1,373 research outputs found
Refining the prediction of multisite pain in 13-year-old boys and girls by using parent-reported pain experiences in the first decade of life
Background
We evaluated different pain profiles as prospective predictors of multisite pain in 13-year-old adolescents (1300 girls and 1457 boys) enrolled in Generation XXI, a birth cohort study in Portugal.
Methods
Pain history was queried using the Luebeck Pain Questionnaire through parent proxy- (ages 7 and 10) and adolescent (age 13) self-reports. We estimated the risk of multisite pain (2 or more pain sites) at age 13, according to previous pain experiences, including accumulation and timing. We defined five profiles that combined adverse features at ages 7 and 10 (recurrence, multisite, frequency, duration, intensity, triggers, activity restrictions, passive coping, and family history) and estimated their relative risks (RR) and likelihood ratios (LR) for adolescent multisite pain.
Results
At age 13, 39.2% of girls and 27.2% of boys reported multisite pain in the previous three months. The risk was higher among girls with multisite and recurrent pain at ages 7 and 10 than in girls without those adverse features, especially if psychosocial triggers were also present (RR 1.87; 95% confidence interval 1.36, 2.36 and LR 3.49; 1.53, 7.96). Boys with recurrent pain of higher frequency and causing activity restrictions at ages 7 and 10 had a higher risk of multisite pain at 13 (RR 2.05; 1.03, 3.05 and LR 3.06; 1.12, 8.39). Earlier adverse experiences were more predictive of future pain in girls than in boys.
Conclusions
Different profiles were useful to rule in future multisite pain in boys and girls. This provides clues for early stratification of chronic pain risk.
Significance
We identified sex-specific pain features that can be collected by practitioners in the first decade of life to improve the stratification of children in terms of their future risk of a maladaptive pain experience in adolescence. Using a prospective population-based cohort design, we show that early multisite pain and psychosocial triggers are relevant predictors of future multisite pain in girls, whereas repeated reports of high-frequency pain leading to activity restrictions are predictive of adolescent multisite pain in boys.This study was funded by the European Regional Development Fund (ERDF), through COMPETE 2020 Operational Programme 'Competitiveness and Internationalization' together with national funding from the Foundation for Science and Technology (FCT) – Portuguese Ministry of Science, Technology and Higher Education – through the project 'STEPACHE – The pediatric roots of amplified pain: from contextual influences to risk stratification' (POCI-01-0145-FEDER-029087, info:eu-repo/grantAgreement/FCT/9471 - RIDTI/PTDC/SAU-EPI/29087/2017/PT) and by the Epidemiology Research Unit – Instituto de Saúde Pública, Universidade do Porto (EPIUnit) (POCI-01-0145-FEDER-006862; UID/DTP/04750/2019), Administração Regional de Saúde Norte (Regional Department of the Portuguese Ministry of Health) and Calouste Gulbenkian Foundation. This work was also supported by a research grant from FOREUM Foundation for Research in Rheumatology (Career Research Grant)
Dissipation instability of Couette-like adiabatic flows in a plane channel
The mixed convection flow in a plane channel with adiabatic boundaries is
examined. The boundaries have an externally prescribed relative velocity
defining a Couette-like setup for the flow. A stationary flow regime is
maintained with a constant velocity difference between the boundaries,
considered as thermally insulated. The effect of viscous dissipation induces a
heat source in the flow domain and, hence, a temperature gradient. The
nonuniform temperature distribution causes, in turn, a buoyancy force and a
combined forced and free flow regime. Dual mixed convection flows occur for a
given velocity difference. Their structure is analysed where, in general, only
one branch of the dual flows is compatible with the Oberbeck-Boussinesq
approximation, for realistic values of the Gebhart number. A linear stability
analysis of the basic stationary flows with viscous dissipation is carried out.
The stability eigenvalue problem is solved numerically, leading to the
determination of the neutral stability curves and the critical values of the
P\'eclet number, for different Gebhart numbers. An analytical asymptotic
solution in the special case of perturbations with infinite wavelength is also
developed.Comment: 24 pages, 11 figure
Faithful Squashed Entanglement
Squashed entanglement is a measure for the entanglement of bipartite quantum
states. In this paper we present a lower bound for squashed entanglement in
terms of a distance to the set of separable states. This implies that squashed
entanglement is faithful, that is, strictly positive if and only if the state
is entangled. We derive the bound on squashed entanglement from a bound on
quantum conditional mutual information, which is used to define squashed
entanglement and corresponds to the amount by which strong subadditivity of von
Neumann entropy fails to be saturated. Our result therefore sheds light on the
structure of states that almost satisfy strong subadditivity with equality. The
proof is based on two recent results from quantum information theory: the
operational interpretation of the quantum mutual information as the optimal
rate for state redistribution and the interpretation of the regularised
relative entropy of entanglement as an error exponent in hypothesis testing.
The distance to the set of separable states is measured by the one-way LOCC
norm, an operationally-motivated norm giving the optimal probability of
distinguishing two bipartite quantum states, each shared by two parties, using
any protocol formed by local quantum operations and one-directional classical
communication between the parties. A similar result for the Frobenius or
Euclidean norm follows immediately. The result has two applications in
complexity theory. The first is a quasipolynomial-time algorithm solving the
weak membership problem for the set of separable states in one-way LOCC or
Euclidean norm. The second concerns quantum Merlin-Arthur games. Here we show
that multiple provers are not more powerful than a single prover when the
verifier is restricted to one-way LOCC operations thereby providing a new
characterisation of the complexity class QMA.Comment: 24 pages, 1 figure, 1 table. Due to an error in the published
version, claims have been weakened from the LOCC norm to the one-way LOCC
nor
Measuring the extent of convective cores in low-mass stars using Kepler data: towards a calibration of core overshooting
Our poor understanding of the boundaries of convective cores generates large
uncertainties on the extent of these cores and thus on stellar ages. Our aim is
to use asteroseismology to consistently measure the extent of convective cores
in a sample of main-sequence stars whose masses lie around the mass-limit for
having a convective core. We first test and validate a seismic diagnostic that
was proposed to probe in a model-dependent way the extent of convective cores
using the so-called ratios, which are built with and
modes. We apply this procedure to 24 low-mass stars chosen among Kepler targets
to optimize the efficiency of this diagnostic. For this purpose, we compute
grids of stellar models with both the CESAM2k and MESA evolution codes, where
the extensions of convective cores are modeled either by an instantaneous
mixing or as a diffusion process. Among the selected targets, we are able to
unambiguously detect convective cores in eight stars and we obtain seismic
measurements of the extent of the mixed core in these targets with a good
agreement between the CESAM2k and MESA codes. By performing optimizations using
the Levenberg-Marquardt algorithm, we then obtain estimates of the amount of
extra-mixing beyond the core that is required in CESAM2k to reproduce seismic
observations for these eight stars and we show that this can be used to propose
a calibration of this quantity. This calibration depends on the prescription
chosen for the extra-mixing, but we find that it should be valid also for the
code MESA, provided the same prescription is used. This study constitutes a
first step towards the calibration of the extension of convective cores in
low-mass stars, which will help reduce the uncertainties on the ages of these
stars.Comment: 27 pages, 15 figures, accepted in A&
Piezoelectric and optical response of uniaxially stretched (VDF/TrFE) (75/25) copolymer films
The phase diagram of the poly(vinylidene fluoride-trifluorethylene) (P(VDF-TrFE))
copolymer system shows for VDF contents of 50...85 mol% a ferroelectric (FE)-paraelectric (PE)
phase transition below melting temperature. Investigations on P(VDF-TrFE) 75/25 samples
revealed a slight anisotropic behaviour, which leads to a strongly anisotropic stretching effect both
on the phase transition and on the amount and nature of the FE phase in samples subjected to
mechanical stretching along the main directions of the film.
In this work, both the refractive index n1,2 and the piezoelectric coefficient d33 of mechanically
stretched P(VDF-TrFE) have been measured for samples with different levels of permanent
deformation. These parameters are found to reflect the anisotropy of the permanently deformed
samples. The stretching effect is most pronounced (n1,2) or limited (d33) to the vicinity of the
yielding point of the material. Above the yielding point, almost the piezoelectric d33 coefficient of
the non-deformed sample is observed for samples with large permanent deformation.Fundação para a Ciência e a Tecnologia (FCT) - Grants POCTI/CTM/33501/99, POCI/CTM/59425/2004.PIEZOTECH S.A.CRUP (AI-A-16/04)
Efficient and feasible state tomography of quantum many-body systems
We present a novel method to perform quantum state tomography for
many-particle systems which are particularly suitable for estimating states in
lattice systems such as of ultra-cold atoms in optical lattices. We show that
the need for measuring a tomographically complete set of observables can be
overcome by letting the state evolve under some suitably chosen random circuits
followed by the measurement of a single observable. We generalize known results
about the approximation of unitary 2-designs, i.e., certain classes of random
unitary matrices, by random quantum circuits and connect our findings to the
theory of quantum compressed sensing. We show that for ultra-cold atoms in
optical lattices established techniques like optical super-lattices, laser
speckles, and time-of-flight measurements are sufficient to perform fully
certified, assumption-free tomography. Combining our approach with tensor
network methods - in particular the theory of matrix-product states - we
identify situations where the effort of reconstruction is even constant in the
number of lattice sites, allowing in principle to perform tomography on
large-scale systems readily available in present experiments.Comment: 10 pages, 3 figures, minor corrections, discussion added, emphasizing
that no single-site addressing is needed at any stage of the scheme when
implemented in optical lattice system
On Hastings' counterexamples to the minimum output entropy additivity conjecture
Hastings recently reported a randomized construction of channels violating
the minimum output entropy additivity conjecture. Here we revisit his argument,
presenting a simplified proof. In particular, we do not resort to the exact
probability distribution of the Schmidt coefficients of a random bipartite pure
state, as in the original proof, but rather derive the necessary large
deviation bounds by a concentration of measure argument. Furthermore, we prove
non-additivity for the overwhelming majority of channels consisting of a Haar
random isometry followed by partial trace over the environment, for an
environment dimension much bigger than the output dimension. This makes
Hastings' original reasoning clearer and extends the class of channels for
which additivity can be shown to be violated.Comment: 17 pages + 1 lin
A reversible theory of entanglement and its relation to the second law
We consider the manipulation of multipartite entangled states in the limit of
many copies under quantum operations that asymptotically cannot generate
entanglement. As announced in [Brandao and Plenio, Nature Physics 4, 8 (2008)],
and in stark contrast to the manipulation of entanglement under local
operations and classical communication, the entanglement shared by two or more
parties can be reversibly interconverted in this setting. The unique
entanglement measure is identified as the regularized relative entropy of
entanglement, which is shown to be equal to a regularized and smoothed version
of the logarithmic robustness of entanglement.
Here we give a rigorous proof of this result, which is fundamentally based on
a certain recent extension of quantum Stein's Lemma proved in [Brandao and
Plenio, Commun. Math. 295, 791 (2010)], giving the best measurement strategy
for discriminating several copies of an entangled state from an arbitrary
sequence of non-entangled states, with an optimal distinguishability rate equal
to the regularized relative entropy of entanglement. We moreover analyse the
connection of our approach to axiomatic formulations of the second law of
thermodynamics.Comment: 21 pages. revised versio
Green manure contributing for nutrients cycling in irrigated environments of the Brazilian Semi-Arid.
This study aimed to evaluate the dry matter production and accumulation of nutrients of the aerial phytomass of two types of plant mixtures and the spontaneous vegetation kept between the lines of a mango orchard, under two systems of soil managemen
A Generalization of Quantum Stein's Lemma
We present a generalization of quantum Stein's Lemma to the situation in
which the alternative hypothesis is formed by a family of states, which can
moreover be non-i.i.d.. We consider sets of states which satisfy a few natural
properties, the most important being the closedness under permutations of the
copies. We then determine the error rate function in a very similar fashion to
quantum Stein's Lemma, in terms of the quantum relative entropy.
Our result has two applications to entanglement theory. First it gives an
operational meaning to an entanglement measure known as regularized relative
entropy of entanglement. Second, it shows that this measure is faithful, being
strictly positive on every entangled state. This implies, in particular, that
whenever a multipartite state can be asymptotically converted into another
entangled state by local operations and classical communication, the rate of
conversion must be non-zero. Therefore, the operational definition of
multipartite entanglement is equivalent to its mathematical definition.Comment: 30 pages. (see posting by M. Piani arXiv:0904.2705 for a different
proof of the strict positiveness of the regularized relative entropy of
entanglement on every entangled state). published version
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