Discusses human ability to perceive repeated sensory stimuli in the visual system, and explains that its frequency fc has a critical value, under normal conditions, about 40 Hz. (GA)

Describes an undergraduate physical chemistry experiment which demonstrates the principles of solution calorimetry and the entropy titration technique. (CS)

Presents three problems that can be used in classroom to motivate chemical engineering students at the college level. (HM)

Accidentally killed animals provide biology classes with excellent study material. (Editor)

Describes a two-hour physics laboratory experiment modeling the phenomena of eclipsing binary stars developed by the Air Force Academy as part of a week-long laboratory-oriented experience for visiting high school students. (BT)

Describes a simple demonstration that illustrates the nature of isotropic substances by tearing newsprint, magazines, and wrapping paper. (BT)

This article describes the distribution of mass in a hand-held object as a fundamental but unrecognized contributor to the sensation one receives from the object. Experiments producing fractions for human sensitivity are given. (SA)

Discusses electric and magnetic forces between parallel-wire conductors and derives, in a simple fashion, order of magnitude estimates of the ratio of the likely electrostatic and electromagnetic forces for a simple parallel-wire balance. (Author/HM)

Describes a nineteenth century paper by Reynolds on his experiments with the tension that a column of liquid could sustain, and compares Reynolds work with some of the other related work published in French journals at that time. (GA)

Discusses different approaches to the teaching of electrical resistance as presented by different authors of physics textbooks. Evaluates, compares, and expresses personal preferences for certain approaches. (GA)

Explains interference colors in thin films as being due to the removal, or considerable reduction, of a certain color by destructive inteference that results in the complementary color being seen. (GA)

An experiment is presented which utilizes the current solid state technology to demonstrate electrochemical generation of hydrogen gas, direct generation of electricity for pumping water, and energy conversion efficiency. The experimental module costs about $100 and can be used repeatedly. (BB)

The preparation of eight heterocyclic compounds is described. These syntheses each take three or four hours and are suitable for undergraduate organic chemistry laboratories. (BB)

This undergraduate experiment demonstrates the effect of temperature on the rate of hydrolysis of para-nitrophenyl beta-glucoside. (BB)

An experiment is described which provides a simple example of the application of the Wittig reaction to the synthesis of unsaturated compounds. The experiment was designed with British HNC chemistry students in mind, but it is also suitable as a project-type exercise for final year GCE A-level students. (Author/BB)