Use Of Radiofrequency Research Articles

Coaxial Radio Frequency (RF) Diathermy in Anterior Segment Surgery

Modern ophthalmic microsurgery, particularly cataract extraction, trabeculectomy, and other forms of glaucoma filtration surgery, has been characterized by ever increasing precision. The use of radio frequency (RF) currents for cautery of blood vessels in anterior segment microsurgery has several advantages over other methods widely employed, including the bipolar cautery. A coaxial monopolar underwater diathermy probe, which operates with RF current has been specifically developed for anterior segment microsurgery and has proved vastly superior in cataract surgery, trabeculectomy, and full thickness glaucoma filtration procedures.

TEXTURIZATION THROUGH SPINNING

ABSTRACTPrinciples of spinning edible protein fibers are discussed and the commercial development of the process is traced. Basic considerations involve structure requirements for a polymer to be fiber‐forming and the control of processing steps. Physical phenomena occurring during the spinning process are enumerated as well as structural changes, the exhibited physical properties and principle process variables. Recent modifications of the spinning process include melt‐spinning and the use of radio frequency or microwave heating for bringing the spinning solution up to the optimum forming temperature.

The use of dielectric heating in the drying of biological materials from the frozen state

The rate of vacuum drying of biological materials from the frozen state may be extremely slow due to the lowering of the vapor pressure which results from evaporative cooling. Present means of supplying heat involve the danger of localized damage due to overheating at the surface. This can be avoided by the use of radio frequency (1000 Mc/s) energy from a radar generator. These wavelengths are not absorbed by dry proteins and thus the dielectric heating occurs only in that part of the material still containing water. Microscopic examination of tissues dried in this way revealed no evidence of localized overheating or other changes due to exposure to radio energy. In operation, a small antenna is placed next to the sample holder and the temperature, as indicated by a thermocouple in the material, is controlled by adjusting the power to the radar generator. The amount of power needed to produce a given amount of heating is a function of the rate at which water vapor can escape from the material as well as the dielectric properties of the material itself. When all water has been removed, no further heating can be produced.

An All-Electronic Signal-Seeking Broadcast Receiver

This paper describes the use of current-controlled inductors in a signal-seeking broadcast receiver. The use of these inductors as tuning elements results in a receiver with no moving parts. Although the idea of an automatically self-tuning receiver goes back several decades, its practical realization has been made more promising through the recent improvement in saturable-core circuit elements for radio frequency use. The receiver described does not represent a finished design for manufacture, but does show some presently obtainable characteristics in this type of instrument and the problems encountered in such circuits.

Recent Developments in the Electron Microscope

A description is given of the limitations in resolving power of microscopes indicating the reason for the 50- to 100-times greater resolving power of the electron microscope over the optical instrument. This is followed by a treatment of the basic principles involved in the electron microscope. A detailed description is given of the newly developed RCA electron microscope which, although equal or superior in performance to any previous microscope, occupies a much smaller space, is completely self-contained, and can be readily handled by an inexperienced operator. Examples of the work done by this new instrument are shown. The extremely compact power-supply system for the microscope is described. The reduction in size is obtained chiefly by the use of a radio-frequency-actuated rectifier system. By the use of radio frequency and an especially designed voltage divider, excellent stability of the order of 0.004 per cent of 60 kilovolts output at 0.5 milliampere drain is obtained.