Experiments on the spherical expansion of a plasma into an underdense plasma are described. The initial spherical plasmas are stable anode spots that expand into the ambient region. The anode spots are formed in low pressure noble gas plasmas that have been impregnated with acetone. The formation mechanism is interpreted in terms of electron attachment on the acetone molecules.

Experiments on the propagation of an ion-acoustic soliton from an isotropic plasma into a region containing a weak mirror magnetic field are described. An anomalous focusing of the soliton is detected. The magnetic field also allows us to separately observe reflected ions from the soliton and the ions involved in the excitation of the soliton.

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A technique to easily and quickly obtain, display, and analyze the transistor characteristics of pnp and npn bipolar junction transistors with a Macintosh personal computer is reported. Both the necessary hardware and software are described.

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