A periodic elastic medium in which periodicity is relevant

We analyze, in both (1+1)- and (2+1)- dimensions, a periodic elastic medium in which the periodicity is such that at long distances the behavior is always in the random-substrate universality class. This contrasts with the models with an additive periodic potential in which, according to the field theoretic analysis of Bouchaud and Georges and more recently of Emig and Nattermann, the random manifold class dominates at long distances in (1+1)- and (2+1)-dimensions. The models we use are random-bond Ising interfaces in hypercubic lattices. The exchange constants are random in a slab of size $L^{d-1} \times \lambda$ and these coupling constants are periodically repeated along either {10} or {11} (in (1+1)-dimensions) and {100} or {111} (in (2+1)-dimensions). Exact ground-state calculations confirm scaling arguments which predict that the surface roughness $w$ behaves as: $w \sim L^{2/3}, L \ll L_c$ and $w \sim L^{1/2}, L \gg L_c$, with $L_c \sim \lambda^{3/2}$ in $(1+1)$-dimensions and; $w \sim L^{0.42}, L \ll L_c$ and $w \sim \ln(L), L \gg L_c$, with $L_c \sim \lambda^{2.38}$ in $(2+1)$-dimensions.Comment: Submitted to Phys. Rev.

On the thermodynamics of first-order phase transition smeared by frozen disorder

The simplified model of first-order transition in a media with frozen long-range transition-temperature disorder is considered. It exhibits the smearing of the transition due to appearance of the intermediate inhomogeneous phase with thermodynamics described by the ground state of the short-range random-field Ising model. Thus the model correctly reproduce the persistence of first-order transition only in dimensions d > 2, which is found in more realistic models. It also allows to estimate the behavior of thermodynamic parameters near the boundaries of the inhomogeneous phase.Comment: 4 page

Magnetic nanocomposites at microwave frequencies

Most conventional magnetic materials used in the electronic devices are ferrites, which are composed of micrometer-size grains. But ferrites have small saturation magnetization, therefore the performance at GHz frequencies is rather poor. That is why functionalized nanocomposites comprising magnetic nanoparticles (e.g. Fe, Co) with dimensions ranging from a few nm to 100 nm, and embedded in dielectric matrices (e.g. silicon oxide, aluminium oxide) have a significant potential for the electronics industry. When the size of the nanoparticles is smaller than the critical size for multidomain formation, these nanocomposites can be regarded as an ensemble of particles in single-domain states and the losses (due for example to eddy currents) are expected to be relatively small. Here we review the theory of magnetism in such materials, and we present a novel measurement method used for the characterization of the electromagnetic properties of composites with nanomagnetic insertions. We also present a few experimental results obtained on composites consisting of iron nanoparticles in a dielectric matrix.Comment: 20 pages, 10 figures, 5 table

Response to antipsychotic drugs in treatment-resistant schizophrenia : Conclusions based on systematic review

Peer reviewe

Optimal taxation without state-contingent debt

To recover a version of Barro's (1979) `random walk' tax smoothing outcome, we modify Lucas and Stokey's (1983) economy to permit only risk--free debt. This imparts near unit root like behavior to government debt, independently of the government expenditure process, a realistic outcome in the spirit of Barro's. We show how the risk--free--debt--only economy confronts the Ramsey planner with additional constraints on equilibrium allocations that take the form of a sequence of measurability conditions. We solve the Ramsey problem by formulating it in terms of a Lagrangian, and applying a Parameterized Expectations Algorithm to the associated first--order conditions. The first--order conditions and numerical impulse response functions partially affirm Barro's random walk outcome. Though the behaviors of tax rates, government surpluses, and government debts differ, allocations are very close for computed Ramsey policies across incomplete and complete markets economies.Optimal taxation, incomplete markets, recursive contracts, tax smoothing, parameterized expectations

Aeolian sans ripples: experimental study of saturated states

We report an experimental investigation of aeolian sand ripples, performed both in a wind tunnel and on stoss slopes of dunes. Starting from a flat bed, we can identify three regimes: appearance of an initial wavelength, coarsening of the pattern and finally saturation of the ripples. We show that both initial and final wavelengths, as well as the propagative speed of the ripples, are linear functions of the wind velocity. Investigating the evolution of an initially corrugated bed, we exhibit non-linear stable solutions for a finite range of wavelengths, which demonstrates the existence of a saturation in amplitude. These results contradict most of the models.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Lett. Title changed, figures corrected and simplified, more field data included, text clarifie

Observed Loss of Polar Mesospheric Ozone Following Substorm-Driven Electron Precipitation

Several drivers cause precipitation of energetic electrons into the atmosphere. While some of these drivers are accounted for in proxies of energetic electron precipitation (EEP) used in atmosphere and climate models, it is unclear to what extent the proxies capture substorm‐induced EEP. The energies of these electrons allow them to reach altitudes between 55 and 95 km. EEP‐driven enhanced ionization is known to result in production of HOx and NOx, which catalytically destroy ozone. Substorm‐driven ozone loss has previously been simulated, but has not been observed before. We use mesospheric ozone observations from the Microwave Limb Sounder and Global Ozone Monitoring by Occultation of Stars instruments, to investigate the loss of ozone during substorms. Following substorm onset, we find reductions of polar mesospheric (∼76 km) ozone by up to 21% on average. This is the first observational evidence demonstrating the importance of substorms on the ozone balance within the polar atmosphere

Loving-kindness meditation: a tool to improve healthcare provider compassion, resilience, and patient care

Background: Stress is a critical problem facing many healthcare institutions. The consequences of stress include increased provider burnout and decreased quality of care for patients. Ironically, a key factor that may help buffer the impact of stress on provider well-being and patient health outcomes—compassion—is low in healthcare settings and declines under stress. This gives rise to an urgent question: what practical steps can be taken to increase compassion, thereby benefitting both provider well-being and patient care? Methods: We investigated the relative effectiveness of a short, 10-minute session of loving-kindness meditation (LKM) to increase compassion and positive affect. We compared LKM to a non-compassion positive affect induction (PAI) and a neutral visualization (NEU) condition. Self- and other-focused affect, self-reported measures of social connection, and semi-implicit measures of self-focus were measured pre- and post- meditation using repeated measures ANOVAs and via paired sample t-tests for follow-up comparisons. Results: Findings show that LKM improves well-being and feelings of connection over and above other positive-affect inductions, at both explicit and implicit levels, while decreasing self-focus in under 10 minutes and in novice meditators. Conclusions: These findings suggest that LKM may be a viable, practical, and time-effective solution for preventing burnout and promoting resilience in healthcare providers and for improving quality of care in patients

Quasi-static cracks and minimal energy surfaces

We compare the roughness of minimal energy(ME) surfaces and scalar ``quasi-static'' fracture surfaces(SQF). Two dimensional ME and SQF surfaces have the same roughness scaling, w sim L^zeta (L is system size) with zeta = 2/3. The 3-d ME and SQF results at strong disorder are consistent with the random-bond Ising exponent zeta (d >= 3) approx 0.21(5-d) (d is bulk dimension). However 3-d SQF surfaces are rougher than ME ones due to a larger prefactor. ME surfaces undergo a ``weakly rough'' to ``algebraically rough'' transition in 3-d, suggesting a similar behavior in fracture.Comment: 7 pages, aps.sty-latex, 7 figure