composite Laminate Finite Element Analysis.  

National Technical Information Service (NTIS)

The analysis of plate like structures such as blades built-up with composite laminate fibers requires the modification of an existing finite element computer program to include the coupling of in-plane stretching with out-of-plane bending of a plate. An i...

J. O'Callahan J. A. McElman

1981-01-01

277

[Laminitis in cattle: a literature review].  

PubMed

Worldwide afflictions of the claws belong to the economically important diseases in dairy cattle. The significance of laminitis has gained importance in the last years since the condition is regarded as the most important predisposing factor for the development of lesions such as sole ulcer, white line disease and heel horn erosion. Apart from the clinical stages (acute, subacute, chronic, chronic-recurrent) there is also a subclinical form of laminitis which does not cause lameness. It is characterized by soft yellowish sole and heel horn with haemorrhages in the sole and along the white line. Laminitis is a multifactorial event in which nutrition, genetic disposition and the perinatal period, combined with the associated diseases of high-yielding cows, have a particular significance. Currently, two principally different hypotheses on the pathogenesis are discussed. The generally accepted theory bases on a disturbance in the microcirculation of the corium. According to the other theory the circulatory disturbances are secondary to changes which occur in the horn producing cells of the stratum basale of the epidermis. The predisposing factors and the pathogenesis of laminitis are discussed in the light of possible therapeutic and prophylactic measures. PMID:7855848

Lischer, C; Ossent, P

1994-10-01

278

Tevatron I: Large Bore Quad Lamination Analysis.  

National Technical Information Service (NTIS)

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

M. Leininger

1982-01-01

279

Behavior of bolted joints in composite laminates  

SciTech Connect

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

Jurf, R.A.

1986-01-01

280

Laminates Reinforced By Short Transverse Rods  

NASA Technical Reports Server (NTRS)

Short transverse rods incorporated into laminated composite panels to increase interlaminar strengths of panels, according to proposal. Rods help panels resist delamination caused by impacts from dropped tools or, in vehicles, by debris. Inserted into selected individual internal layers during preimpregnation.

Farley, Gary L.

1993-01-01

281

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

282

Fatigue Damage Mechanics of Composite Laminates,  

National Technical Information Service (NTIS)

The mechanics of fatigue damage in composite laminates is developed. Damage which results from such mechanisms as delamination and matrix cracking results in a loss of stiffness of the material. A change in stiffness is modelled in terms of the dominant m...

P. W. R. Beaumont

1987-01-01

283

Penetration and perforation of thick FRP laminates  

Microsoft Academic Search

Analytical equations are given for the prediction of the penetration and perforation of thick FRP laminates struck normally by missiles over a wide range of impact velocities. The missiles have different nose shapes (i.e. truncated, conical, flat, ogival and hemispherical). The formulation is based on the assumption that the deformations are localized and that the mean pressure offered by the

H. M. Wen

2001-01-01

284

BOND OF FRP LAMINATES TO CONCRETE  

Microsoft Academic Search

Fiber reinforced polymer (FRP) laminates are being successfully used for strengthe ning of existing reinforced concrete structures. Bond of the FRP reinforcement to the concrete substrate is of critical importance for the effectiveness of the technique. In this project, flexural test specimens were prepared to address some of the factors expected to affect bond, namely, bonded length, concrete strength, number

Laura De Lorenzis; Brian Miller; Antonio Nanni

285

Multiscale analyses of fibre metal laminates  

Microsoft Academic Search

The advance of composites used in aerospace, civil and biomechanical engineering and other technology branches over the last decades has led to a substantial increase in the application of these materials. In addition, the search for new and improved materials in aerospace industry has stimulated the development of hybrid materials partly made out of composites, such as Fibre-Metal Laminates (FMLs).

M. V. Cid Alfaro

2008-01-01

286

Development of a ferromagnetic fibre metal laminate  

Microsoft Academic Search

This study introduces the concept of a multifunctional fibre metal laminate (FML), specifically, one which utilises ferromagnetic foil in combination with carbon fibre reinforced epoxy to produce a FML which is magnetically functional and structurally efficient. The aim is to develop such a material\\/structure for use in future high output, low mass, electrical machines and embedded actuation. The work presented

G. P. McCombe; J. A. Etches; P. H. Mellor; I. P. Bond

2011-01-01

287

Static Properties of Fibre Metal Laminates  

Microsoft Academic Search

In this article a brief overview of the static properties of Fibre Metal Laminates is given. Starting with the stress-strain relation, an effective calculation tool for uniaxial stress-strain curves is given. The method is valid for all Glare types. The Norris failure model is described in combination with a Metal Volume Fraction approach leading to a useful tool to predict

M. Hagenbeek; C. van Hengel; O. J. Bosker; C. A. J. R. Vermeeren

2003-01-01

288

Property Optimisation in Fibre Metal Laminates  

Microsoft Academic Search

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

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

2004-01-01

289

Fatigue initiation in fibre metal laminates  

Microsoft Academic Search

It is assumed that fatigue crack initiation in Fibre Metal Laminates is determined by the stress cycles in the metal layers only. It is further assumed that if the stress cycles in the metal layers are known, the fatigue initiation life can be established using S–N data available for the given metal alloy.The internal stresses in the aluminium layers of

J. J. Homan

2006-01-01

290

Cooled, Laminated Radial Turbine Demonstration Program.  

National Technical Information Service (NTIS)

A low-cost, high-temperature radial turbine has been developed that demonstrates the technology required to manufacture a small, cooled turbine using photoetched laminates bonded together to form a complete wheel. An advanced long-life and high-performanc...

R. W. Vershure G. D. Large L. J. Meyer M. J. Egan

1981-01-01

291

Residual Stresses in Polymer Matrix Composite Laminates  

Microsoft Academic Search

Residual stresses in composites are induced during fabrication and by environmental exposure. The theory formulated can describe the shrinkage commonly observed after a thermal expansion test. Comparison between the analysis and experimental data for [02\\/± 45]s laminates of various material systems indicates that the residual stress-free temperature can be lower than the curing temperature, depending on the curing process. Ef

H. Thomas Hahn

1976-01-01

292

Reliability analysis of continuous fiber composite laminates  

NASA Technical Reports Server (NTRS)

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

Thomas, David J.; Wetherhold, Robert C.

1990-01-01

293

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

294

A new damage model for composite laminates  

Microsoft Academic Search

Aircraft composite structures must have high stiffness and strength with low weight, which can guarantee the increase of the pay-load for airplanes without losing airworthiness. However, the mechanical behavior of composite laminates is very complex due the inherent anisotropy and heterogeneity. Many researchers have developed different failure progressive analyses and damage models in order to predict the complex failure mechanisms.

Marcelo Leite Ribeiro; Volnei Tita; Dirk Vandepitte

295

Multifunctional microtruss laminates: textile synthesis, and properties  

Microsoft Academic Search

Open cell periodic metal truss structures can exhibit significantly higher stiffnesses and strengths than stochastic cellular metal structures of the same relative density while still providing high mechanical energy absorption and efficient heat exchange opportunities. Here, a potentially inexpensive textile-based approach to the synthesis of periodic metal microtruss laminates is reported. The process consists of selecting a wire weave, laying

D. J. Sypeck; H. N. G. Wadley

2001-01-01

296

Micromechanics of Composite Laminate Compression Failures.  

National Technical Information Service (NTIS)

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...

E. G. Guynn W. L. Bradley

1988-01-01

297

Composite laminated shells under internal pressure  

Microsoft Academic Search

A theoretical study is conducted of the response of filament-wound composite shells under internal pressure; a system of sixth-order ordinary differential equations is obtained by means of the cylindrically anisotropic elasticity field equations and Lekhnitskii's (1963) stress functions. The general expressions for the stresses and displacements in the laminated composite shells under internal pressure are discussed. Attention is given to

F. G. Yuan

1992-01-01

298

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

299

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

300

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

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

301

Partners and post-translational modifications of nuclear lamins  

PubMed Central

Nuclear intermediate filament networks formed by A- and B-type lamins are major components of the nucleoskeleton that are required for nuclear structure and function, with many links to human physiology. Mutations in lamins cause diverse human diseases (‘laminopathies’). At least fifty-four partners interact with human A-type lamins directly or indirectly. The less studied human lamins B1 and B2 have twenty-three and seven reported partners, respectively. These interactions are likely to be regulated at least in part by lamin post-translational modifications. This review summarizes the binding partners and post-translational modifications of human lamins and discusses their known or potential implications for lamin function.

Simon, Dan N.; Wilson, Katherine L.

2013-01-01

302

Tensile stress-strain behavior of boron/aluminum laminates  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

303

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

304

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

NASA Astrophysics Data System (ADS)

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

Satheesh, Sathianeson; Wesley, Samuel Godwin

2012-12-01

305

Species-dependent silicon isotope fractionation by marine diatoms  

NASA Astrophysics Data System (ADS)

Fractionation of silicon (Si) isotopes was measured in seven species (nine strains) of polar and sub-polar marine diatoms grown in semi-continuous unialgal cultures under optimal irradiance and temperature for each diatom strain. Results from this work provide the first evidence that Si isotope fractionation by diatoms is species-dependent. The greatest difference in the Si isotope fractionation factor (?) was observed between two Southern Ocean diatoms, Fragilariopsis kerguelensis (-0.54‰, average for two strains) and Chaetoceros brevis (-2.09‰). The ? for the other species, both polar and sub-polar, ranged from -0.72‰ to -1.21‰. The two remaining polar diatoms had ? values of -0.74 ± 0.05‰ for Thalassiosira antarctica, and -1.21 ± 0.04‰ for Thalassiosira nordenskioeldii, while the sub-polar species had ? values of -0.72 ± 0.04‰ for Thalassiosira weissflogii, -0.88 ± 0.06‰ for Thalassiosira pseudonana (CCCM58), -0.97 ± 0.14‰ for Thalassiosira pseudonana (CCMP1014), and -1.15 ± 0.03‰ for Porosira glacialis. The range in ? for the diatoms evaluated in this study may be large enough to significantly impact the Si isotope composition measured in diatom opal (?30Si-bSiO2) from marine sediments and its subsequent interpretation. To test the influence of diatom taxonomic composition on ?30Si-bSiO2, we developed a model that considered the relative abundance of diatom species and the ? values (from this study) for each species present within the sediment core (i.e. weighted-average ?). The model was applied to records from a Southern Ocean sediment core (TN057-13) where both diatom abundance and ?30Si-bSiO2 data were available. The analysis indicated that 67% of the variation in ?30Si-bSiO2 could be explained by species-dependent Si isotope fractionation. We suggest that future work should assess phytoplankton taxonomic composition when using ?30Si-bSiO2 as a proxy for Si utilization.

Sutton, Jill N.; Varela, Diana E.; Brzezinski, Mark A.; Beucher, Charlotte P.

2013-03-01

306

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

SciTech Connect

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

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

2005-08-12

307

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

308

Dispersion coefficients for alkali-metal diatoms  

SciTech Connect

The knowledge of the long-range interaction between atoms and molecules is of fundamental importance for low-energy and low-temperature collisions. The electrostatic interaction between the charge distributions of two ground-state alkali-metal atoms can be expanded in powers of 1/R, the internuclear distance. The coefficients corresponding to the expansion powers of R{sup -6}, R{sup -8}, and R{sup -10} are calculated exactly using a numerical technique originally developed for determining resonance profile near an absorption line. These coefficients are evaluated by integrating the dynamic electric multipole polarizabilities at imaginary frequencies which are in turn obtained by solving two coupled inhomogeneous differential equations. Highly accurate one-electron model potentials are developed to represent the motion of the valence electron in the field of the closed alkali positive ion core. The numerical results for the constants C{sub 6}, C{sub 8}, and C{sub 10} for the homo- and hetero-nuclear alkai diatoms are compared with other calculations.

Dalgarno, A.; Marinescu, M.; Sadeghpour, H.R. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)

1993-05-01

309

Impulse formalism for atom-diatom collisions  

SciTech Connect

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

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

1991-01-01

310

The structural response of unsymmetrically laminated composite cylinders  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

311

Adhesion and motility of fouling diatoms on a silicone elastomer.  

PubMed

Recent demands for non-toxic antifouling technologies have led to increased interest in coatings based on silicone elastomers that 'release' macrofouling organisms when hydrodynamic conditions are sufficiently robust. However, these types of coatings accumulate diatom slimes, which are not released even from vessels operating at high speeds (>30 knots). In this study, adhesion strength and motility of three common fouling diatoms (Amphora coffeaeformis var. perpusilla (Grunow) Cleve, Craspedostauros australis Cox and Navicula perminuta Grunow) were measured on a poly-dimethylsiloxane elastomer (PDMSE) and acid-washed glass. Adhesion of the three species was stronger to PDMSE than to glass but the adhesion strengths varied. The wall shear stress required to remove 50% of cells from PDMSE was 17 Pa for Craspedostauros, 24 Pa for Amphora and >53 Pa for Navicula; the corresponding values for glass were 3, 10 and 25 Pa. In contrast, the motility of the three species showed little or no correlation between the two surfaces. Craspedostauros moved equally well on glass and PDMSE, Amphora moved more on glass initially before movement ceased and Navicula moved more on PDMSE before movement ceased. The results show that fouling diatoms adhere more strongly to a hydrophobic PDMSE surface, and this feature may contribute to their successful colonization of low surface energy, foul-release coatings. The results also indicate that diatom motility is not related to adhesion strength, and motility does not appear to be a useful indicator of surface preference by diatoms. PMID:15804716

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

2004-12-01

312

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

313

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

National Technical Information Service (NTIS)

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

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

1977-01-01

314

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

EPA Science Inventory

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

315

Current status of standardized nonmetallic cryogenic laminates  

SciTech Connect

Kasen and Schramm review the ongoing efforts to provide a commercial supply of standardized and controlled-performance laminates to meet the short-term needs of the cryogenic industry for the critical components in MFE superconducting magnet design and construction. The approach provides a basis for systematic development of material variants and for new materials as required to meet the needs of future designs. The approach recognizes the development of nonmetallic insulators and structural supports in magnets subjected to intense irradiation at 4 K will require a much better understanding of all the factors affecting material performance in this environment and that this will be achieved only by an interdisciplinary approach. The lack of a terminology which would allow a designer to sepcify nonmetallic laminate materials by a performance criteria is a continuing problem. A long-range effort is needed.

Kasen, M.B.; Schromm, R.E.

1982-01-01

316

High energy impact on woven laminates  

NASA Astrophysics Data System (ADS)

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

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

2003-09-01

317

Thermomechanical postbuckling analysis of laminated composite shells  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

318

Damage growth in composite laminates with interleaves  

NASA Technical Reports Server (NTRS)

The influence of interleaves on the fracture behavior of laminated composites is investigated. The geometry of the composite consists of a cracked layer, bonded between two half-planes, which is separated by thin, low modulus, interleaves. The interleaves are modeled as uncoupled tension and shear springs. A stress analysis is carried out for a crack which may grow up to and spread along the interface. Integral transform techniques are used to develop the solution in terms of singular integral equations. An asymptotic analysis reveals logarithmic singularities in the critical stresses for the case of a broken layer. The equations are solved numerically and the effect of damage on critical stresses is studied. Initial results indicate that the interleaf gives a significant reduction in stresses in the adjacent regions and, if properly selected, should result in a more damage tolerant laminate.

Goree, James G.; Kaw, Autar K.

1987-01-01

319

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

PubMed

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

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

2011-10-01

320

Residual stresses in polymer matrix composite laminates  

NASA Technical Reports Server (NTRS)

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

Hahn, H. T.

1976-01-01

321

Processing and mechanical characterization of alumina laminates  

Microsoft Academic Search

Single-phase ceramics that combine property gradients or steps in monolithic bodies are sought as alternatives to ceramic composites made of dissimilar materials. This work describes novel processing methods to produce stepped-density (or laminated) alumina single-phase bodies that maintain their mechanical integrity. One arrangement consists of a stiff, dense bulk material with a thin, flaw tolerant, porous exterior layer. Another configuration

John K. Montgomery

2002-01-01

322

Laminated grid and web magnetic cores  

DOEpatents

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

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

1984-01-01

323

Aging and nuclear organization: lamins and progeria  

Microsoft Academic Search

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

Leslie C Mounkes; Colin L Stewart

2004-01-01

324

Free vibration of moving laminated composite plates  

Microsoft Academic Search

Two-dimensional axially moving materials have a wide range of industrial applications such as papers, plastics and composites in producing lines, power transmission and conveyor belts, etc. In many of these instances, the moving material is not isotropic, but is a single-layer orthotropic material or consists of several orthotropic layers.In this article, free vibration of axially moving symmetrically laminated plates subjected

S. Hatami; M. Azhari; M. M. Saadatpour

2007-01-01

325

LATERAL LAMINATION APPROACH FOR MULTILAYER PIEZOELECTRIC MICROACTUATOR  

Microsoft Academic Search

This paper reports a simple lateral lamination scheme for the fabrication of multilayer piezoelectric actuators. The fabrication scheme consists of dicing of a high-d 33 piezoelectric coefficient lead zirconate titanate (PZT) material, photolithographic high- aspect-ratio SU-8 definition of electrical isolation, and micromolding of conductive polymer electrodes. Backside and inclined UV exposure has been exploited to secure the 1mm-thick SU-8 pillar

Xiaosong Wu; Guang Yuan; Seong-O Choi; Yanzhu Zhao; Seong-Hyok Kim; Yong-Kyu Yoon; Mark G. Allen

326

Delamination buckling of fibre–metal laminates  

Microsoft Academic Search

A fibre–metal laminate is a composite of metal and fibre-reinforced prepreg layers. An example of such a material is Glare. It consists of alternating layers of aluminium and glass-fibre-reinforced prepreg. The material can be sensitive to delamination buckling, which occurs when a partially delaminated panel is subjected to a compressive force. The interaction of local buckling and extension of the

J. J. C. Remmers; R. de Borst

2001-01-01

327

Impact loading on fibre metal laminates  

Microsoft Academic Search

Static identation and low and high velocity impact tests are conducted on specimens with a circular clamped test area. Monolithic A1 2024-T3 and 7075-T6, various grades of Fibre Metal Laminates (FML), and composites are tested. The energy to create the first crack for FML with aramid and carbon fibres is comparable to fibre reinforced composite materials and is relatively low

A. Vlot

1996-01-01

328

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

329

Static contact crushing of composite laminated shells  

Microsoft Academic Search

The crush behavior of carbon-epoxy composite laminated shells with three different curvatures is investigated. The FEM package ABAQUS and the user-defined material subroutine (UMAT) based on the concept of progressive stiffness degradation were employed to simulate crushing until the specimens totally collapsed. The 2-D delamination propagation proposed by Davies et al. is considered to be an additional failure mechanism for

C. H. Huang; Y. J. Lee

2004-01-01

330

Surface Activated Bonding Method for Flexible Lamination  

Microsoft Academic Search

A short review is given on the flexible lamination of Cu\\/LCP by using the modified surface activated bonding (SAB) method. It includes a comprehensive investigation on the adhesion improvement and mechanism, interface quality in terms of mechanical and electrical integrity, and fine pitch patterning [5-7]. Ar-rf plasma cleans the LCP surface and produces dangling sites on the LCP with reduced

M. M. R. Howlader; T. Suga

2007-01-01

331

Scaling effects in angle-ply laminates  

NASA Technical Reports Server (NTRS)

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

Kellas, Sotiris; Morton, John

1992-01-01

332

Characteristics of laminates with delamination control strips  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

333

Ultrastructural study of laminated urinary stone.  

PubMed

Several modalities of stone analysis are utilised in different laboratories. However, the treating clinician finds it hard to assess the initiation and progression of stone formation. The pathogenesis of calculogenesis still remains a mystery. The purpose of this paper is to assess the pathological mechanisms of stone nucleation and growth by observing the ultra microscopic morphology of the different layers of laminated stones; 130 fragments from 28 randomly selected laminated stones of more than 10-mm diameter were analysed. Wet chemical analysis of the stones was performed. Surface and cross-sectional morphology of the entire stones and the individual fragments was assessed using optical microscopy and images were recorded using ordinary camera. They were further analysed using FTIR for confirmation. By morphological analysis, whewellite, weddellite, uric acid, and phosphate were the main minerals identified. Mixtures of these minerals were also found. Concentric lamination, radial striation, frond formation, and amorphous pattern were the main cross-sectional morphologies obtained. The calculi analysed had differences in their outer and inner portions. This was more pronounced in stones containing predominantly whewellite and uric acid. Whewellite was the outer component in most mixed stones. Uric acid was more in the inner layers of mixed stones than the surface. PMID:19657634

Fazil Marickar, Y M; Varma, Luxmi; Koshy, Peter

2009-10-01

334

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

335

Extracellular Matrix Assembly in Diatoms (Bacillariophyceae)1  

PubMed Central

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

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

1998-01-01

336

Bound-free Spectra for Diatomic Molecules  

NASA Technical Reports Server (NTRS)

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

Schwenke, David W.

2012-01-01

337

Barium uptake and adsorption in diatoms  

NASA Astrophysics Data System (ADS)

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

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

2005-06-01

338

Complete sequence of the mitochondrial genome of a diatom alga Synedra acus and comparative analysis of diatom mitochondrial genomes.  

PubMed

The first two mitochondrial genomes of marine diatoms were previously reported for the centric Thalassiosira pseudonana and the raphid pennate Phaeodactylum tricornutum. As part of a genomic project, we sequenced the complete mitochondrial genome of the freshwater araphid pennate diatom Synedra acus. This 46,657 bp mtDNA encodes 2 rRNAs, 24 tRNAs, and 33 proteins. The mtDNA of S. acus contains three group II introns, two inserted into the cox1 gene and containing ORFs, and one inserted into the rnl gene and lacking an ORF. The compact gene organization contrasts with the presence of a 4.9-kb-long intergenic region, which contains repeat sequences. Comparison of the three sequenced mtDNAs showed that these three genomes carry similar gene pools, but the positions of some genes are rearranged. Phylogenetic analysis performed with a fragment of the cox1 gene of diatoms and other heterokonts produced a tree that is similar to that derived from 18S RNA genes. The introns of mtDNA in the diatoms seem to be polyphyletic. This study demonstrates that pyrosequencing is an efficient method for complete sequencing of mitochondrial genomes from diatoms, and may soon give valuable information about the molecular phylogeny of this outstanding group of unicellular organisms. PMID:20309551

Ravin, Nikolai V; Galachyants, Yuri P; Mardanov, Andrey V; Beletsky, Alexey V; Petrova, Darya P; Sherbakova, Tatyana A; Zakharova, Yuliya R; Likhoshway, Yelena V; Skryabin, Konstantin G; Grachev, Mikhail A

2010-06-01

339

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

340

Understanding amine catalyzed silica polymerization : diatoms as bioarchitects.  

SciTech Connect

Current state-of-the-art biomimetic methodologies employed worldwide for the realization of self-assembled nanomaterials are adequate for certain unique applications, but a major breakthrough is needed if these nanomaterials are to obtain their true promise and potential. These routes typically utilize a 'top-down' approach in terms of controlling the nucleation, growth, and deposition of structured nanomaterials. Most of these techniques are inherently limited to primarily 2D and simple 3D structures, and are therefore limited in their ultimate functionality and field of use. Zeolites, one of the best-known and understood synthetic silica structures, typically possess highly ordered silica domains over very small length scales. The development of truly organized and hierarchical zeolites over several length scales remains an intense area of research world wide. Zeolites typically require high-temperature and complex synthesis routes that negatively impact certain economic parameters and, therefore, the ultimate utility of these materials. Nonetheless, zeolite usage is in the tons per year worldwide and is quickly becoming ubiquitous in its applications. In addition to these more mature aspects of current practices in materials science, one of the most promising fields of nanotechnology lies in the advent and control of biologically self-assembled materials, especially those involved with silica and other ceramics such as hydroxyapatite. Nature has derived, through billions of years of evolutionary steps, numerous methods by which fault-tolerant and mechanically robust structures can be created with exquisite control and precision at relatively low temperature ranges and pressures. Diatoms are one of the best known examples that exhibit this degree of structure and control known that is involved with the biomineralization of silica. Diatoms are eukaryotic algae that are ubiquitous in marine and freshwater environments. They are a dominant form of phytoplankton critical to global carbon fixation. The silicified cell wall of the diatom is called the frustule, and the intricate silica structure characteristic of a given species is known as the valve. There are two general classes of diatoms, based on their overall morphologies, the pennate and centric. Diatoms achieve their silicified structures in exact fashion through genetically inspired design rules coupled with precisely directed biochemistry occurring at temperatures ranging from a few degrees Celsius (polar species) to temperatures just over room temperature (tropical species). Different species of diatoms produce markedly different structures. To start with, there are two basic types of frustule macromorphologies: pennate diatoms display bilateral symmetry and centric diatoms show radial symmetry. There are thousands of permutations of these two basic forms and the micromorphology of the valve can be quite complex with all types of pore arrangements and morphologies (Figure 1.1). The detailed morphology of the cell wall of a given diatom species is reproduced with exactness, because the process is genetically encoded. Three types of cell wall proteins have been identified in diatoms; the frustulins, pleuralins, and silaffins. Frustulins are cell wall proteins that form an organic coat to protect the silica structures from dissolution into the aqueous environment. Pleuralins are associated with a specific subcomponent of the frustule during cell division, and play a role in hypotheca-epitheca development. Silaffins from Cylindrotheca fusiformis are short chain-length peptides that play a direct role in the silica polymerization process, and possess unique biochemical post-translation functionalization. Larger proteins with silaffin activity have recently been described in Thalassiosira pseudonana. Frustulins and pleuralins play no role in silica polymerization or structure formation in diatoms, whereas the silaffins are one of the primary polymerization determinants. In addition to the silaffins, a class of long-chain polyamines associated with diatom silica has been

Spoerke, Erik David; Aubry, Sylvie; Lane, Pamela; Robinson, David B; Bauer, Christina A.; Zendejas, Frank; Tran, Huu; Lane, Todd W.; Simmons, Blake Alexander

2007-10-01

341

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

342

Light transmission of the marine diatom Coscinodiscus wailesii  

NASA Astrophysics Data System (ADS)

The results of a detailed investigation of light transmission behavior of a centric marine diatom species Coscinodiscus wailesii are reported. We measured 3-dimentional intensity distributions of both broadband and monochromatic light transmitted through individual valves of the diatom in air and water. Cross-sectional intensity profiles of transmitted light indicates valves of C. wailesii can concentrate light into certain regions. At a distance from the valve shorter than its diameter, light intensities close to the optical axis are relatively higher than those in the surrounds; at a longer distance, transmitted light intensities display ring-shaped profiles. The distance showing this light concentration characteristic becomes shorter as the wavelength of incoming light goes up. These results may offer insight into the understanding of biological functions of diatom frustules' intricate structures and inspire new optical biomimetic applications.

Hsu, Shih-Hsin; Paoletti, Camille; Torres, Moacir; Ritchie, Raymond J.; Larkum, Anthony W. D.; Grillet, Christian

2012-03-01

343

Chloroplast-mitochondria cross-talk in diatoms.  

PubMed

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

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

2012-02-01

344

Diatom response to extremely low-frequency magnetic fields  

SciTech Connect

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

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

1992-06-01

345

Genome engineering empowers the diatom Phaeodactylum tricornutum for biotechnology.  

PubMed

Diatoms, a major group of photosynthetic microalgae, have a high biotechnological potential that has not been fully exploited because of the paucity of available genetic tools. Here we demonstrate targeted and stable modifications of the genome of the marine diatom Phaeodactylum tricornutum, using both meganucleases and TALE nucleases. When nuclease-encoding constructs are co-transformed with a selectable marker, high frequencies of genome modifications are readily attained with 56 and 27% of the colonies exhibiting targeted mutagenesis or targeted gene insertion, respectively. The generation of an enhanced lipid-producing strain (45-fold increase in triacylglycerol accumulation) through the disruption of the UDP-glucose pyrophosphorylase gene exemplifies the power of genome engineering to harness diatoms for biofuel production. PMID:24871200

Daboussi, Fayza; Leduc, Sophie; Maréchal, Alan; Dubois, Gwendoline; Guyot, Valérie; Perez-Michaut, Christophe; Amato, Alberto; Falciatore, Angela; Juillerat, Alexandre; Beurdeley, Marine; Voytas, Daniel F; Cavarec, Laurent; Duchateau, Philippe

2014-01-01

346

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

Microsoft Academic Search

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

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

1995-01-01

347

Dynamics of diatom colonization process in some rivers influenced by urban pollution (Hanoi, Vietnam)  

Microsoft Academic Search

Periphytic diatom communities’ colonization patterns were studied at three sampling stations of the Red–Nhue–Tolich hydrosystem presenting different urban pollution levels by using artificial substrates for 6 weeks in dry season 2005. Structural characteristics of periphytic diatoms developed on glass substrates at each sampling site were followed and compared. This experiment showed, through various general criteria (total diatom density, dry weight

Thi Thuy Duong; Agnès Feurtet-Mazel; Michel Coste; Dinh Kim Dang; Alain Boudou

2007-01-01

348

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

Microsoft Academic Search

Diatoms are an important group of eukaryotic phytoplankton, responsible for about 20% of global primary productivity. Study of the functional role of chemical signaling within phytoplankton assemblages is still in its infancy although recent reports in diatoms suggest the existence of chemical-based defense strategies. Here, we demonstrate how the accurate perception of diatom-derived reactive aldehydes can determine cell fate in

Assaf Vardi; Fabio Formiggini; Raffaella Casotti; Alessandra De Martino; François Ribalet; Antonio Miralto; Chris Bowler

2006-01-01

349

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

Microsoft Academic Search

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

Peter C. Vos; Hein Wolf

1993-01-01

350

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

PubMed

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

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

2014-02-21

351

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

352

Effects of light fluctuations on the growth and productivity of Antarctic diatoms in culture  

Microsoft Academic Search

This work shows that the low division rates observed in diatoms in Antarctic waters seem to be due to conditions of irradiance rather than to the low temperature: low light intensity and light fluctuations are two factors which depress the division rate of diatoms. However, with regard to the productivity, Antarctic diatoms seem well-adapted to their turbulent environment. Cells grown

Anne Mortain-Bertrand; M. Curie

1989-01-01

353

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

Microsoft Academic Search

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.

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

2011-01-01

354

Deficiencies in the diatom evidence for a Pliocene reduction of the East Antarctic Ice Sheet  

Microsoft Academic Search

Evidence for Pliocene reduction of the East Antarctic Ice Sheet (EAIS) has been inferred from the presence of Pliocene planktic marine diatoms in tills of the Sirius Group now exposed along the slopes of the Transantarctic Mountains. We highlight deficiencies in this diatom evidence for a Pliocene reduction of the EAIS. First, we examine what diatom habitats are left behind

Lloyd H. Burckle; Arjen P. Stroeven; Christian Bronge; Urve Miller; Anders Wasell

1996-01-01

355

Perforation of flexible laminates by projectiles of different geometry  

Microsoft Academic Search

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

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

2005-01-01

356

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 87±1%. With colloidal silver treatment

Sumin Kim; Hyun-Joong Kim

2006-01-01

357

Fracture behavior of thick, laminated graphite/epoxy composites  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

358

Non-linear behavior of fiber composite laminates  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

359

Interlaminar Fracture of Commingled GF\\/PET Composite Laminates  

Microsoft Academic Search

The Mode I, Mode II and mixed mode (Mode I:II ratios of 4:1, 1:1 and 1:4) fracture behavior of novel textile glass fiber reinforced polyethylene terephthalate (GF\\/PET) laminates has been investigated. The laminates were manufactured by compression molding two different fabrics produced by weaving and warp knitting commingled GF\\/PET yarns. The initiation fracture toughness of the woven laminates in pure

Niklas Svensson; Roshan Shishoo; Michael Gilchrist

1998-01-01

360

Role of diatoms in nickel biogeochemistry in the ocean  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

361

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

362

The Displacement Perspective During Ultimate Failure of Composite Laminates  

NASA Astrophysics Data System (ADS)

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

Pal, P.; Bhar, A.

2013-04-01

363

An Elastic Model of Blebbing in Nuclear Lamin Meshworks  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

364

Mechanical model of blebbing in nuclear lamin meshworks  

PubMed Central

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

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

2013-01-01

365

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

PubMed

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

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

2012-10-01

366

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

367

Method of insetting predesigned disbond areas into composite laminates  

NASA Technical Reports Server (NTRS)

This invention is a process for producing composite laminates containing interlaminar disbonds of controlled sizes, shapes, and positions within a composite structure. A composite layer is provided for later inclusion within a laminate. The surfaces of this composite layer are solvent cleaned and sandblasted, except in desired disbond areas, which are coated with a releasing surface. A template to mask the bond areas is employed to obtain disbond areas of controlled shapes and sizes. The resulting composite layer is then used in the subsequent manufacture of a laminate, whereby faulty adhesion in the laminate can be studied with prior knowledge of the size, shape, and location of the disbond areas.

Dickerson, George E. (inventor)

1990-01-01

368

Microwave permeability of laminates with thin Fe-based films  

NASA Astrophysics Data System (ADS)

The permeability of layered composites (laminates) is measured at frequencies 0.1-10 GHz. The laminates consist of alternating iron and Mylar films. The continuous or patterned iron films 0.1-1 ?m thick are produced by magnetron sputtering. The intrinsic permeability spectra of metal inclusion are parametrically reconstructed. The obtained parameters of magnetic resonance are compared to the theoretical constrains derived for a perfect infinite film. The effect of film thickness upon the permeability of the laminate is discussed. The microwave permeability of the laminates under study is comparable with that of composites filled with carbonyl iron.

Iakubov, I. T.; Lagarkov, A. N.; Maklakov, S. A.; Osipov, A. V.; Rozanov, K. N.; Ryzhikov, I. A.; Starostenko, S. N.

2004-05-01

369

A Reliability Analysis Approach to Fatigue Life Dispersion of Laminated Glass Fiber Composite Materials.  

National Technical Information Service (NTIS)

The statistical nature of the fatigue life of laminated glass fiber composite materials (FRP) is studied. Four different FRP laminates (satin woven FRP, plain woven FRP, roving woven FRP, and SMC laminated FRP) were used in the experiments. Unidirectional...

T. Tanimoto S. Amijima H. Ishikawa K. J. Miller R. F. Smith

1979-01-01

370

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...after importation of certain prepregs, laminates, and finished circuit boards that infringe...Co., Ltd., and VENTEC-Global Laminates USA LLC based on a consent order....

2012-10-05

371

Effects of monomethylhydrazine on selected species of marine diatoms  

SciTech Connect

A safe concentration (SC) and the mean effective concentration (EC) for hydrazine, MMH, and unsymmetrical dimethylhydrazine have been determined on species of green algae. The aqueous degradation of MMH is relatively rapid compared to the time green algae require to reach maximum standing crop. The diatoms Thalassiosira pseudonana and Skeletonema costatum reach maximum standing crop in 6 to 7 days in culture which makes them ideal for testing short-term effects of MMH. The objectives of this study were to determine the relative sensitivity of selected marine diatoms to MMH and whether species composition would be affected by MMH.

Wendler, B.W.; Norris, D.R.

1985-07-01

372

Distribution of Epiphytic Diatoms in a Sub-Tropical Estuary  

NASA Astrophysics Data System (ADS)

Within estuaries, seagrasses may represent an order of magnitude greater surface area relative to sediments for the colonization and growth of diatoms. Fossil diatom distributions have proven useful in inferring paleoenvironmental conditions. The strength of these inferences is dependent upon defining the environmental relationships of contempory diatom compositions. The present investigation characterized the modern epiphytic diatom flora on the seagrass Thalassia testudinum at seven sites in the sub-tropical Florida Bay estuary and at one Atlantic Ocean site east of the upper Florida Keys. These sites were sampled six times between March 2000 and April 2001. Diatom species composition was related to water quality parameters using multivariate statistics. 338 diatom species were identified. The seven most abundant species from pooled samples were Cocconeis placentula, Brachysira aponina, Nitzschia liebetruthii, Hyalosynedra laevigata, Amphora cf. tenerrima, Mastogloia crucicula, and M. pusilla. These seven species collectively accounted for 51.7 percent of all valves counted and occurred in at least 85 percent of all samples. Analysis of similiarity and NMDS ordination of species relative abundances revealed four distinct diatom communities across the study region. The spatial variability of these communities was correlated with salinity and water-column nutrient availability. Summertime communities were significantly different from winter-spring communities, but these communities showed a gradual temporal progression with much overlap. The temporal variability was correlated with temperature. Indicator species analysis identified many species significantly influencing the four spatial groups. The Atlantic marine site was characterized by many different Mastogloia species and some epipsammic (sand-grain associated) diatoms (i.e., Cymatosira lorenziana, Dimerogramma dubium, and Neofragilaria nicobarica). Mastogloia pusilla, Rhopalodia pacifica, and Cocconeis woodii were strong indicators of the Gulf of Mexico marine site. Reimerothrix floridensis was particularly abundant in the western interior of Florida Bay (i.e., sites 2, 3, and 4) during summer months. The eastern interior of Florida Bay was characterized by high relative abundances of Brachysira aponina and Nitzschia liebetruthii. The optima and tolerance of these indicator species relative to individual water quality parameters were also determined.

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

2005-05-01

373

Relaxation of higher vibrational states in diatomic gases  

NASA Technical Reports Server (NTRS)

A general and computationally efficient approach evaluating the transition probabilities for the V-T exchange, involving highly excited levels and the transitions of delta-v of more than 1, in diatomic gases is presented. The role of the repulsive part of the intermolecular potential on the transition probability is also investigated. Examples of numerical results are given for number of transitions in nitrogen and oxygen molecules in the ground electronic states. The approach can be used for interactions involving diatomic molecular ions.

Kunc, J. A.

1992-01-01

374

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

375

Sediment sources and sedimentation processes of 2011 Tohoku-oki tsunami deposits on the Sendai Plain, Japan — Insights from diatoms, nannoliths and grain size distribution  

NASA Astrophysics Data System (ADS)

The 11th March 2011 Tohoku-oki tsunami inundated the low-lying Sendai Plain (Japan) more than 5 km inland leaving sand and mud deposits over most of the area. In order to establish the sources of the tsunami deposits and interpret processes of their sedimentation, samples were collected from the deposits, underlying soils and the beach along a shore-perpendicular transect and analysed for grain size, diatom assemblages and nannoliths. The fining-inland tsunami deposits consisted of poorly to moderately sorted medium to coarse sand within 2 km of the coastline and very poorly to poorly sorted mud farther inland. More specifically, there was a slight fining of the coarse to medium sand mode within the sandy deposits and an increased contribution of the coarse and very coarse silt fraction in the mud deposits. The tsunami deposits also exhibited vertical changes including fining upward and coupled coarsening-fining upward trends. Few diatoms were present in beach sediments, soils and tsunami deposits within 1 km of the coastline, while diatoms were more abundant farther inland. Diatom assemblages in the soil and tsunami deposits were similar and dominated by species typical of freshwater-brackish habitats, while no typically marine species were encountered. Nannoliths were generally absent in the studied sediments, except for few specimens. Our data indicate that there was probably no or only a very minor component of marine sediments transported onland by the tsunami. The sandy tsunami deposits within ~ 1 km of the coastline were mostly derived from beach and dune erosion. From 1 to 2 km landward the contribution of these sources decreased, while sources comprising local soil erosion and the entrainment of sediments from the Teizan-bori canal increased. Farther inland, local soil erosion was the major sediment source for the mud deposits. The tsunami deposits were most likely deposited during at least two inundations, mostly out from suspension resulting in an upward grain size fining trend. However, bed load deposition was also important in the sandy deposits as suggested by a common grain size upward coarsening, position on C-M diagrams and frequent horizontal lamination. The present study reveals that even very large tsunamis may not transport marine sediments onland and thus many commonly applied indicators of tsunami deposits based on the assumption of their offshore origin (marine diatoms, foraminifera, nannoliths, marine sediments) may be of limited use.

Szczuci?ski, Witold; Kokoci?ski, Miko?aj; Rzeszewski, Micha?; Chagué-Goff, Catherine; Cachão, Mario; Goto, Kazuhisa; Sugawara, Daisuke

2012-12-01

376

Three-year changes in planktonic diatom communities in a eutrophic lake in Nanjing, Jiangsu Province, China  

Microsoft Academic Search

We determined the patterns in the annual succession of planktonic diatoms and the relationship between diatom seasonal succession and environmental variables in shallow, nutrient-rich Lake Yueya, which lies in Nanjing, Jiangsu Province, China. Planktonic diatoms and selected environmental parameter were examined monthly over 3 years. The diatom assemblages exhibited obvious seasonal succession in this lake. Cyclostephanos dubius and Stephanodiscus hantzschii

Min Yao; Yan-Ling Li; Xiang-Dong Yang; Qian Liu

2011-01-01

377

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

PubMed

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

Yu, Chang-feng

2012-08-01

378

Supramolecular organization of fucoxanthin-chlorophyll proteins in centric and pennate diatoms.  

PubMed

Fucoxanthin-chlorophyll proteins (FCP) are the major light-harvesting proteins of diatom algae, a major contributor to marine carbon fixation. FCP complexes from representatives of centric (Cyclotella meneghiniana) and pennate (Phaeodactylum tricornutum) diatoms were prepared by sucrose gradient centrifugation and studied by means of electron microscopy followed by single particle analysis. The oligomeric FCP from a centric diatom were observed to take the form of unusual chain-like or circular shapes, a very unique supramolecular assembly for such antennas. The existence of the often disputed oligomeric form of FCP in pennate diatoms has been confirmed. Contrary to the centric diatom FCP, pennate diatom FCP oligomers are very similar to oligomeric antennas from related heterokont (Stramenopila) algae. Evolutionary aspects of the presence of novel light-harvesting protein arrangement in centric diatoms are discussed. PMID:24715699

Gardian, Zdenko; Litvín, Radek; Bína, David; Vácha, František

2014-07-01

379

Diatom Data from Bradley Lake, Oregon: Downcore Analyses.  

National Technical Information Service (NTIS)

Displaced marine diatoms provide biostratigraphic evidence for tsunami inundation at Bradley Lake, a small freshwater lake on the south-central Oregon coast. During the past 7,200 years, fine-grained lacustrine deposits in the deep axis of the lake were d...

E. Hemphill-Haley R. C. Lewis

2003-01-01

380

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

381

The paleoclimatology of Lake Baikal: A diatom synthesis and prospectus  

Microsoft Academic Search

The paleoclimatic archive held in Lake Baikal sediments is of significant importance, given the lake's position in one of the world's most continental regions where there are few continuous, high quality records spanning the Quaternary. Here I review diatom and associated biogenic silica records from Lake Baikal sediments and provide a paleoclimatic synthesis of changes at various timescales over the

Anson W. Mackay

2007-01-01

382

Fecal Pellets: Role in Sedimentation of Pelagic Diatoms  

Microsoft Academic Search

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

Hans-Joachim Schrader

1971-01-01

383

CHECKLIST OF DIATOMS FROM THE LAURENTIAN GREAT LAKES  

EPA Science Inventory

An updated diatom (Bacillariophyta) checklist for the Great Lakes has been completed (J. Great Lakes Res. 1999) and supplants the preliminary checklist (J. Great Lakes Res. 1978). The present list is effectively a 20-year update. The updated list is based upon: 1) the 1978 checkl...

384

Calculation of Franck-Condon Factors for Diatomic Molecules.  

National Technical Information Service (NTIS)

This report calculates Franck-Condon Factors for several diatomic molecules (Br2, BrCl, BrF, IC1, IF, PbO). The potential energy wells for the different electronic states of the molecules were modelled using a Rydberg-Klein-Rees approximation. The results...

L. D. Brasure

1985-01-01

385

NEW DIATOM SPECIES FROM THE FEDERAL DISTRICT OF BRAZIL  

Microsoft Academic Search

As the final part of a taxonomic and ecological study of the diatoms living in two beds of aquatic macrophytes in Lagoa Bonita, Federal District of Brazil, four new species, Brachysira staurophora, Eunotia sennae, Kobayasiella mirabilis and Pinnularia sulcata are described. They occurred in several of the numerous samples examined for this study. For each taxon, morphological and ecological data

Maria das Graças Machado de Souza; Pierre Compère

1999-01-01

386

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...

387

Exotic states of diatomic molecules and methods of their description  

Microsoft Academic Search

Various methods for representation of electronic states in diatomic molecules basing on experimental spectroscopic data are critically compared. The technique of pointwise inverted perturbation approach (IPA) is indicated as the most suitable in case of states characterized by potential energy curves substantially different from the Morse potential. Recent developments of this technique are presented. Our understanding of the energy structure

ASEN PASHOV; James Bourchier

388

State-Specific Energy Transfer in Diatomic Radicals.  

National Technical Information Service (NTIS)

Quantum-state-specific collisional energy transfer has been studied in the N atoms, and the Hydroxyl and Nitrogen Sulfur diatomic radicals. Vibrational energy transfer (VET) in the A(2) Sigma(+) state of OH was found to depend on rotational level. Rotatio...

D. R. Crosley J. B. Jeffries R. A. Copeland

1988-01-01

389

Experimental Vibrational Zero-Point Energies: Diatomic Molecules  

Microsoft Academic Search

Vibrational zero-point energies (ZPEs), as determined from published spectroscopic constants, are derived for 85 diatomic molecules. Standard uncertainties are also provided, including estimated contributions from bias as well as the statistical uncertainties propagated from those reported in the spectroscopy literature. This compilation will be helpful for validating theoretical procedures for predicting ZPEs, which is a necessary step in the ab

Karl K. Irikura

2007-01-01

390

Freshwater diatoms as a source of lipids for biofuels.  

PubMed

Until recently, biodiesel production has been derived from terrestrial plants such as soybean and canola, leading to competition between biodiesel production and agricultural production for source materials. Microalgae have the potential to synthesize 30 times more oil per hectare than terrestrial plants without competing for agricultural land. We examined four genera (Cyclotella, Aulacoseira, Fragilaria, Synedra) of common freshwater diatoms (Bacillariophyceae) for growth and lipid content in defined medium (sD11) that replicates hypereutrophic conditions in lakes and wastewater treatment plant effluents and optimized the medium for silicon content. Cyclotella and Aulacoseira produced the highest levels of total lipids, 60 and 43 ?g total lipids/ml, respectively. Both diatoms are rich in fatty acids C14, C16, C16:1, C16:2,7,10, and C22:5n3. Of the diatoms examined, Cyclotella reached the highest population density (>2.5 × 10(6) cells/ml) in stationary phase when many of the cells appeared to be filled entirely with oil. Silicon enrichment studies indicated that for optimal utilization of phosphorus and nitrogen by diatoms growing in wastewater effluent, the amount of silicon present or added to the effluent should be 17.5 times the mass of phosphorus in the effluent. With high growth rates, high lipid contents, and rapid settling rates, Cyclotella and Aulacoseira are candidates for biodiesel production. PMID:22009056

Graham, James M; Graham, Linda E; Zulkifly, Shahrizim B; Pfleger, Brian F; Hoover, Spencer W; Yoshitani, Jun

2012-03-01

391

Diatomic Cesium in a Diode-Pumped Alkali Laser System  

Microsoft Academic Search

Abstract Diode Pumped Alkali Laser (DPAL) systems combine the positive characteristics of chemical and diode lasers. These systems create a laser that is compact and ecient, while working well at high temperatures and high powers. In conjunction with the Air Force Research Laboratory (AFRL), an attempt was made to improve DPAL technology by using a diatomic alkali metal as a

Jamey Christy; Eric Martinez; Tanner Oakes; Jake Smith; Kendrick Walter

2008-01-01

392

Damping mechanisms in fiber reinforced laminates  

NASA Technical Reports Server (NTRS)

Low strain damping in fiber reinforced composite materials is due to material loss factors in both fibers and matrix materials. The high modulus of the fibers makes up for the low damping factor. Strains high enough to cause transverse layer cracking in laminates with organic matrix materials causes a large permanent increase in the damping factor. This increase is not due to the transverse cracks but rather to short microcracks in the high shear strain regions. Other damping mechanisms at high strains are also discussed.

Plunkett, R.

1983-01-01

393

Laminated composites modeling in ADAGIO/PRESTO.  

SciTech Connect

A linear elastic constitutive equation for modeling fiber-reinforced laminated composites via shell elements is specified. The effects of transverse shear are included using first-order shear deformation theory. The proposed model is written in a rate form for numerical evaluation in the Sandia quasi-statics code ADAGIO and explicit dynamics code PRESTO. The equation for the critical time step needed for explicit dynamics is listed assuming that a flat bilinear Mindlin shell element is used in the finite element representation. Details of the finite element implementation and usage are given. Finally, some of the verification examples that have been included in the ADAGIO regression test suite are presented.

Hammerand, Daniel Carl

2004-05-01

394

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

395

Nonlinear sequential laminates reproducing hollow sphere assemblages  

NASA Astrophysics Data System (ADS)

A special class of nonlinear porous materials with isotropic 'sequentially laminated' microstructures is found to reproduce exactly the hydrostatic behavior of 'hollow sphere assemblages'. It is then argued that this result supports the conjecture that Gurson's approximate criterion for plastic porous materials, and its viscoplastic extension of Leblond et al. (1994), may actually yield rigorous upper bounds for the hydrostatic flow stress of porous materials containing an isotropic, but otherwise arbitrary, distribution of porosity. To cite this article: M.I. Idiart, C. R. Mecanique 335 (2007).

Idiart, Martín I.

2007-07-01

396

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

397

Differential Curing In Fiber/Resin Laminates  

NASA Technical Reports Server (NTRS)

Modified layup schedule counteracts tendency toward delamination. Improved manufacturing process resembles conventional process, except prepregs partially cured laid on mold in sequence in degree of partial cure decreases from mold side to bag side. Degree of partial cure of each layer at time of layup selected by controlling storage and partial-curing temperatures of prepreg according to Arrhenius equation for rate of gel of resin as function of temperature and time from moment of mixing. Differential advancement of cure in layers made large enough to offset effect of advance bag-side heating in oven or autoclave. Technique helps prevent entrapment of volatile materials during manufacturing of fiber/resin laminates.

Webster, Charles N.

1989-01-01

398

Better Thermal Insulation in Solar-Array Laminators  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

399

Lamins: building blocks or regulators of gene expression?  

Microsoft Academic Search

Intermediate filament (IF) proteins are the building blocks of cytoskeletal filaments, the main function of which is to maintain cell shape and integrity. The lamins are thought to be the evolutionary progenitors of IF proteins and they have profound influences on both nuclear structure and function. These influences require the lamins to have dynamic properties and dual identities — as

Christopher J. Hutchison

2002-01-01

400

Charge distribution in polyethylene\\/ethylene vinylacetate laminates and blends  

Microsoft Academic Search

The formation of space charge in polyethylene\\/ethylene vinylacetate copolymer (PE\\/EVA) laminates was investigated using a pulsed electroacoustic (PEA) method. The formation of heterocharge was observed in PE while positive charge (holes) was distributed over the EVA specimen. In the laminates, however, a large amount of charge accumulates at the interface between PE and EVA, resulting in an increase of the

Kwang S. Suh; Jae Young Kim; Chang Ryong Lee; Tatsuo Takada

1996-01-01

401

A-type nuclear lamins, progerias and other degenerative disorders  

Microsoft Academic Search

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

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

2005-01-01

402

High Toughness Ceramic Laminates by Design of Residual Stresses  

Microsoft Academic Search

Multilayered ceramic composites are very promising materials for different engineering applications. Laminates with strong interfaces can provide high apparent fracture toughness and damage tolerance along with the high strength and reliability. The control over the mechanical behavior of laminates can be obtained through design of residual stresses in separate layers. Here we report a development of tough silicon nitride based

Nina A. Orlovskaya; Jakob Kuebler; Vladimir I. Subotin; Mykola Lugovy

403

Evaluation of laminated composite structures using ultrasonic attenuation measurement  

Microsoft Academic Search

The existence of delamination and porosity in laminated composite structures will degrade the strength of the structures. The detection of delamination can be easily obtained using ultrasonic C-scan or A-scan methods. But, the detection of porosity in laminated structures has been a difficult task for years, especially in production condition. This paper will analytically evaluate the current techniques used in

Peitao Shen; J. R. Houghton

1992-01-01

404

Oxydative stress alters nuclear shape through lamins dysregulation  

PubMed Central

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

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

2012-01-01

405

Identification of differential protein interactors of lamin A and progerin.  

PubMed

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

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

2010-01-01

406

Prediction of Stress Relaxation in Laminated Leather Layers  

Microsoft Academic Search

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

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

407

Live load distribution factors for glued-laminated timber bridges  

Microsoft Academic Search

Over the past years the United States Department of Agriculture - Forest Products Laboratory and the Federal Highway Administration have supported several research programs. This thesis is a result of a study sponsored by the Forest Products Laboratory, with the objective of determining how truckloads are distributed to the structural members of glued-laminated timber bridges. Glued-laminated timber girder bridges with

Jeremy James May

2008-01-01

408

An Historic Overview of the Development of Fibre Metal Laminates  

Microsoft Academic Search

In this paper a brief overview of the history of Fibre Metal Laminates Arall and Glare is given as background information for the other, technical articles in this journal. The story of the development of Fibre Metal Laminates is rather a unique story in the history of aircraft materials: A university laboratory invented, developed and certified an aircraft material. Many

C. A. J. R. Vermeeren

2003-01-01

409

Failure mechanism of riveted joint in fibre metal laminates  

Microsoft Academic Search

The paper reports on an investigation involving a comparison between a fibre metal laminate (FML) and typical aluminium alloy fuselage material (2024-T3). Results are presented on the effect of panel material, laminate stacking stiffness and forming load on the stress distribution within both the FML and the 2024-T3 riveted joints subjected to external loads. The stress distribution was predicted using

Liam Ryan; John Monaghan

2000-01-01

410

Static Strength of Riveted Joints in Fibre Metal Laminates.  

National Technical Information Service (NTIS)

The behavior of rivets in aircraft and other structures made of Fiber Metal Laminates (FML) is of concern because the superior properties of these materials enable reduced thicknesses to be used, and because of the nature of the laminate itself. The prese...

W. J. Slagter

1994-01-01

411

Numerical assessment of delamination in fibre metal laminates  

Microsoft Academic Search

In the present contribution numerical models for delamination in fibre metal laminates are discussed. Fibre metal laminates form a class of materials in which homogeneous aluminium sheets are combined with fibre reinforced prepreg layers. Intensive experimental analyses have been carried out to assess the possible application of new design methods which make use of the layered structure of fibre metal

Frank Hashagen; René de Borst

2000-01-01

412

Fatigue crack initiation in fibre-metal laminate glare 2  

Microsoft Academic Search

Fatigue crack initiation in notched plates made of fibre-metal laminate GLARE 2 was studied under constant stress amplitude loading using light and scanning electron microscope. Fatigue crack initiation mechanism observed in notched laminates was found different from the mechanism typical for monolithic materials. Stress and plastic strain finite element calculation was used to discuss the anomalous fatigue crack initiation in

A. Vašek; J. Polák; V. Kozák

1997-01-01

413

Numerical assessment of failure mechanisms in fibre metal laminates  

Microsoft Academic Search

In this contribution numerical models are discussed for describing failure mechanisms in fibre metal laminates. Fibre metal laminates form a new class of materials which are considered for a possible application to the fuselage of future aircraft generations. The intensive experimental analyses of these materials are focused on the assessment of their residual strength and on the assessment of new

F. Hashagen; R. De Borst

1998-01-01

414

Characterisation of fibre metal laminates under thermomechanical loadings  

Microsoft Academic Search

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

M. Hagenbeek

2005-01-01

415

Towards application of fibre metal laminates in large aircraft  

Microsoft Academic Search

Fibre metal laminates were developed at Delft University during the last two decades as a family of new hybrid materials consisting of bonded thin metal sheets and fibre\\/adhesive layers. This laminated structure provides the material with excellent fatigue, impact and damage tolerance characteristics and a low density. While the 20 per cent weight reduction was the prime driver behind the

A. Vlot; L. B. Vogelesang; T. J. de Vries

1999-01-01

416

Mechanical and electrical properties of laminated polytetrafluoroethylene films  

Microsoft Academic Search

Laminated polytetrafluoroethylene (PTFE) films, which are made of compact and porous PTFE layers, are prepared through the process of sintering. The corona charging technique is utilized to make the laminated PTFE films piezoelectric, thus transforming them into piezoelectrets. The crystallinity, Young’s modulus in compression mode, stress-strain behavior, charge dynamics, and thermal stability of the fabricated films are investigated by particular

Xuewen Wang; Kexing Lou; Xiaoqing Zhang; Zhuanlan Sun; Gongxun Cao; Zhongfu Xia

2011-01-01

417

Permutation genetic algorithm for stacking sequence design of composite laminates  

Microsoft Academic Search

Stacking sequence design of a composite laminate with a given set of plies is a combinatorial problem of seeking an optimal permutation. Permutation genetic algorithms optimizing the stacking sequence of a composite laminate for maximum buckling load are studied. A new permutation GA named gene–rank GA is developed and compared with an existing Partially Mapped Permutation GA, originally developed for

Boyang Liu; Raphael T. Haftka; Mehmet A. Akgün; Akira Todoroki

2000-01-01

418

Improved genetic algorithm for minimum thickness composite laminate design  

Microsoft Academic Search

The use of a genetic algorithm for the minimum thickness design of composite laminated plates is explored. A previously developed genetic algorithm for laminate design is thoroughly revised and improved, by incorporating knowledge of the physics of the problem into the genetic algorithm. Constraints are accounted for by combining fixed and progressive penalty functions. Improved selection, mutation, and permutation operators

R. Le Riche; R. T. Haftka

1995-01-01

419

Delamination threshold loads for low velocity impact on composite laminates  

Microsoft Academic Search

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

G. A. Schoeppner; S. Abrate

2000-01-01

420

Some Tensile Properties of Metal-Metallic Glass Laminates.  

National Technical Information Service (NTIS)

The tensile properties of brass (Cu-30% Zn)-nickel base metallic glass (MBF-35 Metglas) laminates have been investigated. Laminates were prepared by soldering these constituents together with a Pb-Sn alloy. The metallic glass exhibited an enhanced tensile...

Y. Leng T. H. Courtney

1989-01-01

421

Ultrasonic imaging of damages in CRFT-laminates  

Microsoft Academic Search

High performance materials such as carbon fiber reinforced plastics (CFRP) are attractive materials for aircraft and aerospace components. Their application to primary aircraft structures requires the knowledge of damage incured after fabrication or in service. CFRP laminates are inhomogeneous and anisotropic materials, a 2 mm laminate consists of 16 layers of fibers, each with a thickness of 0.125 mm. The

Wolfgang Hillger

1992-01-01

422

Residual strength of centrally cracked metal\\/fiber composite laminates  

Microsoft Academic Search

The residual strength of metal\\/fiber composite laminates (MFCLs) with a central crack is studied. The laminate is a sandwich with a fiber reinforced epoxy ply (prepreg) in the middle and an aluminum alloy layer on each of the outer surfaces. Dugdale strip yielding zones in the aluminum layers at the crack tip are assumed to take into account ductile deformations

Z.-H. Jin; R. C. Batra

1996-01-01

423

Fatigue damage accumulation in carbon\\/epoxy laminated composites  

Microsoft Academic Search

The precise prediction of fatigue damage progress and fatigue life in laminated composites has been always a concern to designers. The present work is focused on the fatigue damage mechanisms and damage accumulation rate in laminated composites. Results showed that the dominant damage mechanism depends on the applied stress and total delamination only observed under the cyclic stress of less

J. Aghazadeh Mohandesi; B. Majidi

2009-01-01

424

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

425

A MEMS lamination technology based on sequential multilayer electrodeposition  

NASA Astrophysics Data System (ADS)

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

Kim, Minsoo; Kim, Jooncheol; Herrault, Florian; Schafer, Richard; Allen, Mark G.

2013-09-01

426

Genome Properties of the Diatom Phaeodactylum tricornutum[w  

PubMed Central

Diatoms are a ubiquitous class of microalgae of extreme importance for global primary productivity and for the biogeochemical cycling of minerals such as silica. However, very little is known about diatom cell biology or about their genome structure. For diatom researchers to take advantage of genomics and post-genomics technologies, it is necessary to establish a model diatom species. Phaeodactylum tricornutum is an obvious candidate because of its ease of culture and because it can be genetically transformed. Therefore, we have examined its genome composition by the generation of approximately 1,000 expressed sequence tags. Although more than 60% of the sequences could not be unequivocally identified by similarity to sequences in the databases, approximately 20% had high similarity with a range of genes defined functionally at the protein level. It is interesting that many of these sequences are more similar to animal rather than plant counterparts. Base composition at each codon position and GC content of the genome were compared with Arabidopsis, maize (Zea mays), and Chlamydomonas reinhardtii. It was found that distribution of GC within the coding sequences is as homogeneous in P. tricornutum as in Arabidopsis, but with a slightly higher GC content. Furthermore, we present evidence that the P. tricornutum genome is likely to be small (less than 20 Mb). Therefore, this combined information supports the development of this species as a model system for molecular-based studies of diatom biology. The nucleotide sequence data reported has been deposited in GenBank Nucleotide Sequence Database (dbEST section) under accession nos. BI306757 through BI307753.

Scala, Simona; Carels, Nicolas; Falciatore, Angela; Chiusano, Maria Luisa; Bowler, Chris

2002-01-01

427

Fatigue behavior of graphite-epoxy laminates at elevated temperatures  

NASA Technical Reports Server (NTRS)

An examination and analysis is presented of the elevated temperature fatigue behavior of multidirectional graphite-epoxy laminates in terms of single lamina behavior. The laminate strength is predicted by considering the cyclic stress field in each lamina, the interlaminar stresses, and the experimentally determined temperature-effect 'shifting factors'. The initial failure of a lamina in a laminate is examined first in terms of stress redistribution, and then in terms of total failure and final laminate fracture; these analytical results are then compared with the actual fatigue behavior of T300/5208 graphite-epoxy composite laminates. In view of the agreement obtained, it is concluded that the temperature 'shifting factors' introduced here enable one to predict long-term behavior at a given temperature from short-time testing at elevated temperatures.

Rotem, A.; Nelson, H. G.

1981-01-01

428

The strength of laminated composite materials under repeated impact loading  

NASA Technical Reports Server (NTRS)

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

Rotem, Assa

1988-01-01

429

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

430

The mechanical behavior of GLARE laminates for aircraft structures  

NASA Astrophysics Data System (ADS)

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

Wu, Guocai; Yang, J.-M.

2005-01-01

431

LINCing lamin B2 to neuronal migration: growing evidence for cell-specific roles of B-type lamins.  

PubMed

Nuclear lamins are major components of the nuclear lamina, and play essential roles in supporting the nucleus and organizing nuclear structures. While a large number of clinically important mutations have been mapped to the LMNA gene in humans, very few mutations have been associated with the B-type lamins. We have shown that lamin B2-deficiency in mice results in severe brain abnormalities. While the early stages of forebrain development in lamin B2-deficient mice appear to be normal, cortical neurons fail to migrate and organize into proper layers within the cerebral cortex. The morphogenesis of the hippocampus and cerebellum is also severely impaired. These phenotypes are reminiscent of lissencephaly, a human brain developmental disorder characterized by an abnormal neuronal migration. Most mutations in lissencephaly patients affect cytoplasmic regulators of nuclear translocation, which is a crucial step in neuronal migration. The phenotypes of lamin B2-deficient mice suggest that lamin B2 may also play a key role in nuclear translocation. Potential mechanisms for lamin B2 involvement, which include mechanical and non-mechanical roles, and participation in LINC complexes in the nuclear envelope, are discussed along with evidence that lamins B1 and B2 play distinct, cell-specific functions. PMID:21278813

Coffinier, Catherine; Fong, Loren G; Young, Stephen G

2010-01-01

432

Mechanical behavior of thick, curved, laminated composites  

SciTech Connect

A finite element code was developed for calculating the stresses and strains in thick, curved, composite laminates subjected to an arbitrary, but consistent, combination of forces and displacements. The laminate may be arbitrarily curved in one plane but must have no curvature in the other two perpendicular planes. The accuracy of the stress analysis was evaluated by generating numerical results for three problems for which analytical solutions exist, and by comparing the numerical and the analytical results. In every case the agreement between the numerical and analytical results was excellent. The analysis and the computer code were specialized to racetrack shaped composite straps loaded by pins in tension. A procedure was also established for estimating the failure loads of such straps, by utilizing the strains provided by the finite element method and the Tsai-Wu failure criteria. Tests were performed to validate the strap stress analysis and failure model. Forty-three straps were made of either T300/976, IM6/081, T1000/081 graphite-epoxy, K92/081 kevlar-epoxy, or S-2/081 glass epoxy. The strains and failure loads of these straps were measured, and the data were compared to the calculated strains and failure loads. The calculated values agreed well with the data. Lastly, the use of the computer code in the design of composite straps is discussed, and charts for estimating the failure loads of different types of straps are presented.

Graff, E.

1989-01-01

433

Development of a heterogeneous laminating resin system  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

434

Concentration-dependent lamin assembly and its roles in the localization of other nuclear proteins  

PubMed Central

The nuclear lamina (NL) consists of lamin polymers and proteins that bind to the polymers. Disruption of NL proteins such as lamin and emerin leads to developmental defects and human diseases. However, the expression of multiple lamins, including lamin-A/C, lamin-B1, and lamin-B2, in mammals has made it difficult to study the assembly and function of the NL. Consequently, it has been unclear whether different lamins depend on one another for proper NL assembly and which NL functions are shared by all lamins or are specific to one lamin. Using mouse cells deleted of all or different combinations of lamins, we demonstrate that the assembly of each lamin into the NL depends primarily on the lamin concentration present in the nucleus. When expressed at sufficiently high levels, each lamin alone can assemble into an evenly organized NL, which is in turn sufficient to ensure the even distribution of the nuclear pore complexes. By contrast, only lamin-A can ensure the localization of emerin within the NL. Thus, when investigating the role of the NL in development and disease, it is critical to determine the protein levels of relevant lamins and the intricate shared or specific lamin functions in the tissue of interest.

Guo, Yuxuan; Kim, Youngjo; Shimi, Takeshi; Goldman, Robert D.; Zheng, Yixian

2014-01-01

435

Investigation of Forming Performance of Laminated Steel Sheets Using Finite Element Analyses  

Microsoft Academic Search

Laminated steel sheets have been used in automotive structures for reducing in-cabin noise. However, due to the marked difference in material properties of the different laminated layers, integrating laminated steel parts into the manufacturing processes can be challenging. Especially, the behavior of laminated sheets during forming processes is very different from that of monolithic steel sheets. During the deep-draw forming

Wenning Liu; Xin Sun; Robert Ruokolainen; Xiaohong Gayden

2007-01-01

436

Advanced calculation of the room-temperature shapes of thin unsymmetric composite laminates  

Microsoft Academic Search

It is well known that the room-temperature shapes of unsymmetric laminates do not always conform to the predictions of classical lamination theory. Instead of being saddle shaped, as classical lamination theory predicts, the room-temperature shapes of unsymmetrically laminated composites are often cylindrical in nature. In addition, a second cylindrical shape can sometimes be obtained from the first by a simple

M. W. Hyer

1995-01-01

437

Advanced Calculation of the Room-Temperature Shapes of Unsymmetric Laminates  

Microsoft Academic Search

It is well known that the room-temperature shapes of unsymmetric laminates do not always conform to the predictions of classical lamination theory. Instead of being saddle shaped, as classical lamination theory predicts, the room-temperature shapes of unsymmetrically laminated composites are often cylindrical in nature. In addition, a second cylindrical shape can sometimes be obtained from the first by a simple

M. Schlecht; K. Schulte

1999-01-01

438

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

439

Interlaminate Deformation in Thermoplastic Composite Laminates: Experimental-Numerical Correlation  

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

440

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

441

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

442

An advanced higher-order theory for laminated composite plates with general lamination angles  

NASA Astrophysics Data System (ADS)

This paper proposes a higher-order shear deformation theory to predict the bending response of the laminated composite and sandwich plates with general lamination configurations. The proposed theory a priori satisfies the continuity conditions of transverse shear stresses at interfaces. Moreover, the number of unknown variables is independent of the number of layers. The first derivatives of transverse displacements have been taken out from the inplane displacement fields, so that the C0 shape functions are only required during its finite element implementation. Due to C0 continuity requirements, the proposed model can be conveniently extended for implementation in commercial finite element codes. To verify the proposed theory, the fournode C0 quadrilateral element is employed for the interpolation of all the displacement parameters defined at each nodal point on the composite plate. Numerical results show that following the proposed theory, simple C0 finite elements could accurately predict the interlaminar stresses of laminated composite and sandwich plates directly from a constitutive equation, which has caused difficulty for the other global higher order theories.

Wu, Zhen; Zhu, Hong; Chen, Wan-Ji

2011-10-01

443

Extracellular Matrix Assembly in Diatoms (Bacillariophyceae) (I. A Model of Adhesives Based on Chemical Characterization and Localization of Polysaccharides from the Marine Diatom Achnanthes longipes and Other Diatoms).  

PubMed Central

Extracellular adhesives from the diatoms Achnanthes longipes, Amphora coffeaeformis, Cymbella cistula, and Cymbella mexicana were characterized by monosaccharide and methylation analysis, lectin-fluorescein isothiocyanate localization, and cytochemical staining. Polysaccharide was the major component of adhesives formed during cell motility, synthesis of a basal pad, and/or production of a highly organized shaft. Hot water-insoluble/hot 0.5 M NaHCO3-soluble anionic polysaccharides from A. longipes and A. coffeaeformis adhesives were primarily composed of galactosyl (64-70%) and fucosyl (32-42%) residues. In A. longipes polymers, 2,3-, t-, 3-, and 4-linked/substituted galactosyl, t-, 3-, 4-, and 2-linked fucosyl, and t- and 2-linked glucuronic acid residues predominated. Adhesive polysaccharides from C. cistula were EDTA-soluble, sulfated, consisted of 83% galactosyl (4-, 4,6-, and 3,4-linked/substituted) and 13% xylosyl (t-, 4f/5p-, and 3p-linked/substituted) residues, and contained no uronosyl residues. Ulex europaeus agglutinin uniformly localized [alpha](1,2)-L-fucose units in C. cistula and Achnanthes adhesives formed during motility and in the pads of A. longipes. D-Galactose residues were localized throughout the shafts of C. cistula and capsules of A. coffeaeformis. D-Mannose and/or D-glucose, D-galactose, and [alpha](t)-L-fucose residues were uniformly localized in the outer layers of A. longipes shafts by Cancavalia ensiformis, Abrus precatorius, and Lotus tetragonolobus agglutinin, respectively. A model for diatom cell adhesive structure was developed from chemical characterization, localization, and microscopic observation of extracellular adhesive components formed during the diatom cell-attachment process.

Wustman, B. A.; Gretz, M. R.; Hoagland, K. D.

1997-01-01

444

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

445

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

446

Wave propagation in a graphite/epoxy laminate  

NASA Technical Reports Server (NTRS)

Harmonic wave and wave front propagations in a graphite/epoxy laminate are investigated using a plate theory that includes transverse shear deformation. Transient waves produced by impact of a steel ball are studied experimentally and by using finite elements. The statically measured law of contact between the steel ball and the laminate is used in the finite element program to compute the dynamic contact force. It is found that use of this contact law in conjunction with the finite element modeling of the laminate yields excellent agreement with the experimental results.

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

1983-01-01

447

Improved PMR Polyimides For Heat-Stable Laminates  

NASA Technical Reports Server (NTRS)

Second-generation PMR-type polyimides (PMR-II polyimides) of enhanced thermo-oxidative stability prepared by substitution of para-aminostyrene (PAS) end caps for nadic-ester (NE) end caps used in prior PMR-II polyimides. Laminates unidirectionally reinforced with graphite fibers and made with PAS-capped resins exhibited thermo-oxidative stabilities significantly greater than those of similar laminates made with NE-capped PMR-II resins. One new laminate exhibited high retention of weight and strength after 1,000 h of exposure to air at 371 degrees C.

Vannucci, R. D.; Malarik, D. C.; Papadapoulos, D. S.; Waters, John F.

1994-01-01

448

Stress and strength of laminated composite containing a circular hole  

NASA Astrophysics Data System (ADS)

This dissertation is to study the stress and strength of a finite laminated plate containing a circular hole subjected to tension. Efforts were made in three aspects: theoretical modeling, computer simulation using finite element method, and experimental evaluation using unidirectional and crossply Scotchply laminates. The stress concentration factor, normal stress distribution and tensile strength of laminates with various hole sizes and gage lengths were investigated. Theoretically, two models were proposed to describe the normal stress distribution of a laminate with finite width and finite length. By defining a width correction function and a size correction function, the normal stress in a laminate with finite width and finite size was predicted in terms of the normal stress in an infinite laminate. The introduction of width correction function and size correction function was based upon the elastic solutions of finite and infinite isotropic plates containing a circular hole. Experimental work was performed on laminated specimens made of unidirectional and crossply Scotchply laminates. Width effect, or hole size effect, was studied using 2? wide specimens with hole size varying from 0.1? to 1.5? (the corresponding d/W ratio from 0.05 to 0.75). Specimens with different lengths were tested. Both initial tensile strength and ultimate (rupture) strength were obtained for specimens with various hole sizes and gage lengths. Strain gages were also used in several specimens to check normal stress distribution. Finite element method was extensively used in the stress analysis of the unidirectional and crossply laminates in this study. COSMOS software was utilized which has the capability to model laminated composites. Composite quadrilateral plate elements were used for the laminates. A total of 29 cases were analyzed to obtain the stress concentration factor, normal stress distribution, and initial tensile strength for laminates with various hole sizes and lengths. The results of this study showed that the proposed models provide better stress and strength predictions than existing models. The predictions from the proposed models agree well with the experimental data and results from the finite element analysis.

Zhao, Yi

449

An approximate solution for interlaminar stresses in composite laminates  

NASA Technical Reports Server (NTRS)

An efficient approximate solution for interlaminar stresses in finite width, symmetric and unsymmetric laminated composites subjected to axial and/or bending loads is presented. The solution is based upon statically admissible stress fields which take into consideration local property mismatch effects and global equilibrium requirements. Unknown constants in the assumed stress states are determined through minimization of the laminate complementary energy. Typical results are presented for through-thickness and interlaminar stress distributions for angle-ply and cross-ply laminates subjected to axial loading. It is shown that the present formulation represents an improved, efficient approximate solution for interlaminar stresses.

Rose, Cheryl A.; Herakovich, Carl T.

1993-01-01

450

Prediction of microcracking in composite laminates under thermomechanical loading  

NASA Technical Reports Server (NTRS)

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

Maddocks, Jason R.; Mcmanus, Hugh L.

1995-01-01

451

Characterization and quantitation of three B-type lamins in Xenopus oocytes and eggs: increase of lamin LI protein synthesis during meiotic maturation.  

PubMed

We have previously shown that Xenopus oocytes, eggs, and early embryos contain lamins LII and LIII, and that portions of each are associated with distinct egg vesicle populations. We now report that a lamin similar or identical to the B-type lamin LI is also present in oocyte nuclei and in egg extracts. We have quantitated the three B-type lamins per oocyte nucleus, and have calculated relative ratios of LI:LIII = 1:100, and LII:LIII = 1:10. Similar to lamin LII, 5-15% of lamin LI is associated with egg membranes in a biochemically stable manner. Egg vesicles absorbed with lamin isoform-specific antibodies to magnetic beads indicate that lamin LI-associated egg membranes are of heterogenous morphology, and are independent from the lamin LII and LIII vesicle populations. Compared to other nuclear envelope proteins, the synthesis of lamin LI protein is specifically elevated during meiotic maturation, resulting in a 4- to 12-fold higher amount of lamin LI in eggs than is present in oocyte nuclei. Immunofluorescence and immunoblot analysis demonstrated that lamins LI, LII, and LIII are associated with the nuclear envelope formed on demembranated sperm when added to activated egg extract. These results strongly suggest that three different lamin-associated vesicle populations are involved in the formation of a nuclear envelope in egg extracts. PMID:8832400

Lourim, D; Kempf, A; Krohne, G

1996-07-01

452

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

PubMed

Seasonal variations in the fouling diatom community from a monsoon influenced tropical estuary were investigated. The community composition did not differ significantly between stainless steel and polystyrene substrata due to dominance by Navicula spp. The experimental evidence suggests that Amphora, which is a dominant fouling diatom in temperate waters, ultimately dominates the community in tropical regions when conditions are favourable. These observations reveal that a faster onset of macrofouling interferes with the microfouling community wherein the faster recruiters that have a higher abundance in ambient waters, dominate the community. Seasonal variations were observed in the fouling diatom community. Navicula delicatula dominated during the post-monsoon and tychopelagic diatoms (Melosira and Odontella) were observed during the monsoon. Low diatom abundance was recorded during the pre-monsoon season. The results indicate that although the fouling diatom community composition does not vary between substrata, there is a seasonal change in the community depending on the physical, chemical and biological interactions. PMID:18668383

Mitbavkar, Smita; Anil, Arga Chandrashekar

2008-01-01

453

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

454

Impact resistance of composite laminated sandwich plates  

NASA Astrophysics Data System (ADS)

Investigated are the effects of face layup sequence and core density of a sandwich plate on the impact delamination area of the laminated facesheet. The sandwich plate is made of graphite/epoxy faces and Nomex honeycomb core. The size and shape of delamination due to impact at each interply location have been measured by the room temperature deply technique. The shape of the interply delamination under impact is, in general, found to be two-lobed. The shape exhibits very peculiar regularity under various experimental conditions. The quantitative measurement of delamination size has shown that the face layup with small relative orientation between adjacent plies and high density core are desirable in sandwich plates to reduce the impact delamination.

Kim, Chun-Gon; Jun, Eui-Jin

455

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

456

Thermally induced local effects in laminated composites  

SciTech Connect

The steady-state thermally induced local effects in laminated composite materials are investigated from the micro- and macromechanical points of view. The micromechanical model is represented by the alternating layers of a perfectly bonded matrix-reinforcement system, while the macromechanical counterpart is characterized by the effective thermal and mechanical properties of the constituent layers. The solutions are obtained within the framework of linear plane thermoelasticity via the Fourier transform technique and the flexibility/stiffness matrix method. As a numerical illustration, the micro- and macromechanical temperature and thermal stress fields due to given surface temperature distributions are presented to measure the degree of correspondence between the two models. Considerable discrepancies are observed to exist between the micro- and macromechanical thermal stress fields, especially, in regions involving high temperature gradients. 21 refs.

Choi, H.J.; Thangjitham, Surot (Virginia Polytechnic Institute and State University, Blacksburg (United States))

1992-06-01

457

Permeability After Impact Testing of Composite Laminates  

NASA Technical Reports Server (NTRS)

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

Nettles, Alan T.

2003-01-01

458

Permeability After Impact Testing of Composite Laminates  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

459

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.

2014-04-01

460

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

461

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

462

Influence of bending-twisting and extension-bending coupling on damping of laminated composites  

Microsoft Academic Search

This paper describes a three-dimensional finite element-strain energy method for characterizing vibration coupling effects on damping of laminated composites. The analysis was performed on graphite-epoxy laminated cantilever beams in two stacking sequences: (i) 12-ply symmetric laminates [12(?)], and (ii) 12-ply antisymmetric laminates [6(?)\\/6(-?)]. Thus, the effects of vibration coupling between bending and twisting in symmetric laminates, and between extension and

S. J. Hwang; R. F. Gibson

1993-01-01

463

Germanium incorporation into the silica of diatom cell walls  

Microsoft Academic Search

1.The diatoms, Nitzschia alba, Navicula pelliculosa, Cylindrotheca fusiformis, and Cyclotella nana, took up radioisotopically labelled germanic acid, 68Ge(OH)4, from their growth media and incorporated up to 80% of it into the silica of their cell walls. Silicification appeared to be required for germanium incorporation.2.The uptake and incorporation of germanic acid was dependent upon the relative concentrations of Ge(OH)4 and Si(OH)4,

Farooq Azam; Barbara B. Hemmingsen; Benjamin E. Volcani

1973-01-01

464

Screening of diatoms for heterotrophic eicosapentaenoic acid production  

Microsoft Academic Search

Nine strains of diatoms (representing four species) were screened for their ability to produce eicosapentaenoic acid (EPA) when cultured heterotrophically on glucose. Four strains were able to produce EPA heterotrophically using glucose as its carbon and energy source. Of the four,Nitzschia laevis was the best EPA producer, yielding 0.017 g g?1 dry cell weight.N. laevis was the only species tested

Chor Koon Tan; Michael R. Johns

1996-01-01

465

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

466

The winter-spring diatom flowering in Narragansett Bay  

Microsoft Academic Search

Weekly observations of phosphate, nitrate, silicate, and phytoplankton over a 4%-year period are analyzed to explain year-to-year variations in the time of inception and magni- tude of the winter-spring diatom flowering in Narragansett Bay, Rhode Island. The popu- lation during this period (November-June) is dominated by Skeletonemu costatum. The start of growth does not appear to be related to stability,

DAVID M. PRATT

1965-01-01

467

The diatom genus Actinocyclus in the Western United States  

USGS Publications Warehouse

Ten new and four known taxa of the diatom genus Actinocyclus are described, illustrated, and (or) noted from middle Miocene lake deposits in the Western United States. A key is presented to help separate the taxa based on morp