Yttrium and rare earth elements (REY) in aqueous environments have been intensively studied because they record important geochemical information. For example, the cerium anomaly, measured in marine sedimentary rocks, has been widely applied as a paleoredox indicator. Marine carbonates are the main substrate used to reconstruct REY signal in paleo-oceans with the underlying assumption that REY incorporated into carbonate minerals preserve the authigenic seawater signal. However, extracting authigenic REY signals from carbonate rocks are challenging. It requires dissolving carbonate phases using acid leaching procedures without contamination from other non-carbonate phases such as Mn/Fe oxides (hydroxides), clay minerals, siliciclastic and organic phases. Multiple dissolution protocols, especially partial leaching, were proposed to eliminate potential contaminations. Yet, the efficiency lof these procedures in reducing contamination remains ambiguous. Additionally, no systematic study on how each non-carbonate phase can modify the authigenic REY signal from carbonates. First, we systematically investigated the efficiency of using ammonium acetate buffer pre-treatment to remove exchangeable ions prior to dissolution. We tested a range of concentration, pH, and reaction time of the buffer and we found that ammonium acetate of 1 M with a pH slightly < 7, and 30 mins for reaction time works best for efficiency. Second, we tested a range of acid species and molarity to dissolve common non-carbonate contamination phases including USGS standards NOD-A-1 (manganese nodule) and SBC-1 (Brush Creek shale), as well as montmorillonite, kaolinite, illite from the Clay Minerals Society. We used three batches of acetic and nitric acids with different molarity and found that both the acid species and molarity are key parameters to avoid leaching of non-carbonate phases. We observed a negative Ce anomaly during leaching of Mn nodule using acetic acid versus a positive anomaly using nitric acid suggesting that nitric acid may introduce false positive Ce anomalies into samples. We also demonstrated that it is essential to filter the leachate to prevent the later dissolution of floating particles. For instance, Mn oxides, which carry positive Ce anomalies, can overprint the carbonate REY signal because the nitric acid (i.e. 2% v/v) used during later ICP-MS analysis could dissolve tetravalent Ce. Third, we conducted a series of leaching experiments on mixed samples consisting of 80% pure modern limestone and 20% mixed pure contaminants to identify the best protocol to avoid contamination. We demonstrate that using acetic acid with a molarity lower than 0.5 M is sufficient to avoid contaminations from Mn oxides, clay minerals, and siliciclastic phases. Finally, we present a new sequential leaching protocol for calcite ( > 75% CaCO3) using two steps of ammonium acetate pre-leaching followed by three steps of 0.3 M acetic acid leaching.

In the modern ocean, U reduction and incorporation into anoxic sediments imparts a large isotopic fractionation of approximately vertical bar 0.6 parts per thousand that shifts the seawater delta U-238 value (U-238/U-235, expressed as delta U-238 per mil deviation relative to CRM-112a) relative to continental runoff. Given the long residence time of U in the modern oceans (similar to 400 kyr), the isotopic composition of carbonates (taken as a proxy for seawater) reflects the global balance between anoxic and other sinks. The U isotopic composition of open-marine carbonates has thus emerged as a proxy for reconstructing past changes in the redox state of the global ocean. A tenet of this approach is that the delta U-238 values of seawater and anoxic sediments should always be fractionated by the same amount.

We present a photometric and spectroscopic analysis of the ultraluminous and slowly evolving 03fg-like Type Ia SN 2021zny. Our observational campaign starts from similar to 5.3 h after explosion (making SN 2021zny one of the earliest observed members of its class), with dense multiwavelength coverage from a variety of ground-and space-based telescopes, and is concluded with a nebular spectrum similar to 10 months after peak brightness. SN 2021zny displayed several characteristics of its class, such as the peak brightness (M-B = -19.95 mag), the slow decline (delta m(15)(B) = 0.62 mag), the blue early-time colours, the low ejecta velocities, and the presence of significant unburned material above the photosphere. However, a fluxexcess for the first similar to 1.5 d after explosion is observed in four photometric bands, making SN 2021zny the third 03fg-like event with this distinct behaviour, while its + 313 d spectrum shows prominent [OI] lines, a very unusual characteristic of thermonuclear SNe. The early flux excess can be explained as the outcome of the interaction of the ejecta with similar to 0 . 04 M-? of H/He-poor circumstellar material at a distance of similar to 10(12) cm, while the low ionization state of the late-time spectrum re veals lo w abundances of stable iron-peak elements. All our observations are in accordance with a progenitor system of two carbon/oxygen white dwarfs that undergo a merger event, with the disrupted white dwarf ejecting carbon-rich circumstellar material prior to the primary white dwarf detonation.

The detonation of a thin (less than or similar to 0.03 M (circle dot)) helium shell (He-shell) atop a similar to 1 M (circle dot) white dwarf (WD) is a promising mechanism to explain normal Type Ia supernovae (SNe Ia), while thicker He-shells and less massive WDs may explain some recently observed peculiar SNe Ia. We present observations of SN 2020jgb, a peculiar SN Ia discovered by the Zwicky Transient Facility (ZTF). Near maximum brightness, SN 2020jgb is slightly subluminous (ZTF g-band absolute magnitude -18.7 mag less than or similar to M ( g ) less than or similar to -18.2 mag depending on the amount of host-galaxy extinction) and shows an unusually red color (0.2 mag less than or similar to g (ZTF) - r (ZTF) less than or similar to 0.4 mag) due to strong line-blanketing blueward of similar to 5000 angstrom. These properties resemble those of SN 2018byg, a peculiar SN Ia consistent with an He-shell double detonation (DDet) SN. Using detailed radiative transfer models, we show that the optical spectroscopic and photometric evolution of SN 2020jgb is broadly consistent with a similar to 0.95-1.00 M (circle dot) (C/O core + He-shell) progenitor ignited by a greater than or similar to 0.1 M (circle dot) He-shell. However, one-dimensional radiative transfer models without non-local-thermodynamic-equilibrium treatment cannot accurately characterize the line-blanketing features, making the actual shell mass uncertain. We detect a prominent absorption feature at similar to 1 mu m in the near-infrared (NIR) spectrum of SN 2020jgb, which might originate from unburnt helium in the outermost ejecta. While the sample size is limited, we find similar 1 mu m features in all the peculiar He-shell DDet candidates with NIR spectra obtained to date. SN 2020jgb is also the first peculiar He-shell DDet SN discovered in a star-forming dwarf galaxy, indisputably showing that He-shell DDet SNe occur in both star-forming and passive galaxies, consistent with the normal SN Ia population.

We present the Texas Euclid Survey for Ly alpha (TESLA), a spectroscopic survey in the 10 deg(2) of the Euclid North Ecliptic Pole (NEP) field. Using TESLA, we study how the physical properties of Lya emitters (LAEs) correlate with Lya emission to understand the escape of Ly alpha emission from galaxies at redshifts of 2-3.5. We present an analysis of 43 LAEs performed in the NEP field using early data from the TESLA survey. We use Subaru Hyper Suprime-Cam imaging in the grizy bands, Spitzer/IRAC channels 1 and 2 from the Hawaii 20 deg(2) (H20) survey, and spectra acquired by the Visible Integral-Field Replicable Unit Spectrograph (VIRUS) on the Hobby-Eberly Telescope. We perform spectral energy distribution (SED) fitting to compute the galaxy properties of 43 LAEs, and study correlations between stellar mass, star formation rate (SFR), and dust to the Lya rest-frame equivalent width (W-Ly alpha). We uncover marginal (1 sigma significance) correlations between stellar mass and W-Ly alpha, and SFR and W-Ly alpha, with a Spearman correlation coefficient of -0. 34(-.17)(+.14) and -0. 37(-.16)(+.14), respectively. We show that the WLya distribution of the 43 LAEs is consistent with being drawn from an exponential distribution with an e-folding scale of W-0 = 150 angstrom. Once complete the TESLA survey will enable the study of greater than or similar to 50,000 LAEs to explore more correlations between galaxy properties and W-Ly alpha. The large sample size will allow the construction of a predictive model for W-Ly alpha as a function of SED-derived galaxy properties, which could be used to improve Ly alpha-based constraints on reionization.

PIWI-interacting RNAs (piRNAs) silence transposons in germ cells to maintain genome stability and animal fertility. Rhino, a rapidly evolving heterochromatin protein 1 (HP1) family protein, binds Deadlock in a species-specific manner and so defines the piRNA-producing loci in the Drosophila genome. Here, we determine the crystal structures of Rhino-Deadlock complex in Drosophila melanogaster and simulans. In both species, one Rhino binds the N-terminal helix-hairpin-helix motif of one Deadlock protein through a novel interface formed by the beta-sheet in the Rhino chromoshadow domain. Disrupting the interface leads to infertility and transposon hyperactivation in flies. Our structural and functional experiments indicate that electrostatic repulsion at the interaction interface causes cross-species incompatibility between the sibling species. By determining the molecular architecture of this piRNA-producing machinery, we discover a novel HP1-partner interacting mode that is crucial to piRNA biogenesis and transposon silencing. We thus explain the cross-species incompatibility of two sibling species at the molecular level.

The heavy occupancy of transposons in the genome implies that existing organisms have survived from multiple, independent rounds of transposon invasions. However, how and which host cell types survive the initial wave of transposon invasion remain unclear. We show that the germline stem cells can initiate a robust adaptive response that rapidly endogenizes invading P element transposons by activating the DNA damage checkpoint and piRNA production. We find that temperature modulates the P element activity in germline stem cells, establishing a powerful tool to trigger transposon hyper-activation. Facing vigorous invasion, Drosophila first shut down oogenesis and induce selective apoptosis. Interestingly, a robust adaptive response occurs in ovarian stem cells through activation of the DNA damage checkpoint. Within 4 days, the hosts amplify P element-silencing piRNAs, repair DNA damage, subdue the transposon, and reinitiate oogenesis. We propose that this robust adaptive response can bestow upon organisms the ability to survive recurrent transposon invasions throughout evolution.

We use density functional theory to calculate the equilibrium isotopic fractionation factors of zirconium (Zr) in a variety of minerals including zircon, baddeleyite, Ca-catapleiite, ilmenite, geikielite, magnetite, apatite, K-feldspar, quartz, olivine, clinopyroxene, orthopyroxene, amphibole, and garnet. We also report equilibrium isotopic fractionation factors for Hf in zircons, Ca-catapleiite, and ilmenite. These calculations show that coordination environment is an important control on Zr and Hf isotopic fractionation, with minerals with Zr and Hf in low coordinations predicted to be enriched in the heavy isotopes of Zr and Hf, relative to those with Zr and Hf in high coordinations. At equilibrium, zircon, which hosts Zr and Hf in 8-fold coordination, is predicted to have low Zr-94/Zr-90 and Hf-179/Hf-177 ratios compared to silicate melt, which hosts Zr and Hf in 6-fold coordination. However, our modeling results indicate that little equilibrium isotopic fractionation for Zr is expected during magmatic differentiation and zircon crystallization. We show through isotopic transport modeling that the Zr isotopic variations that were documented in igneous rocks are likely due to diffusion-driven kinetic isotopic fractionation. The two settings where this could take place are (i) diffusion-limited crystallization of zircon (DLC model) and (ii) diffusion-triggered crystallization of zircon (DTC model) in the boundary layer created by the growth of Zr-poor minerals. Fractional crystallization of zircons enriched in light Zr isotopes by diffusion can drive residual magmas toward heavy Zr isotopic compositions. Our diffusive transport model gives the framework to interpret Zr isotope data and gain new insights into the cooling history of igneous rocks and the setting of zircon crystallization.

Serving as a host factor for human immunodeficiency virus (HIV) integration, LEDGF/p75 has been under extensive study as a potential target for therapy. However, as a highly conserved protein, its physiological function remains to be thoroughly elucidated. Here, we characterize the molecular function of dP75, the Drosophila homolog of LEDGF/p75, during oogenesis. dP75 binds to transcriptionally active chromatin with its PWWP domain. The C-terminus integrase-binding domain-containing region of dP75 physically interacts with the histone kinase Jil-1 and stabilizes it in vivo. Together with Jil-1, dP75 prevents the spreading of the heterochromatin mark-H3K9me2-onto genes required for oogenesis and piRNA production. Without dP75, ectopical silencing of these genes disrupts oogenesis, activates transposons, and causes animal sterility. We propose that dP75, the homolog of an HIV host factor in Drosophila, partners with and stabilizes Jil-1 to ensure gene expression during oogenesis by preventing ectopic heterochromatin spreading. Copyright (C) 2020, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and Genetics Society of China. Published by Elsevier Limited and Science Press. All rights reserved.

Plate subduction greatly influences the physical and chemical characteristics of Earth's surface and deep interior, yet the timing of its initiation is debated because of the paucity of exposed rocks from Earth's early history. We show that the titanium isotopic composition of orthogneisses from the Acasta Gneiss Complex spanning the Hadean to Eoarchean transition falls on two distinct magmatic differentiation trends. Hadean tonalitic gneisses show titanium isotopic compositions comparable to modern evolved tholeiitic magmas, formed by differentiation of dry parental magmas in plume settings. Younger Eoarchean granitoid gneisses have titanium isotopic compositions comparable to modern calc-alkaline magmas produced in convergent arcs. Our data therefore document a shift from tholeiitic- to calc-alkaline-style magmatism between 4.02 and 3.75 billion years (Ga) in the Slave craton.