Effect of high-frequency excitation on friction induced vibration caused by the combined action of velocity-weakening and mode-coupling

The present article studies the effects of both tangential and normal high-frequency excitations on a two-degree-of-freedom moving-mass-on-belt which represents a minimal model incorporating both velocity-weakening instability (so-called Stribeck effect) and mode-coupling instability (so-called binary flutter). The method of direct partition of motion is employed for studying the characteristics of the system in slow time scale. Linear stability analysis is performed near the equilibrium point of the system for both with and without sinusoidal high-frequency excitation. It is observed that the instability can be suppressed by the tangential high-frequency excitation only for a specific range of strength of excitation. However, stability does not improve under normal high-frequency excitations, though amplitude of the self-excited oscillation can be controlled to some extent. Direct numerical simulations are carried out in MATLAB SIMULINK to validate the analytical predictions.

Global and local excitation and inhibition shape the dynamics of the cortico-striatal-thalamo-cortical pathway

The cortico-striatal-thalamo-cortical (CSTC) pathway is a brain circuit that controls movement execution, habit formation and reward. Hyperactivity in the CSTC pathway is involved in obsessive compulsive disorder, a neuropsychiatric disorder characterized by the execution of repetitive involuntary movements. The striatum shapes the activity of the CSTC pathway through the coordinated activation of two classes of medium spiny neurons (MSNs) expressing D1 or D2 dopamine receptors. The exact mechanisms by which balanced excitation/inhibition of these cells controls the network dynamics of the CSTC pathway remain unclear. Here we use non-linear modeling of neuronal activity and bifurcation theory to investigate how global and local changes in excitation/inhibition of MSNs regulate the activity of the CSTC pathway. Our findings indicate that a global and proportionate increase in excitation/inhibition pushes the system to states of generalized hyper-activity throughout the entire CSTC pathway. Certain disproportionate changes in global excitation/inhibition trigger network oscillations. Local changes in the excitation/inhibition of MSNs generate specific oscillatory behaviors in MSNs and in the CSTC pathway. These findings indicate that subtle changes in the relative strength of excitation/inhibition of MSNs can powerfully control the network dynamics of the CSTC pathway in ways that are not easily predicted by its synaptic connections.

Simulation and Analysis on the Best Range of Lift-Off Values in MFL Testing

As a nondestructive testing method, the magnetic flux leakage (MFL) testing technique is widely used for the testing of surface and near-surface areas in ferromagnetic materials. The MFL field is influenced by parameters of defects, strength of excitation, sensor lift-off value and electromagnetic noises etc. A 2-D finite element method (FEM) simulation model is established in this paper to analyze the influence of lift-off values under the condition of mechanical vibration and electromagnetic noises. The distribution of the MFL field peak for different lift-off values and different depth defects is presented. The defect quantization errors caused by the mechanical vibration and electromagnetic noises are introduced to analyze the influence of lift-off values and electromagnetic noises. The best range of lift-off values can be determined from the results of error analysis. It is effective to improve the measuring accuracy in practical MFL testing.

Electrocortical Correlates of Temperament

The aim of this study was to investigate the relationship between three temperament dimensions: strength of excitation, strength of inhibition and mobility measured by Pavlov’s Temperament Survey (PTS), and amplitudes and latencies of evoked brain potentials (N1, P2, N2, P3 & SW) measured by a visual oddball paradigm in two blocks. The participants were female psychology students (N=54) with mean age of 20. Significant positive correlations were determined between amplitudes of N1-P2-N2-P3 components and strength of excitation and mobility in the first and second block, mostly on parietal electrodes, as well as significant negative correlations of amplitudes of N1-P2-N2-P3 components and strength of inhibition. Considering measurement limitations important future study directions have been given.

Temporal Selectivity in Midbrain Electrosensory Neurons Identified by Modal Variation in Active Sensing

Mormyrid weakly electric fish actively sense their surroundings by continuously emitting discrete pulses of electricity separated by varying intervals of silence. The temporal pattern of this pulsing behavior is related to context. While resting in the absence of an overt stimulus, baseline interpulse intervals (IPIs) mostly range 200–450 ms, and sequential variation is relatively high. Spontaneously, or following the presentation of a novel stimulus, IPIs transiently shorten during the performance of an electromotor “burst” display. We made intracellular whole cell recordings in vivo from neurons in the lateral nucleus of the torus semicircularis while the fish's dynamic pulsing behavior modified the temporal pattern of stimulation. Stimulation was designed to simulate the spatial patterns of AM that occur during the electrolocation of a resistive object. We discovered that toral neurons selectively respond to stimulation during a particular mode of electromotor activity. Two types of temporally selective neurons were discovered: baseline-selective neurons that displayed significantly higher postsynaptic potential (PSP) amplitude and spike count per electric organ discharge (EOD) during baseline electromotor activity and burst-selective neurons that displayed significantly higher PSP amplitude and spike count per EOD during electromotor burst displays. Interval-dependent changes in the strength of excitation and inhibition contributed to their selectivity.

Exploration of the Benefits of an Activity-Specific Test of Temperament

The Structure of Temperament Questionnaire (STQ) was proposed by Rusalov in 1989 and subsequently tested in five languages. The questionnaire assesses four temperamental traits (Ergonicity, Plasticity, Tempo, and Emotionality) in three separate areas of activity: physical, verbal-social, and intellectual. The scales are all activity-specific. In 775 Canadian subjects, two temperament tests were compared, both developed on the basis of Pavlovian studies of the nervous system: the activity-specific approach (STQ) and the nonspecific Pavlovian Temperamental Survey (PTS). More significant sex differences were found on activity-specific scales of the STQ than on the nonspecific PTS scales. The pattern of correlations between the STQ scales and the time taken on an experimental task requiring a prolonged and intense word-assessment activity showed stronger correlations with the specific scales of the STQ measuring the dynamic aspects of social-verbal activity, and not with the PTS Strength of Excitation scale, which is based on a “general arousal” concept. The results supported the separation of temperament traits related to three different types of activities and opposed to “general arousal” theories of temperament.