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DOE OSTI2020

An Experimental Feasibility Study on Applying Neutron Tomography to Encapsulated Spent Nuclear Fuel - 20050

Visual inspection makes easier to ensure the integrity and safety of spent nuclear fuel (SNF) than any classical techniques. Various classical techniques have been applied but there are no reliable methods to qualitatively and quantitatively verify spent fuel in dry storage. Thus, the present authors have developed the prototype safeguards apparatus for dry storage employing the array of He-4 gas scintillation detectors (S670E, Arktis Radiation Detectors Ltd., Switzerland), newly designed to simultaneously measure thermal and fast neutrons without any moderators. The S670E detector has a cylindrical shape with a diameter of 52 mm and active length of 600 mm (total length: 875 mm). The detector is filled by He-4 gas with an approximate pressure of 180 bar for fast neutron detection, and its inner wall is coated by Li-6 for thermal neutron detection. The scintillation lights generated via Li-6 nuclear reaction and elastic scattering are collected by 24 SiPMs linearly paired at the center of the detector. The detector delivers a TTL (Transistor-Transistor Logic) output for pulse readout and UART (Universal Asynchronous Receiver Transmitter) for device control. In order to assess feasibility of the apparatus, an experimental system has been designed, built, and optimized via computational studies. Cf-252 neutron sources and linearly arrayed detectors, working as a single detector, were occupied for this study due to the difficulties in working with SNF. The laboratory scale cask (diameter: 0.67 m, height: 1.5 m), minimized by a factor of 10 compared to the actual thickness of a commercial TN-32 cask, was also manufactured. The detector array was designed to rotate the lab-scale cask and obtain 36 image profiles at every 10 degrees. All profiles were aligned in single frame image called a sinogram, and the cross-sectional image was then fabricated by the inverse radon transform algorithm. These experiments have been repeated with different configurations and numbers of sources. Some gamma-ray sources were also measured with neutron sources in order to distinguish between neutron and gamma-ray pulses. Basically, a He-4 detector is designed to run on Linux OS so it is difficult to directly apply to Windows-based equipment widely used in S. Korea. Therefore, a new data acquisition board working on Windows OS was designed and built. The board mainly consists of FPGA (Field Programmable Gate Array) and SoC (System on Chip) for TTL pulse readout, sorting measured data, and transferring data to a user interface. In conclusion, the tomographic system at lab-scale has shown considerable potential to detect a partial or gross defect of encapsulated assemblies in dry storage. Next steps of this study will be to 1) repeatedly carry out experiments to demonstrate scientific reliability and validity, and 2) numerically integrate signals with weight factors to enhance the image quality since the suggested system based on passive interrogation method requires longer measurement time. Finally, the system will apply to a commercial dry storage phased out soon in S. Korea. (authors)

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2024

Development of Half-Sandwich Ru, Os, Rh, and Ir Complexes Bearing the Pyridine-2-ylmethanimine Bidentate Ligand Derived from 7-Chloroquinazolin-4(3H)-one with Enhanced Antiproliferative Activity

Kinesin spindle protein (KSP) inhibitors are one of the most promising anticancer agents developed in recent years. Herein, we report the synthesis of ispinesib-core pyridine derivative conjugates, which are potent KSP inhibitors, with half-sandwich complexes of ruthenium, osmium, rhodium, and iridium. Conjugation of 7-chloroquinazolin-4(3H)-one with the pyridine-2-ylmethylimine group and the organometallic moiety resulted in up to a 36-fold increased cytotoxicity with IC 50 values in the micromolar and nanomolar range also toward drug-resistant cells. All studied conjugates increased the percentage of cells in the G 2 /M phase, simultaneously decreasing the number of cells in the G 1 /G 0 phase, suggesting mitotic arrest. Additionally, ruthenium derivatives were able to generate reactive oxygen species (ROS); however, no significant influence of the organometallic moiety on KSP inhibition was observed, which suggests that conjugation of a KSP inhibitor with the organometallic moiety modulates its mechanism of action.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Materials Data on OsC8I4N3OF by Materials Project

OsC8N3OI4F crystallizes in the orthorhombic Pca2_1 space group. The structure is one-dimensional and consists of two OsC8N3OI4F ribbons oriented in the (0, 0, 1) direction. Os2- is bonded in a distorted linear geometry to one N3-, four I1-, and one F1- atom. The Os–N bond length is 1.76 Å. There are two shorter (2.69 Å) and two longer (2.80 Å) Os–I bond lengths. The Os–F bond length is 1.95 Å. There are eight inequivalent C+2.25+ sites. In the first C+2.25+ site, C+2.25+ is bonded in a distorted single-bond geometry to one C+2.25+ and one N3- atom. The C–C bond length is 1.24 Å. The C–N bond length is 1.26 Å. In the second C+2.25+ site, C+2.25+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.58 Å. In the third C+2.25+ site, C+2.25+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.58 Å. In the fourth C+2.25+ site, C+2.25+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.64 Å. In the fifth C+2.25+ site, C+2.25+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.65 Å. In the sixth C+2.25+ site, C+2.25+ is bonded in a distorted linear geometry to one C+2.25+ and one I1- atom. The C–I bond length is 1.96 Å. In the seventh C+2.25+ site, C+2.25+ is bonded in a distorted single-bond geometry to one C+2.25+ and one N3- atom. The C–C bond length is 1.27 Å. The C–N bond length is 1.25 Å. In the eighth C+2.25+ site, C+2.25+ is bonded in a bent 150 degrees geometry to one C+2.25+ and one I1- atom. The C–I bond length is 1.99 Å. There are three inequivalent N3- sites. In the first N3- site, N3- is bonded in a bent 150 degrees geometry to two C+2.25+ atoms. In the second N3- site, N3- is bonded in a linear geometry to one Os2- and one O2- atom. The N–O bond length is 1.18 Å. In the third N3- site, N3- is bonded in a 4-coordinate geometry to four C+2.25+ and one I1- atom. The N–I bond length is 3.47 Å. O2- is bonded in a single-bond geometry to one N3- atom. There are four inequivalent I1- sites. In the first I1- site, I1- is bonded in a 2-coordinate geometry to one Os2-, one C+2.25+, one N3-, and one F1- atom. The I–F bond length is 3.14 Å. In the second I1- site, I1- is bonded in a 2-coordinate geometry to one Os2- and one C+2.25+ atom. In the third I1- site, I1- is bonded in a distorted single-bond geometry to one Os2- atom. In the fourth I1- site, I1- is bonded in a distorted single-bond geometry to one Os2- atom. F1- is bonded in a single-bond geometry to one Os2- and one I1- atom.

36 MATERIALS SCIENCE↗

NASA NTRS2004

Low Abundances of Highly Siderophile Elements in the Lunar Mantle: Evidence for Prolonged Late Accretion

The highly siderophile elements (HSE: including Re, Au, Ir, Os, Ru, Pt, Pd, Rh) are strongly partitioned into metal relative to silicates. In the terrestrial planets these elements are concentrated in metallic cores. Earth s mantle has sufficiently high abundances of the HSE (~0.008 times CI abundances) that it has been hypothesized approximately 0.1-0.5% of the mass of the Earth was added following the last major interaction between the core and mantle [e.g. 1]. The additional material added to the Earth and Moon has been termed a late veneer , and the process has often been termed late accretion [2]. The timing of the dominant late accretionary period of the Earth and Moon is still poorly known. The abundances of HSE in the lunar mantle could provide important constraints on when the late veneer was added. The material that ultimately became the silicate portion of the Moon was likely stripped of most of its HSE prior to and during coalescence of the Moon. Consequently the initial lunar mantle likely had very low concentrations of the HSE. Unlike Earth, the generation of permanent lunar crust by ~4.4 Ga prevented subsequent additions of HSE to the lunar mantle via continued accretion. Thus, if a substantial portion of the late veneer was added after 4.4 Ga, the lunar mantle should have retained very low HSE concentrations. Conversely, if the late veneer was mostly added prior to 4.4 Ga, HSE abundances in the lunar mantle may be roughly similar to abundances in the terrestrial mantle.

Walker, R. J.↗

DOE OSTI2020

Materials Data on OsSeS3Cl4 by Materials Project

OsSeS3Cl4 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. there are two inequivalent Os6+ sites. In the first Os6+ site, Os6+ is bonded to three S2- and three Cl1- atoms to form edge-sharing OsS3Cl3 octahedra. There are a spread of Os–S bond distances ranging from 2.24–2.29 Å. There are a spread of Os–Cl bond distances ranging from 2.40–2.44 Å. In the second Os6+ site, Os6+ is bonded to three S2- and two Cl1- atoms to form edge-sharing OsS3Cl2 square pyramids. There are one shorter (2.24 Å) and two longer (2.27 Å) Os–S bond lengths. There are one shorter (2.42 Å) and one longer (2.46 Å) Os–Cl bond lengths. There are two inequivalent Se4+ sites. In the first Se4+ site, Se4+ is bonded in a distorted rectangular see-saw-like geometry to four Cl1- atoms. There are a spread of Se–Cl bond distances ranging from 2.20–2.84 Å. In the second Se4+ site, Se4+ is bonded in a 3-coordinate geometry to three S2- atoms. There are a spread of Se–S bond distances ranging from 2.24–2.61 Å. There are six inequivalent S2- sites. In the first S2- site, S2- is bonded in a 6-coordinate geometry to one Se4+, one S2-, and four Cl1- atoms. The S–S bond length is 2.04 Å. There are a spread of S–Cl bond distances ranging from 3.41–3.80 Å. In the second S2- site, S2- is bonded in a 2-coordinate geometry to one Se4+ and one S2- atom. The S–S bond length is 2.03 Å. In the third S2- site, S2- is bonded in a 1-coordinate geometry to one Os6+ and one S2- atom. In the fourth S2- site, S2- is bonded in a 3-coordinate geometry to two Os6+ and one Cl1- atom. The S–Cl bond length is 2.08 Å. In the fifth S2- site, S2- is bonded in a 1-coordinate geometry to one Os6+ and one S2- atom. In the sixth S2- site, S2- is bonded in a 2-coordinate geometry to two Os6+ and one Se4+ atom. There are eight inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a 1-coordinate geometry to one Os6+ and one Se4+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one Os6+ and one S2- atom. In the third Cl1- site, Cl1- is bonded in a single-bond geometry to one Os6+ atom. In the fourth Cl1- site, Cl1- is bonded in a single-bond geometry to one Os6+ atom. In the fifth Cl1- site, Cl1- is bonded in a distorted single-bond geometry to two S2- atoms. In the sixth Cl1- site, Cl1- is bonded in a single-bond geometry to one Se4+ and one S2- atom. In the seventh Cl1- site, Cl1- is bonded in a 1-coordinate geometry to one Os6+, one Se4+, and one S2- atom. In the eighth Cl1- site, Cl1- is bonded in a single-bond geometry to one Se4+ atom.

36 MATERIALS SCIENCE↗

NASA NTRS2024

Independent Scientific Review of Biological Assumptions and Planned Ultraviolet Treatment for Mars Sample Return Backward Planetary Protection

The Backward Planetary Protection Study Team (“the Study Team”), assembled by the Office of the Chief Scientist (OCS) at the request of the Office of Planetary Protection (OPP), has conducted numerous detailed discussions on the potential use of an active ultraviolet (UV) approach for minimizing or eliminating biological contamination of the exterior of the planned Orbiting Sample container (OS) of the Mars Sample Return (MSR) mission. This review of the backward planetary protection (BPP) considerations for the MSR mission focused on two key parameters that are opportunities for further process development to support implementation of planetary protection practices in meeting mission requirements. These parameters include: 1) Sub-cellular biological assumptions – should Mars missions consider self-replicating organisms only or do they need to consider non-self-replicating entities without a cellular organization such as viruses, prions, etc. and macromolecules capable of genetic information transfer, as well? 2) UV biocidal impact – what is the UV fluence in the Mars atmosphere and its associated potential biocidal credit? The assembled subject matter experts (SMEs) in the Study Team are listed in Appendix A, with a brief description of each member’s relevant expertise.

Mamta Patel Nagaraja↗

NASA NTRS2010

Chemical sensors using coated or doped carbon nanotube networks

Methods for using modified single wall carbon nanotubes ("SWCNTs") to detect presence and/or concentration of a gas component, such as a halogen (e.g., Cl.sub.2), hydrogen halides (e.g., HCl), a hydrocarbon (e.g., C.sub.nH.sub.2n+2), an alcohol, an aldehyde or a ketone, to which an unmodified SWCNT is substantially non-reactive. In a first embodiment, a connected network of SWCNTs is coated with a selected polymer, such as chlorosulfonated polyethylene, hydroxypropyl cellulose, polystyrene and/or polyvinylalcohol, and change in an electrical parameter or response value (e.g., conductance, current, voltage difference or resistance) of the coated versus uncoated SWCNT networks is analyzed. In a second embodiment, the network is doped with a transition element, such as Pd, Pt, Rh, Ir, Ru, Os and/or Au, and change in an electrical parameter value is again analyzed. The parameter change value depends monotonically, not necessarily linearly, upon concentration of the gas component. Two general algorithms are presented for estimating concentration value(s), or upper or lower concentration bounds on such values, from measured differences of response values.

Li, Jing↗

NASA NTRS2011

Coated or doped carbon nanotube network sensors as affected by environmental parameters

Li, Jing↗

DOE OSTI2020

Materials Data on K2H2OsCCl5O2 by Materials Project

K4Os2CH4O3Cl10CO crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional and consists of four formaldehyde molecules and one K4Os2CH4O3Cl10 framework. In the K4Os2CH4O3Cl10 framework, there are four inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 7-coordinate geometry to two O2- and five Cl1- atoms. There are one shorter (2.64 Å) and one longer (2.82 Å) K–O bond lengths. There are a spread of K–Cl bond distances ranging from 3.08–3.37 Å. In the second K1+ site, K1+ is bonded in a 9-coordinate geometry to nine Cl1- atoms. There are a spread of K–Cl bond distances ranging from 3.17–3.79 Å. In the third K1+ site, K1+ is bonded in a 2-coordinate geometry to two O2- and seven Cl1- atoms. There are one shorter (2.69 Å) and one longer (2.74 Å) K–O bond lengths. There are a spread of K–Cl bond distances ranging from 3.12–3.67 Å. In the fourth K1+ site, K1+ is bonded in a 10-coordinate geometry to ten Cl1- atoms. There are a spread of K–Cl bond distances ranging from 3.16–3.85 Å. There are two inequivalent Os1+ sites. In the first Os1+ site, Os1+ is bonded in a distorted square pyramidal geometry to five Cl1- atoms. There are a spread of Os–Cl bond distances ranging from 2.36–2.49 Å. In the second Os1+ site, Os1+ is bonded in a distorted square pyramidal geometry to five Cl1- atoms. There are a spread of Os–Cl bond distances ranging from 2.36–2.52 Å. C4+ is bonded in a single-bond geometry to one O2- atom. The C–O bond length is 1.17 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted water-like geometry to two K1+ and two H1+ atoms. In the second O2- site, O2- is bonded in a distorted water-like geometry to two K1+ and two H1+ atoms. In the third O2- site, O2- is bonded in a single-bond geometry to one C4+ and one Cl1- atom. The O–Cl bond length is 3.27 Å. There are ten inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a 1-coordinate geometry to three K1+ and one Os1+ atom. In the second Cl1- site, Cl1- is bonded in a 4-coordinate geometry to three K1+ and one Os1+ atom. In the third Cl1- site, Cl1- is bonded in a 4-coordinate geometry to three K1+ and one Os1+ atom. In the fourth Cl1- site, Cl1- is bonded in a 5-coordinate geometry to four K1+ and one Os1+ atom. In the fifth Cl1- site, Cl1- is bonded in a 6-coordinate geometry to four K1+, one Os1+, and one O2- atom. In the sixth Cl1- site, Cl1- is bonded in a 3-coordinate geometry to two K1+ and one Os1+ atom. In the seventh Cl1- site, Cl1- is bonded in a 1-coordinate geometry to three K1+ and one Os1+ atom. In the eighth Cl1- site, Cl1- is bonded in a 4-coordinate geometry to three K1+ and one Os1+ atom. In the ninth Cl1- site, Cl1- is bonded in a 1-coordinate geometry to four K1+ and one Os1+ atom. In the tenth Cl1- site, Cl1- is bonded in a 1-coordinate geometry to two equivalent K1+ and one Os1+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Long-lived biνo at the LHC

We examine the detection prospects for a long-lived bi ν o, a pseudo-Dirac bino which is responsible for neutrino masses, at the LHC and at dedicated long-lived particle detectors. The bi ν o arises in U(1) R -symmetric supersymmetric models where the neutrino masses are generated through higher dimensional operators in an inverse seesaw mechanism. At the LHC the bi ν o is produced through squark decays and it subsequently decays to quarks, charged leptons and missing energy via its mixing with the Standard Model neutrinos. We consider long-lived bi ν os which escape the ATLAS or CMS detectors as missing energy and decay to charged leptons inside the proposed long-lived particle detectors FASER, CODEX-b, and MATHUSLA. We find the currently allowed region in the squark-bi ν o mass parameter space by recasting most recent LHC searches for jets+. We also determine the reach of MATHUSLA, CODEX-b and FASER. We find that a large region of parameter space involving squark masses, bi ν o mass and the messenger scale can be probed with MATHUSLA, ranging from bi ν o masses of 10 GeV-2 TeV and messenger scales 10 2 - 11 TeV for a range of squark masses.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS2015

Toxicity of Mineral Dusts and a Proposed Mechanism for the Pathogenesis of Particle-Induced Lung Diseases

Humans will set foot on the moon again. The lunar surface has been bombarded for 4 billion years by micrometeoroids and cosmic radiation, creating a layer of fine dust having a potentially reactive particle surface. To investigate the impact of surface reactivity (SR) on the toxicity of particles, and in particular, lunar dust (LD), we ground 2 Apollo 14 LD samples to increase their SR and compare their toxicity with those of unground LD, TiO2 and quartz. Intratracheally instilled at 0, 1, 2.5, or 7.5 mg/rat, all dusts caused dose-dependent increases in pulmonary lesions, and enhancement of biomarkers of toxicity assessed in bronchoalveolar lavage fluids (BALF). The toxicity of LD was greater than that of TiO2 but less than that of quartz. Three LDs differed 14-fold in SR but were equally toxic; quartz had the lowest SR but was most toxic. These results show no correlation between particle SR and toxicity. Often pulmonary toxicity of a dust can be attributed to oxidative stress (OS). We further observed dose-dependent and dustcytotoxicity- dependent increases in neutrophils. The oxidative content per BALF cell was also directly proportional to both the dose and cytotoxicity of the dusts. Because neutrophils are short-lived and release of oxidative contents after they die could initiate and promote a spectrum of lesions, we postulate a general mechanism for the pathogenesis of particle-induced diseases in the lung that involves chiefly neutrophils, the source of persistent endogenous OS. This mechanism explains why one dust (e.g., quartz or nanoparticles) is more toxic than another (e.g., micrometer-sized TiO2), why dust-induced lesions progress with time, and why lung cancer occurs in rats but not in mice and hamsters exposed to the same duration and concentration of dust.

Lam, C.‐W.↗

NASA NTRS1993

Evaluation Metrics for the Paragon XP/S-15

On February 17th 1993, the Numerical Aerodynamic Simulation (NAS) facility located at the NASA Ames Research Center installed a 224 node Intel Paragon XP/S-15 system. After its installation, the Paragon was found to be in a very immature state and was unable to support a NAS users' workload, composed of a wide range of development and production activities. As a first step towards addressing this problem, we implemented a set of metrics to objectively monitor the system as operating system and hardware upgrades were installed. The metrics were designed to measure four aspects of the system that we consider essential to support our workload: availability, utilization, functionality, and performance. This report presents the metrics collected from February 1993 to August 1993. Since its installation, the Paragon availability has improved from a low of 15% uptime to a high of 80%, while its utilization has remained low. Functionality and performance have improved from merely running one of the NAS Parallel Benchmarks to running all of them faster (between 1 and 2 times) than on the iPSC/860. In spite of the progress accomplished, fundamental limitations of the Paragon operating system are restricting the Paragon from supporting the NAS workload. The maximum operating system message passing (NORMA IPC) bandwidth was measured at 11 Mbytes/s, well below the peak hardware bandwidth (175 Mbytes/s), limiting overall virtual memory and Unix services (i.e. Disk and HiPPI I/O) performance. The high NX application message passing latency (184 microns), three times than on the iPSC/860, was found to significantly degrade performance of applications relying on small message sizes. The amount of memory available for an application was found to be approximately 10 Mbytes per node, indicating that the OS is taking more space than anticipated (6 Mbytes per node).

Traversat, Bernard↗

DOE OSTI2020

Materials Data on OsN5Cl3 by Materials Project

(OsN)2N2(N2Cl)2(NCl2)2 crystallizes in the orthorhombic Pnma space group. The structure is zero-dimensional and consists of four ammonia molecules, four azanylidyneosmium molecules, four dichloramine molecules, and four N2Cl clusters. In each N2Cl cluster, N+0.20+ is bonded in a single-bond geometry to one Cl1- atom. The N–Cl bond length is 1.70 Å. Cl1- is bonded in a linear geometry to two equivalent N+0.20+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on K2H3OsN2O7 by Materials Project

(K2OsN2O7)2(H2)3 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional and consists of twelve hydrogen molecules and one K2OsN2O7 framework. In the K2OsN2O7 framework, there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of K–O bond distances ranging from 2.76–2.87 Å. In the second K1+ site, K1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of K–O bond distances ranging from 2.70–3.02 Å. Os7+ is bonded to four O2- atoms to form distorted edge-sharing OsO4 trigonal pyramids. There are a spread of Os–O bond distances ranging from 1.77–1.97 Å. There are two inequivalent N1+ sites. In the first N1+ site, N1+ is bonded in a bent 120 degrees geometry to two O2- atoms. Both N–O bond lengths are 1.26 Å. In the second N1+ site, N1+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.25 Å) and one longer (1.27 Å) N–O bond length. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a water-like geometry to two equivalent Os7+ atoms. In the second O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent K1+ and one N1+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one N1+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to two K1+ and one N1+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to two K1+ and one Os7+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to three K1+ and one N1+ atom. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to two K1+ and one Os7+ atom.

36 MATERIALS SCIENCE↗

NASA NTRS1988

Provenance of the K/T boundary layers

An array of chemical, physical and isotopic evidence indicates that an impact into oceanic crust terminated the Cretaceous Period. Approximately 1500 cu km of debris, dispersed by the impact fireball, fell out globally in marine and nonmarine environments producing a 2 to 4 mm thick layer (fireball layer). In North American locales, the fireball layer overlies a 15 to 25 mm thick layer of similar but distinct composition. This 15 to 25 mm layer (ejecta layer) may represent approximately 1000 cu km of lower energy ejecta from a nearby impact site. Isotopic and chemical evidence supports a mantle provenance for the bulk of the layers. The extraordinary REE pattern of the boundary clays was modelled as a mixture of oceanic crust, mantle, and approximately 10 percent continental material. The results are presented. If the siderophiles of the ejecta layer were derived solely from the mantle, a test may be available to see if the siderophile element anomaly of the fireball layer had an extraterrestrial origin. Radiogenic Os-187 is depleted in the mantle relative to an undifferentiated chondritic source. Os-187/Os-186 ratios of 1.049 and 1.108 were calculated for the ejecta and fireball layers, respectively.

Hildebrand, A. R.↗

DOE OSTI2021

Climate model projections from the Scenario Model Intercomparison Project (ScenarioMIP) of CMIP6

Abstract. The Scenario Model Intercomparison Project (ScenarioMIP) defines and coordinates the main set of future climate projections, based on concentration-driven simulations, within the Coupled Model Intercomparison Project phase 6 (CMIP6). This paper presents a range of its outcomes by synthesizing results from the participating global coupled Earth system models. We limit our scope to the analysis of strictly geophysical outcomes: mainly global averages and spatial patterns of change for surface air temperature and precipitation. We also compare CMIP6 projections to CMIP5 results, especially for those scenarios that were designed to provide continuity across the CMIP phases, at the same time highlighting important differences in forcing composition, as well as in results. The range of future temperature and precipitation changes by the end of the century (2081–2100) encompassing the Tier 1 experiments based on the Shared Socioeconomic Pathway (SSP) scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5) and SSP1-1.9 spans a larger range of outcomes compared to CMIP5, due to higher warming (by close to 1.5 ∘C) reached at the upper end of the 5 %–95 % envelope of the highest scenario (SSP5-8.5). This is due to both the wider range of radiative forcing that the new scenarios cover and the higher climate sensitivities in some of the new models compared to their CMIP5 predecessors. Spatial patterns of change for temperature and precipitation averaged over models and scenarios have familiar features, and an analysis of their variations confirms model structural differences to be the dominant source of uncertainty. Models also differ with respect to the size and evolution of internal variability as measured by individual models' initial condition ensemble spreads, according to a set of initial condition ensemble simulations available under SSP3-7.0. These experiments suggest a tendency for internal variability to decrease along the course of the century in this scenario, a result that will benefit from further analysis over a larger set of models. Benefits of mitigation, all else being equal in terms of societal drivers, appear clearly when comparing scenarios developed under the same SSP but to which different degrees of mitigation have been applied. It is also found that a mild overshoot in temperature of a few decades around mid-century, as represented in SSP5-3.4OS, does not affect the end outcome of temperature and precipitation changes by 2100, which return to the same levels as those reached by the gradually increasing SSP4-3.4 (not erasing the possibility, however, that other aspects of the system may not be as easily reversible). Central estimates of the time at which the ensemble means of the different scenarios reach a given warming level might be biased by the inclusion of models that have shown faster warming in the historical period than the observed. Those estimates show all scenarios reaching 1.5 ∘C of warming compared to the 1850–1900 baseline in the second half of the current decade, with the time span between slow and fast warming covering between 20 and 27 years from present. The warming level of 2 ∘C of warming is reached as early as 2039 by the ensemble mean under SSP5-8.5 but as late as the mid-2060s under SSP1-2.6. The highest warming level considered (5 ∘C) is reached by the ensemble mean only under SSP5-8.5 and not until the mid-2090s.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS2021

Climate model projections from the Scenario Model Intercomparison Project (ScenarioMIP) of CMIP6

The Scenario Model Intercomparison Project (ScenarioMIP) defines and coordinates the main set of future climate projections, based on concentration-driven simulations, within the Coupled Model Intercomparison Project phase 6 (CMIP6). This paper presents a range of its outcomes by synthesizing results from the participating global coupled Earth system models. We limit our scope to the analysis of strictly geophysical outcomes: mainly global averages and spatial patterns of change for surface air temperature and precipitation. We also compare CMIP6 projections to CMIP5 results, especially for those scenarios that were designed to provide continuity across the CMIP phases, at the same time highlighting important differences in forcing composition, as well as in results. The range of future temperature and precipitation changes by the end of the century (2081–2100) encompassing the Tier 1 experiments based on the Shared Socioeconomic Pathway (SSP) scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5) and SSP1-1.9 spans a larger range of outcomes compared to CMIP5, due to higher warming (by close to 1.5 °C) reached at the upper end of the 5 %–95 % envelope of the highest scenario (SSP5-8.5). This is due to both the wider range of radiative forcing that the new scenarios cover and the higher climate sensitivities in some of the new models compared to their CMIP5 predecessors. Spatial patterns of change for temperature and precipitation averaged over models and scenarios have familiar features, and an analysis of their variations confirms model structural differences to be the dominant source of uncertainty. Models also differ with respect to the size and evolution of internal variability as measured by individual models' initial condition ensemble spreads, according to a set of initial condition ensemble simulations available under SSP3-7.0. These experiments suggest a tendency for internal variability to decrease along the course of the century in this scenario, a result that will benefit from further analysis over a larger set of models. Benefits of mitigation, all else being equal in terms of societal drivers, appear clearly when comparing scenarios developed under the same SSP but to which different degrees of mitigation have been applied. It is also found that a mild overshoot in temperature of a few decades around mid-century, as represented in SSP5-3.4OS, does not affect the end outcome of temperature and precipitation changes by 2100, which return to the same levels as those reached by the gradually increasing SSP4-3.4 (not erasing the possibility, however, that other aspects of the system may not be as easily reversible). Central estimates of the time at which the ensemble means of the different scenarios reach a given warming level might be biased by the inclusion of models that have shown faster warming in the historical period than the observed. Those estimates show all scenarios reaching 1.5 °C of warming compared to the 1850–1900 baseline in the second half of the current decade, with the time span between slow and fast warming covering between 20 and 27 years from present. The warming level of 2 °C of warming is reached as early as 2039 by the ensemble mean under SSP5-8.5 but as late as the mid-2060s under SSP1-2.6. The highest warming level considered (5 °C) is reached by the ensemble mean only under SSP5-8.5 and not until the mid-2090s.d-2090s.

Scenario Model Intercomparison Project (ScenarioMI↗

NASA NTRS1997

Constraints on the Nature and Distribution of Iridium Host Phases at the Cretaceous-Tertiary Boundary: Implications for Projectile Identity and dispersal on impact

Among Cretaceous-Tertiary boundary sites worldwide, variations in the concentrations and ratios of elements commonly enriched in meteorites complicate traditional geochemical attempts at impactor identification. Yet they may provide constraints on the physical and chemical processes associated with large-body disruption and dispersal, as well as with diagenesis of projectile components. To this end, we continue our efforts to identify the mineral host-phases of projectile-derived elements, particularly for Ir, and to document their partitioning between crater deposits and ejecta resulting from the Chicxulub basin-forming impact. Building on earlier work, we used INAA to measure Ir concentrations in successively smaller splits of finely powdered impact melt breccia from the Chicxulub Crater in Mexico (sample Y6Nl9-R(b)), and K/T boundary fish clay from Stevns Klint, Denmark (sample FC-1, split from 40 kg of homogenized material intended as an analytical standard). Results for the Chicxulub sample show a heterogeneous Ir distribution and document that at least five discrete Ir-bearing host phases were isolated in subsequent splits, having Ir masses equivalent to pure Ir spheres from about 0.8 to about 3.5 mm in diameter. Three of these are within a sufficiently reduced mass of powder to warrant searching for them using backscattered electron microscopy. In contrast, successively smaller splits of the Stevns Klint fish clay show no statistically significant deviation from the reported value of 32 +/- 2 ng/g Ir, suggesting a uniform Ir host-phase distribution. For the smallest split obtained thus far (100 +/- 40 ng/g Ir), a pure Ir sphere of equivalent Ir mass would be <0.05 min in diameter. (n.b. Although homogenizing and sieving of FC-1 to <75 min obviously obscured variations in stratigraphic distribution, it is unlikely to have affected the size-frequency distribution of Ir host phases.) We previously identified micrometer-scale Ir host phases by electron microscopy in melt-rock samples from two widely separated drill holes at the Chicxulub Basin, including a replicate split of Y6-NI9-R. One is an aggregate of subhedral Ir metal grains enclosed in silicate, in which no other Pt group elements (PGE) were detected. A second particle with twice the mass as the first, concentrated predominantly in a single grain, is associated with minor concentrations of Os, Ru, and Pt, and with adhering particles of corundum and perovskite. A third Ir-rich particle, with a greater apparent Os concentration, was identified before being lost as a result of charging under the electron beam. In addition to demonstrating the preservation of projectile components within the Chicxulub Crater, analogous phase associations in Ca- and Al-rich inclusions (CAI) from C2 and C3 chondrites suggest to us that these melt-rock Ir host phases are relics from a carbonaceous chondrite K/T boundary impactor Although the obviously low Ru/Ir ratios of the Chicxulub Ir host phases are qualitatively consistent with suggested PGE fractionation with distance during condensation in an ejecta cloud, it seems difficult to explain the accumulation of the about 3 x 10(exp 11) Ir atoms required to form a about 10(exp -10) g nugget of pure Ir metal within a jet of vaporized projectile expanding at 1-4 km/s, or to effectively exclude or remove commonly alloyed PGE and siderophile elements by fractionation processes resulting from condensation, oxidation, sulfidization, exsolution, or autometamorphism during cooling of the melt. We do not dismiss the importance of these processes entirely; on the contrary, other geochemical and mineralogical aspects of the melt rocks require them, and condensation from the expanding ejecta cloud appears to best explain the primary Ir host-phase distribution in the fish clay, as well as the high Ir concentrations associated with spinel-bearing spheroids at the K/T boundary in the Pacific Ocean . If the "relict" hypothesis is correct, micronuggets of other PGEs and alloys, not detected by our INAA screening, should also occur in the melt rocks. Possibly, the discrete host phases with lesser Ir masses are such alloys with subordinate Ir, rather than simply smaller, predominantly Ir-bearing particles. A CAI source for the relics would be consistent with either a comet or an asteroid K/T impact at Chicxulub. (Additional information contained in the original.)

Schuraytz, B. C.↗