Stochastic resonance in electrical circuits—II: Nonconventional stochastic resonance.

Stochastic resonance (SR), in which a periodic signal in a nonlinear system can be amplified by added noise, is discussed. The application of circuit modeling techniques to the conventional form of SR, which occurs in static bistable potentials, was considered in a companion paper. Here, the investigation of nonconventional forms of SR in part using similar electronic techniques is described. In the small-signal limit, the results are well described in terms of linear response theory. Some other phenomena of topical interest, closely related to SR, are also treate

Stochastic resonance in electrical circuits—I: Conventional stochastic resonance.

Stochastic resonance (SR), a phenomenon in which a periodic signal in a nonlinear system can be amplified by added noise, is introduced and discussed. Techniques for investigating SR using electronic circuits are described in practical terms. The physical nature of SR, and the explanation of weak-noise SR as a linear response phenomenon, are considered. Conventional SR, for systems characterized by static bistable potentials, is described together with examples of the data obtainable from the circuit models used to test the theory

Spin-correlations and magnetic structure in an Fe monolayer on 5d transition metal surfaces

We present a detailed first principles study on the magnetic structure of an Fe monolayer on different surfaces of 5d transition metals. We use the spin-cluster expansion technique to obtain parameters of a spin model, and predict the possible magnetic ground state of the studied systems by employing the mean field approach and in certain cases by spin dynamics calculations. We point out that the number of shells considered for the isotropic exchange interactions plays a crucial role in the determination of the magnetic ground state. In the case of Ta substrate we demonstrate that the out-of-plane relaxation of the Fe monolayer causes a transition from ferromagnetic to antiferromagnetic ground state. We examine the relative magnitude of nearest neighbour Dzyaloshinskii-Moriya (D) and isotropic (J) exchange interactions in order to get insight into the nature of magnetic pattern formations. For the Fe/Os(0001) system we calculate a very large D/J ratio, correspondingly, a spin spiral ground state. We find that, mainly through the leading isotropic exchange and Dzyaloshinskii-Moriya interactions, the inward layer relaxation substantially influences the magnetic ordering of the Fe monolayer. For the Fe/Re(0001) system characterized by large antiferromagnetic interactions we also determine the chirality of the $120^{\circ}$ N\'eel-type ground state.Comment: 15 pages, 8 figures, 2 table

Class 1 PI3K clinical candidates and recent inhibitor design strategies: a medicinal chemistry perspective

Phosphatidylinositol 3-kinases (PI3Ks) are a family of lipid kinases that phosphorylate the 3-OH of the inositol ring of phosphoinositides, and deregulation of this pathway has implications in many diseases. The search for novel PI3K inhibitors has been at the forefront of academic and industrial medicinal chemistry with over 600 medicinal chemistry-based publications and patents appearing to date, leading to 38 clinical candidates and the launch of two drugs, idelalisib in 2014 and copanlisib in 2017. This Perspective will discuss medicinal chemistry design approaches to novel isoform-selective inhibitors through consideration of brief case histories of compounds that have progressed into clinical development or that have revealed new structural motifs in this highly competitive area of research

Can’t get you out of my mind: Empathy, Distress, and Recurring Thoughts about a Person in Need

Research suggests that empathic concern and distress give rise to different patterns of helping behavior. It has been proposed that this difference is caused by the effects of these emotions on recurrent thoughts about the person in need. However, no research has directly investigated this potential explanation. To remedy this, we tested the hypotheses that distress, but not empathic concern, is associated with both anticipated recurring thoughts (Study 1) and experienced recurring thoughts (Study 2) about a victim. We also tested the hypothesis that distress is associated with thoughts about the victim, whereas empathic concern is associated with thoughts about the victim’s situation (Study 3), which is potentially a consequence of the motives associated with each emotion. Lastly, we assessed the causal relations between distress, empathic concern, and recurrent thoughts (Study 4). Overall, results demonstrate a distinctive, and important, pattern of associations among empathic concern, distress, and different forms of recurrent thoughts about an emotion-eliciting stimulus

Cluster coherent potential approximation for electronic structure of disordered alloys

We extend the single-site coherent potential approximation (CPA) to include the effects of non-local disorder correlations (alloy short-range order) on the electronic structure of random alloy systems. This is achieved by mapping the original Anderson disorder problem to that of a selfconsistently embedded cluster. This cluster problem is then solved using the equations of motion technique. The CPA is recovered for cluster size $N_{c}=1$, and the disorder averaged density-of-states (DOS) is always positive definite. Various new features, compared to those observed in CPA, and related to repeated scattering on pairs of sites, reflecting the effect of SRO are clearly visible in the DOS. It is explicitly shown that the cluster-CPA method always yields positive-definite DOS. Anderson localization effects have been investigated within this approach. In general, we find that Anderson localization sets in before band splitting occurs, and that increasing partial order drives a continuous transition from an Anderson insulator to an incoherent metal.Comment: 7 pages, 6 figures. submitted to PR

Changing the Magnetic Configurations of Nanoclusters Atom-by-Atom

The Korringa-Kohn-Rostoker Green (KKR) function method for non-collinear magnetic structures was applied on Mn and Cr ad-clusters deposited on the Ni(111) surface. By considering various dimers, trimers and tetramers, a large amount of collinear and non-collinear magnetic structures is obtained. Typically all compact clusters have very small total moments, while the more open structures exhibit sizeable total moments, which is a result of the complex frustration mechanism in these systems. Thus, as the motion of a single adatom changes the cluster structure from compact to open and vice versa, this can be considered as a magnetic switch, which via the local exchange field of the adatom allows to switch the cluster moment on and off, and which might be useful for future nanosize information storage.Comment: 7 page

Integrating biological data into ocean observing systems: the future role of OBIS

The future data needs of ocean science and ocean resource management will require a more seamless and accessible coupling of biological data with physical oceanographic processes. This bio-physical data framework will be built through the active integration of data from an extensive variety of sensors, observers, platforms and data archives across a wide range of space and time scales. This necessary synthesis of raw biological data into useful information and potentially new understanding is dependent on both new developments in ocean exploration as well as developments in information systems and informatics. The Ocean Biogeographic Information System (OBIS) is poised to play a significant and expanding role in the evolving ocean observation system

Light atom quantum oscillations in UC and US

High energy vibrational scattering in the binary systems UC and US is measured using time-of-flight inelastic neutron scattering. A clear set of well-defined peaks equally separated in energy is observed in UC, corresponding to harmonic oscillations of the light C atoms in a cage of heavy U atoms. The scattering is much weaker in US and only a few oscillator peaks are visible. We show how the difference between the materials can be understood by considering the neutron scattering lengths and masses of the lighter atoms. Monte Carlo ray tracing is used to simulate the scattering, with near quantitative agreement with the data in UC, and some differences with US. The possibility of observing anharmonicity and anisotropy in the potentials of the light atoms is investigated in UC. Overall the observed data is well accounted for by considering each light atom as a single atom isotropic quantum harmonic oscillator.Comment: 10 pages, 8 figure