Widespread dispersal and aging of organic carbon in shallow marginal seas

The occurrence of pre-aged organic carbon (OC) in continental margin surface sediments is a commonly observed phenomenon, yet the nature, sources, and causes of this aged OC remain largely undetermined for many continental shelf settings. Here we present the results of an extensive survey of the abundance and radiocarbon content of OC in surface sediments from the northern Chinese marginal seas. Pre-aged OC is associated with both coarser (>63 µm) and finer (<63 µm) sedimentary components; measurements on specific grain-size fractions reveal that it is especially prevalent within the 20–63 µm fraction of inner shelf sediments. We suggest that organic matter associated with this sortable silt fraction is subject to protracted entrainment in resuspension-deposition loops during which it ages, is modified, and is laterally dispersed, most likely via entrainment within benthic nepheloid layers. This finding highlights the complex dynamics and predepositional history of organic matter accumulating in continental shelf sediments, with implications for our understanding of carbon cycling on continental shelves, development of regional carbon budgets, and interpretation of sedimentary records

The AGORA High-resolution Galaxy Simulations Comparison Project. II. Isolated Disk Test

Using an isolated Milky Way-mass galaxy simulation, we compare results from nine state-of-the-art gravito-hydrodynamics codes widely used in the numerical community. We utilize the infrastructure we have built for the AGORA High-resolution Galaxy Simulations Comparison Project. This includes the common disk initial conditions, common physics models (e.g., radiative cooling and UV background by the standardized package Grackle) and common analysis toolkit yt, all of which are publicly available. Subgrid physics models such as Jeans pressure floor, star formation, supernova feedback energy, and metal production are carefully constrained across code platforms. With numerical accuracy that resolves the disk scale height, we find that the codes overall agree well with one another in many dimensions including: gas and stellar surface densities, rotation curves, velocity dispersions, density and temperature distribution functions, disk vertical heights, stellar clumps, star formation rates, and Kennicutt–Schmidt relations. Quantities such as velocity dispersions are very robust (agreement within a few tens of percent at all radii) while measures like newly formed stellar clump mass functions show more significant variation (difference by up to a factor of ~3). Systematic differences exist, for example, between mesh-based and particle-based codes in the low-density region, and between more diffusive and less diffusive schemes in the high-density tail of the density distribution. Yet intrinsic code differences are generally small compared to the variations in numerical implementations of the common subgrid physics such as supernova feedback. Our experiment reassures that, if adequately designed in accordance with our proposed common parameters, results of a modern high-resolution galaxy formation simulation are more sensitive to input physics than to intrinsic differences in numerical schemes

Boundary Work and Transactive Memory Systems in Teams: Moderating Effects of the Visibility Affordance

Individuals in work teams frequently cross boundaries across teams, often by using information and communication technologies (ICTs). The current study investigates the effects of members’ boundary work and the visibility affordance of teams’ ICTs on Transactive Memory Systems (TMS) in teams. Survey data from 212 full-time employees whose work hours were divided between multiple teams reveals that boundary spanning enhances the focal team’s TMS credibility and specialization and negatively influences TMS coordination. Additionally, boundary reinforcement positively affects TMS credibility and coordination. The visibility affordance has a direct positive impact on all three dimensions of TMS and a moderating effect for boundary reinforcement such that higher visibility overrides the positive direct effect of boundary reinforcement on TMS. These findings suggest that different types of boundary work contribute to different dimensions of TMS and that teams might consider prioritizing the use of ICTs with high visibility to enhance their TMS

Properties of the circumgalactic medium in cosmic ray-dominated galaxy haloes

We investigate the impact of cosmic rays (CRs) on the circumgalactic medium (CGM) in FIRE-2 simulations, for ultra-faint dwarf through Milky Way (MW)-mass haloes hosting star-forming (SF) galaxies. Our CR treatment includes injection by supernovae, anisotropic streaming and diffusion along magnetic field lines, and collisional and streaming losses, with constant parallel diffusivity κ∼3×10²⁹ cm² s⁻¹ chosen to match γ-ray observations. With this, CRs become more important at larger halo masses and lower redshifts, and dominate the pressure in the CGM in MW-mass haloes at z ≲ 1–2. The gas in these ‘CR-dominated’ haloes differs significantly from runs without CRs: the gas is primarily cool (a few ∼10⁴), and the cool phase is volume-filling and has a thermal pressure below that needed for virial or local thermal pressure balance. Ionization of the ‘low’ and ‘mid’ ions in this diffuse cool gas is dominated by photoionization, with O VI columns ≳10^(14.5) cm⁻² at distances ≳150kpc⁠. CR and thermal gas pressure are locally anticorrelated, maintaining total pressure balance, and the CGM gas density profile is determined by the balance of CR pressure gradients and gravity. Neglecting CRs, the same haloes are primarily warm/hot (⁠T≳10⁵) with thermal pressure balancing gravity, collisional ionization dominates, O VI columns are lower and Ne VIII higher, and the cool phase is confined to dense filaments in local thermal pressure equilibrium with the hot phase

But What About... Cosmic Rays, Magnetic Fields, Conduction, & Viscosity in Galaxy Formation

We present a suite of high-resolution cosmological simulations, using the FIRE-2 feedback physics together with explicit treatment of magnetic fields, anisotropic conduction and viscosity, and cosmic rays (CRs) injected by supernovae (including anisotropic diffusion, streaming, adiabatic, hadronic and Coulomb losses). We survey systems from ultra-faint dwarf ($M_{\ast}\sim 10^{4}\,M_{\odot}$, $M_{\rm halo}\sim 10^{9}\,M_{\odot}$) through Milky Way masses, systematically vary CR parameters (e.g. the diffusion coefficient $\kappa$ and streaming velocity), and study an ensemble of galaxy properties (masses, star formation histories, mass profiles, phase structure, morphologies). We confirm previous conclusions that magnetic fields, conduction, and viscosity on resolved ($\gtrsim 1\,$pc) scales have small effects on bulk galaxy properties. CRs have relatively weak effects on all galaxy properties studied in dwarfs ($M_{\ast} \ll 10^{10}\,M_{\odot}$, $M_{\rm halo} \lesssim 10^{11}\,M_{\odot}$), or at high redshifts ($z\gtrsim 1-2$), for any physically-reasonable parameters. However at higher masses ($M_{\rm halo} \gtrsim 10^{11}\,M_{\odot}$) and $z\lesssim 1-2$, CRs can suppress star formation by factors $\sim 2-4$, given relatively high effective diffusion coefficients $\kappa \gtrsim 3\times10^{29}\,{\rm cm^{2}\,s^{-1}}$. At lower $\kappa$, CRs take too long to escape dense star-forming gas and lose energy to hadronic collisions, producing negligible effects on galaxies and violating empirical constraints from $\gamma$-ray emission. But around $\kappa\sim 3\times10^{29}\,{\rm cm^{2}\,s^{-1}}$, CRs escape the galaxy and build up a CR-pressure-dominated halo which supports dense, cool ($T\ll 10^{6}$ K) gas that would otherwise rain onto the galaxy. CR heating (from collisional and streaming losses) is never dominant.Comment: 35 pages, 23 figures. Updated to match published (MNRAS) versio

Application of the extended P+QQ force model to N≈ZN \approx Z fp shell nuclei

To study collective motion, the extended pairing plus $QQ$ force model proposed recently is applied to $A$=46, 48 and 50 nuclei in the $fp$ shell region. Exact shell model calculations in the truncated model space $(f_{7/2},p_{3/2},p_{1/2})$ prove the usefulness of the interaction. The simple model with the pairing plus quadrupole pairing plus $QQ$ force and $J$-independent isoscalar proton-neutron force reproduces unexpectedly well observed binding energies, energy levels of collective (yrast) states and reduced $E2$ transition probabilities in $^{46}$Ti, $^{46}$V, $^{48}$V, $^{48}$Cr, $^{50}$Cr and $^{50}$Mn. The correspondence between theory and experiment is almost comparable to that attained by the full $fp$ shell model calculations with realistic effective interactions. Some predictions are made for energy levels and variations of $B(E2)$ in the yrast bands, in these nuclei. Characteristics of the interaction are investigated by comparing with the realistic effective interactions.Comment: 34 pages including 14 figure

DNA Self-Assembly of Targeted Near-Infrared-Responsive Gold Nanoparticles for Cancer Thermo-Chemotherapy

Targeted Cancer Therapy: Inspired by the ability of DNA hybridization, a targeted near-infrared (NIR) light-responsive delivery system has been developed through simple DNA self-assembly (PEG=polyethylene glycol). This DNA-based platform shows the ability of releasing therapeutics upon near-infrared irradiation, and remarkable targeted thermo- and chemotherapeutic efficacy in vitro and in vivo

Constraining Cosmic-ray Transport with Observations of the Circumgalactic Medium

Recent theoretical studies predict that the circumgalactic medium (CGM) around low-redshift, $\sim L_*$ galaxies could have substantial nonthermal pressure support in the form of cosmic rays. However, these predictions are sensitive to the specific model of cosmic-ray transport employed, which is theoretically and observationally underconstrained. In this work, we propose a novel observational constraint for calculating the lower limit of the radially-averaged, effective cosmic-ray transport rate, $\kappa_{\rm min}^{\rm eff}$. Under a wide range of assumptions (so long as cosmic rays do not lose a significant fraction of their energy in the galactic disk, regardless of whether the cosmic-ray pressure is important or not in the CGM), we demonstrate a well-defined relationship between $\kappa_{\rm min}^{\rm eff}$ and three observable galaxy properties: the total hydrogen column density, the average star formation rate, and the gas circular velocity. We use a suite of FIRE-2 galaxy simulations with a variety of cosmic-ray transport physics to demonstrate that our analytic model of $\kappa_{\rm min}^{\rm eff}$ is a robust lower limit of the true cosmic-ray transport rate. We then apply our new model to calculate $\kappa_{\rm min}^{\rm eff}$ for galaxies in the COS-Halos sample, and confirm this already reveals strong evidence for an effective transport rate which rises rapidly away from the interstellar medium to values $\kappa_{\rm min}^{\rm eff}\gtrsim 10^{30-31}\,{\rm cm}^2\,{\rm s}^{-1}$ (corresponding to anisotropic streaming velocities of $v^{\rm stream}_{\rm eff} \gtrsim 1000\,{\rm km}\,{\rm s}^{-1}$) in the diffuse CGM, at impact parameters larger than $50-100$\,kpc. We discuss how future observations can provide qualitatively new constraints in our understanding of cosmic rays in the CGM and intergalactic medium.Comment: 9 pages, 2 figures, accepted to MNRA