the degree of brain circulation and cellular functions). It showed that "the process of cell death is a gradual, stepwise process and that some of those processes can be either postponed, preserved or even reversed". A similar organ perfusion system under development, 'OrganEx', can restore – i.e. on the cellular level – multiple vital (pig) organs one hour after death (during which the body had prolonged warm ischaemia). It could be used to preserve donor organs but may also be developed to be useful for revival in medical emergencies by buying "more time for doctors to treat people whose bodies were starved of oxygen, such as those who died from drowning or heart attacks". There is research into what happens during and after death as well as how and to what extent patients could be revived by the use of science and technology. For example, one study showed that in the hours after humans die, "certain cells in the human brain are still active". However, it is thought that at least without any life-support-like systems, death is permanent and irreversible after several hours – not days – even in cases when revival was still possible shortly after death. A 2010 study notes that physicians are determining death "test only for the permanent cessation of circulation and respiration because they know that irreversible cessation follows rapidly and inevitably once circulation no longer will restore itself spontaneously and will not be restored medically". Development of advanced live support measures "including cardiopulmonary resuscitation (CPR) and positive pressure ventilation (PPV)" brought the interdependence of cessation of brain function and loss of respiration and circulation and "the traditional definition of death into question" and further developments upend more "definitions of mortality". Hypothetical speculations without existing technologies Russian cosmist Nikolai Fyodorovich Fyodorov advocated resurrection of the dead using scientific methods. Fedorov tried to plan specific actions for scientific research of the possibility of restoring life and making it infinite. His first project is connected with collecting and synthesizing decayed remains of dead based on "knowledge and control over all atoms and molecules of the world". The second method described by Fedorov is genetic-hereditary. The revival could be done successively in the ancestral line: sons and daughters restore their fathers and mothers, they in turn restore their parents and so on. This means restoring the ancestors using the hereditary information that they passed on to their children.