The general goal of drug discovery is to identify novel compounds that are active against a preselected biological target with acceptable pharmacological properties defined by marketed drugs. Scaffold hopping has been widely applied by medicinal chemists to discover equipotent compounds with novel backbones that have improved properties. In this article we classify scaffold hopping into four ma...

Biological redox machines require efficient transfer of electrons and holes for function. Reactions involving multiple tunneling steps, termed "hopping," often promote charge separation within and between proteins that is essential for energy storage and conversion. Here we show how semiclassical electron transfer theory can be extended to include hopping reactions: graphical representations (c...

INTRODUCTION Rhythmic, cyclic human movements may be generated without substantial control from supraspinal structures. There is some evidence that such movements may be largely controlled at the spinal cord level instead. Melvill Jones et al. (1973) described two neural pathways which play important roles during hopping, namely vestibular reflexes (VRs) and functional (long latency response) s...

Simulations and physical robots have shown that hopping and running are possible without sensory feedback. However, stable behavior is often limited to a certain range of the parameters of the open-loop system. Even the simplest of hopping systems can exhibit unstable behavior that results in unpredictable nonperiodic motion as system parameters are adjusted. This paper analyzes the stability o...

This paper proposes an evolutionary optimization approach for optimal hopping of humanoid robots. In the proposed approach, the hopping trajectory is generated by a central pattern generator (CPG). The CPG is one of the biologically inspired approaches, and it generates rhythmic signals by using neural oscillators. During the hopping motion, the disturbance caused by the ground reaction forces ...

Energy. The Los Alamos National Laboratory strongly supports academic freedom and a researcher's right to publish; as an institution, however, the Laboratory does not endorse this viewpoint of a publication or guarantee its technical correctness. Although particle hopping models have been introduced into traac science in the 1950s, their systematic use has only started recently. Two reasons for...

To improve the performance of short-range wireless communications, channel quality must be improved by avoiding interference and multi-path fading. Frequency hopping spread spectrum (FHSS) is a transmission technique where the carrier hops from frequency to frequency. For frequency hopping a mechanism must be designed so that the data can be transmitted in a clear channel and avoid congested ch...

Jamming attack in wireless networks is a severe problem and is easily accomplished by emitting a continuous radio signal. Although the perfect solution to avoid jamming attack does not exist due to the nature of the wireless shared medium, a channel-hopping scheme is considered one of the most effective ways to mitigate jamming attacks. In this paper, I consider various channel-hopping schemes ...

We evaluate the accuracy of Tully's surface hopping algorithm for the spin-boson model in the limit of small to moderate reorganization energy. We calculate transition rates between diabatic surfaces in the exciton basis and compare against exact results from the hierarchical equations of motion; we also compare against approximate rates from the secular Redfield equation and Ehrenfest dynamics...

This paper proposes a new model of a one-legged hopping robot. The one-legged hopping robot is useful in realizing rapid movement such as that of a running animal. Although it has a simple leg mechanism, the dynamics are not simple and require non-linear complex analysis. This means that it is not easy to derive a controller for stable hopping in a systematic way. Therefore, a dynamics-based ap...