995 research outputs found
Conclusion of Viking Lander Imaging Investigation: Picture catalog of experiment data record
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
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
Purpose â 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 â 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.
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
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
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
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 and
We give the analytic expressions of the eight master integrals entering our
previous computation of two-loop light fermion contributions to and
. 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 Theory
The renormalization group is used to improve the effective potential of
massive symmetric 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
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