65,266 research outputs found

    Structural parameters for globular clusters in M31 and generalizations for the fundamental plane

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    The structures of globular clusters (GCs) reflect their dynamical states and past histories. High-resolution imaging allows the exploration of morphologies of clusters in other galaxies. Surface brightness profiles from new Hubble Space Telescope observations of 34 globular clusters in M31 are presented, together with fits of several different structural models to each cluster. M31 clusters appear to be adequately fit by standard King models, and do not obviously require alternate descriptions with relatively stronger halos, such as are needed to fit many GCs in other nearby galaxies. The derived structural parameters are combined with corrected versions of those measured in an earlier survey to construct a comprehensive catalog of structural and dynamical parameters for M31 GCs with a sample size similar to that for the Milky Way. Clusters in M31, the Milky Way, Magellanic Clouds, Fornax dwarf spheroidal and NGC 5128 define a very tight fundamental plane with identical slopes. The combined evidence for these widely different galaxies strongly reinforces the view that old globular clusters have near-universal structural properties regardless of host environment.Comment: AJ in press; 59 pages including 16 figure

    SCREENING OF PHYTOPHAGOUS INSECTS FOR BIOLOGICAL CONTROL OF WEEDS

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    It is necessary to demonstrate the host specificity of an exotic phytophagous insect before introducing it for the biological control of a weed. The widely-used "starvation test" made on economic plants is considered inadequate for this purpose and we propose that studies should be broadened to include the following: (1) study of the insect's biology, including host-plant records, with particular attention to adaptations likely to restrict the host range, (2) review of the plants attacked by related insects, (3) determination of the laboratory host range of the insect, (4) investigation of the chemical or physical basis of host-plant recognition, (5) starvation tests on economic plants to confirm the limits of the previously established host range, (6) establishment of the insects' potential effectiveness for weed control. A limited amount of feeding on economic plants in the laboratory is not reason for rejection, if other criteria show the insect has a high degree of specificit

    Lunar surface exploration by satellite. An integrated experiment package to perform measurements of the composition of the lunar surface Final report

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    Integrated experiment package to measure lunar surface composition - gamma ray, alpha particle, X ray fluorescence, and neutron albedo experiment

    Analytical and experimental investigation of a 1/8-scale dynamic model of the shuttle orbiter. Volume 1: Summary report

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    A 1/8-scale structural dynamics model of the space shuttle orbiter was analyzed using the NASA Structural Analysis System (NASTRAN). Comparison of the calculated eigenvalues with preliminary test data for the unrestrained condition indicate that the analytical model was consistently stiffer, being about 20% higher in the first mode. The eigenvectors show reasonably good agreement with test data. A series of analytical and experimental investigations undertaken to resolve the discrepancy are described. Modifications in the NASTRAN model based upon these investigations resulted in close agreement for both eigenvalues and eigenvectors

    Creep Evaluation of (Orthotic) Cast Materials During Simulated Clubfoot Correction

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    The Ponseti method is a widely accepted and highly successful conservative treatment of pediatric clubfoot that relies on weekly manipulations and cast applications. However, the material behavior of the cast in the Ponseti technique has not been investigated. The current study sought to characterize the ability of two standard casting materials to maintain the Ponseti corrected foot position by evaluating creep response. A dynamic cast testing device (DCTD) was built to simulate a typical pediatric clubfoot. Semi-rigid fiberglass and rigid fiberglass casting materials were applied to the device, and the rotational creep was measured at various constant torques. The movement was measured using a 3D motion capture system. A 2-way ANOVA was performed on the creep displacement data at a significance level of 0.05. Among cast materials, the rotational creep displacement was found to be significantly different (p-values ≪ 0.001). The most creep displacement occurs in the semi-rigid fiberglass (approximately 1.0 degrees), then the rigid fiberglass (approximately 0.4 degrees). There was no effect of torque magnitude on the creep displacement. All materials maintained the corrected position with minimal change in position over time

    Managing rapport in intercultural business interactions: a comparison of two Chinese-British welcome meetings

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    This paper explores the management of rapport in intercultural business interactions. It compares two Chinese-British business welcome meetings that were held by the same British company. Despite many similarities between the two meetings, both the British and the Chinese were very satisfied with the first meeting, while the Chinese were very annoyed by the second. This paper describes the similarities and differences between the two meetings, and explores why they were evaluated so differently. It argues that research into the management of relations in intercultural communication needs to use a broader analytic framework than is typical of intercultural discourse research, and that it needs to gather a wider range of data types

    Analysis of a Very Massive DA White Dwarf via the Trigonometric Parallax and Spectroscopic Methods

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    By two different methods, we show that LHS 4033 is an extremely massive white dwarf near its likely upper mass limit for destruction by unstable electron captures. From the accurate trigonometric parallax reported herein, the effective temperature (T=10,900 K) and the stellar radius (R=0.00368 R_sun) are directly determined from the broad-band spectral energy distribution -- the parallax method. The effective temperature and surface gravity are also estimated independently from the simultaneous fitting of the observed Balmer line profiles with those predicted from pure-hydrogen model atmospheres -- the spectroscopic method (T=10,760 K, log g=9.46). The mass of LHS 4033 is then inferred from theoretical mass-radius relations appropriate for white dwarfs. The parallax method yields a mass estimate of 1.310--1.330 M_sun, for interior compositions ranging from pure magnesium to pure carbon, respectively, while the spectroscopic method yields an estimate of 1.318--1.335 M_sun for the same core compositions. This star is the most massive white dwarf for which a robust comparison of the two techniques has been made.Comment: 17 pages, including 4 figures, Accepted for Ap.

    A "partitioned leaping" approach for multiscale modeling of chemical reaction dynamics

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    We present a novel multiscale simulation approach for modeling stochasticity in chemical reaction networks. The approach seamlessly integrates exact-stochastic and "leaping" methodologies into a single "partitioned leaping" algorithmic framework. The technique correctly accounts for stochastic noise at significantly reduced computational cost, requires the definition of only three model-independent parameters and is particularly well-suited for simulating systems containing widely disparate species populations. We present the theoretical foundations of partitioned leaping, discuss various options for its practical implementation and demonstrate the utility of the method via illustrative examples.Comment: v4: 12 pages, 5 figures, final accepted version. Error found and fixed in Appendi

    Stable isotope studies on granulites from the high grade terrain of Southern India

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    Fluid inclusion and petrologic characteristics of South India granulites and their bearing on the sources of metamorphic fluids are discussed. This paper served as a review and an introduction to the next paper by D. Jackson. Jackson presented carbon isotope data from gases extracted from fluid inclusions in South Indian granulites. The uniformly low Delta C-13 values (minus 10 plus or minus 2 per mil) and the greater abundance of CO2 in the incipient charnockites are suggestive of fluid influx from an externally buffered reservoir
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