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.

Example input: 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.
Example output: Ventricular Fibrillation
Example 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.
Q: Abstract: The impact of occlusion and the role of the counter ion on the permeation of nickel ions through skin have been examined using excised human skin. A highly sensitive electrochemical method was used to quantify the amount of nickel permeating the skin. The investigations show that nickel ions are capable of permeating the skin barrier when applied under occlusion. The process is slow, having a lag time of approximately 50 h. The permeation rate, and thus the physical amount being bioavailable, is considerably increased when aqueous nickel chloride is used in comparison with aqueous nickel sulphate. With respect to nickel permeation of the skin, we conclude that the choice of salt is an important consideration in patch testing.
A:
Female