摘要:

A high precision, easy to build, digital recording system has been adapted on a commerical Zimm‐Crothers rotating viscometer. It allows intrinsic viscosity measurements on very diluted nucleic acid solutions.

ISSN:0034-6748    

DOI:10.1063/1.1686115

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Equipment has been designed and developed that allows one to use the gamma attenuation technique to measure the densities of metals at high temperatures. Saturated liquid density values have been measured from room temperature up to 1841°C. The density values obtained by this technique compare very well with those measured by other methods.

ISSN:0034-6748    

DOI:10.1063/1.1686116

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A remote reversing switch is presented, which is operable at low temperatures and useful for eliminating thermal lead voltages by means of an average. It utilizes four n‐channel enhancement mode MOSFET's with the channels connected in a balanced bridge configuration. Input signal reversal is achieved by gating on alternate pairs of transistors. The use of sapphire heat sinks for all channel leads is critical to the achievement of a switch resolution of better than ±2 nV, measured at 4.2, 77, and 300 K. The switch was also used as a remote chopping element for a phase‐synchronized dc to ac inversion, again at 4.2, 77, and 300 K with resolution approaching the limits of the equipment used to test its performance. The small size, infinitesimal power dissipation, predicted immunity to large magnetic fields, and almost perfect isolation of the driving circuit from the desired signal makes this reversing switch superior to any other device which has previously been used for such purposes.

ISSN:0034-6748    

DOI:10.1063/1.1686117

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A simple infrared cell was developed to study gas adsorption on a catalyst. The main body of the cell was made of Pyrex glass. Windows were attached to the cell body by means of O‐ring seals with water‐cooled brass rings. A heating assembly with tungsten windings was set in the cell. This cell could be used at temperatures up to 450°C, either under vacuum to a pressure of 10−6Torr or in any controlled atmosphere.

ISSN:0034-6748    

DOI:10.1063/1.1686118

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The geometric factorGis a major parameter in determining differential cross sections with a gas target. Silverstein has calculatedGfor several detector aperture geometries with a finite sized, but parallel incident beam. Critchfield and Dodder have calculatedGfor a parallel‐edge front aperture and circular back aperture with a divergent incident beam. In this article,Gis calculated for a parallel edge front aperture and a rectangular back aperture with a divergent incident beam. The present calculation follows the method outlined by Critchfield and Dodder and employs a convenient combination and slight modification of their notation and that of Silverstein.

ISSN:0034-6748    

DOI:10.1063/1.1686119

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An inexpensive servo‐controlled electrohydraulic fatigue machine, capable of a maximum load of 22.2 kN (5000 lbf) and a maximum servo‐controlled strain rate of 0.2 sec−1, is described. Its primary capability is to perform load and strain‐range controlled fatigue tests conducted at constant strain rate feedback. In addition, the machine is capable of performing constant strain rate tensile tests and closed loop stress relaxation tests. The results of some initial fatigue tests are presented.

ISSN:0034-6748    

DOI:10.1063/1.1686120

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A description is given of a cantilever apparatus to determine the mechanical strength and elastic modulus of optical fibers. This test method overcomes the problem of fiber breakage in the jaws of tensile machines. Young's modulus, the breaking stress distribution, and values of the breaking radius of curvature and strain are presented for fused quartz fibers.

ISSN:0034-6748    

DOI:10.1063/1.1686121

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A simple Hall probe loop which can be adjusted to null induced voltages from ac magnetic fields is described. With its use induced voltages have been reduced to the microvolt region allowing Hall effect measurements without the use of bucking voltages in low mobility materials.

ISSN:0034-6748    

DOI:10.1063/1.1686122

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A novel and simple two frequency ac Hall apparatus is described and some results obtained using it are presented.

ISSN:0034-6748    

DOI:10.1063/1.1686123

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An arrangement is suggested which avoids the need for specialized, high‐priced, bulky switches in four‐terminal resistance circuitry.

ISSN:0034-6748    

DOI:10.1063/1.1686124

出版商:AIP    

年代:1973

数据来源: AIP