Embodiments include methods and apparatus for determining whether a neurological event has occurred in a subject. The controller generates a switching signal to switch a transformer for generating an output voltage and an output current at an output terminal of the offline LED lighting circuit to drive LEDs. The emission collection device has a conduit with an inlet in fluid communications with the low impedance cavity and an outlet that can be connected to a chemical sensing system to analyze the atmosphere sample for emissions leaking from the seal. The invention provides a method of manufacturing such ring magnets with high efficiency. , and the ethane is oxidatively dehydrogenated to form the corresponding alkene with an alkane conversion of at least about 10% and an alkene selectivity of at least about 70%.