You are a biochemist, working with a 12-slot centrifuge. This is a gadget that has 12 equally spaced slots around a central axis, in which you can place chemical samples you want separated. The slots on the centrifuge are numbered 1 through 12 clockwise (and clock-like).

           12  1
        11        2

      10            3
             °
       9            4

         8        5
            7  6

When the machine is turned on, the samples whirl around the central axis and do their thing. To ensure that the centrifuge runs smoothly, the samples must be distributed in the 12 slots such that it is balanced evenly.

Can you use the centrifuge to run 5 samples?

For example, if you have four samples, they may be placed in slots 1, 4, 7, and 10 to balance the centrifuge.

(In reply to re: Are biochemist really that smart?. by Tristan)

It usually takes even less time than that:

We are filling the tubes to a set volume so just use the pipette to fill the 'spare' tube to the same volume (ummm - about 2 seconds of time). Clearly, for repeated centrifugation of samples of the same volume then the dummy tube can remain in the centrifuge, taking no time at all.

 

We always have a beaker of water on the bench so do not have to even walk to the tap.

 

We are so cool ;)

 

(I have often wondered about the difference in density between the sample and the water dummy - although it may not cause a noticible imbalance (the centrifuge will usually turn off if this is the case) it may cause wear on the centrifuge.

 

Oh well - we can always buy another with all the $40/sample we get from ajosin ...

Posted by cyclothymic on 2008-07-20 08:15:18