Autonomic oscillatory activities exist in almost every living thing and most of them are produced by rhythmic activities of the corresponding neural systems (locomotion, respiration, heart beat, etc.). This paper mathematically discusses sustained oscillations generated by mutual inhibition of the neurons which are represented by a continuous-variable model with a kind of fatigue or adaptation effect. If the neural network has no stable stationary state for constant input stimuli, it will generate and sustain some oscillation for any initial state and for any disturbance. Some sufficient conditions for that are given to three types of neural networks: lateral inhibition networks of linearly arrayed neurons, symmetric inhibition networks and cyclic inhibition networks. The result suggests that the adaptation of the neurons plays a very important role for the appearance of the oscillations. Some computer simulations of rhythmic activities are also presented for cyclic inhibition networks consisting of a few neurons.

The locomotive motion in animals is produced in some central neural units, and basically no sensory signal from peripheral receptors is necessary to induce it. The rhythm generators do not only produce rhythms but also alter their frequencies and patterns. This paper presents some mathematical models of the neural rhythm generators and discusses various aspects of the frequency and pattern control in them.

Recently, thermally activated delayed fluorescence (TADF) materials have received increasing attention as effective emitters for organic light-emitting diodes (OLEDs). However, most of them are usually employed as dopants in a host material. In this report, carbazole dendrimers with a triphenyl-s-triazine core are reported, which are the first solution-processable, non-doped, high-molecular-weight TADF materials. The dendrimers were obtained by a new and facile synthetic route using the tert-butyldimethylsilyl moiety as a protecting group. All dendrimers showed TADF in toluene. Measurements of the temperature-dependent luminescence lifetime revealed that spin-coated neat films also showed TADF with moderate quantum yields. OLED devices incorporating these dendrimers as spin-coated emitting layers gave external quantum efficiencies of up to a 3.4 %, which suggests that this device is harvesting triplet excitons. This result indicates that carbazole dendrimers with attached acceptors are potential TADF materials owing to their polarized electronic structure (with HOMO-LUMO separation).

Abstnd: In blind source separation the numh:r of the m o r s is usually assumed to be equal to that of the sources. In this c a x a n i n w ' appears with which any lmcar transform of an estimated source signal can also be considered another estimation of the source signal. M m w in the case that the number of the msors is greater than that of the sou~ces, another indctmninacy arises due to the redundancy of the sensors. Although these indctaminacies arc often mnsidercd unsubstantial and have k n eliminated without defmite bass, an appropriate "alization of the separator is to enhance the acauacy of the separation resdlt parlicularly in the case of convolutive mixture. This papa shows two principles for eliminating these inddmninacie:i: (i) minimal distortion principle and (ii) inverse minimal distortion principle.

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