Berliner Gramophone formulations remained the standard disc record material until the first vinyl records – initially made only for radio use and other special applications – were introduced in the 1930s. Beginning in 1896, Berliner's gramophones were made by Philadelphia-based machinist Eldridge Johnson, who added a spring motor to drive the previously hand-rotated turntable. Berliner also opened an office in New York City, staffed by Frank Seaman and O. D. LaDow and organized as the National Gramophone Company. Master recordings were made onto zinc plates, which were then electroplated and a negative-image "mother" made from them to stamp discs. A major reversal
Polymer fractionation Polymer fractionation Polymers are chainlike molecules that are made of the same repetition unit. With a few exceptions such as proteins, a polymer consists of a mix of molecules with different chain lengths. Therefore average values are given for the molecular weight like the number average, the weight average or the viscosity average molar mass. A measure for the width of the molecular weight distribution is the polydispersity index. The targeted manipulation of the molecular weight distribution of a polymer by removing short and/or long chain material is called polymer fractionation. The molecular weight of polymers has a large influence