These brief summaries are designed to help readers easily see which articles will be most valuable to them. The online version contains links to the articles.

Regular readers will note the temporary increase in the length of the journal as we try to decrease the backlog of manuscripts.

Beth Parks, Editor

88 (12) p. 1035

Giuseppe Zurlo, James Blackwell, Niall Colgan, Michel Destrade

88 (12) pp. 1036–1040

If a solid rubber cylinder is twisted, will it grow longer or shorter? This question was answered experimentally by John Poynting in 1909, but the analytical explanation is non-trivial. This manuscript provides a simple explanation using energy considerations, appropriate for an intermediate-level mechanics course.

Tom Howard and Ana Barbosa Aguiar

88 (12) pp. 1041–1048

Fluid instabilities are usually difficult to illustrate in labs and demonstrations. A simple classroom demonstration of a “barotropic instability,” supported by numerical analysis, is of particular interest to undergraduates in geophysics.

Lawrence N. Virgin

88 (12) pp. 1049–1058

3D printing is used to make a variety of cantilevers that allow undergraduates to probe the effect of cantilever geometry on stiffness and vibration frequency. This article is particularly useful for students of statics and strength of materials.

Andrea Ferroglia and Miguel C. N. Fiolhais

88 (12) pp. 1059–1067

The gravitational phenomenon of tidal locking is explored using the effective potential for two orbiting, spinning objects. The limiting case in which one of the objects is point-like is studied in detail, with Mars's moon Phobos given as an example. Appropriate for undergraduate or graduate classical mechanics courses.

Peter F. Hinrichsen

88 (12) pp. 1068–1074

For a pendulum undergoing large amplitude oscillations both with and without damping, the motion is represented using a many-term Fourier approximation and is compared with experimental results.

A. Chambliss and J. Franklin

88 (12) pp. 1075–1082

This manuscript introduces an improved method of computing the trajectories of charged particles in magnetic fields, including magnetic confinement geometries. The method could be easily incorporated into an undergraduate E&M or computational physics course.

S. Fumeron, B. Berche, and F. Moraes

88 (12) pp. 1083–1093

Differential forms are introduced to help illuminate certain features of electromagnetism. Two examples related to the electromagnetic properties of the classical and quantum vacuum illustrate the power of using differential forms. Appropriate for graduate-level students.

Adrian Nugraha Utama, Jianwei Lee, and Mathias Alexander Seidler

88 (12) pp. 1094–1102

A quantum cryptography workshop teaches high-school students about the conventional BB84 quantum key distribution protocol. In this hands-on session, a simplification is made to the original protocol, creating a security loophole that student hackers can exploit. Appropriate for motivated high-school or undergraduate students.

R. Cabrera-Trujillo and O. Vendrell

88 (12) pp. 1103–1108

The virial theorem is demonstrated for a particle in a box, using Cauchy's boundary conditions to account for the average force exerted by the walls on the particle. Appropriate for an undergraduate quantum mechanics class.

David C. Johnston

88 (12) pp. 1109–1122

The band structure of non-interacting electrons in a one-dimensional metallic structure with a periodic sinusoidal potential is studied, using numerically-exact solutions to the Mathieu-Schrodinger equation. Appropriate for an advanced class in solid state theory.

Jonathan Pinnell, Asher Klug, and Andrew Forbes

88 (12) pp. 1123–1131

Spatial filtering is a commonly-used technique to improve the quality of laser light by optically filtering the noise. Here a theoretical and experimental framework is developed to spatially filter “structured” light--i.e., light having an arbitrary beam profile. Appropriate for both undergraduate and graduate optics classes.

Kai Pieper, Gaël Latour, Jens Küchenmeister, Antje Bergmann, Roman Dengler, and Carsten Rockstuhl

88 (12) pp. 1132–1139

Optical coherence tomography (OCT) is a measurement technique for non-invasive imaging of interfaces in bulk samples. A simple OCT setup, built from a Michelson interferometer and a microscope, is described, which can be used for undergraduate lab projects.

A. K. T. Assis and M. C. D. Neves

88 (12) pp. 1140–1144

The paper translated is of interest as a reminder of the state of astronomy and physics at the end of the 19th century. It also provides an example, very appropriate for undergraduates, of the application of physics to astronomical questions.

Richard H. Price

88 (12) pp. 1145–1146

A new way to explain why a gyroscope doesn't fall: In a frame that rotates with the gyroscope, the gravitational torque is exactly balanced by the torque from the Coriolis pseudoforce. Appropriate for introductory mechanics students who understand acceleration in rotating frames.

Jacob Katriel

88 (12) pp. 1147–1150

An elementary example is given that shows the insufficiency of the energy spectrum to determine the interatomic potential, even when the bound states form a complete set. Appropriate for advanced undergraduates.

Jarrett L. Lancaster

88 (12) pp. 1151–1155

A resistance to motion in a harmonic oscillator is typically presented as either linear or quadratic in the velocity. Here a generalization is given for any power of the velocity. The presentation is best suited for advanced undergraduates.

Vikas K. Sewani, Hyma H. Vallabhapurapu, Yang Yang, Hannes R. Firgau, Chris Adambukulam, Brett C. Johnson, Jarryd J. Pla, and Arne Laucht

88 (12) pp. 1156–1169

The negative nitrogen vacancy center in diamond provides an opportunity for undergraduates to do hands-on experiments controlling electronic spin states in a low-cost laboratory setup.

E. Brekke, T. Bennett, H. Rook, and E.L. Hazlett

88 (12) pp. 1170–1174

3D printing enables the construction of an external-cavity laser diode at an order-of-magnitude cost reduction compared to a commercial system. This design enables new spectroscopy experiments in the undergraduate curriculum and will also be helpful in some research labs.

Harry Bernas

88 (12) p.1075