Magnificent Desolation

We here investigate how the synthesis method affects the crystallite size and atomic structure of cobalt iron oxide nanoparticles. By using a simple solvothermal method, we first synthesized cobalt ferrite nanoparticles of ca. 2 and 7 nm, characterized by Transmission Electron Microscopy (TEM), Small Angle X-ray scattering (SAXS), X-ray and neutron total scattering. The smallest particle size corresponds to only a few spinel unit cells. Nevertheless, Pair Distribution Function (PDF) analysis of X-ray and neutron total scattering data shows that the atomic structure, even in the smallest nanoparticles, is well described by the spinel structure, although with significant disorder and a contraction of the unit cell parameter. These effects can be explained by the surface oxidation of the small nanoparticles, which is confirmed by X-ray near edge absorption spectroscopy (XANES). Neutron total scattering data and PDF analysis reveal a higher degree of inversion in the spinel structure of the smallest nanoparticles. Neutron total scattering data also allow magnetic PDF (mPDF) analysis, which shows that the ferrimagnetic domains correspond to ca. 80% of the crystallite size in the larger particles. A similar but less well-defined magnetic ordering was observed for the smallest nanoparticles. Finally, we used a co-precipitation synthesis method at room temperature to synthesize ferrite nanoparticles similar in size to the smallest crystallites synthesized by the solvothermal method. Structural analysis with PDF demonstrates that the ferrite nanoparticles synthesized via this method exhibit a significantly more defective structure compared to those synthesized via a solvothermal method.

The Haumea family is the only known dynamical family in the trans-Neptunian region. To date, 10 family members have been unambiguously identified using near-infrared (NIR) spectral or photometric data in combination with their strong dynamical proximity and the rest of the family. In this work, we build off previous empirically constructed models of the family to identify 39 candidate family members and follow up on eight of them using the Hubble Space Telescope (HST) to measure their visible and NIR colors. Six of the candidates have strong water-ice absorption features—consistent with family membership. Based on these initial findings, our sample of 39 candidate family members should contain about 20 more water-rich objects. Combining the HST visible and NIR photometry with past results, we find no evidence for significant color heterogeneity within the family. Of the six new family members, two have Δv ∼ 300 m s−1, well outside of the traditionally defined velocity dispersion limit of ∼150 m s−1. As evidence suggests they are not affected by any of Neptune's resonances, we propose that these family members are the result of dynamical sculpting by Neptune during its outward migration. Further searches for far-flung family members will be able to further explore this hypothesis.

The kinetic mixing of two U(1) gauge theories can result in a massless photon that has perturbative couplings to both electric and magnetic charges. This framework can be used to perturbatively calculate in a quantum field theory with both kinds of charge. Here we reexamine the running of the magnetic charge, where the calculations of Schwinger and Coleman sharply disagree. We calculate the running of both electric and magnetic couplings and show that the disagreement between Schwinger and Coleman is due to an incomplete summation of topological terms in the perturbation series. We present a momentum space prescription for calculating the loop corrections in which the topological terms can be systematically separated for resummation. Somewhat in the spirit of modern amplitude methods we avoid using a vector potential and use the field strength itself, thereby trading gauge redundancy for the geometric redundancy of Stokes surfaces. The resulting running of the couplings demonstrates that Dirac charge quantization is independent of renormalization scale, as Coleman predicted. As a simple application we also bound the parameter space of magnetically charged states through the experimental measurement of the running of electromagnetic coupling.

Far-field (9.7–35.5 km) noise measurements were made during the fifth flight test of SpaceX's Starship Super Heavy, which included the first-ever booster catch. Key results involving launch and flyback sonic boom sound levels include (a) A-weighted sound exposure levels during launch are 18 dB less than predicted at 35 km; (b) the flyback sonic boom exceeds 10 psf at 10 km; and (c) comparing Starship launch noise to Space Launch System and Falcon 9 shows that Starship is substantially louder; the far-field noise produced during a Starship launch is at least ten times that of Falcon 9.

Advanced construction technologies are creating opportunities to design and fabricate non-traditional concrete structural geometries. While removing structurally unnecessary material can aid in sustainability efforts, it can also reduce a structure’s ability to attenuate impact sound. An assessment of the impact sound insulation performance of custom concrete floors has often been excluded from previous studies because of the large computational cost for simulating radiated sound at high frequencies. In response, this paper presents a hybrid, computationally efficient method to approximate the impact sound performance of floors by strategically using the air-hemisphere method for a subset of low frequencies, while relying on the structure’s radiation efficiency at higher frequencies. This method improves upon existing strategies to discretize the receiving side of the floor for impact sound performance. To demonstrate this method, six anthropometric walking paths are simulated on four non-traditional floor geometries and three conventional floor slabs. The simulated results are compared to experimentally obtained dynamic behavior for the custom slabs and full-scale tests of impact sound for the conventional slabs. The proposed method is much more efficient than maintaining high resolution discretization across all frequencies, leading to significant computational time savings. Efficient simulations for determining the impact sound insulation of non-traditional structures may further enable the design of novel floor geometries, potentially accelerating their implementation in buildings.

Spatiospectral lobes are significant contributors to noise radiated from full-scale tactical aircraft. Prior studies have explored lobe frequency-domain characteristics, but a joint time–frequency domain analysis has the potential to further describe these phenomena and connect them to source-related events in the time waveform. This paper uses acoustical data collected from a 120-microphone array near a T-7A-installed F404 engine to characterize the spatiospectral lobes in combinations of the time, frequency, and spatial domains. An event-based beamforming method is used in conjunction with a wavelet transform to determine propagation angles and event source locations corresponding to each of the lobes. Temporospectral events in the wavelet transform are then analyzed using Markov chains. Finally, spatiospectral maps created from the measured data are decomposed into individual lobes using events in the wavelet transform as a guide. The spatiospectrotemporal combination of these three analyses shows that the lobes originate from multiple, overlapping regions along the jet lipline and that each lobe has its own peak radiation angle. Additionally, events corresponding to the spatiospectral lobes occur intermittently and at different times from each other, leading to bursts of acoustic energy with rapidly changing directivities.