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We have developed an instrument which simultaneously measures the thermal conductivity κ, Seebeck coefficient α, and electrical resistivity ρ of a sample, thereby determining the thermoelectric figure of merit Z = α2/(κρ). A Quantum Design Physical Property Measurement System (PPMS) provides the temperature control from 1.9 - 390 K and applied magnetic fields of up to 14 tesla. Two small probes mounted along the sample each contain thin film Cernox chip thermometers as well as electrical contacts to monitor the temperature and voltage drops across the sample. A third probe attached to the end of the sample provides a heater and current source to stimulate the sample both thermally and electrically. The sample's response to cyclic heat pulses is analyzed in real time using DSP techniques. A nonlinear least-squares fit is used, employing a two time-constant model to determine both the thermal conductivity and the Seebeck coefficient for the material. Data acquisition using these ac techniques are expedited since we can sweep both temperature and field during a measurement. Adaptive algorithms continually adjust the thermal and electrical stimuli applied to the sample, optimizing the speed and accuracy of the measurement. We present results from some of the materials measured so far, including thermal conductivity standards and Pb in the superconducting state.

Bornstein’s hypothesis that there is a loss of color discrimination in tropical areas was not supported in earlier research in the Cook Islands. Using a more sensitive color vision test (the Farnsworth-Munsell 100-Hue Test), a loss of color discrimination in the red-purple and blue-green regions of the spectrum was found. The lack of sex differences in this color discrimination loss supports a physiological rather than a genetic explanation of the observed decrement.

The effects of qualitative labels on the judgment of gustatory dissimilarities were examined in the situation where the S was required to memorise the salient characteristics of one stimulus in a pair before judging its dissimilarity to the other. Systematic shifts in judgments occurred under various labelling conditions, suggesting that verbal cues play an important part in the perception of stimulus relations.

We have fabricated small‐area tunnel junctions of a lead‐tellurium‐lead structure. These have been used in conjunction with bulk superconductors to make hybrid quantum interference devices. We have successfully operated these devices at bias frequencies of 30 MHz, 300 MHz, and 10 GHz.

We describe the design, operation, and performance of a superconducting quantum interference device (SQUID) which operates at a frequency of 9 GHz. It is sensitive to variations of magnetic field in a frequency band from 0 to 1 GHz.

We have designed and tested a model for a 3 kHz receiver using a superconducting antenna circuit and a SQUID (Superconducting QUantum Interference Device) amplifier. Q factors as high as 6400 have been demonstrated for the resonant antenna, giving it an extremely low intrinsic noise voltage. We have anlayzed and solved various problems of matching between antenna and SQUID, as well as measuring noise, contributed by materials in the surrounding cryostat. We have been able to use feedback from the SQUID amplifier into the antenna to effectively broaden the 3 dB bandwidth to 1200 Hz without raising the noise level of the system significantly. By scaling the results obtained with our model receiver to an antenna volume of .022 M-cubed we have been able to estimate that a noise level of 2.4 x 10 to the -17th power T/(sq.rt. Hz) could be obtained in a 100 Hz bandwidth. (Author)

SQUID based instruments have been commercially manufactured in the United States for over six years. However, until about three years ago these systems were only suitable to be used by low temperature physicists and other researchers who were willing to become initiated into the somewhat black art of SQUID operation. The early instruments presented users with a choice between temperamental point-contact junctions and temperature sensitive thin-film bridges. It was often up to the user to piece his system together from various suppliers, and then have to worry about RFI (radio frequency interference), slew rate limitations, mysterious flux jumping, ground loops and a host of other distracting problems. There were no comprehensive research contracts let to industry for the systematic development of SQUID systems, so that out of necessity the development work was done in a piecemeal fashion. The terms “special” and “optional” have sometimes been used as euphemisms for “untried” when soliciting fixed-price contracts. These practices have resulted in some desperately heroic development feats. They have also, on occasion, left the customer with the task of salvaging a less than successful design.

Descriptions of the taste qualities of a nucleotide, disodium-5′-guanylate, are reported under two different response sets, lenient and stringent. Control comparison stimuli were de-ionized water and weak sodium chloride, and near threshold taste concentrations were used. Twenty subjects, 10 under each response set, participated. D5′G has a complex taste, and induces a marked false positive detection response pattern which resembles its own taste. The implications for methodology in gustatory psychophysics are noted.

The energy sensitivity of a direct current (dc) superconducting quantum interference device (SQUID) can be improved if it is operated in a two-stage configuration. Employing this technique, a commercial dc SQUID system was modified and made competitive with other sensors especially designed for very low noise applications. We report the noise measurements performed in the temperature range 4.2 K–25 mK. At 4.2 K, the coupled energy sensitivity obtained with the two-stage dc SQUID was approximately ten times better than with a conventional readout electronics. The noise energy decreases linearly until approximately 300 mK, in good agreement with theoretical previsions. At lower temperature the hot-electron effect produces a saturation and the best energy sensitivity measured with open input coil is 35 ℏ.

The quantization of magnetic flux in a superconducting circuit can serve for the measurement of electrical quantities in the same way that we use the wavelength of light to measure length. We report a demonstration of this function in the measurement of attenuation ratio at a frequency of 30 MHz.