1,367 research outputs found
Factors Affecting the Output and Quit Propensities of Production Workers
We have used a proprietary data set of newly hired semi-skilled production workers at one location of a large unionized firm to investigate several issues in labor economics. This data set is unique in several respects: the workers in our sample faced the same wage schedules, had the same promotional opportunities, the same job tenure (zero), similar working conditions, and had jobs for which we were able to record their physical output. We analyze these data by formulating a simultaneous equation model to explain wages, output, education, and a worker's quit decision. The model is estimated by maximum likelihood and subjected to a variety of specification tests. Such tests include a comparison of the standard error estimates that form the basis for White's information test, and White's version of a Hausman specification test. Our principal findings are: 1. Individuals that choose more education than we would expect from their observed characteristics have lower than expected quit propensities. We argue that this low quit propensity is one of the unmeasured (and unobserved) attributes that sorting models posit are correlated with education and hence distort the usual estimates of rates of return to education. 2. The performance of non-whites in our sample was no lower than that of whites. However, on their previous jobs non-whites received lower wages than did whites. 3. The output per hour of males in our sample was higher than that of females; however, we were unable to conclude from our data whether these productivity differences could explain the higher wages received by men on their previous jobs. Moreover, this output difference may be transitory and may diminish with on-the-job learning. 4. The expected value of alternative wages had a positive (but not statistically very significant) effect on quit rates. Workers with better alternative opportunities were more likely to quit (all workers had the same opportunities on their current job). 5. Finally we found that workers with high output levels were more likely to quit than were workers with average output levels.
Sequence of the mouse Q4 class I gene and characterization of the gene product
The Q4 class I gene has been shown to participate
in gene conversion events within the mouse major
histocompatibility complex. Its complete genomic nucleotide
sequence has been determined. The 5' half of Q4
resembles H-2 genes more strongly than other Q genes.
Its 3' end, in contrast, is Q-like and contains a translational
stop signal in exon 5 which predicts a polypeptide with
an incomplete membrane spanning segment. The presence
of two inverted B1 repeats suggests that part of the Q4
gene may be mobile within the genome. Gene transfer experiments
have shown that the Q4 gene encodes a
ß2-microglobulin associated polypeptide of Mr 41 000. A
similar protein was found in activated mouse spleen cells.
The Q4 polypeptide was found to be secreted both by
spleen cells and by transfected fibroblasts and was not detectable
on the cell surface. Antibody binding and twodimensional
gel electrophoresis indicate that the Q4
molecule is identical to a mouse class I polypeptide, Qb-1,
which has been previously described
A Nonpolymorphic Class I Gene in the Murine Major Histocompatibility Complex
DNA sequence analysis of a class I gene (QlO), which maps to the Qa2,3 locus in the C57BL/lO (H-
2b haplotype) mouse, reveals that it is almost identical
to a cDNA clone (pH16) isolated from a SWR/J
(H-2q haplotype) mouse liver cDNA library. Exon 5,
in particular, has an unusual structure such that a
polypeptide product is unlikely to be anchored in the
cell membrane. Our findings suggest that the two
sequences are derived from allelic class I genes,
which are nonpolymorphic, in contrast to H-2K allelic
sequences from the same mice, and they may encode
liver-specific polypeptides of unknown function.
Our previous studies indicate that the QlO gene
is a potential donor gene for the generation of mutations
at the H-2K locus by inter-gene transfer of
genetic information. Thus the lack of polymorphism
in class I genes at the QlO locus implies either that
they are not recipients for such exchanges or that
selective pressure prevents the accumulation of mutations
in genes at this locus
Entanglement Sharing and Decoherence in the Spin-Bath
The monogamous nature of entanglement has been illustrated by the derivation
of entanglement sharing inequalities - bounds on the amount of entanglement
that can be shared amongst the various parts of a multipartite system.
Motivated by recent studies of decoherence, we demonstrate an interesting
manifestation of this phenomena that arises in system-environment models where
there exists interactions between the modes or subsystems of the environment.
We investigate this phenomena in the spin-bath environment, constructing an
entanglement sharing inequality bounding the entanglement between a central
spin and the environment in terms of the pairwise entanglement between
individual bath spins. The relation of this result to decoherence will be
illustrated using simplified system-bath models of decoherence.Comment: 5 pages, 1 figure v2: 6 pages 2 figures, additional example and
reference
Long-Period Giant Companions to Three Compact, Multiplanet Systems
Understanding the relationship between long-period giant planets and multiple smaller short-period planets is critical for formulating a complete picture of planet formation. This work characterizes three such systems. We present Kepler-65, a system with an eccentric (e = 0.28 ± 0.07) giant planet companion discovered via radial velocities (RVs) exterior to a compact, multiply transiting system of sub-Neptune planets. We also use precision RVs to improve mass and radius constraints on two other systems with similar architectures, Kepler-25 and Kepler-68. In Kepler-68 we propose a second exterior giant planet candidate. Finally, we consider the implications of these systems for planet formation models, particularly that the moderate eccentricity in Kepler-65\u27s exterior giant planet did not disrupt its inner system
Separation-dependent localization in a two-impurity spin-boson model
Using a variational approach we investigate the delocalized to localized
crossover in the ground state of an Ohmic two-impurity spin-boson model,
describing two otherwise non-interacting spins coupled to a common bosonic
environment. We show that a competition between an environment-induced Ising
spin interaction and externally applied fields leads to variations in the
system-bath coupling strength, , at which the delocalized-localized
crossover occurs. Specifically, the crossover regime lies between
and depending upon the spin separation and the
strength of the transverse tunneling field. This is in contrast to the
analogous single spin case, for which the crossover occurs (in the scaling
limit) at fixed . We also discuss links between the
two-impurity spin-boson model and a dissipative two-spin transverse Ising
model, showing that the latter possesses the same qualitative features as the
Ising strength is varied. Finally, we show that signatures of the crossover may
be observed in single impurity observables, as well as in the behaviour of the
system-environment entanglement.Comment: 12 pages, 9 figures. Published version. Expanded discussion of the
distance dependence between the impurities, and added a related figur
Lack of class I H-2 antigens in cells transformed by radiation leukemia virus is associated with methylation and rearrangement of H-2 DNA
Transformation of murine thymocytes by
radiation leukemia virus is associated with reduced expression
of the class I antigens encoded in the major histocompatibility
complex (MHC) and increased methylation and altered restriction
enzyme patterns of MHC DNA. These changes may play
a role in host susceptibility to virus-induced leukemogenesis
and accord with the notion that viral genomes play a regulatory
function when they integrate adjacent to histocompatibiity
genes
Seeing double with K2: Testing re-inflation with two remarkably similar planets around red giant branch stars
Despite more than 20 years since the discovery of the first gas giant planet
with an anomalously large radius, the mechanism for planet inflation remains
unknown. Here, we report the discovery of EPIC228754001.01, an inflated gas
giant planet found with the NASA K2 Mission, and a revised mass for another
inflated planet, K2-97b. These planets reside on ~9 day orbits around host
stars which recently evolved into red giants. We constrain the irradiation
history of these planets using models constrained by asteroseismology and
Keck/HIRES spectroscopy and radial velocity measurements. We measure planet
radii of 1.31 +\- 0.11 Rjup and and 1.30 +\- 0.07 Rjup, respectively. These
radii are typical for planets receiving the current irradiation, but not the
former, zero age main sequence irradiation of these planets. This suggests that
the current sizes of these planets are directly correlated to their current
irradiation. Our precise constraints of the masses and radii of the stars and
planets in these systems allow us to constrain the planetary heating efficiency
of both systems as 0.03% +0.03%/-0.02%. These results are consistent with a
planet re-inflation scenario, but suggest the efficiency of planet re-inflation
may be lower than previously theorized. Finally, we discuss the agreement
within 10% of stellar masses and radii, and planet masses, radii, and orbital
periods of both systems and speculate that this may be due to selection bias in
searching for planets around evolved stars.Comment: 18 pages, 15 figures, accepted to AJ. Figures 11, 12, and 13 are the
key figures of the pape
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