Bipolar Pulse Trains Research Articles

Calcium activation of macrocilia in the ctenophoreBero�

1. Macrocilia on the lips of the ctenophore Beroë are usually quiescent, but can be activated to beat rapidly and continuously by various stimuli. 2. During feeding, macrocilia beat actively and serve to spread the lips of Beroë over its prey. 3. Vigorous, repetitive mechanical stimulation of the lips evokes widespread activation of macrocilia via a pathway that is probably neural. 4. Extracellular electrical stimulation (DC or bipolar pulse-trains) elicits immediate activation of macrocilia on lip pieces, but not on dissociated cells. 5. Macrocilia on lip pieces are activated to beat by high KCl artificial sea water (ASW), but not by high KCl Ca-free ASW. Continuous beating for long periods is also elicited by high Ca ASW or Mg-free ASW, but not by Ca-Mg-free ASW. Addition of La, Cd, Co or Mn (10 mM) to high KCl ASW reversibly blocks activation. Verapamil, D-600, nifedipine, or BAY K 8644 (10 microM) has no effect on KC1-induced activation, but the anticalmodulin drug W-7 (10 microM) reversibly inhibits beating. 6. Mild heat treatment dissociates macrociliary cells from lip tissue. Such isolated macrociliary cells usually beat continuously in normal sea water, and swim in circular paths. Ca-free ASW, or addition of Co or Mn to ASW, inhibits beating of dissociated cells. High KCl ASW activates beating of quiescent, isolated macrociliary cells. 7. Ca-Mg-free ASW inhibits beating of dissociated macrociliary cells, and return to Mg-free ASW activates motility, allowing one to activate macrocilia on isolated cells simply by addition of Ca.(ABSTRACT TRUNCATED AT 250 WORDS)

On Reducing the Period of Input Pulse Trains Using Coupled-Line Networks

The theoretical and experimental results on converting input pulse trains into bipolar pulse trains of higher speed are presented. The network used here for such functions consists of two strip-coupled lines and three resistors. The experiment shows good agreement with theory.

Stimuli producing different apparent frequencies for periodicity analysis and for place analysis

Segments derived from Gaussian noise served as exemplars of complex waveforms, and were repeated with alternate antiphasic (180° phase‐shifted) statements: [A+, A−, A+, . . .]. For repetition frequencies of (A+, A−) from 2–2000 Hz, listeners matched apparent frequencies using adjustable unipolar pulse trains: from 200–2000 Hz, apparent frequency = fundamental frequency = (1/τ Hz, where τ = duration (s) of [(A+) + (A−)]; from 2–30 Hz, apparent frequency = (2/τ Hz; from 30–200 Hz, apparent frequency was between (1/τ) and (2/τ) Hz. For 30–200 Hz, low‐pass filtering at (10/τ) Hz favored matches of (2/τ) Hz and high‐pass filtering at (10/τ) Hz favored matches of (2/τ) Hz. Results resemble earlier observations with bipolar (alternating polarity) pulse trains matched with unipolar pulse trains, then attributed to special characteristics of pulses. Our observations, together with other evidence, suggest rather that periodic waveforms consisting of antiphasic alternation produce different apparent frequencies for neural periodicity analysis and for neural place analysis, since: (1) periodicity analysis is insensitive to phase inversion [(A+) ≡ (A−)]; (2) place (spectral) analysis is sensitive to phase inversion [(A+) ≢ (A−)]. [Work supported by NSF.]

Radio Frequency Pulsewidth Modulation

The width of a train of square pulses can be varied to produce a modulated carrier at the pulse repetition frequency. When the pulse train is generated by switching (class D) transistors, highefficiency operation is possible. The efficiency of this type of amplifier can be significantly higher than that of conventional pulsewidth modulation amplifiers, since the switching rate is reduced. In addition, the spectrum of a bipolar pulse train so modulated has the highly desirable property of all spurious products being band limited near the odd harmonics of the carrier.

The T1 Carrier System

T1 carrier provides 24 voice channels by time division multiplexing and pulse code modulation (PCM). Each voice channel is sampled 8000 times a second and each sample is coded into a 7-digit binary word. Provision for signaling and synchronization raises the pulse repetition rate on the repeatered line to 1.544 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> pulse positions per second. The bipolar pulse train out of the terminals is transmitted over pulp, paper or plastic insulated paired cables by the use of regenerative repeaters. For 22-gauge cable pairs, repeaters are normally located at 6000-foot intervals. The system has been designed for low cost and is being widely applied on many trunks interconnecting switching units within metropolitan areas. Western Electric Company manufacture of T1 began in 1962 and about 100,000 channels are now in service throughout the Bell System.