Short term synaptic depression model—Analytical solution and analysis

In this article we present analytical solutions of the single and pair pulse time evolution of a plastic neocortical synapse described by the TM-model. We show that this model is equivalent to the receptor-desensitization model with three kinetic states. For the TM-model we derive the analytical form of a measure of paired pulse depression. We analyze the sensitivity of the synaptic depression phenomenon on model parameters and derive the relative importance of each of the parameters. The closed form of the measure of synaptic depression allows fitting the model to experimental data. The fitted parameters are used to make predictions about the asymptotic properties of the postsynaptic currents. We show that for synapses with the ratio of inactivation and recovery rates of the same order, the synaptic depression does not preclude the rate-coding of information: e.g. in the pyramid–pyramid connections of adult rat neocortex, rate-coding is possible for higher frequencies

Wykorzystanie satelitów w rozsiewczej radiofonii i telewizji. Przegląd Zagadnień Łączności, 1971, nr 3 (102)

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Stan obecny i przewidywany rozwój telekomunikacji. Przegląd Zagadnień Łączności, 1970, nr 5 (98)

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Nowoczesna radiokomunikacja mikrofalowa. Przegląd Zagadnień Łączności, 1963, nr 1 (16)

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Musical Ratios in Sounds from the Human Cochlea

The physiological roots of music perception are a matter of long-lasting debate. Recently light on this problem has been shed by the study of otoacoustic emissions (OAEs), which are weak sounds generated by the inner ear following acoustic stimulation and, sometimes, even spontaneously. In the present study, a high-resolution time–frequency method called matching pursuit was applied to the OAEs recorded from the ears of 45 normal volunteers so that the component frequencies, amplitudes, latencies, and time-spans could be accurately determined. The method allowed us to find that, for each ear, the OAEs consisted of characteristic frequency patterns that we call resonant modes. Here we demonstrate that, on average, the frequency ratios of the resonant modes from all the cochleas studied possessed small integer ratios. The ratios are the same as those found by Pythagoras as being most musically pleasant and which form the basis of the Just tuning system. The statistical significance of the results was verified against a random distribution of ratios. As an explanatory model, there are attractive features in a recent theory that represents the cochlea as a surface acoustic wave resonator; in this situation the spacing between the rows of hearing receptors can create resonant cavities of defined lengths. By adjusting the geometry and the lengths of the resonant cavities, it is possible to generate the preferred frequency ratios we have found here. We conclude that musical perception might be related to specific geometrical and physiological properties of the cochlea

Divergent Cortical Generators of MEG and EEG during Human Sleep Spindles Suggested by Distributed Source Modeling

Background: Sleep spindles are,1-second bursts of 10–15 Hz activity, occurring during normal stage 2 sleep. In animals, sleep spindles can be synchronous across multiple cortical and thalamic locations, suggesting a distributed stable phaselocked generating system. The high synchrony of spindles across scalp EEG sites suggests that this may also be true in humans. However, prior MEG studies suggest multiple and varying generators. Methodology/Principal Findings: We recorded 306 channels of MEG simultaneously with 60 channels of EEG during naturally occurring spindles of stage 2 sleep in 7 healthy subjects. High-resolution structural MRI was obtained in each subject, to define the shells for a boundary element forward solution and to reconstruct the cortex providing the solution space for a noise-normalized minimum norm source estimation procedure. Integrated across the entire duration of all spindles, sources estimated from EEG and MEG are similar, diffuse and widespread, including all lobes from both hemispheres. However, the locations, phase and amplitude of sources simultaneously estimated from MEG versus EEG are highly distinct during the same spindles. Specifically, the sources estimated from EEG are highly synchronous across the cortex, whereas those from MEG rapidly shift in phase, hemisphere, and the location within the hemisphere. Conclusions/Significance: The heterogeneity of MEG sources implies that multiple generators are active during huma

Broadband satellite systems in telecommunication networks

W artykule dokonano przeglądu metod stosowanych w sieciach satelitarnych z satelitami geostacjonarnymi i niegeostacjonarnymi w celu realizacji szerokopasmowych służb łączności z naziemnymi stacjami stacjonarnymi i przenośnymi. Rozpatrzono różne aspekty rozwoju systemów, zwłaszcza zagadnienia transmisji multimedialnych i szybkich połączeń internetowych przy zastosowaniu szerokopasmowych metod dostępu, wspólnej pracy systemów GSO i NGSO i metod efektywnego zarządzania systemami satelitarnymi.Broadband satellite systems are an integral part of communications technology, providing wide range of services. Their importance mainly results from the rapid growth of Internet, PC and interactive services usage. The article provides a review of technologies employed in geostationary (GSO) and non-geostationary (NGSO) satellite networks for provision of broadband services to fixed and portable ground terminals. Different aspects of development of these systems are considered, especially: transmission of multimedia content and fast Internet services using broadband access, sharing between GSO and NGSO satellite networks and effective management of satellite systems