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1

The dissolution kinetics of diatom ooze from the Antarctic area  

NASA Astrophysics Data System (ADS)

The dissolution kinetics of Antarctic diatom ooze was investigated in seawater at various pH's and temperatures. The slow dissolution rate of the ooze was mostly due to the presence of inhibitors postfixed on the surface layer of silica skeletons, which partly were removed by the acid treatment; inhibitors reformed gradually around the surface of acid-cleaned skeletons. The dissolution process was quite different from that of silica skeletons prepared from living diatoms, and could be described by parabolic kinetics; the concentration of dissolved silica from the diatom ooze is proportional to square root of time. The parabolic rate constant, K, had a good relationship with pH and with temperature; the constant estimated by temperature and pH in deep waters of the Antarctic area was calculated to be ( 1.1 ˜ 2.3) × 10 -11mol cm -2 h - 1/2.

Kamatani, Akiyoshi; Ejiri, Nobuhiko; Treguer, Paul

1988-07-01

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

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

USGS Publications Warehouse

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

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

1994-01-01

5

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

6

The geochronology of foraminiferal ooze deposits in the "Southern Ocean"  

USGS Publications Warehouse

Many cores raised from the Drake Passage are characterized by alternating zones of foraminiferal ooze and sandysilt. Cores raised from the East Pacific Rise are foraminiferal ooze or alternating siliceous and carbonate ooze. The uranium and thorium concentrations and isotopic ratios in foraminifers separated from these cores were measured by alpha-spectroscopy. 230Th in foraminiferal tests is found to be out of equilibrium with its parent (234U), enabling the “excess 230Th” method to be used in estimating sedimentation rates. The uranium concentration of the tests is constant, suggesting constant uranium concentrations in the sea and thus constant production of 230Th during periods of foraminiferal production. 232Th concentration is 2.1 ± 0.7 ppm in the Drake Passage and below the level of detection in tests from the East Pacific Rise. Within each core the 232Th is constant, varying closely with distance from the source. Based on the degree of disequilibrium of 230Th, correlations between cores can be made. Age estimates of the foraminiferal zones indicate deposition occurred between 8 000 and 120 000 and between 190 000 and 280 000 years before present. Reported dates of high stands of the sea fall between the ages estimated for the foraminiferal zones, suggesting these zones were deposited during northern hemisphere glacial maxima.

Holmes, Charles W.; Osmond, J.K.; Goodell, H.G.

1968-01-01

7

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

8

The isotopic composition of diatom-bound nitrogen in Southern Ocean sediments  

Microsoft Academic Search

Treatment of diatom microfossils from Southern Ocean sediments with hot perchloric acid leaves a ``diatombound'' N fraction which is 0-40\\/00 lower in delta15N than the bulk sediment, typically 30\\/00 lower in recent Antarctic diatom ooze. Results from Southern Ocean surface sediments indicate that early diagenetic changes in bulk sediment N content and delta15N are not reflected in diatom-bound N, suggesting

Daniel M. Sigman; Mark A. Altabet; Roger Francois; Daniel C. McCorkle; Jean-Francois Gaillard

1999-01-01

9

Invertebrate lamins  

SciTech Connect

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

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

2007-06-10

10

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. PMID:20826548

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

2010-01-01

11

Laminate article  

DOEpatents

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

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

2002-01-01

12

Hybrid composite laminate structures  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

13

Intramural hematoma and oozing rupture of left atrium after resection of wide-based left atrial myxoma.  

PubMed

We describe a rare complication after the resection of the left atrial (LA) myxoma. After tumor resection, a large defect of the endocardium was reinforced with an autologous pericardial patch. Transesophageal echocardiography demonstrated a hematoma and pulsatile flow beneath the patch, without patch perforation or detachment. Bleeding increased after closure of the sternum. Intramural hematoma and oozing rupture of the LA were diagnosed. A small intramural vessel of the LA was identified as the main causative site of bleeding. The pericardial patch was repositioned with fibrin glue. Fibrin sheets and glue were applied for reinforcement of the LA from outside. PMID:25046973

Ohira, Suguru; Doi, Kiyoshi; Maeda, Sachiko; Yaku, Hitoshi

2014-10-01

14

Diatomic Spectral Database  

National Institute of Standards and Technology Data Gateway

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

15

Zeolitisation of diatoms.  

PubMed

The development of low cost hierarchical porous materials based upon the zeolitisation of diatomaceous earth for fluid waste benification is described. Two preparative approaches invole: first, using the diatom as a support for zeolite nanocrystals; second, direct pseudomorphic transformation of the diatom into a zeolite. These hierarchical porous materials are potentially useful for important industrial processes in ion-exchange, catalysis and waste benefication. PMID:15762166

Anderson, M W; Holmes, S M; Mann, R; Foran, P; Cundy, C S

2005-01-01

16

Plasmids in diatom species.  

PubMed Central

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

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

1991-01-01

17

The lamin protein family  

PubMed Central

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

2011-01-01

18

Nuclear lamins and neurobiology.  

PubMed

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

Young, Stephen G; Jung, Hea-Jin; Lee, John M; Fong, Loren G

2014-08-01

19

Influence of Lamination Pressure upon the Stiffness of Laminated Rotor  

NASA Astrophysics Data System (ADS)

In recent years, a laminated rotor made of the insulated silicon steel laminates is increasingly adopted in the electrical machineries. While this laminated rotor offers good electrical performances, it is quite complicated to predict its stiffness as it is influenced by various factors such as material properties and shape of the laminates, characteristics of the insulation layer, lamination pressure and method of fitting. As it is difficult to model or define boundary conditions in the case of lamination pressure or fitting, the stiffness of the laminated rotor cannot simply calculated using conventional analytical method. Therefore, quantitative investigation on the influence of lamination pressure upon the stiffness of laminated rotor is highly required. In this study, natural frequency of the rotor is measured under various conditions of lamination pressure to investigate the influence of lamination pressure upon the stiffness of laminated rotor. It is found from the experiment that the natural frequency is increased with lamination pressure, and saturated near the 20% of the difference between the inner and outer diameters of the laminate. It is also found that the natural frequency can be controlled to 4-14% in the range of 1-10MPa of lamination pressure. The saturated value of the stiffness of laminated rotor is expected to approach to that of shrinkage-fitted cylinder having the same inner and outer diameters under the same assembly condition. It is expected that the results would be helpful to design generators or motors using laminated rotors.

Kim, Yeong-Chun; Kim, Kyung-Woong

20

Direct thrombin inhibitor (DTI) vs. aspirin in primary total hip and knee replacement using wound ooze as the primary outcome measure. A prospective cohort study.  

PubMed

The latest NICE guidance dictates that all patients undergoing lower-limb arthroplasty should be prescribed potent venous thromboembolic (VTE) prophylaxis. However, use of potent anti-thrombotics is likely to lead to increased post-operative wound ooze. Postoperative wound ooze is associated with increased risk of infection. This study used a prospective, consecutive, multi-surgeon sample of 110 patients undergoing primary total hip replacement (THR) and total knee replacement (TKR) prescribed either direct thrombin inhibitor (DTI) (n=51, 26 males: 25 females, age 69 ±18) or aspirin (n=59, 25 males: 34 females, age 69 ± 19). Hospital stay, body mass index (BMI), wound length and patient demographics were documented along with a daily assessment of wound ooze. The use of DTI's was associated with a significant increase in mean days to dryness in both THR (6.2 ± 0.98, 95% C.I. 5.2-7.1) and TKR (6.6 ± 1.89, 95% C.I. 4.7-8.5) compared to aspirin in THR (3.0 ± 1.03, 95% C.I 1.9-4.0) and TKR (3.4 ± 1.21, 95% C.I 2.2-4.6) with p-values of <0.0001 and 0.0024 for THR and TKR respectively. Age, gender and wound length were not found to be significant confounding variables. DTI's proven benefit in lowering venous thromboembolism when compared with aspirin needs to be balanced with their increased cost and increased duration of wound ooze. PMID:22362503

Aquilina, Alexander L; Brunton, Luke R; Whitehouse, Michael R; Sullivan, Niall; Blom, Ashley W

2012-01-01

21

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. PMID:24563357

Gonzalo, Susana

2014-01-01

22

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

23

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

24

Parasitic diatoms inside antarctic sponges.  

PubMed

Antarctic sponges may host large populations of planktonic and benthic diatoms. After settling on the sponge, these diatoms enter its body through pinacocytes (1) and form, there, large mono- or pauci-specific assemblages. Yet the total amount of carbohydrates in the invaded sponge tissue is inversely correlated with that of chlorophyll-a. We suggest, therefore, that endobiont diatoms utilize the products of the metabolism of their host as an energy source. This is the first evidence indicating that an endobiotic autotrophic organism may parasitize its animal host. Moreover, this unusual symbiotic behavior could be a successful strategy that allows the diatom to survive in darkness. PMID:10707811

Bavestrello, G; Arillo, A; Calcinai, B; Cattaneo-Vietti, R; Cerrano, C; Gaino, E; Penna, A; Sarà, M

2000-02-01

25

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

NASA Astrophysics Data System (ADS)

The Southern Ocean remains the least studied region on Earth with respect to Holocene climate variability. The few Antarctic proximal marine sedimentary records available tend to be short, low resolution, and discontinuous. However, sediments recently recovered from the Adélie drift during IODP Expedition 318 present a new opportunity to study East Antarctic Holocene climatic evolution, at a resolution that facilitates direct comparison with ice-cores. Expedition 318 recovered 171m of Holocene laminated diatom ooze from site U1357B. The sediments represent continuous Holocene accumulation up to the present day (based on 89 AMS 14C dates) and are characterised by 2-6cm thick, light/dark laminae couplets, interpreted as seasonal biogenic production and accumulation events. We present the results of initial biomarker analyses: fatty acid ?D and TEX86 measurements on lipid extracts from paired light/dark laminae throughout the Holocene. The C18 fatty acid is assumed to represent an integrated signal from the algal precursors and thus surface water conditions. The ?DC18-FA values show no consistent offset between the light and dark laminae, and values become isotopically heavier on average through the Holocene (ca. -220 to 140‰), in line with declining insolation at 65°S. Superimposed on this trend are millennial scale isotopic excursions of ca. 20 to 60‰, including a clear excursion coeval with an increase in grain size in U1356B and the late Holocene climate 'optimum' between 6 and 3 kyr, inferred from East Antarctic ice-cores. ?DC18-FA shows no clear relationship with TEXL86 sea-surface temperature estimates, which display pronounced early variability and relative warmth from 11.2 to 10.4 ka (0 to 6.5 °C, average ca. 3.5 °C), but almost no change after 10.4 ka, as cold, stable SSTs (average ca. 2 °C) persist through the rest of the Holocene. We explore the potential controls on the ?DC18-FA record and suggest the influence of isotopically depleted meltwater from the proximal ice-sheet (additive to a salinity effect) and/or upwelling could account for the millennial scale variability. The next steps are to ground-truth the proxies in this unique archive and to exploit the paleoclimatic information encoded in the abundant algal sterol compounds, the higher plant waxes and to apply compound-specific ?13C as well as additional ?D measurements.

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

2012-12-01

26

Diatomic predissociation line widths  

NASA Technical Reports Server (NTRS)

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

Child, M. S.

1973-01-01

27

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

28

Diatom DNA as historical information  

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

29

Loosely-Bound Diatomic Molecules.  

ERIC Educational Resources Information Center

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

Balfour, W. J.

1979-01-01

30

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. PMID:22933565

Amin, Shady A.; Parker, Micaela S.

2012-01-01

31

Resin hybrid composite laminates  

SciTech Connect

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

Bhatnagar, A.

1986-01-01

32

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

33

Laminates and reinforced metals  

NASA Technical Reports Server (NTRS)

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

Chamis, C. C.

1980-01-01

34

Heat resistant nontoxic laminate  

NASA Technical Reports Server (NTRS)

Light-weight low-cost laminate used to replace epoxy compound panels is suitable for auto, railcar, and aircraft structural parts. Physical and thermal tests show panels made from formulation have better insulative properties, and burn cleaner with less toxic gas generation than panels made with conventional materials.

Kourtides, D. A.; Parker, J. A.

1979-01-01

35

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

36

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

Microsoft Academic Search

The Antarctic ice sheet plays a key role in global oceanic and atmosphere systems. One of the most dynamic regions of the continent is the Antarctic Peninsula (AP) where ecological and cryospheric systems respond rapidly to climate change, such as the last deglaciation ( ˜12-13 kyr BP). Here, deglacial laminated diatom-rich marine sediments are well known, e.g., Palmer Deep (64°

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

2004-01-01

37

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

Microsoft Academic Search

The Latest Cretaceous (Maastrichtian) Marca Shale Member, California, displays a well-preserved record of alternating terrigenous and diatomaceous laminae couplets, remarkably similar in lithology to recent laminated sediments from the Gulf of California and Santa Barbara Basin. This similarity, together with the recognition of intra- and inter-annual variability in the diatom flora, implies an annual origin for these couplets. High-resolution backscattered

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

2005-01-01

38

Laminated piezoelectric transformer  

NASA Technical Reports Server (NTRS)

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

Vazquez Carazo, Alfredo (Inventor)

2006-01-01

39

Solar cell module lamination process  

DOEpatents

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

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

2002-01-01

40

Renaissance in diatomic spectroscopy  

NASA Astrophysics Data System (ADS)

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

Tiemann, Eberhard; Knöckel, Horst

2013-07-01

41

Diatom genomics: genetic acquisitions and mergers.  

PubMed

Diatom algae arose by two-step endosymbiosis. The complete genome of the diatom Thalassiosira pseudonana has now been sequenced, allowing us to reconstruct the remarkable intracellular gene transfers that occurred during this convoluted cellular evolution. PMID:15620637

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

2004-12-29

42

Equine laminitis caused by distal displacement of the distal phalanx: 12 cases (1976-1985).  

PubMed

Clinical data from 12 cases of equine laminitis characterized by distal displacement of the distal phalanx (P3) were reviewed. Clinical features of horses that survived the syndrome were compared with the nonsurvivors to obtain prognostic indicators. Animals affected included 8 Quarter Horses, 2 Welsh ponies, 1 Thoroughbred, and 1 Arabian. Eight of the animals were females (67%), 2 were stallions, and 2 were geldings. The mean age of affected animals was 8.6 years (2 to 14 years), and the mean body weight was 442 kg. The survivors weighed less than the nonsurvivors (384 kg vs 473 kg, respectively), suggesting that body weight may be of prognostic value for horses affected with distal displacement of P3. Ten of the 12 animals (83%) were admitted because of a disorder other than laminitis, but subsequently developed laminitis during the treatment period. All affected animals had clinical evidence of endotoxemia and/or sepsis before the onset of laminitis. Cavitation or depression of the dorsal coronary band was detected in all animals and was the most reliable clinical indicator of distal displacement of P3. Five horses had fluid (blood or serum) ooze from their coronary bands and 2 of these sloughed one or more of their hooves. Necropsy findings of the 8 horses that were euthanatized included severe hemorrhagic, congested laminae and complete detachment of P3 from the hoof wall. Histologic examination of affected laminae revealed vascular thrombosis and multifocal areas of hemorrhage and necrosis. Radiography failed to reveal distal displacement of P3 in 8 animals, but the remaining 4 animals had an accentuation of the dorsal proximal hoof wall and cavitation of the coronary band visible on lateral radiographs. PMID:3744996

Baxter, G M

1986-08-01

43

Lamin A, lamin B, and lamin B receptor analogues in yeast  

Microsoft Academic Search

Previous studies have shown that turkey erythrocyte lamin B is anchored to the nuclear enve- lope via a 58-kD integral membrane protein termed p58 or lamin B receptor (Worman H. J., J. Yuan, G. Blobel, and S. D. Georgatos. 1988. Proc. Natl. Acad. Sci. USA. 85:8531-8534). We now identify a p58 analogue in the yeast Saccharomyces cerevisiae. Turkey erythrocyte lamin

Spyros D. Georgatos; Ioanna Maroulakou; Gfinter Blobel

1989-01-01

44

Thermal conductivity of graphene laminate.  

PubMed

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

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

2014-09-10

45

Subclinical laminitis in dairy heifers  

Microsoft Academic Search

By causing poorer horn quality, subclinical laminitis is considered to be a major predisposing cause of other hoof problems, particularly sole ulcers in newly calved heifers. In this study the hind hooves of 136 female Friesian\\/Holstein cattle aged between four months and two years were examined to discover at what age the signs of subclinical laminitis appeared. Sole haemorrhages were

HK Bradley; D Shannon

1989-01-01

46

Holographic nondestructive testing of laminates  

NASA Technical Reports Server (NTRS)

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

Stuckenberg, F. H.

1973-01-01

47

Driven Diatomic Oscillator Chain Model  

NSDL National Science Digital Library

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

Christian, Wolfgang

2008-07-05

48

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.

49

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. PMID:23146893

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

2012-01-01

50

Subclinical laminitis in dairy heifers.  

PubMed

By causing poorer horn quality, subclinical laminitis is considered to be a major predisposing cause of other hoof problems, particularly sole ulcers in newly calved heifers. In this study the hind hooves of 136 female Friesian/Holstein cattle aged between four months and two years were examined to discover at what age the signs of subclinical laminitis appeared. Sole haemorrhages were found in the hoof horn of calves as young as five months. The consistent finding of these lesions in heifers of all ages indicated that subclinical laminitis of varying degree was a common condition during the early growing period of young dairy heifers. PMID:2800281

Bradley, H K; Shannon, D; Neilson, D R

1989-08-19

51

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

52

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

53

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

54

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

55

Risk factors for equine laminitis  

E-print Network

logistic regression to assess age, breed, sex, and seasonality as risk factors for equine laminitis. There were 70 acute cases, 183 chronic cases, and 779 controls. No statistical association was found between age, breed, sex, or seasonality...

Polzer, John Patrick

2012-06-07

56

Introduction and Motivation Structural Model for Laminated Glass Beams Conclusions and Outlook of Laminated Glass Structures  

E-print Network

Introduction and Motivation Structural Model for Laminated Glass Beams Conclusions and Outlook Analysis of Laminated Glass Structures for Photovoltaic Applications Holm Altenbach Otto November 5th, 2013 Hameln, Germany November 5th, 2013 Holm Altenbach Analysis of Laminated Glass Structures

57

SPECTRUM FATIGUE LIFETIME AND RESIDUAL STRENGTH FOR FIBERGLASS LAMINATES  

E-print Network

SPECTRUM FATIGUE LIFETIME AND RESIDUAL STRENGTH FOR FIBERGLASS LAMINATES by Neil Kelly Wahl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Fiberglass Laminates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Fatigue Trends of Fiberglass Laminates

58

Multiple late Quaternary episodes of exceptional diatom production in the Gulf of Alaska  

NASA Astrophysics Data System (ADS)

Hole 887B of the Ocean Drilling Program (ODP) comprises a 44 m (750 kyr) long continuous section recovered from the Patton-Murray Rise, an elevated plateau that is largely isolated from turbidite deposition. The Patton-Murray area is centered under the Alaska Gyre, a region characterized by the domal upwelling of nutrient-rich waters. Marked increases in productivity and rapid settling of biogenic matter are suggested throughout the section by the episodic accumulation of diatomaceous oozes up to ˜1 m thick that are accompanied by barium enrichments. Significant ?13C org maxima in the major diatomaceous bands suggest that mixed-layer [CO 2(aq)] may have been drawn down significantly during some of the productivity events. The episodes of enhanced productivity at Site 887 occur synchronously with short-lived minima in planktonic foram ?18O, suggesting a direct link to low salinity, or less likely, warming, events in the Gulf of Alaska. There is no obvious explanation for the events, but they may be related to seasonal incursions of meltwater from Alaska. We speculate that episodic input of meltwater- or dust-borne iron from Asian or Alaskan sources may have promoted the extraordinary diatom production events recorded in the sedimentary record.

McDonald, D.; Pedersen, T. F.; Crusius, J.

1999-11-01

59

Some Observations of Diatoms Under Turbulence  

Microsoft Academic Search

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

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

2009-01-01

60

Diatom biomineralization reflected in diatom B/Si  

NASA Astrophysics Data System (ADS)

Because boron speciation in seawater is controlled by pH there has been wide interest in using the concentration and isotopic composition of B in marine biominerals to reconstruct past changes in ocean pH. Biomineralization may modulate B incorporation either through cellular pH regulation or uptake processes. We investigate the effect of biomineralization on B incorporation in opal from diatoms. Two species of diatoms, Thalassiosira weissflogii and T. pseudonana, were cultured at pH between 7.4 and 8.6, equivalent to pCO2 from 2000 to 200 ppmv. Growth rate, type of carbon acquisition, and silicon and carbon quotas were determined. Harvested opal was thoroughly cleaned of organic matter using permanganate and perchloric acid oxidative treatments. The boron content of opal was determined by mounting cleaned frustules in epoxy resin for measurement of 11B and 28Si on LA-ICPMS (Resonetics, Agilent 7700 ). LA-ICPMS measurements are reproducible from one session to the next and indicate B concentrations in T. pseudonana ranging from 7 to 40 ppm and in T. weissflogii from 4 to 9 ppm. B content in T. pseudonana is correlated with bicarbonate uptake rate and with normalized Si quotas, while for T. weissflogii, which is a bicarbonate-restricted user at the pH studied, B content seems to be regulated primarily by the borate/bicarbonate seawater ratio. We present a simple cellular model of B and Si uptake by diatoms to quantitatively explore the mechanisms for variable B content and its potential as a proxy .

Stoll, H.; Mejia-Ramirez, L. M.; Isensee, K.; Mendez-Vicente, A.; Pisonero, J.

2012-04-01

61

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

62

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

63

DDD: Dynamic Database for Diatomics  

NASA Technical Reports Server (NTRS)

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

Schwenke, David

2004-01-01

64

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

65

Hypothesized resource relationships among African planktonic diatoms  

Microsoft Academic Search

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

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

1985-01-01

66

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

67

Thermal stresses in laminated beams  

E-print Network

. 11 zz. i 1 1 . 2 2 -C D e ( ? )+C e i 2 i t i 11 zz. 2 13 zz. i i -[C +C 3]n T. i (11) Force and Moment Resultants Consider a laminated beam which is subjected to thermal and external loads. Bending is produced by the difference.... a XX. + dX 1 i 3X st. 0 I Xz I I Fig. 4. Transverse Normal and Shear Stresses Acting on a Section of the Laminated Beam. The equations of equilibrium in the x and z directions of a typical beam section are as follows: z=z I' z=0 30 XX . I...

Marcano, Victor Manuel

2012-06-07

68

MEMS optical acoustic sensors manufactured in laminates  

Microsoft Academic Search

Latest advancement in printed circuit board (PCB) technologies and discoveries of novel laminate materials has enabled a series of laminate MEMS devices to be designed, fabricated, and productized. To demonstrate the benefit in design and fabrication using the Laminate MEMS technology, we introduce embedded MEMS optical sensors fabricated directly within PCB layers. Free-standing polymeric waveguides translate acoustic signals into optical

Yang Zhang; Jonas Tsai; G. P. Li; Mark Bachman

2011-01-01

69

Basic mechanics of laminated composite plates  

NASA Technical Reports Server (NTRS)

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

Nettles, Alan T.

1994-01-01

70

A new lamin in Xenopus somatic tissues displays strong homology to human lamin A.  

PubMed Central

The nuclear lamina of vertebrates is composed of several major polypeptides that range in mol. wt from 60 to 80 kd. In mammals, the three major lamin proteins are designated A, B and C. Two major lamins have been described in Xenopus somatic tissues; two other lamins are expressed primarily in germ cells. We have analysed a cDNA clone encoding a Xenopus lamin that is highly homologous to human lamins A and C. The predicted protein has the carboxy-terminal domain characteristic of human lamin A and is thus a lamin A homologue. Surprisingly, the lamin encoded by the cDNA clone is not one of the known Xenopus lamins. The encoded protein is distinct in size from the oocyte lamin LIII and the two somatic lamins LI and LII. Monoclonal antibodies specific for LII, LIII and LIV (the lamin of male germ cells) do not recognize the protein encoded by the cDNA clone; conversely, a polyclonal antibody against the encoded protein does not recognize any of the known Xenopus lamins. This lamin is expressed late in embryonic development, and is present in all adult somatic cells examined, except erythrocytes. Thus frogs and mammals are similar in having three major somatic lamins that fall into distinct structural classes. Images Fig. 3. Fig. 4. Fig. 5. Fig. 6. Fig. 7. PMID:3428277

Wolin, S L; Krohne, G; Kirschner, M W

1987-01-01

71

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

72

Steady state response of unsymmetrically laminated plates  

SciTech Connect

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

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

1995-11-01

73

Superplasticity in laminated metal composites  

SciTech Connect

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

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

1998-10-20

74

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

75

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...

76

Reevaluating the green contribution to diatom genomes.  

PubMed

Photosynthetic diatom plastids have long been suggested to have originated by the secondary endosymbiosis of a red alga. However, recent phylogenomic studies report a high number of diatom nuclear genes phylogenetically related to green algal and green plant genes. These were interpreted as endosymbiotic gene transfers (EGT) from a cryptic green algal endosymbiosis. We reanalyzed this issue using a larger set of red algal genomic data. We show that previous studies suffer from a taxonomic sampling bias and point out that a majority of gene phylogenies are either poorly resolved or do not describe EGT events. We finally show that genes having a complete descent from cyanobacteria to diatoms through primary and secondary EGTs have been mostly transferred via a red alga. We conclude that, even if some diatom genes still support a putative green algal origin, these are not sufficient to argue for a cryptic green algal secondary endosymbiosis. PMID:22684208

Deschamps, Philippe; Moreira, David

2012-01-01

77

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. PMID:24957993

Bromke, Mariusz A.

2013-01-01

78

Nesting in textile laminates: geometrical modelling of the laminate  

Microsoft Academic Search

The nesting of reinforcements in textile laminates is studied using a 3D geometrical model of a woven, braided and non-crimp stitched fabrics in the relaxed and sheared state. The following fabric parameters were varied in the numerical experiments: flatness of the yarns, tightness and balance of the fabric, fabric weaving\\/braiding\\/knitted pattern, number of layers and degree of shear. Monte-Carlo modelling

S. V. Lomov; I. Verpoest; T. Peeters; D. Roose; M. Zako

2003-01-01

79

Biocide activity of diatom-silver nanocomposite  

Microsoft Academic Search

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

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

2010-01-01

80

Preservation potential of seasonal laminated deposits as a useful tool for environmental analysis in mesotrophic Lake Kizaki, central Japan  

NASA Astrophysics Data System (ADS)

In this paper discusses the aquatic environment at Lake Kizaki, central Japan, during the last ca. 60 years and describes the importance of laminated sediments in environmental analyses. The flux of total algal carbon increased between 1965 and 1996 while the BSi flux, which can be used in diatom production, showed a larger increase between 1960 and 1998 than typically occurs on average. The flux of dinosterol, an indicator of dinoflagellate production, also increased from 1966 to 1998, and the sedimentary dinoflagellate record correlated with observations of freshwater red tides caused by dinoflagellate blooms. Parallel laminated sediment was determined to have appeared between 1960 and 1995, corresponding to a period of high total algal carbon levels and BSi fluxes. For lamina formation and its preservation process, the thickness of the oxygen-poor layer depended on excessive total algal production during stagnant periods and appeared to be important because nutrients were diffused and accumulated in the oxygen-poor layer from bottom sediments. This could result in diatom blooms at the next overturn period. The development of the thick oxygen-poor layer appeared to be triggered primarily by the presence of excessive nutrients generated by human activities. In general, the occurrence of laminated sediments can provide a useful tool for understanding the eutrophic state in Lake Kizaki.

Ito, Takuma

2013-09-01

81

Postbuckling of laminated anisotropic panels  

NASA Technical Reports Server (NTRS)

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

Jeffrey, Glenda L.

1987-01-01

82

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

Microsoft Academic Search

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

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

2011-01-01

83

Coupled Simulation of Circuit and Piezoelectric Laminates  

E-print Network

In this paper, an algorithm for the coupled simulation of circuit and piezoelectric laminate devices is presented. A finite element solver for piezoelectric laminates is included in the SPICE framework as a capacitor. The charge of this capacitor is a function of both the terminal voltage and the mechanical strain in the piezoelectric material. The coupled simulator allows simulation of novel micropower generation circuits based on piezoelectric laminates. 1.

unknown authors

84

Geometrically nonlinear analysis of laminated elastic structures  

NASA Technical Reports Server (NTRS)

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

Reddy, J. N.

1984-01-01

85

Classification of laminate domain patterns in ferroelectrics  

NASA Astrophysics Data System (ADS)

Ferroelectric crystals are known to adopt low-energy, compatible domain configurations. Observations show that these configurations are commonly multirank laminate patterns. In this work, a method to classify and enumerate the laminate domain patterns that can form is presented. The criteria of exact compatibility for laminates structures in a ferroelectric single crystal are used to find all the rank-2 arrangements of domains in the polar tetragonal crystal system. Surprisingly, only eight distinct rank-2 laminate patterns that satisfy compatibility conditions at all domain walls are found. These patterns are classified and correlated with observations of domains in single crystals, showing good agreement.

Tsou, N. T.; Potnis, P. R.; Huber, J. E.

2011-05-01

86

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

87

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

88

Residual stresses in angleplied laminates and their effects on laminate behavior  

NASA Technical Reports Server (NTRS)

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

Chamis, C. C.

1978-01-01

89

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

90

Industrial laminates: manufacture, materials, and applications  

Microsoft Academic Search

Substrates for industrial laminates range from unbleached kraft paper, which looks like ordinary grocery bags, to the most exotic carbon fiber and other synthetic fibers. However, since most of the RIEA\\/1A Grades of laminates (majority of the market) use more common substrates such as bleached and unbleached kraft paper, cotton linter paper, cotton fabrics, nylon fabric and glass fabrics and

1995-01-01

91

Improved Fire-Resistant Resins for Laminates  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

92

Diversity dynamics of marine planktonic diatoms across the Cenozoic  

E-print Network

LETTERS Diversity dynamics of marine planktonic diatoms across the Cenozoic Daniel L. Rabosky1 for oceanic diatom diversity across the Cenozoic. Peak species diversity in marine planktonic diatoms occurred of Cenozoic microfossil occurrence collected from a globally dispersed network of 165 drilling sites11

Rabosky, Daniel L.

93

Diatom community structure on commercially available ship hull coatings  

Microsoft Academic Search

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

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

2011-01-01

94

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

Microsoft Academic Search

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

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

1988-01-01

95

[Chloroplast ultrastructure in some diatoms from different classes].  

PubMed

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

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

2009-01-01

96

Critical current of laminated and non-laminated BSCCO superconducting composite tape under bending strain  

NASA Astrophysics Data System (ADS)

It has been reported that, when the (Bi,Pb) 2Sr 2Ca 2Cu 3O x (hereafter noted as BSCCO)/Ag/Ag-alloy tape is laminated with stainless steel, the tensile strain tolerance of critical current is much improved. In this study, using the non-laminated and laminated BSCCO composite tapes fabricated at American Superconductor Corporation, the influences of lamination on the critical current and its distribution under bending strain were studied. The analysis of the measured variation of average critical current with bending strain based on the damage evolution model revealed that the laminated stainless steel acts to suppress the fracture of the BSCCO filaments. The experimentally observed high critical current retention of the laminated tape up to high bending strain was accounted for by the suppression of fracture of BSCCO filaments stated above and enhancement of the compressive residual strain in the filaments. The distributions of local critical current in non-laminated and laminated composite tape were described well by the three-parameter Weibull distribution function within the bending strain lower than 1.1%. The coefficient of variation of distribution of critical current of the laminated tape was similar to that of the non-laminated one under the same strain distribution in the core.

Matsubayashi, H.; Mukai, Y.; Arai, T.; Shin, J. K.; Ochiai, S.; Okuda, H.; Osamura, K.; Otto, A.; Malozemoff, A.

2009-10-01

97

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. PMID:22393432

Zaremba-Czogalla, Magdalena; Piekarowicz, Katarzyna; Wachowicz, Katarzyna; Kozio?, Katarzyna; Dubi?ska-Magiera, Magda; Rzepecki, Ryszard

2012-01-01

98

Partial Wave Theory of Diatomic Molecules. II  

Microsoft Academic Search

The method of expanding the wavefunction of diatomic molecules in a series of orbital angular momentum eigenfunctions (partial waves) is extended to two-electron homonuclear molecules. The angular momentum is a function of the Euler angles only; a symmetric choice of these angles is used which greatly facilitates the description of the exchange character of the wavefunction. As a result, explicit

A. Temkin; A. K. Bhatia

1965-01-01

99

Cenozoic history of Antarctic benthic diatoms  

Microsoft Academic Search

Antarctic Cenozoic climate changes have influenced the development of the Southern Ocean benthic diatom flora. When Antarctica and South America separated in the late Eocene (?37 Ma), giving rise to the proto-Antarctic Circumpolar Current (ACC), the environment gradually changed from temperate alpine glacial to subpolar with ice sheet development. By the early Oligocene (? 30 Ma), at least thirteen new

Jason M. Whitehead

2005-01-01

100

Paleodepth determination from Antarctic benthic diatom assemblages  

Microsoft Academic Search

Analysis of modern surface sediments from fjords in the Vestfold Hills (Antarctica) indicates that 58% of the variation in benthic diatom assemblages can be attributed to changes in environmental parameters with water depth. Attenuation of light through the water column is suggested to account for 45% of the variation, and the decrease in substrate grain size with depth possibly accounts

Jason M. Whitehead; Andrew McMinn

1997-01-01

101

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

102

Biofilm diatom community structure: influence of temporal and substratum variability.  

PubMed

Diatoms, which are early autotrophic colonisers, are an important constituent of the biofouling community in the marine environment. The effects of substratum and temporal variations on the fouling diatom community structure in a monsoon-influenced tropical estuary were studied. Fibreglass and glass coupons were exposed every month for a period of 4 days and the diatom population sampled at 24 h intervals, over a period of 14 months. The planktonic diatom community structure differed from the biofilm community. Pennate diatoms dominated the biofilms whilst centric diatoms were dominant in the water column. Among the biofilm diatoms, species belonging to the genera Navicula, Amphora, Nitzschia, Pleurosigma and Thalassionema were dominant. On certain occasions, the influence of planktonic blooms was also seen on the biofilm community. A comparative study of biofilms formed on the two substrata revealed significant differences in density and diversity. However species composition was almost constant. In addition to substratum variations, the biofilm diatom community structure also showed significant seasonal variations, which were attributed to physico-chemical and biological changes in both the water and substratum. Temporal variations in the tychopelagic diatoms of the water were also observed to exert an influence on the biofilm diatom community. Variations in diatom communities may determine the functional ecosystem of the benthic environment. PMID:16371339

Patil, Jagadish S; Anil, Arga Chandrashekar

2005-01-01

103

Diatoms and pH Reconstruction  

NASA Astrophysics Data System (ADS)

Palaeolimnological diatom data comprise counts of many species expressed as percentages for each sample. Reconstruction of past lake-water pH from such data involves two steps; (i) regression, where responses of modern diatom abundances to pH are modelled and (ii) calibration where the modelled responses are used to infer pH from diatom assemblages preserved in lake sediments. In view of the highly multivariate nature of diatom data, the strongly nonlinear response of diatoms to pH, and the abundance of zero values in the data, a compromise between ecological realism and computational feasability is essential. The two numerical approaches used are (i) the computationally demanding but formal statistical approach of maximum likelihood (ML) Gaussian logit regression and calibration and (ii) the computationally straightforward but heuristic approach of weighted averaging (WA) regression and calibration. When the Surface Water Acidification Project (SWAP) modern training set of 178 lakes is reduced by data-screening to 167 lakes, WA gives superior results in terms of lowest root mean squared errors of prediction in cross-validation. Bootstrapping is also used to derive prediction errors, not only for the training set as a whole but also for individual pH reconstructions by WA for stratigraphic samples from Round Loch of Glenhead, southwest Scotland covering the last 10 000 years. These reconstructions are evaluated in terms of lack-of-fit to pH and analogue measures and are interpreted in terms of rate of change by using bootstrapping of the reconstructed pH time-series.

Birks, H. J. B.; Line, J. M.; Juggins, S.; Stevenson, A. C.; Ter Braak, C. J. F.

1990-03-01

104

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. PMID:24623722

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

2014-01-01

105

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

106

Method of laminating structural members  

NASA Technical Reports Server (NTRS)

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

Heier, W. C. (inventor)

1974-01-01

107

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

108

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

109

Flat laminated microbial mat communities  

NASA Astrophysics Data System (ADS)

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

Franks, Jonathan; Stolz, John F.

2009-10-01

110

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

2014-01-01

111

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

112

Laminate Propellant Combustion (Review) 2. Theoretical Investigations  

Microsoft Academic Search

A review of theoretical research of the combustion of laminate propellants is given. The purpose and description of the simplification\\u000a of heterogeneous propellants through the use of constituent layers is detailed. This second of a two-part review describes:\\u000a 1) the development of knowledge of the deflagration of laminates through analytical and computational descriptions of many\\u000a different aspects of the overall

R. P. Fitzgerald; M. Q. Brewster

2006-01-01

113

Development of a laminate fatigue analysis  

NASA Technical Reports Server (NTRS)

A fatigue analysis technique developed to predict damage growth in notched laminates is described. Features of the analysis include: criteria to relate matrix failure to cyclic stresses in and between plies; correlation of delamination growth with strain-release rate; and in-plane shear modulus change is related to cyclic shear stresses. A simplified finite element model is used to determine stresses in laminates that contain matrix damage. Failure criteria are integrated with the finite element model to form the fatigue analysis.

Roderick, G. L.; Obrien, T. K.; Whitcomb, J. D.

1980-01-01

114

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

115

Effect of temperature on diatom volume, growth rate, and carbon and nitrogen content: Reconsidering some paradigms  

Microsoft Academic Search

We examined the response of diatoms to naturally experienced temperatures and tested these hypotheses: (1) diatoms follow the rule that organism size decreases with increasing temperature; (2) diatom growth rate follows a Q10-like response; (3) diatom carbon (C) and nitrogen (N) content per unit volume (V) decrease with increasing size, and changes in temperature affect this relationship; and (4) diatom

David J. S. Montagnes; Daniel J. Franklin

2008-01-01

116

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

PubMed

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

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

2008-06-24

117

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

PubMed

Lamins, members of the family of intermediate filaments, form a supportive nucleoskeletal structure underlying the nuclear envelope and can also form intranuclear structures. Mutations within the A-type lamin gene cause a variety of degenerative diseases which are collectively referred to as laminopathies. At the molecular level, laminopathies have been shown to be linked to a discontinuous localization pattern of A-type lamins, with some laminopathies containing nuclear lamin A aggregates. Since nuclear aggregate formation could lead to the mislocalization of proteins interacting with A-type lamins, we set out to examine the effects of FLAG-lamin A N195K and R386K protein aggregate formation on the subnuclear distribution of the retinoblastoma protein (pRb) and the sterol responsive element binding protein 1a (SREBP1a) after coexpression as GFP-fusion proteins in HeLa cells. We observed strong recruitment of both proteins into nuclear aggregates. Nuclear aggregate recruitment of the NPC component nucleoporin NUP153 was also observed and found to be dependent on the N-terminus. That these effects were specific was implied by the fact that a number of other coexpressed karyophilic GFP-fusion proteins, such as the nucleoporin NUP98 and kanadaptin, did not coaggregate with FLAG-lamin A N195K or R386K. Immunofluorescence analysis further indicated that the precursor form of lamin A, pre-lamin A, could be found in intranuclear aggregates. Our results imply that redistribution into lamin A-/pre-lamin A-containing aggregates of proteins such as pRb and SREBP1a could represent a key aspect underlying the molecular pathogenesis of certain laminopathies. PMID:16289535

Hübner, S; Eam, J E; Hübner, A; Jans, D A

2006-01-15

118

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

SciTech Connect

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

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

2006-01-15

119

Universal Reduced Potential Function for Diatomic Systems  

SciTech Connect

The potential energy functions of 200 diatomic systems, with dissociation energies D{sub e} ranging from few eV to hundreds of {mu}eV, are well described by a new three-parameter potential energy function. Identification of the evaluated values of a dimensionless quantity, {xi}{sub n}=(L{sub 2}/L{sub n}) [L{sub n}=((n{exclamation_point}D{sub e}/f{sub n})){sup 1/n}, a scaled length parameter, and f{sub n}, the nth force constant evaluated at the equilibrium internuclear distance R{sub e}], is proposed as a reliable criterion to search for the universal scaling features of potentials and spectroscopic constants for bound diatomic systems. Our study suggests a useful approach to predicting future molecular spectroscopic constants.

Xie Ruihua [Department of Physics and Key Laboratory of Ferroelectric Materials and Devices of Hubei Province, Hubei University, Wuhan 430062 (China); Institute for Quantum Studies and Department of Physics, Texas A and M University, College Station, Texas 77843 (United States); Department of Chemistry, Emory University, Atlanta, Georgia 30322 (United States); Hsu, Paul S. [Institute for Quantum Studies and Department of Physics, Texas A and M University, College Station, Texas 77843 (United States)

2006-06-23

120

Generalized diatomics-in-molecules theory  

Microsoft Academic Search

A three-dimensional potential surface for the H3 system accurately fitted to the ab initio points of Liu and Siegbahn is reported. In this fit the physical model is a valence bond description based on two canonical structures, the complete mathematical framework is that of the generalized diatomics-in-molecules (GDIM) theory with zero differential overlap approximation, and the fitting function is a

Ay-Ju A. Wu

1981-01-01

121

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

122

Multiphoton Processes in Homopolar Diatomic Molecules  

Microsoft Academic Search

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

F. V. Bunkin; I. I. Tugov

1973-01-01

123

Photoacclimation in the marine diatom Skeletonema costatum  

Microsoft Academic Search

Photoacclimation was examined in the marine diatom Skeletonema costatum, which was subjected to reciprocal shifts between irradiances of 50 (low-light) and 1,200 (high-light) mmol photons m 22 s 21 . Cell chlorophyll a and fucoxanthin contents were higher but diadinoxanthin and diatoxanthin contents lower in cells grown at 50 mmol photons m 22 s 21 than in cells shifted to

Tracy Anning; Hugh L. MacIntyre; Sandra M. Pratt; Pippa J. Sammes; Stuart Gibb; Richard J. Geider

2000-01-01

124

Previously Unknown Virus Infects Marine Diatom  

PubMed Central

Diatoms are a major phytoplankton group that play important roles in maintaining oxygen levels in the atmosphere and sustaining the primary nutritional production of the aquatic environment. Among diatoms, the genus Chaetoceros is one of the most abundant and widespread. Temperature, climate, salinity, nutrients, and predators were regarded as important factors controlling the abundance and population dynamics of diatoms. Here we show that a viral infection can occur in the genus Chaetoceros and should therefore be considered as a potential mortality source. Chaetoceros salsugineum nuclear inclusion virus (CsNIV) is a 38-nm icosahedral virus that replicates within the nucleus of C. salsugineum. The latent period was estimated to be between 12 and 24 h, with a burst size of 325 infectious units per host cell. CsNIV has a genome structure unlike that of other viruses that have been described. It consists of a single molecule of covalently closed circular single-stranded DNA (ssDNA; 6,005 nucleotides), as well as a segment of linear ssDNA (997 nucleotides). The linear segment is complementary to a portion of the closed circle creating a partially double-stranded genome. Sequence analysis reveals a low but significant similarity to the replicase of circoviruses that have a covalently closed circular ssDNA genome. This new host-virus system will be useful for investigating the ecological relationships between bloom-forming diatoms and other viruses in the marine system. Our study supports the view that, given the diversity and abundance of plankton, the ocean is a treasury of undiscovered viruses. PMID:16000758

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

2005-01-01

125

Star Trek replicators and diatom nanotechnology  

Microsoft Academic Search

Diatoms are single celled algae, the 105–106 species of which create a wide variety of three-dimensional amorphous silica shells. If we could get them to produce useful structures, perhaps by compustat selection experiments (i.e. forced evolution of development or evodevo), their exponential growth in suspension cultures could compete with the lithography techniques of present day nanotechnology, which have limited 3D

Ryan W. Drum; Richard Gordon

2003-01-01

126

Collecting, Cleaning, Mounting, and Photographing Diatoms  

Microsoft Academic Search

\\u000a This chapter describes techniques used by diatomists to clean and mount diatoms successfully. The techniques involve the use\\u000a of extremely hazardous chemicals that are a serious threat to one’s health and physical safety, including strong mineral acids\\u000a that can cause severe skin burns or blindness after brief contact with the skin or eyes; sodium hydroxide, a strong base which\\u000a can

Stephen S. Nagy

127

Silicon diatom frustules as nanostructured photoelectrodes.  

PubMed

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

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

2014-09-18

128

Molecular Tools for Discovering the Secrets of Diatoms  

NSDL National Science Digital Library

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

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

2009-10-01

129

Laminating rule for predicting the dielectric properties of E-glass\\/epoxy laminate composite  

Microsoft Academic Search

Since the electromagnetic properties of fiber reinforced polymeric laminate composite can be tailored effectively by adjusting its composition and regulating the stacking sequence, it is plausible material for fabricating the radar absorbing structures (RAS) of desired performance. In order to design the effective electromagnetic wave (EM) absorber with the fiber reinforced polymeric laminate composite, its electromagnetic characteristics should be available

Woo Seok Chin; Dai Gil Lee

2007-01-01

130

Diatomics-in-molecules treatment of NH3  

Microsoft Academic Search

The diatomics-in-molecules method is applied to calculate the ground state potential-energy surface of NH3 by using both the selection of atomic states and the diatomic input data previously employed in a successful DIM description of the low-lying valence states of NH3. It appears that the diatomic information is transferable from one DIM model to the other one only in a

R. Polák; J. Vojtík

1989-01-01

131

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

132

Lamination residual stresses in fiber composites  

NASA Technical Reports Server (NTRS)

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

Daniel, I. M.; Liber, T.

1975-01-01

133

Mechanical Behavior of Fabric-Film Laminates  

NASA Technical Reports Server (NTRS)

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

Said, Magdi S.

1999-01-01

134

Diatom community structure on in-service cruise ship hulls.  

PubMed

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

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

2014-10-01

135

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

Microsoft Academic Search

Taphonomic issues pose fundamental challenges for Quaternary scientists to recover environmental signals from biological proxies and make accurate inferences of past environments. The problem of microfossil preservation, specifically diatom dissolution, remains an important, but often overlooked, source of error in both qualitative and quantitative reconstructions of key variables from fossil samples, especially those using relative abundance data. A first step

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

2009-01-01

136

Semitransparent Organic Photovoltaic Cells with Laminated Top Electrode  

E-print Network

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

Cui, Yi

137

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

138

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

139

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

140

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

141

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

142

Diatomic sulfur (S/sub 2/)  

SciTech Connect

Recently, they described a group 14 metal assisted procedure for the preparation and Diels-Alder trapping of S/sub 2/, a highly reactive diatomic form of elemental sulfur. Their continuing efforts in this area have led us to develop an alternate synthetic method that affords this reactive dienophile by, to their knowledge, an unprecedented intramolecular carbon-carbon bond-forming reaction. The ability to generate S/sub 2/ conveniently, and at temperatures more conductive to Diels-Alder trapping, makes it synthetically attractive to use. The present procedure should therefore, find widespread application in the synthesis of 1,2-dithiins.

Steliou, K.; Salama, P.; Brodeur, D.; Gareau, Y.

1987-02-04

143

Buckling analyses of composite laminate skew plates with material nonlinearity  

Microsoft Academic Search

A nonlinear material constitutive model, including a nonlinear in-plane shear formulation and the Tsai–Wu failure criterion, for fiber–composite laminate materials is employed to carry out finite element buckling analyses for composite laminate skew plates under uniaxial compressive loads. The influences of laminate layup, plate skew angle and plate aspect ratio on the buckling resistance of composite laminate skew plates are

Hsuan-Teh Hu; Chia-Hao Yang; Fu-Ming Lin

2006-01-01

144

Diatoms respire nitrate to survive dark and anoxic conditions  

PubMed Central

Diatoms survive in dark, anoxic sediment layers for months to decades. Our investigation reveals a correlation between the dark survival potential of marine diatoms and their ability to accumulate NO3? intracellularly. Axenic strains of benthic and pelagic diatoms that stored 11–274 mM NO3? in their cells survived for 6–28 wk. After sudden shifts to dark, anoxic conditions, the benthic diatom Amphora coffeaeformis consumed 84–87% of its intracellular NO3? pool within 1 d. A stable-isotope labeling experiment proved that 15NO3? consumption was accompanied by the production and release of 15NH4+, indicating dissimilatory nitrate reduction to ammonium (DNRA). DNRA is an anaerobic respiration process that is known mainly from prokaryotic organisms, and here shown as dissimilatory nitrate reduction pathway used by a eukaryotic phototroph. Similar to large sulfur bacteria and benthic foraminifera, diatoms may respire intracellular NO3? in sediment layers without O2 and NO3?. The rapid depletion of the intracellular NO3? storage, however, implies that diatoms use DNRA to enter a resting stage for long-term survival. Assuming that pelagic diatoms are also capable of DNRA, senescing diatoms that sink through oxygen-deficient water layers may be a significant NH4+ source for anammox, the prevalent nitrogen loss pathway of oceanic oxygen minimum zones. PMID:21402908

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

2011-01-01

145

Diatom distribution and status of organic pollution in sewage drains  

Microsoft Academic Search

Data on the limnology of various sewage drains meeting the River Yamuna in Delhi suggest that diatom distribution, seasonal\\u000a and total, and concentration of nitrate nitrogen vary with the degree of organic pollution. The significance of such a relationship\\u000a for identifying certain diatoms as water quality indicators is discussed.

K. M. M. Dakshini; J. K. Soni

1982-01-01

146

Tracking the sterol biosynthesis pathway of the diatom Phaeodactylum tricornutum.  

PubMed

Diatoms are unicellular photosynthetic microalgae that play a major role in global primary production and aquatic biogeochemical cycling. Endosymbiotic events and recurrent gene transfers uniquely shaped the genome of diatoms, which contains features from several domains of life. The biosynthesis pathways of sterols, essential compounds in all eukaryotic cells, and many of the enzymes involved are evolutionarily conserved in eukaryotes. Although well characterized in most eukaryotes, the pathway leading to sterol biosynthesis in diatoms has remained hitherto unidentified. Through the DiatomCyc database we reconstructed the mevalonate and sterol biosynthetic pathways of the model diatom Phaeodactylum tricornutum in silico. We experimentally verified the predicted pathways using enzyme inhibitor, gene silencing and heterologous gene expression approaches. Our analysis revealed a peculiar, chimeric organization of the diatom sterol biosynthesis pathway, which possesses features of both plant and fungal pathways. Strikingly, it lacks a conventional squalene epoxidase and utilizes an extended oxidosqualene cyclase and a multifunctional isopentenyl diphosphate isomerase/squalene synthase enzyme. The reconstruction of the P. tricornutum sterol pathway underscores the metabolic plasticity of diatoms and offers important insights for the engineering of diatoms for sustainable production of biofuels and high-value chemicals. PMID:24996048

Fabris, Michele; Matthijs, Michiel; Carbonelle, Sophie; Moses, Tessa; Pollier, Jacob; Dasseville, Renaat; Baart, Gino J E; Vyverman, Wim; Goossens, Alain

2014-11-01

147

Enhanced photosynthetic assimilation ratios in Antarctic Polar Front (convergence) diatoms  

Microsoft Academic Search

Diatom populations from the Antarctic Polar Front (convergence) in the Drake Passage area exhibited relatively high photosynthesis : chlorophyll a ratios at light saturation. The permanent water column instability and the adverse meteorological conditions observed in the central Drake Passage area seem to product a light-color stress on the physiology of convergence diatoms that are restricted to a blue-green light

ENRIQUE F. MANDELLI

1967-01-01

148

ORIGINAL PAPER Seasonal progression of diatom assemblages in surface waters  

E-print Network

Diatoms Á Phytoplankton Á Seasonality Á Sea-ice Á Coastal Antarctic Á Proboscia inermis IntroductionORIGINAL PAPER Seasonal progression of diatom assemblages in surface waters of Ryder Bay and environmental conditions with algal speciation. Typical of near-shore Antarctic waters, biomass was dominated

149

Diatom frustules as light traps enhance DSSC efficiency.  

PubMed

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

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

2013-02-01

150

The Central Carbon and Energy Metabolism of Marine Diatoms  

PubMed Central

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

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

2013-01-01

151

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

EPA Science Inventory

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

152

Diatoms in forensic expertise of drowning—a Macedonian experience  

Microsoft Academic Search

Results obtained by examination of 22 human cases suspected for drowning, one human case of death other than drowning and several tests on laboratory rats were used as a basis for evaluation of diatom method as supportive in forensic expertise of drowning. The recovery of diatoms from various examined organs, their qualitative and quantitative composition, if properly treated without the

Svetislav Krstic; Aleksej Duma; Biljana Janevska; Zlatko Levkov; Ksenija Nikolova; Marina Noveska

2002-01-01

153

PALAEOENVIRONMENT AND ARCHAEOLOGY: THE USE OF DIATOM ANALYSIS IN ARCHAEOLOGY  

Microsoft Academic Search

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. The assemblages are usually diverse and therefore contain considerable ecological information. For this reason, and because it is easy to obtain large numbers of individuals, robust statistical and multivariate

Nadja Ognjanova-Rumenova

2008-01-01

154

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

155

Copepod hatching success in marine ecosystems with high diatom concentrations.  

PubMed

Diatoms dominate spring bloom phytoplankton assemblages in temperate waters and coastal upwelling regions of the global ocean. Copepods usually dominate the zooplankton in these regions and are the prey of many larval fish species. Recent laboratory studies suggest that diatoms may have a deleterious effect on the success of copepod egg hatching. These findings challenge the classical view of marine food-web energy flow from diatoms to fish by means of copepods. Egg mortality is an important factor in copepod population dynamics, thus, if diatoms have a deleterious in situ effect, paradoxically, high diatom abundance could limit secondary production. Therefore, the current understanding of energy transfer from primary production to fisheries in some of the most productive and economically important marine ecosystems may be seriously flawed. Here we present in situ estimates of copepod egg hatching success from twelve globally distributed areas, where diatoms dominate the phytoplankton assemblage. We did not observe a negative relationship between copepod egg hatching success and either diatom biomass or dominance in the microplankton in any of these regions. The classical model for diatom-dominated system remains valid. PMID:12353032

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

2002-09-26

156

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

157

ORIGINAL PAPER A caveat regarding diatom-inferred nitrogen concentrations  

E-print Network

in diatom community structure. The lake- water concentrations of nitrate that cause these community changes in quantifying surface- water concentrations of nitrate that elicit ecological change in order to implement remain unclear, raising interest in the development of diatom-based transfer functions to infer nitrate

158

Lake warming favours small-sized planktonic diatom species  

PubMed Central

Diatoms contribute to a substantial portion of primary production in the oceans and many lakes. Owing to their relatively heavy cell walls and high nutrient requirements, planktonic diatoms are expected to decrease with climate warming because of reduced nutrient redistribution and increasing sinking velocities. Using a historical dataset, this study shows that diatoms were able to maintain their biovolume with increasing stratification in Lake Tahoe over the last decades; however, the diatom community structure changed. Increased stratification and reduced nitrogen to phosphorus ratios selected for small-celled diatoms, particularly within the Cyclotella genus. An empirical model showed that a shift in phytoplankton species composition and cell size was consistent within different depth strata, indicating that altered nutrient concentrations were not responsible for the change. The increase in small-celled species was sufficient to decrease the average diatom size and thus sinking velocity, which strongly influences energy transfer through the food web and carbon cycling. Our results show that within the diverse group of diatoms, small-sized species with a high surface area to volume ratio were able to adapt to a decrease in mixing intensity, supporting the hypotheses that abiotic drivers affect the size structure of planktonic communities and that warmer climate favours small-sized diatom cells. PMID:18812287

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

2008-01-01

159

The central carbon and energy metabolism of marine diatoms.  

PubMed

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

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

2013-01-01

160

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

161

Benthic diatoms in lakes: environmental drivers and ecological  

E-print Network

Sueciae 2014:47 ISSN 1652-6880 ISBN (print version) 978-91-576-8042-6 ISBN (electronic version) 978 diatom guilds seems to be decoupled from nutrient availability in acidic compared to high pH aquatic producers, especially diatoms, displayed a stronger response to pH than macro- invertebrates, possibly due

162

Paleoenvironmental inference models from sediment diatom assemblages in Baffin Island  

E-print Network

Paleoenvironmental inference models from sediment diatom assemblages in Baffin Island lakes Abstract: Diatoms from the surface sediments of 61 lakes on Baffin Island, Nunavut, were identified Introduction The Canadian Arctic Archipelago, of which Baffin Island represents the largest landmass (507 450

Wolfe, Alexander P.

163

Composite laminate free edge reinforcement concepts  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

164

A study of delamination buckling of laminates  

NASA Technical Reports Server (NTRS)

The subject of this paper is the buckling of laminated plates, with a preexisting delamination, subjected to in-plane loading. Each laminate is modelled as an orthotropic Mindlin plate. The analysis is carried out by a combination of the finite element and asymptotic expansion methods. By applying the finite element method, plates with general delamination regions can be studied. The asymptotic expansion method reduces the number of unknown variables of the eigenvalue equation to that of the equation for a single Kirchhoff plate. Numerical results are presented for several examples. The effects of the shape, size, and position of the delamination on the buckling load are studied through these examples.

Mukherjee, Yu-Xie; Xie, Zhi-Cheng; Ingraffea, Anthony

1990-01-01

165

Energy Saving Glass Lamination via Selective Radio Frequency Heating  

SciTech Connect

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

Allan, Shawn M.

2012-02-27

166

Energy Saving Glass Lamination via Selective Radio Frequency Heating  

SciTech Connect

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

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

2012-02-27

167

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

168

Integration of TiO2 into the diatom Thalassiosira weissflogii during frustule synthesis  

PubMed Central

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

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

2013-01-01

169

Controlling Performance of Laminated Composites Using Piezoelectric Materials  

E-print Network

-electro-elastic constitutive model for transversely isotropic materials is used for each ply in the composite laminates. The first-ply failure and ultimate laminate failure criteria of composite laminates are used to predict the failure stress and mode of the composite...

Hasan, Zeaid

2012-02-14

170

Best Strip-Beam Properties Derivable from Classical Lamination Theory  

E-print Network

Best Strip-Beam Properties Derivable from Classical Lamination Theory Wenbin Yu Utah State strips from an asymptotically correct classical lamination theory derived using the variational Introduction Classical lamination theory (CLT) of plates is suitable for modeling of thin, isotropic plates

Yu, Wenbin

171

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

172

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

173

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

E-print Network

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

174

Reciprocal knock-in mice to investigate the functional redundancy of lamin B1 and lamin B2  

PubMed Central

Lamins B1 and B2 (B-type lamins) have very similar sequences and are expressed ubiquitously. In addition, both Lmnb1- and Lmnb2-deficient mice die soon after birth with neuronal layering abnormalities in the cerebral cortex, a consequence of defective neuronal migration. The similarities in amino acid sequences, expression patterns, and knockout phenotypes raise the question of whether the two proteins have redundant functions. To investigate this topic, we generated “reciprocal knock-in mice”—mice that make lamin B2 from the Lmnb1 locus (Lmnb1B2/B2) and mice that make lamin B1 from the Lmnb2 locus (Lmnb2B1/B1). Lmnb1B2/B2 mice produced increased amounts of lamin B2 but no lamin B1; they died soon after birth with neuronal layering abnormalities in the cerebral cortex. However, the defects in Lmnb1B2/B2 mice were less severe than those in Lmnb1-knockout mice, indicating that increased amounts of lamin B2 partially ameliorate the abnormalities associated with lamin B1 deficiency. Similarly, increased amounts of lamin B1 in Lmnb2B1/B1 mice did not prevent the neurodevelopmental defects elicited by lamin B2 deficiency. We conclude that lamins B1 and B2 have unique roles in the developing brain and that increased production of one B-type lamin does not fully complement loss of the other. PMID:24672053

Lee, John M.; Tu, Yiping; Tatar, Angelica; Wu, Daniel; Nobumori, Chika; Jung, Hea-Jin; Yoshinaga, Yuko; Coffinier, Catherine; de Jong, Pieter J.; Fong, Loren G.; Young, Stephen G.

2014-01-01

175

Optimal design of pitched laminated wood beams  

Microsoft Academic Search

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

M. Avriel; J. D. Barrett

1978-01-01

176

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

177

Fabrication of CFRP\\/Al Active Laminates  

Microsoft Academic Search

This paper describes fabrication and evaluation of the active laminate. It was made by hot-pressing of an aluminum plate as a high CTE material, a unidirectional CFRP prepreg as a low CTE material and an electric resistance heater, a KFRP prepreg as a low CTE material and an insulator between them, and copper foils as electrodes. In this study, fabricating

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

2003-01-01

178

Micro-Cracking Detection in Laminated Composites  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

179

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

180

Computational modeling of failure in composite laminates  

Microsoft Academic Search

There is no state of the art computational model that is good enough for predictive simulation of the complete failure process in laminates. Already on the single ply level controversy exists. Much work has been done in recent years in the development of continuum models, but these fail to predict the correct failure mechanism in cases where matrix cracking in

F. P. Van der Meer

2010-01-01

181

Theory of laminated turbulence: open questions  

E-print Network

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

E. Kartashova

2006-07-30

182

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

183

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

184

HYGROTHERMAL AGING OF POLYIMIDE MATRIX COMPOSITE LAMINATES  

E-print Network

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

Nairn, John A.

185

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

186

Edge effects in angle-ply composite laminates  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

187

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

188

Determining Shear Stress Distribution in a Laminate  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

189

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

190

Oceanographic control of biogenic opal and diatoms in surface sediments of the Southwestern Atlantic  

Microsoft Academic Search

Based on 66 surface sediment samples collected in the SW Atlantic Ocean between 27 and 50°S, this study presents an overview of the spatial distribution of biogenic opal and diatom concentrations, and diatom assemblages. Biogenic opal has highest values in the deepest, pelagic stations and decreases toward the slope. Diatoms closely follow the spatial trend of opal. Diatom assemblages reflect

O Romero; C Hensen

2002-01-01

191

control of biogenic opal and diatoms in surface sediments of the Southwestern Atlantic  

Microsoft Academic Search

Based on 66 surface sediment samples collected in the SW Atlantic Ocean between 27 and 50‡S, this study presents an overview of the spatial distribution of biogenic opal and diatom concentrations, and diatom assemblages. Biogenic opal has highest values in the deepest, pelagic stations and decreases toward the slope. Diatoms closely follow the spatial trend of opal. Diatom assemblages reflect

O. Romero; C. Hensen

192

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

Microsoft Academic Search

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

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

2010-01-01

193

Diatom-based label-free optical biosensor for biomolecules.  

PubMed

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

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

2014-10-01

194

Diatom assemblages promote ice formation in large lakes  

PubMed Central

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

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

2013-01-01

195

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

196

Copepod Population-Specific Response to a Toxic Diatom Diet  

PubMed Central

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

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

2012-01-01

197

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

NASA Astrophysics Data System (ADS)

We examine the capacity of nematodes from three feeding types (deposit feeder, epistrate feeder, predator) to utilize microphytobenthos (MPB), and assess whether diatom cell size and consumer body size are important drivers of their feeding. We analyzed natural stable isotope ratios of carbon and nitrogen in abundant nematode genera and a variety of carbon sources at an estuarine intertidal flat. All nematodes had ?13C indicating that MPB is their major carbon source. ?15N, however, demonstrated that only one deposit and one epistrate feeder genus obtained most of their carbon from direct grazing on MPB, whereas other deposit feeders and predators obtained at least part of their carbon by predation on MPB grazers. We then performed a microcosm experiment in which equal cell numbers of each of three differently sized strains of the pennate diatom Seminavis were offered as food to four, one and one genera of deposit feeders, epistrate feeders and predators, respectively. Previous studies have shown that all but the epistrate feeder ingest whole diatoms, whereas the epistrate feeder pierces cells and sucks out their contents. Most genera showed markedly higher carbon absorption from medium and large cells than from small ones. When considering the number of cells consumed, however, none of the nematodes which ingest whole cells exhibited a clear preference for any specific diatom size. The epistrate feeder was the smallest nematode taxon considered here, yet it showed a marked preference for large cells. These results highlight that the feeding mechanism is much more important than consumer size as a driver of particle size selection in nematodes grazing MPB.

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

2014-09-01

198

Failure determination for a laminated composite plate with a circular hole  

E-print Network

of Unidirectional Graphite/Epoxy Laminate 23 Stiffness and Compliance Matrices for Laminate 24 Roots of Characteristic Equation Maximum Stress Concentrations 46 Maximum Laminate Stress Concentrations Crack Initiation Stress 47 Laminate Strain Energy Release... Rates (no hole) Laminate Strain Energy Release Rates (with hole) Gc for Sinqle Ply in Laminate With Hole 10 Location of Maximum Stress Concentrations and Fracture Points 50 I. I ST OF FIGURES FIGURE PAGE Principal Coordinate Systems Laminate...

Ko, Chi-Ren Clarence

2012-06-07

199

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

200

An aqueous route to organically functionalized silica diatom skeletons  

NASA Astrophysics Data System (ADS)

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

Fowler, Christabel E.; Buchber, Catherine; Lebeau, Bénédicte; Patarin, Joël; Delacôte, Cyril; Walcarius, Alain

2007-04-01

201

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

202

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

203

Genomic footprints of a cryptic plastid endosymbiosis in diatoms.  

PubMed

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

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

2009-06-26

204

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

205

Interface stresses in laminated cylindrical shells  

SciTech Connect

A theory is established by treating each layer of a laminated cylindrical shell as a separate thin shell with the interface stresses as unknown loading parameters. Equilibrium equations are satisfied exactly. Other elasticity equations are assumed to be approximately satisfied or satisfied on the average through the thickness of each layer. By satisfying continuity in displacement at each interface and the traction boundary conditions at inner and outer boundary surfaces, the interface stresses are determined systematically without limitation of the number of layers of the shell. Present results show excellent agreements with the exact solution for homogeneous isotropic thick cylinders. Results are presented for the basic problem of double layered shells which may be used as bench mark solutions for future reference. Numerical examples for laminated cylinders consisting of layers of orthotropic materials are presented for illustrative purposes.

Wang, J.T.S.; Lin, C.C. [National Chung-Hsing Univ., Taichung (Taiwan, Province of China). Institute of Applied Mathematics

1993-12-31

206

Fabrication of CFRP/Al Active Laminates  

NASA Astrophysics Data System (ADS)

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

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

207

Investigating Delamination Migration in Composite Tape Laminates  

NASA Technical Reports Server (NTRS)

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

Ratcliffe, James G.; DeCarvalho, Nelson V.

2014-01-01

208

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

209

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

210

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

211

Hypervelocity impact on laminate composite panels  

Microsoft Academic Search

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

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

1995-01-01

212

Analysis of fatigue damage in composite laminates  

NASA Technical Reports Server (NTRS)

An attempt is made to give a comprehensive characterization of processes of degradation in type 1 and 2 laminated composites under cyclic (fatigue) loading; based on the discovery of a 'characteristic damage state' that forms independently of load history and is determined by laminae properties, orientation and stacking sequence alone. The detailed nature of this state, its formation and its influence on strength, life and stiffness, is discussed.

Reifsnider, K. L.; Talug, A.

1980-01-01

213

Micromechanical modeling of composite plies and laminates  

Microsoft Academic Search

After, fabrication or in service, certain metal and ceramic matrix laminates may exhibit extensive de-cohesion, such as de-bonding and sliding at fiber-matrix interfaces. The de-cohesion induced changes on overall response and on redistribution of local stress and deformation fields is analyzed here. A finite element analysis of an unit cell model of a fibrous ply is used to obtain energy

Mullahalli V. Srinivas

1997-01-01

214

Simulation of Progressive Failure in Composite Laminates  

Microsoft Academic Search

Fiber reinforced polymers are materials with excellent mechanical properties and relativelymuch design freedom.However, because\\u000a complex failuremechanisms originating from the microstructure of the material may occur, realistic simulation of the failure\\u000a process is still a challenge. Two alternative models for the modeling of failure in composite laminates are presented. The\\u000a first is a continuum damage model that is supposed to cover

F. P. van der Meer; L. J. Sluys

215

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

216

Generalized diatomics-in-molecule method for polyatomics  

Microsoft Academic Search

A new derivation of the generalized diatomics-in-molecule (GDIM) method for the description of electronically stationary and quasi-stationary states of a polyatomic molecule is given in the partial-wave representation of the electron continuum. The method is based on the combination of the projection-operator approach of scattering theory with the diatomics-in-molecule fragmentation of the fixed-nuclei Hamiltonian, resulting in the construction of diabatic

A. K. Belyaev; A. S. Tiukanov; W. Domcke

2009-01-01

217

Generalized diatomics-in-molecules method for polyatomic anions  

Microsoft Academic Search

The diatomics-in-molecules (DIM) method for the construction of polyatomic potential-energy functions from the potential energies of atomic and diatomic fragments is generalized to obtain a description of potential-energy functions of both quasistationary and bound states of polyatomic anions. The formulation is based on the combination of the DIM method with the projection-operator approach of scattering theory. The proposed theory allows

A. K. Belyaev; A. S. Tiukanov; W. Domcke

2002-01-01

218

Diatom frustule photonic crystal geometric and optical characterization  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

219

Seasonal Diatom Variability and Paleolimnological Inferences – A Case Study  

Microsoft Academic Search

The seasonality of physical, chemical, and biological water variables is a major characteristic of temperate, dimictic lakes.\\u000a Yet, few investigations have considered the potential information that is encoded in seasonal dynamics with respect to the\\u000a paleolimnological record. We used a one-year sequence of diatoms obtained from sediment traps and water samples, as well as\\u000a the sedimentary diatom record covering the

Dörte Köster; Reinhard Pienitz

2006-01-01

220

Opening the gateways for diatoms primes Earth for Antarctic glaciation  

NASA Astrophysics Data System (ADS)

The abrupt onset of Antarctic glaciation during the Eocene-Oligocene Transition (?33.7 Ma, Oi1) is linked to declining atmospheric pCO2 levels, yet the mechanisms that forced pCO2 decline remain elusive. Biogenic silicon cycling is inextricably linked to both long and short term carbon cycling through the diatoms, siliceous walled autotrophs which today account for up to 40% of primary production. It is hypothesised that during the Late Eocene a sharp rise in diatom abundance could have contributed to pCO2 drawdown and global cooling by increasing the proportion of organic carbon buried in marine sediment. Diatom and sponge silicon isotope ratios (?30Si) are here combined for the first time to reconstruct the late Eocene-early Oligocene ocean silicon cycle and provide new insight into the role of diatom productivity in Antarctic glaciation. At ODP site 1090 in the Southern Ocean, a 0.6‰ rise in diatom ?30Si through the late Eocene documents increasing diatom silicic acid utilisation with high, near modern values attained by the earliest Oligocene. A concomitant 1.5‰ decline in sponge ?30Si at ODP site 689 on the Maud Rise tracks an approximate doubling of intermediate depth silicic acid concentration in the high southern latitudes. Intermediate depth silicic acid concentration peaked at ?31.5 Ma, coincident with the final establishment of a deepwater pathway through the Tasman Gateway and Drake Passage. These results suggest that upwelling intensification related to the spin-up of a circum-Antarctic current may have driven late Eocene diatom proliferation. Organic carbon burial associated with higher diatom abundance and export provides a mechanism that can account for pCO2 drawdown not only at, but also prior to, Antarctic glaciation as required by a pCO2 ‘threshold’ mechanism for ice sheet growth.

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

2013-08-01

221

Modeling Composite Laminate Crushing for Crash Analysis  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

222

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

223

Vibration analysis of bimodulus laminated cylindrical panels  

NASA Astrophysics Data System (ADS)

This paper deals with the flexural vibration behavior of bimodular laminated composite cylindrical panels with various boundary conditions. The formulation is based on first order shear deformation theory and Bert's constitutive model. The governing equations are derived using finite element method and Lagrange's equation of motion. An iterative eigenvalue approach is employed to obtain the positive and negative half cycle free vibration frequencies and corresponding mode shapes. A detailed parametric study is carried out to study the influences of thickness ratio, aspect ratio, lamination scheme, edge conditions and bimodularity ratio on the free vibration characteristics of bimodulus angle- and cross-ply composite laminated cylindrical panels. It is interesting to observe that there is a significant difference between the frequencies of positive and negative half cycles depending on the panel parameters. Through the thickness distribution of modal stresses for positive half cycle is significantly different from that for negative half cycle unlike unimodular case wherein the stresses at a particular location in negative half cycle would be of same magnitude but of opposite sign of those corresponding to positive half cycle. Finally, the effect of bimodularity on the steady state response versus forcing frequency relation is studied for a typical case.

Khan, K.; Patel, B. P.; Nath, Y.

2009-03-01

224

Molecular identification of sequestered diatom chloroplasts and kleptoplastidy in foraminifera.  

PubMed

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

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

2011-07-01

225

Environmental factors influencing diatom communities in Antarctic cryoconite holes  

NASA Astrophysics Data System (ADS)

Cryoconite holes are ice-bound habitats that can act as refuges for aquatic and terrestrial microorganisms on glacier surfaces. In the McMurdo Dry Valleys of Antarctica, these holes are often capped by an ice lid that prevents the exchange of material and gases with the surrounding atmosphere and aquatic environment. Diatoms have been documented in cryoconite holes, and recent findings suggest that these habitats may harbour a distinctive diatom flora compared to the surrounding aquatic environments. In this study, we examined diatom community composition in cryoconite holes and environmental correlates across three glaciers in Taylor Valley, Antarctica. The diatom communities were dominated by two genera, Muelleria and Diadesmis, both of which had high viability and could have been seeded from the surrounding ephemeral streams. The location of the cryoconite hole within the valley was a key determinant of community composition. A diatom species richness gradient was observed that corresponded to distance inland from the coast and co-varied with species richness in streams within the same lake basin. Cryoconite holes that were adjacent to streams with higher diversity displayed greater species richness. However, physical factors, such as the ability to withstand freeze-thaw conditions and to colonize coarse sediments, acted as additional selective filters and influenced diatom diversity, viability and community composition.

Stanish, L. F.; Bagshaw, E. A.; McKnight, D. M.; Fountain, A. G.; Tranter, M.

2013-12-01

226

Role of diatoms in regulating the ocean's silicon cycle  

NASA Astrophysics Data System (ADS)

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

Yool, Andrew; Tyrrell, Toby

2003-12-01

227

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. PMID:24113585

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

2013-01-01

228

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

229

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

230

A continuum model for damage evolution in laminated composites  

NASA Technical Reports Server (NTRS)

The accumulation of matrix cracking is examined using continuum damage mechanics lamination theory. A phenomenologically based damage evolutionary relationship is proposed for matrix cracking in continuous fiber reinforced laminated composites. The use of material dependent properties and damage dependent laminate averaged ply stresses in this evolutionary relationship permits its application independently of the laminate stacking sequence. Several load histories are applied to crossply laminates using this model, and the results are compared to published experimental data. The stress redistribution among the plies during the accumulation of matrix damage is also examined. It is concluded that characteristics of the stress redistribution process could assist in the analysis of the progressive failure process in laminated composites.

Lo, D. C.; Allen, D. H.; Harris, C. E.

1991-01-01

231

Molecular Fossils as Time Indicators for the Evolution of Diatoms.  

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

232

Intramolecular dependence of the frequency dependent polarizabilities of Li2(a3?+u) and van der Waals dispersion coefficients for atom-diatom and diatom-diatom alkali dimers  

NASA Astrophysics Data System (ADS)

An ab initio time dependent gauge invariant method (TDGI) has been used to compute the frequency dependent dipole and quadrupole polarizabilities of Li, Na, Li2(a3?+u) and Na2(a3?+u) and their dependence on the internuclear distance of the diatomic species. The dependence of the isotropic and anisotropic components of the static dipole polarizabilities on the diatomic distance was fitted to an analytical form which has an asymptotic form in agreement with the theoretical expression derived by Heijmen, T. G. A., Moszynski, R., Wormer, P. E. S., and van der Avoird, A., Molec. Phys., 89, 81. Long range two-body C6 coefficients have been evaluated for all combinations of atom-atom, atom-homonuclear diatom and homonuclear diatom-homonuclear diatom systems in which the diatomics are in the a3?+u state. Furthermore, the C8 coefficients for the atom-atom and atom-diatom interactions and the three-body C9 coefficients for the four atom-diatom systems have been obtained. For the atom-diatom case, the dipole-induced dipole C6 coefficients have been calculated for various diatomic distances up to 15 Å. The distance dependence of their isotropic C6000 and anisotropic C6202 components has been fitted to an analytical form similar to that used for the static dipole polarizabilities of the diatomics.

Rérat, Michel; Bussery-Honvault, Béatrice

233

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

Microsoft Academic Search

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

E. Paasche

1973-01-01

234

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

235

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

236

A shear deformation model for transverse cracking in composite laminates  

Microsoft Academic Search

Transverse cracking is often the earliest failure mode of composite laminates with off axis plies. In this article, a shear deformation model for the stress analysis of symmetric laminates with centrally located 90-deg plies subjected to transverse cracking is presented. Axial stiffness reduction predictions are compared with test data and results from other models for (0m\\/90n)s type cross-ply laminates. The

P. Sriram; E. A. Armanios

1993-01-01

237

Tension fatigue analysis and life prediction for composite laminates  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

238

Direct actin binding to A- and B-type lamin tails and actin filament bundling by the lamin A tail  

PubMed Central

Nuclear intermediate filament networks formed by A- and B-type lamins are major components of the nucleoskeleton. Lamins have growing links to human physiology and disease including Emery-Dreifuss muscular dystrophy (EDMD), lipodystrophy, cardiomyopathy, neuropathy, cerebellar disorders and segmental accelerated ‘aging’ syndromes. How lamins interact with other nucleoskeletal components, and even the identities of these other components, are open questions. Previous studies suggested lamins might bind actin. We report that the recombinant C-terminal tail domain of human A- and B-type lamins binds directly to purified actin in high-speed pelleting assays. This interaction maps to a conserved Actin Binding site (AB-1) comprising lamin A residues 461–536 in the Ig-fold domain, which are 54% identical in lamin B1. Two EDMD-causing missense mutations (R527P and L530P) in lamin A that are predicted to disrupt the Ig-fold, each reduced F-actin binding by ?66%, whereas the surface-exposed lipodystrophy-causing R482Q mutation had no significant effect. The lamin A tail was unique among lamins in having a second actin-binding site (AB-2). This second site was mapped to lamin A tail residues 564–608, based on actin-binding results for the lamin C tail and internal deletions in the lamin A tail that cause Hutchinson-Gilford Progeria Syndrome (?35, ?50) or restrictive dermopathy (?90). Supporting the presence of two actin-binding sites, recombinant precursor (unmodified) and mature lamin A tails (not C or B1 tails) each bundled F-actin in vitro: furthermore F-actin bundling was reduced 25–40% by the R527P, L530P, ?35 and ?50 mutations, and was abolished by ?90. Unexpectedly, the mature lamin A tail bound F-actin significantly more efficiently than did the prelamin A tail; this suggested unmodified residues 647–664, unique to prelamin A, might auto-inhibit binding to actin (and potentially other partners). These biochemical results suggest direct mechanisms by which lamins, particularly lamin A, might impact the concentration of free actin in the nucleus or pathways including transcription, nuclear export, chromatin remodeling, chromatin movement and nuclear assembly that require nuclear myosin 1c and polymerizable actin. PMID:21327074

Simon, Dan N; Zastrow, Michael S

2010-01-01

239

Matrix cracking and bending stiffness reduction in composite laminates  

E-print Network

Axial Tests 4. RESULTS AND DISCUSSION 4. 1 [0/90s], Laminate 4. 1. 1 0 j'901 ], Experimental Results 4. 1. 2 0/90s], Analytical Results 4. 1. 3, 0/90s], Analytical ? Experimental Comparison 4. 2 [90s/Oq, Laminate 4. 2. 1, '90'/Oq], Experimental... OF FIGURES Fig. 1 Equilibrium Element Used in Euler ? Bernoulli Development Fig. 2 Laminate Moment Equilibrium Element Fig. 3 Laminate Representative Volume Fig. 4 Bending and Shear Deformations Fig. 5 Timoshenko Equilibrium Element Fig. 6 Four Point...

Frailey, James Alan

2012-06-07

240

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

241

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. PMID:23401537

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

2013-01-01

242

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

243

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

244

Seasonal changes of diatom species in the Hooghly estuary, India  

NASA Astrophysics Data System (ADS)

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

Goswami, P. K.

2013-12-01

245

Vibrational nonequilibrium effects on diatomic dissociation rates  

NASA Technical Reports Server (NTRS)

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

Hansen, C. F.

1993-01-01

246

Cenozoic planktonic marine diatom diversity and correlation to climate change.  

PubMed

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

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

2014-01-01

247

Cenozoic Planktonic Marine Diatom Diversity and Correlation to Climate Change  

PubMed Central

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

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

2014-01-01

248

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

Microsoft Academic Search

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

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

1999-01-01

249

The effects of thermal and hygroscopic loads on unsymmetric composite laminates  

E-print Network

Symmetric Laminate A laminate is said to exhibit bending-extension coupling when the laminate bends and/or twists when pulled in tension. However, symmetric laminates do not exhibit this bending- extension coupling inherent to unsymmetric laminates... predetermined twist for anticipated membrane and bending loads can be selected. This can provide structural damping to minimize or to avoid flutter Although the curvature present in an unsymmetric laminate may be useful for manufacturing curved panels...

Ross, George Ray

2012-06-07

250

An experimental investigation of damage-dependent material damping of laminated composites  

E-print Network

-Chair of Committee) Charles E. Harris (Co-Chair of Commit tee) David H. Allen (Member) l, 3 Alan Wolfend n (Member) Walter E. Haisler (Head of Department) May 1988 ABSTRACT An Experimental Investigation of Damage-Dependent Material Damping of Laminated... Inducement, Damage Measurement MATHEMATICAL MODEL 11 15 36 38 RESULTS AND DISCUSSION 52 Laminate A, [0/90/0]s Laminate B, [90/0/90]s . Laminate C, [0/903]s . Laminate D, [903/0]s Laminate E, [0/90]2s . Laminate F, [90/0/902]s . Laminate...

Smith, Scott Andrew

2012-06-07

251

Laminated multilayer sheet structure and its utilization  

SciTech Connect

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 (B/sub 1/) bonded to a transparent synthetic resin layer (B/sub 2/), said layer (B/sub 1/) being a transparent thermic ray reflecting layer composed of (I) a layer of a metal having a thickness of about 50 to about 600 A, said metal being selected from the group consisting of gold, silver, copper, aluminum and a mixture of alloy of at least two of said metals, and (II) a high refractive substance layer having a thickness of about 50 to about 600 A, of an oxide of titanium derived from a layer of an organic titanium compound of the formula Ti/sub 1/O/sub m/R/sub n/, where R is alkyl of 1-20 carbon atoms, l=1-30, m=4+3(1-1), and n=4+2(1-1), and containing the organic residual moiety of the organic titanium compound, the amount of said organic residual moiety being 0.1 to 30% by weight based on the weight of the high refractive substance layer; or said layer (B/sub 1/) being a transparent semiconductive layer having a thickness of about 500 to about 5,000 a and being composed of a compound selected from the group consisting of indium oxide, tin oxide, cadmium oxide, antimony oxide, copper iodide, and a mixture of at least two of said compounds. A method is described for heat-insulating a room, which comprises applying to the surface of a floor, wall, ceiling or partition in the room a laminated multilayer sheet structure 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 (B/sub 1/) bonded to a transparent synthetic resin layer (B/sub 2/.)

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

1980-07-29

252

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

253

Fracture modes in notched angleplied composite laminates  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

254

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

255

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

256

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

257

Thermally-induced shapes of rigid FR4 electrical laminates  

Microsoft Academic Search

In the process of a laminate cooling from the curing temperature to room temperature, a substantial level of thermal residual stresses develop. These residual thermal stresses arise due to the mismatch of the thermal expansion coefficient between lamina and between the reinforcing fibers and the matrix resin, generating warpage, or out of plane deformations, when the laminate is not symmetric

Phra Douglas Lyle

1997-01-01

258

Weatherproof and mechanically stable laminate for encasing thermal insulation  

Microsoft Academic Search

A laminate is disclosed for encasing thermal insulation on objects comprising in the following order, an outer aluminum sheet, a first layer of polyethylene film, a layer of a kraft paper, a second layer of polyethylene film and a final sheet of aluminum foil, the laminate possessing excellent insulating ability as well as good weatherproof and mechanical stability properties.

Antoni

1978-01-01

259

A theory for predicting composite laminate warpage resulting from fabrication  

NASA Technical Reports Server (NTRS)

Linear laminate theory is used with the moment-curvature relationship to derive equations for predicting end deflections due to warpage without solving the coupled fourth-order partial differential equations of the plate. Composite micro- and macrohyphenmechanics are used with laminate theory to assess the contribution of factors such as ply misorientation, fiber migration, and fiber and/or void volume ratio nonuniformity on the laminate warpage. Using these equations, it was found that a 1 deg error in the orientation angle of one ply was sufficient to produce warpage end deflection equal to two laminate thicknesses in a 10 inch by 10 inch laminate made from 8 ply Mod-I/epoxy. Using a sensitivity analysis on the governing parameters, it was found that a 3 deg fiber migration or a void volume ratio of three percent in some plies is sufficient to produce laminate warpage corner deflection equal to several laminate thicknesses. Tabular and graphical data are presented which can be used to identify possible errors contributing to laminate warpage and/or to obtain an a priori assessment when unavoidable errors during fabrication are anticipated.

Chamis, C. C.

1974-01-01

260

Three-dimensional vibration analysis of rotating laminated composite blades  

Microsoft Academic Search

This work offers the first known three-dimensional continuum vibration analysis for rotating, laminated composite blades. A cornerstone of this work is that the dynamic energies of the rotating blade are derived from a three-dimensional elasticity based, truncated quadrangular pyramid model incorporating laminated orthotropicity, full geometric nonlinearity using an updated Lagrangian formulation and Coriolis acceleration terms. These analysis sophistications are included

O. G. McGee; H. R. Chu

1994-01-01

261

Strength in notched and impact-damaged laminates  

Microsoft Academic Search

The strength of notched and impact damaged laminates was studied. The solution for a plate containing an elliptic opening and inclusion was used as given by Lekhnitskii. The solution for the infinite plate, combined with laminate analysis to determine the ply stresses, and the average stress criterion proposed by Whitney and Nuismer were used to predict the notched strength. However,

El-Zein

1989-01-01

262

Measurement of the mechanical properties of angle ply laminates  

Microsoft Academic Search

Design of advanced fiber composite structures requires a knowledge of the strength and stiffness of laminates. For modulus, designs rely on classical lamination theory. For strength a failure criterion is needed. For off-axis plies this is normally a maximum stress criterion, or smoothed out versions such as \\

Jing Wang

2000-01-01

263

Lamin A-Dependent Nuclear Defects in Human Aging  

Microsoft Academic Search

Mutations in the nuclear structural protein lamin A cause the premature aging syndrome Hutchinson-Gilford progeria (HGPS). Whether lamin A plays any role in normal aging is unknown. We show that the same molecular mechanism responsible for HGPS is active in healthy cells. Cell nuclei from old individuals acquire defects similar to those of HGPS patient cells, including changes in histone

Paola Scaffidi; Tom Misteli

2006-01-01

264

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

265

Combined tension and bending testing of tapered composite laminates  

Microsoft Academic Search

A simple beam element used at Bell Helicopter was incorporated in the Computational Mechanics Testbed (COMET) finite element code at the Langley Research Center (LaRC) to analyze the responce of tappered laminates typical of flexbeams in composite rotor hubs. This beam element incorporated the influence of membrane loads on the flexural response of the tapered laminate configurations modeled and tested

T. Kevin O'Brien; Gretchen B. Murri; Rick Hagemeier; Charles Rogers

1994-01-01

266

Damage tolerance of a stitched carbon\\/epoxy laminate  

Microsoft Academic Search

Polymer composite laminates are prone to delamination when impacted. This behaviour generally results in a low damage tolerance, which is of great concern for load carrying applications. The possibility of improving the low velocity and ballistic impact damage tolerances of a carbon fibre brittle epoxy laminate by stitching has been investigated by determination of damage width, compression strength and other

Fritz Larsson

1997-01-01

267

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

268

Thermal modeling of carbon-epoxy laminates in fire environments  

Microsoft Academic Search

A thermal model is developed for the response of carbon-epoxy composite laminates in fire environments. The model is based on a porous media description that includes the effects of gas transport within the laminate along with swelling. Model comparisons are conducted against the data from Quintere et al. Simulations are conducted for both coupon level and intermediate scale one-sided heating

Matthew T. McGurn; Paul Edward DesJardin; Amanda B. Dodd

2010-01-01

269

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

E-print Network

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

Bertrand, Erin Marie

270

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

271

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

272

Free Vibration of Uncertain Unsymmetrically Laminated Beams  

NASA Technical Reports Server (NTRS)

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

Kapania, Rakesh K.; Goyal, Vijay K.

2001-01-01

273

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

274

Hygrothermally stable laminated composites with optimal coupling  

NASA Astrophysics Data System (ADS)

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

Haynes, Robert Andrew

275

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

276

Diatoms: a biotemplating approach to fabricating drug delivery reservoirs.  

PubMed

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

Chao, Joshua T; Biggs, Manus Jp; Pandit, Abhay S

2014-11-01

277

Ultrastructural observations on the marine fouling diatom Amphora  

NASA Astrophysics Data System (ADS)

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

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

1980-06-01

278

Circular random motion in diatom gliding under isotropic conditions.  

PubMed

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

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

2014-12-01

279

Diatom stratigraphy of the lower Pliocene part of the Sisquoc Formation, Harris Grade section, California  

Microsoft Academic Search

Lower Pliocene diatoms were studied from the Sisquoc Formation and lowermost Foxen Mudstone, exposed along Hams Grade north of Lompoc, California, to refine the diatom biostratigraphy of post-Monterey Formation sediments in California. Sixty-seven diatom taxa were identified in the 25 samples examined from the 790-m thick (2950-ft) section. The diatoms are assignable to the uppermost Nitzschia reinholdii Zone and Thalassiosira

John A. Barron; Jack G. Baldau

1986-01-01

280

Diatom data from Bradley Lake, Oregon: downcore analyses  

USGS Publications Warehouse

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

Hemphill-Haley, Eileen; Lewis, Roger C.

2003-01-01

281

Cenozoic planktonic marine diatom diversity and correlation to climate change  

USGS Publications Warehouse

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

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

2014-01-01

282

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

283

Antarctic climate cooling and response of diatoms in glacial meltwater streams  

Microsoft Academic Search

To understand biotic responses to an Antarctic cooling trend, we analyzed diatom samples from glacial meltwater streams in the McMurdo Dry Valleys, the largest ice-free area in Antarctica. Diatoms are abundant in these streams, and 24 of 40 species have only been found in the Antarctic. The percentage of these Antarctic diatom species increased with decreasing annual stream flow and

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

2006-01-01

284

Extreme streams: flow intermittency as a control on diatom communities in meltwater streams in  

E-print Network

to persist. Future Antarctic warming may alter diatom community composition and habitats that act as refugiaExtreme streams: flow intermittency as a control on diatom communities in meltwater streams. The benthic microbial mats harbor diatoms that have adapted to hydrologic stresses, including numerous endemic

Wall, Diana

285

Revisiting nutrient utilization in the glacial Antarctic: Evidence from a new method for diatom-bound  

E-print Network

Revisiting nutrient utilization in the glacial Antarctic: Evidence from a new method for diatom Antarctic: Evidence from a new method for diatom-bound N isotopic analysis, Paleoceanography, 19, PA3001; accepted 16 April 2004; published 1 July 2004. [1] Isotopic measurements of diatom-bound nitrogen, using

Sigman, Daniel M.

286

The amino acid and sugar composition of diatom cell-walls  

Microsoft Academic Search

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

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

1973-01-01

287

Climatically driven macroevolutionary patterns in the size of marine diatoms over the Cenozoic  

E-print Network

Climatically driven macroevolutionary patterns in the size of marine diatoms over the Cenozoic Zoe species over the Cenozoic. We found that the minimum and maximum sizes of the diatom frustule have ex through the Cenozoic. biological pump carbon cycle cell size climate change phytoplankton Diatoms

Falkowski, Paul G.

288

The Transcriptome and Proteome of the Diatom Thalassiosira pseudonana Reveal a Diverse Phosphorus  

E-print Network

The Transcriptome and Proteome of the Diatom Thalassiosira pseudonana Reveal a Diverse Phosphorus, we couple deep sequencing of transcript tags and quantitative proteomics to analyze the diatom ML, et al. (2012) The Transcriptome and Proteome of the Diatom Thalassiosira pseudonana Reveal

Benitez-Nelson, Claudia

289

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

290

Two-component modeling of the optical properties of a diatom bloom in the Southern Ocean  

E-print Network

Two-component modeling of the optical properties of a diatom bloom in the Southern Ocean Alex 2011 Keywords: Inherent optical properties Ocean color Southern Ocean Diatoms Diatom cells have species form chains or other colonial structures, and they tend to form aggregates during the senescent

Strathclyde, University of

291

Time-efficient numerical simulation of diatomic molecular spectra  

NASA Astrophysics Data System (ADS)

We present a quantum-mechanical procedure for calculating the photoabsorption spectra of diatomic molecules, entirely based on the Fourier grid Hamiltonian method for obtaining energies and the corresponding wave functions. Discrete and continuous spectrum contributions, which are the result of transitions between bound, free, and quasibound states of diatomic molecules were treated on the same footing. Using the classical Franck-Condon principle and the stationary-phase approximation, we also developed a "semiquantum" simulation method of the spectrum which allows an extremely time-efficient numerical algorithm, reducing the computer time by up to four orders of magnitude. The proposed method was tested on the absorption spectra of potassium molecules.

Beuc, Robert; Movre, Mladen; Horvati?, Berislav

2014-03-01

292

Diatoms in Historical Tsunami Deposits, Northern California, USA  

NASA Astrophysics Data System (ADS)

A fundamental challenge in using microfossils to differentiate paleotsunami deposits from those of other sources (storms, floods) is to identify characteristics that favor one mode of deposition over the other. The silt- to sand-size siliceous hard parts (valves) of diatoms are commonly found as transported particles in tsunami deposits, but logically, may also be found in other types of coastal deposits of the same grain size. To date, observations on diatom preservation and provenance have been invoked as supporting evidence for paleotsunami deposits. These observations can be tested and refined by detailed observations of diatom assemblages in recent, well-documented tsunami deposits. As a component of the U.S. Geological Survey Science Application for Risk Reduction (SAFRR) project, diatoms were examined in two historical tsunami deposits on the central and northern California coast: the 1946 deposit on the north end of Half Moon Bay (37.5°N) and the 1964 deposit about 10 km south of Crescent City (41.7°N). Both tsunamis were the result of distant-source events across the Pacific Ocean from California: the M 8.1 Eastern Aleutians Islands earthquake (1946) and the M 9.2 Alaska earthquake (1964). At both localities tsunami inundation was documented by eyewitness accounts. The deposits are now preserved in the shallow subsurface as ~1-10 cm thick layers of silt and sand intercalated in peaty marsh or clay-rich lagoon deposits. These historical tsunami deposits are particularly useful for documenting characteristics of entrained diatom assemblages for comparison to paleotsunami deposits. First, the deposits consist of mostly fine sand and silt, and therefore are an appropriate particle size for containing diatoms. Second, although they are recent enough to have been documented by eyewitness accounts, they are also old enough to have been altered by natural geological processes (e.g., burial, compaction, taphonomic affects on diatom valves) as would be found in paleotsunami deposits. Finally, although they are both the result of deposition by a distant-source tsunami at a coastal location not affected by coincident earthquake deformation (i.e., non-subsiding coast), they accumulated and were preserved in different kinds of coastal environments, and therefore the diatom records for each are different. At Half Moon Bay, the 1946 tsunami swept across a shallow brackish lagoon and salt marsh, leaving a deposit of clean, very fine sand containing large, allochthonous epipsammic diatoms consistent with landward-directed transport from the adjacent shallow marine nearshore. Where the deposit settled out and was later buried by clay-rich lagoon deposits, both the tsunami sand layer and entrained diatoms are well preserved. In contrast to the open, preservation-conducive lagoon environment at Half Moon Bay, the 1964 tsunami south of Crescent City inundated a freshwater marsh with thick stands of vegetation. The resultant paleotsunami deposit is limited in lateral extent, and dominantly contains well-preserved freshwater diatoms that mask obvious evidence of marine inundation.

Hemphill-Haley, E.; Loofbourrow, C.

2013-12-01

293

Mitotic lamin disassembly is triggered by lipid-mediated signaling  

PubMed Central

Disassembly of the nuclear lamina is a key step during open mitosis in higher eukaryotes. The activity of several kinases, including CDK1 (cyclin-dependent kinase 1) and protein kinase C (PKC), has been shown to trigger mitotic lamin disassembly, yet their precise contributions are unclear. In this study, we develop a quantitative imaging assay to study mitotic lamin B1 disassembly in living cells. We find that CDK1 and PKC act in concert to mediate phosphorylation-dependent lamin B1 disassembly during mitosis. Using ribonucleic acid interference (RNAi), we showed that diacylglycerol (DAG)-dependent PKCs triggered rate-limiting steps of lamin disassembly. RNAi-mediated depletion or chemical inhibition of lipins, enzymes that produce DAG, delayed lamin disassembly to a similar extent as does PKC inhibition/depletion. Furthermore, the delay of lamin B1 disassembly after lipin depletion could be rescued by the addition of DAG. These findings suggest that lipins activate a PKC-dependent pathway during mitotic lamin disassembly and provide evidence for a lipid-mediated mitotic signaling event. PMID:22986494

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

2012-01-01

294

Role of nuclear Lamin A/C in cardiomyocyte functions.  

PubMed

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

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

2014-10-01

295

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

296

Lamins regulate cell trafficking and lineage maturation of adult human hematopoietic cells  

E-print Network

Lamins regulate cell trafficking and lineage maturation of adult human hematopoietic cells Jae re- veals a lamin expression map that partitions human blood line- ages between marrow of high ploidy are inhibited by lamin suppression. Lamins thus contribute to both trafficking

Discher, Dennis

297

Transient response of a laminated composite plate  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

298

The digital pathologies of chronic laminitis.  

PubMed

This review indicates that the patient-to-patient uniqueness commonly seen in chronic laminitis represents the variable presence of the digital pathologies. Although some degree of mechanical failure is always present, the secondary metabolic and growth dysplasias, vascular pathologies, and sepsis may or may not be evident. The presence and severity of these pathologies appear to have a more significant impact on the prognosis of individual cases than does the displacement of the distal phalanx. It should be reiterated that it is often the combined presence of these individual pathologies that gives rise to the patient that is totally refractory to treatment. In the absence of these pathologies, many horses with significant displacement of the distal phalanx are not in pain and are not in need of treatment. It thus follows that a key to the improved rehabilitation of difficult patients is focusing research on the physiopathology and diagnosis of these nonmechanical problems. PMID:10472120

Grosenbaugh, D A; Morgan, S J; Hood, D M

1999-08-01

299

Stability optimization of laminated composite plates  

NASA Technical Reports Server (NTRS)

The optimum design of plates with orthotropic layers under axial compression and shear is discussed. The plates considered are the laminates of N orthotropic layers whose principal material axes coincide with the plate axes. Each layer is assumed to have the same thickness and an equal number of fibers in the direction of + alpha sub i and - alpha sub i with respect to the plate axis. The fiber directions which give the highest axial buckling stress and the highest shear buckling stress are found by utilizing a mathematical optimization technique for various aspect ratios of the plates. Inhomogeneity in the direction of the plate thickness (stacking sequence) is taken into account in this analysis.

Hirano, Y.

1980-01-01

300

Eddy current losses in ferromagnetic laminations  

SciTech Connect

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

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

2000-05-01

301

Laminated Wave Turbulence: Generic Algorithms II  

E-print Network

The model of laminated wave turbulence puts forth a novel computational problem - construction of fast algorithms for finding exact solutions of Diophantine equations in integers of order $10^{12}$ and more. The equations to be solved in integers are resonant conditions for nonlinearly interacting waves and their form is defined by the wave dispersion. It is established that for the most common dispersion as an arbitrary function of a wave-vector length two different generic algorithms are necessary: (1) one-class-case algorithm for waves interacting through scales, and (2) two-class-case algorithm for waves interacting through phases. In our previous paper we described the one-class-case generic algorithm and in our present paper we present the two-class-case generic algorithm.

Elena Kartashova; Alexey Kartashov

2006-11-17

302

Laminated Wave Turbulence: Generic Algorithms I  

E-print Network

The model of laminated wave turbulence presented recently unites both types of turbulent wave systems - statistical wave turbulence (introduced by Kolmogorov and brought to the present form by numerous works of Zakharov and his scientific school since nineteen sixties) and discrete wave turbulence (developed in the works of Kartashova in nineteen nineties). The main new feature described by this model is the following: discrete effects do appear not only in the long-wave part of the spectral domain (corresponding to small wave numbers) but all through the spectra thus putting forth a novel problem - construction of fast algorithms for computations in integers of order $10^{12}$ and more. In this paper we present a generic algorithm for polynomial dispersion functions and illustrate it by application to gravity and planetary waves.

E. Kartashova; A. Kartashov

2006-09-07

303

Extracellular Matrix Assembly in Diatoms (Bacillariophyceae)' 1. A Model of Adhesives Based on Chemical Characterization and localization of Polysaccharides from the Marine Diatom Achnanthes longipes and Other Diatoms  

Microsoft Academic Search

Extracellular adhesives from the diatoms Achnanthes longipes, Amphora coffeaeformis, Cymbella cisfula, 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 pro- duction of a highly organized shaft. Hot water-insoluble\\/hot 0.5 M NaHC0,-soluble anionic polysaccharides from A.

Brandon A. Wustman; Michael R. Cretz; Kyle D. Hoagland

304

Interlaminar stresses in composite laminates: A perturbation analysis  

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

305

Wave propagation in graphite/epoxy laminates due to impact  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

306

Accurate stress resultants equations for laminated composite deep thick shells  

SciTech Connect

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

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

1995-11-01

307

Vibration analysis of rotating thin laminated composite shell of revolution  

SciTech Connect

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

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

1995-11-01

308

Axisymmetric vibrations of laminated composite conical shells with varying thickness  

SciTech Connect

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

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

1995-11-01

309

Prolonged darkness and diatom mortality: II. Marine temperate species  

Microsoft Academic Search

The effect of prolonged darkness was tested on the diatom species Ditylum brightwellii (West) Grunow, Thalassiosira punctigera (Castracane) Hasle and Rhizosolenia setigera Brightwell, isolated from the North Sea. All species survived dark incubation in the vegetative state. D. brightwellii and T. punctigera survived 35 days in the dark, whereas R. setigera survived 21 days. Mass mortality occurred, at latest, after

E. Peters

1996-01-01

310

FLUORESCENCE QUENCHING AND THE DIADINOXANTHIN CYCLE IN A MARINE DIATOM  

EPA Science Inventory

The diadinoxanthin cycle (DD-cycle) in chromophyta algae involves the interconversion of two carotenoids, diadinoxanthin (DD) and diatoxanthin (DT). e investigated the kinetics of light-induced DD-cycling in the marine diatom Phaeodactylum triconutum and its role in dissipating e...

311

Diatom plastids depend on nucleotide import from the cytosol.  

PubMed

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

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

2009-03-01

312

Vibrational kinetics of diatomic molecules in parallel plate RF plasmas  

Microsoft Academic Search

In this paper, the history and state of the art of the theoretical modeling of the vibrational kinetics of diatomic molecules in nonequilibrium plasmas produced by parallel plate, capacitively coupled radio-frequency (RF) discharges are conceptually discussed. After introducing the physical framework and classical methods for the vibrational kinetics description in plasmas, the peculiarity and novelty of parallel plate RF discharges

S. Longo; P. Diomede; M. Capitelli

2008-01-01

313

Theory of high-precision Zeeman effect in diatomic molecules  

Microsoft Academic Search

A theoretical description of the Zeeman effect in a diatomic molecule is given on the basis of exact numerical diagonalization of the perturbation matrix. In this way it is also possible to include the fine and hyperfine structures to the desired degree of accuracy, and this is highly important for a complete theory of the molecular Zeeman effect. The present

L. Veseth

1976-01-01

314

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

315

Photoacclimation of antarctic marine diatoms to solar ultraviolet radiation  

Microsoft Academic Search

The present study was carried out at Palmer Station (64.7 ° S, 64.1 ° W), Antarctica, during the austral spring-summer of the years 1993 and 1994. Two centric diatom species (Thalassiosira sp. and Corethron criophilum Castracane) and two pennate species (Pseudonitzschia sp. and Fragilariopsis cylindrus (Grunow) Krieger) were isolated from natural phytoplankton assemblages and exposed to solar radiation to study

E. Walter Helbling; Bruce E. Chalker; Walter C. Dunlap; Osmund Holm-Hansen; Virginia E. Villafañe

1996-01-01

316

Conserved motif CMLD in silicic acid transport proteins of diatoms  

Microsoft Academic Search

Sequenced fragments of genes coding for silicon transporters (SITs) were analyzed for diatoms of evolutionarily distant classes (centric Chaetoceros muelleri Lemmermann, pennate araphid Synedra acus Kützing, pennate raphid Phaeodactylum tricornutum Bohlin, and pennate Cylindrotheca fusiformis Reimann et Lewin with a keeled raphe system). SITs were found to contain a conserved motif, CMLD. Hydropathy profiles showed that the motif CMLD is

T. A. Sherbakova; Yu. A. Masyukova; T. A. Safonova; D. P. Petrova; A. L. Vereshagin; T. V. Minaeva; R. V. Adelshin; T. I. Triboy; I. V. Stonik; N. A. Aizdaitcher; M. V. Kozlov; Ye. V. Likhoshway; M. A. Grachev

2005-01-01

317

Effect of dissociation on thermodynamic properties of pure diatomic gases  

NASA Technical Reports Server (NTRS)

A graphical method is described by which the enthalpy, entropy, and compressibility factor for the equilibrium mixture of atoms and diatomic molecules for pure gaseous elements may be obtained and shown for any dissociating element for which the necessary data exist. Results are given for hydrogen, oxygen, and nitrogen. The effect of dissociation on the heat capacity is discussed briefly.

Woolley, Harold W

1955-01-01

318

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...

319

Diatoms: unique eukaryotic extremophiles providing insights into planetary change  

NASA Astrophysics Data System (ADS)

The diatoms (Division Bacillariophyta) are aquatic, pigmented single-celled photosynthetic eukaryotes. They are a major component of the food chain in marine, estuarine and freshwater ecosystems. These diploid organisms have the ability to take dissolved silica out of the water column, and use it to create their cell walls. The taxonomy and classification system for the group is based to a large part on cell wall symmetry, as well as the number, type, position and organization of the many perforations in the glass. As a group, diatoms are found in almost every water type of water body around the globe, including a wide range of extreme environments. Individual species, however, have limited distributions and ecological requirements. Preservation of the glass cell walls in sedimentary basins has left nearly a 120 million year record. Species-related distributions, and well-preserved record make diatoms an excellent tool for environmental reconstruction and monitoring. New research on diatoms includes applications to conservation biology, astrobiology, nanotechnology, and biofuels.

Kociolek, J. P.

2007-09-01

320

The Buoyancy of Plankton Diatoms: A Problem of Cell Physiology  

Microsoft Academic Search

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

F. Gross; E. Zeuthen

1948-01-01

321

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

322

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...

323

Hemolytic activity in extracts of the diatom Nitzschia.  

PubMed

The few reports about diatom toxins are related to central nervous system toxicity, induced by domoic acid. In the present work Nitzschia sp. (Bacillariophyceae) was studied. The cells were cultured in f/2 medium, under 4000 lux and 14/10 hr light/dark cycle. After massive growth (5 x 10(6) cells/ml) the diatom cells were filtered, and an extract was prepared and partitioned in two fractions (polar and apolar). After cell harvesting by filtration, the diatom cells were shaken in artificial sea water to extract the water-soluble extracellular matrix (mucilage). An extract was prepared with the washed cells (free of mucilage), and polar and apolar fractions were obtained. Hemolytic assays were performed using 4.0 and 0.5% erythrocyte suspensions. Both the diatom polar and apolar fractions showed hemolytic activity. The membrane phospholipid sphingomyelin was tested as an acceptor for the hemolysins in the polar and apolar fractions. The mucilage did not exhibit hemolytic activity. PMID:9080587

Rangel, M; Malpezzi, E L; Susini, S M; de Freitas, J C

1997-02-01

324

Growth rates of large and small Southern Ocean diatoms in relation to availability of iron in natural seawater  

Microsoft Academic Search

Blooms of large diatoms dominate the CO2 drawdown and silicon cycle of the Southern Ocean in both the past and present. The growth of these Antarctic diatoms is limited by availability of iron (and light). Here we report the first assessment of growth rates in relation to iron availability of two truly oceanic Antarctic diatom species, the large, chain-forming diatom

Klaas R. Timmermans; Loes J. A. Gerringa; Hein J. W. de Baar; Bas van der Wagt; Marcel J. W. Veldhuis; Jeroen T. M. de Jong; Peter L. Croot; Marie Boye

2001-01-01

325

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. PMID:12114555

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

2002-01-01

326

Fossilized diatoms in meteorites from recent falls in Sri Lanka  

NASA Astrophysics Data System (ADS)

On December 29, 2012, a bright yellow and green fireball was observed to disintegrate over the Polonnaruwa District of North Central, Sri Lanka. Many low density, black stones were recovered soon after the observed fall from rice paddy fields near the villages of Aralaganwila and Dimbulagala. These stones were initially studied by optical microscopy methods at the Medical Research Institute in Colombo, Sri Lanka. Soon thereafter, samples were sent to the UK and to the United States. More extensive Field Emission Scanning Electron Microscopy studies were then carried out at Cardiff University and the NASA/Marshall Space Flight Center. The physico-chemical properties, elemental abundances, mineralogy and stable isotope data clearly indicate that these stones are non-terrestrial. Freshly fractured interior surfaces of the black stones have also been observed to contain the remains of fossilized diatom. Many of the diatom frustules are clearly embedded in the meteorite rock matrix and exhibit nitrogen levels below the EDX detection limits. Some of the fossil diatoms are araphid marine pennates and planktonic forms that are inconsistent with conditions associated with rice paddy fields. These observations indicate the fossilized diatoms are indigenous to the meteorites rather than post-arrival biological contaminants. The carbon content and mineralogy suggests that these stones may represent a previously ungrouped clan of carbonaceous meteorites. The extremely low density (~0.6) of the stones and their observed mineralogy was inconsistent with known terrestrial rocks (e.g., pumice, diatomite and fulgurites). The minerals detected suggest that the parent body of the Polonnaruwa stones may have been the nucleus of a comet. These observations are interpreted as supporting the Hoyle-Wickramasinghe Panspermia hypothesis and the hypothesis that diatoms and other microorganisms might be capable of living and growing in water ice and brines in comets.

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

2013-09-01

327

Diatom Proteomics Reveals Unique Acclimation Strategies to Mitigate Fe Limitation  

PubMed Central

Phytoplankton growth rates are limited by the supply of iron (Fe) in approximately one third of the open ocean, with major implications for carbon dioxide sequestration and carbon (C) biogeochemistry. To date, understanding how alteration of Fe supply changes phytoplankton physiology has focused on traditional metrics such as growth rate, elemental composition, and biophysical measurements such as photosynthetic competence (Fv/Fm). Researchers have subsequently employed transcriptomics to probe relationships between changes in Fe supply and phytoplankton physiology. Recently, studies have investigated longer-term (i.e. following acclimation) responses of phytoplankton to various Fe conditions. In the present study, the coastal diatom, Thalassiosira pseudonana, was acclimated (10 generations) to either low or high Fe conditions, i.e. Fe-limiting and Fe-replete. Quantitative proteomics and a newly developed proteomic profiling technique that identifies low abundance proteins were employed to examine the full complement of expressed proteins and consequently the metabolic pathways utilized by the diatom under the two Fe conditions. A total of 1850 proteins were confidently identified, nearly tripling previous identifications made from differential expression in diatoms. Given sufficient time to acclimate to Fe limitation, T. pseudonana up-regulates proteins involved in pathways associated with intracellular protein recycling, thereby decreasing dependence on extracellular nitrogen (N), C and Fe. The relative increase in the abundance of photorespiration and pentose phosphate pathway proteins reveal novel metabolic shifts, which create substrates that could support other well-established physiological responses, such as heavily silicified frustules observed for Fe-limited diatoms. Here, we discovered that proteins and hence pathways observed to be down-regulated in short-term Fe starvation studies are constitutively expressed when T. pseudonana is acclimated (i.e., nitrate and nitrite transporters, Photosystem II and Photosystem I complexes). Acclimation of the diatom to the desired Fe conditions and the comprehensive proteomic approach provides a more robust interpretation of this dynamic proteome than previous studies. PMID:24146769

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

2013-01-01

328

Diatom community structure on commercially available ship hull coatings.  

PubMed

Diatoms are primary colonizers of both antifouling and fouling-release ship hull coatings. There are few published studies which report on diatom community development on modern ship hull coatings. This study reports diatom communities on eight commercial marine ship hull coatings exposed at three static immersion sites along the east coast of Florida, viz. Daytona, Sebastian, and Miami. The coatings tested were three ablative copper systems (Ameron ABC-3, International BRA-640, and Hempel Olympic 76600), two copper-free biocidal systems (E-Paint SN-1, Sherwin Williams HMF), and three fouling-release (FR) systems (International Intersleek 700, International Intersleek 900, and Hempel Hempasil). One hundred and twenty-seven species comprising 44 genera were identified, including some of the more commonly known foulers, viz. Achnanthes, Amphora, Cocconeis, Entomoneis, Licmophora, Melosira, Navicula, Nitzschia, Synedra, and Toxarium. A significant difference was seen among sites, with the more estuarine site, Sebastian, having lower overall diatom abundance and higher diversity than Daytona and Miami. Copper coatings were primarily fouled by Amphora delicatissima and Entomoneis pseudoduplex. Copper-free coatings were fouled by Cyclophora tenuis, A. delicatissima, Achnanthes manifera, and Amphora bigibba. FR surfaces were typified by C. tenuis, and several species of Amphora. The presence of C. tenuis is new to the biofouling literature, but as new coatings are developed, this diatom may be one of many that prove to be problematic for static immersion. Results show coatings can be significantly influenced by geographical area, highlighting the need to test ship hull coatings in locations similar to where they will be utilized. PMID:21932984

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

2011-10-01

329

Nuclear lamins in the brain--new insights into function and regulation  

PubMed Central

The nuclear lamina is an intermediate filament meshwork composed largely of four nuclear lamins—lamins A and C (A-type lamins) and lamins B1 and B2 (B-type lamins). Located immediately adjacent to the inner nuclear membrane, the nuclear lamina provides a structural scaffolding for the cell nucleus. It also interacts with both nuclear membrane proteins and the chromatin and is thought to participate in many important functions within the cell nucleus. Defects in A-type lamins cause cardiomyopathy, muscular dystrophy, peripheral neuropathy, lipodystrophy, and progeroid disorders. In contrast, the only bona fide link between the B-type lamins and human disease is a rare demyelinating disease of the central nervous system—adult-onset autosomal-dominant leukoencephalopathy, caused by a duplication of the gene for lamin B1. However, this leukoencephalopathy is not the only association between the brain and B-type nuclear lamins. Studies of conventional and tissue-specific knockout mice have demonstrated that B-type lamins play essential roles in neuronal migration in the developing brain and in neuronal survival. The importance of A-type lamin expression in the brain is unclear, but it is intriguing that the adult brain preferentially expresses lamin C rather than lamin A, very likely due to microRNA-mediated removal of prelamin A transcripts. Here, we review recent studies on nuclear lamins, focusing on the function and regulation of the nuclear lamins in the central nervous system. PMID:23065386

Jung, Hea-Jin; Lee, John M.; Yang, Shao H.; Young, Stephen G.; Fong, Loren G.

2012-01-01

330

Modelling of thick composites using a layerwise laminate theory  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

331

A CLASS OF OPTIMAL TWO-DIMENSIONAL MULTIMATERIAL CONDUCTING LAMINATES  

E-print Network

A CLASS OF OPTIMAL TWO-DIMENSIONAL MULTIMATERIAL CONDUCTING LAMINATES NATHAN ALBIN1, ANDREJ, polyconvexity, rank-one convexity, multiwell variational problem . 1 #12;2 N. ALBIN, A. CHERKAEV, AND V. NESI

Cherkaev, Andrej

332

Nuclear lamins during gametogenesis, fertilization and early development  

NASA Technical Reports Server (NTRS)

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

Maul, G. G.; Schatten, G.

1986-01-01

333

Impact Damage to Composite Laminates: Effect of Impact Location  

NASA Astrophysics Data System (ADS)

Accidental impact loading of Composite laminates during manufacture and in-service can occur in different locations including near the edge or on the edge of a composite structure. This paper describes investigation of the effect of impact to composite laminates and compares the damage arising from central, near edge and on edge impact events. The damage tolerance of impact damaged laminates using both compression and tension tests has been measured. These results reveal the different damage mechanisms arising from different locations of impact. These different damage mechanisms have been investigated using X-Ray computed tomography. Impact on the edge of composite laminates is found to lead to smaller damage area, but more fibre failure; the severity of this damage is not revealed in standard compression after impact tests.

Malhotra, A.; Guild, F. J.

2014-02-01

334

Analysis of a unidirectional, symmetric buffer strip laminate with damage  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

335

Warpage eliminated in copper-clad microwave circuit laminates  

NASA Technical Reports Server (NTRS)

Cryogenic treatment of laminated copper-clad microwave circuit boards eliminates stresses that cause warpage when a circuit is etched on one side of the board. After etching, the stresses may be eliminated to reduce warpage.

Boone, W. L., Jr.

1967-01-01

336

Progressive Failure Analysis Methodology for Laminated Composite Structures  

NASA Technical Reports Server (NTRS)

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

Sleight, David W.

1999-01-01

337

Mechanics of fatigue damage in titanium-graphite hybrid laminates  

E-print Network

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

Burianek, Dennis Arthur

2001-01-01

338

Analysis and Compression Testing of Laminates Optimised for Damage Tolerance  

NASA Astrophysics Data System (ADS)

Barely Visible Impact Damage (BVID) can occur when laminated composite material is subject to out-of-plane impact loads and can result in a significant reduction in compressive strength. This paper reports on three compression tests of laminates optimised to maximise damage tolerance. Results from these tests were analysed using a semi-analytical, fracture mechanics based method that predicts the strain below which laminated coupons containing BVID subject to axial compression will not fail. A further experiment was conducted on an artificially delaminated coupon in order to validate the modelling methodology. Results from one of the two optimised stacking sequences considered show an increase of over 40% in Compression After Impact (CAI) strength compared with a baseline configuration. Analysis of results has indicated that CAI strength is dependent to a great extent on damage morphology and stability of damage growth, both of which are functions of laminate stacking sequence.

Rhead, Andrew T.; Butler, Richard; Baker, Neil

2011-02-01

339

Thermal Analysis of Piezoelectric Benders with Laminated Power Electronics  

E-print Network

Thermal Analysis of Piezoelectric Benders with Laminated Power Electronics Andrew J. Fleming1 with integrated high voltage power electronics. Such devices dramatically simplify the application of piezoelectric actuators since the power electronics are already optimized for the voltage range, capacitance

Fleming, Andrew J.

340

Characterization of delamination onset and growth in a composite laminate  

NASA Technical Reports Server (NTRS)

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

Obrien, T. K.

1981-01-01

341

Stairway fracture architecture in laminated to finely stratified rocks  

NASA Astrophysics Data System (ADS)

In this work we present the result of a study dealing on the architecture of fractures in laminated rocks, where they develop accordingly to a stairway architecture. On a section perpendicular to the sedimentary layering/structure intersection, this architecture consists of stepping fracture segments running parallel to the lamination/layering (LaP) connected by ramp segments (R) cutting across the laminations. The presence of lamination produces an anisotropy that deviates the average fracture propagation. The presence of LaP segments strongly influences the fracture induced permeability in these rocks by increasing connectivity. These fractures are formed by either the coalescence of individual fractures (representing the ramp segments) or as the result of a single propagating fracture. Stairway fractures are likely to form during syn-diagenetic conditions. Depending on the original lamination dip, a component of rock sliding may trigger or enhance the fracturing process. The architecture of stairway fractures is parameterized by the L/R ratio (the ratio between the lengths of the Ramp and LaP segments), the original lamination dip, and the cut-off angle (the angle between the ramp segment of the fracture and the lamination), in turn depending from the stress regime. Successive tilting may tilt the original lamination dip. In this view, the cut-off angle results a particularly suited parameter being related to the interplay between the rheology of the layers and the stress conditions at failure. A physical model of stairway fractures has been developed considering the effect of the rheological contrast between the layer and the intra-layer infilling, the fluid overpressure and the overburden. The model has been successfully applied to laminated rocks outcrops. The rheological parameters needed to match the observed geometry were obtained using a Montecarlo approach. The obtained rheological parameters are comparable with those presented in the literature and justify the LaP/Ramp proposed model. Two distinct behaviors were found and quantified depending on the original lamination/layers dip. Fluid pressure plays an important role in the development of the LaP segments. Resulting model may be applied to model fracture-induced permeability in laminated fluid reservoirs.

Maggi, Matteo; Cianfarra, Paola; Salvini, Francesco

2014-05-01

342

A Lamination Micro Mixer for µ-Immunomagnetic Cell Sorter  

Microsoft Academic Search

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

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

2005-01-01

343

Laminate composites with enhanced pyroelectric effects for energy harvesting  

Microsoft Academic Search

A pyroelectric coefficient enhanced 2-2 connectivity laminate composites' energy harvesting credentials have been assessed. The use of the electrothermal coupling factor for laminate composites (kLam2) for such an assessment has been appraised while the experimental samples are evaluated to show a significant improvement in their performance via pyroelectric coefficient enhancement, demonstrative of their great potential in energy harvesting applications. A

H. H. S. Chang; Z. Huang

2010-01-01

344

Simulation of fatigue performance of cross-ply composite laminates  

Microsoft Academic Search

The fatigue life of cross-ply composite laminates was evaluated using a statistical model. A modified shear-lag analysis was applied to describe the cycle-number-dependent stiffness reduction and consequent stress redistribution processes in the laminates resulted from both progressive transverse matrix cracking in transverse plies and local delamination at tips of transverse cracks. From the strength degradation behaviour and the static strength

Xiaoxue Diao; Lin Ye; Yiu-Wing Mai

1996-01-01

345

Determination of the technical constants of laminates in oblique directions  

NASA Technical Reports Server (NTRS)

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

Vidouse, F.

1979-01-01

346

Optimization of electromagnetic absorption in laminated composite plates  

Microsoft Academic Search

Analyzes an electromagnetic model of radar-absorbing layered structures for several stacking sequences of a woven glass\\/vinyl ester laminate, foam layers, and resistive sheets. It considers configurations that are either deposited on different backing materials or embedded in a laminated sandwich plate. Through-the-thickness layer dimensions and sheet resistances offering the best signal absorption over a specified frequency range are found for

Karel Matous; George J. Dvorak

2003-01-01

347

Fracture analysis of local delaminations in laminated composites  

NASA Technical Reports Server (NTRS)

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

Sriram, P.; Armanios, Erian A.

1988-01-01

348

Dynamic structural coupling behaviors of antisymmetric piezoelectric laminate  

Microsoft Academic Search

A study on the dynamic structural coupling behaviors of a laminated composite beam with an embedded piezo-ceramic (PZT) layer is presented in this paper. The composite structure under investigation is a three-layer laminate with anti-symmetric configuration, which leads to an extension-twisting structural coupling. Due to this coupling effect, when an electric filed is applied to the PZT layer, the actuated

HonLeung K. Wong; ShiWei R. Lee

2001-01-01

349

Dielectric, ferroelectric, magnetic, and magnetoelectric properties of multiferroic laminated composites  

Microsoft Academic Search

Multiferroic laminated composites consisting of lead-zirconate titanate (PZT)\\/polyvinylidene-fluoride (PVDF) particulate composite layers and Tb-Dy-Fe alloy (Terfenol-D)\\/PVDF particulate composite layers, prepared by a simple hot-molding technique, were reported. In the laminated composites, the polymer PVDF is inert and used just as a binder. The measured dielectric, ferroelectric, magnetic, and magnetoelectric properties demonstrate strong dependence on volume fraction f of the PVDF

N. Cai; J. Zhai; C.-W. Nan; Y. Lin; Z. Shi

2003-01-01

350

Tracer Lamination in the Stratosphere: A Global Climatology  

NASA Technical Reports Server (NTRS)

Vertical soundings of stratospheric ozone often exhibit laminated tracer structures characterized by strong vertical tracer gradients. The change in time of these gradients is used to define a tracer lamination rate. It is shown that this quantity can be calculated by the cross product of the horizontal temperature and horizontal tracer gradients. A climatology based on UARS satellite-borne ozone data and on ozone-like pseudotracer data is presented. Three stratospheric regions with high lamination rates were found: the part of the stratospheric overworld which is influenced by the polar vortex, the part of the lowermost stratosphere which is influenced by the tropopause and a third region in the subtropical lower stratosphere mainly characterized with strong vertical shear. High lamination rates in the stratospheric overworld were absent during summer, whereas in the lowermost stratosphere high lamination rates were found year-round. This is consistent with the occurrence and seasonal variation of the horizontal tracer gradient and vertical shear necessary for tilting the tracer surfaces. During winter, high lamination rates associated with the stratospheric polar vortex are present down to approximately 100 hPa. Several features of the derived climatology are roughly consistent with earlier balloon-borne studies. The patterns in the southern and northern hemisphere are comparable, but details differ as anticipated from a less disturbed and more symmetric southern polar vortex.

Appenzeller, Christof; Holton, James R.

1997-01-01

351

Response of automated tow placed laminates to stress concentrations  

NASA Technical Reports Server (NTRS)

In this study, the response of laminates with stress concentrations is explored. Automated Tow Placed (ATP, also known as Fiber Placement) laminates are compared to conventional tape layup manufacturing. Previous tensile fracture tests on fiber placed laminates show an improvement in tensile fracture of large notches over 20 percent compared to tape layup laminates. A hierarchial modeling scheme is presented. In this scheme, a global model is developed for laminates with notches. A local model is developed to study the influence of inhomogeneities at the notch tip, which are a consequence of the fiber placement manufacturing technique. In addition, a stacked membrane model was developed to study delaminations and splitting on a ply-by-ply basis. The results indicate that some benefit with respect to tensile fracture (up to 11 percent) can be gained from inhomogeneity alone, but that the most improvement may be obtained with splitting and delaminations which are more severe in the case of fiber placement compared to tape layup. Improvements up to 36 percent were found from the model for fiber placed laminates with damage at the notch tip compared to conventional tape layup.

Cairns, Douglas S.; Ilcewicz, Larry B.; Walker, Tom

1993-01-01

352

Preparation of composite board using foil-laminated and plastic-laminated liquid packaging paperboard as raw materials  

Microsoft Academic Search

We investigated the properties of composite board formed using base sheets of aluminum foil-laminated and polyethylene (PE)\\u000a plastic-laminated liquid packaging paperboard (LP) as an alternative to recycling these items in wastepaper stream. Boards\\u000a of different specific gravities ranging from 0.55 to 0.75 were made by pressing shredded LP blended with urea resin having\\u000a resin content of 6%–10% at 180C. Subsequently,

Gwo-Shyong Hwang; Eugene I-Chen Wang; Yu-Chang Su

2006-01-01

353

Increased solubility of lamins and redistribution of lamin C in X-linked Emery–Dreifuss muscular dystrophy fibroblasts  

Microsoft Academic Search

Emery–Dreifuss muscular dystrophy (EDMD) is caused by mutations in the gene encoding the nuclear membrane protein emerin (X-linked EDMD) or in the gene encoding lamins A\\/C (autosomal dominant EDMD). One hypothesis explaining the disease suggests that the mutations lead to weakness of the nuclear lamina. To test this hypothesis we investigated lamin solubility and distribution in skin fibroblasts from X-EDMD

Ewa Markiewicz; Rachel Venables; Mauricio-Alvarez-Reyes; Roy Quinlan; Margareth Dorobek; Irena Hausmanowa-Petrucewicz; Christopher Hutchison

2002-01-01

354

Diatom-inferred wind activity at Lac du Sommet, southern Québec, Canada: A multiproxy paleoclimate reconstruction based on diatoms, chironomids and pollen for the past 9500 years  

Microsoft Academic Search

Paleo surface wind for southern Quebec was inferred quantitatively for the past 9500 years from diatom assemblages archived in the sediment of the shallow mountain Lac du Sommet using biweekly sediment trap samples along an elevation gradient in the study area. The wind reconstruction was compared with diatom-inferred dissolved organic carbon concentration, chironomid-inferred mean August air temperature, pollen, grain size

Sonja Hausmann; Isabelle Larocque-Tobler; Pierre J. H. Richard; Reinhard Pienitz; Guillaume St-Onge; Falko Fye

2011-01-01

355

Nuclear localization signal deletion mutants of lamin A and progerin reveal insights into lamin A processing and emerin targeting.  

PubMed

Lamin A is a major component of the lamina, which creates a dynamic network underneath the nuclear envelope. Mutations in the lamin A gene (LMNA) cause severe genetic disorders, one of which is Hutchinson-Gilford progeria syndrome (HGPS), a disease triggered by a dominant mutant named progerin. Unlike the wild-type lamin A, whose farnesylated C-terminus is excised during post-translational processing, progerin retains its farnesyl tail and accumulates on the nuclear membrane, resulting in abnormal nuclear morphology during interphase. In addition, membrane-associated progerin forms visible cytoplasmic aggregates in mitosis. To examine the potential effects of cytoplasmic progerin, nuclear localization signal (NLS) deleted progerin and lamin A (PG?NLS and LA?NLS, respectively) have been constructed. We find that both ?NLS mutants are farnesylated in the cytosol and associate with a sub-domain of the ER via their farnesyl tails. While the farnesylation on LA?NLS can be gradually removed, which leads to its subsequent release from the ER into the cytoplasm, PG?NLS remains permanently farnesylated and membrane-bounded. Moreover, both ?NLS mutants dominantly affect emerin's nuclear localization. These results reveal new insights into lamin A biogenesis and lamin A-emerin interaction. PMID:24637396

Wu, Di; Flannery, Andrew R; Cai, Helen; Ko, Eunae; Cao, Kan

2014-01-01

356

Somatic lamins in germinal vesicles of goldfish (Carassius auratus) vitellogenic oocytes.  

PubMed

In fish and amphibians, B-type lamins are divided into somatic (B1, B2) and oocyte-type (B3) lamins. In this study, we purified nuclear lamins from rainbow trout erythrocytes, raised an anti-lamin monoclonal antibody (L-200) that recognizes goldfish somatic-lamins, and isolated cDNAs encoding goldfish B-type lamins (B1 and B2) from a goldfish cell culture cDNA library. Goldfish B-type lamins are structurally similar to lamins found in other vertebrates with minor amino acid substitutions in the conserved region. Western blot analysis showed that goldfish oocytes contained mainly GV-lamin B3 as well as some somatic lamins. Laser-confocal microscope observations revealed that lamin B3 was present only in GV nuclear lamina, whereas somatic lamins were present in dense fibrillar structures throughout nuclear gels of isolated GVs. Similar nuclear filamentous structures were also observed in GVs of paraffin embedded oocytes. Epitope mapping indicated that L-200 recognized a conserved region containing a short stretch of the alpha-helix coiled-coil rod domain (Y(E/Q)(Q/E)LL). A similar motif is also present in other cytoplasmic intermediate filaments (i.e., vimentin, desmin, peripherin and GFAP). Taken together, these findings suggest that lamins or lamin-related intermediate filaments are an important component of the interior architecture of goldfish vitellogenic oocyte nuclei (GVs). PMID:11942628

Yamaguchi, A; Nagahama, Y

2001-12-01

357

Progressive Fracture of Laminated Composite Stiffened Plate  

NASA Technical Reports Server (NTRS)

Laminated fiber-reinforced composite stiffened plate with [0/90/plus or minus 45]s plies made of S-Glass/epoxy are evaluated via computational simulation to study damage and fracture progression. The loads are pressure and temperature which varies from 21 to 65.5 C (case I) and from 143.3 to 21 C (case II). An integrated computer code is used for the simulation of the damage progression. Results show that damage initiation begins at low load level, with matrix cracking at the 0 deg. (bottom and top) plies, fiber fracture at the bottom (0 deg.) ply and interply delamination at the top (0 deg. ) ply. Increasing the applied pressure, the damage growth is expended resulting in fracture through the thickness of the structure. At this stage, 90 percent of the plies damage at applied pressure 15.306 MPa for the case I and 15.036 MPa for the case II. After this stage the cracks propagate rapidly and the structure collapses.

Gotsis, Pascalis K.; Chamis, Christos C.; David, Kostantinos; Abdi, Frank

2007-01-01

358

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. PMID:12223660

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

1997-01-01

359

Neural Network predictions of Diatomic and Triatomic Molecular Data  

NASA Astrophysics Data System (ADS)

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

Blake Laing, W.

1997-11-01

360

Toxic Diatom Pseudo-nitzschia and Its Primary Consumers (Vectors)  

Microsoft Academic Search

\\u000a Toxic algal blooms are occurring on a more frequent basis and have been shown to cause harm in higher trophic levels. The\\u000a diatom toxin domoic acid, produced by the genus Pseudo-nitzschia, has been shown to be responsible for the contamination of shellfish, zooplankton, and fish around the world. Contaminations\\u000a have impacted various economical markets as well. These primary consumers (vectors)

Sibel Bargu; Emily Smith; Koray Ozhan

361

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 morphological criteria visible in the light microscope. The geologic ranges of Actinocyclus species in the Western United States are discussed based on examination of over 100 localities of diatomaceous lacustrine deposits.

Edited by Bradbury, J. Platt; Krebs, William N.

1995-01-01

362

Localized atomic orbitals for atoms in molecules. II. Diatomic molecules  

Microsoft Academic Search

Using a previously described method, localized atomic orbitals (LAOs) for atoms in molecules are found for the atoms Li, B, C, N, O, and F in the diatomic molecules LiH, Li2, LiF, BH, B2, BF, C2, CO, NH, N2, and F2. In all instances LAOs partition into sets of core, lone pair, and bonding orbitals which, except in C2, are

Keith H. Aufderheide; Alice Chung-Phillips

1980-01-01

363

Direct imaging of quantum wires nucleated at diatomic steps  

SciTech Connect

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

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

2007-01-01

364

Light-temperature interactions on the growth of Antarctic diatoms  

Microsoft Academic Search

Summary  The combined effect of various temperatures and light intensities on the growth of seven species of antarctic diatoms in culture has been studied. With the exception of Chaetoceros deflandrei whose thermal tolerance is fairly good, these obligatory psychrophils cannot survive in temperatures above 6° to 9° C. Their mean growth rate is relatively low, between 0.24 div d–1 for Corethron

Michel Fiala; Louise Oriol

1990-01-01

365

Condensed-matter energetics from diatomic molecular spectra  

NASA Technical Reports Server (NTRS)

Analyses of molecular spectra and compression data from crystals show that a single function successfully describes the dependence on interatomic separation of both the potential energy of diatomic molecules and the cohesive binding energy of condensed matter. The empirical finding that one function describes interatomic energies for such diverse forms of matter and over a wide range of conditions can be used to extend condensed-matter equations of state but warrants further theoretical study.

Kim, In H.; Jeanloz, Raymond; Jhung, Kyu S.

1993-01-01

366

ADIAC: Using computer vision technology for automatic diatom identification  

E-print Network

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

Bayer, M.M.

367

The distribution and abundance of planktonic diatoms in Lake Superior  

USGS Publications Warehouse

The principal diatoms collected at 14 stations in Lake Superior were Cyclotella "glomerata-stelligera" [= C. glomerata and C. stelligera combined], Cyclotella "ocellata-kutzingiana", Fragilaria crotonensis, and Rhizosolenia eriensis. Concentrations were heaviest in the Apostle Islands region (up to 2,160 per ml) and lightest northwest of the Keweenaw Peninsula (68 to 78 per ml). Species composition differed in different parts of the lake.

Holland, Ruth E.

1965-01-01

368

Novel Sex Cells and Evidence for Sex Pheromones in Diatoms  

PubMed Central

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

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

2011-01-01

369

Paleoenvironmental impact of volcanic eruptions indicated by diatoms  

SciTech Connect

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

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

1985-01-01

370

PCB-resistant diatoms in the Hudson River estuary  

NASA Astrophysics Data System (ADS)

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

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

1988-02-01

371

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

NASA Astrophysics Data System (ADS)

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.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. Electronic supplementary information (ESI) available: Details on experimental methods, SEM analysis of IONP-DTMs and DTMs after incubation in a body fluid mimic. See DOI: 10.1039/c3nr05623f

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

2014-01-01

372

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

373

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

Microsoft Academic Search

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

Adrianna Ianora; Antonio Miralto

2010-01-01

374

Prolate-spheroidal models for monoexcited states of diatomic molecules. Application to H2  

Microsoft Academic Search

Within the shielded diatomic orbital (SDO) scheme, various approximate descriptions of monoexcited states of diatomic molecules are proposed including first- and second-order perturbation energies. The first-order perturbation energies are obtained in a rigorous way by using as excited-state wavefunction the antisymmetrized product of the ground-state wavefunction varphi of the corresponding diatomic core and a SDO psi corresponding to an empirical

M. Aubert-Frécon; C. Le Sech

1981-01-01

375

Distribution of Epilithic Diatoms in Response to Environmental Conditions in an Urban Tropical Stream, Central Kenya  

Microsoft Academic Search

Use of diatoms in monitoring water quality is well acknowledged in developed countries, but only recently has the assessment\\u000a started gaining importance in developing countries. Diatoms can be obtained from natural and artificial substrates. Appreciating\\u000a the differences and similarities of diatom assemblages on both substrates may contribute to a better understanding and standardization\\u000a particularly during monitoring of water quality. During

George G. Ndiritu; Nathan N. Gichuki; Ludwig Triest

2006-01-01

376

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

Microsoft Academic Search

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

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

2003-01-01

377

Subfossil and modern diatom plankton and the paleolimnology of Rotsee (Switzerland) since 1850  

Microsoft Academic Search

The diatom biostratigraphy of the topmost sediment meter of Rotsee, Central Switzerland, is characterized by a major change fromCyclotella comensis-dominated toStephanodiscus hantzschii\\/S. parvus-dominated assemblages. A comparison between old phytoplankton samples, taken between 1910–1930, and subfossil diatom assemblages is used for dating the upper 35 cm of the core. There is evidence that the change in dominant diatoms occurred in 1919\\/20,

André F. Lotter

1989-01-01

378

Biogeochemistry of silica in Devils Lake: Implications for diatom preservation  

USGS Publications Warehouse

Diatom-salinity records from sediment cores have been used to construct climate records of saline-lake basins. In many cases, this has been done without thorough understanding of the preservation potential of the diatoms in the sediments through time. The purpose of this study was to determine the biogeochemistry of silica in Devils Lake and evaluate the potential effects of silica cycling on diatom preservation. During the period of record, 1867-1999, lake levels have fluctuated from 427 m above sea level in 1940 to 441.1 m above sea level in 1999. The biogeochemistry of silica in Devils Lake is dominated by internal cycling. During the early 1990s when lake levels were relatively high, about 94% of the biogenic silica (BSi) produced in Devils Lake was recycled in the water column before burial. About 42% of the BSi that was incorporated in bottom sediments was dissolved and diffused back into the lake, and the remaining 58% was buried. Therefore, the BSi accumulation rate was about 3% of the BSi assimilation rate. Generally, the results obtained from this study are similar to those obtained from studies of the biogeochemistry of silica in large oligotrophic lakes and the open ocean where most of the BSi produced is recycled in surface water. During the mid 1960s when lake levels were relatively low, BSi assimilation and water-column dissolution rates were much higher than when lake levels were high. The BSi assimilation rate was as much as three times higher during low lake levels. Even with the much higher BSi assimilation rate, the BSi accumulation rate was about three times lower because the BSi water-column dissolution rate was more than 99% of the BSi assimilation rate compared to 94% during high lake levels. Variations in the biogeochemistry of silica with lake level have important implications for paleolimnologic studies. Increased BSi water-column dissolution during decreasing lake levels may alter the diatom-salinity record by selectively removing the less resistant diatoms. Also, BSi accumulation may be proportional to the amount of silica input from tributary sources. Therefore, BSi accumulation chronologies from sediment cores may be effective records of tributary inflow.

Lent, R.M.; Lyons, B.

2001-01-01

379

Tension fatigue analysis and life prediction for composite laminates  

NASA Technical Reports Server (NTRS)

A tension fatigue life prediction methodology for composite laminates is presented. Tension fatigue tests were conducted on quasi-isotropic and orthotropic glass epoxy, graphite epoxy, and glass/graphite epoxy hybrid laminates. Edge delamination onset data were used to generate plots of strain energy release rate as a function of cycles to delamination onset. These plots were then used along with strain energy release rate analyses of delaminations initiating at matrix cracks to predict local delamination onset. Stiffness loss was measured experimentally to account for the accumulation of matrix cracks and for delamination growth. Fatigue failure was predicted by comparing the increase in global strain resulting from stiffness loss to the decrease in laminate failure strain resulting from delaminations forming at matrix cracks through the laminate thickness. Good agreement between measured and predicted lives indicated that the through-thickness damage accumulation model can accurately describe fatigue failure for laminates where the delamination onset behavior in fatigue is well characterized, and stiffness loss can be monitored in real time to account for damage growth.

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

1988-01-01

380

Fracture behavior of unidirectional boron/aluminum composite laminates  

NASA Technical Reports Server (NTRS)

An experiment was conducted to verify the results of mathematical models which predict the stresses and displacements of fibers and the amount of damage growth in a center-notched lamina as a function of the applied remote stress and the matrix and fiber material properties. A brittle lacquer coating was used to detect the yielding in the matrix while X-ray techniques were used to determine the number of broken fibers in the laminate. The notched strengths and the amounts of damage found in the specimens agree well with those predicted by the mathematical model. It is shown that the amount of damage and the crack opening displacement does not depend strongly on the number of plies in the laminate for a given notch width. By heat-treating certain laminates to increase the yield stress of the alumina matrix, the effect of different matrix properties on the fracture behavior was investigated. The stronger matrix is shown to weaken the notched laminate by decreasing the amount of matrix damage, thereby making the laminate more notch sensitive.

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

1983-01-01

381

Effect of microcracks on the thermal expansion of composite laminates  

NASA Technical Reports Server (NTRS)

A finite element analysis was used to quantitatively predict the effect of matrix microcracks in the 90 deg plies of graphite/epoxy composites on the coefficient of thermal expansion in the 0 deg direction, alpha (y) (perpendicular to the cracks). Results were generated for (0m/90n)s, (0/+ or 45/90)s and (0/90/ + or - 45)s graphite/epoxy laminate configurations. Analytical predictions were compared with experimental results for the two quasi-isotropic laminate configurations. Both analytical and experimental results showed that microcracks reduced the effective stiffness of the 90 deg plies, thus causing the laminates, thermal response to be more like that of a (0) laminate. The change in alpha(y) was a function of lamina material properties, microcrack density, fiber orientation, and stacking sequence. A combination of classical lamination theory and finite element analysis was used to predict the effect of microcracks in both the 90 deg and 0 deg plies. Analytical results showed that the addition of microcracks in the 0 deg plies do affect alpha(y), but to a lesser extent than those in the 90 deg plies.

Bowles, D. E.

1984-01-01

382

Dynamic Stability of Uncertain Laminated Beams Under Subtangential Loads  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

383

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

E-print Network

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

García, Andre Phillipé

2010-01-01

384

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

ERIC Educational Resources Information Center

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

Hungerford, James J.

1988-01-01

385

Bacteria and diatom co-occurrence patterns in microbial mats from polar desert streams.  

PubMed

The ephemeral stream habitats of the McMurdo Dry Valleys of Antarctica support desiccation and freeze-tolerant microbial mats that are hot spots of primary productivity in an otherwise inhospitable environment. The ecological processes that structure bacterial communities in this harsh environment are not known; however, insights from diatom community ecology may prove to be informative. We examined the relationships between diatoms and bacteria at the community and taxon levels. The diversity and community structure of stream microbial mats were characterized using high-throughput pyrosequencing for bacteria and morphological identification for diatoms. We found significant relationships between diatom communities and the communities of cyanobacteria and heterotrophic bacteria, and co-occurrence analysis identified numerous correlations between the relative abundances of individual diatom and bacterial taxa, which may result from species interactions. Additionally, the strength of correlations between heterotrophic bacteria and diatoms varied along a hydrologic gradient, indicating that flow regime may influence the overall community structure. Phylogenetic consistency in the co-occurrence patterns suggests that the associations are ecologically relevant. Despite these community- and taxon-level relationships, diatom and bacterial alpha diversity were inversely correlated, which may highlight a fundamental difference between the processes that influence bacterial and diatom community assembly in these streams. Our results therefore demonstrate that the relationships between diatoms and bacteria are complex and may result from species interactions as well as niche-specific processes. PMID:22998505

Stanish, Lee F; O'Neill, Sean P; Gonzalez, Antonio; Legg, Teresa M; Knelman, Joseph; McKnight, Diane M; Spaulding, Sarah; Nemergut, Diana R

2013-04-01

386

Exceptionally well-preserved early Oligocene diatoms from glacial sediments of Prydz Bay, East Antarctica  

USGS Publications Warehouse

An exceptionally well-preserved early Oligocene diatom assemblage is documented and illustrated from the internal sediment of a gastropod shell, which was collected from glacial sedments recovered at ODP Site 739, Prydz Bay, Antarctica. The diatoms were deposited between 35.9 and 34.8 Ma according to diatom and calcareous nannofossil stratigraphy, apparently soon after a period of major ice sheet advance across the Prydz Bay continental shelf. The diatom assemblage is neritic in character, but it can readily be correlated with open ocean assemblages from the Southern Ocean as well as with similar material recovered from the CIROS-1 drillhole in the Ross Sea. -Authors

Barron, J. A.; Mahood, A. D.

1993-01-01

387

Lamination Formation, CO2 Uptake And Environmental Effects On Morphology: Siliceous Stromatolite Formation In A Hot Spring, Yellowstone National Park  

NASA Astrophysics Data System (ADS)

Siliceous stromatolites were collected from a hot spring in Yellowstone National Park in order to investigate stromatolite morphogenesis and growth rate. The majority of the stromatolite is composed of relatively porous light and dark layers of silica-coated filaments. The light layers (~150 ?m) predominantly consist of surface normal filaments and the dark layers (~50 ?m) are composed of reclining filaments. The main body lamination is interrupted by another style that drapes the entire structure, contains coccoidal as well as filamentous microbial forms, is well-cemented with silica, and includes a significant population of pennate diatoms. Over the course of stromatolite growth, the main body style and the drape style lamination alternated, but the majority of the growth is composed of the light/dark couplets. Radiometric dating (228Th/228Ra, 228Ra/226Ra, and 137Cs) indicate that the growth of a 5 cm stromatolite occurred on the order of years (not tens or hundreds of years), and in situ growth experiments reveal that the light/dark laminae couples do not represent daily, weekly or seasonal cycles. 14C analysis reveals that organic matter from the main body consistently contains lower ?14C versus the drape fabric. As CO2 from the hydrothermal vent waters is radio-carbon dead (which would result in lower ?14C values), we interpret the main body to have formed when spring level was deeper or flowing more vigorously, resulting in a greater influence from spring derived CO2 during photosynthetic CO2 uptake, and the drape to have formed when spring level was shallower or less vigorous, resulting in a greater incorporation of atmospheric CO2. More vigorous flow is likely to also affect the spring temperature. Combining the radiometric age dating, in situ growth experiments, and ?14C analysis suggests that growth of the light/dark couplets is sporadic and linked to rising water levels, whereas formation of the drape style lamination represents falling water levels and possible emergence. It is possible that the changing water levels, and thus stromatolite growth rate and morphology, record the larger scale geologic processes in Yellowstone National Park.

Corsetti, F. A.; Berelson, W.; Spear, J. R.; Hammond, D. E.; Pepe-Ranney, C.; Beaumont, W.

2010-12-01

388

Vibration suppression of laminated composite plates using embedded smart material layers  

E-print Network

In this study, a complete theoretical formulation of laminated composite plates with integrated smart material layers that serve as sensors and/or actuators is presented for the vibration suppression of laminated composite plates. The third...

Krishnan, Sivasubramaniam

2012-06-07

389

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

E-print Network

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

Iqbal, Jaffar S

2011-01-01

390

Statistical control and experimental design for edge bead reduction in laminating process  

E-print Network

Edge bead formation is a well-known phenomenon typically happening in the lamination due to the physics of this process. It causes the defect of high edge observed in the carton roll after the laminated carton sheets are ...

Fan, Huangjia (Francis Huangjia)

2010-01-01

391

Stiffness reduction and stress transfer in composite laminates with transverse matrix cracks  

E-print Network

Cross-ply laminates and angle-ply laminates with transverse plies containing through-width matrix cracks across the thickness of the transverse plies are studied using a variational, strain energy based approach, complementary to that of Hashin...

Praveen, Grama Narasimhaprasad

2012-06-07

392

Development of a Procedure to Evaluate the Shear Modulus of Laminated Glass Interlayers  

E-print Network

Laminated glass is comprised of multiple glass plates coupled together in a sandwich construction through the use of a polymorphous interlayer that acts as a bonding agent between the glass plates. Laminated glass offers several advantages over...

Brackin, Michael S.

2010-07-14

393

The effect of temperature on the bending of laminated glass beams  

E-print Network

monolithic glass. Some of the advantageous properties of laminated glass include a greater impact resistance, improved sound resistance, and better thermal insulation inside the structure. The most important advantage of laminated glass as compared...

Edel, Matthew Thomas

2012-06-07

394

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

E-print Network

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

Shim, Dong Jin, 1972-

2002-01-01

395

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

E-print Network

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

Michelis, Alexandros

2009-01-01

396

Magnetic field analysis of laminated core by using homogenization method  

NASA Astrophysics Data System (ADS)

This paper describes an approach to efficient modeling of the microscopic structure of magnetic materials in the nonlinear magnetostatic field analysis of a laminated core. When the ordinary finite element method is applied, large memory and computational cost are required due to the huge number of elements generated by detailed modeling of a laminated core. In order to overcome the above difficulties, we introduce the homogenization method, which is widely used in continuum mechanics, into the magnetic field computation and expand the method into the nonlinear analysis. Furthermore, the specialized homogenization method for a laminated core is carried out to verify the above homogenization method in the electromagnetism. Some numerical results are also presented to demonstrate the effectiveness of the proposed method.

Muto, H.; Takahashi, Y.; Wakao, S.; Fujiwara, K.; Kameari, A.

2006-04-01

397

Deformations of Flat Unsymmetric Laminates Subjected to Inplane Loads  

NASA Technical Reports Server (NTRS)

The geometrically nonlinear deformation response of initially flat unsymmetric cross-ply laminates subjected to an inplane compressive load and two sets of boundary conditions is studied. Stability of the deformations is considered. At issue is whether or not the plate remains flat with increased compressive loading, and whether it buckles. A semi-infinite unsymmetric cross-ply laminate is used to show the combined effects of geometric nonlinearities and bending-stretch coupling. Finite element results for finite laminates are then presented, and it is shown that to a large degree the boundary conditions control the character of the deformation response. It appears that clamped boundary conditions support buckling behavior, in the classic sense of bifurcation, whereas simply-supported conditions do not.

Hyer, Michael W.; Ochinero, Tomoya T.; Majeed, Majed

2004-01-01

398

Wear behaviour of composite laminates with hard superficial layers  

SciTech Connect

Intrinsic material properties of polymeric composite materials as rigidity and mechanical strength can be satisfactory for many applications while the superficial properties as wear resistance and corrosion cannot be satisfactory for specific employment conditions. Recent studies have shown that it is possible to change the superficial properties of composite laminates by the deposition of hard material films. The coating of composite components, however, brings a major complication during the fabrication process, for a special technological step is necessary. In this paper the authors propose to improve the superficial properties using hard particles embedded into the resin directly during the fabrication of the external layers of the laminate. In this way laminates have been obtained, where the superficial layers have been impregnated with resin with different hard particles. Results of wear tests show an increase of the wear resistance while SEM analysis show the rupture mechanisms of the fibers.

Visconti, I.C.; Langella, A.; Capuano, P. [Univ. of Naples (Italy). Dept. of Materials and Production

1993-12-31

399

Low velocity impact of inclined CSM composite laminates  

SciTech Connect

The damage tolerance of composite laminates subject to low velocity impact is an important aspect of current design philosophies required to ensure the integrity of primary load bearing structures. To the authors knowledge, no work published in the open literature has addressed the damage tolerance of composites subject to impacts at non-perpendicular inclinations, which in practical situations is the most common form of impact. This paper describes an experimental study, devised to assess the influence of inclined impact on the residual strength characteristics of CSM laminates. Preliminary experimental results and comparisons with previous work on flat plate impact tests are presented. The influence of the degree of inclination and impact energy are correlated with the laminates damage area and residual tensile properties.

Arnold, W.S.; Madjidi, S.; Marshall, I.H.; Robb, M.D. [Univ. of Paisley (United Kingdom). Dept. of Mechanical and Manufacturing Engineering

1993-12-31

400

Nonlinear response of resin matrix laminates using endochronic theory  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

401

Compression and compression fatigue testing of composite laminates  

NASA Technical Reports Server (NTRS)

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

Porter, T. R.

1982-01-01

402

Structural integrity of composite laminates with embedded micro-sensors  

NASA Astrophysics Data System (ADS)

The study of the mechanical interaction among the host, interface, and a device embedded within a laminated composite is important. Embedding micro-sensors in composite laminates produces material discontinuity around the inclusions. This in turn produces stress concentrations at or near the inclusions. Both 2D plane strain and 3D FEM models are developed to analyze the stress/strain state surrounding the embedded micro-sensors within a unidirectional composite laminate. The objective of the present numerical effort is to take into account the observed resin-rich areas caused by embedment, and to determine their effects on the local stress field around the embedment and the corresponding potential failure modes.

Huang, Yi; Nemat-Nasser, Sia

2007-04-01

403

Damage prediction in cross-plied curved composite laminates  

NASA Technical Reports Server (NTRS)

Analytical and experimental work is detailed which is required to predict delamination onset and growth in a curved cross plied composite laminate subjected to static and fatigue loads. The composite used was AS4/3501/6, graphite/epoxy. Analytically, a closed form stress analysis and 2-D and 3-D finite element analyses were conducted to determine the stress distribution in an undamaged curved laminate. The finite element analysis was also used to determine values of strain energy release rate at a delamination emanating from a matrix crack in a 90 deg ply. Experimentally, transverse tensile strength and fatigue life were determined from flat 90 deg coupons. The interlaminar tensile strength and fatigue life were determined from double cantilevered beam specimens. Cross plied curved laminates were tested statically and in fatigue to give a comparison to the analytical predictions. A comparison of the fracture mechanics life prediction technique and the strength based prediction technique is given.

Martin, Roderick H.; Jackson, Wade C.

1991-01-01

404

Fracture behavior of unidirectional boron/aluminum composite laminates  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

405

Laminations and microgranule formation in pediatric glomerular basement membranes.  

PubMed

Glomerular basement membrane (GBM) splitting, laminations, and microgranular formation are classically encountered with Alport disease, but can be found in other glomerular diseases. We found moderate to marked GBM laminations/microgranular formations in 51 of 724 (7%) pediatric diagnostic renal biopsies. These included 12 Alport disease, 12 thin basement membrane disease (TBM), 13 mesangial hypercellularity (MH), 6 focal segmental glomerulosclerosis (FSGS), and 8 other diseases. Follow-up demonstrated progression in most of the Alport disease and FSGS, as expected, but also in 40% of TBM and 30% of MH. Basement membrane laminations/microgranular formations are not specific for Alport disease, may represent a non-specific injury, and may herald a progressive clinical course. PMID:25394298

Craver, Randall; Crespo-Salgado, Janice; Aviles, Diego

2014-01-01

406

Snap-Through of Unsymmetric Laminates Using Piezocomposite Actuators  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

407

Low-temperature mechanical properties of glass/epoxy laminates  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

408

Proteins that associate with lamins: Many faces, many functions  

SciTech Connect

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

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

2007-06-10

409

Thermal modeling of carbon-epoxy laminates in fire environments.  

SciTech Connect

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

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

2010-10-01

410

Cloning and expression of ADAM related metalloproteases in Equine Laminitis  

PubMed Central

Equine laminitis is a debilitating disease affecting the digital laminae that suspends the distal phalanx within the hoof. While the clinical progression of the disease has been well documented, the molecular events associated with its pathogenesis remain largely unknown. We have investigated the expression of genes coding for proteins containing a Disintegrin and Metalloprotease domain (ADAM), as well as genes encoding the natural inhibitors of these enzymes (Tissue Inhibitor of MetalloProtease; TIMP) in horses with naturally acquired (acute, chronic and aggravated chronic cases collected in clinic) or experimentally-induced (black walnut extract and starch gruel models) laminitis using real time quantitative RT-PCR. Changes in expression of these enzymes and regulators may underlie the pathologic remodeling of lamellar tissue in laminitis. Genes encoding ADAMs involved in inflammation (ADAM-10 and ADAM-17), as well as those implicated in arthritis (ADAMTS-1, ADAMTS-4 and ADAMTS-5) were cloned, and the sequences used to generate specific oligonucleotide primers for the RT-qPCR experiments. Our results show that genes encoding ADAM-10 and 17 were not induced in most laminitic animals whereas ADAMTS-4 gene expression was strongly upregulated in practically all cases of experimentally induced and naturally acquired laminitis. The expression of MMP-9 and ADAMTS-5 was also increased in many of the laminitic horses. In addition, TIMP-2 gene expression was decreased in most laminitic horses, whereas expression of genes encoding other TIMPs, namely TIMP-1 and TIMP-3 was randomly increased or decreased in the various models. We conclude that elevated expression of lamellar ADAMTS-4 is a common feature of laminitis consistent with a central role of the gene product in the pathophysiology of laminitis. PMID:19131116

Coyne, Michael J.; Cousin, Helene; Loftus, John P.; Johnson, Philip J.; Belknap, James K.; Gradil, Carlos M.; Black, Samuel J.; Alfandari, Dominique

2010-01-01

411

Development of laminated fiber-reinforced nanocomposites for bone regeneration  

NASA Astrophysics Data System (ADS)

There have been numerous efforts to develop synthetic and/or natural tissue engineering scaffolds that are suitable for bone regeneration applications to replace autograft and allograft bones. Current biomaterials as a scaffold for bone regeneration are limited by the extent of degradation concurrent with bone formation, mechanical strength, and the extent of osteogenic differentiation of marrow stromal cells migrating from the surrounding tissues. In this project, a novel laminated nanocomposite scaffold is fabricated, consisting of poly (L-lactide ethylene oxide fumarate) (PLEOF) hydrogel reinforced with poly (L-lactic acid) (PLLA) electrospun nanofibers and hydroxyapatite (HA) nanoparticles. PLEOF is a novel in situ crosslinkable macromer synthesized from biocompatible building units which can be functionalized with bioactive peptides like the cell-adhesive Arg--Gly--Asp (RGD) amino acid sequence. The hydrophilicity and degradation rate of the macromer can be tailored to a particular application by controlling the ratio of PEG to PLA blocks in the macromer and the unsaturated fumarate units can be used for in-situ crosslinking. The PLLA nanofibers were electrospun from high molecular weight PLLA. The laminated nanocomposites were fabricated by dry-hand lay up technique followed by compression molding and thermal crosslinking. The laminated nanocomposites were evaluated with respect to degradation, water uptake, mechanical strength, and the extent of osteogenic differentiation of bone marrow stromal (BMS) cells. Laminates with or without HA nanoparticles showed modulus values much higher than that of trabecular bone (50-100 MPa). The effect of laminated nanocomposites on osteogenic differentiation of BMS cells was determined in terms of cell number, ALPase activity and calcium content. Our results demonstrate that grafting RGD peptide and HA nanoparticles to a PLEOF hydrogel reinforced with PLLA nanofibers synergistically enhance osteogenic differentiation of BMS cells. In conclusion, the laminated nanocomposite with controllable degradation characteristics and robust mechanical properties is attractive as a synthetic bone-mimetic matrix for skeletal tissue regeneration.

Xu, Weijie

412

A- and B-type lamins are differentially expressed in normal human tissues  

Microsoft Academic Search

A selection of normal human tissues was investigated for the presence of lamins B1, B2, and A-type lamins, using a panel\\u000a of antibodies specific for the individual lamin subtypes. By use of immunoprecipitation and two-dimensional immunoblotting\\u000a techniques we demonstrated that these antibodies do not cross-react with other lamin subtypes and that a range of different\\u000a phosphorylation isoforms is recognized by

Jos L. V. Broers; Barbie M. Machiels; Helma J. H. Kuijpers; Frank Smedts; Ronald van den Kieboom; Yves Raymond; Frans C. S. Ramaekers

1997-01-01

413

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

414

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

PubMed

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

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

2011-05-12

415

A higher order theory of laminated composite cylindrical shells  

NASA Technical Reports Server (NTRS)

A new higher order theory has been proposed for the analysis of composite cylindrical shells. The formulation allows for arbitrary variation of inplane displacements. Governing equations are presented in the form of a hierarchy of sets of partial differential equations. Each set describes the shell behavior to a certain degree of approximation. The natural frequencies of simply-supported isotropic and laminated shells and stresses in a ring loaded composite shell have been determined to various orders of approximation and compared with three dimensional solutions. These numerical studies indicate the improvements achievable in estimating the natural frequencies and the interlaminar shear stresses in laminated composite cylinders.

Krishna Murthy, A. V.; Reddy, T. S. R.

1986-01-01

416

Modeling localized properties of E-rated laminating lumber  

E-print Network

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

Richburg, Brent Allen

2012-06-07

417

An investigation of damage accumulation in graphite/epoxy laminates  

E-print Network

Page 77 33 Example of cr ack br anching fr om transverse crack at 0'/90' interface 78 34 X-r ay radiographs for a pr ogressively loaded [0/90?] laminate (dark rectangles ar e s aluminum extensometer mounting tabs) 35 Crack development by type... Page 77 33 Example of cr ack br anching fr om transverse crack at 0'/90' interface 78 34 X-r ay radiographs for a pr ogressively loaded [0/90?] laminate (dark rectangles ar e s aluminum extensometer mounting tabs) 35 Crack development by type...

Norvell, Robert Gerald

2012-06-07

418

Complex response of a bistable laminated plate: Multiscale entropy analysis  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

419

Nuclear architecture remodelling in cardiomyocytes with lamin A deficiency.  

PubMed

We analysed the architecture of cardiomyocyte nuclei lacking lamin A activity in three patients with dilated cardiomyopathy. The diagnosis was established on the basis of clinical and electrophysiological examinations, chest radiography and electrocardiography. An ultrastructural study of affected cardiomyocytes showed dramatic alterations in nuclear distribution and organization affecting nuclear shape, lamina structure, chromatin and nuclear interior organization. The most specific hallmark of nuclei with lamin A deficiency was the reorganization of the nuclear interior, the appearance of a various number of mitochondria within the nuclear matrix, and focal or total lack of nuclear membrane. PMID:18825595

Fidzia?ska, Anna; Walczak, Ewa; Glinka, Zofia; Religa, Grzegorz

2008-01-01

420

Fabrication of alumina films with laminated structures by ac anodization  

NASA Astrophysics Data System (ADS)

Anodization techniques by alternating current (ac) are introduced in this review. By using ac anodization, laminated alumina films are fabricated. Different types of alumina films consisting of 50-200 nm layers were obtained by varying both the ac power supply and the electrolyte. The total film thickness increased with an increase in the total charge transferred. The thickness of the individual layers increased with the ac voltage; however, the anodization time had little effect on the film thickness. The laminated alumina films resembled the nacre structure of shells, and the different morphologies exhibited by bivalves and spiral shells could be replicated by controlling the rate of increase of the applied potentials.

Segawa, Hiroyo; Okano, Hironaga; Wada, Kenji; Inoue, Satoru

2014-02-01

421

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

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

422

Molecular Genetic Analysis of the Nested Drosophila melanogaster Lamin C Gene  

PubMed Central

Lamins are intermediate filaments that line the inner surface of the nuclear envelope, providing structural support and making contacts with chromatin. There are two types of lamins, A- and B-types, which differ in structure and expression. Drosophila possesses both lamin types, encoded by the LamC (A-type) and lamin Dm0 (B-type) genes. LamC is nested within an intron of the essential gene ttv. We demonstrate that null mutations in LamC are lethal, and expression of a wild-type LamC transgene rescues lethality of LamC but not ttv mutants. Mutations in the human A-type lamin gene lead to diseases called laminopathies. To determine if Drosophila might serve as a useful model to study lamin biology and disease mechanisms, we generated transgenic flies expressing mutant LamC proteins modeled after human disease-causing lamins. These transgenic animals display a nuclear lamin aggregation phenotype remarkably similar to that observed when human mutant A-type lamins are expressed in mammalian cells. LamC aggregates also cause disorganization of lamin Dm0, indicating interdependence of both lamin types for proper lamina assembly. Taken together, these data provide the first detailed genetic analysis of the LamC gene and support using Drosophila as a model to study the role of lamins in disease. PMID:15965247

Schulze, Sandra R.; Curio-Penny, Beatrice; Li, Yuhong; Imani, Reza A.; Rydberg, Lena; Geyer, Pamela K.; Wallrath, Lori L.

2005-01-01

423

Stress and Failure Analysis of Composite Laminates with an Inclusion under Multiaxial Compression-Tension Loading  

Microsoft Academic Search

The present paper investigates the failure of orthotropic laminates with a filled hole subjected to biaxial compression-tension loading. This is an idealised case that simulates a situation where the impact damaged laminate has been repaired by drilling a hole and then plugging the hole with a perfect-fit core made of a dissimilar material. The exact stress distribution in the laminate

P. Berbinau; C. Filiou; C. Soutis

2001-01-01

424

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

EPA Science Inventory

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

425

Magneto-optical trapping of a diatomic molecule.  

PubMed

Laser cooling and trapping are central to modern atomic physics. The most used technique in cold-atom physics is the magneto-optical trap (MOT), which combines laser cooling with a restoring force from radiation pressure. For a variety of atomic species, MOTs can capture and cool large numbers of particles to ultracold temperatures (less than ?1 millikelvin); this has enabled advances in areas that range from optical clocks to the study of ultracold collisions, while also serving as the ubiquitous starting point for further cooling into the regime of quantum degeneracy. Magneto-optical trapping of molecules could provide a similarly powerful starting point for the study and manipulation of ultracold molecular gases. The additional degrees of freedom associated with the vibration and rotation of molecules, particularly their permanent electric dipole moments, allow a broad array of applications not possible with ultracold atoms. Spurred by these ideas, a variety of methods has been developed to create ultracold molecules. Temperatures below 1 microkelvin have been demonstrated for diatomic molecules assembled from pre-cooled alkali atoms, but for the wider range of species amenable to direct cooling and trapping, only recently have temperatures below 100 millikelvin been achieved. The complex internal structure of molecules complicates magneto-optical trapping. However, ideas and methods necessary for creating a molecular MOT have been developed recently. Here we demonstrate three-dimensional magneto-optical trapping of a diatomic molecule, strontium monofluoride (SrF), at a temperature of approximately 2.5 millikelvin, the lowest yet achieved by direct cooling of a molecule. This method is a straightforward extension of atomic techniques and is expected to be viable for a significant number of diatomic species. With further development, we anticipate that this technique may be employed in any number of existing and proposed molecular experiments, in applications ranging from precision measurement to quantum simulation and quantum information to ultracold chemistry. PMID:25143111

Barry, J F; McCarron, D J; Norrgard, E B; Steinecker, M H; DeMille, D

2014-08-21

426

Magneto-optical trapping of a diatomic molecule  

NASA Astrophysics Data System (ADS)

Laser cooling and trapping are central to modern atomic physics. The most used technique in cold-atom physics is the magneto-optical trap (MOT), which combines laser cooling with a restoring force from radiation pressure. For a variety of atomic species, MOTs can capture and cool large numbers of particles to ultracold temperatures (less than ~1 millikelvin) this has enabled advances in areas that range from optical clocks to the study of ultracold collisions, while also serving as the ubiquitous starting point for further cooling into the regime of quantum degeneracy. Magneto-optical trapping of molecules could provide a similarly powerful starting point for the study and manipulation of ultracold molecular gases. The additional degrees of freedom associated with the vibration and rotation of molecules, particularly their permanent electric dipole moments, allow a broad array of applications not possible with ultracold atoms. Spurred by these ideas, a variety of methods has been developed to create ultracold molecules. Temperatures below 1 microkelvin have been demonstrated for diatomic molecules assembled from pre-cooled alkali atoms, but for the wider range of species amenable to direct cooling and trapping, only recently have temperatures below 100 millikelvin been achieved. The complex internal structure of molecules complicates magneto-optical trapping. However, ideas and methods necessary for creating a molecular MOT have been developed recently. Here we demonstrate three-dimensional magneto-optical trapping of a diatomic molecule, strontium monofluoride (SrF), at a temperature of approximately 2.5 millikelvin, the lowest yet achieved by direct cooling of a molecule. This method is a straightforward extension of atomic techniques and is expected to be viable for a significant number of diatomic species. With further development, we anticipate that this technique may be employed in any number of existing and proposed molecular experiments, in applications ranging from precision measurement to quantum simulation and quantum information to ultracold chemistry.

Barry, J. F.; McCarron, D. J.; Norrgard, E. B.; Steinecker, M. H.; Demille, D.

2014-08-01

427

Diatom immigration drives biofilm recovery after chronic copper exposure 1 This is the peer-reviewed version of the following article: Diatom immigration drives biofilm recovery after chronic copper  

E-print Network

Diatom immigration drives biofilm recovery after chronic copper exposure 1 2 3 4 5 This is the peer-reviewed version of the following article: Diatom immigration drives biofilm recovery after, 69336 Lyon, France Summary 1. The impact of immigration on the recovery of diatom assemblages after

Paris-Sud XI, Université de

428

Quantum computation with diatomic bits in optical lattices  

SciTech Connect

We propose a scheme for scalable and universal quantum computation using diatomic bits with conditional dipole-dipole interaction, trapped within an optical lattice. The qubit states are encoded by the scattering state and the bound heteronuclear molecular state of two ultracold atoms per site. The conditional dipole-dipole interaction appears between neighboring bits when they both occupy the molecular state. The realization of a universal set of quantum logic gates, which is composed of single-bit operations and a two-bit controlled-NOT gate, is presented. The readout method is also discussed.

Lee, Chaohong; Ostrovskaya, Elena A. [Nonlinear Physics Centre and ARC Centre of Excellence for Quantum-Atom Optics, Research School of Physical Sciences and Engineering, Australian National University, Canberra ACT 0200 (Australia)

2005-12-15

429

Exact path integral treatment of a diatomic molecule potential  

SciTech Connect

A rigorous evaluation of the path integral for Green's function associated with a four-parameter potential for a diatomic molecule is presented. A closed form of Green's function is obtained for different shapes of this potential. When the deformation parameter {lambda} is {lambda}<0 or 0<{lambda}<1, it is found that the quantization conditions are transcendental equations that require a numerical solution. For {lambda}{>=}1 and r set-membership sign](1/{eta})ln {lambda},{infinity}[, the energy spectrum and the normalized wave functions of the bound states are derived. Particular cases of this potential which appear in the literature are also briefly discussed.

Benamira, F.; Guechi, L.; Mameri, S.; Sadoun, M. A. [Laboratoire de Physique Theorique, Departement de Physique, Faculte des Sciences Exactes, Universite Mentouri, Route d'Ain El Bey, Constantine 25000 DZ (Algeria)

2007-03-15

430

Antifreeze Protein in Antarctic Marine Diatom, Chaetoceros neogracile  

Microsoft Academic Search

The antifreeze protein gene (Cn-AFP) from the Antarctic marine diatom, Chaetoceros neogracile was cloned and characterized. The full-length Cn-AFP cDNA contained an open reading frame of 849 bp and the deduced 282 amino\\u000a acid peptide chain encodes a 29.2 kDa protein, which includes a signal peptide of 30 amino acids at the N terminus. Both the\\u000a Cn-AFP coding region with and without

In Gyu Gwak; Woong sic Jung; Hak Jun Kim; Sung-Ho Kang; EonSeon Jin

2010-01-01

431

Dissociation rate of bromine diatomics in an argon heat bath  

NASA Technical Reports Server (NTRS)

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

Razner, R.; Hopkins, D.

1973-01-01

432

Indiana University Southeast Physics Applets: Two Dimensional Diatomic Model Simulation  

NSDL National Science Digital Library

This item is a simulation on the movement and energy of a diatomic molecule made up of two atoms with a mass ratio of 1:4. Users can observe the kinetic energy in both atoms, as well as the energy stored in the spring connecting them. Context-rich questions are included on the average kinetic energy of the atoms, their thermal equilibrium with each other, and how their speed changes as the spring gains energy. This page is part of a collection of Java applets with tutorial questions developed for students of undergraduate physics.

Forinash, Kyle

2008-08-31

433

Direct imaging of quantum wires nucleated at diatomic steps  

SciTech Connect

Atomic steps at growth surfaces are important heterogeneous sources for nucleation of epitaxial nano-objects. In the presence of misfit strain, we show that the nucleation process takes place preferentially at the upper terrace of the step as a result of the local stress relaxation. Evidence for strain-induced nucleation comes from the direct observation by postgrowth, atomic resolution, Z-contrast imaging of an InAs-rich region in a nanowire located on the upper terrace surface of an interfacial diatomic step.

Molina, S. I.; Varela, M.; Sales, D. L.; Ben, T.; Pizarro, J.; Galindo, P. L.; Fuster, D.; Gonzalez, Y.; Gonzalez, L.; Pennycook, S. J. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Departamento de Ciencia de los Materiales e I.M. y Q.I., Facultad de Ciencias, Universidad de Cadiz, Campus Rio San Pedro, Puerto Real, 11510 Cadiz (Spain); Departamento de Lenguajes y Sistemas Informaticos, CASEM, Universidad de Cadiz, Campus Rio San Pedro, Puerto Real, 11510 Cadiz (Spain); Instituto de Microelectronica de Madrid (CNM, CSIC), Isaac Newton 8, Tres Cantos, 28760 Madrid (Spain); Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennesse 37831 (United States)

2007-10-01

434

Intracellular distribution of the reductive and oxidative pentose phosphate pathways in two diatoms.  

PubMed

Diatoms contribute a large proportion to the worldwide primary production and are particularly effective in fixing carbon dioxide. Possibly because diatom plastids originate from a secondary endocytobiosis, their cellular structure is more complex and metabolic pathways are rearranged within diatom cells compared to cells containing primary plastids. We annotated genes encoding isozymes of the reductive and oxidative pentose phosphate pathways in the genomes of the centric diatom Thalassiosira pseudonana and the pennate diatom Phaeodactylum tricornutum and bioinformatically inferred their intracellular distribution. Prediction results were confirmed by fusion of selected presequences to Green Fluorescent Protein and expression of these constructs in P. tricornutum. Calvin cycle enzymes for the carbon fixation and reduction of 3-phosphoglycerate are present in single isoforms, while we found multiple isoenzymes involved in the regeneration of ribulose-1,5-bisphosphate. We only identified one cytosolic sedoheptulose-1,7-bisphosphatase in both investigated diatoms. The oxidative pentose phosphate pathway seems to be restricted to the cytosol in diatoms, since we did not find stromal glucose-6-phosphate dehydrogenase and 6-phosphogluconolactone dehydrogenase isoforms. However, the two species apparently possess a plastidic phosphogluconolactonase. A 6-phosphogluconolactone dehydrogenase is apparently plastid associated in P. tricornutum and might be active in the periplastidic compartment, suggesting that this compartment might be involved in metabolic processes in diatoms. PMID:19206144

Gruber, Ansgar; Weber, Till; Bártulos, Carolina Río; Vugrinec, Sascha; Kroth, Peter G

2009-02-01

435

Author's personal copy A time-calibrated multi-gene phylogeny of the diatom genus Pinnularia  

E-print Network

Author's personal copy A time-calibrated multi-gene phylogeny of the diatom genus Pinnularia College, New London, CT 06320, USA e Department of Botany, The Natural History Museum, Cromwell Road Fossil record Raphid diatoms Pinnularia Bacillariophyceae Eocene a b s t r a c t Pinnularia

Wolfe, Alexander P.

436

Evidence for reduced biogenic silica dissolution rates in diatom B. Moriceau 1,2*  

E-print Network

1 Evidence for reduced biogenic silica dissolution rates in diatom aggregates B. Moriceau 1,2* , M head: Biogenic silica dissolution in diatom aggregates hal-00381254,version1-23Jun2009 Author for dissolution, aggregation influences the balance between recycling of biogenic silica (BSiO2) and its

Boyer, Edmond

437

Abstract Diatom and geochemical data from Crawford Lake, Ontario, have been used to docu-  

E-print Network

periods of cultural eutrophication and examine the limno- logical processes that occurred during ORIGINAL PAPER Diatom assemblage response to Iroquoian and Euro-Canadian eutrophication of Crawford Lake- turbance and recovery in lake systems. Keywords Crawford Lake Ã? Diatoms Ã? Iroquoian Ã? Eutrophication Ã?

McAndrews, John H.

438

Characterization of high arctic stream diatom assemblages from Cornwallis Island, Nunavut,  

E-print Network

Characterization of high arctic stream diatom assemblages from Cornwallis Island, Nunavut, Canada Island, Nunavut, Canada (75°06N, 93°36W). A total of 64 diatom taxa were identified from epilithic sept lacs et de deux rivières entourant le lac Sophia de l'île Cornwallis, au Nunavut, Canada (75°06N

Vincent, Warwick F.

439

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

EPA Science Inventory

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

440

Diatom cultivation and biotechnologically relevant products. Part I: Cultivation at various scales  

Microsoft Academic Search

Biotechnological applications of diatoms are still in development. Further development at the industrial scale will depend on optimisation of the culture process with the aim of reducing costs. Because of the photoautotrophic status of the majority of diatoms, microalgal cultures suffer from the limitation of light diffusion, which requires the development of suitable photobioreactors. Thus, genetically engineered microalgae that may

Thierry Lebeau; Jean-Michel Robert

2003-01-01

441

Ecological responses of epilithic diatoms and aquatic macrophytes to fish farm pollution in a Spanish river  

E-print Network

Ecological responses of epilithic diatoms and aquatic macrophytes to fish farm pollution.A. & Jiménez, A. 2007. Ecological responses of epilithic diatoms and aquatic macrophytes to fish farm pollution than at S-3 and S-4, with a clear tendency to improve with distance from the fish farm. In contrast

Espigares, Tíscar

442

MORPHOLOGY, ECOLOGY AND DISTRIBUTION OF AN ENDEMIC ANTARCTIC LACUSTRINE DIATOM: CHAMAEPINNULARIA CYMATOPLEURA COMB. NOV  

Microsoft Academic Search

Specimens belonging to the diatom species Pinnularia cymatopleura collected from benthic cyanobacterial mats of lakes and ponds in Continental Antarctica were examined. In addiction, slides from the West & West collection which contain isotypes of this taxon were also investigated. Light Microscope (LM) and Scanning Electron Microscope (SEM) studies of this diatom reveal that its valve structure possesses features typical

Paolo Cavacini; Nadia Tagliaventi; Bruno Fumanti

2006-01-01

443

Resting spore formation in the antarctic diatoms Coscinodiscus furcatus Karsten and Thalassiosira australis Peragallo  

Microsoft Academic Search

The resting spore morphology of the antarctic diatoms Coscinodiscus furcatus Karsten and Thalassiosira australis Peragallo are described. Both species form endogenous resting spores. The spore valve of C. furcatus differ from those of the vegetative cells primarily by (i) a greater convexity and (ii) a coarser and more distinctly fasciculated areolation. This resting spore is identical to the diatom traditionally

Erik E. Syvertsen

1985-01-01