SEARCH · Engineering Papers

Results for “B(HO)2”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6

All sources NASA NTRS DOE OSTI

NASA NTRS1994

Three-dimensional structure of Schistosoma japonicum glutathione S-transferase fused with a six-amino acid conserved neutralizing epitope of gp41 from HIV

The 3-dimensional crystal structure of glutathione S-transferase (GST) of Schistosoma japonicum (Sj) fused with a conserved neutralizing epitope on gp41 (glycoprotein, 41 kDa) of human immunodeficiency virus type 1 (HIV-1) (Muster T et al., 1993, J Virol 67:6642-6647) was determined at 2.5 A resolution. The structure of the 3-3 isozyme rat GST of the mu gene class (Ji X, Zhang P, Armstrong RN, Gilliland GL, 1992, Biochemistry 31:10169-10184) was used as a molecular replacement model. The structure consists of a 4-stranded beta-sheet and 3 alpha-helices in domain 1 and 5 alpha-helices in domain 2. The space group of the Sj GST crystal is P4(3)2(1)2, with unit cell dimensions of a = b = 94.7 A, and c = 58.1 A. The crystal has 1 GST monomer per asymmetric unit, and 2 monomers that form an active dimer are related by crystallographic 2-fold symmetry. In the binding site, the ordered structure of reduced glutathione is observed. The gp41 peptide (Glu-Leu-Asp-Lys-Trp-Ala) fused to the C-terminus of Sj GST forms a loop stabilized by symmetry-related GSTs. The Sj GST structure is compared with previously determined GST structures of mammalian gene classes mu, alpha, and pi. Conserved amino acid residues among the 4 GSTs that are important for hydrophobic and hydrophilic interactions for dimer association and glutathione binding are discussed.

Schistosoma japonicum/enzymology/genetics/immunolo↗

DOE OSTI2021

Superionic iron oxide–hydroxide in Earth’s deep mantle

Water ice becomes a superionic phase under the high pressure and temperature conditions of deep planetary interiors of ice planets such as Neptune and Uranus, which affects interior structures and generates magnetic fields. The solid Earth, however, contains only hydrous minerals with a negligible amount of ice. Here we combine high pressure and temperature electrical conductivity experiments, Raman spectroscopy and first-principles simulations to investigate the state of hydrogen in the pyrite-type FeO 2 H x (x ≤ 1), which is a potential H-bearing phase near the core–mantle boundary. We find that when the pressure increases beyond 73 GPa at room temperature, symmetric hydroxyl bonds are softened and the H + (or proton) becomes diffusive within the vicinity of its crystallographic site. Increasing temperature under pressure, the diffusivity of hydrogen is extended beyond the individual unit cell to cover the entire solid, and the electrical conductivity soars, indicating a transition to the superionic state, which is characterized by freely moving protons and a solid FeO 2 lattice. Furthermore, the highly diffusive hydrogen provides fresh transport mechanisms for charge and mass, which dictate the geophysical behaviours of electrical conductivity and magnetism, as well as geochemical processes of redox, hydrogen circulation and hydrogen isotopic mixing in Earth’s deep mantle.

58 GEOSCIENCES↗

DOE OSTI2022

A Quasar Shedding Its Dust Cocoon at Redshift 2

We present the first near-IR spectroscopy and joint analyses of multiwavelength observations for SDSS J082747.14+425241.1, a dust-reddened, weak broad emission-line quasar (WLQ) undergoing a remarkable broad-absorption line (BAL) transformation. The systemic redshift is more precisely measured to be z = 2.070 ± 0.001 using Hβ compared to z = 2.040 ± 0.003 using Mg ιι from the literature, signifying an extreme Mg ιι blueshift of 2140 ± 530 km s –1 relative to Hβ. Using the Hβ-based single-epoch scaling relation with a systematic uncertainty of 0.3 dex, its black hole (BH) mass and Eddington ratio are estimated to be M BH ~ 6.1 × 10 8 M ⊙ and λ Edd ~ 0.71, indicative of being in a rapidly accreting phase. Our investigations confirm the WLQ nature and the LoBAL → HiBAL transformation, along with a factor of 2 increase in the Mg ιι+Fe ιι emission strength and a decrease of 0.1 in E(B – V) over two decades. The kinetic power of this LoBAL wind at R ~ 15 pc from its BH is estimated to be ~43% of the Eddington luminosity, sufficient for quasar feedback upon its host galaxy albeit with an order-of-magnitude uncertainty. This quasar provides a clear example of the long-sought scenario where LoBAL quasars are surrounded by dust cocoons, and wide-angle nuclear winds play a key role in the transition of red quasars evolving into the commonly seen blue quasars.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2021

The 450 Day X-Ray Monitoring of the Changing-look AGN 1ES 1927+654

1ES 1927+654 is a nearby active galactic nucleus (AGN) that underwent a changing-look event in early 2018, developing prominent broad Balmer lines that were absent in previous observations. We have followed up this object in the X-rays with an ongoing campaign that started in 2018 May and that includes 265 NICER (for a total of 678 ks) and 14 Swift/XRT (26 ks) observations, as well as three simultaneous XMM-Newton/NuSTAR (158/169 ks) exposures. In the X-rays, 1ES 1927+654 shows a behavior unlike any previously known AGN. The source is extremely variable both in spectral shape and flux and does not show any correlation between X-ray and UV flux on timescales of hours or weeks/months. After the outburst, the power-law component almost completely disappeared, and the source showed an extremely soft continuum dominated by a blackbody component. The temperature of the blackbody increases with the luminosity, going from kT∼80 eV (for a 0.3–2 keV luminosity ofL0.3−2∼1041.5erg s−1) to∼200 eV (forL0.3−2∼1044erg s−1). The spectra show evidence of ionized outflows and of a prominent feature at ∼1 keV, which can be reproduced by a broad emission line. The unique characteristics of1ES 1927+654 in the X-ray band suggest that it belongs to a new type of changing-look AGN. Future X-ray surveys might detect several more objects with similar properties.

Astrophysical black holes↗

NASA NTRS2020

The Destruction and Recreation of the X-Ray Corona in a Changing-look Active Galactic Nucleus

We present the drastic transformation of the X-ray properties of the active galactic nucleus 1ES 1927+654, following a changing-look event. After the optical/UV outburst the power-law component, produced in the X-ray corona, disappeared, and the spectrum of 1ES 1927+65 instead became dominated by a blackbody component (kT ∼ 80− 120 eV). This implies that the X-ray corona, ubiquitously found in AGN, was destroyed in the event. Our dense ∼ 450 day long X-ray monitoring shows that the source is extremely variable in the X-ray band. On long time scales the source varies up to ∼ 4 dex in ∼ 100 days, while on short timescales up to ∼ 2 dex in ∼ 8 hours. The luminosity of the source is found to first show a strong dip down to ∼ 10(exp 40) erg/s, and then a constant increase in luminosity to levels exceeding the pre-outburst level &300 days after the optical event detection, rising up asymptotically to ∼ 2 × 10(exp 44) erg/s. As the X-ray luminosity of the source increases, the X-ray corona is recreated, and a very steep power-law component (Γ ≃ 3) reappears, and dominates the emission for 0.3–2 keV luminosities & 10(exp 43.7) erg/s, ∼ 300 days after the beginning of the event. We discuss possible origins of this event, and speculate that our observations could be explained by the interaction between the accretion flow and debris from a tidally disrupted star. Our results show that changing-look events can be associated with dramatic and rapid transformations of the innermost regions of accreting SMBHs.

C. Ricci↗

NASA NTRS2021

THE 450DAYS X-RAY MONITORING OF THE CHANGING-LOOK AGN 1ES 1927+654

1ES 1927+654 is a nearby active galactic nucleus (AGN) which underwent a changing-look event in early 2018, developing prominent broad Balmer lines which were absent in previous observations. We have followed up this object in the X-rays with an ongoing campaign that started in May 2018, and that includes 265 NICER (for a total of 678 ks) and 14 Swift/XRT (26 ks) observations, as well as three simultaneous XMM-Newton/NuSTAR (158/169 ks) exposures. In the X-rays, 1ES 1927+654 shows a behaviour unlike any previously known AGN. The source is extremely variable both in spectral shape and flux, and does not show any correlation between X-ray and UV flux on timescales of hours or weeks/months. After the outburst the power-law component almost completely disappeared, and the source showed an extremely soft continuum dominated by a blackbody component. The temperature of the blackbody increases with the luminosity, going from kT ∼ 80 eV (for a 0.3–2 keV luminosity of L(0.3−2) ∼ 10^(41.5) erg/s) to ∼ 200 eV (for L(0.3−2) ∼ 10^(44) erg/s). The spectra show evidence of ionized outflows, and of a prominent feature at ∼ 1 keV, which can be reproduced by a broad emission line. The unique characteristics of 1ES 1927+654 in the X-ray band suggest that it belongs to a new type of changing-look AGN. Future X-ray surveys might detect several more objects with similar properties.

C. Ricci↗

DOE OSTI2023

HamLib: A Library of Hamiltonians for Benchmarking Quantum Algorithms and Hardware

For a considerable time, large datasets containing problem instances have proven valuable for analyzing computer hardware, software, and algorithms. One notable example of the value of large datasets is ImageNet [1], a vast repository of images that has been instrumental in testing numerous deep learning packages. Similarly, in the domain of computational chemistry and materials science, the availability of extensive datasets such as the Protein Data Bank [2], the Materials Project [3], and QM9 [4] has greatly facilitated the evaluation of new algorithms and software approaches, while also promoting standardization within the field. These well-defined datasets and problem instances, in turn, serve as the foundation for creating benchmarking suites like MLPerf [5] and LINPACK [6], [7]. These suites enable fair and rigorous comparisons of different methodologies and solutions, fostering continuous advancements in various areas of computer science and beyond.

Sawaya, Nicolas PD↗

NASA NTRS2011

Wallops Low Elevation Link Analysis for the Constellation Launch/Ascent Links

To execute the President's Vision for Space Exploration, the Constellation Program (CxP) was formed to build the next generation spacecraft Orion and launch vehicles Ares, to transport human and cargo to International Space Station (ISS), moon, and Mars. This paper focuses on the detailed link analysis for Orion/Ares s launch and ascent links with Wallops 11.3m antenna (1) Orion's Dissimilar Voice link: 10.24 Kbps, 2-way (2) Ares Developmental Flight Instrument link, 20 Mbps, downlink. Three launch trajectories are considered: TD7-E, F (Feb), and G (Aug). In certain launch scenarios, the critical events of main engine cutoff (MECO) and Separation occur during the low elevation regime of WFF s downrange -- less than 5 degree elevation angle. The goal of the study is to access if there is enough link margins for WFF to track the DV and DFI links.

Constellation↗

DOE OSTI2021

Local ordering in disordered Nd x Zr 1-x O 2-0.5x pyrochlore as observed using neutron total scattering

Pyrochlore complex oxides (A 2 B 2 O 7 ) are an important class of fluorite-derivative ceramics with exceptional chemical and structural versatility which make them ideal model systems for studying disordering mechanisms over a range of spatial scales. Here, neutron total scattering methods were used to analyze the structural behavior in the non-stoichiometric series Nd x Zr 1-x O 2-0.5x (0.5 ≤ x ≤ 0.23) as a function of Nd content, x. Characterization of the structure functions using Rietveld refinement and the pair distribution functions with small-box refinement reveal complex disordering pathways; the average, long-range phase changes over a very narrow compositional range from pyrochlore ($Fd\bar{3}m$) to defect fluorite ($Fm\bar{3}m$) through full randomization of the cation and anion sublattices at x ~ 0.31, while the local, short-range structure continuously adopts a weberite-type atomic arrangement (C222 1 ). Comparison to a previously studied Ho 2 Ti 2-x Zr x O 7 solid solution series reveals how changes in chemical composition and stoichiometry modify defect formation and determine how disordering progresses across different length scales in pyrochlore oxides.

36 MATERIALS SCIENCE↗

DOE OSTI2024

HamLib: A library of Hamiltonians for benchmarking quantum algorithms and hardware

In order to characterize and benchmark computational hardware, software, and algorithms, it is essential to have many problem instances on-hand. This is no less true for quantum computation, where a large collection of real-world problem instances would allow for benchmarking studies that in turn help to improve both algorithms and hardware designs. To this end, here we present a large dataset of qubit-based quantum Hamiltonians. The dataset, called HamLib (for Hamiltonian Library), is freely available online and contains problem sizes ranging from 2 to 1000 qubits. HamLib includes problem instances of the Heisenberg model, Fermi-Hubbard model, Bose-Hubbard model, molecular electronic structure, molecular vibrational structure, MaxCut, Max- k -SAT, Max- k -Cut, QMaxCut, and the traveling salesperson problem. The goals of this effort are (a) to save researchers time by eliminating the need to prepare problem instances and map them to qubit representations, (b) to allow for more thorough tests of new algorithms and hardware, and (c) to allow for reproducibility and standardization across research studies.

97 MATHEMATICS AND COMPUTING↗

NASA NTRS1999

Cepheid Calibration of the Peak Brightness of SNe Ia.: SN 1989B in NGC 3627 - 9

Repeated imaging observations have been made of NGC 3627 with the Hubble Space Telescope in 1997/98, over an interval of 58 days. Images were obtained on 12 epochs in the F555W band and on five epochs in the F8141,V band. The galaxy hosted the prototypical, "Branch normal", type la supernova SN 1989B. A total of 83 variables have been found, of which 68 are definite Cepheid variables with periods ranging from 75 days to 3.85 days. The de-reddened distance modulus is determined to be (m - M)(sub 0) = 30.22 +/- 0.12 (internal uncertainty) using a subset of the Cepheid data whose reddening and error parameters are secure. The photometric data of Wells et al. (1994), combined with the Cepheid data for NGC 3627 give MB(max) = -19.36 +/- 0.18 and M(sub V)(max) = -19.34 +/- 0.16 for SN 1989B. Combined with the previous six calibrations in this program, plus two additional calibrations determined by others gives the mean absolute magnitudes at maximum of (M(sub B)) = -19.48 +/- 0.07 for "Brunch normal" SNe Ia at this interim stage in the calibration program. Using the argument by Wells et al. (1994) that SN 1989B here is virtually identical in decay rate and colors at maximum with SN 198ON in NGC 1316 in the Fornax cluster, and that such identity means nearly identical absolute magnitude, it follows that the difference in the distance modulus of NGC 3627 and NGC 1316 is 1.62 +/- 0.03 mag. Thus the NGC 3627 modulus implies that (m - M)(sub 0) = 31.84 for NGC 1316. The second parameter correlations of M(max) of blue SNe la with decay rate, color at maximum, and Hubble type are re-investigated. The dependence of (M(max)) on decay rate is non-linear, showing a minimum for decay rates between 1.0 less than ADelta(sub m)15 less than 1.6. Magnitudes corrected for decay rate show no dependence on Hubble type, but a dependence on color remains. Correcting both the fiducial sample of 34 SNe la with decay-rate data and the current eight calibrating SNe la for the correlation with decay rate as well as color gives H(sub 0) = 60 +/- 2 (internal) km/s Mpc, in both B and V. The same value to within 4% is obtained if only the SNe la in spirals (without second parameter corrections) are considered. The correlation of SNe la color at maximum with M(max) cannot be due to internal absorption because the slope coefficients in B, V, and I with the change in magnitude are far from or even opposite to the canonical reddening values. The color effect must be intrinsic to the supernova physics. "Absorption" corrections of distant blue SNe la will lead to incorrect values of H(sub 0). The Cepheid distances used in this series are insensitive to metallicity differences. The zeropoint of the P-L relation is based on an assumed LMC modulus of (m - M)(sub 0) = 18.50. As this may have to be increased by 0(sup m).06 to 0(sup m).08, all distances in this paper will follow and Ho will decrease by 3 - 4%.

Saha, A.↗

DOE OSTI2023

Machine learning guided discovery of superconducting calcium borocarbides

Pursuit of superconductivity in light-element systems at ambient pressure is of great experimental and theoretical interest. In this work, we combine a machine learning (ML) method with first-principles calculations to efficiently search for the energetically favorable ternary Ca-B-C compounds. Three layered borocarbides (stable CaBC 5 and metastable Ca 2 BC 11 and CaB 3 C 3 ) are predicted to be phonon-mediated superconductors at ambient pressure. The stable CaBC 5 and the low-energy metastable Ca 2 BC 11 (with formation energy only 9.5 meV/atom above the convex hull) have a superconducting T c of 5.2 and 8.9 K, respectively. While the hexagonal CaB 3 C 3 possesses a T c of 26.1 K, it is metastable with formation energy of 153 meV/atom above the convex hull. The ML-guided approach opens up a way for greatly accelerating the discovery of new high-T c superconductors.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on HoBO3 by Materials Project

HoBO3 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are six inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.32–2.48 Å. In the second Ho3+ site, Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.27–2.49 Å. In the third Ho3+ site, Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.29–2.49 Å. In the fourth Ho3+ site, Ho3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ho–O bond distances ranging from 2.28–2.70 Å. In the fifth Ho3+ site, Ho3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ho–O bond distances ranging from 2.18–2.51 Å. In the sixth Ho3+ site, Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.27–2.57 Å. There are six inequivalent B3+ sites. In the first B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.38–1.41 Å. In the second B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.45–1.56 Å. In the third B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.44–1.55 Å. In the fourth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.46–1.56 Å. In the fifth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.45–1.55 Å. In the sixth B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.37 Å) and one longer (1.42 Å) B–O bond length. There are eighteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to three Ho3+ and one B3+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ho3+ and two B3+ atoms. In the third O2- site, O2- is bonded in a distorted single-bond geometry to three Ho3+ and one B3+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to three Ho3+ and one B3+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to two Ho3+ and one B3+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to three Ho3+ and one B3+ atom. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to three Ho3+ and one B3+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ho3+ and two B3+ atoms. In the ninth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Ho3+ and two B3+ atoms. In the tenth O2- site, O2- is bonded in a distorted single-bond geometry to two Ho3+ and one B3+ atom. In the eleventh O2- site, O2- is bonded in a distorted single-bond geometry to three Ho3+ and one B3+ atom. In the twelfth O2- site, O2- is bonded in a 2-coordinate geometry to two Ho3+ and two B3+ atoms. In the thirteenth O2- site, O2- is bonded in a distorted single-bond geometry to three Ho3+ and one B3+ atom. In the fourteenth O2- site, O2- is bonded in a 1-coordinate geometry to three Ho3+ and one B3+ atom. In the fifteenth O2- site, O2- is bonded in a distorted single-bond geometry to three Ho3+ and one B3+ atom. In the sixteenth O2- site, O2- is bonded in a 1-coordinate geometry to three Ho3+ and one B3+ atom. In the seventeenth O2- site, O2- is bonded in a distorted single-bond geometry to three Ho3+ and one B3+ atom. In the eighteenth O2- site, O2- is bonded in a distorted single-bond geometry to three Ho3+ and one B3+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2023

Reaching a burning plasma and ignition using smaller capsules/ Hohlraums , higher radiation temperatures, and thicker ablator/ice on the national ignition facility

In indirect-drive implosions, the final core hot spot energy and pressure and, hence, neutron yield attainable in 1D increase with increasing laser peak power and, hence, radiation drive temperature at the fixed capsule and Hohlraum size. Here we present simple analytic scalings validated by 1D simulations that quantify the improvement in performance and use this to explain existing data and simulation trends. Extrapolating to the 500 TW National Ignition Facility peak power limit in a low gas-fill 5.4 mm diameter Hohlraum based on existing high adiabat implosion data at 400 TW, 1.3 MJ and 1 × 10 16 yield, we find that a 2–3 × 10 17 yield (0.5–0.7 MJ) is plausible using only 1.8 MJ of laser energy. Based on existing data varying deuterium–tritium (DT) fuel thickness and dopant areal density, further improvements should be possible by increasing DT fuel areal density, and hence confinement time and yield amplification.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS1998

Dryout and Rewetting in the Pool Boiling Experiment Flown on STS-72 (PBE-2 B) and STS-77 (PBE-2 A)

Experiments were conducted in the microgravity of space in which a pool of liquid (R-113), initially at a precisely defined pressure and temperature, is subjected to a step imposed heat flux from a semi-transparent thin-film heater forming part of one wall of the container such that boiling is initiated and maintained for a defined period of time at a constant pressure level. A total of nine tests were conducted at three levels of heat flux and three levels of subcooling in each of the two space experiments in a GAS canister on the STS-77, -72, respectively. Three (3) modes of propagation of boiling across the heater surface and subsequent vapor bubble growths were observed, in addition to the two (2) modes observed in the previous microgravity pool boiling space flights on STS-47, -57, and -60. Of particular interest were the extremely dynamic or "explosive" growths, which were determined to be the consequence of the large increase in the liquid-vapor interface area associated with the appearance of a corrugated or rough interface. Predictions of circumstances for its onset have been carried out. Assumptions were necessary regarding the character of disturbances necessary for the instabilities to grow. Also, a new vapor bubble phenomena was observed in which small vapor bubbles migrated toward a larger bubble, eventually coalescing with this larger bubble. The heat transfer was enhanced approximately 30% as a result of these migrating bubbles, which is believed to be a vapor bubble manifestation of Marangoni convection and/or molecular momentum effects, sometimes referred to as vapor recoil. The circumstances of heat flux and liquid subcooling necessary to produce heater surface dryout for an initially stagnant liquid subjected to an imposed heat flux have been more closely identified.

Merte, Herman, Jr.↗

DOE OSTI2021

Geometry of the charge density wave in the kagome metal A V 3 Sb 5

Kagome lattice is a fertile platform for topological and intertwined electronic excitations. Recently, experimental evidence of an unconventional charge density wave (CDW) is observed in a Z 2 kagome metal AV 3 Sb 5 (A=K, Cs, Rb). This observation triggers wide interest in the interplay between frustrated crystal structure and Fermi surface instabilities. Here, we analyze the lattice effect and its impact on CDW in AV 3 Sb 5 . Based on published experimental data, we show that the 2×2×2 CDW breaks the sixfold rotational symmetry of the crystal due to the phase shift between kagome layers and can explain the twofold symmetric CDW peak intensity observed by scanning tunneling spectroscopy. The coupling between the lattice and electronic degrees of freedom yields a weak first-order structural transition without continuous change of lattice dynamics. Our result emphasizes the fundamental role of lattice geometry in proper understanding of unconventional electronic orders in AV 3 Sb 5 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

NASA NTRS2020

The SUrvey for Pulsars and Extragalactic Radio Bursts - IV. Discovery and polarimetry of a 12.1-s radio pulsar

We report the discovery of PSR J2251−3711, a radio pulsar with a spin period of 12.1 s, the second longest currently known. Its timing parameters imply a characteristic age of 15 Myr, a surface magnetic field of 1.3 × 10^(13) G, and a spin-down luminosity of 2.9 × 10^(29) erg/s. Its dispersion measure of 12.12(1) pc/cu. cm leads to distance estimates of 0.5 and 1.3 kpc according to the NE2001 and YMW16 Galactic free electron density models, respectively. Some of its single pulses show an uninterrupted 180-deg sweep of the phase-resolved polarization position angle, with an S-shape reminiscent of the rotating vector model prediction. However, the fact that this sweep occurs at different phases from one pulse to another is remarkable and without straightforward explanation. Although PSR J2251−3711 lies in the region of the P − P˙ parameter space occupied by the X-ray isolated neutron stars (XINS), there is no evidence for an X-ray counterpart in our Swift XRT observation; this places a 99 per cent-confidence upper bound on its unabsorbed bolometric thermal luminosity of 1.1 × 10^(31) (d/1 kpc)^2 erg/s for an assumed temperature of 85 eV, where d is the distance to the pulsar. Further observations are needed to determine whether it is a rotation-powered pulsar with a true age of at least several Myr, or a much younger object such as an XINS or a recently cooled magnetar. Extreme specimens like PSR J2251−3711 help bridge populations in the so-called neutron star zoo in an attempt to understand their origins and evolution.

V Morello↗

DOE OSTI2020

The cross correlation of the ABS and ACT maps

One of the most important checks for systematic errors in CMB studies is the cross correlation of maps made by independent experiments. In this study we report on the cross correlation between maps from the Atacama B-mode Search (ABS) and Atacama Cosmology Telescope (ACT) experiments in both temperature and polarization. These completely different measurements have a clear correlation with each other and with the Planck satellite in both the EE and TE spectra at ℓ<400 over the roughly 0110 deg 2 common to all three. The TB, EB, and BB cross spectra are consistent with noise. Exploiting such cross-correlations will be important for future experiments operating in Chile that aim to probe the 30<ℓ<8,000 range.

79 ASTRONOMY AND ASTROPHYSICS↗