•Bennu most likely came from a low albedo asteroid family in inner main belt.•We modeled the dynamical evolution of candidate source family members.•Semimajor axis distribution of ancient families ...reproduced with stochastic YORP model.•Probable Bennu source families are New Polana (70%, +8/−4%) and Eulalia (30%, +4/−8%).•Most low albedo km-sized NEOs on Earth-like orbits come from these two families.
Asteroid (101955) Bennu, the target of NASA’s OSIRIS-REx sample return mission, is a D≈0.5km diameter low albedo near-Earth object. It has a spectral signature consistent with primitive carbonaceous chondrites, and an orbit similar to that of the Earth. A plausible evolution scenario for Bennu is that it migrated inward across the inner main belt from a low albedo family by Yarkovsky thermal forces over many hundreds of Myr. Eventually, it entered a resonance that took it into the terrestrial planet region, where a combination of planetary encounters and resonances took it to its current orbit over a few Myr to tens of Myr. When it departed the main belt, Bennu probably had an eccentricity 0.1<e<0.2 and an inclination 1°<i<6°. Several low albedo families have the appropriate dynamical, color, albedo, and broad spectral characteristics to produce Bennu: Clarissa, Erigone, Eulalia, New Polana, and Sulamitis.
Here we used a suite of numerical simulations to determine the ages of the families above, how Bennu reached its current orbit, and the most probable source family for Bennu. Specifically, we tracked test Bennu-like asteroids evolving in semimajor axis by the coupled Yarkovsky/YORP effects, incorporating a new formalism for how YORP torques modify the spin vector evolution of small asteroids. Using results and insights provided by Statler (Statler, T.S. 2009. Icarus 202, 502–513), we assumed that modest shape changes to asteroids, produced by a variety of processes (e.g., crater formation, changes to asteroid rotational angular momentum by YORP), caused the test asteroids’ spin rates, but not their obliquities, to undergo a random walk. This “stochastic YORP” mechanism slows down how often asteroids reach YORP endstates (i.e., spinning up so fast that the asteroid sheds mass, spinning down so much the asteroid enters into a tumbling rotation state). This new model allowed us to reproduce the semimajor axis distribution of observed family members from Clarissa, Erigone, Eulalia, New Polana, and Sulamitis. In the process, we derived model family formation ages of ∼60Myr old, 130±30Myr old, 830-100+370Myr old, 1400±150Myr old, and200±40Myr, respectively.
Next, using a Monte-Carlo code to track millions of test asteroids from each of the families above to main belt escape routes capable of producing Bennu-like orbits, we found the most likely parent families for Bennu are Eulalia and New Polana. On average, more than twice as many 0.5km objects from the New Polana family reach Bennu’s orbit as those from the Eulalia family. This corresponds to the New Polana and Eulalia families having a 70-4+8% and 30-8+4% probability of producing Bennu, respectively. Comparable runs to deduce the source of the Hayabusa 2 target, the low albedo 0.87km diameter near-Earth object (162173) 1999 JU3, produced similar probabilities for both families. The former Marco-Polo-R target, the 1.9km asteroid (175706) 1996 FG3, however, has a 85-83+4% probability of coming from the Eulalia family and a 15-4+83% probability of coming from the New Polana family. The reason for this switch is that 1996 FG3 may have been part of Yarkovsky/YORP-produced wave of like-sized bodies that is only now reaching the terrestrial planet region. We suggest that the top-like shape of Bennu is a byproduct of mass wasting and/or mass shedding events produced by YORP spin up during its long journey across the inner main belt.
Abstract We present a detailed study of the observational biases of the DECam Ecliptic Exploration Project’s B1 data release and survey simulation software that enables direct statistical comparisons ...between models and our data. We inject a synthetic population of objects into the images, and then subsequently recover them in the same processing as our real detections. This enables us to characterize the survey’s completeness as a function of apparent magnitudes and on-sky rates of motion. We study the statistically optimal functional form for the magnitude, and develop a methodology that can estimate the magnitude and rate efficiencies for all survey’s pointing groups simultaneously. We have determined that our peak completeness is on average 80% in each pointing group, and our magnitude drops to 25% of this value at m 25 = 26.22. We describe the freely available survey simulation software and its methodology. We conclude by using it to infer that our effective search area for objects at 40 au is 14.8 deg 2 , and that our lack of dynamically cold distant objects means that there at most 8 × 10 3 objects with 60 < a < 80 au and absolute magnitudes H ≤ 8.
Abstract We present the first set of trans-Neptunian objects (TNOs) observed on multiple nights in data taken from the DECam Ecliptic Exploration Project. Of these 110 TNOs, 105 do not coincide with ...previously known TNOs and appear to be new discoveries. Each individual detection for our objects resulted from a digital tracking search at TNO rates of motion, using two-to-four-hour exposure sets, and the detections were subsequently linked across multiple observing seasons. This procedure allows us to find objects with magnitudes m VR ≈ 26. The object discovery processing also included a comprehensive population of objects injected into the images, with a recovery and linking rate of at least 94%. The final orbits were obtained using a specialized orbit-fitting procedure that accounts for the positional errors derived from the digital tracking procedure. Our results include robust orbits and magnitudes for classical TNOs with absolute magnitudes H ∼ 10, as well as a dynamically detached object found at 76 au (semimajor axis a ≈ 77 au). We find a disagreement between our population of classical TNOs and the CFEPS-L7 three-component model for the Kuiper Belt.
Non-invasive markers of liver fibrosis are urgently required, especially for use in non-specialist settings. The aim of this study was to identify novel serum biomarkers of advanced fibrosis.
We ...performed an unbiased screen of 120 serum analytes including cytokines, chemokines and proteases in 70 patients (35 without fibrosis, 35 with cirrhosis on biopsy), and selected a panel of 44 candidate biomarkers, which were subsequently measured in a mixed-etiology cohort of 432 patients with known serum HA, PIIINP and TIMP1 (which comprise the validated Enhanced Liver Fibrosis (ELF) test). Multivariate logistic regression modelling was used to generate models for the prediction of advanced or significant fibrosis (METAVIR ≥F3 and ≥F2, respectively); in addition to identifying biomarkers of disease activity and steatohepatitis.
Seventeen analytes were significantly differentially expressed between patients with no advanced fibrosis and patients with advanced fibrosis, the most significant being hyaluronic acid (HA) and matrix metalloproteinase (MMP) 7 (p = 2.9E-41 and p = 1.0E-26, respectively). The optimal model for the prediction of advanced fibrosis comprised HA, MMP7, MMP1, alphafetoprotein (AFP) and the AST to platelet ratio index (APRI). We demonstrate enhanced diagnostic accuracy (AUROC = 0.938) compared to a model comprising HA, PIIINP and TIMP1 alone (ELF) (AUROC = 0.898, p<0.0001, De Long's test).
We have identified novel serum biomarkers of advanced liver fibrosis, which have the potential to enhance the diagnostic accuracy of established biomarkers. Our data suggest MMP7 is a valuable indicator of advanced fibrosis and may play a role in liver fibrogenesis.
Inflammatory bowel disease (IBD), comprising Crohn disease and ulcerative colitis, affects 1 to 3 million people in the United States. Telemedicine has shown promise in IBD. The objective of this ...study, telemedicine for patients with IBD (TELE-IBD), was to compare disease activity and quality of life (QoL) in a 1-year randomized clinical trial of IBD patients receiving telemedicine versus standard care. Treatment groups experienced improvements in disease activity and QoL, but there were no significant differences between groups. Study adherence to the text-based intervention was less than 80%, the targeted goal.
To understand adherence to remote monitoring, the goal of this qualitative assessment was to obtain TELE-IBD trial participants' perceptions, including their recommendations for future monitoring.
In this study, patients attending 3 tertiary referral centers with worsening IBD symptoms in the previous 2 years were eligible for randomization to remote monitoring via SMS text messages (short message service, SMS) every other week, weekly, or standard care. Participants (n=348) were evenly enrolled in the treatment groups, and 259 (74.4%) completed the study. For this study, a purposive sample of adherent (N=15) and nonadherent (N=14) patients was drawn from the TELE-IBD trial population. Adherence was defined as the completion of 80% (278/348) or more of the weekly or every other week self-assessments. Semistructured interviews conducted by phone surveyed (1) the strengths and benefits of TELE-IBD, (2) challenges associated with using TELE-IBD, and (3) how to improve the TELE-IBD intervention. Interviews were recorded, professionally transcribed, and coded based on a priori concepts and emergent themes with the aid of ATLAS.ti, version.7 qualitative data analysis software.
Participants' discussions centered on 3 elements of the intervention: (1) self-assessment questions, (2) action plans, and (3) educational messages. Participants also commented on text-based platform, depression and adherence, TELE-IBD system in place of office visit, and their recommendations for future TELE-IBD systems. Adherent and nonadherent participants prefer a flexible system that is personalized, including targeted education messages, and they perceive the intervention as effective in facilitating IBD self-management.
Participants identified clear benefits to the TELE-IBD system, including obtaining a better understanding of the disease process, monitoring their symptoms, and feeling connected to their health care provider. Participants' perceptions obtained in this qualitative study will assist in improving the TELE-IBD system to be more responsive to patients with IBD.
We manually mapped particles ranging in longest axis from 0.3 cm to 95 m on (101955) Bennu for the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer ...(OSIRIS-REx) asteroid sample return mission. This enabled the mission to identify candidate sample collection sites and shed light on the processes that have shaped the surface of this rubble-pile asteroid. Building on a global survey of particles, we used higher-resolution data from regional observations to calculate particle size-frequency distributions (PSFDs) and assess the viability of four candidate sites for sample collection (presence of unobstructed particles ≤ 2 cm). The four candidate sites have common characteristics: each is situated within a crater with a relative abundance of sampleable material. Their PSFDs, however, indicate that each site has experienced different geologic processing. The PSFD power-law slopes range from −3.0 ± 0.2 to −2.3 ± 0.1 across the four sites, based on images with a 0.01-m pixel scale. These values are consistent with, or shallower than, the global survey measurements. At one site, Osprey, the particle packing density appears to reach geometric saturation. We evaluate the uncertainty in these measurements and discuss their implications for other remotely sensed and mapped particles, and their importance to OSIRIS-REx sampling operations.
NASA’s first asteroid sample return mission, OSIRIS-REx, collected a sample from the surface of near-Earth asteroid Bennu in October 2020 and will deliver it to Earth in September 2023. Selecting a ...sample collection site on Bennu’s surface was challenging due to the surprising lack of large ponded deposits of regolith particles exclusively fine enough (≤ 2 cm diameter) to be ingested by the spacecraft’s Touch-and-Go Sample Acquisition Mechanism (TAGSAM). Here we describe the Sampleability Map of Bennu, which was constructed to aid in the selection of candidate sampling sites and to estimate the probability of collecting sufficient sample. “Sampleability” is a numeric score that expresses the compatibility of a given area’s surface properties with the sampling mechanism. The algorithm that determines sampleability is a best fit functional form to an extensive suite of laboratory testing outcomes tracking the TAGSAM performance as a function of four observable properties of the target asteroid. The algorithm and testing were designed to measure and subsequently predict TAGSAM collection amounts as a function of the minimum particle size, maximum particle size, particle size frequency distribution, and the tilt of the TAGSAM head off the surface. The sampleability algorithm operated at two general scales, consistent with the resolution and coverage of data collected during the mission. The first scale was global and evaluated nearly the full surface. Due to Bennu’s unexpected boulder coverage and lack of ponded
regolith deposits, the global sampleability efforts relied heavily on additional strategies to find and characterize regions of interest based on quantifying and avoiding areas heavily covered by material too large to be collected. The second scale was site-specific and used higher-resolution data to predict collected mass at a given contact location. The rigorous sampleability assessments gave the mission confidence to select the best possible sample collection site and directly enabled successful collection of hundreds of grams of material.
Archaeal family-D DNA polymerases (Pol-D) comprise a small (DP1) proofreading subunit and a large (DP2) polymerase subunit. Pol-D is one of the least studied polymerase families, and this publication ...investigates the enzyme from Archaeoglobus fulgidus (Afu Pol-D). The C-terminal region of DP2 contains two conserved cysteine clusters, and their roles are investigated using site-directed mutagenesis. The cluster nearest the C terminus is essential for polymerase activity, and the cysteines are shown to serve as ligands for a single, critical Zn2+ ion. The cysteines farthest from the C terminal were not required for activity, and a role for these amino acids has yet to be defined. Additionally, it is shown that Afu Pol-D activity is slowed by the template strand hypoxanthine, extending previous results that demonstrated inhibition by uracil. Hypoxanthine was a weaker inhibitor than uracil. Investigations with isolated DP2, which has a measurable polymerase activity, localised the deaminated base binding site to this subunit. Uracil and hypoxanthine slowed Afu Pol-D “in trans”, that is, a copied DNA strand could be inhibited by a deaminated base in the alternate strand of a replication fork. The error rate of Afu Pol-D, measured in vitro, was 0.24×10−5, typical for a polymerase that has been proposed to carry out genome replication in the Archaea. Deleting the 3′–5′ proofreading exonuclease activity reduced fidelity twofold. The results presented in this publication considerably increase our knowledge of Pol-D.
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•Archaeal DNA Polymerase-D binds Zn, this is essential for activity.•Archaeal DNA Polymerase-D is inhibited by uracil and hypoxanthine.•Inhibition by deaminated bases occurs both in cis and in trans.•Deaminated bases are sensed by the large (polymerase) subunit.•Polymerase-D has high fidelity, compatible with genome replication.
Recessive mutations in diacylglycerol kinase epsilon (DGKE) display genetic pleiotropy, with pathological features reported as either thrombotic microangiopathy or membranoproliferative ...glomerulonephritis (MPGN), and clinical features of atypical hemolytic uremic syndrome (aHUS), nephrotic syndrome or both. Pathophysiological mechanisms and optimal management strategies have not yet been defined. In prospective and retrospective studies of aHUS referred to the United Kingdom National aHUS service and prospective studies of MPGN referred to the National Registry of Rare Kidney Diseases for MPGN we defined the incidence of DGKE aHUS as 0.009/million/year and so-called DGKE MPGN as 0.006/million/year, giving a combined incidence of 0.015/million/year. Here, we describe a cohort of sixteen individuals with DGKE nephropathy. One presented with isolated nephrotic syndrome. Analysis of pathological features reveals that DGKE mutations give an MPGN-like appearance to different extents, with but more often without changes in arterioles or arteries. In 15 patients presenting with aHUS, ten had concurrent substantial proteinuria. Identified triggering events were rare but coexistent developmental disorders were seen in six. Nine with aHUS experienced at least one relapse, although in only one did a relapse of aHUS occur after age five years. Persistent proteinuria was seen in the majority of cases. Only two individuals have reached end stage renal disease, 20 years after the initial presentation, and in one, renal transplantation was successfully undertaken without relapse. Six individuals received eculizumab. Relapses on treatment occurred in one individual. In four individuals eculizumab was withdrawn, with one spontaneously resolving aHUS relapse occurring. Thus we suggest that DGKE-mediated aHUS is eculizumab non-responsive and that in individuals who currently receive eculizumab therapy it can be safely withdrawn. This has important patient safety and economic implications.
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