995 research outputs found

    Conclusion of Viking Lander Imaging Investigation: Picture catalog of experiment data record

    Get PDF
    The images returned by the two Viking landers during the Viking Survey Mission are presented in this report. Listing of supplemental information which describe the conditions under which the images were acquired are included. Subsets of the images are listed in a variety of sequences to aid in locating images of interest. The format and organization of the digital magnetic tape storage of the images are described. A brief description of the mission and the camera system is also included

    Composite Operators in QCD

    Full text link
    We give a formula for the derivatives of a correlation function of composite operators with respect to the parameters (i.e., the strong fine structure constant and the quark mass) of QCD in four-dimensional euclidean space. The formula is given as spatial integration of the operator conjugate to a parameter. The operator product of a composite operator and a conjugate operator has an unintegrable part, and the formula requires divergent subtractions. By imposing consistency conditions we derive a relation between the anomalous dimensions of the composite operators and the unintegrable part of the operator product coefficients.Comment: 26 page

    The Delphi method: methodological issues arising from a study examining factors influencing the publication or non-publication of mental health nursing research

    Get PDF
    Purpose – The paper describes how the classic Delphi method can be adapted and structured to ensure that specific research questions are clearly addressed. Design/methodology/approach – As part of a larger mixed method project, a modified Delphi study was undertaken to explore factors influencing publication and non-publication of mental health nursing research. Findings - This paper reports brief findings from the Delphi study. However, its main focus is the methodological issues arising from the Delphi method. Implications - The paper argues that the classic Delphi method can be adapted and structured to ensure that specific research questions are able to be clearly answered. The adaptations are pragmatic in approach and in keeping with the general principles underpinning the Delphi method, while successfully addressing the problems of attrition and previous criticism of homogenous panels. Originality/value - This paper offers some practical solutions to issue arising from undertaking research using the Delphi method

    Grain sorting in the morphological active layer of a braided river physical model.

    Get PDF
    A physical scale model of a gravel-bed braided river was used to measure vertical grain size sorting in the morphological active layer aggregated over the width of the river. This vertical sorting is important for analyzing braided river sedimentology, for numerical modeling of braided river morphodynamics, and for measuring and predicting bedload transport rate. We define the morphological active layer as the bed material between the maximum and minimum bed elevations at a point over extended time periods sufficient for braiding processes to rework the river bed. The vertical extent of the active layer was measured using 40 hourly high-resolution DEMs (digital elevation models) of the model river bed. An image texture algorithm was used to map bed material grain size of each DEM. Analysis of the 40 DEMs and texture maps provides data on the geometry of the morphological active layer and variation in grain size in three dimensions. By normalizing active layer thickness and dividing into 10 sublayers, we show that all grain sizes occur with almost equal frequency in all sublayers. Occurrence of patches and strings of coarser (or finer) material relates to preservation of particular morpho-textural features within the active layer. For numerical modeling and bedload prediction, a morphological active layer that is fully mixed with respect to grain size is a reliable approximation

    The Thermal Stability of Mass-Loaded Flows

    Full text link
    We present a linear stability analysis of a flow undergoing conductively-driven mass-loading from embedded clouds. We find that mass-loading damps isobaric and isentropic perturbations, and in this regard is similar to the effect of thermal conduction, but is much more pronounced where many embedded clumps exist. The stabilizing influence of mass-loading is wavelength independent against isobaric (condensing) perturbations, but wavelength dependent against isentropic (wave-like) perturbations. We derive equations for the degree of mass-loading needed to stabilize such perturbations. We have also made 1D numerical simulations of a mass-loaded radiative shock and demonstrated the damping of the overstability when mass-loading is rapid enough.Comment: 4 pages, 1 figure, to be published in A&

    An Approach for Developing National Guidelines for Postsecondary Support Services Programs

    Get PDF
    This paper presents a case for developing standards for specialized support programs serving deaf students in postsecondary institutions. A step-by-step plan for producing standards for the evaluation, development, and accreditation of these programs is outlined. Criteria for forming flexible standards which (1) account for variations in program size and type and (2) enhance support services which make postsecondary education more accessible for deaf students are clarified. The importance of teamwork between postsecondary specialists and generalists to link standards for special service programs to the process of accrediting regular institutions of higher education is emphasized. An example of accrediting a special college for deaf students is discussed. Results from a process of setting priorities for future actions in developing program standards which emerged from a professional conference are reported. Expected benefits of these standards to enhancing program quality are described

    Dust in Interstellar Clouds, Evolved Stars and Supernovae

    Full text link
    Outflows of pre-main-sequence stars drive shocks into molecular material within 0.01 - 1 pc of the young stars. The shock-heated gas emits infrared, millimeter and submillimeter lines of many species including. Dust grains are important charge carriers and play a large role in coupling the magnetic field and flow of neutral gas. Some effects of the dust on the dynamics of oblique shocks began to emerge in the 1990s. However, detailed models of these shocks are required for the calculation of the grain sputtering contribution to gas phase abundances of species producing observed emissions. We are developing such models. Some of the molecular species introduced into the gas phase by sputtering in shocks or by thermally driven desorption in hot cores form on grain surfaces. Recently laboratory studies have begun to contribute to the understanding of surface reactions and thermally driven desorption important for the chemistry of star forming clouds. Dusty plasmas are prevalent in many evolved stars just as well as in star forming regions. Radiation pressure on dust plays a significant role in mass loss from some post-main-sequence stars. The mechanisms leading to the formation of carbonaceous dust in the stellar outflows are similar to those important for soot formation in flames. However, nucleation in oxygen-rich outflows is less well understood and remains a challenging research area. Dust is observed in supernova ejecta that have not passed through the reverse shocks that develop in the interaction of ejecta with ambient media. Dust is detected in high redshift galaxies that are sufficiently young that the only stars that could have produced the dust were so massive that they became supernovae. Consequently, the issue of the survival of dust in strong supernova shocks is of considerable interest.Comment: 4 pages, to be published in the proceedings of Fifth International Conference on Physics of Dusty Plasma

    Master integrals for the two-loop light fermion contributions to gg→Hgg \to H and H→γγH \to \gamma\gamma

    Get PDF
    We give the analytic expressions of the eight master integrals entering our previous computation of two-loop light fermion contributions to gg→Hgg \to H and H→γγH \to \gamma\gamma. The results are expressed in terms of generalized harmonic polylogarithms with maximum weight four included.Comment: 9 pages, 6 figure

    Renormalization Group Improvement of the Effective Potential in Massive O(N) Symmetric ϕ4\phi^4 Theory

    Full text link
    The renormalization group is used to improve the effective potential of massive O(N){\rm O}(N) symmetric ϕ4\phi^4 theory. Explicit results are given at the two-loop level.Comment: 8pages, no figures, plain Latex, UCLA/92/TEP/26. (equation 9 corrected, results unchanged
    • 

    corecore