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Magnetic signature of vertically migrating aggregations in the ocean
No full textThe transport of heat and solutes by vertically migrating aggregations of plankton has long been explored as a potentially important source of ocean mixing. However, direct evidence of enhanced mixing due to these migrations remains challenging to obtain and inconclusive. These shortcomings are due to the limitations of current measurement techniques, i.e., velocimetry techniques, which require a priori knowledge of the precise aggregation location and typically trigger animal avoidance behavior from introducing instrumentation into the migration. Here we develop a new approach to overcome these longstanding limitations by leveraging advancements in modern magnetometry to detect the flow-induced magnetic fields that naturally arise from seawater as it moves through the Earth's geomagnetic field. We derive quantitative predictions showing that these flow-induced magnetic fields in the vicinity of migrating aggregations have a strength proportional to the integrated fluid transport due to the migration. Importantly these magnetic signatures are potentially detectable remotely at a significant distance far from the aggregation and region of moving fluid with emerging quantum-enhanced magnetometry techniques such as Nitrogen-Vacancy centers in diamond. These results provide a new, testable framework for quantifying the significance of fluid transport in the ocean due to swimming organisms that may finally resolve a scientific debate with potentially enormous implications for our understanding of ocean dynamics and climate change
Optical O₂ sensors also respond to redox active molecules commonly secreted by bacteria
No full textFrom a metabolic perspective, molecular oxygen (O₂) is arguably the most significant constituent of Earth’s atmosphere. Nearly every facet of microbial physiology is sensitive to the presence and concentration of O₂, which is the most favorable terminal electron acceptor used by biology and also a dangerously reactive oxidant. As O₂ has such sweeping implications for physiology, researchers have developed diverse approaches to measure O₂ concentrations in natural and laboratory settings. Recent improvements to phosphorescent O₂ sensors piqued our interest due to the promise of optical measurement of spatiotemporal O₂ dynamics. However, we found that our preferred bacterial model, Pseudomonas aeruginosa PA14, secretes more than one molecule that quenches such sensors, complicating O₂ measurements in PA14 cultures and biofilms. Assaying supernatants from cultures of 9 bacterial species demonstrated that this phenotype is common: all supernatants quenched a soluble O₂ probe substantially. Phosphorescent O₂ probes are often embedded in solid support for protection, but an embedded probe called O₂ NS was quenched by most supernatants as well. Measurements using pure compounds indicated that quenching is due to interactions with redox-active small molecules including phenazines and flavins. Uncharged and weakly-polar molecules like pyocyanin were especially potent quenchers of O₂ NS. These findings underscore that optical O₂ measurements made in the presence of bacteria should be carefully controlled to ensure that O2, and not bacterial secretions, is measured, and motivate the design of custom O₂ probes for specific organisms to circumvent sensitivity to redox-active metabolites
Chiral cavity quantum electrodynamics
No full textCavity quantum electrodynamics, which explores the granularity of light by coupling a resonator to a nonlinear emitter, has played a foundational role in the development of modern quantum information science and technology. In parallel, the field of condensed matter physics has been revolutionized by the discovery of underlying topological, often arising from the breaking of time-reversal symmetry, as in the case of the quantum Hall effect. In this work, we explore the cavity quantum electrodynamics of a transmon qubit in a topologically nontrivial Harper–Hofstadter lattice. We assemble the lattice of niobium superconducting resonators and break time-reversal symmetry by introducing ferrimagnets before coupling the system to a transmon qubit. We spectroscopically resolve the individual bulk and edge modes of the lattice, detect Rabi oscillations between the excited transmon and each mode and measure the synthetic-vacuum-induced Lamb shift of the transmon. Finally, we demonstrate the ability to employ the transmon to count individual photons within each mode of the topological band structure. This work opens the field of experimental chiral quantum optics, enabling topological many-body physics with microwave photons and providing a route to backscatter-resilient quantum communication
Edge-of-the-Multis: Evidence for a Transition in the Outer Architectures of Compact Multiplanet Systems
No full textAlthough the architectures of compact multiple-planet systems are well characterized, there has been little examination of their “outer edges,” or the locations of their outermost planets. Here we present evidence that the observed high-multiplicity Kepler systems truncate at smaller orbital periods than can be explained by geometric and detection biases alone. To show this, we considered the existence of hypothetical planets orbiting beyond the observed transiting planets with properties dictated by the “peas-in-a-pod” patterns of intrasystem radius and period ratio uniformity. We evaluated the detectability of these hypothetical planets using (1) a novel approach for estimating the mutual inclination dispersion of multitransiting systems based on transit chord length ratios, and (2) a model of transit probability and detection efficiency that accounts for the impacts of planet multiplicity on completeness. Under the assumption that the “peas-in-a-pod” patterns continue to larger orbital separations than observed, we find that ≳35% of Kepler compact multis should possess additional detected planets beyond the known planets, constituting a ∼7σ discrepancy with the lack of such detections. These results indicate that the outer (∼100–300 days) regions of compact multis experience a truncation (i.e., an “edge-of-the-multis”) or a significant breakdown of the “peas-in-a-pod” patterns, in the form of systematically smaller radii or larger period ratios. We outline future observations that can distinguish these possibilities, and we discuss implications for planet formation theories
Mode hybridization in DNA-inspired helical metamaterials with variable centro-asymmetry
No full textWe study helical acoustic metamaterials and demonstrate the ability to vary the materials' dispersion properties by controlling geometrical structure and mass distribution. By locally adding eccentric, higher density elements in the unit cells, we perturb the moment of inertia of the system and introduce centro-asymmetry. This allows controlling the degree of mode coupling and the width of subwavelength bandgaps in the dispersion relation, which are the product of enhanced local resonance hybridization. We characterize the distinct normal modes in our metamaterials using finite element simulations and analytically quantify the coupling between each mode. The evolution of acoustic bandgaps induced by the increasing level of centro-asymmetry is experimentally validated with 3D-printed structures
Untangling the Galaxy. IV. Empirical Constraints on Angular Momentum Evolution and Gyrochronology for Young Stars in the Field
No full textWe present a catalog of ~100,000 periodic variable stars in TESS FFI data among members of widely distributed moving groups identified with Gaia in the previous papers in the series. By combining the periods from our catalog attributable to rotation with previously derived rotation periods for benchmark open clusters, we develop an empirical gyrochronology relation of angular momentum evolution that is valid for stars with ages 10-1000 Myr. Excluding stars rotating faster than 2 days, which we find are predominantly binaries, we achieve a typical age precision of ~0.2-0.3 dex and improving at older ages. Importantly, these empirical relations apply to not only FGK-type stars but also M-type stars, due to the angular momentum distribution being much smoother, simpler, continuous and monotonic as compared to the rotation period distribution. As a result, we are also able to begin tracing in fine detail the nature of angular momentum loss in low-mass stars as functions of mass and age. We characterize the stellar variability amplitudes of the cool stars as functions of mass and age, which may correlate with the starspot covering fractions. We also identify pulsating variables among the hotter stars in the catalog, including δ Scuti, γ Dor and SPB-type variables. These data represent an important step forward in being able to estimate precise ages of FGK- and M-type stars in the field, starting as early as the pre-main-sequence phase of evolution
Spectroscopic Confirmation of a Population of Isolated, Intermediate-Mass YSOs
No full textWide-field searches for young stellar objects (YSOs) can place useful constraints on the prevalence of clustered versus distributed star formation. The Spitzer/IRAC Candidate YSO (SPICY) catalog is one of the largest compilations of such objects (~120,000 candidates in the Galactic midplane). Many SPICY candidates are spatially clustered, but, perhaps surprisingly, approximately half the candidates appear spatially distributed. To better characterize this unexpected population and confirm its nature, we obtained Palomar/DBSP spectroscopy for 26 of the optically-bright (G<15 mag) "isolated" YSO candidates. We confirm the YSO classifications of all 26 sources based on their positions on the Hertzsprung-Russell diagram, H and Ca II line-emission from over half the sample, and robust detection of infrared excesses. This implies a contamination rate of <10% for SPICY stars that meet our optical selection criteria. Spectral types range from B4 to K3, with A-type stars most common. Spectral energy distributions, diffuse interstellar bands, and Galactic extinction maps indicate moderate to high extinction. Stellar masses range from ~1 to 7 M_⊙, and the estimated accretion rates, ranging from 3 × 10⁻⁸ to 3 × 10⁻⁷ M_⊙ yr⁻¹, are typical for YSOs in this mass range. The 3D spatial distribution of these stars, based on Gaia astrometry, reveals that the "isolated" YSOs are not evenly distributed in the Solar neighborhood but are concentrated in kpc-scale dusty Galactic structures that also contain the majority of the SPICY YSO clusters. Thus, the processes that produce large Galactic star-forming structures may yield nearly as many distributed as clustered YSOs
FIRE-3: Updated Stellar Evolution Models, Yields, & Microphysics and Fitting Functions for Applications in Galaxy Simulations
No full textIncreasingly, uncertainties in predictions from galaxy formation simulations (at sub-Milky Way masses) are dominated by uncertainties in stellar evolution inputs. In this paper, we present the full set of updates from the FIRE-2 version of the Feedback In Realistic Environments (FIRE) project code, to the next version, FIRE-3. While the transition from FIRE-1 to FIRE-2 focused on improving numerical methods, here we update the stellar evolution tracks used to determine stellar feedback inputs, e.g. stellar mass-loss (O/B and AGB), spectra (luminosities and ionization rates), and supernova rates (core-collapse and Ia), as well as detailed mass-dependent yields. We also update the low-temperature cooling and chemistry, to enable improved accuracy at T ≲ 10⁴ K and densities n ≫ 1 cm⁻³, and the meta-galactic ionizing background. All of these synthesize newer empirical constraints on these quantities and updated stellar evolution and yield models from a number of groups, addressing different aspects of stellar evolution. To make the updated models as accessible as possible, we provide fitting functions for all of the relevant updated tracks, yields, etc, in a form specifically designed so they can be directly 'plugged in' to existing galaxy formation simulations. We also summarize the default FIRE-3 implementations of 'optional' physics, including spectrally-resolved cosmic rays and supermassive black hole growth and feedback
Latinos, group identity, and equal opportunity on the 2020 California ballot
No full textObjective. Racial minority groups are often assumed to support equal opportunity policies, with most research focused on biracial contexts between Whites and Blacks. With a unique opportunity to study richer contexts from California's 2020 elections, we test whether Latino voters supported ballot measures associated with equal opportunity.
Methods. Using data on vote choice for Propositions 15 (raising commercial property taxes) and 16 (repealing prohibition of affirmative action) from a post-election survey of California registrants, we use logistic regression to test whether Latino support for equal opportunity policies is higher than that of Whites.
Results. For both propositions, while Latino support was higher than White support, it was not statistically different when controlled for partisanship.
Conclusion. There is little evidence to suggest that California Latinos support equal opportunity policies more strongly than White voters. This lukewarm support may explain the fates of both propositions in the election
Novel sulfur isotope analyses constrain sulfurized porewater fluxes as a minor component of marine dissolved organic matter
No full textMarine dissolved organic matter (DOM) is a major reservoir that links global carbon, nitrogen, and phosphorus. DOM is also important for marine sulfur biogeochemistry as the largest water column reservoir of organic sulfur. Dissolved organic sulfur (DOS) can originate from phytoplankton-derived biomolecules in the surface ocean or from abiotically “sulfurized” organic matter diffusing from sulfidic sediments. These sources differ in ³⁴S/³²S isotope ratios (δ³⁴S values), with phytoplankton-produced DOS tracking marine sulfate (21‰) and sulfurized DOS mirroring sedimentary porewater sulfide (∼0 to –10‰). We measured the δ³⁴S values of solid-phase extracted (SPE) DOM from marine water columns and porewater from sulfidic sediments. Marine DOMSPE δ³⁴S values ranged from 14.9‰ to 19.9‰ and C:S ratios from 153 to 303, with lower δ³⁴S values corresponding to higher C:S ratios. Marine DOMSPE samples showed consistent trends with depth: δ³⁴S values decreased, C:S ratios increased, and δ13C values were constant. Porewater DOMSPE was ³⁴S-depleted (∼-0.6‰) and sulfur-rich (C:S ∼37) compared with water column samples. We interpret these trends as reflecting at most 20% (and on average ∼8%) contribution of abiotic sulfurized sources to marine DOSSPE and conclude that sulfurized porewater is not a main component of oceanic DOS and DOM. We hypothesize that heterogeneity in δ³⁴S values and C:S ratios reflects the combination of sulfurized porewater inputs and preferential microbial scavenging of sulfur relative to carbon without isotope fractionation. Our findings strengthen links between oceanic sulfur and carbon cycling, supporting a realization that organic sulfur, not just sulfate, is important to marine biogeochemistry