Total Solar Eclipse: April 8, 2024

Alloying mixed ratios of elements into the halide perovskite (HP) structure has proven to be an effective method of tuning these materials’ structural and electronic properties for photovoltaic and other optoelectronic applications. However, the standard spectroscopies used to characterize HP alloys such as absorption and photoluminescence are limited in their ability to detect disorder and phase segregation within the structure. Here, we characterize these properties in 2D HP alloys to a greater degree by using electroabsorption spectroscopy to study thin films with mixed-metal (Pb–Sn) and mixed-halide (Br–Cl and Br–I) compositions. The large spectral separation of band-edge states in 2D HPs allow us to detect a coexistence of elemental-rich domains within the Pb–Sn and Br–I alloys. Meanwhile, we find that the Br–Cl alloys exhibit sharper spectral features and a more uniform electroabsorption response indicative of an ordered structure, albeit still not as ordered as their pure Br and Cl counterparts. The band gap energies of the Br–Cl series (PEA2PbBrxCl4 – x) can be continuously tuned between 3.425 and 4.13 eV via the Br:Cl ratio, while the exciton binding energies can be tuned from 349 to 487 meV.

Historically the radiation efficiency of a rocket plume has been assumed to be 0.5%, but recent measurements have thrown this into some doubt. Determining the sound power level of a rocket is the first step in characterizing its radiation efficiency. Because the sound radiation from a launch vehicle is anisotropic, well-calibrated ground measurement stations are used, along with trajectory data, to obtain sound power. Historically, the effect of ground reflections appears largely to have been neglected in the literature, despite the potential to inflate overall power levels (OAPWL) and therefore radiation efficiency. This study investigates the likely effect of a finite-impedance ground on spectra, overall sound pressure levels (OASPL), and power levels. A single-parameter ground reflection model is used to obtain an estimate for change in OASPL for a model spectrum based on measured space vehicle launches. When the correction is applied to the OAPWL it produces in a nearly 3dB level reduction, therefore reducing the radiation efficiency by a factor of two. This indicates the probability that the radiation efficiency assumed for rockets in the past is too high.

The directivity function of a played musical instrument describes the angular dependence of its acoustic radiation and diffraction about the instrument, musician, and musician’s chair. In this study, high angular resolution directivity data were acquired in an anechoic chamber of a muted trumpet being played by a seated musician. The chair height and horizontal displacement ensured that the geometric center of the instrument’s radiating region fell at the circular center of a computer-controlled semi-circular array of 36 microphones positioned at 5-degree polar-angle increments. Azimuthal rotations progressed in 5-degree increments, such that the measurements involved 2,521 unique positions over a sphere. Additional measurements at a position within the rotating reference frame facilitated post-processing. The musician played chromatic scales at each rotation position, and this process was repeated for straight, cup, and wow wow mutes in order to draw comparisons in the directivity patterns of each mute to the unmuted trumpet. Radiation behind the musician increased as a result of the mute, and mute-dependent changes to the directivity patterns primarily occurred above 1 kHz.

Migratory bird refuge soundscapes are seasonally dynamic due to changes in wildlife populations. Some of the most prominent acoustical events in a bird refuge are the morning and evening avian choruses, particularly during spring and early summer when breeding activity of birds is high. This event is acoustically dynamic, reacting to both biotic and abiotic drivers. One such driver is the presence of standing water. For this study, near-continuous spectral data were collected at the U.S. Federal Fish and Wildlife Services Bear River Migratory Bird Refuge. Although data fidelity can be compromised by wind and rain, changes in the avian chorus characteristics over time are observed. These changes over time are observed to correlate with times management at the refuge drained the wetland area surrounding the recording sites. Recording sites that were close to drained wetland units saw decreases in the average sound pressure level during the dawn chorus, sometimes on the order of 20 dB.

Q-balls are non-topological solitons arising in scalar field theories. Solutions for rotating Q-balls (and the related boson stars) have been shown to exist when the angular momentum is equal to an integer multiple of the Q-ball charge Q. Here we consider the possibility of classically long-lived metastable rotating Q-balls with small angular momentum, even for large charge, for all scalar theories that support non-rotating Q-balls. This is relevant for rotating extensions of Q-balls and related solitons such as boson stars as it impacts their cosmological phenomenology.

The Allotrope Foundation (AF) started as a group of pharmaceutical companies, instrument, and software vendors that set out to simplify the exchange of data in the laboratory. After a decade of work, they released products that have found adoption in various companies. Most recently, the Allotrope Simple Model (ASM) was developed to speed up and widen the adoption. As a result, the Foundation has recently added chemical companies and, importantly, is reworking its business model to lower the entry barrier for smaller companies. Here, we present the proceedings from the Allotrope Connect Fall 2023 conference and summarize the technical and organizational developments at the Foundation since 2020.