摘要:

An apparatus suitable for recordings of extracellular oxygen tension in terms of the degree of hemoglobin dissociation and intracellular oxidation‐reduction state in terms of the fluorescence level of mitochondrial and cytoplasmic reduced pyridine nucleotide has been constructed. A time sharing sequence permitting light and dark intervals for reflectance fluorometry and two flashes of different wavelengths for reflectance spectrophotometry operates at a repetition frequency of 60 cps. Fixed filters are used in fluorometry for excitation and emission and continuously variable interference filters are used in spectrophotometry.

ISSN:0034-6748    

DOI:10.1063/1.1718224

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Multiplier and log converter circuits in the literature which are based on junction diodes have in common the requirement that the junction employed have a constant slope of the logIvsVcharacteristic. When current components of the Cutler‐Bath and Sah‐Noyce‐Shockley types are considered, it is found that the range over which any one component becomes dominant, permitting application of the junction for logarithmic conversion, is narrow. The transfer conductanceyFBof silicon diffused transistors is shown to exhibit the desired logarithmic characteristic over many decades. The use of an operational amplifier to impose the required bias conditions is discussed, together with performance limitations imposed by the amplifier. Circuits are given illustrating the application of the technique to vacuum gauges, transistor testing, and to an analog multiplier having a dynamic output range of five decades. A commercial electrometer is converted to logarithmic indication by the addition of only two components.

ISSN:0034-6748    

DOI:10.1063/1.1718225

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A probe is described that will determine (a) contact resistance with continuously increasing pressure from 0–1000 g, (b) contact resistance as a function of wipe distance at fixed normal load, and (c) the current‐voltage properties of films from 0–200 V. In pressure and voltage modes, specimen positioning is entirely automatic and programmable. The probe locates the test surface on an X‐Y plane, goes through the selected mode, and then automatically repositions and repeats the measurement according to test schedule. The wipe mode is performed manually. Resistance, current, voltage, load, wipe distance, and location of the specimen are read out on an oscillographic recorder. Contact resistance is measured by the four‐point technique from 10−4to 103&OHgr;. The resistance span is divided into six ranges which change automatically, from high to low, when the resistance decreases to a preset percentage of the scale. The open circuit dc voltage of the resistance measuring circuit is 10−2or 5×10−2V, depending on resistance range.

ISSN:0034-6748    

DOI:10.1063/1.1718226

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

In a fixed‐field alternating gradient (FFAG) accelerator, the stability limits and the stability of the machine against field perturbations are very much affected by the choice of the betatron oscillation frequencies, &ngr;rand &ngr;z. A general criterion for the stability of the accelerator is proposed and, using this criterion, a computer study was carried out on the dependence of the stability on &ngr;rand &ngr;z. The results of this stability survey seem to indicate a a relatively unique choice of &ngr;rand &ngr;zto obtain the desired beam intensity.

ISSN:0034-6748    

DOI:10.1063/1.1718227

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A sensitive integrating microdensitometer for evaluation of diffraction films is reported. The instrument is simple in construction and requires no critical alignment. Contrary to general designs the scanning is done with the receiver by a Vidicon television pickup tube serving both as light sensitive element and scanning device. Circuits for processing the video signal are described.

ISSN:0034-6748    

DOI:10.1063/1.1718228

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Structural analyses of large solid propellant motors subjected to an environment of transportation and handling must include the contribution of the solid propellant. More accurate propellant mechanical properties are needed for this purpose than are presently being obtained. The test method described is for determination of the dynamic shear modulus in the frequency range 0.10 to 1000 cps. The specimen consists of two concentric metal rings carried by a flat plate of propellant. The high frequency data (70–1000 cps) are obtained by applying a known sinusoidal motion to the outer ring and measuring the response at the center. The transducer and center mounting are used as an inertial mass and are included in the analysis of the viscoelastic plate. The low frequency data (0.10–45 cps) are obtained by applying a known sinusoidal motion to the center of the specimen with the outer edge in a clamped position. The applied force and displacement are both measured at the center of the specimen. The theoretical response of a plate with the dimensions of the specimen is determined by using plate theory [J. H. Baltrukonis, W. G. Gottenberg, and R. H. Schreiner, Space Technology Lab. Tech. Rept. STL/TR‐60–0000–19331 (1960)] and assuming a complex Poisson's ratio of 0.5+i(o). An IBM computer is used to reduce the high frequency data; however, for the low frequency data an approximate solution [A. I. Soler and M. A. Brull, Repts. No. 61–012 and 61‐A‐014 under contract U‐60–11305, Dyna/Structures, Inc., Springfield, Pennsylvania (1961)] makes possible the reduction of results by a simple hand computation. Typical results for the complex dynamic shear modulus with its real and imaginary parts as well as the loss tangent are given for a composite solid propellant. These data indicate a precision of approximately ±10%.

ISSN:0034-6748    

DOI:10.1063/1.1718229

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The Dauphinee‐Mooser circuit has been improved by incorporating into it a transistorized null detector. The effective noise level has been cut down to, and possibly below, the chopper noise level by picking only the portion of signal that is observed while the contacts are closed. Pickup of external stray signals has been cut down to the level where they are virtually imperceptible. A complete description of the amplifier circuit is included.

ISSN:0034-6748    

DOI:10.1063/1.1718230

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A variable bent diffracting device is described which will fit on the Norelco diffractometer. The object of this device is to provide a coupling to the rotation of the diffracting element about the goniometer axis and to bend the element automatically so that its radius of curvature has a constant value over its surface and in particular the correct value at each diffraction angle. With such a device it has been demonstrated that it is possible to eliminate the major source of error in peak displacement and, in particular, improve the resolution of low angle lines.

ISSN:0034-6748    

DOI:10.1063/1.1718231

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A system is described for making low temperature electron bombardment studies. A liquid helium Dewar is used in conjunction with a 1.2‐MeV Dynamitron electron accelerator. Cooling is by conduction, and annealing is accomplished by balancing the helium flow rate through the cooling coils with a heater located within the cooling head. Details of the sample mount are given along with the beam positioning and monitoring devices.

ISSN:0034-6748    

DOI:10.1063/1.1718232

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A surface balance is described for production of dynamic changes of area of films adsorbed at a gas‐liquid interface. It has been used to demonstrate reduction of surface tension to nearly zero by surface active agents derived from mammalian lungs.

ISSN:0034-6748    

DOI:10.1063/1.1718233

出版商:AIP    

年代:1963

数据来源: AIP