{ "items" : [
    { "id" : "http://dbpedia.org/resource/Holweck_pump"
      "properties" : {
        "http://www.w3.org/2000/01/rdf-schema#comment" : [ "A Holweck pump is a type of vacuum pump that utilises the drag of air molecules against a rotating surface. The modern turbomolecular pump is a more advanced version based on similar operation, and a Holweck pump is often used as the backing pump for it. The Holweck pump can produce a vacuum as low as 10−8 mmHg."] } } }
