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.     

Novel design for high-power single-lateral-mode lasers

A new laser design for single-mode high-power applications is reported. The waveguide is a laterally flaring and transversely tapering GaAs buried ridge fabricated by selective area epitaxy. Single-lateral-mode powers of 200 mW were achieved     

Bücherschau

Ohne Zusammenfassung VDI     

A fiber-optic hydrophone with a mechanical anti-aliasing filter

Two fiber-optic hydrophones which use high birefringence fiber have been constructed and tested. The hydrophone sensitivity, as determined by optical interferometry, was 93.5 mrad/Pa at 100 Hz. One of the hydrophones tested had an integral low-pass filter which had a break point near 200 Hz and a measured roll-off of 26 dB/octave. This hydrophone transducer is a prototype device for a class of sensors that can be optically sampled. Fiber sensors that are optically sampled require mechanical anti-aliasing filters to remove high frequency components. Optical frequency multiplexing of a number of fiber sensors which are connected in series is expected to be an important application for this type of sensor.     

Selection of catalytically active biotin ligase and trypsin mutants by phage display

Phage display has been shown to facilitate greatly the selectionof polypeptides with desired properties by establishing a directlink between the polypeptide and the gene that encodes it. However,selection for catalytic activities displayed on phage remainsa challenge, since reaction products diffuse away from the enzymeand make it difficult to recover catalytically active phage–enzymes.We have recently described a selection methodology in whichthe reaction substrate (and eventually the reaction product)is anchored on calmodulin-tagged phage–enzymes by meansof a calmodulin binding peptide. Phage displaying a catalyticactivity are physically isolated by means of affinity reagentsspecific for the product of reaction. In this study, we investigatedthe efficiency of selection for catalysis by phage display,using a ligase (the Escherichia coli biotin ligase BirA) andan endopeptidase (the rat trypsin His57