Graduate Student Savanah Turner Publishes Study of over 300 L and T dwarfs

TrIP2 is an advanced version of the transformer interatomic potential (TrIP) trained on the expanded ANI-2x data set, including more diverse molecular configurations with sulfur, fluorine, and chlorine. It leverages the equivariant SE(3)-transformer architecture, incorporating physical biases and continuous atomic representations. TrIP was introduced as a highly promising transferable interatomic potential, which we show here to generalize to new atom types with no alterations to the underlying model design. Benchmarking on COMP6 energy and force calculations, structure minimization tasks, torsion drives, and applications to molecules with unexpected conformational energy minima demonstrates TrIP2’s high accuracy and transferability. Direct architectural comparisons demonstrate superior performance against ANI-2x, while holistic model evaluations─including training data and level-of-theory considerations─show comparative performance with state-of-the-art models like AIMNet2 and MACE-OFF23. Notably, TrIP2 achieves state-of-the-art force prediction performance on the COMP6 benchmarks and closely approaches DFT-optimized structures in torsion drives and geometry optimization tasks. Without requiring any architectural modifications, TrIP2 successfully capitalizes on additional training data to deliver enhanced generalizability and precision, establishing itself as a robust and scalable framework capable of accommodating future expansions or applications to new domains with minimal reengineering.

Pulsatile bioimpedance measurements require filters with very narrow bandwidths to preserve heartbeat-rate modulation while suppressing excess noise. At the signal's carrier frequency, this demands an impractically-high-Q filter. Multirate signal processing is an attractive solution to this problem, as it provides an avenue to extract the signals of interest practically. This paper presents a multirate filtering solution and shows step-by-step how the bioimpedance data of interest are extracted from noise and excitation frequency in in-phase and quadrature signals acquired from an analog measurement circuit. The tested impedance values resemble realistic human tissue impedance, demonstrating the method's ability to measure a human pulse within an approximately 50−Hz bandwidth at a 1−MHz carrier. This method is useful for high-Q bioimpedance measurements where interest lies in the details of signals pulsing at the rate of a beating human heart.

The Firefly Alpha launch, featuring an unexpected engine shutdown, offered a unique opportunity to study the acoustic effects of clustered nozzles on rocket noise. Measurements revealed a 0.75 dB drop in overall sound pressure levels (OASPL) and a 30% frequency shift, compared to predictions of 1.2 dB and 20%, respectively. While direct comparisons are limited by the dataset’s uniqueness, the results generally align with existing rocket noise models, highlighting areas for refinement. This study provides valuable data for improving noise prediction methods and deepening the understanding of launch vehicle acoustics.

The far-UV (FUV) reflectance of the state-of-the-art, broadband UV/optical/IR mirrors of XeF2-passivated LiF on Al (Al + XeLiF) is promising for future space telescope missions. To reach their potential, dependable cleaning procedures and storage methods for such reflective surfaces need to be developed. First Contact™ polymer (FCP) formulations have proven to be a reliable method for cleaning conventional mirror surfaces coated with oxides or bare metal and for protecting them in storage. We report here on studies of the cleaning and storage of Al + XeLiF samples using customized FCP formulations designed by Photonic Cleaning Technologies. Cleaning of such mirrors is demanding since fluoride coatings are softer than oxides and can be moisture sensitive. Any damage that marks the overcoat can lead to catastrophic loss of FUV reflectance due to surface roughening and formation of aluminum oxide, which is FUV opaque. We discovered that one formulation could be successfully applied to and removed from Al + XeLiF coatings multiple times. The coatings retained low roughness, minimal aluminum oxide thickness, and high far-UV reflectance. Another of the four FCP formulations successfully cleaned the Al + XeLiF coatings several times. Variable-angle, spectroscopic ellipsometry, tapping-mode atomic force microscopy, x-ray photoelectron spectroscopy, and FUV reflectance allowed us to observe any changes in reflectance and surface roughness, the formation of aluminum oxide, and damage to coating integrity. From the studies of the range of FCP-fluoride interactions, we noted that too much polymer-to-surface adhesion or exposure to trace water in the polymer can result in coating damage.

In this Sound Perspectives essay, I summarize potential impacts of rocket noise and suggest that the Acoustical Society of America (ASA), with its interdisciplinary expertise in acoustics and vibration, is uniquely positioned to help address these growing challenges. 

The search for new useful molecular ferroelectrics is a non-trivial problem. We present the application of an automated symmetry-searching method (FERROSCOPE) to the Cambridge Structural Database (CSD) in order to identify polar structures with a closely-related non-polar phase. Such structures have the possibility of undergoing a polarization-switching phase transition thus forming a ferroelectric-paraelectric pair. FERROSCOPE successfully identifies this relationship in 84% of a curated list of 156 known molecular ferroelectrics from the literature and identifies an additional 17 000 potentially ferroelectric compounds in the CSD. Our analysis shows that the method identifies CSD structures which have potentially been described in incorrect space groups, extending previous analyses. We describe experimental case studies which reveal phase transitions in two polar systems predicted to have related non-polar phases.