Abstract: Provided herein are computer-implemented methods for assigning maternal or fetal origin to one or more genetic variants in cell free DNA (cfDNA) from a sample from a pregnant mammal, preferably a pregnant human, using a probabilistic model for assigning maternal or fetal origin to genetic variants in DNA from a sample obtained from a pregnant mammal, wherein the model assigns maternal or fetal origin based on a combination of fetal fraction and DNA fragment size.

Abstract: A clip for securing a rail seal element to a rail includes a generally L-shaped first clip member having a clamping arm and an elongate connector arm extending from one end of the clamping arm and capable of passing under the rail; a second clip member removably slidable on the connector arm; and a locking mechanism capable of releasably locking the second clip member against sliding movement along the connector arm. In use, the second clip member is removed from the connector arm so that the connector arm can be passed under the rail with minimum disruption of the ballast. The second clip member is then slid back onto the connector arm, and the assembled clip then oriented so that the rail and the rail seal are positioned between the damping arm and the second clip member. The second clip member is then slid on the connector arm toward the clamping arm so as to tightly press the rail and rail seal therebetween.