Describes an apparatus designed to investigate molecular motion by means of light scattering. Light from a He-Ne laser is focused into a cell containing a suspension of polystyrene spheres. The scattered light, collected on the photosurface of a photomultiplier tube, is analyzed. The apparatus won first prize in Demonstration Lecture Apparatus in…

The following report appears as the introduction to a privately funded educational history study recently completed by a group of American historians, educators, and legislators. (Editor)

The temperature at which the onset of coordinated segmental motion begins is called the glass-rubber transition temperature (Tg). Natural rubber at room temperature is a good example of a material above its Tg. Describes an experiment examining the response of a typical polymer to temperature variations above and below Tg. (Author/JN)

Overvoltage, also called overpotential, activation overpotential, and kinetic polarization, is the voltage in excess of the reversible value which is required to cause a cell reaction to proceed at an appreciable rate. Provided is a simple and dramatic demonstration of overvoltage. (JN)

Cerenkov counting is a useful technique for assaying medium/high energy beta emitters in aqueous solutions. Advantages of the technique include: (1) simple sample preparation; (2) being able to handle large volume of aqueous solution for counting; and (3) absence of chemical quenching. Cerenkov counting is also less expensive than other methods.…