Twin-peak quasiperiodic oscillations as an internal resonance

Two inter-related peaks occur in high-frequency power spectra of X-ray lightcurves of several black-hole candidates. We further explore the idea that a non-linear resonance mechanism, operating in strong-gravity regime, is responsible for these quasi-periodic oscillations (QPOs). By extending the multiple-scales analysis of Rebusco, we construct two-dimensional phase-space sections, which enable us to identify different topologies governing the system and to follow evolutionary tracks of the twin peaks. This suggests that the original (Abramowicz and Kluzniak) parametric-resonance scheme can be viewed as an ingenuous account of the QPOs model with an internal resonance. We show an example of internal resonance in a system with up to two critical points, and we describe a general technique that permits to treat other cases in a systematical manner. A separatrix divides the phase-space sections into regions of different topology: inside the libration region the evolutionary tracks bring the observed twin-peak frequencies to an exact rational ratio, whereas in the circulation region the observed frequencies remain off resonance. Our scheme predicts the power should cyclically be exchanged between the two oscillations. Likewise the high-frequency QPOs in neutron-star binaries, also in black-hole sources one expects, as a general property of the non-linear model, that slight detuning pushes the twin-peak frequencies out of sharp resonance.Comment: Accepted for publication in A&A; 11 pages, 6 figure

Effects of zopiclone on blood glucose level, serum lipid concentration and clot lysis time normoglycemic and normolipidemic rats

In normoglycemic and normolipidemic rats the i.p. injection of zopiclone induced an acceleration of fibrinolysis in a dose-dependent bell shaped manner and various changes of the blood glucose level. Total lipids, total cholesterol and triglyceride serum levels remained unaffected by doses of 1.25, 2.5 and 15.0 mg/kg, with the exception of the medium dose (5.0 mg/kg) and the next dose (10.0 mg/kg) which lowered them very significantlly

EAHP European Statements baseline survey 2015

Objectives The 2015 EAHP European Statements survey was related to sections 2, 5 and 6 of the European Statements of Hospital Pharmacy (Statements). In addition to collection of statistical data about the level of implementation of the Statements, it was also intended to identify important barriers to their implementation. Methods The online questionnaire was sent to all hospital pharmacies in EAHP member countries. Data were analysed by researchers from Keele University School of Pharmacy, UK and the EAHP Survey Group. Results There were a total of 949 responses (response rate 18%). In the first part of the survey, data was collected on hospital pharmacy setting. While almost half of hospital pharmacies served over 500 beds, 80% of hospital pharmacies had 10 or less pharmacists. In section B, we gathered evidence about the degree of implementation of sections 2, 5 and 6 of the Statements and the main barriers to and drivers of implementation. Five questions with the lowest implementation level were then further analysed. Only five countries had 50% or more of hospital pharmacies reporting that the hospital pharmacists routinely publish hospital pharmacy practice research. 67% of participants stated that they had contingency plans for medicines shortages. The majority of countries (n=20) have less than half of respondents using computerised decision support to reduce the risk of medication errors. When asked if an audit had been undertaken in the past 3 years to identify priorities in medicines use processes, the mean percentage of positive responses for a country was 58%. Conclusions EAHP has gained an informative overview of the implementation level as well as the barriers to and drivers of implementation in sections 2, 5 and 6. This is essential to inform the plans for EAHP to best support their implementation

A polyconvex transversely-isotropic invariant-based formulation for electro-mechanics: stability, minimisers and computational implementation

The fabrication of evermore sophisticated miniaturised soft robotic components made up of Electro-Active Polymers (EAPs) is constantly demanding parallel development from the in-silico simulation point of view. The incorporation of crystallographic anisotropic micro-architectures, within an otherwise nearly uniform isotropic soft polymer matrix, has shown great potential in terms of advanced three-dimensional actuation (i.e. stretching, bending, twisting), especially at large strains, that is, beyond the onset of geometrical pull-in instabilities. To accommodate for this in-silico response, this paper presents a phenomenological invariant-based polyconvex transversely isotropic framework for the simulation of EAPs at large strains. This research expands previous work developed by Gil and Ortigosa for isotropic EAPs with the help of the pioneering work by Schr\"{o}eder and Neff in the context of polyconvexity for materials endowed with crystallographic architectures in single physics mechanics. The paper also summarises key important results both in terms of the existence of minimisers and material stability. In addition, a series of numerical examples is presented in order to demonstrate the effect that the anisotropic orientation and the contrast of material properties, as well as the level of deformation and electric field, have upon the response of the EAP when subjected to large three-dimensional stretching, bending and torsion, including the possible development of wrinkling

Numerical simulation of the adhesive interface

SGS-2022-00

Diffusion of Mn interstitials in (Ga,Mn)As epitaxial layers

Magnetic properties of thin (Ga,Mn)As layers improve during annealing by out-diffusion of interstitial Mn ions to a free surface. Out-diffused Mn atoms participate in the growth of a Mn-rich surface layer and a saturation of this layer causes an inhibition of the out-diffusion. We combine high-resolution x-ray diffraction with x-ray absorption spectroscopy and a numerical solution of the diffusion problem for the study of the out-diffusion of Mn interstitials during a sequence of annealing steps. Our data demonstrate that the out-diffusion of the interstitials is substantially affected by the internal electric field caused by an inhomogeneous distribution of charges in the (Ga,Mn)As layer.Comment: 11 pages, 5 figure

Internal resonance in non-linear disk oscillations and the amplitude evolution of neutron star kilohertz QPOs

We explore some properties of twin kilohertz quasiperiodic oscillations (QPOs) in a simple toy-model consisting of two oscillation modes coupled by a general nonlinear force. We examine resonant effects by slowly varying the values of the tunable, and nearly commensurable, eigenfrequencies. The behavior of the actual oscillation frequencies and amplitudes during a slow transition through the 3:2 resonance is examined in detail and it is shown that both are significantly affected by the nonlinearities in the governing equations. In particular, the amplitudes of oscillations reflect a resonant exchange of energy between the modes, as a result the initially weaker mode may become dominant after the transition. We note that a qualitatively similar behavior has been recently reported in several neutron star sources by Torok (2008, arXiv:0812.4751), who found that the difference of amplitudes in neutron star twin peak QPOs changes sign as the observed frequency ratio of the QPOs passes through the value 3:2.Comment: 6 pages, 5 figures, accepted by A&