1,719 research outputs found

    An automatic data system for vibration modal tuning and evaluation

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    A digitally based automatic modal tuning and analysis system developed to provide an operational capability beginning at 0.1 hertz is described. The elements of the system, which provides unique control features, maximum operator visibility, and rapid data reduction and documentation, are briefly described; and the operational flow is discussed to illustrate the full range of capabilities and the flexibility of application. The successful application of the system to a modal survey of the Skylab payload is described. Information about the Skylab test article, coincident-quadrature analysis of modal response data, orthogonality, and damping calculations is included in the appendixes. Recommendations for future application of the system are also made

    A CO Survey of Young Planetary Nebulae

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    We report the results of a sensitive survey of young planetary nebulae in the CO J=2-1 line that significantly increases the available data on warm, dense, molecular gas in the early phases of planetary nebula formation. The observations were made using the IRAM 30 m telescope with the 3 by 3 pixel Heterodyne Receiver Array (HERA). The array provides an effective means of discriminating the CO emission of planetary nebulae in the galactic plane from contaminating emission of interstellar clouds along the line of sight. 110 planetary nebulae were observed in the survey and 40 were detected. The results increase the number of young planetary nebulae with known CO emission by approximately a factor of two. The CO spectra yield radial velocities for the detected nebulae, about half of which have uncertain or no velocity measurements at optical wavelengths. The CO profiles range from parabolic to double-peaked, tracing the evolution of structure in the molecular gas. The line widths are significantly larger than on the Asymptotic Giant Branch, and many of the lines show extended wings, which probably result from the effects on the envelopes of high velocity jets.Comment: 29 pages, 2 figures (with multiple panels), to be published in Astrophysical Journal Supplement Serie

    Speech Communication

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    Contains reports on three research projects.National Institutes of Health (Grant 5 RO1 NS04332-13)National Institutes of Health (Grant 1 T32 NS07040-01)Joint Services Electronics Program (Contract DAAB07-75-C-1346

    Zeta-Functions for Non-Minimal Operators

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    We evaluate zeta-functions ζ(s)\zeta(s) at s=0s=0 for invariant non-minimal 2nd-order vector and tensor operators defined on maximally symmetric even dimensional spaces. We decompose the operators into their irreducible parts and obtain their corresponding eigenvalues. Using these eigenvalues, we are able to explicitly calculate ζ(0)\zeta(0) for the cases of Euclidean spaces and NN-spheres. In the NN-sphere case, we make use of the Euler-Maclaurin formula to develop asymptotic expansions for the required sums. The resulting ζ(0)\zeta(0) values for dimensions 2 to 10 are given in the Appendix.Comment: 26 pages, additional reference

    Gauge Independent Trace Anomaly for Gravitons

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    We show that the trace anomaly for gravitons calculated using the usual effective action formalism depends on the choice of gauge when the background spacetime is not a solution of the classical equation of motion, that is, when off-shell. We then use the gauge independent Vilkovisky-DeWitt effective action to restore gauge independence to the off-shell case. Additionally we explicitly evaluate trace anomalies for some N-sphere background spacetimes.Comment: 19 pages, additional references and title chang

    3-D Photoionization Structure and Distances of Planetary Nebulae II. Menzel 1

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    We present the results of a spatio-kinematic study of the planetary nebula Menzel 1 using spectro-photometric mapping and a 3-D photoionization code. We create several 2-D emission line images from our long-slit spectra, and use these to derive the line fluxes for 15 lines, the Halpha/Hbeta extinction map, and the [SII] line ratio density map of the nebula. We use our photoionization code constrained by these data to derive the three-dimensional nebular structure and ionizing star parameters of Menzel 1 by simultaneously fitting the integrated line intensities, the density map, and the observed morphologies in several lines, as well as the velocity structure. Using theoretical evolutionary tracks of intermediate and low mass stars, we derive a mass for the central star of 0.63+-0.05 Msolar. We also derive a distance of 1050+_150 pc to Menzel 1.Comment: To be published in ApJ of 10th February 2005. 12 figure

    Analytical Estimate of the Critical Velocity for Vortex Pair Creation in Trapped Bose Condensates

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    We use a modified Thomas-Fermi approximation to estimate analytically the critical velocity for the formation of vortices in harmonically trapped BEC. We compare this analytical estimate to numerical calculations and to recent experiments on trapped alkali condensates.Comment: 12 page

    We must become gatekeepers : editing indigenous writing

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    With the proliferation of Indigenous texts currently published by specialist and mainstream publishers, non-Indigenous editors increasingly find themselves negotiating the uncomfortable territories of race, politics and power for which current training (in an Australian context) leaves them poorly prepared. Indigenous writer Anita Heiss advocates the employment of Indigenous editors as an \u27ideal\u27 solution, though few are currently working in the Australian industry. Margaret McDonell, an experienced non-Indigenous editor of Indigenous texts, suggests non-Indigenous editors need to \u27undertake a journey of learning\u27 during which \u27assumptions, biases, tastes and preconceptions\u27 are examined. Yet this presents a difficult task within a postcolonial society, when, as identified by Clare Bradford, even the classification of texts into genres such as fiction and the short story represents an entirely Eurocentric construct, \u27not readily correspond[ing] with Aboriginal schemata\u27. The Australian Society of Authors\u27 discussion paper \u27Writing about Indigenous Australia: Some Issues to Consider and Protocols to Follow\u27 provides practical guidelines that may be adapted for editorial use. This article canvasses these and other ideas with a focus on establishing an ethical and appropriately sensitive cross-cultural approach to editing Indigenous writing.<br /

    Estimation of capture probabilities using generalized estimating equations and mixed effects approaches

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    Modeling individual heterogeneity in capture probabilities has been one of the most challenging tasks in capture-recapture studies. Heterogeneity in capture probabilities can be modeled as a function of individual covariates, but correlation structure among capture occasions should be taking into account. A proposed generalized estimating equations (GEE) and generalized linear mixed modeling (GLMM) approaches can be used to estimate capture probabilities and population size for capture-recapture closed population models. An example is used for an illustrative application and for comparison with currently used methodology. A simulation study is also conducted to show the performance of the estimation procedures. Our simulation results show that the proposed quasi-likelihood based on GEE approach provides lower SE than partial likelihood based on either generalized linear models (GLM) or GLMM approaches for estimating population size in a closed capture-recapture experiment. Estimator performance is good if a large proportion of individuals are captured. For cases where only a small proportion of individuals are captured, the estimates become unstable, but the GEE approach outperforms the other methods
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