5,063 research outputs found
Reallocation Effects of the Minimum Wage
We investigate the wage, employment and reallocation effects of the introduction of a nationwide minimum wage in Germany that affected 15% of all employees. Based on identification designs that exploit variation in exposure across individuals and local areas, we find that the minimum wage raised wages, but did not lower employment. It also led to the reallocation of low-wage workers from smaller to larger, from lower- to higher-paying, and from less- to more-productive establishments. This worker upgrading accounts for up to 17% of the wage increase induced by the minimum wage. Moreover, at the regional level, average establishment quality increased in more affected areas in the years following the introduction of the minimum wage
Discrimination of Vaccinated and infected Pigs by Salmonella-specific IGa antibodies
Isotype switching from IgM to IgG or IgA leads to generation of high affinity antibodies during the immune response. This phenomenon can be applied for differentiation of early and late infection stages. The purpose of this study was to evaluate the applicability of a newly developed Ig-isotype specific Salmonella antibody ELISA for discrimination between vaccinated and infected pigs. Using this novel ELISA we were able to detect different patterns of Salmonella-specific IgM, IgG and IgA antibodies following immunization with a S. Typhimurium live vaccine or after experimental infection with a nalidixic-acid resistant wild-type strain of S. Typhimurium. Interestingly, Salmonella-specific IgA antibodies represented an excellent tool for the recognition of fresh infection in vaccinated pigs. Under SPF conditions, we were able to discriminate between naive, vaccinated, experimentally infected nonvaccinated, and experimentally infected vaccinated animals. However, the highest specific IgA levels were detected in challenged vaccinated pigs. Preliminary results from field trials support the findings from experiments using SPF animals
Steps toward the power spectrum of matter. II. The biasing correction with sigma_8 normalization
A new method to determine the bias parameter of galaxies relative to matter
is suggested. The method is based on the assumption that gravity is the
dominating force which determines the formation of the structure in the
Universe. Due to gravitational instability the galaxy formation is a threshold
process: in low-density environments galaxies do not form and matter remains in
primordial form. We investigate the influence of the presence of void and
clustered populations to the power spectrum of matter and galaxies. The power
spectrum of galaxies is similar to the power spectrum of matter; the fraction
of total matter in the clustered population determines the difference between
amplitudes of fluctuations of matter and galaxies, i.e. the bias factor. To
determine the fraction of matter in voids and clustered population we perform
numerical simulations. The fraction of matter in galaxies at the present epoch
is found using a calibration through the sigma_8 parameter.Comment: LaTex (sty files added), 31 pages, 4 PostScript figures embedded,
Astrophysical Journal (accepted
On ionisation effects and abundance ratios in damped Lyman-alpha systems
The similarity between observed velocity structures of Al III and singly
ionised species in damped Lyman-alpha systems (DLAs) suggests the presence of
ionised gas in the regions where most metal absorption lines are formed.
To explore the possible implications of ionisation effects we construct a
simplified two-region model for DLAs consisting of an ionisation bounded region
with an internal radiation field and a neutral region with a lower metal
content. Within this framework we find that ionisation effects are important.
If taken into account, the element abundance ratios in DLAs are quite
consistent with those observed in Milky Way stars and in metal-poor H II
regions in blue compact dwarf galaxies. In particular we cannot exclude the
same primary N origin in both DLAs and metal-poor galaxies. From our models no
dust depletion of heavy elements needs to be invoked; little depletion is
however not excluded.Comment: to appear in "Evolution of Galaxies. I. Observational clues", Eds.
J.M. Vilchez, G. Stasinska, Astrophysics and Space Science, in press. 5
pages, including 3 figure
Collective motion of active Brownian particles in one dimension
We analyze a model of active Brownian particles with non-linear friction and
velocity coupling in one spatial dimension. The model exhibits two modes of
motion observed in biological swarms: A disordered phase with vanishing mean
velocity and an ordered phase with finite mean velocity. Starting from the
microscopic Langevin equations, we derive mean-field equations of the
collective dynamics. We identify the fixed points of the mean-field equations
corresponding to the two modes and analyze their stability with respect to the
model parameters. Finally, we compare our analytical findings with numerical
simulations of the microscopic model.Comment: submitted to Eur. Phys J. Special Topic
Steps toward the power spectrum of matter. III. The primordial spectrum
Observed power spectrum of matter found in Papers I and II is compared with
analytical power spectra. Spatially flat cold and mixed dark matter models with
cosmological constant and open models are considered. The primordial power
spectrum of matter is determined using the power spectrum of matter and the
transfer functions of analytical models. The primordial power spectrum has a
break in amplitude. We conclude that a scale-free primordial power spectrum is
excluded if presently available data on the distribution of clusters and
galaxies represent the true mass distribution of the Universe.Comment: LaTex (sty files added), 22 pages, 5 PostScript figures embedded,
Astrophysical Journal (accepted
UVES observations of QSO 0000-2620: oxygen and zinc abundances in the Damped Ly-alpha galaxy at z_abs=3.3901
Observations of the QSO 0000-2620 with UVES spectrograph at the 8.2m ESO
KUEYEN telescope are used for abundance analysis of the damped Ly-alpha system
at z_{abs}=3.3901. Several Oxygen lines are identified in the Ly_alpha forest
and a measure for the oxygen abundance is obtained at [O/H]=-1.85 +/- 0.1 by
means of the unsaturated OI 925 A and OI 950 A lines. This represents the most
accurate O measurement in a damped Ly_alpha galaxy so far. We have also
detected ZnII 2026 A and CrII 2056, 2062 A redshifted at about 8900 A and found
abundances [Zn/H] = -2.07 +/- 0.1 and [Cr/H]=-1.99 +/- 0.1. Furthermore,
previous measurements of Fe, Si, Ni and N have been refined yielding
[Fe/H]=-2.04 +/- 0.1, [Si/H]=-1.90 +/- 0.1, [Ni/H]=-2.27 +/- 0.1, and
[N/H]=-2.68 +/- 0.1. The abundance of the non-refractory element zinc is the
lowest among the damped Ly-alpha systems showing that the associated
intervening galaxy is indeed in the early stages of its chemical evolution. The
fact that the Zn abundance is identical to that of the refractory elements Fe
and Cr suggests that dust grains have not formed yet. In this Damped Ly-alpha
system the observed [O,S,Si/Zn,Fe,Cr] ratios, in whatever combination are
taken, are close to solar (i.e 0.1-0.2 dex) and do not show the
[alpha-element/Fe] enhancement observed in Milky Way stars of comparable
metallicity. The observed behavior supports a galaxy evolution model
characterized by either episodic or low star formation rate rather than a
Milky-Way-type evolutionary model.Comment: Accepted by Ap
Higher Dimensional Operators in Top Condensation from a Renormalization Group Point of View
The predictive power of top-condensation models strongly depends on the
behaviour of higher dimensional operators. These are analyzed in this paper by
an extension of the standard renormalization group (RG) arguments which turns
out to be a surprisingly powerful tool. Top-condensation models intermediated
by underlying scalar exchange can be shown to be mere reparametrizations of the
standard model. Further on, RG-arguments show that dynamical vector states
cannot be lowered in top-condensation models. Finally we give a general
argument concerning the size of higher dimensional operators of heavy vector
exchange.Comment: 21 pages, latex2e, axodraw.sty, epsfig.sty, 4 postscript figures.
Some of the discussions extended and clarifie
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