Two mathematicians have proved that a straightforward question—how hard is it to untie a knot?—has a complicated answer.

Here is a close look at the common- versus differential-mode voltage and instrumentation amplifier (IA) topologies.

They are two LAUSD schools just a mile apart. Yet in many ways Canfield Avenue Elementary School and Shenandoah Elementary School in the Beverlywood and Reynier Village neighborhoods of Los Angeles ...