Environmental exposure effects on composite materials for commercial aircraft

A study was conducted to determine the effects of long term flight and ground exposure on three commercially available graphite-epoxy material systems: T300/5208, T300/5209, and T300/934. Sets of specimens were exposed on commercial aircraft and ground racks for 1, 2, 3, 5, and 10 years. Inflight specimen sites included both the interior and exterior of aircraft based in Hawaii, Texas, and New Zealand. Ground racks were located at NASA-Dryden and the above mentioned states. Similar specimens were exposed to controlled lab conditions for up to 2 years. After each exposure, specimens were tested for residual strength and a dryout procedure was used to measure moisture content. Both room and high temperature residual strengths were measured and expressed as a pct. of the unexposed strength. Lab exposures included the effects of time alone, moisture, time on moist specimens, weatherometer, and simulated ground-air-ground cycling. Residual strengths of the long term specimens were compared with residual strengths of the lab specimens. Strength retention depended on the exposure condition and the material system. Results showed that composite materials can be successfully used on commercial aircraft if environmental effects are considered

Planktonic Microbes in the Gulf of Maine Area

In the Gulf of Maine area (GoMA), as elsewhere in the ocean, the organisms of greatest numerical abundance are microbes. Viruses in GoMA are largely cyanophages and bacteriophages, including podoviruses which lack tails. There is also evidence of Mimivirus and Chlorovirus in the metagenome. Bacteria in GoMA comprise the dominant SAR11 phylotype cluster, and other abundant phylotypes such as SAR86-like cluster, SAR116-like cluster, Roseobacter, Rhodospirillaceae, Acidomicrobidae, Flavobacteriales, Cytophaga, and unclassified Alphaproteobacteria and Gammaproteobacteria clusters. Bacterial epibionts of the dinoflagellate Alexandrium fundyense include Rhodobacteraceae, Flavobacteriaceae, Cytophaga spp., Sulfitobacter spp., Sphingomonas spp., and unclassified Bacteroidetes. Phototrophic prokaryotes in GoMA include cyanobacteria that contain chlorophyll (mainly Synechococcus), aerobic anoxygenic phototrophs that contain bacteriochlorophyll, and bacteria that contain proteorhodopsin. Eukaryotic microalgae in GoMA include Bacillariophyceae, Dinophyceae, Prymnesiophyceae, Prasinophyceae, Trebouxiophyceae, Cryptophyceae, Dictyochophyceae, Chrysophyceae, Eustigmatophyceae, Pelagophyceae, Synurophyceae, and Xanthophyceae. There are no records of Bolidophyceae, Aurearenophyceae, Raphidophyceae, and Synchromophyceae in GoMA. In total, there are records for 665 names and 229 genera of microalgae. Heterotrophic eukaryotic protists in GoMA include Dinophyceae, Alveolata, Apicomplexa, amoeboid organisms, Labrynthulida, and heterotrophic marine stramenopiles (MAST). Ciliates include Strombidium, Lohmaniella, Tontonia, Strobilidium, Strombidinopsis and the mixotrophs Laboea strobila and Myrionecta rubrum (ex Mesodinium rubra). An inventory of selected microbial groups in each of 14 physiographic regions in GoMA is made by combining information on the depth-dependent variation of cell density and the depth-dependent variation of water volume. Across the entire GoMA, an estimate for the minimum abundance of cell-based microbes is 1.7×1025 organisms. By one account, this number of microbes implies a richness of 105 to 106 taxa in the entire water volume of GoMA. Morphological diversity in microplankton is well-described but the true extent of taxonomic diversity, especially in the femtoplankton, picoplankton and nanoplankton – whether autotrophic, heterotrophic, or mixotrophic, is unknown

Expert Systems and Multimedia: Examining the Potential for Integration

Expert systems and multimedia are being incorporated into organizations at increasing rates because, while being independently developed, they possess capabilities appropriate for integration with each other. This paper examines the potential for such integration, providing support to users beyond the capabilities of each independently used technology. An integrated system, essential to the city of Los Angeles during the 1992 riots and the 1994 earthquake, is examined to demonstrate the usefulness and benefits of expert systems and multimedia integration. The potential for this integration is further explored by examining issues related to an integration framework where the two technologies support each other. Three integrated prototype systems are reviewed to promote the legitimacy of expert systems and multimedia integration. Preliminary findings conclude that this integration will offer benefits to various applications. © 1995 M.E. Sharpe, Inc

Stereospecific Ring-Opening Metathesis Polymerization of Norbornadienes Employing Tungsten Oxo Alkylidene Initiators

We report here the polymerization of several 7-isopropylidene-2,3-disubstituted norbornadienes, 7-oxa-2,3-dicarboalkoxynorbornadienes, and 11-oxa-benzonorbornadienes with a single tungsten oxo alkylidene catalyst, W(O)(CH-t-Bu)(OHMT)(Me2Pyr) (OHMT = 2,6-dimesitylphenoxide; Me2Pyr = 2,5-dimethylpyrrolide) to give cis, stereoregular polymers. The tacticities of the menthyl ester derivatives of two polymers were determined for two types. For poly(7-isopropylidene-2,3-dicarbomenthoxynorbornadiene) the structure was shown to be cis,isotactic, while for poly(7-oxa-2,3-dicarbomenthoxynorbornadiene) the structure was shown to be cis,syndiotactic. A bis-trifluoromethyl-7-isopropylidene norbornadiene was not polymerized stereoregularly with W(O)(CHCMe2Ph)(Me2Pyr)(OHMT) alone, but a cis, stereoregular polymer was formed in the presence of 1 equiv of B(C6F5)3.United States. Dept. of Energy (DE-FG02- 86ER13564)Defense Threat Reduction Agency (DTRA) (Chemical and Biological Technologies, grant BA12PHM123 in the “Dynamic Multifunctional Materials for a Second Skin D[MS]2” program

Tungsten Oxo Alkylidene Complexes as Initiators for the Stereoregular Polymerization of 2,3-Dicarbomethoxynorbornadiene

We have employed 2,3-dicarbomethoxynorbornadiene (DCMNBD) as a monomer to explore new tungsten oxo alkylidene complexes as initiators for stereoregular ROMP (ring-opening metathesis polymerization). The initiators include MAP (monoaryloxide pyrrolide) oxo alkylidene complexes with the general formula W(O)(CHCMe[subscript 2]Ph)(Me[subscript 2]Pyr)(OAr) (Me[subscript 2]Pyr = 2,5-dimethylpyrrolide, OAr = an aryloxide) and W(O)(CHCMe[subscript 2]Ph)(OR)[subscript 2] (OR = an aryloxide or OC(CF[subscript 3])[subscript 3]), or PPh[subscript 2]Me or CH[subscript 3]CN adducts thereof. We have found that MAP initiators yield cis,syndiotactic-poly(DCMNBD) as a consequence of stereogenic metal control. In contrast, W(O)(CHCMe[subscript 2]Ph)(OR)[subscript 2](L) initiators (where L = PPh[subscript 2]Me or acetonitrile) are strongly biased toward formation of cis,isotactic structures, while W(O)(CHCMe[subscript 2]Ph)(OR)[subscript 2] initiators are strongly biased toward formation of cis,syndiotactic structures. Addition of B(C[subscript 6]F[subscript 5])[subscript 3] to W(O)(CHCMe[subscript 2]Ph)(Me[subscript 2]Pyr)(OR) species leads to a dramatic increase in the rate of polymerization and to an increase in the cis,syndiotacticity of the polymer (if not already high), while addition of B(C[subscript 6]F[subscript 5])[subscript 3] to W(O)(CHCMe[subscript 2]Ph)(OR)[subscript 2] initiators leads to a dramatic increase in the rate of polymerization and to the formation of highly cis,syndiotactic polymers. All evidence supports the proposal that 16e W(O)(CHCMe[subscript 2]Ph)(OR)[subscript 2](L) complexes can operate either through loss of L to yield 14e W(O)(CHCMe[subscript 2]Ph)(OR)[subscript 2] species (which yield largely cis,syndiotactic-poly(DCMNBD)) or by directly reacting with DCMNBD to yield an 18e intermediate and largely cis,isotactic-poly(DCMNBD). All polymerizations by W(O)(CHCMe[subscript 2]Ph)(OR)[subscript 2](L) and W(O)(CHCMe[subscript 2]Ph)(OR)[subscript 2] initiators are proposed to operate through some version of chain end control.United States. Dept. of Energy (DE-FG02-86ER13564)National Science Foundation (U.S.) (CHE-1111133