Eruption velocity is controlled by the gas contents of the column, and low-strength surface rocks commonly crack under the pressure of the eruption, forming a flared outgoing structure that pushes the gases even faster.These massive eruptive columns are the distinctive feature of a Plinian eruption, and reach up 2 to 45 km (1 to 28 mi) into the atmosphere. The densest part of the plume, directly above the volcano, is driven internally by gas expansion. As it reaches higher into the air the plume expands and becomes less dense, convection and thermal expansion of volcanic ash drive it even further up into the stratosphere. At the top of the plume, powerful prevailing winds drive the plume away from the volcano. These highly explosive eruptions are usually associated with volatile-rich dacitic to rhyolitic lavas, and occur most typically at stratovolcanoes. Eruptions can last anywhere from hours to days, with longer eruptions being associated with more felsic volcanoes. Although they are usually associated with felsic magma, Plinian eruptions can occur at basaltic volcanoes, if the magma chamber differentiates with upper portions rich in silicon dioxide, or if magma ascends rapidly.Plinian eruptions are similar to both Vulcanian and Strombolian eruptions, except that rather than creating discrete explosive events, Plinian eruptions form sustained eruptive columns.
Names
The IUPAC name for pentosan polysulfate is [(2R,3R,4S,5R)-2-hydroxy-5-[(2S,3R,4S,5R)-5-hydroxy-3,4-disulfooxyoxan-2-yl]oxy-3-sulfooxyoxan-4-yl] hydrogen sulfate.There are 40 synonyms listed for pentosan polysulfate on PubChem including BAY-946, HOE-946, pentosan sulfuric polyester, polypentose sulfate, polysulfated xylan, PZ-68, SP-54, xylan SP54 and xylan sulfate.Various brand names include Elmiron (as sodium salt), Hemoclar, Anarthron, Fibrase, Fibrocid, Thrombocid and SP54. PPS capsules are sold in India under the brand names Comfora, Pentossan-100, Cystopen and For-IC. In the veterinary field, pentosan polysulfate is sold as Cartrophen Vet and Sylvet by Biopharm Australia, Pentosan by Naturevet Australia, Anarthron by Randlab Australia and Zydax by Parnell. Research
Transmissible spongiform encephalopathies
PPS is being studied as a potential treatment of Creutzfeldt–Jakob disease (CJD). The rationale for this treatment was unclear but it was subsequently shown in prion-infected mouse neuroblastoma cells that PPS could rapidly reduce the levels of abnormal (scrapie) prion without affecting the normal cellular isoform. As PPS can bind to the cellular isoform of the prion protein, it may stabilise this form and prevent its conversion to the pathological (scrapie) isoform.The treatment of one patient in Northern Ireland and around six other patients in mainland Britain was reported in the press. Other animals
Dogs
Read et al. (1996)  used three different doses of sodium PPS to treat 40 geriatric dogs with well-established clinical signs of chronic osteoarthritis (OA) with a subcutaneous injection. The 3 mg/kg dose was the most effective.