A starting material for producing optical fibers contains metal halides. Right and left rear wheels independently driven by permanent magnet electric motors and front wheels electrically steerable over a range of approximately 180 degrees operate under the control of a vehicle controller responsive to steering and speed input controls to provide zero turn radius operation with minimum slippage and tire scuffing. When the concentration is greater than a predetermined value, it is discriminated that no liquid is present, since it is considered that the output of the sensor is abnormal because of the absence of a liquid in the tank. The basic elements of the binding domain on gp120 that is recognized by broadly neutralizing antibody b12 are disclosed, as in their use in making vaccines for preventing or treating HIV. An analysis may determine attributes of each user and then allocate the user to a software version based on at least some of the determined attributes.