James F. Schooley

Effect of stress on the superconducting transition temperature of SrTiO3

The superconducting transition temperatures of several specimens of reduced SrTiO3 and of Nb-doped SrTiO3 have been investigated as functions of hydrostatic and uniaxial compressive stresses up to 1.8 kbars. Decreases inTc as large as 0.12 K have been observed in specimens under hydrostatic pressure. Because of the lowTc and small compressibility of SrTiO3, Δ(lnTc)/ΔP and Δ(lnTc)/Δ(lnV) are orders of magnitude greater than the corresponding effects in elemental superconductors. The effect of uniaxial stress onTc varied with the direction of stress. Compression along a [111] direction caused large decreases inTc, while both small increases and small decreases inTc have been observed for [100] compression. It is believed that the present results reveal the presence of a sensitive volume dependence in one or more of the parameters important to superconductivity in SrTiO3, and that no significant electron-transfer effects occurred in the range of stresses of this experiment.

Superconductive transition in cadmium

Mutual inductance measurements of the superconductive transitions occurring in single-crystal and polycrystalline cadmium samples in magnetic fields of 0–10−4T (0–1G) are presented. The temperature at which the zero-field superconductive transition midpoints occur appears to be constant within ±0.2 mK for transitions narrower than 2 mK, butTc increases for broader transitions. The transitions exhibited both narrowing and hysteresis, the latter perhaps due to supercooling, in fields of a few tenths of a gauss.Tc has been measured as 0.515±0.0025 K on theT62 temperature scale.

First in a series: the early years of the national bureau of standards: born to measure

In this first of 4 articles about the early history of the National Bureau of Standards (NBS), which in 1988 became the National Institute of Standards and Technology (NIST), I present an overview of the state of standards in America during the first decades of the countrys existence, some of the origins of the scientific approach to metrology, and the growth of the NBS through the contributions of some of the outstanding people who participated in metrology.

Second in a Series: The Creation of the National Bureau of Standards

This article is the second in a series of four that describe the early years of the National Bureau of Standards (now known as the National Institute of Standards and Technology). The fi rst article described the work of Ferdinand Rudolph Hassler, America¿s fi rst metrologist [1]. His efforts during the fi rst half of the 19th century created the fi rst survey of the coastal United States and provided the young country with the beginnings of a coherent system of weights and measures. A brief description of the convention of the meter, a brief look at 19th century science and invention in America, and an account of the creation of the National Bureau of Standards appear in this article.

Third in a series on the first years of the national bureau of standards: stratton builds a laboratory

This article is the third in a series of four that describes the establishment of the National Bureau of Standards (NBS), now known as the National Institute of Standards and Technology (NIST). The first article featured the work of Ferdinand Rudolph Hassler, Americas first metrologist, who initiated the nations first coastal survey and a coherent system of weights and measures. The second article discussed the Convention of the Meter and the creation of the National Bureau of Standards by Public Law 56-177 on 3 March 1901. In this article, we follow the remarkable success of Samuel Stratton in building an effective and far-reaching standards laboratory. This article follows the outstanding personnel at the NBS and their work from 1901-1904, including the immediate and effective NBS response to the great Baltimore fire of 1904.

Use of Superconductors as Thermometric Fixed Points

The possibility of using superconductors with sharp transition temperatures as fixed points on a thermometer scale was examined. Annealed polycrystalline specimens 3.2 cm long by 0.157 cm in diameter were placed in a cryostat which would operate from 0.3 to 10.0 K; the superconductive transitions were measured with a Hartshorn bridge operating at 270 Hz. One specimen each was made from the purest available Pb, In, Ga, Zn, and Cd—the latter two elements are obtainable from the Office of Standard Reference Materials. In all cases but Cd, the width of the transitions were less than 0.001 K; for Cd it was 0.002 K. The specimens were cycled once to room temperature and remeasured to check their reproducibility vs two germanium resistance thermometers. The reproducibility was better than 0.001 K. These preliminary results indicate the strong possibilities for this approach to fixed point thermometry.

This is IEEE Energy: Energy studies at NIST

I decided to devote this column to the more general topic of energy studies at the National Bureau of Standards (NBS)/ National Institute of Standards and Technology (NIST). It turns out that there have been lots of these. What follows here is an overview of the history of the NBS/ NIST as it applies to the contributions from its energy studies and applications.

Egad! It's a mole!

A little while ago, I asked my wife of some sixty years whether she knows what a mole is. Despite more than a half-century of silly questions from me, she was not in the least annoyed, and she gave a perfectly logical answer.

Mingling with the masses [History of Physical Standards]

Would it be okay if I refer to mass as a weighty subject? And if I should do such a thing, would it give me gravitas? Well, weight and gravitas are much in the news these days, although weight seems to show up mainly in health stories and gravitas dominates the political scene. So let me be perfectly clear. Today, I want to discuss mass, weight, and gravity (the English equivalent of the Latin ¿gravitas¿).

Making new history from old standards

The winds of change are blowing strongly in the International System of Units (known since 1960 as the SI). Already gone is the meter bar, artfully constructed of a platinum-iridium alloy so many years ago, an end-on X-shaped bar carefully scribed by the denizens of the International Bureau of Weights and Measures (BIPM) in Sevres, France.