An Oscillatory Mechanism for Multi-level Storage in Short-term Memory

Oscillatory activity is commonly observed during the maintenance of information in short-term memory, but its role remains unclear. Non-oscillatory models of short-term memory storage are able to encode stimulus identity through their spatial patterns of activity, but are typically limited to either an all-or-none representation of stimulus amplitude or exhibit a biologically implausible exact-tuning condition. Here, we demonstrate a simple phase-locking mechanism by which oscillatory input enables a circuit to generate persistent or sequential activity patterns that encode information not only in their location but also in a discrete set of amplitudes.

Daily rhythms in the transcriptomes of the human parasite Schistosoma mansoni

The consequences of the earth’s daily rotation have led to 24-hour biological rhythms in most organisms. Parasites have daily rhythms, which, when in synchrony with host rhythms, optimize their fitness. Using round-the-clock transcriptomics of male and female Schistosoma mansoni blood flukes we have discovered the first 24-hour molecular oscillations in a metazoan parasite, and gained insight into its daily rhythms. We show that expression of ∼2% of its genes followed diel cycles. Rhythmic processes, in synchrony in both sexes, included a night-time stress response and a day-time metabolic ‘rush hour’. These 24hr rhythms may be driven by host rhythms and/or generated by an intrinsic circadian clock. However, canonical core clock genes are lacking, suggesting an unusual oscillatory mechanism or loss of a functional clock. The daily rhythms in biology identified here, may promote within-host survival and between-host transmission, and are important for the development and delivery of therapeutics against schistosomiasis.

High-torque variator with rocker oscillating mechanism

The design and the theory of calculation of the rocker oscillatory mechanism are presented, which provides an increase in more than 2 times the oscillation range of the oscillating shaft in comparison with the known oscillating mechanisms. The device allows to significantly increase the effectiveness of a high-torque non-frictiontype variator: it increases the variation range, reduces the cost of the design and reduces the metal consumption of the variator. Keywords: adjustable oscillating mechanism, cam non-friction high-torque variator [email protected]

MATHEMATICAL MODELING OF A MULTI-INERT OSCILLATORY MECHANISM

It is noted that the free harmonic vibrations of a classical pendulum are due to the mutual conversion of the kinetic energy of the load intothe potential energy of the spring. Oscillators with a different nature of energy exchange have been developed, for example, by converting the kinetic energy of a load into the energy of a magnetic field of a solenoid or the energy of an electric field of a capacitor. All these oscillatory systems and the like were a prerequisite for the creation of a biinert oscillator,in which the acceleration of one load occurs due to the braking of another, i. e. only kinetic energies are exchanged. The aim of the work is mathematical modeling of a multi-inert oscillatory mechanism. The main research methods in the framework of this work are methods of mathematical modeling and analysis. The methods used make it possible to obtain a reliable description of the studied objects. Inthe proposed multi-inert oscillator, inert bodies of mass m each carry out harmonic oscillations due to the mutual exchange of kinetic energy. The potential energy of the springs is not requiredfor this. Body vibrationsare free. A feature of a multi-inert oscillator is that the frequency of itsfree oscillations is not fixed and is determined mainly by the initial conditions. This feature can be very useful for technical applications, for example, for self-neutralization of mechanical reactive (inertial) power. n-gon, formed by inert bodies, carries out complex motion – orbital rotation around the center of coordinates and spin rotation around its axis passing through the center of the n-gon. Moreover, each load performs linear harmonic oscillations along its guide. With the arrangement of the guiding weights not in the form of a star, but in parallel to each other, the angles between the corresponding cranks must be 360/n degrees.

MULTI–INERT OSCILLATORY MECHANISM

A mechanical oscillatory system with homogeneous elements, namely, with n massive loads (multi– inert oscillator), is considered. The possibility of the appearance of free harmonic oscillations of loads in such a system is shown. Unlike the classical spring pendulum, the oscillations of which are due to the mutual conversion of the kinetic energy of the load into the potential energy of the spring, in a multi–inert oscillator, the oscillations are due to the mutual conversion of only the kinetic energies of the goods. In this case, the acceleration of some loads occurs due to the braking of others. A feature of the multi–inert oscillator is that its free oscillation frequency is not fixed and is determined mainly by the initial conditions. This feature can be very useful for technical applications, for example, for self–neutralization of mechanical reactive (inertial) power in oscillatory systems.

A new cognition on oscillatory thermocapillary convection for high Prandtl number fluids

A direct numerical simulations on the oscillatory thermocapillary convection in a non-axisymmetric liquid bridge of high Pr fluids under normal gravity has been conducted by using a new method of mass conserving Level Set method for capturing any micro-scale migrations of free surface. Against the former studies, the oscillatory behaviors of surface flow (the perturbation of velocity, temperature, and free surface) and flow pattern have been quantitatively investigated simultaneously for the first time. The present results show that the instability of thermocapillary convection originates from the oscillations of velocity, temperature, and free surface at the hot corner. The velocity oscillation responds slowly to the temperature oscillation, which are opposite in transfer direction for each other, resulting in the free surface oscillation. The oscillatory thermocapillary convection in the liquid bridge is eventually excited by the coupling effects of these three kinds of oscillations, which discloses clearly the oscillatory mechanism of thermocapillary convection for high Pr fluids.

Mathematical model for volcanic harmonic tremors

Harmonic tremors consist in the release of infrasonic energy associated with volcanic activity. The typical frequency range of harmonic tremors is 0.1–12 Hz. We suppose that the harmonic tremors are due to the formation of bubbles entrapped in cavities that oscillate converting thermal energy into mechanic energy. Reproducing the natural phenomenon through an experimental apparatus, we propose here a mathematical model to describe the oscillatory mechanism and to detect the frequency as a function of the main physical parameters. We show that the frequency obtained through the model is in agreement with the one obtained through experimental measurements and with the data available from the literature, proving the consistency of the proposed model.

Dynamic regulation of interregional cortical communication by slow brain oscillations during working memory

Transiently storing information and mentally manipulating it is known as working memory. These operations are implemented by a distributed, fronto-parietal cognitive control network in the brain. The neural mechanisms controlling interactions within this network are yet to be determined. Here, we show that during a working memory task the brain uses an oscillatory mechanism for regulating access to prefrontal cognitive resources, dynamically controlling interactions between prefrontal cortex and remote neocortical areas. Combining EEG with non-invasive brain stimulation we show that fast rhythmical brain activity at posterior sites are nested into prefrontal slow brain waves. Depending on cognitive demand this high frequency activity is nested into different phases of the slow wave enabling dynamic coupling or de-coupling of the fronto-parietal control network adjusted to cognitive effort. This mechanism constitutes a basic principle of coordinating higher cognitive functions in the human brain.