Symbolic framework for linear active circuits based on port equivalence using limit variables

Published versio

MgB2 tunnel junctions and 19 K low-noise dc superconducting quantum interference devices

Point contact junctions made from two pieces of MgB2 can be adjusted to exhibit either superconductor-insulator-superconductor (SIS) or superconductor-normal metal-superconductor (SNS) current-voltage characteristics. The SIS characteristics are in good agreement with the standard tunneling model for s-wave superconductors, and yield an energy gap of (2.02 +/- 0.08) meV. The SNS characteristics are in good agreement with the predictions of the resistively-shunted junction model. DC Superconducting QUantum Interference Devices made from two SNS junctions yield magnetic field noise as low as 35 fT/Hz^{1/2} at 19 K.Comment: 4 pages, 4 figure

Seasonal changes in pore water pressure in a grass covered cut slope in London clay

In temperate European climates, the season of peak water demand by vegetation (summer) is out of phase with the season of greatest rainfall (winter). This results in seasonal fluctuations in soil water content and, in clay soils, associated problems of shrinking and swelling that can in turn contribute to strain-softening and progressive slope failure. This paper presents field measurements of seasonal moisture content and pore water pressure changes within the surface drying zone of a cut slope in the London Clay at Newbury, Berkshire, UK. A climate station was installed at the site to measure the parameters needed to determine specific plant evapotranspiration. This information was used to carry out a water balance calculation to estimate the year-round soil moisture deficit caused by the vegetation. The calculated soil moisture deficit matches reasonably closely the field measurements of soil drying. The field measurements of seasonal changes in pore water pressure and suction are linked quantitatively to the measured changes in water content using the soil water characteristic curve for the London Clay. The suctions generated by the light vegetation cover at Newbury were found not to persist into the winter and early spring

Observations of red-giant variable stars by Aboriginal Australians

Aboriginal Australians carefully observe the properties and positions of stars, including both overt and subtle changes in their brightness, for subsistence and social application. These observations are encoded in oral tradition. I examine two Aboriginal oral traditions from South Australia that describe the periodic changing brightness in three pulsating, red-giant variable stars: Betelgeuse (Alpha Orionis), Aldebaran (Alpha Tauri), and Antares (Alpha Scorpii). The Australian Aboriginal accounts stand as the only known descriptions of pulsating variable stars in any Indigenous oral tradition in the world. Researchers examining these oral traditions over the last century, including anthropologists and astronomers, missed the description of these stars as being variable in nature as the ethnographic record contained several misidentifications of stars and celestial objects. Arguably, ethnographers working on Indigenous Knowledge Systems should have academic training in both the natural and social sciences.Comment: The Australian Journal of Anthropology (2018

Connecting the Old to the New: What Technology-Crazed Adolescents tell us about Teaching Content Area Literacy

This article describes a study where Personal Digital Assistants (PDAs) were integrated into two eighth grade social studies classrooms to create a bridge that connected traditional textbook teaching with new technology. This article will explore the motivation for this type of integration, give specific details about the study, and share what we learned from students about how using the technology gave them control over their reading, connected to their lives, and gave a new spin on the old in terms of content area literacy strategies. Finally, this article will conclude with future directions for educational implications for research and practice

Wrinkling of a bilayer membrane

The buckling of elastic bodies is a common phenomenon in the mechanics of solids. Wrinkling of membranes can often be interpreted as buckling under constraints that prohibit large amplitude deformation. We present a combination of analytic calculations, experiments, and simulations to understand wrinkling patterns generated in a bilayer membrane. The model membrane is composed of a flexible spherical shell that is under tension and that is circumscribed by a stiff, essentially incompressible strip with bending modulus B. When the tension is reduced sufficiently to a value \sigma, the strip forms wrinkles with a uniform wavelength found theoretically and experimentally to be \lambda = 2\pi(B/\sigma)^{1/3}. Defects in this pattern appear for rapid changes in tension. Comparison between experiment and simulation further shows that, with larger reduction of tension, a second generation of wrinkles with longer wavelength appears only when B is sufficiently small.Comment: 9 pages, 5 color figure

Interchain coherence of coupled Luttinger liquids at all orders in perturbation theory

We analyze the problem of Luttinger liquids coupled via a single-particle hopping \tp and introduce a systematic diagrammatic expansion in powers of \tp. An analysis of the scaling of the diagrams at each order allows us to determine the power-law behavior versus \tp of the interchain hopping and of the Fermi surface warp. In particular, for strong interactions, we find that the exponents are dominated by higher-order diagrams producing an enhanced coherence and a failure of linear-response theory. Our results are valid at any finite order in \tp for the self-energy.Comment: 4 pages, 3 ps figures. Accepted for publication in Phys. Rev. Let