The present invention provides an active primer that includes an electronically active material dispersed in a binder. Each rack within such vending machine has an open end and closed end, wherein the open end thereof is provided with a mechanical stop or gate having essentially no mechanical moving parts, for control of the dispensing of products from such racks in response to customer demand for product from such rack. Another exemplary method includes synthesizing a first proofread double stranded DNA ; synthesizing a second proofread dsDNA; and ligating the first proofread DNA with the second proofread DNA to form a long polynucleotide. A transmission link is provided, coupled to the backrest and the seat part so that the backrest pivots into the not-in-use position as the seat part is moved into its not-in-use position.