964 research outputs found
Employment and social policy will be a sticking point in negotiations between London and Brussels
Compared to the legal framework of the Single European Market, the EU’s competence in employment and social policy is relatively weak. Paul Copeland (QMUL) writes that this is likely to be a sticking point in negotiations between London and Brussels on the UK’s future relationship with the EU
Self-tuning and the derivation of the Fab Four
We have recently proposed a special class of scalar tensor theories known as
the Fab Four. These arose from attempts to analyse the cosmological constant
problem within the context of Horndeski's most general scalar tensor theory.
The Fab Four together give rise to a model of self-tuning, with the relevant
solutions evading Weinberg's no-go theorem by relaxing the condition of
Poincare invariance in the scalar sector. The Fab Four are made up of four
geometric terms in the action with each term containing a free potential
function of the scalar field. In this paper we rigorously derive this model
from the general model of Horndeski, proving that the Fab Four represents the
only classical scalar tensor theory of this type that has any hope of tackling
the cosmological constant problem. We present the full equations of motion for
this theory, and give an heuristic argument to suggest that one might be able
to keep radiative corrections under control. We also give the Fab Four in terms
of the potentials presented in Deffayet et al's version of Horndeski.Comment: 25 pages, 1 figur
Dark energy after GW170817, revisited
We revisit the status of scalar-tensor theories with applications to dark
energy in the aftermath of the gravitational wave signal GW170817 and its
optical counterpart GRB170817A. At the level of the cosmological background, we
identify a class of theories, previously declared unviable in this context,
whose anomalous gravitational wave speed is proportional to the scalar equation
of motion. As long as the scalar field is assumed not to couple directly to
matter, this raises the possibility of compatibility with the gravitational
wave data, for any cosmological sources, thanks to the scalar dynamics. This
newly "rescued" class of theories includes examples of generalised quintic
galileons from Horndeski theories. Despite the promise of this leading order
result, we show that the loophole ultimately fails when we include the effect
of large scale inhomogeneities.Comment: Updated with corrections to the gravitational wave propagation coming
from higher order terms in the presence of large scale inhomogeneities. These
close off any remaining loopholes. References adde
The (In)Effectiveness of the European Employment Strategy
Qualitative studies of the European Employment Strategy produce conflicting accounts of its effectiveness within the Member States. Furthermore, such studies are limited in that they predominantly concern a small number of country case studies and one or two particular policy issues. Obtaining an accurate overview of the effectiveness of the OMC is therefore problematic. This article constructs a quantitative framework to analyse the effectivnes of the EES and applies it to ten EU Member States between 2005-2009. The analysis differentiates between shallow voluntary compliance, whereby member state responses to the EES represent activities which they themselves identify as a priority, and deep voluntary normative compliance, whereby member state activity is related to specific Council recommendations to improve policies in a particular area. The paper finds substantial evidence for both forms of compliance, however, an analysis of the formation of country specific recommendations, reveals the deeply politically negotiated nature of their formation and the limitations of our findings
Aging and the Behavioral Problems of Brain Injury
Educational Objectives
1. List the various classes of brain injury.
2. Identify cognitive and emotional problems as among the most common and disabling complications of brain injury.
3. Assess challenges to successful aging with a brain injury.
4. Examine the consequences of inadequate systems of care for the challenging behaviors produced by brain injury
Decay of an inhomogeneous state via resonant tunnelling
We recently investigated the nature of resonant tunnelling in standard scalar
Quantum Field Theory, uncovering the conditions required for resonance. It was
shown that whereas the homogeneous false vacuum may decay via bubble
nucleation, it may not decay in a resonant fashion. The no-go theorem given
there is circumvented in this study by considering an initial state other than
the homogeneous false vacuum, and we confirm our mechanism by showing in an
explicit model how resonant tunnelling occurs. Using this model we demonstrate
how the tunnelling rate depends on the energy of specially constructed initial
states, with these states corresponding to contracting spherical bubbles of
some vacuum that evolve to a minimum radius and then tunnel to another vacuum,
instead of the classical motion where the bubble would just start to expand.Comment: 19 pages, 22 figure
Characterization of the SECIS binding protein 2 complex required for the co-translational insertion of selenocysteine in mammals
Selenocysteine is incorporated into at least 25 human proteins by a complex mechanism that is a unique modification of canonical translation elongation. Selenocysteine incorporation requires the concerted action of a kink-turn structural RNA (SECIS) element in the 3′ untranslated region of each selenoprotein mRNA, a selenocysteine-specific translation elongation factor (eEFSec) and a SECIS binding protein (SBP2). Here, we analyze the molecular context in which SBP2 functions. Contrary to previous findings, a combination of gel filtration chromatography and co-purification studies demonstrates that SBP2 does not self-associate. However, SBP2 is found to be quantitatively associated with ribosomes. Interestingly, a wild-type but not mutant SECIS element is able to effectively compete with the SBP2 ribosome interaction, indicating that SBP2 cannot simultaneously interact with the ribosome and the SECIS element. This data also supports the hypothesis that SBP2 interacts with one or more kink turns on 28S rRNA. Based on these results, we propose a revised model for selenocysteine incorporation where SBP2 remains ribosome bound except during selenocysteine delivery to the ribosomal A-site
Seasonal-adjustment Based Feature Selection Method for Large-scale Search Engine Logs
Search engine logs have a great potential in tracking and predicting
outbreaks of infectious disease. More precisely, one can use the search volume
of some search terms to predict the infection rate of an infectious disease in
nearly real-time. However, conducting accurate and stable prediction of
outbreaks using search engine logs is a challenging task due to the following
two-way instability characteristics of the search logs. First, the search
volume of a search term may change irregularly in the short-term, for example,
due to environmental factors such as the amount of media or news. Second, the
search volume may also change in the long-term due to the demographic change of
the search engine. That is to say, if a model is trained with such search logs
with ignoring such characteristic, the resulting prediction would contain
serious mispredictions when these changes occur.
In this work, we proposed a novel feature selection method to overcome this
instability problem. In particular, we employ a seasonal-adjustment method that
decomposes each time series into three components: seasonal, trend and
irregular component and build prediction models for each component
individually. We also carefully design a feature selection method to select
proper search terms to predict each component. We conducted comprehensive
experiments on ten different kinds of infectious diseases. The experimental
results show that the proposed method outperforms all comparative methods in
prediction accuracy for seven of ten diseases, in both now-casting and
forecasting setting. Also, the proposed method is more successful in selecting
search terms that are semantically related to target diseases.Comment: The 25th ACM SIGKDD Conference on Knowledge Discovery and Data Mining
(KDD '19
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