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Elliot M. Meyerowitz
No full textElliot Meyerowitz is the George Beadle Professor of Biology, and a Howard Hughes Medical Institute Investigator at the California Institute of Technology, where he has been on the faculty since 1980. In 2011 and 2012, while on leave from Caltech, he served as the Inaugural Director of the Sainsbury Laboratory at the University of Cambridge. The Meyerowitz laboratory studies the development of Arabidopsis, and also the cell biology and growth of a giant unicellular alga, Caulerpa. Current studies concentrate on the interrelated roles of mechanical and chemical signaling in plant morphogenesis, using genetics, genomics, and live imaging. With collaborators, they also develop computational models of plant growth and development, as both sources and tests of experimental hypotheses
Planet engulfment signatures in twin stars
No full textPlanet engulfment can be inferred from enhancement of refractory elements in the photosphere of the engulfing star following accretion of rocky planetary material. Such refractory enrichments are subject to stellar interior mixing processes, namely thermohaline mixing induced by an inverse mean-molecular-weight gradient between the convective envelope and radiative core. Using ᴍᴇsᴀ stellar models, we quantified the strength and duration of engulfment signatures following planet engulfment. We found that thermohaline mixing dominates during the first ∼5-45 Myr post-engulfment, weakening signatures by a factor of ∼2 before giving way to depletion via gravitational settling on longer time-scales. Solar metallicity stars in the 0.5-1.2 M_⊙ mass range have observable signature time-scales of ∼1 Myr-8 Gyr, depending on the engulfing star mass and amount of material engulfed. Early type stars exhibit larger initial refractory enhancements but more rapid depletion. Solar-like stars (M = 0.9-1.1 M_⊙) maintain observable signatures (>0.05 dex) over time-scales of ∼20 Myr-1.7 Gyr for nominal 10 M_⊕ engulfment events, with longer-lived signatures occurring for low-metallicity and/or hotter stars (1 M_⊙, ∼2-3 Gyr). Engulfment events occurring well after the zero-age main sequence produce larger signals due to suppression of thermohaline mixing by gravitational settling of helium (1 M_⊙, ∼1.5 Gyr). These results indicate that it may be difficult to observe engulfment signatures in solar-like stars that are several Gyr old
Draft Genome Assembly of Stutzerimonas sp. Strain S1 and Achromobacter spanius Strain S4, Two Syringol-Metabolizing Bacteria Isolated from Compost Soil
No full textTwo bacterial strains able to use syringol as a sole carbon source were isolated from compost. The isolates, named S1 and S4, were sequenced using the Illumina platform. The final assemblies contained 4.2 Mbp, 63% GC, and 3,912 genes for S1 and 6.2 Mbp, 64% GC, and 5,503 genes for S4
The origin of ultramassive white dwarfs: hints from Gaia EDR3
No full textGaia Data Release 2 revealed a population of ultramassive white dwarfs on the Q branch that are moving anomalously fast for a local disc population with their young photometric ages. As the velocity dispersion of stars in the local disc increases with age, a proposed explanation of these white dwarfs is that they experience a cooling delay that causes current cooling models to infer photometric ages much younger than their true ages. To explore this explanation, we investigate the kinematics of ultramassive white dwarfs within 200 pc of the Sun using the improved Gaia Early Data Release 3 observations. We analyse the transverse motions of 0.95–1.25 M_⊙ white dwarfs, subdivided by mass and age, and determine the distributions of the three-dimensional components of the transverse velocities. The results are compared to expectations based on observed kinematics of local main-sequence stars. We find a population of photometrically young (∼0.5–1.5 Gyr) ultramassive (∼1.15–1.25 M_⊙) white dwarfs for which the transverse velocity component in the direction of Galactic rotation is more dispersed than for local disc stars of any age; thus, it is too dispersed to be explained by any cooling delay in white dwarfs originating from the local disc. Furthermore, the dispersion ratio of the velocity components in the Galactic plane for this population is also inconsistent with a local disc origin. We discuss some possible explanations of this kinematically anomalous population, such as a halo origin or production through dynamical effects of stellar triple systems
Anatomy of the electroweak phase transition for dark sector induced baryogenesis
No full textWe investigate the electroweak phase transition patterns for a recently proposed baryogenesis model with CP violation originated in the dark sector. The model includes a complex scalar singlet-Higgs boson portal, a U(1)ₗ gauge lepton symmetry with a Z′ gauge boson portal and a fermionic dark matter particle. We find a novel thermal history of the scalar sector, featuring a Z₂ breaking singlet vacuum in the early Universe driven by a dark Yukawa coupling, that induces a one-step strongly first order electroweak phase transition. We explore the parameter space that generates the observed matter-antimatter asymmetry and dark matter relic abundance, while being consistent with constraints from electric dipole moment, collider searches, and dark matter direct detection bounds. The complex singlet can be produced via the Higgs portal and decays into Standard Model particles after traveling a certain distance. We explore the reach for long-lived singlet scalars at the 13 TeV Large Hadron Collider with ℒ = 139 fb⁻¹ and show its impact on the parameter space of the model. Setting aside currently unresolved theoretical uncertainties, we estimate the gravitational wave signatures detectable at future observatories
NEID Reveals That the Young Warm Neptune TOI-2076 b Has a Low Obliquity
No full textTOI-2076 b is a sub-Neptune-sized planet (R = 2.39 ± 0.10 R_⊕) that transits a young (204 ± 50 MYr) bright (V = 9.2) K-dwarf hosting a system of three transiting planets. Using spectroscopic observations obtained with the NEID spectrograph on the WIYN 3.5 m Telescope, we model the Rossiter–McLaughlin effect of TOI-2076 b, and derive a sky-projected obliquity of λ = -3₋₁₅⁺¹⁶°. Using the size of the star (R = 0.775 ± 0.015 R_⊙), and the stellar rotation period (P_(rot) = 7.27 ± 0.23 days), we estimate an obliquity of ψ ={18₋₉⁺¹⁰° (ψ < 34° at 95% confidence), demonstrating that TOI-2076 b is in a well-aligned orbit. Simultaneous diffuser-assisted photometry from the 3.5 m telescope at Apache Point Observatory rules out flares during the transit. TOI-2076 b joins a small but growing sample of young planets in compact multi-planet systems with well-aligned orbits, and is the fourth planet with an age ≲ 300 Myr in a multi-transiting system with an obliquity measurement. The low obliquity of TOI-2076 b and the presence of transit timing variations in the system suggest the TOI-2076 system likely formed via convergent disk migration in an initially well-aligned disk
Neural connectivity molecules best identify the heterogeneous clock and dopaminergic cell types in the Drosophila adult brain
No full textOur recent single-cell sequencing of most adult Drosophila circadian neurons indicated notable and unexpected heterogeneity. To address whether other populations are similar, we sequenced a large subset of adult brain dopaminergic neurons. Their gene expression heterogeneity is similar to that of clock neurons, i.e., both populations have two to three cells per neuron group. There was also unexpected cell-specific expression of neuron communication molecule messenger RNAs: G protein–coupled receptor or cell surface molecule (CSM) transcripts alone can define adult brain dopaminergic and circadian neuron cell type. Moreover, the adult expression of the CSM DIP-beta in a small group of clock neurons is important for sleep. We suggest that the common features of circadian and dopaminergic neurons are general, essential for neuronal identity and connectivity of the adult brain, and that these features underlie the complex behavioral repertoire of Drosophila
The Apparent Absence of Forward Scattering in the HD 53143 Debris Disk
No full textHD 53143 is a mature Sun-like star and host to a broad disk of dusty debris, including a cold outer ring of planetesimals near 90 au. Unlike most other inclined debris disks imaged at visible wavelengths, the cold disk around HD 53143 appears as disconnected “arcs” of material, with no forward-scattering side detected to date. We present new, deeper Hubble Space Telescope Imaging Spectrograph coronagraphic observations of the HD 53143 debris disk and show that the forward-scattering side of the disk remains undetected. By fitting our KLIP-reduced observations via forward modeling with an optically thin disk model, we show that fitting the visible wavelength images with an azimuthally symmetric disk with unconstrained orientation results in an unphysical edge-on orientation that is at odds with recent ALMA observations, while constraining the orientation to that observed by ALMA results in nearly isotropically scattering dust. We show that the HD 53143 host star exhibits significant stellar variations due to spot rotation and revisit age estimates for this system
Poly‐Catecholic Functionalization of Biomolecules for Rapid Gelation, Robust Injectable Bioadhesion, and Near‐Infrared Responsiveness
No full textMussel-inspired catechol-functionalization of degradable natural biomaterials has garnered significant interest as an approach to achieve bioadhesion for sutureless wound closure. However, conjugation capacity in standard coupling reactions, such as carbodiimide chemistry, is limited by low yield and lack of abundant conjugation sites. Here, a simple oxidative polymerization step before conjugation of catechol-carrying molecules (i.e., 3,4-dihydroxy-l-phenylalanine, l-DOPA) as a potential approach to amplify catechol function in bioadhesion of natural gelatin biomaterials is proposed. Solutions of gelatin modified with poly(l-DOPA) moieties (GelDOPA) are characterized by faster physical gelation and increased viscosity, providing better wound control on double-curved tissue surfaces compared to those of l-DOPA-conjugated gelatin. Physical hydrogels treated topically with low concentrations of NaIO4 solutions are crosslinked on-demand via through-thickness diffusion. Poly(l-DOPA) conjugates enhance crosslinking density compared to l-DOPA conjugated gelatin, resulting in lower swelling and enhanced cohesion in physiological conditions. Together with cohesion, more robust bioadhesion at body temperature is achieved by poly(l-DOPA) conjugates, exceeding those of commercial sealants. Further, poly(l-DOPA) motifs introduced photothermal responsiveness via near-infrared (NIR) irradiation for controlled drug release and potential applications in photothermal therapy. The above functionalities, along with antibacterial activity, render the proposed approach an effective biomaterial design strategy for wound closure applications
1/f laws found in non-human music
No full textA compelling question at the intersection of physics, neuroscience, and evolutionary biology concerns the extent to which the brains of various species evolved to encode regularities of the physical world. It would be parsimonious and adaptive, for example, for brains to evolve an innate understanding of gravity and the laws of motion, and to be able to detect, auditorily, those patterns of noises that ambulatory creatures make when moving about the world. One such physical regularity of the world is fractal structure, generally characterized by power-law correlations or 1/f β spectral distributions. Such laws are found broadly in nature and human artifacts, from noise in physical systems, to coastline topography (e.g., the Richardson effect), to neuronal spike patterns. These distributions have also been found to hold for the rhythm and power spectral density of a wide array of human music, suggesting that human music incorporates regularities of the physical world that our species evolved to recognize and produce. Here we show for the first time that 1/fβ laws also govern the spectral density of a wide range of animal vocalizations (music), from songbirds, to whales, to howling wolves. We discovered this 1/fβ power-law distribution in the vocalizations within all of the 17 diverse species examined. Our results demonstrate that such power laws are prevalent in the animal kingdom, evidence that their brains have evolved a sensitivity to them as an aid in processing sensory features of the natural world