Cure kinetics of ring-opening metathesis polymerization of dicyclopentadiene

The cure kinetics of polydicyclopentadiene (pDCPD) prepared by ring-opening metathesis polymerization with three different concentrations of Grubbs' catalyst was examined using differential scanning calirimetry (DSC). The experimental data were used to test several different phenomenological kinetic models. The data are best modeled with a "model-free" isoconversional method. This analysis reveals that the activation energy increases significantly for degree of cure greater than 60%. Catalyst concentration is shown to have a large effect on the cure kinetics.published or submitted for publicationis peer reviewe

Near-Infrared Spectroscopy of the Bright Kuiper Belt Object 2000 EB173

We have obtained a near-infrared spectrum of the bright Kuiper Belt object 2000 EB173; the spectrum appears featureless. The spectrum has a sufficient signal-to-noise ratio to rule out the 1.5 and 2.0 μm absorption from water ice even at the low level seen in the Centaur Chariklo. In addition, we can rule out a 2.3 μm absorption at the level seen in the Centaur Pholus

Center for bioplastics and biocomposites: Bringing INDUSTRY and UNIVERSITIES together to develop new biobased products and technologies

The Center for Bioplastics and Biocomposites (CB2) is a NSF Industry & University Cooperative Research Center that brings together industry partners and university researchers who have a common interest in biobased plastics and composites. CB2 is developing the knowledge that will allow the production of high-value products from sustainable agricultural and forestry feedstocks that are compatible with current industrial manufacturing systems. CB2 is focused on six research areas that will promote industry-wide acceptance of bioplastics and biocomposites and increase the use of sustainable materials: synthesis and compounding, processing, biocomposites, medical applications, biobased products, and modeling. Companies, commodity boards, and other organizations interested in the market introduction of economically viable biobased products are encouraged to join CB2 and its 25 industry partners. Becoming a member has many advantages including leveraging research efforts through the center’s projects and early access to technologies developed by the center. Membership allows organizations to vote on project selection. CB2 is a collaborative effort by Iowa State University and Washington State University. These universities provide significant expertise in feedstock production, polymer processing, and natural fiber polymer composites

Hummingbird diversity, food niche characters, and assemblage composition along a latitudinal precipitation gradient in the Bolivian lowlands

As for many other taxa, hummingbird diversity declines away from the equator, but the causes for this decline are still disputed and might involve, among others, climatic factors or the availability of food resources. Because hummingbirds are one of the classical examples for plant-animal coevolution, it has been proposed that the diversity of hummingbird assemblages might depend on the diversity of food plants available. We tested this hypothesis by studying the hummingbird assemblages and their food plants for 1year at six sites along a 660-km-long transect in Bolivian lowland forests extending from the southernmost Amazonian rain forests to dry Chaco forests. Hummingbird diversity was higher in the northern three sites as compared to the southern ones, with an abrupt decline in species numbers and a corresponding change in taxonomic composition at the boundary from evergreen to drought deciduous forests. Hummingbird diversity and abundance were only weakly correlated to climatic factors or to the diversity of humming-visited flowers, but strongly to the seasonal abundance of flowers. The overlap in nectar diet between hummingbird species depended on the number of plant species: when numerous species were available, the hummingbirds segregated by feeding preferences, but when few flowers were available, all hummingbirds fed on the same plants. We conclude that the local diversity of hummingbird species is not primarily determined by the diversity of food plants, but rather by the abundance of flowers available at any given point in tim

In situ poly(urea-formaldehyde) microencapsulation of dicyclopentadiene

Microencapsulated healing agents that possess adequate strength, long shelf-life, and excellent bonding to the host material are required for self-healing materials. Ureaformaldehyde microcapsules containing dicyclopentadiene were prepared by in situ polymerization in an oil-in-water emulsion that meet these requirements for self-healing epoxy. Microcapsules of 10-1000 ??m in diameter were produced by appropriate selection of agitation rate in the range of 200-2000 rpm. A linear relation exists between log(mean diameter) and log(agitation rate). Surface morphology and shell wall thickness were investigated by optical and electron microscopy. Microcapsules are composed of a smooth 160-220 nm inner membrane and a rough, porous outer surface of agglomerated urea-formaldehyde nanoparticles. Surface morphology is influenced by pH of the reacting emulsion and interfacial surface area at the core-water interface. High yields (80-90%) of a free flowing powder of spherical microcapsules were produced with a fill content of 83-92 wt% as determined by CHN analysis.published or submitted for publicationis peer reviewe

Ascogrammitis lehnertii (Polypodiaceae): a new and dominant understory-species from a diverse community of grammitid ferns in the Andes of Ecuador

In the scope of pantropical studies aimed at understanding how the diversity of grammitid ferns (Polypodiaceae) has evolved and is maintained, we studied a diverse grammitid community in treeline elfin forests in eight study plots of 400 m2 each at 3200 m on Cerro Toledo, Loja, southern Ecuador.Werecorded a total of 7986 individuals of 16 grammitid species. Ascogrammitis lehnertii is here described as a newspecies.We also recorded Mycopteris leucosticta, a species previously believed to be restricted to the Choc´o region of Ecuador. We found that the grammitid species were segregated by habitat into trunk-base and trunk specialists, which suggests that species coexistence in these diverse epiphytic communities is at least partly linked to habitat segregation. Ascogrammitis lehnertii and M. leucosticta were the second and third most abundant species, respectively, and both were mostly trunk-base species. The new species A. lehnertii differs from its congeners by the combination of its relatively broad lamina, (2–)3–4 cmwide, fertile leaves bearing 2mmlong reddish setae in and near the sori, and by bearing proliferous roots from which new plants emerge. Phylogenetic analyses of atpß, rbcL, rps4, trnG-trnR, andtrnL-trnFDNAmolecular sequences, usingmaximum likelihood, place A. lehnertii as sister to A. cuencana with strong support. Despite previous intensive collection efforts in Loja for the past 30 yr, all but one of the collections of this new species were made in the last three years. The discovery of A. lehnertii and the new record of M. leucosticta highlight the patchy distribution of some species in the Andes and the value of surveying

Influence of niche characteristics and forest type on fern species richness, abundance and plant size along an elevational gradient in Costa Rica

An analysis of the fern vegetation on 156 plots along an elevational gradient (45-3400m) in undisturbed forests in Costa Rica, Central America, showed a hump-shaped pattern of species richness with a maximum of up to 68 species per 400m² at mid-elevations. This study documents the contribution of specific habitats (forest types: ridges, ravines) and niches within them (dead wood, rocks, growth zones in trees) to the local fern richness and the relation of species richness to elevation and climatic variables. Forests along ravines showed significantly higher species richness, presumably caused by high environmental humidity. The mean number of individuals of occupied niches per species increased significantly with elevation, suggesting that the niche breadth of species increased and that the differentiation of niches decreased with elevation. Both findings may explain the reduced fern species richness towards and above the upper treeline, but not at low elevations. The key factors for the decreases of species richness at the extremes of the gradient are likely to involve climatic condition