769 research outputs found
Product Market Competition and Human Resource Practices: An Analysis of the Retail Food Sector
The rise of super-centers and the entry of Wal-Mart into food retailing have dramatically altered the competitive environment in the industry. This paper explores the impact of such changes on the labor market practices of traditional food retailers. We use longitudinal data on workers and firms to construct new measures of compensation and employment, and examine how these measures evolve within and across firms in response to changes in product market structure. An additional feature of the analysis is to combine rich case study knowledge about the retail food industry with the new matched employer-employee data from the Census Bureau.
27/32
We show that when an N=2 SCFT flows to an N=1 SCFT via giving a mass to the
adjoint chiral superfield in a vector multiplet with marginal coupling, the
central charges a and c of the N=2 theory are related to those of the N=1
theory by a universal linear transformation. In the large N limit, this
relationship implies that the central charges obey a_IR/a_UV=c_IR/c_UV=27/32.
This gives a physical explanation to many examples of this number found in the
literature, and also suggests the existence of a flow between some theories not
previously thought to be connected.Comment: 3 pages. v2: references added, minor typos correcte
Product Market Competition and Human Resource Practices: An Analysis of the Retail Food Sector
The rise of super-centers and the entry of Wal-Mart into food retailing have dramatically altered the competitive environment in the industry. This paper explores the impact of such changes on the labor market practices of traditional food retailers. We use longitudinal data on workers and firms to construct new measures of compensation and employment, and examine how these measures evolve within and across firms in response to changes in product market structure. An additional feature of the analysis is to combine rich case study knowledge about the retail food industry with the new matched employer-employee data from the Census Bureau.supermarkets, human resource practices, competition, internal labor market, wage growth, Labor and Human Capital, Marketing,
Decomposing the Sources of Earnings Inequality: Assessing the Role of Reallocation
This paper exploits longitudinal employer-employee matched data from the U.S. Census Bureau to investigate the contribution of worker and firm reallocation to changes in earnings inequality within and across industries between 1992 and 2003. We find that factors that cannot be measured using standard cross-sectional data, including the entry and exit of firms and the sorting of workers across firms, are important sources of changes in earnings distributions over time. Our results also suggest that the dynamics driving changes in earnings inequality are heterogeneous across industries.inequality, linked employer-employee data, sorting
Decomposing the Sources of Earnings Inequality Assessing the Role of Reallocation
This paper uses matched employer-employee data from the Longitudinal Employer Household Dynamics database to investigate the contribution of worker and firm reallocation to within industry changes in wage inequality between 1992 and 2003. We find that the entry and exit of firms and the sorting of workers and firms based on underlying worker "skills" are important determinants of changes in industry earnings distributions over time. Our results suggest that the underlying dynamics of earnings inequality are complex and are due to factors that cannot be measured in standard crosssectional data.
Star Cluster Candidates in M81
We present a catalog of extended objects in the vicinity of M81 based a set
of 24 Hubble Space Telescope Advanced Camera for Surveys (ACS) Wide Field
Camera (WFC) F814W (I-band) images. We have found 233 good globular cluster
candidates; 92 candidate HII regions, OB associations, or diffuse open
clusters; 489 probable background galaxies; and 1719 unclassified objects. We
have color data from ground-based g- and r-band MMT Megacam images for 79
galaxies, 125 globular cluster candidates, 7 HII regions, and 184 unclassified
objects. The color-color diagram of globular cluster candidates shows that most
fall into the range 0.25 < g-r < 1.25 and 0.5 < r-I < 1.25, similar to the
color range of Milky Way globular clusters. Unclassified objects are often
blue, suggesting that many of them are likely to be HII regions and open
clusters, although a few galaxies and globular clusters may be among them.Comment: 35 pages, 11 figures, submitted to A
Evidence for the Strongest Version of the 4d a-Theorem, via a-Maximization Along RG Flows
In earlier work, we (KI and BW) gave a two line "almost proof" (for
supersymmetric RG flows) of the weakest form of the conjectured 4d a-theorem,
that a_{IR}<a_{UV}, using our result that the exact superconformal R-symmetry
of 4d SCFTs maximizes a=3Tr R^3-Tr R. The proof was incomplete because of two
identified loopholes: theories with accidental symmetries, and the fact that
it's only a local maximum of \it{a}. Here we discuss and extend a proposal of
Kutasov (which helps close the latter loophole) in which a-maximization is
generalized away from the endpoints of the RG flow, with Lagrange multipliers
that are conjectured to be identified with the running coupling constants.
a-maximization then yields a monotonically decreasing "a-function" along the RG
flow to the IR. As we discuss, this proposal in fact suggests the strongest
version of the a-theorem: that 4d RG flows are gradient flows of an a-function,
with positive definite metric. In the perturbative limit, the RG flow metric
thus obtained is shown to agree precisely with that found by very different
computations by Osborn and collaborators. As examples, we discuss a new class
of 4d SCFTs, along with their dual descriptions and IR phases, obtained from
SQCD by coupling some of the flavors to added singlets.Comment: 36 pages, 6 figures. v2: added referenc
Efficacy of Disease-Modifying Therapies in Relapsing Remitting Multiple Sclerosis: A Systematic Comparison
The treatment of relapsing-remitting multiple sclerosis (RRMS) has become more effective over the last decade with the advent of the currently available disease-modifying therapies (DMTs). Pivotal clinical studies differ in many characteristics, such that cross-comparisons of relative risk reductions are of limited value and can be misleading. Our objective was to compare the clinical efficacy of currently approved first-line DMTs in patients with RRMS, applying an evidence-based medicine approach. We reviewed all phase III pivotal trials of DMTs. Six clinical trials of Avonex®, Betaseron®, Copaxone®, Rebif® and Tysabri® in patients with RRMS were identified for analysis. Only randomized, placebo-controlled, double-blind studies were included. The clinical efficacy endpoints compared were: proportion of relapse-free patients at 1 and 2 years; annualized relapse rate at 2 years; proportion of progression-free patients at 2 years, and proportion of patients free of gadolinium-enhancing lesions at 1 year or 9 months. Based on these analyses, Betaseron, Rebif, and Tysabri show comparable effects, whereas for several endpoints Avonex or Copaxone did not significantly differ from placebo. In the absence of head-to-head studies for all products used to treat RRMS, it still may be possible to compare treatment effects by applying evidence-based medicine principles
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