There has been continuing effort to understand the cause for the thickness dependence observed in the glass transition dynamics of polymer films. In a previous experiment, we showed that a two-layer model, assuming the films to contain a high-mobility surface layer residing on top of a bulklike inner layer, can explain the thickness dependence found in the viscosity of unentangled polystyrene films. Here, we examine the validity of this model in polystyrene films that are entangled. Unlike the unentangled films, the entangled ones are initially out-of-equilibrium, exhibiting a plateau modulus ∼1/10 times the bulk value. Upon annealing, the viscosity typically grows with time and eventually saturates. For the films with thickness above 20 nm, the saturated viscosity is the same as the bulk and takes ∼5–10 reptation times to reach. We find that the saturated viscosity is fully explainable by the two-layer model. A straightforward interpretation would imply that the surface mobile layer exists at equilibrium and modifies the dynamics of unentangled and entangled polymer films in a similar way.

Ultra-high energy neutrinos are detectable through impulsive radio signals generated through interactions in dense media, such as ice. Subsurface in-ice radio arrays are a promising way to advance the observation and measurement of astrophysical high-energy neutrinos with energies above those discovered by the IceCube detector (≥ 1 PeV) as well as cosmogenic neutrinos created in the GZK process (≥ 100 PeV). Here we describe the NuPhase detector, which is a compact receiving array of low-gain antennas deployed 185 m deep in glacial ice near the South Pole. Signals from the antennas are digitized and coherently summed into multiple beams to form a low-threshold interferometric phased array trigger for radio impulses. The NuPhase detector was installed at an Askaryan Radio Array (ARA) station during the 2017/18 Austral summer season. In situ measurements with an impulsive, point-source calibration instrument show a 50% trigger efficiency on impulses with voltage signal-to-noise ratios (SNR) of ≤2.0, a factor of ∼1.8 improvement in SNR over the standard ARA combinatoric trigger. Hardware-level simulations, validated with in situ measurements, predict a trigger threshold of an SNR as low as 1.6 for neutrino interactions that are in the far field of the array. With the already-achieved NuPhase trigger performance included in ARASim, a detector simulation for the ARA experiment, we find the trigger-level effective detector volume is increased by a factor of 1.8 at neutrino energies between 10 and 100 PeV compared to the currently used ARA combinatoric trigger. We also discuss an achievable near term path toward lowering the trigger threshold further to an SNR of 1.0, which would increase the effective single-station volume by more than a factor of 3 in the same range of neutrino energies. * Corresponding Author

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Originating from the early 1970s in Luleå, Sweden, and initially designed for the agricultural industry, hot-stamped sheet steel has developed to become the leading material in a modern state-of-the-art lightweight structural automotive body engineering. This critical review provides a detailed insight into the origins, fundamental metallurgical principles, commercial growth, current legal stronghold on aluminising coatings and latest technological developments. Comparisons to other state-of–the-art ferrous and non-ferrous automotive sheet materials are made, including carbon fibre-reinforced polymer; while the future outlook for hot-stamped sheet steel and opportunities for further technological developments are highlighted.