If the ACA is repealed, with it will go the protection it offers individuals with preexisting health problems. They would again be denied health insurance or subjected to unaffordable insurance premiums.
The rapid transition from a non-conducting to a conductive state produces a brief emission of light and a sharp crack or snapping sound. A spark is created when the applied electric field exceeds the dielectric breakdown strength of the intervening medium.
Spark is built using Scala around the concept of Resilient Distributed Datasets (RDD) and provides actions / transformations on top of RDD. It has one of the best documentation around open source projects. There was not much resources around RDD, but this paper and presentation are the roots of RDD.