Localization from quantum interference in one-dimensional disordered potentials

We show that the tails of the asymptotic density distribution of a quantum wave packet that localizes in the the presence of random or quasiperiodic disorder can be described by the diagonal term of the projection over the eingenstates of the disordered potential. This is equivalent of assuming a phase randomization of the off-diagonal/interference terms. We demonstrate these results through numerical calculations of the dynamics of ultracold atoms in the one-dimensional speckle and quasiperiodic potentials used in the recent experiments that lead to the observation of Anderson localization for matter waves [Billy et al., Nature 453, 891 (2008); Roati et al., Nature 453, 895 (2008)]. For the quasiperiodic case, we also discuss the implications of using continuos or discrete models.Comment: 5 pages, 3 figures; minor changes, references update

SRSF1-dependent nuclear export of C9ORF72 repeat-transcripts: targeting toxic gain-of-functions induced by protein sequestration as a selective therapeutic strategy for neuroprotection

Microsatellite repeat expansions cause several incurable and lethal neurodegenerative disorders including ataxias, myotonic dystrophy, Huntington's disease and C9ORF72-linked amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Abnormal repeat transcripts generated from the expanded loci are substrates of repeat-associated non-AUG (RAN) translation, an unconventional form of translation leading to the production of polymeric repeat proteins with cytotoxic and aggregating properties. The mechanisms involved in the pathogenesis of microsatellite repeat expansion disorders remain a hotly debated topic. They are shared between toxic loss/gain of functions due to intranuclear RNA foci that sequesters RNA-binding proteins and RAN translation of repeat proteins in the cytoplasm. We recently elucidated the molecular mechanism driving the nuclear export of C9ORF72 repeat transcripts and showed for the first time that this pathway can be manipulated to confer neuroprotection. Strikingly, we discovered that intron-retaining C9ORF72 repeat transcripts hijack the physiological NXF1-dependent export pathway by selective RNA-repeat sequestration of SRSF1. Antagonizing SRSF1 and the nuclear export of C9ORF72 repeat transcripts promoted in turn the survival of patient-derived motor neurons and suppressed neurodegeneration-associated motor deficits in Drosophila (Hautbergue et al. Nature Communications 2017; 8:16063). In this invited Research Highlight review, we aim to place this work in the context of our previous studies on the nuclear export of mRNAs, provide a summary of the published research and highlight the significance of these findings as a novel therapeutic strategy for neuroprotection in C9ORF72-ALS/FTD. In addition, we emphasize that protein sequestration, often thought as of inducing loss-of-function mechanisms, can also trigger unwanted protein interactions and toxic gain-of-functions

Stable standing waves for a class of nonlinear Schroedinger-Poisson equations

We prove the existence of orbitally stable standing waves with prescribed $L^2$-norm for the following Schr\"odinger-Poisson type equation \label{intro} %{%{ll} i\psi_{t}+ \Delta \psi - (|x|^{-1}*|\psi|^{2}) \psi+|\psi|^{p-2}\psi=0 \text{in} \R^{3}, %-\Delta\phi= |\psi|^{2}& \text{in} \R^{3},%. when $p\in \{8/3\}\cup (3,10/3)$. In the case $3<p<10/3$ we prove the existence and stability only for sufficiently large $L^2$-norm. In case $p=8/3$ our approach recovers the result of Sanchez and Soler \cite{SS} %concerning the existence and stability for sufficiently small charges. The main point is the analysis of the compactness of minimizing sequences for the related constrained minimization problem. In a final section a further application to the Schr\"odinger equation involving the biharmonic operator is given

Persistent currents in a Bose-Einstein condensate in the presence of disorder

We examine bosonic atoms that are confined in a toroidal, quasi-one-dimensional trap, subjected to a random potential. The resulting inhomogeneous atomic density is smoothened for sufficiently strong, repulsive interatomic interactions. Statistical analysis of our simulations show that the gas supports persistent currents, which become more fragile due to the disorder.Comment: 5 pages, RevTex, 3 figures, revised version, to appear in JLT

Towards the integration of urban sound planning in urban development processes: the study of four test sites within the SONORUS project

Noise pollution in urban environments is today a major problem affecting inhabitants of many European cities. Reducing noise is therefore a necessity. As a result, many cities now have noise action plans comprising concrete actions to tackle noise issues in affected areas. Nevertheless, these often isolated documents only address existing problems. In order to change this practice an integrated strategy is necessary. A new approach to urban sound planning, a holistic approach, is being developed and tested within the SONORUS project and it is described in this paper. SONORUS, the Urban Sound Planner project, is an initial training network (ITN) that is educating researchers in a whole range of acoustic disciplines, as well as in advanced urban planning processes. An essential part of this training is the application of the holistic approach to real test sites. Although this is an ongoing work, a few innovative techniques were already developed and its application to the test sites resulted in improved urban sound planning tools. This paper promotes the discussion about the implications that the holistic approach might have in urban sound planning policies and how it can be a driving force for changing the noise pollution situation in urban environment

Size effects of basic cell in static analysis of sandwich beams

AbstractIn this paper, multilayered sandwich beam structures are considered. Within the scope of static analyses and stiffness design of such type of lightweight and functional structures, size effects of the basic cell are studied both theoretically and numerically in a systematic way for the first time. The direct FE discretization method, the homogenization method and the classical beam theory are examined systematically to reveal, on one hand, the existence of the size effect, and on the other hand, the ability of each method in capturing the size effect upon the static stress distribution and structural deflection. Particularly, limitations of the homogenization method are clarified although the latter is widely applied today in the equivalent modeling and topology design of cellular materials of sandwich structures. By means of the above methods, bending problems of multilayered beams and cellular core sandwiches are solved to illustrate variations of the deflection, stress as well as the computing accuracies in terms of the size of the basic cell. It is shown that the size effect is important when the basic cell has a considerable dimension relative to the structural size and that this effect decreases rapidly with the size reduction of the basic cell. Theoretically, the homogenized result corresponds to the limit solution when the size of the basic cell tends to be infinitely small

Bose-Einstein Condensate in Weak 3d Isotropic Speckle Disorder

The effect of a weak three-dimensional (3d) isotropic laser speckle disorder on various thermodynamic properties of a dilute Bose gas is considered at zero temperature. First, we summarize the derivation of the autocorrelation function of laser speckles in 1d and 2d following the seminal work of Goodman. The goal of this discussion is to show that a Gaussian approximation of this function, proposed in some recent papers, is inconsistent with the general background of laser speckle theory. Then we propose a possible experimental realization for an isotropic 3d laser speckle potential and derive its corresponding autocorrelation function. Using a Fourier transform of that function, we calculate both condensate depletion and sound velocity of a Bose-Einstein condensate as disorder ensemble averages of such a weak laser speckle potential within a perturbative solution of the Gross-Pitaevskii equation. By doing so, we reproduce the expression of the normalfluid density obtained earlier within the treatment of Landau. This physically transparent derivation shows that condensate particles, which are scattered by disorder, form a gas of quasiparticles which is responsible for the normalfluid component

Low-Temperature Specific Heat of an Extreme-Type-II Superconductor at High Magnetic Fields

We present a detailed study of the quasiparticle contribution to the low-temperature specific heat of an extreme type-II superconductor at high magnetic fields. Within a T-matrix approximation for the self-energies in the mixed state of a homogeneous superconductor, the electronic specific heat is a linear function of temperature with a linear-$T$ coefficient $\gamma_s(H)$ being a nonlinear function of magnetic field $H$. In the range of magnetic fields H\agt (0.15-0.2)H_{c2} where our theory is applicable, the calculated $\gamma_s(H)$ closely resembles the experimental data for the borocarbide superconductor YNi$_2$B$_2$C.Comment: 7 pages, 2 figures, to appear in Physical Review

Nucleation of Al3Zr and Al3Sc in aluminum alloys: from kinetic Monte Carlo simulations to classical theory

Zr and Sc precipitate in aluminum alloys to form the compounds Al3Zr and Al3Sc which for low supersaturations of the solid solution have the L12 structure. The aim of the present study is to model at an atomic scale this kinetics of precipitation and to build a mesoscopic model based on classical nucleation theory so as to extend the field of supersaturations and annealing times that can be simulated. We use some ab-initio calculations and experimental data to fit an Ising model describing thermodynamics of the Al-Zr and Al-Sc systems. Kinetic behavior is described by means of an atom-vacancy exchange mechanism. This allows us to simulate with a kinetic Monte Carlo algorithm kinetics of precipitation of Al3Zr and Al3Sc. These kinetics are then used to test the classical nucleation theory. In this purpose, we deduce from our atomic model an isotropic interface free energy which is consistent with the one deduced from experimental kinetics and a nucleation free energy. We test di erent mean-field approximations (Bragg-Williams approximation as well as Cluster Variation Method) for these parameters. The classical nucleation theory is coherent with the kinetic Monte Carlo simulations only when CVM is used: it manages to reproduce the cluster size distribution in the metastable solid solution and its evolution as well as the steady-state nucleation rate. We also find that the capillary approximation used in the classical nucleation theory works surprisingly well when compared to a direct calculation of the free energy of formation for small L12 clusters.Comment: submitted to Physical Review B (2004

Access to infertility consultations: what women tell us about it?

The main objective of the present paper is to evaluate the perception of women concerning the barriers and access to infertility consultations. Socio cultural and economic access to infertility consultations is detached and three municipalities of the northwest of Portugal were chosen as an example of a peripheral country. A quantitative/qualitative study was done with 60 women. Three dimensions were evaluated: geographic and structural and functional access; economic access; and sociocultural access. The main barriers were mainly identified in the last two dimensions. The economic access was the less well evaluated by women being the cost of treatment (medication, and concentration of costs in a short period) difficult to bear. This can justify a greater involvement of the Portuguese Government, by developing policies for the reimbursement of part of the costs. Also, some changes in structural and functional access must be done with special regard to the separation of the infertility consultations from the reproductive medicine section. The setting of the teams, with a follow-up by the same team of health professionals is also needed