2,434 research outputs found
GROCERY STORE BUYING BEHAVIOR: EVIDENCE FROM LOYALTY PROGRAM DATA
Consumer/Household Economics,
Detecting Bimodality in Astronomical Datasets
We discuss statistical techniques for detecting and quantifying bimodality in
astronomical datasets. We concentrate on the KMM algorithm, which estimates the
statistical significance of bimodality in such datasets and objectively
partitions data into sub-populations. By simulating bimodal distributions with
a range of properties we investigate the sensitivity of KMM to datasets with
varying characteristics. Our results facilitate the planning of optimal
observing strategies for systems where bimodality is suspected.
Mixture-modeling algorithms similar to the KMM algorithm have been used in
previous studies to partition the stellar population of the Milky Way into
subsystems. We illustrate the broad applicability of KMM by analysing published
data on globular cluster metallicity distributions, velocity distributions of
galaxies in clusters, and burst durations of gamma-ray sources. PostScript
versions of the tables and figures, as well as FORTRAN code for KMM and
instructions for its use, are available by anonymous ftp from
kula.phsx.ukans.edu.Comment: 32 page
Globular cluster systems as clues to galaxy evolution
We investigate the properties of systems of globular clusters in light of the hypothesis that galaxy mergers play a major role in galaxy evolution. In a previous paper, we presented a model in which the formation of globular clusters occurs during galaxy interactions and mergers. We discussed several predictions of the model, including the existence of young globular clusters in currently merging galaxies and the presence of two or more metallicity peaks in the globular clusters systems of normal elliptical galaxies. Here, we present recent observational evidence which supports both of these predictions and suggests that mergers may have a significant influence on the formation and evolution of galaxies and their globular clusters
CONVENIENCE STORE PRACTICES AND PROGRESS WITH EFFICIENT CONSUMER RESPONSE: THE MINNESOTA CASE
The adoption of Efficient Consumer Response (ECR) practices by Minnesota convenience store (C- store) is explained in this study. Data were collected through a mail survey distributed to more than 250 Minnesota C-stores ranging in size from single, independently owned stores to over 100 store chains. The survey instrument was developed to collect data on the following components important to C-store operations and the implementation of ECR: information systems, ordering, receiving, inventory management, and pricing practices. Findings are presented from three distinct perspectives: 1. Location: Rural C-stores, which often meet customer needs that were once met by small supermarkets, carried a wider range of products and offered more services than C-stores in urban and suburban locations. However, rural stores had the lowest adoption rate for practices related to the ECR initiative. Urban chains coordinated business practices with suppliers to a greater degree than suburban and rural chains. 2. Chain size: Larger chains were more likely to have implemented the more costly technological practices than were small chains. This was expected since large chains can spread the fixed costs of ECR adoption over a larger number of stores. Larger chains also cooperated and communicated more with their suppliers than small chains. Again, this was expected, since larger chains can economize on transaction costs involved in maintaining these business relationships. 3. ECR practices: ECR adoption and superior performance were positively related. Having adopted six to nine practices was positively correlated with higher inside and outside sales per square foot of selling area and higher annual inventory turns. However, it was not clear whether there was a causal relationship in either direction between ECR practices and store performance. The C-store industry is changing, as new information technologies, new business practices, and new retail strategies are developed. The results from this survey can serve as a baseline for future research monitoring the adoption of these innovations and assessing their impact on productivity and profitability. Minnesota C-Stores appear to be smaller but more productive than the national average. Overall, it appears ECR is just beginning to impact the Minnesota C-store industry. Nonetheless, regression analyses confirmed ECR practices are positively related to store sales performance and those stores adopting the most practices had higher productivity measures.Industrial Organization, Marketing,
Experimental Studies of NaCs
We present experimental studies of excited electronic states of the NaCs molecule that are currently underway in our laboratory. The optical-optical double resonance method is used to obtain Doppler-free excitation spectra for several excited states. These data are being used to obtain RydbergKlein-Rees (RKR) or Inverse Perturbation Approach (IPA) potential curves for these states. We are also trying to map the bound portion of the 1(a) 3Σ + potential using resolved laser-induced fluorescence and Fourier transform spectroscopy to record transitions into the shallow well. Bound-free spectra from single ro-vibrational levels of electronically excited states to the repulsive wall of the 1(a) 3Σ + state are also being recorded. Using the previously determined excited state potentials, we can fit the repulsive wall of the 1(a) 3Σ + state to reproduce the experimental spectra using LeRoy’s BCONT program. A slightly modified version of BCONT will also be used to fit the relative transition dipole moments, µe(R), as a function of internuclear separation R, for the various bound-free electronic transitions
Some Revised Observational Constraints on the Formation and Evolution of the Galactic Disk
A set of 76 open clusters with abundances based upon DDO photometry and/or
moderate dispersion spectroscopy has been transformed to a common [Fe/H] scale
and used to study the local structure and evolution of the galactic disk. The
metallicity distribution of clusters with R_GC is best described by two
distinct zones. Between R_GC = 6.5 and 10 kpc, the distribution has a mean
[Fe/H] = 0.0 and a dispersion of 0.1 dex; there is only weak evidence for a
shallow abundance gradient over this distance range. Beyond R_GC = 10 kpc, the
metallicity distribution has a dispersion between 0.10 and 0.15 dex, but with a
mean [Fe/H] = -0.3, implying a sharp discontinuity at R_GC = 10 kpc. After
correcting for the discontinuity, no evidence is found for a gradient
perpendicular to the plane. Adopting the clusters interior to 10 kpc as a
representative sample of the galactic disk over the last 7 Gyr, the cluster
metallicity range is found to be about half that of the field stars. When
coupled with the discontinuity in the galactocentric gradient, the discrepancy
in the metallicity distribution is interpreted as an indication of significant
diffusion of field stars into the solar neighborhood from beyond 10 kpc. These
results imply that the sun is NOT atypical of the stars formed in the solar
circle 4.6 Gyr ago. It is suggested that the discontinuity reflects the edge of
the initial galactic disk as defined by the disk globular cluster system and
the so-called thick disk; the initial offset in [Fe/H] created by the
differences in the chemical history on either side of the discontinuity has
carried through to the current stage of galactic evolution. If correct,
diffusion coupled with the absence of an abundance gradient could make the
separation of field stars on the basis of galactocentric origin difficult.Comment: 41 pages, 9 figure files, LaTex. Appendix section and tables (tex or
postscript) available at http://kubarb.phsx.ukans.edu/ ~twarog/ Submitted to
Astronomical Journal July 199
Globular Cluster Formation
The discovery of young globular clusters in merging galaxies and other
environments provides an opportunity to study directly the process of globular
cluster formation. Empirically it appears that globular cluster formation
occurs preferentially in regions in which star formation occurs at a high rate
and efficiency. Further, the interstellar medium in such regions is likely to
be at a higher pressure than less active star-forming environments. An
additional observational clue to the globular cluster formation process is that
young globular clusters have little or no mass-radius relationship. In this
paper I argue that high pressure and high star-formation efficiency are
responsible for current globular cluster formation. I suggest that the
precursors to globular clusters are molecular clouds and that the mass-radius
relationship exhibited by such clouds is wiped out by a variable star formation
efficiency.Comment: 13 pages. Review to appear in "Extragalactic Globular Cluster
Systems," ed. M. Kissler-Patig, Springer-Verla
Experimental Studies of the NaCs 53Î 0 and a3ÎŁ+ States
We report high resolution measurements of 372 NaCs 53Π0(v, J) ro-vibrational level energies in the range 0 ≤ v ≤ 22. The data have been used to construct NaCs 53Π0 potential energy curves using the Rydberg–Klein-Rees and inverted perturbation approximation methods. Bound-free 53Π0(v, J) → 1(a)3Σ+ emission has also been measured, and is used to determine the repulsive wall of the 1(a)3Σ+ state and the 53Π0 → 1(a)3Σ+ relative transition dipole moment function. Hyperfine structure in the 53Π0 state has not been observed in this experiment. This null result is explained using a simple vector coupling model
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