1,297 research outputs found
Skill policies for Scotland
This paper argues that skill formation is a life-cycle process and develops the
implications of this insight for Scottish social policy. Families are major
producers of skills, and a successful policy needs to promote effective families
and to supplement failing ones. Targeted early interventions have proven to be
very effective in compensating for the effect of neglect. Improvements in
traditional measures of school quality, tuition subsidies, company-sponsored
and public job training are unlikely to be as effective. We review the evidence
and present several policy recommendations
A study of higher dimensional inhomogeneous cosmological model
In this paper we present a class of exact inhomogeneous solutions to
Einstein's equations for higher dimensional Szekeres metric with perfect fluid
and a cosmological constant. We also show particular solutions depending on the
choices of various parameters involved and for dust case. Finally, we examine
the asymptotic behaviour of some of these solutions.Comment: 9 Latex pages, No figure, Revtex styl
A novel approach to identify blazar emission states using clustering algorithms
Even after decades of multi-wavelength (MWL) observations, blazars still
remain mysterious objects. Their extreme variability and variety of emission
characteristics observed during different time periods make it hard to
understand the fundamental processes behind their emission. Thus, a robust
identification and characterization of the different emission states among
blazars is vital to investigate the underlying processes causing the observed
emission. In this contribution, we present a novel technique to determine
emission states across MWL lightcurves (LCs) of blazars using a clustering
algorithm. Using the Extreme Deconvolution algorithm, we apply a Gaussian
Mixture model to the 12-year long-term LC of one of our archetypal blazars, Mrk
501. The two main advantages of the method are that, compared to more
conventional methods, such as the Bayesian block algorithm, it considers
multiple wavebands simultaneously and it is not dependent on the order in time
of the data points. This allows to assign data points to the same emission
state even though they are separated by other states in time. The well sampled
gamma-ray, X-ray and radio LCs used as input allow to identify six clusters.
The clustering is mainly driven by the X-ray flux, showing different levels of
quiescent, intermediate and high flux states. However, the radio flux reveals a
more complicated pattern, dividing some of the X-ray flux levels in low and
high-radio flux states. This suggests that multiple emission regions maybe
responsible for the radio to gamma-ray flux.Comment: 8 pages, 1 figure, Presented at the 38th International Cosmic Ray
Conference (ICRC 2023), 202
Removing epoxy underfill between neighbouring components using acid for component chip-off
International audienc
The Jefferson Lab Frozen Spin Target
A frozen spin polarized target, constructed at Jefferson Lab for use inside a
large acceptance spectrometer, is described. The target has been utilized for
photoproduction measurements with polarized tagged photons of both longitudinal
and circular polarization. Protons in TEMPO-doped butanol were dynamically
polarized to approximately 90% outside the spectrometer at 5 T and 200--300 mK.
Photoproduction data were acquired with the target inside the spectrometer at a
frozen-spin temperature of approximately 30 mK with the polarization maintained
by a thin, superconducting coil installed inside the target cryostat. A 0.56 T
solenoid was used for longitudinal target polarization and a 0.50 T dipole for
transverse polarization. Spin-lattice relaxation times as high as 4000 hours
were observed. We also report polarization results for deuterated propanediol
doped with the trityl radical OX063.Comment: 11 pages, 12 figures, preprint submitted to Nuclear Instruments and
Methods in Physics Research, Section
Design of interactive visualization of models and students data
This document reports the design of the interactive visualizations of open student models that will
be performed in GRAPPLE. The visualizations will be based on data stored in the domain model and student model, and aim at supporting learners to be more engaged in the learning process, and instructors in assisting the learners
Post-Newtonian extension of the Newton-Cartan theory
The theory obtained as a singular limit of General Relativity, if the
reciprocal velocity of light is assumed to tend to zero, is known to be not
exactly the Newton-Cartan theory, but a slight extension of this theory. It
involves not only a Coriolis force field, which is natural in this theory
(although not original Newtonian), but also a scalar field which governs the
relation between Newtons time and relativistic proper time. Both fields are or
can be reduced to harmonic functions, and must therefore be constants, if
suitable global conditions are imposed. We assume this reduction of
Newton-Cartan to Newton`s original theory as starting point and ask for a
consistent post-Newtonian extension and for possible differences to usual
post-Minkowskian approximation methods, as developed, for example, by
Chandrasekhar. It is shown, that both post-Newtonian frameworks are formally
equivalent, as far as the field equations and the equations of motion for a
hydrodynamical fluid are concerned.Comment: 13 pages, LaTex, to appear in Class. Quantum Gra
The Cosmic No-Hair Theorem and the Nonlinear Stability of Homogeneous Newtonian Cosmological Models
The validity of the cosmic no-hair theorem is investigated in the context of
Newtonian cosmology with a perfect fluid matter model and a positive
cosmological constant. It is shown that if the initial data for an expanding
cosmological model of this type is subjected to a small perturbation then the
corresponding solution exists globally in the future and the perturbation
decays in a way which can be described precisely. It is emphasized that no
linearization of the equations or special symmetry assumptions are needed. The
result can also be interpreted as a proof of the nonlinear stability of the
homogeneous models. In order to prove the theorem we write the general solution
as the sum of a homogeneous background and a perturbation. As a by-product of
the analysis it is found that there is an invariant sense in which an
inhomogeneous model can be regarded as a perturbation of a unique homogeneous
model. A method is given for associating uniquely to each Newtonian
cosmological model with compact spatial sections a spatially homogeneous model
which incorporates its large-scale dynamics. This procedure appears very
natural in the Newton-Cartan theory which we take as the starting point for
Newtonian cosmology.Comment: 16 pages, MPA-AR-94-
Recolonizing gray wolves increase parasite infection risk in their prey
The recent recolonization of Central Europe by the European gray wolf (Canis
lupus) provides an opportunity to study the dynamics of parasite transmission
for cases when a definitive host returns after a phase of local extinction. We
investigated whether a newly established wolf population increased the
prevalence of those parasites in ungulate intermediate hosts representing wolf
prey, whether some parasite species are particularly well adapted to wolves,
and the potential basis for such adaptations. We recorded Sarcocystis species
richness in wolves and Sarcocystis prevalence in ungulates harvested in study
sites with and without permanent wolf presence in Germany using microscopy and
DNA metabarcoding. Sarcocystis prevalence in red deer (Cervus elaphus) was
significantly higher in wolf areas (79.7%) than in control areas (26.3%) but
not in roe deer (Capreolus capreolus) (97.2% vs. 90.4%) or wild boar (Sus
scrofa) (82.8% vs. 64.9%). Of 11 Sarcocystis species, Sarcocystis taeniata and
Sarcocystis grueneri occurred more often in wolves than expected from the
Sarcocystis infection patterns of ungulate prey. Both Sarcocystis species
showed a higher increase in prevalence in ungulates in wolf areas than other
Sarcocystis species, suggesting that they are particularly well adapted to
wolves, and are examples of “wolf specialists”. Sarcocystis species richness
in wolves was significantly higher in pups than in adults. “Wolf specialists”
persisted during wolf maturation. The results of this study demonstrate that
(1) predator–prey interactions influence parasite prevalence, if both predator
and prey are part of the parasite life cycle, (2) mesopredators do not
necessarily replace the apex predator in parasite transmission dynamics for
particular parasites of which the apex predator is the definitive host, even
if meso‐ and apex predators were from the same taxonomic family (here:
Canidae, e.g., red foxes Vulpes vulpes), and (3) age‐dependent immune
maturation contributes to the control of protozoan infection in wolves
Anisotropy and inflation in Bianchi I brane worlds
After a more general assumption on the influence of the bulk on the brane, we
extend some conclusions by Maartens et al. and Santos et al. on the asymptotic
behavior of Bianchi I brane worlds. As a consequence of the nonlocal
anisotropic stresses induced by the bulk, in most of our models, the brane does
not isotropize and the nonlocal energy does not vanish in the limit in which
the mean radius goes to infinity. We have also found the intriguing possibility
that the inflation due to the cosmological constant might be prevented by the
interaction with the bulk. We show that the problem for the mean radius can be
completely solved in our models, which include as particular cases those in the
references above.Comment: 10 pages, improved discussion on the likeliness of
non-isotropization, completed list of references, matches version to appear
in Class. Quantum Gra
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