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Ion mobility spectrometry (IMS) can delineate gas-phase ions and probe their geometries. Coupling with electrospray ionization and MS has brought IMS to structural biology, revealing the macromolecular folding and subunit connectivity. However, the orientational averaging of ion–molecule collision cross sections (Ω) in the linear and field asymmetric waveform IMS (FAIMS) diminishes the resolution and structural specificity. In the novel low-field differential (LOD) IMS, a field too weak for ion heating (and thus FAIMS) aligns strong macrodipoles, capturing their magnitudes and directional Ω across the dipole (Ω⊥). However, the bisinusoidal waveforms (from FAIMS) have compromised the resolution, measurement accuracy, and correlation to the ion properties. Large ions amenable to LODIMS have low mobility and diffuse slowly, allowing the waveform frequencies down to ∼10 kHz. The low field and frequency permit generating the ideal rectangular waveforms with a flexible frequency and duty cycle by direct switching (impractical for FAIMS) in a miniature low-power format. This new IMS stage is evaluated for the exemplary large protein albumin (66 kDa) previously studied using the bisinusoidal waveform. The flat voltages and greater form factor initiate the differential IMS effect at lower fields, expand the separation space, and enable the quantification of Ω⊥ values by varying the duty cycle. 

Abstract The Sunspot Solar Observatory Data Archive (SSODA) stores data acquired with the suite of instruments at the Richard B. Dunn Solar Telescope (DST) from February 2018 to the present. The instrumentation at the DST continues to provide high cadence imaging, spectroscopy, and polarimetry of the solar photosphere and chromosphere across a wavelength range from 3500 Å to 11,000 Å. At the time of writing, the archive contains approximately 374 TiB of data across more than 520 observing days (starting on February 1, 2018). These numbers are approximate as the DST remains operational, and is actively adding new data to the archive. The SSODA includes both raw and calibrated data. A subset of the archive contains the results of photospheric and chromospheric spectropolarimetric inversions using the Hazel-2.0 code to obtain maps of magnetic fields, temperatures, and velocity flows. The SSODA represents a unique resource for the investigation of plasma processes throughout the solar atmosphere, the origin of space weather events, and the properties of active regions throughout the rise of Solar Cycle 25. 

Recent improvements to the comparison-based method of digital waveform generation increased the reproducibility of the waveforms so that the higher-order Mathieu stability zones can be accessed reliably. Digitally driven quadrupole mass filters access these zones using a fixed AC voltage and rectangular waveforms that are defined by a duty cycle. In this context, the duty cycle is the fraction of the waveform period where the waveform remains in the high state. Because digitally driven quadrupoles navigate stability using a duty cycle, there is no need to apply a resolving DC offset between electrode pairs. Accessing the higher stability zones using a conventional resonantly-tuned RF requires the use of thousands of AC and DC voltages making the mode of operation less accessible with these devices. Stability zones higher than (1,1) and (2,1) have theoretical resolving powers that are on the order 1,140 and 3,447 at FWHM which drives efforts to practically access these operational conditions. Accessing these zones digitally requires the use of extremely precise waveforms. In a previous effort, waveform generation produced waveforms to reliably access the (1,1) and (2,1) zones without impacting performance. However, recent work found more improvement was needed to reliably access neighboring higher stability zones. Derived from that work, it was determined that a waveform resolution of ~10 ppm or less was needed to reliably access the (3,1) and (3,2) zones. The present work utilized digital waveforms that achieve this level of precision to experimentally access and characterize attributes of the (3,1) and (3,2) zones. This work dives into the investigation of different beam energies to overcome the destabilizing fringing fields, improve transmission, and their overall effect on the experimental resolving power and signal-to-noise. In addition, the AC voltage of the driving RF was varied to understand the effects on the initial ion beam energy that is needed to achieve balanced separation and how the overall signal-to-noise is affected. Lastly, an assessment was made on the effects of the temporal parameters of a digital mass scan on peak sensitivity, peak fidelity, and overall duration for a scan. 

Abstract. Dry deposition of ozone (O3) to the ocean surface and the ozonolysis of organics in the sea surface microlayer (SSML) are potential sources of volatile organic compounds (VOCs) to the marine atmosphere. We use a gas chromatography system coupled to a Vocus proton-transfer-reaction time-of-flight mass spectrometer to determine the chemical composition and product yield of select VOCs formed from ozonolysis of coastal seawater collected from Scripps Pier in La Jolla, California. Laboratory-derived results are interpreted in the context of direct VOC vertical flux measurements made at Scripps Pier. The dominant products of laboratory ozonolysis experiments and the largest non-sulfur emission fluxes measured in the field correspond to Vocus CxHy+ and CxHyOz+ ions. Gas chromatography (GC) analysis suggests that C5–C11 oxygenated VOCs, primarily aldehydes, are the largest contributors to these ion signals. In the laboratory, using a flow reactor experiment, we determine a VOC yield of 0.43–0.62. In the field at Scripps Pier, we determine a maximum VOC yield of 0.04–0.06. Scaling the field and lab VOC yields for an average O3 deposition flux and an average VOC structure results in an emission source of 10.7 to 167 Tg C yr−1, competitive with the DMS source of approximately 20.3 Tg C yr−1. This study reveals that O3 reactivity to dissolved organic carbon can be a significant carbon source to the marine atmosphere and warrants further investigation into the speciated VOC composition from different seawater samples and the reactivities and secondary organic aerosol (SOA) yields of these molecules in marine-relevant, low NOx conditions. 

Forced variational integrators are given by the discretization of the Lagrange-d’Alembert principle for systems subject to external forces, and have proved useful for numerical simulation studies of complex dynamical systems. In this paper we model a passive walker with foot slip by using techniques of geometric mechanics, and we construct forced variational integrators for the system. Moreover, we present a methodology for generating (locally) optimal control policies for simple hybrid holonomically constrained forced Lagrangian systems, based on discrete mechanics, applied to a controlled walker with foot slip in a trajectory tracking problem. 

Forced variational integrators are given by the discretization of the Lagrange-d’Alembert principle for systems subject to external forces, and have proved useful for numerical simulation studies of complex dynamical systems. In this paper we model a passive walker with foot slip by using techniques of geometric mechanics, and we construct forced variational integrators for the system. Moreover, we present a methodology for generating (locally) optimal control policies for simple hybrid holonomically constrained forced Lagrangian systems, based on discrete mechanics, applied to a controlled walker with foot slip in a trajectory tracking problem. 

Abstract We present 1–12 GHz Karl G. Jansky Very Large Array observations of nine off-nuclear persistent radio sources (PRSs) in nearby (z≲ 0.055) dwarf galaxies, along with high-resolution European VLBI Network observations for one of them at 1.7 GHz. We explore the plausibility that these PRSs are associated with fast radio burst (FRB) sources by examining their properties—physical sizes, host-normalized offsets, spectral energy distributions (SEDs), radio luminosities, and light curves—and compare them to those of the PRSs associated with FRB 20121102A and FRB 20190520B, two known active galactic nuclei (AGN), and one likely AGN in our sample with comparable data, as well as other radio transients exhibiting characteristics analogous to FRB-PRSs. We identify a single source in our sample, J1136+2643, as the most promising FRB-PRS, based on its compact physical size and host-normalized offset. We further identify two sources, J0019+1507 and J0909+5655, with physical sizes comparable to FRB-PRSs, but which exhibit large offsets and flat spectral indices potentially indicative of a background AGN origin. We test the viability of neutron star wind nebula and hypernebula models for J1136+2643 and find that the physical size, luminosity, and SED of J1136+2643 are broadly consistent with these models. Finally, we discuss the alternative interpretation that the radio sources are instead powered by accreting massive black holes, and we outline future prospects and follow-up observations for differentiating between these scenarios. 

ABSTRACT Localization of fast radio bursts (FRBs) to arcsecond and subarcsecond precision maximizes their potential as cosmological probes. To that end, FRB detection instruments are deploying triggered complex-voltage capture systems to localize FRBs, identify their host galaxy, and measure a redshift. Here, we report the discovery and localization of two FRBs (20220717A and 20220905A) that were captured by the transient buffer system deployed by the MeerTRAP instrument at the MeerKAT telescope in South Africa. We were able to localize the FRBs to precision of $$\sim$$1 arcsecond that allowed us to unambiguously identify the host galaxy for FRB 20220717A (posterior probability $$\sim$$0.97). FRB 20220905A lies in a crowded region of the sky with a tentative identification of a host galaxy but the faintness and the difficulty in obtaining an optical spectrum preclude a conclusive association. The bursts show low linear polarization fractions (10–17 per cent) that conform to the large diversity in the polarization fraction observed in apparently non-repeating FRBs akin to single pulses from neutron stars. We also show that the host galaxy of FRB 20220717A contributes roughly 15 per cent of the total dispersion measure (DM), indicating that it is located in a plasma-rich part of the host galaxy which can explain the large rotation measure. The scattering in FRB 20220717A can be mostly attributed to the host galaxy and the intervening medium and is consistent with what is seen in the wider FRB population. 

Abstract The discovery and localization of FRB 20240209A by the Canadian Hydrogen Intensity Mapping Fast Radio Burst (CHIME/FRB) experiment marks the first repeating FRB localized with the CHIME/FRB Outriggers and adds to the small sample of repeating FRBs with associated host galaxies. Here we present Keck and Gemini observations of the host that reveal a redshiftz = 0.1384 ± 0.0004. We perform stellar population modeling to jointly fit the optical through mid-IR data of the host and infer a median stellar mass log(M_*/M_⊙) = 11.35 ± 0.01 and a mass-weighted stellar population age  ~11 Gyr, corresponding to the most massive and oldest FRB host discovered to date. Coupled with a star formation rate  <0.31M_⊙yr⁻¹, the specific star formation rate  <10^−11.9yr⁻¹classifies the host as quiescent. Through surface brightness profile modeling, we determine an elliptical galaxy morphology, marking the host as the first confirmed elliptical FRB host. The discovery of a quiescent early-type host galaxy within a transient class predominantly characterized by late-type star-forming hosts is reminiscent of short-duration gamma-ray bursts, Type Ia supernovae, and ultraluminous X-ray sources. Based on these shared host demographics, coupled with a large offset as demonstrated in our companion Letter, we conclude that preferred sources for FRB 20240209A include magnetars formed through merging binary neutron stars/white dwarfs or the accretion-induced collapse of a white dwarf, or a luminous X-ray binary. Together with FRB 20200120E localized to a globular cluster in M81, our findings provide strong evidence that some fraction of FRBs may arise from a process distinct from the core collapse of massive stars.