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The Increasingly Strange Polarimetric Behavior of the Barbarian Asteroids
No full textPolarization phase-curve measurements provide a unique constraint on the surface properties of asteroids that are complementary to those from photometry and spectroscopy and have led to the identification of the “Barbarian” asteroids as a class of objects with highly unusual surfaces. We present new near-infrared polarimetric observations of six Barbarian asteroids obtained with the WIRC+Pol instrument on the Palomar Hale telescope. We find a dramatic change in polarimetric behavior from visible to near-infrared for these objects, including a change in the polarimetric inversion angle that is tied to the index of refraction of the surface material. Our observations support a two-phase surface composition consisting of high albedo and high index of refraction inclusions with a small optical size scale embedded in a dark matrix material more closely related to C-complex asteroids. These results are consistent with the interpretation that the Barbarians are remnants of a population of primitive bodies that formed shortly after calcium-aluminum-rich inclusion (CAIs). Near-infrared polarimetry provides a direct test of the constituent grains of asteroid surfaces
The infinite level normal forms for non-resonant double Hopf singularities
No full textIn this paper, we explore hypernormal forms of vector fields that have non-resonant double Hopf singularities with a non-zero radial cubic part. Our primary focus is on investigating the infinite-level normal form classification of this type of singularities. We provide a normal form decomposition in terms of planar-rotating and planar-radial vector fields, which greatly facilitate the pattern recognition and analysis of the corresponding generalized homological maps. Notably, our paper represents the first instance of the normal form classification for general non-resonant double Hopf singularities without structural symmetry
Cold Spring Harbor Laboratory 2022: emerging insights and viewpoints in immunology
No full textSome of the current and former organizers of the Cold Spring Harbor Laboratory (CSHL) ‘Gene Expression and Signaling in the Immune System’ (GESIS) meeting offer opinions on emerging questions in immunology, discussing the strong value of this recurring scientific meeting in the field
Effect of Leading-Edge Cranks on Stability and Control of Active-Flow-Control-Enabled Tailless Aircraft
No full textThe Swept Wing Flow Test (SWIFT) is a tailless unmanned combat aerial vehicle (UCAV) model to be tested at high Reynolds numbers in NASA’s National Transonic Facility. The model is designed around a [Formula: see text]-shaped wing with a single, large crank at its leading edge (LE). It suffers from an unstable nose-up pitch departure resulting from flow separation augmented by the LE crank. A small-scale, modular wind tunnel model ([Formula: see text]) was built that allowed for changes in the crank angle by increasing the outboard wing sweep. Eliminating the crank entirely increased the [Formula: see text] and changed the sign of pitch departure, thus exposing the significance of the LE crank. The model was equipped with sweeping jet actuators that could be individually enabled by valves located at the actuator inlets, allowing one to explore the role of active flow control (AFC) in expanding the model’s longitudinal stability margins and controlling its yaw while being cognizant of the coupling between changes in the model’s planform and their effect on AFC. Test results indicated that selective actuation depending on the model’s attitude modified the flow and dramatically increased the trimmed [Formula: see text], while further suggesting that the actuation should dynamically change with incidence to improve AFC efficacy
The Earliest Stage of Galactic Star Formation
No full textUsing a recently developed technique to estimate gas temperatures (T_(SF)) in star-forming regions from large photometric surveys, we propose a diagram, analogous to the Hertzsprung–Russell diagram for individual stars, to probe the evolution of individual galaxies. On this T_(SF)-sSFR (specific star formation rate) diagram, a small fraction of star-forming galaxies appear to be dominated by different feedback mechanisms than typical star-forming galaxies. These galaxies generically have younger stellar populations and lower stellar masses and increase in relative abundance toward higher redshifts, so we argue that these objects are in an earlier stage of galactic star formation. Further, Hubble observations find that these "core-forming" galaxies also exhibit distinct morphology and that tracks on the T_(SF)-sSFR diagram are also a morphological sequence. Thus, unlike starburst phases which can be triggered environmentally, these earliest core-forming galaxies appear to be a stage that typical galaxies go through early in their star formation history. We therefore argue that most galaxies first go through a core formation stage, then subsequently disk formation, and finally become quiescent
Quantum synchronization effects induced by strong nonlinearities
No full textA paradigm for quantum synchronization is the quantum analog of the Stuart-Landau oscillator, which corresponds to a van der Pol oscillator in the limit of weak (i.e., vanishingly small) nonlinearity. Due to this limitation, the quantum Stuart-Landau oscillator fails to capture interesting nonlinearity-induced phenomena such as relaxation oscillations. To overcome this deficiency, we propose an alternative model that approximates the Duffing–van der Pol oscillator to finitely large nonlinearities while remaining numerically tractable. This allows us to uncover interesting phenomena in the deep-quantum strongly nonlinear regime with no classical analog, such as the persistence of amplitude death on resonance. We also report nonlinearity-induced position correlations in reactively coupled quantum oscillators. Such coupled oscillations become more and more correlated with increasing nonlinearity before reaching some maximum. Again, this behavior is absent classically. We also show how strong nonlinearity can enlarge the synchronization bandwidth in both single and coupled oscillators. This effect can be harnessed to induce mutual synchronization between two oscillators initially in amplitude death
Asymmetry of carbon sequestrations by plant and soil after forestation regulated by soil nitrogen
No full textForestation is regarded as an effective strategy for increasing terrestrial carbon sequestration. However, its carbon sink potential remains uncertain due to the scarcity of large-scale sampling data and limited knowledge of the linkage between plant and soil C dynamics. Here, we conduct a large-scale survey of 163 control plots and 614 forested plots involving 25304 trees and 11700 soil samples in northern China to fill this knowledge gap. We find that forestation in northern China contributes a significant carbon sink (913.19 ± 47.58 Tg C), 74% of which is stored in biomass and 26% in soil organic carbon. Further analysis reveals that the biomass carbon sink increases initially but then decreases as soil nitrogen increases, while soil organic carbon significantly decreases in nitrogen-rich soils. These results highlight the importance of incorporating plant and soil interactions, modulated by nitrogen supply in the calculation and modelling of current and future carbon sink potential
Entanglement asymmetry as a probe of symmetry breaking
No full textSymmetry and symmetry breaking are two pillars of modern quantum physics. Still, quantifying how much a symmetry is broken is an issue that has received little attention. In extended quantum systems, this problem is intrinsically bound to the subsystem of interest. Hence, in this work, we borrow methods from the theory of entanglement in many-body quantum systems to introduce a subsystem measure of symmetry breaking that we dub entanglement asymmetry. As a prototypical illustration, we study the entanglement asymmetry in a quantum quench of a spin chain in which an initially broken global U(1) symmetry is restored dynamically. We adapt the quasiparticle picture for entanglement evolution to the analytic determination of the entanglement asymmetry. We find, expectedly, that larger is the subsystem, slower is the restoration, but also the counterintuitive result that more the symmetry is initially broken, faster it is restored, a sort of quantum Mpemba effect, a phenomenon that we show to occur in a large variety of systems
Decomposition and Inference of Sources through Spatiotemporal Analysis of Network Signals: The DISSTANS Python package
No full textDense, regional-scale, continuously-operating Global Navigation Satellite System (GNSS) networks enable the monitoring of plate motion and regional surface deformation. The spatial extent and density of these networks, as well as the length of observation records, have steadily increased in the past three decades. Software to efficiently analyze the ever-increasing amount of available timeseries should be geographically portable and computationally efficient, allow for automation, use spatial correlation (exploiting the fact that nearby stations experience common signals), and have openly accessible source code as well as documentation. We introduce the DISSTANS Python package, which aims to be generic (therefore portable), parallelizable (fast), and able to exploit the spatial structure of the observation records in a user-assisted, semi-automated framework that includes uncertainty propagation. DISSTANS is open-source, includes an application interface documentation as well as usage tutorials, and is easily extendable. We present two case studies that demonstrate our code, one using a synthetic dataset and one using real GNSS network timeseries