Abstract: Methods of determining the presence or absence of fluorocarbon(s) on a substrate using X-ray Photoelectron Spectroscopy (XPS). A method may be used to determine the presence or absence of per- or polyfluoroalkyl substances PFASs. A method may use a porous polymer substrate. A method may use solid-phase extraction (SPE). A method may be used to determine the presence or absence of fluorocarbons in an aqueous sample. An aqueous sample may be a groundwater sample, wastewater sample, potable water sample, drinking water sample, or surface water sample. The limit of detection of fluorine in a method may be 0.05% F or less (for XPS analysis) and/or 20 ng or less on a substrate.

Abstract: A luminaire suspension mechanism is provided. The mechanism includes two arms, two friction elements, and a compression element. Each arm includes three segments and two connection points. For each arm, a first segment attaches to a second segment at a connection point, forming a first angle, while the second segment attaches to a third segment at another connection point, forming a second angle. Each friction element is connected to a respective arm's third segment. Each arm's first segment is compressably attached to the compression element, such that a force applied to at least one of the arm-friction element pairs results in the compression element and that at least one pair exerting a suspending force that suspends a luminaire to which the luminaire suspension mechanism is attached within a cavity. The compression element may be a torsion spring, and the angles formed by the arm segments may be obtuse.