Abstract: An apparatus for intermittently controlling windshield wipers, comprising a setting switch which is capable of being manually activated, a microconller responsive to the activation of the setting switch, means for programming a time interval into the microcontroller in response to activation of said setting switch, whereby the microcontroller initiates a sweeping action of the windshield wipers corresponding to the time interval between activations of the setting switch and continues to initiate a sweeping action of the windshield wipers during the programmed time interval until a subsequent activation of the setting switch, and, either means for decreasing the time interval after setting of the programmed time interval by a single subsequent activation of the setting switch or means for increasing the time interval after setting of the programmed time interval by two subsequent activations of the setting switch. A method for intermittently controlling windshield wipers is also disclosed.

Abstract: Methods and compositions for determining the amount of chemical cross talk r isotopic scrambling, induced by an analytical procedure on a test sample using a reference standard composition containing a predetermined ratio of isotopes is disclosed. The method includes subjecting a reference sample which comprises a predetermined ratio of labeled isotopes to an analytical procedure; determining the degree of isotopic scrambling in the reference sample, subjecting a test sample to the identical analytical procedure; the degree of isotopic scrambling caused by the analytical procedure to the reference sample provides an indication of the presence of chemical cross-talk caused by the analytical procedure on the test sample. In preferred aspects, the cross talk is determined using mass spectral analysis and the reference sample comprises an algae mixture having a predetermined ratio of carbon-12 to carbon-13 isotopes.