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PDFtk (short for PDF Toolkit) is a toolkit for manipulating Portable Document Format (PDF) documents. [ 3 ] [ 4 ] It runs on Linux , Windows and macOS . [ 5 ] It comes in three versions: PDFtk Server ( open-source command-line tool ), PDFtk Free ( freeware ) and PDFtk Pro ( proprietary paid ). [ 2 ]
The PtK2 cell line was established by Kirsten Walen and Spencer Brown in 1962. [3] Cells from the rat kangaroo were selected as the source of a cell line because this species has only a small number of chromosomes and these chromosomes are easily visualized under a microscope; mitosis becomes easy to observe, and the structural aspects of cell division can be closely examined.