Identification of the Trail Pheromone of the Pavement Ant Tetramorium immigrans (Hymenoptera: Formicidae)

Journal of Chemical Ecology - Four species of Tetramorium pavement ants are known to guide foraging activities of nestmates via trail pheromones secreted from the poison gland of worker ants, but...     

Multiscale analysis of the urbanization pattern of the Phoenix metropolitan landscape of USA: Time,space and thematic resolution

Investigating the ecological consequences of urbanization require knowledge of land-cover dynamics. Quantification of land-use/land-cover change in Phoenix, Arizona during the period of 1985–2005 using landscape metrics computed from Landsat-derived maps revealed temporal patterns of landscape composition and configuration. With accelerated urbanization the landscape as a whole became more fragmented ecologically and more complex compositionally and geometrically. However, the majority of individual patches became more compact in shape. Urban land covers, especially xeric residential, increased substantially and the desert decreased by 20%. Spatial and thematic resolution of data was shown to have large effects on the analysis of land-cover pattern. Our results, while agreeing in general with previously reported scaling relations with respect to changing spatial grain and extent, showed that scaling relations are also robust and consistent across thematic resolutions and time periods. Some metrics behaved unpredictably and some exhibited scale-free behavior. Compositional metrics, such as patch density, diversity, evenness, and largest patch index, were well correlated with vegetative cover, its spatial variation, and population density. Many of these correlations exhibited hump-shaped patterns with respect to increasing grain size, indicating a characteristic scale at approximately 500–1000 m. By simultaneously manipulating spatial and thematic resolutions, the importance of the Modifiable Area Unit Problem in relating landscape patterns to vegetation and socio-economic variables was also demonstrated. Additionally, highly variable desert vegetation due to precipitation variability poses a challenge for accurately quantifying urbanization pattern in arid environments. Choosing appropriate spatial, temporal and thematic resolutions is essential in meeting this challenge.     

What Have We Not Learned about Teaching Programming?

We need to look seriously at how we teach programming. The purpose of an education should not simply be to pour facts into students, but rather to teach them to think. The topics we need to teach more effectively include correctness concerns; the program development process, not only simplifying but also not "complifying" in the first place; how notation can help or hinder; problem solving; and how to find bugs     

A proof technique for communicating sequential processes

Summary Proof rules are presented for an extension of Hoare's Communicating Sequential Processes. The rules deal with total correctness; all programs terminate in the absence of deadlock. The commands send and receive are treated symmetrically, simplifying the rules and allowing send to appear in guards. Also given are sufficient conditions for showing that a program is deadlock-free. An extended example illustrates the use of the technique.This research was supported in part by the National Science Foundation under grant MCS-7622360.     

Characterisation of potential health promoting lipids in the co-products of de-flossed milkweed

The floss and oil of the common milkweed (Asclepias syriaca L.) seeds are currently used to produce comforters/pillows and skin care products, respectively. As an outcome of these products, copious quantities co-products (pressed seed meal and pod biomass) are disposed of each year despite the presence of potential health benefitting lipids. The objective of this project was to determine the feasibility of developing the lipid fraction from of these co-products for the fast growing dietary human health market. Although certain types of lipids were affected by the extraction solvent used (hexane and diethyl ether) as were overall amounts, analysis of the each extract showed novel lipid profiles with several potential health benefitting agents present at levels comparable to or exceeding those present in other typically consumed dietary oils or food systems (vitamin E, carotenoids, sterols and unsaturated free fatty acids, particularly the both omega 7-fatty acids).     

Molecular beam mass spectrometry and modelling of CH4–CO2 plasmas in relation with polycrystalline and nanocrystalline diamond deposition

CH₄–CO₂ microwave plasmas have been studied by optical emission spectroscopy, microwave interferometry, Langmuir probing and molecular beam mass spectrometry. The variations of plasma parameters and the concentration variations of both stable species and radicals in the plasma had been reported previously as a function of the power density; the influence of the total inlet flow rate is reported here. While the power density influences directly the plasma kinetics, the flow rate changes the residence time in the plasma and then the degree of conversion of the chemical system that is the extent to which the gas composition moves toward its steady-state composition. This is studied by modelling of plasma kinetics taking into account the coupled fluid dynamics of the gaseous species and the gas-phase chemistry including electron dissociation and surface recombination at the reactor wall. The experimental and modelling studies are used for correlating: – the relative concentration of important hydrocarbon radicals and etching radicals in the plasma and the gradients of all these species in front of the surface; – to the deposition domain, the structure (polycrystalline or nanocrystalline) and the quality of diamond films, which is the ratio of sp³ to (sp³ + sp²)-hybridized carbon in the film. All results evidence the plasma kinetic effect on the diamond deposition domain and the diamond deposition quality and structure, due to different degrees of conversion of the chemical system. The deposition of diamond coating from CH₄–CO₂ is shown to be a versatile process that permits deposition of a great variety of diamond films. However it requires particular attention because of the variation of the deposition conditions and then diamond quality and structure of the deposits depending on the extent of conversion of the inlet species to various intermediate and finally stable species formed in the plasma chemical system.     

Two Pheromones of Coniferophagous Bark Beetles Found in the Bark of Nonhost Angiosperms

Volatiles from fresh bark of black cottonwood, Populus trichocarpa; trembling aspen, P. tremuloides; paper birch, Betula papyrifera; bigleaf maple, Acer macrophyllum; red alder, Alnus rubra; and Sitka alder, Alnus viridis, were collected on Porapak Q and subjected to coupled gas chromatographic–electroantennographic detection analyses by utilizing the antennae of several scolytid beetles (Dendroctonus pseudotsugae, D. rufipennis, D. ponderosae, Ips pini, and Dryocoetes confusus). Among the antennally active volatiles identified by coupled gas chromatographic-mass spectroscopic analysis were frontalin, 1,5-dimethyl-6,8-dioxabicyclo[3.2.1]-octane, in the two Alnus species and conophthorin, (E)-7-methyl-1,6-diox-aspiro[4.5]decane, in the other four species. Field trapping experiments demonstrated that conophthorin had a significant disruptant effect on the response to a pheromone-host kairomone blend by both Dendroctonus pseudotsugae and D. ponderosae. Our results, and the recent identification of other scolytid pheromones in various tree species, pose major questions regarding the evolution and ecological roles of these semiochemicals, including the possibility of Batesian mimicry by the beetles. They also suggest a need for comparative studies on the biosynthetic pathways for these compounds.     

Identification of Sex Pheromone Components of Nettle Caterpillar, Setothosea asigna

Gas chromatographic–electroantennographic detection (GC-EAD) analyses of female nettle caterpillar, Setothosea asigna, pheromone gland extracts revealed seven antennally active compounds. Based on their retention indices on three fused silica columns (DB-5, DB-23, and DB-210), these compounds were hypothesized and, through comparative GC, GC-EAD and GC-mass spectrometry with authentic standards, confirmed to be Δ10-undecenal, dodecanal, (E)-9-dodecenal (E9–12:Ald), (Z)-9-dodecenal, (E)-9-dodecen-1-ol, (E)-9,11-dodecadienal (E9,11–12:Ald), and (E)-9,11-dodecadienol. E9–12:Ald and E9,11–12:Ald were most abundant in female S. asigna pheromone extracts. In field trapping experiments in Palembang, Indonesia, synthetic E9–12: Ald and E9,11–12:Ald at a 1:1 ratio, but not singly, attracted S. asigna males. Attractiveness of these two aldehydes could not be enhanced further through the addition of their corresponding alcohols and/or other aldehydic candidate pheromone components. Use of E9–12:Ald and E9,11–12:Ald for pheromone-based monitoring of S. asigna populations will require lure formulations that minimize pheromone degradation by ultraviolet radiation and atmospheric oxidation.     

The 1988-89 Taulbee survey report [education]

Significant findings from the 1988-9 Taulbee report, which is based on a December 1989 survey of the Forsythe list of computing departments, are summarized. The survey focuses on the production and employment of PhDs who graduated in 1988-89 and the faculty of PhD-granting computing departments during the 1989-90 academic year. Among the findings is an 8% increase in PhDs granted. Of the 625 new PhDs, none are black, six are Hispanic, and 87 are women. The 129 CS departments have 2550 faculty members (an increase of 123, or nearly one per department) and reported hiring 204 faculty and losing 161