Comparison of body mass index of a national cohort of Maltese children over a 3-year interval

Aims: To compare body mass index (BMI) at 7 years and at 9 years of age in a national cohort of children in Malta, born in 2001, and to compare the results with an earlier study carried out in 2007 in this same cohort. Methods: BMI measurement of all children in the second year of formal school and again in the fourth year. Results: In 2008, data was collected from a total of 3435 children (girls 48.9%, boys 51.1%) with a mean age of 6.8 years. The same procedure was carried out in 2010 on the same cohort of children. A total of 3090 children participated in the second round of data collection (girls 49.5%, boys 50.5%). Based on WHO criteria (using the 2007 WHO Child Growth Reference BMI-for-age 5-19 charts), over a quarter of Maltese children aged 7 years were found to be overweight or obese in 2008. This proportion rose to just over 40% when the same cohort was measured in 2010 at the age of 9 years. A significant prevalence of overweight and obese boys was found in Gozo for both studies. Children attending Independent (fee-paying) schools were the least overweight and obese. Discussion: Obesity in childhood in Malta is increasing despite efforts to curb this disease. More emphasis must be made on prevention strategy in childhood as this is a key factor in reducing the burden of morbidity and mortality of childhood disease.peer-reviewe

Dissipation assisted Thouless pumping in the Rice-Mele model

We investigate the effect of dissipation from a thermal environment on topological pumping in the periodically-driven Rice-Mele model. We report that dissipation can improve the robustness of pumping quantisation in a regime of finite driving frequencies. Specifically, in this regime, a low-temperature dissipative dynamics can lead to a pumped charge that is much closer to the Thouless quantised value, compared to a coherent evolution. We understand this effect in the Floquet framework: dissipation increases the population of a Floquet band which shows a topological winding, where pumping is essentially quantised. This finding is a step towards understanding a potentially very useful resource to exploit in experiments, where dissipation effects are unavoidable. We consider small couplings with the environment and we use a Bloch-Redfield quantum master equation approach for our numerics: Comparing these results with an exact MPS numerical treatment we find that the quantum master equation works very well also at low temperature, a quite remarkable fact.Comment: 21 pages, 8 figure

The Response of Interest Rates to the Federal Reserve's Weekly Money Announcements: The "Puzzle" of Anticipated Money

Researchers, using the survey conducted by Money Market Services, Inc., have found that the anticipated component in the Federal Reserve's weekly money supply announcement is negatively correlated with the post- announcement change in market yields. We prove that eliminating a (downward) bias in the measure of anticipated money can, in theory, eliminate this puzzle, but that improving the efficiency of an already unbiased measure cannot. We find, using Canadian as well as U.S. interest rate data, that correcting the downward bias in the survey measure reduces, but does not eliminate, the role of anticipated money.

Quasiparticle Coupled Cluster Theory for Pairing Interactions

We present an extension of the pair coupled cluster doubles (p-CCD) method to quasiparticles and apply it to the attractive pairing Hamiltonian. Near the transition point where number symmetry gets spontaneously broken, the proposed BCS-based p-CCD method yields significantly better energies than existing methods when compared to exact results obtained via solution of the Richardson equations. The quasiparticle p-CCD method has a low computational cost of $\mathcal{O}(N^3)$ as a function of system size. This together with the high quality of results here demonstrated, points to considerable promise for the accurate description of strongly correlated systems with more realistic pairing interactions

Free energy and vibrational entropy difference between ordered and disordered Ni3Al

We have calculated free energy and vibrational entropy differences in Ni3Al between its equilibrium ordered structure and a disordered fcc solid solution. The free energy and entropy differences were calculated using the method of adiabatic switching in a molecular-dynamics formalism. The path chosen for the free-energy calculations directly connects the disordered with the ordered state. The atomic interactions are described by embedded-atom-method potentials. We find that the vibrational entropy difference increases with temperature from 0.14kB/atom at 300 K to 0.22kB/atom at 1200 K. We have calculated the density of states (DOS) of the disordered phase from the Fourier transform of the velocity-velocity autocorrelation function. The disordered DOS looks more like a broadened version of the ordered DOS. Analysis of the partial density of states shows that the Al atoms vibrations are most affected by the compositional disorder. The phonon partial spectral intensities along the 〈100〉 direction show that the vibrational spectrum of the disordered phase contains intensities at optical mode frequencies of the ordered alloy. We find that the volume difference between the ordered and disordered phases plays the most crucial role in the magnitude of the vibrational entropy difference. If the lattice constant of the two phases is set to the same value, the vibrational entropy difference decreases to zero

Decoherence induced by a phase-damping reservoir

A phase damping reservoir composed by $N$-bosons coupled to a system of interest through a cross-Kerr interaction is proposed and its effects on quantum superpo sitions are investigated. By means of analytical calculations we show that: i-) the reservoir induces a Gaussian decay of quantum coherences, and ii-) the inher ent incommensurate character of the spectral distribution yields irreversibility . A state-independent decoherence time and a master equation are both derived an alytically. These results, which have been extended for the thermodynamic limit, show that nondissipative decoherence can be suitably contemplated within the EI D approach. Finally, it is shown that the same mechanism yielding decoherence ar e also responsible for inducing dynamical disentanglement.Comment: 8 pages, 3 figure

Coarse graining of master equations with fast and slow states

We propose a general method for simplifying master equations by eliminating from the description rapidly evolving states. The physical recipe we impose is the suppression of these states and a renormalization of the rates of all the surviving states. In some cases, this decimation procedure can be analytically carried out and is consistent with other analytical approaches, like in the problem of the random walk in a double-well potential. We discuss the application of our method to nontrivial examples: diffusion in a lattice with defects and a model of an enzymatic reaction outside the steady state regime.Comment: 9 pages, 9 figures, final version (new subsection and many minor improvements