Remnant Core Research Articles

The Evaporating Massive Embedded Stellar Cluster IRS 13 Close to Sgr A*. II. Kinematic Structure

The existence of two distinct and apparently unrelated populations of dusty stellar objects in the Nuclear Stellar Cluster of the Milky Way, namely IRS 13 and the S-cluster, are potentially prone to a general process describing the star formation history in the Galactic center (GC). The former cluster is thought to be entangled in the clockwise and counterclockwise disks, a large-scale stellar distribution revealed by the analysis of stars at different distances from Sgr A*, the supermassive black hole in the GC. Recently, this large-scale distribution was reported to exhibit a multidisk structure with at least four components. Motivated by this finding, we revisit the anisotropic IRS 13 cluster and find strong evidence for a disk-like structure. An examination of about 50 individual stellar orbits reveals a new structure that does not follow any trend known in the literature. Furthermore, we investigate the possibility of an inspiral cluster undergoing star formation processes, as proposed by several authors. Using a simplified N-body simulation to reproduce our observational results, we conclude that, under certain conditions, a massive cluster can migrate from the Circum Nuclear Disk toward the inner parsec. Based on this classification, we revisit the large-scale NACO Very Large Telescope (VLT) observations of IRS 13 and find evidence for a separation of the cluster into a gravitationally stable core remnant and a dissipating part. With the velocity-resolved H30α line and the broadband spectral energy distribution of IRS 13 E3, we provide tentative support for the existence of an intermediate-mass black hole of ∼3 × 104 M ⊙ surrounded by a hot gaseous stream.

Fallback Rates in Partial Tidal Disruptions of White Dwarfs by Intermediate-mass Black Holes

The fallback rate of debris after the partial tidal disruption of a star by an intermediate-mass black hole (IMBH) might provide important signatures of such black holes rather than supermassive ones. Here using smoothed particle hydrodynamics methods, we provide a comprehensive numerical analysis of this phenomenon. We perform numerical simulations of single partial tidal disruptions of solar-mass white dwarfs in parabolic orbits, with a nonspinning 103 M ⊙ IMBH for various values of the impact parameter, and determine the core mass fractions and fallback rates of debris into the IMBH. For supermassive black holes, in full disruption processes, it is known that the late-time fallback rate follows a power law t −5/3, whereas for partial disruptions, such a rate has recently been conjectured to saturate at a steeper power law t −9/4, independent of the mass of the remnant core. We show here that for IMBHs, partial disruptions significantly alter this conclusion. That is, the fallback rate at late times does not asymptote to a t −9/4 power law, and this rate is also a strong function of the core mass. We derive a robust formula for the late-time fallback rate as a function of the core mass fraction, which is independent of the mass of the white dwarf, as we verify numerically by varying it.

A Post‐Launch Summary of the Science of NASA's Psyche Mission

AbstractAstronomical observations indicate that asteroid (16) Psyche is a large, high‐density (likely >3,400 kg·m−3), metal‐rich (30–55 vol. %) asteroid. Psyche may be remnant core material or it could be a primordial, undifferentiated metal‐rich object. We discuss the science objectives of the upcoming Psyche mission, which will employ three instruments (the Magnetometer, Multispectral Imager, and Gamma‐Ray and Neutron Spectrometer) and will use Doppler tracking of the spacecraft to explore the asteroid. This mission will shed light on the nature and origins of metal‐rich objects in the solar system and beyond, including the cores of the terrestrial planets.

Measuring the surface abundance of iron and nickel on the asteroid (16) Psyche in the presence of large solar particle events

This work investigates a novel signature for measuring the Ni/Fe ratio on the asteroid (16) Psyche that is robust against interference from large Solar Particle Events. NASA's Psyche mission launched on October 13th, 2023, and is headed to investigate this M-type asteroid. A primary science requirement for the Psyche gamma-ray spectrometer is to measure the absolute surface abundance of Ni and Fe. In particular, the Ni/Fe ratio will help test the hypothesis that (16) Psyche is a metal-rich body, possibly a remnant core from a failed planetesimal. However, Solar Particle Events can activate iron in the spacecraft, as well as the body of Psyche itself, disrupting the measurement of the surface abundance of iron for six months or more. Such an event happened during NASA's MESSENGER mission in orbit around Mercury on June 4, 2011, precluding further mapping of iron for the remainder of the mission. A similar event at Psyche could adversely affect mission science goals and/or prolong operation. Given the expected high abundance of Fe at Psyche, this paper proposes an alternative signature that relies on gamma rays from 54Fe rather than 56Fe. Although 54Fe has a lower natural abundance than 56Fe (5.8% vs 91.7%, respectively), 54Fe is much less susceptible to interference from activation and would allow measurements of the surface abundance of iron to resume within days after a large Solar Particle Event. In addition, 58Ni is shown not to be susceptible to interference from activation, thus making the 58Ni/54Fe ratio a robust alternative signature in the presence of Solar Particle Events.

Tidal disruption of white dwarfs in a modified gravity theory with SPH

Abstract Low energy imprints of modifications to general relativity are often found in pressure balance equations inside stars. These modifications are then amenable to tests via astrophysical phenomena, using observational effects in stellar astrophysics that crucially depend on such equations. One such effect is tidal disruption of stars in the vicinity of black holes. In this paper, using a numerical scheme modelled with smoothed particle hydrodynamics, we study real time tidal disruption of a class of white dwarfs by intermediate-mass black holes, in the low energy limit of a theory of modified gravity that alters the internal physics of white dwarfs, namely the Eddington inspired Born-Infeld theory. In this single parameter extension of general relativity, the mass-radius relation of white dwarfs as well as their tidal disruption radius depend on the modified gravity parameter, and these capture the effect of modifications to general relativity. Our numerical simulations incorporating these show that departure from general relativity in these scenarios might be observationally significant, and should therefore be contrasted with data. In particular, we study observationally relevant physical quantities, i.e., tidal kick velocity and trajectory deviation of the remnant core and fallback rates of the tidal debris in this theory and compare them to the Newtonian limit of general relativity. We also comment on the qualitative differences between the modified gravity theory and one with stellar rotation.

Tidal debris from Omega Centauri discovered with unsupervised machine learning

ABSTRACT The gravitational interactions between the Milky Way and in-falling satellites offer a wealth of information about the formation and evolution of our Galaxy. In this paper, we explore the high-dimensionality of the GALAH DR3 plus Gaia eDR3 data set to identify new tidally stripped candidate stars of the nearby star cluster Omega Centauri ($\omega \, \mathrm{Cen}$). We investigate both the chemical and dynamical parameter space simultaneously, and identify cluster candidates that are spatially separated from the main cluster body, in regions where contamination by halo field stars is high. Most notably, we find candidates for $\omega \, \mathrm{Cen}$ scattered in the halo extending to more than 50° away from the main body of the cluster. Using a grid of simulated streams generated with $\omega \, \mathrm{Cen}$-like orbital properties, we then compare the on sky distribution of these candidates to the models. The results suggest that if $\omega \, \mathrm{Cen}$ had a similar initial mass as its present day mass, then we can place a lower limit on its time of accretion at tacc > 7 Gyr ago. Alternatively, if the initial stellar mass was significantly larger, as would be expected if $\omega \, \mathrm{Cen}$ is the remnant core of a dwarf Galaxy, then we can constrain the accretion time to tacc > 4 Gyr ago. Taken together, these results are consistent with the scenario that $\omega \, \mathrm{Cen}$ is the remnant core of a disrupted dwarf galaxy.

The (in)visibility of lost wax casting moulds in the archaeological record: observations from an archaeological experiment

Apart from mould and core remnants attached to metal objects from the Chalcolithic Southern Levant (ca. 4500–3800 BCE), production remains of early lost wax casting are seemingly invisible in the archaeological record. An experiment using reproduced casting moulds was performed to simulate the Chalcolithic processes to investigate whether the moulds might have deteriorated to an unrecognisable state after the casting process. Results from previous studies on mould remains attached to metal objects were complemented with ethnographical accounts for the experimental set-up. The moulds were prepared from local clays already in use during the Chalcolithic. Petrography, simple alteration tests, and general technological considerations reveal that preservation may be poor but is still visible to the naked eye. The preservation of multi-layered fragments is crucial, despite their friable or brittle state after casting. A further, previously unmentioned, clear indication of lost wax casting moulds may be the combination of vegetal temper with mineral/rock temper in their clay paste. This composition derives purely from technological considerations and is independent of depositional and post-depositional processes.

The evolving cluster cores: Putting together the pieces of the puzzle

Context. In this work we address the issue of whether the division of clusters in cool cores (CCs) and non-cool cores (NCCs) is due to a primordial difference or to how clusters evolve across cosmic time. Aims. Our first goal is to establish if spectra from the central regions of a subclass of NCCs known as cool core remnants (CCRs) are consistent with having a small but significant amount of short cooling time gas, thereby allowing a transformation to CC systems on a timescale of a giga year. Our second goal is to determine if low ionization Fe lines emitted from this residual cool gas will be detectable by the calorimeters that will fly on board XRISM and Athena. Methods. We performed a spectral analysis of CCR systems with a multi temperature model and, assuming the different components to be in pressure equilibrium with one another, derived entropy and cooling time distributions for the X-ray emitting gas. Results. We find that in most of our systems, the spectral model allows for a fraction of low entropy, short cooling time gas with a mass that is comparable to the one in CC systems. Moreover, simulations show that future spectrometers on board XRISM and Athena will have the power to directly resolve emission lines from the low temperature gas, thereby providing incontrovertible evidence for its presence. Conclusions. Within the scenario that we have explored, the constant fraction of CCs measured across cosmic time emerges from a dynamical equilibrium where CCs transformed in NCCs through mergers are balanced by NCCs that revert to CCs. Furthermore, CCs and NCCs should not be viewed as distinct sub classes, but as “states” between which clusters can move.

Binary neutron star merger simulations with neutrino transport and turbulent viscosity: impact of different schemes and grid resolution

ABSTRACT We present a systematic numerical relativity study of the impact of different physics input and grid resolution in binary neutron star mergers. We compare simulations employing a neutrino leakage scheme, leakage plus M0 scheme, the M1 transport scheme, and pure hydrodynamics. Additionally, we examine the effect of a sub-grid scheme for turbulent viscosity. We find that the overall dynamics and thermodynamics of the remnant core are robust, implying that the maximum remnant density could be inferred from gravitational wave observations. Black hole collapse instead depends significantly on viscosity and grid resolution. Differently from recent work, we identify possible signatures of neutrino effects in the gravitational waves only at the highest resolutions considered; new high-resolution simulations will be thus required to build accurate gravitational wave templates to observe these effects. Different neutrino transport schemes impact significantly mass, geometry, and composition of the remnant’s disc and ejecta; M1 simulations show systematically larger proton fractions, reaching maximum values larger than 0.4. r-process nucleosynthesis yields reflect the different ejecta compositions; they are in agreement and reproduce residual solar abundances only if M0 or M1 neutrino transport schemes are adopted. We compute kilonova light curves using spherically-symmetric radiation-hydrodynamics evolutions up to 15 d post-merger, finding that they are mostly sensitive to the ejecta mass and electron fraction; accounting for multiple ejecta components appears necessary for reliable light curve predictions. We conclude that advanced neutrino schemes and resolutions higher than current standards are essential for robust long-term evolutions and detailed astrophysical predictions.

Defining priority areas for conservation of poorly known species: A case study of the endemic Brazilian three-banded armadillo

Abstract Conservation of poorly known species is challenging as lack of knowledge on their specific requirements may hamper effective strategies. Here, by integrating biogeographical and landscape analyses, we show that informed actions can be delineated for species with limited presence-only data available. We combine species distribution and connectivity models with temporal land cover changes to define priority areas for conservation of the endemic Brazilian three-banded armadillo, one of the most threatened xenarthrans that was once considered extinct in the wild. We revealed that areas of savanna and grassland are the most suitable habitats for the species and that uplands in the Caatinga ecoregion have a greater likelihood for dispersal. The few remnant armadillo populations are spatially associated with core areas of natural vegetation remnants. Worrisomely, 76% of natural core areas were lost in the past 30 years, mirroring the species’ severe population decline. Preserving the remnant core natural areas should be a high priority to ensure the species’ survival. We highlight key areas for proactive and reactive conservation actions for the three-banded armadillo that will benefit other threatened sympatric species. Our integrative framework provides a set of valuable information for guided conservation management that can be replicated for other poorly known species.

Mirabegron-induced brown fat activation does not exacerbate atherosclerosis in mice with a functional hepatic ApoE-LDLR pathway

Activation of brown adipose tissue (BAT) with the β3-adrenergic receptor agonist CL316,243 protects mice from atherosclerosis development, and the presence of metabolically active BAT is associated with cardiometabolic health in humans. In contrast, exposure to cold or treatment with the clinically used β3-adrenergic receptor agonist mirabegron to activate BAT exacerbates atherosclerosis in apolipoprotein E (ApoE)- and low-density lipoprotein receptor (LDLR)-deficient mice, both lacking a functional ApoE-LDLR pathway crucial for lipoprotein remnant clearance. We, therefore, investigated the effects of mirabegron treatment on dyslipidemia and atherosclerosis development in APOE*3-Leiden.CETP mice, a humanized lipoprotein metabolism model with a functional ApoE-LDLR clearance pathway. Mirabegron activated BAT and induced white adipose tissue (WAT) browning, accompanied by selectively increased fat oxidation and attenuated fat mass gain. Mirabegron increased the uptake of fatty acids derived from triglyceride (TG)-rich lipoproteins by BAT and WAT, which was coupled to increased hepatic uptake of the generated cholesterol-enriched core remnants. Mirabegron also promoted hepatic very low-density lipoprotein (VLDL) production, likely due to an increased flux of fatty acids from WAT to the liver, and resulted in transient elevation in plasma TG levels followed by a substantial decrease in plasma TGs. These effects led to a trend toward lower plasma cholesterol levels and reduced atherosclerosis. We conclude that BAT activation by mirabegron leads to substantial metabolic benefits in APOE*3-Leiden.CETP mice, and mirabegron treatment is certainly not atherogenic. These data underscore the importance of the choice of experimental models when investigating the effect of BAT activation on lipoprotein metabolism and atherosclerosis.

Angular-momentum Transport in Proto-neutron Stars and the Fate of Neutron Star Merger Remnants

Both the core collapse of rotating massive stars, and the coalescence of neutron star (NS) binaries result in the formation of a hot, differentially rotating NS remnant. The timescales over which differential rotation is removed by internal angular-momentum transport processes (viscosity) have key implications for the remnant’s long-term stability and the NS equation of state (EOS). Guided by a nonrotating model of a cooling proto-NS, we estimate the dominant sources of viscosity using an externally imposed angular-velocity profile Ω(r). Although the magneto-rotational instability provides the dominant source of effective viscosity at large radii, convection and/or the Tayler–Spruit dynamo dominate in the core of merger remnants where dΩ/dr ≥ 0. Furthermore, the viscous timescale in the remnant core is sufficiently short that solid-body rotation will be enforced faster than matter is accreted from rotationally supported outer layers. Guided by these results, we develop a toy model for how the merger remnant core grows in mass and angular momentum due to accretion. We find that merger remnants with sufficiently massive and slowly rotating initial cores may collapse to black holes via envelope accretion, even when the total remnant mass is less than the usually considered threshold ≈1.2 M TOV for forming a stable solid-body rotating NS remnant (where M TOV is the maximum nonrotating NS mass supported by the EOS). This qualitatively new picture of the post-merger remnant evolution and stability criterion has important implications for the expected electromagnetic counterparts from binary NS mergers and for multimessenger constraints on the NS EOS.

Aging attenuates diurnal lipid uptake by brown adipose tissue.

Brown adipose tissue (BAT) contributes to cardiometabolic health by taking up glucose and lipids for oxidation, a process that displays a strong diurnal rhythm. While aging has been shown to reduce thermogenic characteristics of BAT, it is as yet unknown whether this reduction is specific to the time of day. Therefore, we assessed whole-body and BAT energy metabolism in young and middle-aged male and female C57BL/6J mice and studied the consequences for lipid metabolism in humanized APOE*3-Leiden.CETP mice (also on a C57BL/6J background). We demonstrate that in middle-aged versus young mice body temperature is lower in both male and female mice, while uptake of triglyceride (TG)-derived fatty acids (FAs) by BAT, reflecting metabolic activity, is attenuated at its peak at the onset of the dark (wakeful) phase in female mice. This coincided with delayed plasma clearance of TG-rich lipoproteins and TG-depleted lipoprotein core remnants, and elevated plasma TGs at the same time point. Furthermore, middle-aged female mice showed increased adiposity, accompanied by lipid accumulation, increased expression of genes involved in lipogenesis, and reduced expression of genes involved in fat oxidation and the intracellular clock machinery in BAT. Peak abundance of lipoprotein lipase (LPL), a crucial regulator of FA uptake, was attenuated in BAT. Our findings suggest that LPL is a potential therapeutic target for restoring diurnal metabolic BAT activity, and that efficiency of strategies targeting BAT may be improved by including time of day as an important factor.

The GALAH Survey: improving our understanding of confirmed and candidate planetary systems with large stellar surveys

ABSTRACT Pioneering photometric, astrometric, and spectroscopic surveys is helping exoplanetary scientists better constrain the fundamental properties of stars within our galaxy and the planets these stars host. In this study, we use the third data release from the stellar spectroscopic GALAH Survey, coupled with astrometric data of eDR3 from the Gaia satellite, and other data from NASA’s Exoplanet Archive, to refine our understanding of 279 confirmed and candidate exoplanet host stars and their exoplanets. This homogenously analysed data set comprises 105 confirmed exoplanets, along with 146 K2 candidates, 95 TESS Objects of Interest (TOIs), and 52 Community TOIs (CTOIs). Our analysis significantly shifts several previously (unknown) planet parameters while decreasing the uncertainties for others. Our radius estimates suggest that 35 planet candidates are more likely brown dwarfs or stellar companions due to their new radius values. We are able to refine the radii and masses of WASP-47 e, K2-106 b, and CoRoT-7 b to their most precise values yet to less than 2.3 per cent and 8.5 per cent, respectively. We also use stellar rotational values from GALAH to show that most planet candidates will have mass measurements that will be tough to obtain with current ground-based spectrographs. With GALAH’s chemical abundances, we show through chemo-kinematics that there are five planet hosts that are associated with the galaxy’s thick disc, including NGTS-4, K2-183, and K2-337. Finally, we show that there is no statistical difference between the chemical properties of hot Neptune and hot rocky exoplanet hosts, with the possibility that short-period rocky worlds might be the remnant cores of hotter, gaseous worlds.

Detecting axion dark matter through the radio signal from Omega Centauri

As a well-motivated dark matter candidate, axions can be detected through the axion-photon resonant conversion in the magnetospheres of magnetic white dwarf stars or neutron stars. In this work, we utilize Omega Centauri, which is the largest globular cluster in the Milky Way and is suggested to be the remnant core of a dwarf galaxy, to probe the axion dark matter through radio signals that originate from all the neutron stars and magnetic white dwarf stars in it. With 100 h of observation, the combination of the radio telescopes Square Kilometer Array phase 1 and Low-Frequency Array can effectively probe the parameter space of the axion-photon coupling ${g}_{a\ensuremath{\gamma}}$ up to ${10}^{\ensuremath{-}14}\ensuremath{\sim}{10}^{\ensuremath{-}15}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}1}$ for the axion mass range of $0.1\ensuremath{\sim}30\text{ }\text{ }\ensuremath{\mu}\mathrm{eV}$. Depending on the choice of neutron star evolution model, this limitation is 2 or 3.5 orders of magnitude higher than that of the single neutron star or magnetic white dwarf.

Radius and Mass Distribution of Ultra-short-period Planets

Abstract Ultra-short-period (USP) planets are an enigmatic subset of exoplanets defined by having orbital periods <1 day. It is still not understood how USP planets form, or to what degree they differ from planets with longer orbital periods. Most USP planets have radii <2 R ⊕, while planets that orbit further from their star extend to Jupiter size (>10 R ⊕). Several theories attempt to explain the formation and composition of USP planets: they could be remnant cores of larger gas giants that lost their atmospheres due to photoevaporation or Roche-lobe overflow, or they could have developed through mass accretion in the innermost part of the protoplanetary disk. The radius and mass distribution of USP planets could provide important clues to distinguish between potential formation mechanisms. In this study, we first verify and update the Kepler catalog of USP planet host star properties, incorporating new data collected by the Gaia mission where applicable. We then use the transit depths measured by Kepler to derive a radius distribution and present occurrence rates for USP planets. Using spherical and tidally distorted planet models, we then derive a mass distribution for USP planets. Comparisons between the updated USP planet mass distribution and simulated planetary systems offer further insights into the formation and evolutionary processes shaping USP planet populations.

Asteroid 16 Psyche: Shape, Features, and Global Map

Abstract We develop a shape model of asteroid 16 Psyche using observations acquired in a wide range of wavelengths: Arecibo S-band delay-Doppler imaging, Atacama Large Millimeter Array (ALMA) plane-of-sky imaging, adaptive optics (AO) images from Keck and the Very Large Telescope (VLT), and a recent stellar occultation. Our shape model has dimensions 278 (−4/+8 km) × 238(−4/+6 km) × 171 km (−1/+5 km), an effective spherical diameter D eff = 222-1/+4 km, and a spin axis (ecliptic lon, lat) of (36°, −8°) ± 2°. We survey all the features previously reported to exist, tentatively identify several new features, and produce a global map of Psyche. Using 30 calibrated radar echoes, we find Psyche’s overall radar albedo to be 0.34 ± 0.08 suggesting that the upper meter of regolith has a significant metal (i.e., Fe–Ni) content. We find four regions of enhanced or complex radar albedo, one of which correlates well with a previously identified feature on Psyche, and all of which appear to correlate with patches of relatively high optical albedo. Based on these findings, we cannot rule out a model of Psyche as a remnant core, but our preferred interpretation is that Psyche is a differentiated world with a regolith composition analogous to enstatite or CH/CB chondrites and peppered with localized regions of high metal concentrations. The most credible formation mechanism for these regions is ferrovolcanism as proposed by Johnson et al. (2020).

Quantitative Structural Characterization of Fibrinogen's αC Regions in Fibrin Monomers and Oligomers

IntroductionMolecular structural characterization of fibrinogen and fibrin provide a basis for prophylaxis and treatments of thrombotic and hemostatic disorders. The flexible C-terminal parts of fibrinogen's Aα chains (αC regions) have been shown to play a role in fibrin formation, cross-linking by factor XIIIa, fibrinolysis, etc. The αC regions comprise about ¼ of the whole molecule by mass, but, because of their extreme flexibility, their structure is missing in the X-ray crystallography of fibrinogen and fibrin fragments. Here, we used high-resolution atomic force microscopy to examine the structure of the αC regions in fibrinogen monomers and in fibrin oligomers formed at the early stages of fibrin polymerization.MethodsThe surface of freshly cleaved graphite was rendered hydrophilic with an amphiphilic hydrocarbon-glycine modifier (Klinov et al., Nanotechnology, 2007, 18, 225102). The modified surface provides favorable conditions for protein absorption and allows obtaining high-resolution imaging of single protein molecules in air. To further improve the resolution, super sharp homemade cantilevers were also used.Plasma-purified full-length human fibrinogen and fibrinogen sub-fraction I-9 lacking most of the αC regions were imaged before and after thrombin treatments. As judged from SDS-PAGE, the I-9 fibrinogen lacked the C-terminal portions of its Aα chains and contained the Aα chain core remnants from 46.5 kDa to 22.6 kDa (or ~66% to 32% of the mass of intact Aα chain). As estimated from these measurements, the sub-fraction lacks virtually all of the αC-domains (Aα392-610) and variable lengths of the αC-connector (Aα221-391). The Bβ and γ chains of the I-9 fibrinogen were intact.ResultsWe analyzed the incidence of intact αC regions, their overall shape, and measured the contour length of the αC regions in the full-length and truncated (I-9) fibrinogen variants as well as their derivatives. In addition, we compared fibrin polymerization kinetics and the final clot structures. The incidence of the αC regions was 50% in the full-length fibrinogen compared to 19% in fibrinogen I-9. In the full-length fibrinogen, we could identify compact globular C-terminal αC-domains linked to the bulk molecule via flexible filamentous αC-connectors, confirming the previously proposed structure of the αC regions. The residual αC regions in fibrinogen I-9 were significantly shorter than in the full-length fibrinogen.To see if the structure of the αC regions changed after conversion to fibrin, we compared the structures of fibrin oligomers formed from the full-length and I-9 fibrinogen variants by thrombin. Up to 80% of the potentially existing αC regions were visualized and quantified in the full-length fibrin; they were highly heterogeneous in their length and configurations. Importantly, conversion of the full-length fibrinogen to fibrin was accompanied by an increase of the incidence and length of the αC regions as well as transitions from more compact conformations, such as a globule on a string, to extended and more flexible offshoots. On the other hand, in fibrinogen I-9 more αC regions were visualized after conversion to fibrin, but the contour length and morphology of shortened αC regions did not change upon fibrin oligomerization.Concurrent dynamic turbidimetry, confocal microscopy, and scanning electron microscopy revealed that trimming of the αC regions slowed down fibrin formation, which correlated with longer protofibrils, thinner fibers, and a denser network. No structural distinctions, except for the incidence of the αC regions, were revealed in laterally aggregated protofibrils made of the full-length or I-9 fibrinogens, suggesting a pure kinetic effect of the αC regions on the fibrin architecture.ConclusionsOur results confirmed that after conversion of fibrinogen to fibrin, the αC regions become exposed, undergo partial unfolding and/or conformational elongation. However, the effects of the αC regions on fibrin formation have a kinetic nature due to reduction of the threshold length of protofibrils, leading to accelerated lateral aggregation. The final structure and macroscopic properties of fibrin clots are affected by kinetics of the earliest stages of fibrin self-assembly. Therefore, these early polymerization steps comprise a good potential therapeutic target to modulate the structure and mechanical properties of blood clots. DisclosuresNo relevant conflicts of interest to declare.

Telluride Mineralogy of the Deer Horn Au-Ag-Te-(Bi-Pb-W) Deposit, British Columbia: Implications for the Generation of Tellurides

ABSTRACTThe Deer Horn deposit, located 150 km south of Smithers in west-central British Columbia, is an Eocene polymetallic system enriched in Au-Ag-Te with lesser amounts of Bi-Pb-W; the Au and Ag are hosted in Te-bearing minerals and Ag-rich gold (Au-Ag alloy). A quartz-sulfide vein system containing the main zones of Au-Ag-Te mineralization and attendant sericite alteration occurs in the hanging wall of a local, spatially related thrust fault and is genetically related to the nearby Eocene Nanika granodiorite intrusive suite. Tellurium-bearing minerals commonly form isolated euhedral to subhedral grains or composite grains (up to 525 μm in size) of Ag-, Bi-, Pb-, and Au-rich tellurium-bearing minerals (e.g., hessite, tellurobismuthite, volynskite, altaite, and petzite). Panchromatic cathodoluminescence imaging revealed four generations of quartz. Within remnant cores of quartz I, local oscillatory zoning occurs in quartz II. Fine-grained veinlets of quartz III and IV crosscut quartz I and II, showing evidence of at least two deformation events; late-forming veinlets of calcite crosscut all generations of quartz. The tellurides and Ag-rich gold occur in stage III quartz. Three types of fluid inclusions were observed in stage III and IV quartz: (1) aqueous liquid and vapor inclusions (L-V); (2) aqueous carbonic inclusions (L-L-V); and (3) carbonic inclusions (vapor-rich). Primary fluid inclusions related to the telluride mineralization within quartz III were tested with microthermometry, along with a few primary inclusions from quartz IV. Homogenization temperatures are 130.0–240.5 °C for L-V inclusions and 268.0–336.4 °C for L-L-V inclusions. Aqueous carbonic inclusions had solid CO2 melting temperatures from –62.1 to –56.8 °C, indicating the presence of ≈1 to 30 mol.% dissolved methane in these inclusions.The Deer Horn Au-Ag-Te-(Bi-Pb-W) deposit is a reduced intrusion-related gold system characterized by sheeted veins, metal zoning, low salinity aqueous-carbonic fluids, and a genetic relationship to an Eocene granodiorite. Values of δ34S of pyrite vary from –1.6 to 1.6 per mil and are compatible with a magmatic source of sulfur.

Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code – III. ω Cen

ABSTRACT We study the multiple populations of ω Cen by using the abundances of Fe, C, N, O, Mg, Al, Si, K, Ca, and Ce from the high-resolution, high signal-to-noise (S/N > 70) spectra of 982 red giant stars observed by the SDSS-IV/APOGEE-2 survey. We find that the shape of the Al–Mg and N–C anticorrelations changes as a function of metallicity, continuous for the metal-poor groups, but bimodal (or unimodal) at high metallicities. There are four Fe populations, similarly to previous literature findings, but we find seven populations based on Fe, Al, and Mg abundances. The evolution of Al in ω Cen is compared to its evolution in the Milky Way and in five representative globular clusters. We find that the distribution of Al in metal-rich stars of ω Cen closely follows what is observed in the Galaxy. Other α-elements and C, N, O, and Ce are also compared to the Milky Way, and significantly elevated abundances are observed over what is found in the thick disc for almost all elements. However, we also find some stars with high metallicity and low [Al/Fe], suggesting that ω Cen could be the remnant core of a dwarf galaxy, but the existence of these peculiar stars needs an independent confirmation. We also confirm the increase in the sum of CNO as a function of metallicity previously reported in the literature and find that the [C/N] ratio appears to show opposite correlations between Al-poor and Al-rich stars as a function of metallicity.