Approximation of small-amplitude weakly coupled oscillators with discrete nonlinear Schrodinger equations

Small-amplitude weakly coupled oscillators of the Klein-Gordon lattices are approximated by equations of the discrete nonlinear Schrodinger type. We show how to justify this approximation by two methods, which have been very popular in the recent literature. The first method relies on a priori energy estimates and multi-scale decompositions. The second method is based on a resonant normal form theorem. We show that although the two methods are different in the implementation, they produce equivalent results as the end product. We also discuss applications of the discrete nonlinear Schrodinger equation in the context of existence and stability of breathers of the Klein--Gordon lattice

Existence and continuous approximation of small amplitude breathers in 1D and 2D Klein--Gordon lattices

We construct small amplitude breathers in 1D and 2D Klein--Gordon infinite lattices. We also show that the breathers are well approximated by the ground state of the nonlinear Schroedinger equation. The result is obtained by exploiting the relation between the Klein Gordon lattice and the discrete Non Linear Schroedinger lattice. The proof is based on a Lyapunov-Schmidt decomposition and continuum approximation techniques introduced in [7], actually using its main result as an important lemma

Quantifying Forearm Muscle Activity during Wrist and Finger Movements by Means of Multi-Channel Electromyography.

The study of hand and finger movement is an important topic with applications in prosthetics, rehabilitation, and ergonomics. Surface electromyography (sEMG) is the gold standard for the analysis of muscle activation. Previous studies investigated the optimal electrode number and positioning on the forearm to obtain information representative of muscle activation and robust to movements. However, the sEMG spatial distribution on the forearm during hand and finger movements and its changes due to different hand positions has never been quantified. The aim of this work is to quantify 1) the spatial localization of surface EMG activity of distinct forearm muscles during dynamic free movements of wrist and single fingers and 2) the effect of hand position on sEMG activity distribution. The subjects performed cyclic dynamic tasks involving the wrist and the fingers. The wrist tasks and the hand opening/closing task were performed with the hand in prone and neutral positions. A sensorized glove was used for kinematics recording. sEMG signals were acquired from the forearm muscles using a grid of 112 electrodes integrated into a stretchable textile sleeve. The areas of sEMG activity have been identified by a segmentation technique after a data dimensionality reduction step based on Non Negative Matrix Factorization applied to the EMG envelopes. The results show that 1) it is possible to identify distinct areas of sEMG activity on the forearm for different fingers; 2) hand position influences sEMG activity level and spatial distribution. This work gives new quantitative information about sEMG activity distribution on the forearm in healthy subjects and provides a basis for future works on the identification of optimal electrode configuration for sEMG based control of prostheses, exoskeletons, or orthoses. An example of use of this information for the optimization of the detection system for the estimation of joint kinematics from sEMG is reported

Why small particle fixed dose triple therapy? An excursus from COPD pathology to pharmacological treatment evolution

Although bronchodilators are the cornerstone in chronic obstructive pulmonary disease (COPD) therapy, the treatment with a single-agent bronchodilator may not provide adequate symptoms control in COPD. The combination of drugs with different mechanisms of action may be more effective in inducing bronchodilation and preventing exacerbations, with a lower risk of side-effects in comparison with the increase of the dose of a single molecule. Several studies comparing the triple therapy with the association of long-acting ß2 agonist (LABA)/inhaled corticosteroid (ICS) or long-acting muscarinic antagonist (LAMA)/LABA reported improvement of lung function and quality of life. A significant reduction in moderate/severe exacerbations has been observed with a fixed triple combination of beclometasone dipropionate (BDP), formoterol fumarate (FF) and glycopyrronium (G) in a single inhaler. The TRILOGY, TRINITY and TRIBUTE studies have provided confirming evidence for a clinical benefit of triple therapy over ICS/LABA combination treatment, LAMA monotherapy and LABA/LAMA combination, with prevention of exacerbations being a key finding. A pooled post hoc analysis of the published clinical studies involving BDP/FF/G fixed combination demonstrated a reduction in fatal events in patients treated with ICS-containing medications, with a trend of statistical significance [hazard ratio = 0.72, 95% confidence interval (CI) 0.50–1.02, p = 0.066], that becomes significant if we consider reduction in fatal events for non-respiratory reasons (hazard ratio = 0.65, 95% CI 0.43–0.97, p = 0.037). In conclusion, a fixed combination of more drugs in a single inhaler can improve long-term adherence to the therapy, reducing the risk of exacerbations and hospital resources utilization. The twice a day administration may provide a better coverage of night, particularly in COPD patients who are highly symptomatic. The inhaled extrafine formulation that allows drug deposition in both large and small – peripheral – airways, is the value added

Surgically Returning to Randomized lib(c)

To strengthen systems against code injection attacks, the write or execute only policy (W + X) and address space layout randomization (ASLR) are typically used in combination. The former separates data and code, while the latter randomizes the layout of a process. In this paper we present a new attack to bypass W + X and ASLR. The state-of-the-art attack against this combination of protections is based on brute-force, while ours is based on the leakage of sensitive information about the memory layout of the process. Using our attack an attacker can exploit the majority of programs vulnerable to stack-based buffer overflows surgically, i.e., in a single attempt. We have estimated that our attack is feasible on 95.6% and 61.8% executables (of medium size) for Intel x86 and x86-64 architectures, respectively. We also analyze the effectiveness of other existing protections at preventing our attack. We conclude that position independent executables (PIE) are essential to complement ASLR and to prevent our attack. However, PIE requires recompilation, it is often not adopted even when supported, and it is not available on all ASLR-capable operating systems. To overcome these limitations, we propose a new protection that is as effective as PIE, does not require recompilation, and introduces only a minimal overhead

Inhibition of the Nicotinic Acetylcholine Receptors by Cobra Venom α-Neurotoxins: Is There a Perspective in Lung Cancer Treatment?

Nicotine exerts its oncogenic effects through the binding to nicotinic acetylcholine receptors (nAChRs) and the activation of downstream pathways that block apoptosis and promote neo-angiogenesis. The nAChRs of the α7 subtype are present on a wide variety of cancer cells and their inhibition by cobra venom neurotoxins has been proposed in several articles and reviews as a potential innovative lung cancer therapy. However, since part of the published results was recently retracted, we believe that the antitumoral activity of cobra venom neurotoxins needs to be independently re-evaluated

Many-body perturbation theory calculations using the yambo code

International audienceyambo is an open source project aimed at studying excited state properties of condensed matter systems from first principles using many-body methods. As input, yambo requires ground state electronic structure data as computed by density functional theory codes such as quantum-espresso and abinit. yambo's capabilities include the calculation of linear response quantities (both independent-particle and including electron-hole interactions), quasi-particle corrections based on the GW formalism, optical absorption, and other spectroscopic quantities. Here we describe recent developments ranging from the inclusion of important but oft-neglected physical effects such as electron-phonon interactions to the implementation of a real-time propagation scheme for simulating linear and non-linear optical properties. Improvements to numerical algorithms and the user interface are outlined. Particular emphasis is given to the new and efficient parallel structure that makes it possible to exploit modern high performance computing architectures. Finally, we demonstrate the possibility to automate workflows by interfacing with the yambopy and AiiDA software tools