Applying the principle of corresponding states to multi-component hydrocarbon mixtures (jet fuels)

Aviation turbine fuel is required to meet stringent product specifications due the critical importance it plays inside of the turbines during the fuel\u27s use. The specification tests for military and commercial grades of jet fuel include over twenty individual analyses, which are costly in both time and money. In addition, these specifications were designed for petroleum derived fuels and are not always applicable to new finished fuels from alternative sources. For these reasons, it is desirable to develop tools to assess a broad range of jet fuel properties based on the underlying chemical composition. This work outlines a methodology to predict two fuel properties, i.e., density and viscosity, using a theoretical model called generalized corresponding states (GCSP), a subset of the corresponding states principal (CSP). The work analyzes different methods to calculate the critical properties of the mixture\u27s components. The components are of vital importance to GCSP. It also investigates reference fluids of the system, which is another important factor in modelling with GCSP. Results for the separate physical parameters, using an initial set of over 50 jet fuels, indicates model predictions fall within an average error range that spans from 0.01% to 7.29%, and is strongly dependent on the critical properties and reference fluids used. Additional improvements to current models and methods are proposed

Phylogeny, Phenology, and Foraging Breadth of<i>Ashmeadiella</i>(Hymenoptera: Megachilidae)

AbstractAshmeadiella Cockerell (Megachilidae: Osmiini) is a bee genus endemic to North America, with greatest richness in arid and Mediterranean regions of the southwestern United States. Species relationships of Ashmeadiella were last analyzed in the 1950s, when Robert Sokal and Charles Michener developed a novel statistical clustering method for classification called numerical taxonomy. To revisit the taxonomic groups they established, we built a molecular phylogeny including all five subgenera. Furthermore, we assembled life history data to lay the foundation for future conservation programs for these bees. We chose three aspects of bee biology that can inform conservation strategies: documenting periods of the year adult bees are flying, assembling data for the flowers each species visits, and compiling the localities and ecoregions where each species is reported. Our results suggest that some Ashmeadiella species may need to be synonymized and that the subgenera should be revised due to non-monophyly. We therefore propose synonymizing the subgenera Cubitognatha and Chilosima with Arogochila. Biological data from published collection records reveal that adult flight periods range from a few months to 11 mo; most species utilize floral resources from multiple plant families; and, over half of the species have ranges extending into the Mojave Desert.</jats:p

Secondary pollen presentation and the temporal dynamics of stylar hair retraction and style elongation in Campanula trachelium

To increase the accuracy of pollen capture and transfer by pollinators some plant species have developed secondary pollen presentation structures. Because the presence of secondary pollen presentation structures at the pistil may reduce the spatial separation between the sexual functions and increase the risk of self-interference and selfing, temporal segregation of the sexual organs, triggered by visiting insects, can be expected to occur. We investigated secondary pollen presentation and the temporal dynamics of the sexual phases in combination with the physiologcal self-incompatibility system in Campanula trachelium, a protandrous insect-pollinated herb. Stylar hair retraction (male function) and curling of the stigmatic lobes (female function) were modelled using Gompertz growth functions. Finally, we performed pollination experiments in the lab and field to assess seed set and pollen limitation under natural conditions. About 68% of the total pollen load was captured by stylar hairs. Manual manipulation of the stylar hairs, mimicking pollinator visitation, significantly shortened the male phase and accelerated the female phase, resulting in a significant decline in temporal overlap between the two sexual functions. Conversely, when pollinators and/or manual manipulations were lacking, the male phase was substantially prolonged and sexual overlap was maximal. This suggests that spreading of the sexual phases and thus the risk of sexual interference are largely determined by the interaction between stylar hairs and visiting pollinators. Natural seed set was high and not pollinator limited. Overall, these results indicate that secondary pollen presentation and partial protandry resulted in efficient pollen capture, transfer and deposition