Eclipsing binaries in open clusters

Accurate physical parameters have been determined for two early-type detached eclipsing binaries in the open cluster h Persei (NGC 869). Masses accurate to 1.5% are derived from high-resolution spectroscopy and radii accurate to 4--6% have been obtained from fitting the existing light curves. The four stars are placed in the mass radius plane and compared to the theoretical stellar models of the Granada Group. The best-fitting models have a low metallicity of approximately Z=0.01 and a high helium abundance of Y=0.34. This is the first determination of the bulk metallicity of the Perseus Double Cluster. Recent studies have assumed a solar metallicity so their results should be reviewed.Comment: 4 pages, 5 figures. To appear in Spectroscopically and Spatially Resolving the Components of Close Binary Stars, ASP Conf. Series, 200

Synthesis of the Beryllium 3131A Spectral Region

The Beryllium spectral region of the Sun, Procyon and 4 stars in the open cluster NGC6633 up to Teff = 7500K have been synthesised using ATLAS9 model atmospheres and the MOOG spectral synthesis program. The line list used for these syntheses has been modified from the ATLAS9 line list to improve the quality of the fits in light of the improved opacities in the new version of the MOOG code. Significant changes have been made to the Mn I line at ATLAS9 wavelength 3131.037A and an OH line has been added at 3131.358A. In addition there are a number of minor changes to gf-values throughout the synthesised region thus improving the fit for the spectra across the temperature range considerably.Comment: 4 pages, 3 figures. To appear in the proceedings of the Workshop "ATLAS 12 and related codes", Trieste, July 11-15, 200

Subsynchronous vibrations in a high pressure centrifugal compressor: A case history

Two distinct aerodynamically excited vibrations in a high pressure low flow centrifugal compressor are documented. A measured vibration near 21% of running speed was identified as a nonresonant forced vibration which results from rotating stall in the diffuser; a measured vibration near 50% of running speed was identified as a self excited vibration sustained by cross coupling forces acting at the compressor wheels. The dependence of these characteristics on speed, discharge pressure, and changes in bearing design are shown. The exciting mechanisms of diffuser stall and aerodynamic cross coupling are evidenced. It is shown how the rotor characteristics are expected to change as a result of modifications. The operation of the compressor after the modifications is described

The UV absorption spectrum of C60 (buckminsterfullerene): A narrow band at 3860 Å

The absorption spectrum of the special C60 cluster buckminsterfullerene has been studied in a supersonic beam by laser depletion of the cold van der Waals complexes of C60 with benzene and methylene chloride. Both complexes were found to display a single, isolated absorption band in the near ultraviolet superimposed on a structureless absorption continuum. For the methylene chloride complex this feature is centered at 3860 Å, and is roughly 50 cm−1 wide. In the benzene van der Waals cluster, the corresponding feature is located at 3863 Å, and has a similar width. This spectrum is tentatively assigned to the 0–0 band of the lowest 1T1u<--1Ag (LUMO+1<--HOMO) transition of a truncated icosahedral carbon shell structure, broadened by coupling to the underlying quasicontinuum of ground state vibrational levels

\u3ci\u3eDendroctonus Valens\u3c/i\u3e and \u3ci\u3eHylastes Porculus\u3c/i\u3e (Coleoptera: Scolytidae): Vectors of Pathogenic Fungi (Ophiostomatales) Associated With Red Pine Decline Disease.

A study was conducted to determine whether Dendroctonus valens and Hylastes porculus could vector their commonly associated fungi to red pine. Field collected adult D. valens transmitted Leptographium terebrantis, Leptographium procerum and Ophiostoma ips into 45%, 30%, and 5%, respectively of the wounded red pine roots onto which they were caged. Field collected H. porculus transmitted L. terebrantis, L. procerum and O. ips into 55%, 40%, and 5%, respectively, of the wounded red pine roots onto which beetles were caged. None of the control roots, which were mechanically wounded only, were found to contain O. ips, whereas only one control root contained L. terebrantis and only one control root contained L. procerum. This work demonstrates that D. valens and H. porculus can vector their associated Leptographium fungi to red pine trees and that these organisms are likely involved in red pine decline disease

Effects of Feeding by Two Folivorous Arthropods on Susceptibility of Hybrid Poplar Clones to a Foliar Pathogen

We investigated variation in folivore-induced effects on subsequent plant suitability to a foliar pathogen. We used a leaf disk assay to expose three clones of hybrid poplar, NC11382, NE332 and NM6, to colonization by a leaf spot pathogen, Septoria musiva. Undamaged leaf disks of NE332 were the most resistant to S. musiva, followed by NM6 and NC11382, respectively. To test the effects of prior herbivory on subsequent susceptibility to this fungal pathogen, we inoculated S. musiva on leaf disks taken from leaves which had been exposed to feeding by Tetranychus mites or cottonwood leaf beetles. Prior activity by mites and cottonwood leaf beetle affected the subsequent susceptibility of clones NC 11382 and NE332 to S. musiva

A renormalization group model for the stick-slip behavior of faults

A fault which is treated as an array of asperities with a prescribed statistical distribution of strengths is described. For a linear array the stress is transferred to a single adjacent asperity and for a two dimensional array to three ajacent asperities. It is shown that the solutions bifurcate at a critical applied stress. At stresses less than the critical stress virtually no asperities fail on a large scale and the fault is locked. At the critical stress the solution bifurcates and asperity failure cascades away from the nucleus of failure. It is found that the stick slip behavior of most faults can be attributed to the distribution of asperities on the fault. The observation of stick slip behavior on faults rather than stable sliding, why the observed level of seismicity on a locked fault is very small, and why the stress on a fault is less than that predicted by a standard value of the coefficient of friction are outlined