摘要:

A new type electric micromanipulator for experimentation with living cells, or other objects under high magnification, is described. It consists of 4 electrically operated toolholders, each suspended under spring loading by thermal expansion wires. In turn, these are controlled by variable transformers operated by two joy sticks. Selector switches determine which toolholder will be influenced by either joy stick. Ratio control transformers in the 110‐volt, line‐operated power unit allow an operator precise, normalized, 3‐dimensional control of the microtools, viewed under any magnification of the compound microscope. In addition to joy‐stick control covering the microrange of 0.5 to 400 microns, each toolholder has 3 sets of mechanical controls to allow coarser adjustments for the range of 0.1 to 10 millimeters. Magnetic chucks and other conveniences for the observer have been provided.

ISSN:0034-6748    

DOI:10.1063/1.1770764

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A calorimetric method of determining photon flux is described. Absolute calibration was performed with an improved Pb block calorimeter using thermistors as temperature‐sensitive elements. Five‐minute irradiations were employed with a maximum of 33 milliwatts emerging from a 0.5‐in. collimator placed at 115 cm from the betatron target. A secondary standard was developed for the purpose of determining bremsstrahlung flux. This secondary standard was a 4‐in. diameter, parallel plate ionization chamber consisting of a 0.016‐in. Al center foil separated by 0.052‐in. air gaps from 0.25‐in. Cu front and back plates and adapted for use with a Victoreen M‐70 electrometer. With corrections described, the results, in ergs/esu per cm air (NTP), are 7340 at 300 Mev, 6370 at 250 Mev, 5720 at 200 Mev, and 5370 at 150 Mev. Calibration of Victoreen thimbles with various types of converter were also made.

ISSN:0034-6748    

DOI:10.1063/1.1770765

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A simple circuit for use in conjunction with electrometer tubes is described. This configuration provides for a reduction in the input capacitance of the circuit to a value in the order of 0.05 (Cgk+Cgp) of the electrometer tube. At the same time linearity is improved. These qualities are achieved through causing both the cathode and the plate potentials of the electrometer tube to follow its grid. No critical compensating adjustments are required. This circuit is particularly suitable as a preamplifier for electrophysiological measurements.

ISSN:0034-6748    

DOI:10.1063/1.1770766

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A design of stereoscopic cameras for use in investigating large angle scattering phenomena with a Wilson cloud chamber has been developed. Duplication of projection systems was adopted in order to enable the analysis of tracks to be shared between two teams working simultaneously. It was required that the reprojected images of the two pairs of cameras should be identical to within close limits, in addition to the usual requirements of a high order of accuracy of reprojection of each camera. Tests described in the paper showed that the reprojection was accurate to at least ±0.5 mm, which is within the allowed tolerances of the experiments envisaged. No observable differences were found between the reprojected images of the two pairs of cameras.

ISSN:0034-6748    

DOI:10.1063/1.1770767

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A simple mechanical network is described which, when loaded with a constant weight, maintains constant stress on the slip planes of a single crystal extending under creep. It also automatically rotates the grips to eliminate end distortion. The problem of extending the crystal along a fixed time is examined.

ISSN:0034-6748    

DOI:10.1063/1.1770768

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A high vacuum needle valve may be used as an adjustable leak for regulating the flow rate of gas samples to a mass spectrometer, when the valve is equipped with a wedge and lever system providing very sensitive control of the needle position. Flow through the leak is molecular at spectrometer pressures, but mass flow may be secured by inserting a capillary tube between the sample and the leak. The leak may be closed completely, thereby simplifying the design of the sample inlet system.

ISSN:0034-6748    

DOI:10.1063/1.1770769

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A new thin‐wall Geiger counter of large area sensitive to soft beta‐radiation has been developed. The sensitive area can be as large as desired and the wall thin enough for C14(2 mg/cm2). The cylindrical geometry renders the counter especially suitable for accurate assays of large solid samples of low specific activity and low energy.

ISSN:0034-6748    

DOI:10.1063/1.1770770

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

This paper describes a membrane apparatus which has been used successfully in obtaining analogic soap‐film solutions to boundary‐value field problems in which either the Poisson or the Laplace partial‐differential equation must be satisfied.

ISSN:0034-6748    

DOI:10.1063/1.1770771

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A fast scale of four has been developed in which the emphasis has been on reliability. Since the scale of two units employ diode clamping to limit the plate and grid voltage excursions, the most important requirements are (1) proper choice of grid clamping voltages, (2) the grid swing without grid clamping should be considerably larger than and symmetrical about that obtained with grid clamping. To satisfy these and other requirements, metallic film precision resistors are used extensively, and the critical bias voltages are controlled by compensating networks. The resolving time for 3 or more evenly spaced trigger pulses is about 0.06 microsecond. Pulse heights ranging from 6 to 15 volts may be used.

ISSN:0034-6748    

DOI:10.1063/1.1770772

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A new multiple filament surface ionization source has been developed for mass spectrometry which for several of the elements is many times more efficient than the usual single filament surface ionization source. Emission from the source can be shifted from the oxide to the metal position or vice versa by appropriate adjustment of temperatures. Because of the high efficiency of the source it is possible to look at the sample during a number of successive evaporations. Use of this source should eliminate the necessity of using electron multiplier ion detection for some elements.

ISSN:0034-6748    

DOI:10.1063/1.1770774

出版商:AIP    

年代:1953

数据来源: AIP