Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.
One example: Abstract: Some patients converted from ventricular fibrillation to organized rhythms by defibrillation - trained ambulance technicians(EMT - Ds) will refibrillate before hospital arrival.The authors analyzed 271 cases of ventricular fibrillation managed by EMT - Ds working without paramedic back - up.Of 111 patients initially converted to organized rhythms, 19(17 % ) refibrillated, 11(58 % ) of whom were reconverted to perfusing rhythms, including nine of 11(82 % ) who had spontaneous pulses prior to refibrillation.Among patients initially converted to organized rhythms, hospital admission rates were lower for patients who refibrillated than for patients who did not(53 % versus 76 % , P = NS), although discharge rates were virtually identical(37 % and 35 % , respectively).Scene - to - hospital transport times were not predictively associated with either the frequency of refibrillation or patient outcome.Defibrillation - trained EMTs can effectively manage refibrillation with additional shocks and are not at a significant disadvantage when paramedic back - up is not available.
Solution is here: Ventricular Fibrillation
Explanation: This term is directly present in the abstract and it is one of the main topic in it. So can be chosen as the medical subject heading.

Now, solve this: Abstract: The author reviewed artificial cells and their applications in hemoperfusion for chronic renal failure, poisoning, fulminant hepatic failure, removal of aluminium and iron, and metabolic assists. Other areas reviewed included artificial cells containing enzymes, multienzymes, immunosorbents, cell cultures and other areas. Artificial cells can be formed as membrane coated adsorbent or microencapsulated adsorbent, enzymes and cells. The large surface to volume relationship and the ultrathin membrane of artificial cells allows the rapid equilibration of metabolites. Artificial cells containing enzymes, ion exchange resin and activated charcoal have been used for hemoperfusion. The microencapsulated or membrane coated absorbents, enzymes, cells, immunosorbents and other material are prevented from releasing unwanted material into the circulation and prevented from adverse effects on blood cells. Because of the problem of charcoal in releasing emboli and depleting platelets we first developed coated activated charcoal hemoperfusion for clinical application. This has been used extensively in clinical studies. The artificial cell approach has also been applied to a number of other hemoperfusion approaches. The lack of space only allows this paper to summarize some of the approaches originated from this research centre.
Solution:
Aluminum