Hafnium Bismuth Erbium Co-Doped Fiber Based Dark Pulses Generation With Black Phosphorus As Saturable Absorber

A dark pulse generation is demonstrated in a fiber laser configured with a 20 cm long HBEDF and multilayer Black Phosphorus as a gain medium and saturable absorber, respectively. Dark pulses fiber laser at 1.5 µm region was obtained when the pump power exceeds the threshold of 147 mW. Meanwhile, the spectrum of the dark pulse is centred at 1556.40 nm, with the 3 dB bandwidth of 0.12 nm and the separation between adjacent pulses is 1145 ns, corresponding to the cavity length of 211 m. The pulse width was measured to be around 320 ns. The radio-frequency spectrum of the dark pulse, which was measured within the 20 MHz range. More than 17 harmonics were observed within this range, which indicates the mode-locking operation of the laser. The fundamental frequency was obtained at 1.1 MHz, which agreed with the oscilloscope trace. Furthermore, it shows a signal to noise ratio of about 36.58 dB, which indicates good stability. The maximum output power of 0.78 mW and pulse energy of 0.78 nJ were obtained at 187 mW pump power.

Membrane potential simulation program for IBM-PC-compatible equipment for physiology and biology students.

MEMPOT is an interactive graphic simulation program, written in Turbo C for IBM-PC-compatible equipment and designed to teach students in the physiological and biological sciences about the measurement and ion dependence of cell membrane potentials. Different external salt solution values can be chosen and an intracellular electrode can be moved on the screen to impale one of a group of cells and measure resting or action potential responses. A simulated voltage-to-frequency audio signal emulates normal experimental audio monitoring of the electrode potential, and a window displays a simulated oscilloscope trace (together with "electrical noise") of the resting or action potential response. The average value of each set of successful impalements is determined for each solution. Once measurements have been made over a suitable range of different solutions, the data can be reentered and plotted graphically on the screen and an interactive approach can be used to determine relative sodium-to-potassium permeabilities at rest or at the action-potential peak. A randomization routine varies permeability ratios within a small range between runs.

Systems for Measuring Thickness of Temperate and Polar Ice from the Ground or from the Air

Equipment has been designed and tested for ground-based and airborne sounding of temperate glaciers. The transmitter is a free-running pulse generator that uses avalanche-mode transistor breakdown to create high-voltage pulses. The transmit and receive antennas are resistively loaded dipoles; for the airborne system, a twin-lead transmit element and a three-layer coaxial receive element are used on the inboard end of the respective antennas. The sounders are broadband systems; oscilloscopes are used for receivers. The oscilloscope trace is recorded photographically in the ground-based systems. A sampling oscilloscope is used in the airborne system—the sampling process strobes the waveform to audio frequencies so that it can be recorded on magnetic tape. Echoes have been obtained from ice depths of 550 m using the airborne system and about 1 000 m using the ground-based system.

Systems for Measuring Thickness of Temperate and Polar Ice from the Ground or from the Air

Equipment has been designed and tested for ground-based and airborne sounding of temperate glaciers. The transmitter is a free-running pulse generator that uses avalanche-mode transistor breakdown to create high-voltage pulses. The transmit and receive antennas are resistively loaded dipoles; for the airborne system, a twin-lead transmit element and a three-layer coaxial receive element are used on the inboard end of the respective antennas. The sounders are broadband systems; oscilloscopes are used for receivers. The oscilloscope trace is recorded photographically in the ground-based systems. A sampling oscilloscope is used in the airborne system—the sampling process strobes the waveform to audio frequencies so that it can be recorded on magnetic tape. Echoes have been obtained from ice depths of 550 m using the airborne system and about 1 000 m using the ground-based system.

A Computer-Based Electro-Optical System for Measuring Wave-Induced Sand Concentrations

A computer-based system utilizing an electro-optical instrument has been developed for generating and processing a signal proportional to the instantaneous sand concentration at a point in a flow field. Herein are described the instrumentation and techniques used in a study of sediment entrainment by periodic waves breaking on sand beaches. The instantaneous sediment concentration has been decomposed as follows: C(x,y,z,t)=C¯(x,y,z)+C′(x,y,z,t)+Cp(x,y,z,t) where C(x, y, z) is the temporal average concentration, C′(x, y, z, t) is a random component of the sediment concentration, and Cp(x, y, z, t) is a repetitive component with period equal to the period of the breaking waves. Particular attention has been given to isolating the repetitive component which was so obscured by the signal characteristics that no periodicity was apparent on either an oscilloscope trace or a strip chart recorder. Spectral analysis was not applicable because the shape of the repetitive waveform, Cp(x, y, z, t), over one wave cycle was desired.

A simple rate meter and oscilloscope intensity modulator for single cell recording

A simple circuit has been described which gives a meter reading proportional to the rate of cell firing. The circuit will trigger reliably on any signal exceeding 100 mV, and a trigger-level control is provided to enable triggering to be suppressed below a threshold level. An external recorder may be driven from the circuit. In addition the circuit provides a pulse which may be used to modulate the intensity of an oscilloscope trace each time the threshold is exceeded.