Harold E. Edgerton

In-situ silhouette photography of Gulf Stream zooplankton

Abstract An in-situ silhouette camera system that permits assessment of vertical and horizontal zooplankton distributions on meter scales, yet retains considerable taxonomic information, is described. Representative data are presented from initial deployments in the Gulf Stream off Miami, Florida. Advantages and disadvantages of this approach are discussed.

AN ANALYSIS OF THE LOCOMOTION OF THE SEAHORSE, HIPPOCAMPUS, BY MEANS OF HIGH SPEED CINEMATOGRAPHY

INTRODUCTION. . . . . . . . . . . . . . S P E E D S OF FIN h I O V E M E K T S . . VECTOR A N A L Y S E S . . . . . . . . . . DISCUSSION. . . . . . . . . . . . . . . . S U M M A R Y . . . . . . . . . . . . . . . . . . BIBLIOGRAPHY. . . . . . . . . . . . . . EXPLANATION OF PLATES.. . . . . . . . . . . . . CONTENTS PAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

The Pulling into Step of a Salient-Pole Synchronous Motor

A synchronous motor started as an induction motor must pass through an electro-mechanical transient after the field circuit is supplied with electrical excitation in order to change its action from that of an induction motor to that of a synchronous motor. The calculation of this problem has been difficult because the differential equation of motion is of a non-linear type of which no analytical solution has been made. The integraph at the Massachusetts Institute of Technology has given a new and direct method of solving equations of the type encountered in these pulling-into-step transients. In this paper are compiled the results of many integraph solutions which were made after combining the factors that influence the performance of such machines into ratios and relative factors so that the results will apply to all practical cases. From the solutions several generalizations are made which can be directly applied to determine whether or not any type of salient-pole synchronous motor will synchronize properly. These solutions take into account inertia, saliency, incompleteness of amortisseur windings, load, switching angle, and field current, and assume negligible armature resistance, negligible rotor leakage reactance, no saturation, constant load torque near synchronous speed, and negligible electrical transients. Oscillograph tests of a 160-hp. motor and a sample calculation are given.

Photographic Use of Electrical Discharge Flashtubes

Xenon-filled gaseous discharge tubes flashed from energy stored in electrical capacitors are very useful converters of electrical energy into light, for both visual and photographic purposes. The efficiency for a typical tube is about 40 lumens per watt for rated conditions. Measured values of light output and efficiency as functions of energy input are given for the FT-14 flashtube. A method of measuring the integrated light output is described, as well as typical circuits and electrical conditions. The xenon electrical flashtube is particularly useful for color photography since its spectral distribution is similar to that of daylight and since the spectral distribution and efficiency are not appreciably affected by voltage or life. The quantity of light is predictable in terms of energy input from the storage capacitor. The flashtube is proposed as a standard lamp, especially for flash comparison. An approximate relationship useful for calculating the photographic exposure factor or guide factor (distance × aperture) is given in terms of energy in the condenser, the type of reflector used, and film speed.

Electrical Characteristics of Stroboscopic Flash Lamps

This paper describes the electrical characteristics of gas‐filled discharge tubes when flashed by a condenser discharge. The object of the experiments was to determine the effects of tube dimensions, pressure, voltage, and capacity upon the performance. The results are of an experimental nature and cover a limited range of values of tubes and circuit constants. An empirical constant called tube resistance is defined and evaluated. This constant is useful in predicting the performance of tubes in electrical circuits.

Time-lapse photography of the biological reworking of sediments in Hudson submarine canyon

ABSTRACT Time-lapse photography indicates that biological activity and reworking acted as a catalyst for sediment erosion by bottom currents during a two-day period at a depth of 360 meters in the Hudson submarine canyon. Decapod Crustacea were responsible for the major tracks and burrows. Deep, sharp tracks made by the crab Cancer borealis were smoothed by currents within three hours, but a large burrow was maintained with intermittent excavation by a smaller burrowing decapod crustacean. The asteroid (seastar) Henricia did not track but smoothed the bottom. A polychaete worm appeared to forage in the Cancer tracks. Bottom water turbidity varied abruptly at intervals of less than one hour.

A Direct‐Reading Counting Rate Meter for Random Pulses

Randomly distributed pulses, of any voltage shape, and of varying magnitude, actuate an amplifier whose output meter indicates only the average rate of arrival of the pulses. Counting rates of 30 per minute up to several thousand per minute are read directly from a rugged meter. The apparatus is a.c. operated, is portable, and is particularly adapted to the study of feeble gamma‐radiation. The apparatus consists essentially of a preamplifier, a uniform pulse generator based on a relaxation oscillator or on an inverter circuit, an output amplifier stage, and a capacity‐resistance electrical tank circuit for performing the averaging process.

Xenon Arc Transients, Electrical and Optical

The growth of the luminous area of a high current discharge in an electronic xenon‐filled flashtube has been studied by means of a sequence of timed short‐exposure photographs taken with a magneto‐optic shutter. Electrical measurements show that the tube conductance is approximately proportional to the luminous area of the arc channel. The ionized gas has a volume conductivity of about 90 mho/cm averaged over the luminous path during the buildup for the conditions investigated.

Transient Torque-Angle Characteristics of Synchronous Machines

Mechanical oscillations of synchronous motors following the application of abrupt shaft loads have not been hereto-fore easily calculated for cases of large angular swings, taking into account the damping currents in the rotor, except by tedious point-by-point methods. The chief difficulty has been due to the form of the basic differential equation upon which the solution of hunting problems depends. Within the lastfew years Dr. V. Bush and others at the Massachusetts Institute of Technology have devised the integraph which is capable of solving the equations of the synchronous motor. Into the integraph are put curves representing the non-linear differential equations and the boundary conditions. The desired results come from the integraph as curves. In this paper the problem of sudden load on the non-salient pole alternator is solved by the integraph for enough different conditions so that the performance of practically any machine of this type may be easily predicted from the compiled results. Knowing the moments of inertia of the machine and its load, the characteristics of the machine running as a synchronous motor and as an induction motor, the maximum amount of sudden load for which the machine will remain in synchronism may be determined for different values of initial load. Other curves give the maximum angle of the first swing of the rotor and the time interval for the rotor to change from its initial position to this maximum angle. The simplest type of equation representing an ideal synchronous machine is solved in this paper.

Blood Flow in the Microcirculation of the Conjunctival Vessels of Man

H. MARICQ, M.D., Fellow in the PostDoctoral Research Training Program, Department of Psychiatry, Columbia University, College of Physicians and Surgeons, New York, N. Y. and Research Associate, Essex County Overbrook Hospital, Cedar Grove, New Jersey Nailfold capillary bed, the area most frequently used for observation on human microcirculation has been reported to be remarkably constant in morphology over long periods of time. The total area of the nailfold examined by capillary microscopy and the focus of interest have varied somewhat from one study to another but have mainly been limited to the end row loops. In the present study the nailfold capillary bed was examined in 406 schizo-