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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.

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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Structured ionized winds shooting out from a quasar at relativistic speeds

Evidence indicates that supermassive black holes (SMBHs) exist at the centres of most galaxies. Their mass correlates with the galactic bulge mass, suggesting a coevolution with their host galaxies, most likely through powerful winds. X-ray observations have detected highly ionized winds outflowing at sub-relativistic speeds from the accretion disks around SMBHs. However, the limited spectral resolution of present X-ray instruments has left the physical structure and location of the winds poorly understood, hindering accurate estimates of their kinetic power. Here, in this study, the first X-Ray Imaging and Spectroscopy Mission (XRISM) observation of the luminous quasar PDS 456 is reported. The high-resolution spectrometer Resolve aboard XRISM enabled the discovery of five discrete velocity components outflowing at 20–30% of the speed of light. This demonstrates that the wind structure is highly inhomogeneous, which probably consists of up to a million clumps. The mass outflow rate is estimated to be 60–300 solar masses per year, with the wind kinetic power exceeding the Eddington luminosity limit. Compared with the galaxy-scale outflows, the kinetic power is more than three orders of magnitude larger, whereas the momentum flux is ten times larger. These estimates disfavour both energy-driven and momentum-driven outflow models. This suggests that such wind activity occurs in less than 10% of the quasar phase and/or that its energy/momentum is not efficiently transferred to the galaxy-scale outflows owing to the clumpiness of the wind and the interstellar medium.

Audard, Marc [Univ. of Geneva, Versoix (Switzerlan↗
NASA NTRS2007

The Beginning and End of the Universe

Cosmology is the scientific study of how the Universe began more than 13 billion years ago, how its properties have changed, and what its future might be. The balance of forces and energy cause the Universe to expand, first accelerating, then decelerating and then accelerating again. Within this overall structure, the interplay of atoms and light with the mysterious dark matter and dark energy causes stars and galaxies to form and evolve, leading to galaxies like our own home, the Milky Way. Observational cosmology uses telescopes on Earth and in space to reach back in time to find the faint remaining echoes of the Big Bang and to trace the formation and evolution of the galaxies and structures that fill the Universe. In this lecture, Dr. Gardner will give an overview of cosmology, outlining the 13-billion year history of the Universe, and highlighting the very rapid progress this field has made in the last decade. He will discuss the role that NASA space telescopes have played in this progress and will continue to play in the years to come. He will give a time-based history of the Universe, discussing the successive processes that formed matter, particles, atoms, stars and galaxies. In particular, he will focus on cosmological inflation, the rapid accelerated expansion that marks the beginning of the Universe, and dark energy, a tenuous substance that overcomes gravity and whose properties will determine its final fate.

Gardner, Jonathan P.↗
NASA NTRS2008

The Beginning and End of the Universe

Cosmology is the scientific study of how the Universe began more than 13 billion years ago, how its properties have changed, and what its future might be. The balance of forces and energy cause the Universe to expand, first accelerating, then decelerating and then accelerating again. Within this overall structure, the interplay of atoms and light with the mysterious dark matter and dark energy causes stars and galaxies to form and evolve, leading to galaxies like our own home, the Milky Way. Observational cosmology uses telescopes on Earth and in space to reach back in time to find the faint remaining echoes of the Big Bang and to trace the formation and evolution of the galaxies and structures that fill the Universe. In this lecture, Dr. Gradner will give an overview of cosmology, outlining the 13-billion year history of the Universe, and highlighting the very rapid progress this field has made i the last decade. He will discuss the role that NASA space telescopes have played in this progress and wil continue to play in the years to come. He will give a time-based history of the Universe, discussing the successive processes that formed matter, particles, atoms, stars and galaxies. In particular, he will focus on cosmological inflation, the rapid accelerated expansion that marks the beginning of the Universe, and dark energy, a tenuous substance that overcomes gravity and whose properties will determine its final fate.

Gardner, Jonathan↗
NASA NTRS2014

The Uncertainty of Biomass Estimates from Modeled ICESat-2 Returns Across a Boreal Forest Gradient

The Forest Light (FLIGHT) radiative transfer model was used to examine the uncertainty of vegetation structure measurements from NASA's planned ICESat-2 photon counting light detection and ranging (LiDAR) instrument across a synthetic Larix forest gradient in the taiga-tundra ecotone. The simulations demonstrate how measurements from the planned spaceborne mission, which differ from those of previous LiDAR systems, may perform across a boreal forest to non-forest structure gradient in globally important ecological region of northern Siberia. We used a modified version of FLIGHT to simulate the acquisition parameters of ICESat-2. Modeled returns were analyzed from collections of sequential footprints along LiDAR tracks (link-scales) of lengths ranging from 20 m-90 m. These link-scales traversed synthetic forest stands that were initialized with parameters drawn from field surveys in Siberian Larix forests. LiDAR returns from vegetation were compiled for 100 simulated LiDAR collections for each 10 Mg · ha(exp -1) interval in the 0-100 Mg · ha(exp -1) above-ground biomass density (AGB) forest gradient. Canopy height metrics were computed and AGB was inferred from empirical models. The root mean square error (RMSE) and RMSE uncertainty associated with the distribution of inferred AGB within each AGB interval across the gradient was examined. Simulation results of the bright daylight and low vegetation reflectivity conditions for collecting photon counting LiDAR with no topographic relief show that 1-2 photons are returned for 79%-88% of LiDAR shots. Signal photons account for approximately 67% of all LiDAR returns, while approximately 50% of shots result in 1 signal photon returned. The proportion of these signal photon returns do not differ significantly (p greater than 0.05) for AGB intervals greater than 20 Mg · ha(exp -1). The 50m link-scale approximates the finest horizontal resolution (length) at which photon counting LiDAR collection provides strong model fits and minimizes forest structure uncertainty in the synthetic Larix stands. At this link-scale AGB greater than 20 Mg · ha(exp -1) has AGB error from 20-50% at the 95% confidence level. These results suggest that the theoretical sensitivity of ICESat-2 photon counting LiDAR measurements alone lack the ability to consistently discern differences in inferred AGB at 10 Mg · ha(exp -1) intervals in sparse forests characteristic of the taiga-tundra ecotone.

LiDAR↗
NASA NTRS1983

Solar system history as recorded in the Saturnian ring structure

Holberg's analysis of the Voyager Saturn photographs in reflected and transparent light, and occultation data of stars seen through the rings are discussed. A hyperfine structure, with 10,000 ringlets can be explained by the Baxter-Thompson negative diffusion. This gives the ringlets a stability which makes it possible to interpret them as fossils, which originated at cosmogonic times. It is shown that the bulk structure can be explained by the combined cosmogonic shadows of the satellites Mimas, Janus and the Shepherd satellites. This structure originated at the transition from the plasma phase to the planetesimal phase. The shadows are not simple void regions but exhibit a characteristic signature. Parts of the fine structure, explained by Holberg as resonances with satellites, are interpreted as cosmogonic shadow effects. However, there are a number of ringlets which can neither be explained by cosmogonic nor by resonance effects. Analysis of ring data can reconstruct the plasma-planetesimal transition with an accuracy of a few percent.

Alfven, H.↗
NASA NTRS1983

Solar system history as recorded in the Saturnian ring structure

Holberg's analysis of the Voyager Saturn photographs in reflected and transparent light, and occultation data of stars seen through the rings are discussed. A hyperfine structure with 10,000 ringlets can be explained by the Baxter-Thompson negative diffusion. This gives the ringlets a stability which makes it possible to interpret them as fossils which originated at cosmogonic times. It is shown that the bulk structure can be explained by the combined cosmogonic shadows of the satellites Mimas and Janus and the Shepherd satellites. This structure originated at the transition from the plasma phase to the planetesimal phase. The shadows are not simple void regions but exhibit a characteristic signature. Parts of the fine structure, explained by Holberg as resonances with satellites, are interpreted as cosmogonic shadow effects. However, there are a number of ringlets which can neither be explained by cosmogonic nor by resonance effects. Analysis of ring data can reconstruct the plasma-planetesimal transition with an accuracy of a few percent. Previously announced in STAR as N84-12013

Alfven, H.↗
DOE OSTI2024

The development and applications of multidimensional biomolecular spectroscopy illustrated by photosynthetic light harvesting

The parallel and synergistic developments of atomic resolution structural information, new spectroscopic methods, their underpinning formalism, and the application of sophisticated theoretical methods have led to a step function change in our understanding of photosynthetic light harvesting, the process by which photosynthetic organisms collect solar energy and supply it to their reaction centers to initiate the chemistry of photosynthesis. The new spectroscopic methods, in particular multidimensional spectroscopies, have enabled a transition from recording rates of processes to focusing on mechanism. We discuss two ultrafast spectroscopies – two-dimensional electronic spectroscopy and two-dimensional electronic-vibrational spectroscopy – and illustrate their development through the lens of photosynthetic light harvesting. Both spectroscopies provide enhanced spectral resolution and, in different ways, reveal pathways of energy flow and coherent oscillations which relate to the quantum mechanical mixing of, for example, electronic excitations (excitons) and nuclear motions. The new types of information present in these spectra provoked the application of sophisticated quantum dynamical theories to describe the temporal evolution of the spectra and provide new questions for experimental investigation. While multidimensional spectroscopies have applications in many other areas of science, we feel that the investigation of photosynthetic light harvesting has had the largest influence on the development of spectroscopic and theoretical methods for the study of quantum dynamics in biology, hence the focus of this review. We conclude with key questions for the next decade of this review.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2026

Semi-inclusive deep-inelastic scattering on a polarized spin-1 target. II. Deuteron and spectator nucleon tagging

We develop the theoretical framework for semi-inclusive deep-inelastic scattering on a polarized spin-1 target and apply it to scattering on the polarized deuteron with spectator nucleon tagging. In Part I (previous article), we present the general form of the semi-inclusive cross section and polarization observables for the spin-1 target. In Part II (this article), we consider deep-inelastic scattering on the polarized deuteron with spectator nucleon tagging as a special case of target fragmentation. Methods of light-front quantization are employed to separate nuclear and hadronic structure in the high-energy process and achieve a composite description. The light-front wave function of the polarized deuteron is obtained from a rotationally covariant three-dimensional wave function in the center-of-mass frame of the proton-neutron system. The tagged structure functions are computed in the impulse approximation. The momentum and spin distribution of the active nucleon are controlled by the deuteron polarization and the detected spectator momentum (𝐷/𝑆 wave ratio). The cross section and spin asymmetries are evaluated for general deuteron polarization (vector and tensor, longitudinal and transverse) as functions of the spectator momentum. Tensor-polarized spin asymmetries of order unity are achieved for spectator momenta of approximately 300 MeV, which select configurations with a large 𝐷 wave. Sum rules for the tagged spin structure functions are derived. The results can be used for simulations of spectator tagging in future polarized fixed-target experiments (Jefferson Lab) or at the Electron-Ion Collider.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1981

Scanner for measuring fine sea-surface structures

An optical scanner using the principle of light reflection has been designed for determining directional slope distributions of the wind-disturbed water surface. The instrument has been tested successfully in the laboratory and could be used in the field. Some sample results along with procedures for data analysis are also presented.

Wu, J.↗
NASA NTRS1982

Anomalous atmospheric spectral features between 300 and 310 nm interpreted in light or new ozone absorption coefficient measurements

Real structure is revealed, by an analysis of continuous scan data from the solar backscattered UV instrument on Nimbus 7, in the backscattered atmospheric albedo region between 300 and 310 nm where spectral anomalies have been reported in ground-based observation. The spectral anomalies are explainable as structure at the 1-5% level in the ozone absorption coefficient, as measured by Bass and Paur (1981). The new absorption coefficient measurements are judged to approach the 1%-level of accuracy in atmospheric radiation calculation, which should resolve discrepancies between different Dobson wavelength pairs and between different instruments and permit the more accurate analysis of such second-order effects as NO emission, SO2 absorption in polluted atmospheres, and Raman scattering effects.

Mcpeters, R. D.↗
NASA NTRS1994

Optically Addressable Spatial Light Modulators

Integrated multiple-quantum-well/Fabry-Perot structure provides high-contrast variation of reflection of reading beam, under control of writing beam. Periodic potential barriers separate photogenerated electrons from holes, leading to long recombination lifetimes and large concentrations of free charge carriers. Concentrations quench excitons or fill energy bands in quantum wells, altering absorption of reading beam.

Maserjian, Joseph↗
NASA NTRS2018

Super Ball Bot - Structures for Planetary Landing and Exploration

Small, light-weight and low-cost missions will become increasingly important to NASA's exploration goals for our solar system. Ideally teams of dozens or even hundreds of small, collapsable robots, weighing only a few kilograms a piece, will be conveniently packed during launch and would reliably separate and unpack at their destination. Such teams will allow rapid, reliable in-situ exploration of hazardous destination such as Titan, where imprecise terrain knowledge and unstable precipitation cycles make single-robot exploration problematic. Unfortunately landing many lightweight conventional robots is difficult with conventional technology. Current robot designs are delicate, requiring combinations of devices such as parachutes, retrorockets and impact balloons to minimize impact forces and to place a robot in a proper orientation. Instead we propose to develop a radically different robot based on a "tensegrity" built purely upon tensile and compression elements. These robots can be light-weight, absorb strong impacts, are redundant against single-point failures, can recover from different landing orientations and are easy to collapse and uncollapse. We believe tensegrity robot technology can play a critical role in future planetary exploration.

Agogino, Adrian K.↗
NASA NTRS1998

Transport of Light Ions in Matter

A recent set of light ion experiments are analyzed using the Green's function method of solving the Boltzmann equation for ions of high charge and energy (the GRNTRN transport code) and the NUCFRG2 fragmentation database generator code. Although the NUCFRG2 code reasonably represents the fragmentation of heavy ions, the effects of light ion fragmentation requires a more detailed nuclear model including shell structure and short range correlations appearing as tightly bound clusters in the light ion nucleus. The most recent NTJCFRG2 code is augmented with a quasielastic alpha knockout model and semiempirical adjustments (up to 30 percent in charge removal) in the fragmentation process allowing reasonable agreement with the experiments to be obtained. A final resolution of the appropriate cross sections must await the full development of a coupled channel reaction model in which shell structure and clustering can be accurately evaluated.

Wilson, J. W.↗
NASA NTRS1993

GRO: Red-shifted electron-positron annihilation gamma-rays from radiopulsars

Reported red-shifted e(+) + e(-) yields gamma + gamma 511 keV gamma-rays from the Crab pulsar would, if ultimately confirmed, provide crucial clues about the structure of the powerful magnetospheric accelerator in that rapidly spinning gamma-ray pulsar. In an attempt to understand the origin of this component of the Crab pulsar's emission, we try to account for the following: (1) a flow of approximately 10 exp 40 e(+/-)/s into near the surface of the neutron star; (2) a relatively narrow annihilation line implying that the annihilating e(+/-) pairs probably had a velocity (along vector B) less than or approximately = 10(exp -1)c; and (3) a tentative light curve suggesting a doubly peaked structure different from that of the rest of the Crab pulsar's nonthermal radiation.

Ruderman, Malvin↗
NASA NTRS2006

Cryogenic Fracture Toughness Evaluation of an Investment Cast Al-Be Alloy for Structural Applications

Aluminum-Beryllium metal matrix composite materials are useful due to their desirable performance characteristics for aerospace applications. Desirable characteristics of this material includes light-weight, dimensional stability, stiffness, good vibration damping characteristics, low coefficient of thermal expansion, and workability, This material is 3.5 times stiffer and 22% lighter than conventional aluminum alloys. electro-optical systems, advanced sensor and guidance components for flight and satellite systems, components for light-weight high-performance aircraft engines, and structural components for helicopters. Aluminum-beryllium materials are now available in the form of near net shape investment castings. In this materials properties characterization study, the cryogenic tensile and fracture properties of an investment casting alloy, Beralcast 363, were determined. Tensile testing was performed at 21 C (70 F), -73.3 C (-100 F), -195.5 C (-320 F) and -252.8 C (-423 F), and fracture (K(sub lc) and da/dN) testing was performed at -73.3 C (-100 F), -195.5 C (-320 F) and -252.8 C (-423 F). Their use is attractive for weight critical structural applications such as advanced

Gamwell, W. R.↗
DOE OSTI2025

Elastic scattering in the 12 N + 197 Au system at 𝐸 lab = 70 MeV

Halo structure is an interesting exotic configuration developed in some light weakly bound nuclei, where a valence particle orbits a nuclear core. Signatures of halo structure can be observed in the angular distributions of the elastic scattering induced by these nuclei at energies around the Coulomb barrier. There are some well-studied reactions with neutron-rich halo nuclei, such as 6 He and 11 Li . However, the information is scarce on the proton-rich side. Recent works confirm the halo structure in the 8B nuclei but still lack more experimental studies for other proton-halo candidates, such as 12 N and 17 F. In this work, we report experimental data for the elastic scattering of 12 N on 197 Au target at 𝐸 lab = 70 MeV. The 12 N is a proton-rich nucleus with proton separation energy 𝑆 𝑝 = 600 keV, which is higher than the 8 B (𝑆 𝑝 = 137 keV) and almost the same as the 17 F (𝑆 𝑝 = 601 keV). Data were obtained at the Cyclotron Institute of Texas A&M University where the 12 N radioactive beam was produced by the momentum achromatic recoil spectrometer. The calculation of the optical model was used to fit the measured angular distribution for the elastic scattering and to obtain the reaction cross section 𝜎 𝑅 . We also performed continuum discretized coupled-channel calculations to compare with the experimental data. The angular distribution of the elastic cross sections exhibits a suppression of the Fresnel peak. From the fitting of the optical model, we obtain the total reaction cross section, 𝜎 𝑅 = 1269 ± 41 mb. The agreement between the CDCC calculation and the experimental elastic scattering data is limited and the breakdown does not exhaust the measured 𝜎 𝑅 . The resulting reduced reaction cross section 𝜎 Red for 12 N + 197 Au is large and comparable to the one obtained for the 8 B + 208 Pb system. This suggests a strong decoupling of the valence proton from the core because of the low binding energy and a dynamic polarization effect. Here, more research is required to estimate the contribution of core excitation.

Elastic scattering reactions↗
DOE OSTI2025

Spin switchable optical phenomena in Rashba band structures through intersystem crossing in momentum space in solution-processing 2D-superlattice perovskite film

Spin-switchable phenomena are a critical element for the development of spintronic and chiroptic devices. Herein we combine a 2D-superlattice perovskite (4,4-DFPD2PbI4) film with a ferromagnetic cobalt (Co) layer to form a multiferroic perovskite/Co interface, and demonstrate spin-switchable circularly polarized luminescence (CPL) between right-handed σ+ and left-handed σ− polarizations. When the ferromagnetic spins of Co at the Co/perovskite interface are altered between positive and negative magnetic field directions, the CPL from the 2D-superlattice perovskite switches from σ+ to σ− polarization. The magnetic field effects present a unique method to confirm that CPL is generated by the circular-orbital momentum of light-emitting excitons within Rashba band structures, eliminating artifacts involving structural birefringence. Our polarized neutron reflectometry measurements confirm a super long-range spin-orbit interaction occurring in the 2D-superlattice perovskite films. The temperature dependence of spin-switchable phenomenon indicates an extraordinarily long orbital polarization lifetime, reaching microseconds at room temperature and milliseconds at 5 K.

36 MATERIALS SCIENCE↗
NASA NTRS2005

Improvement of Raman lidar algorithm for quantifying aerosol extinction

Aerosols are particles of different composition and origin and influence the formation of clouds which are important in atmospheric radiative balance. At the present there is high uncertainty on the effect of aerosols on climate and this is mainly due to the fact that aerosol presence in the atmosphere can be highly variable in space and time. Monitoring of the aerosols in the atmosphere is necessary to better understanding many of these uncertainties. A lidar (an instrument that uses light to detect the extent of atmospheric aerosol loading) can be particularly useful to monitor aerosols in the atmosphere since it is capable to record the scattered intensity as a function of altitude from molecules and aerosols. One lidar method (the Raman lidar) makes use of the different wavelength changes that occur when light interacts with the varying chemistry and structure of atmospheric aerosols. One quantity that is indicative of aerosol presence is the aerosol extinction which quantifies the amount of attenuation (removal of photons), due to scattering, that light undergoes when propagating in the atmosphere. It can be directly measured with a Raman lidar using the wavelength dependence of the received signal. In order to calculate aerosol extinction from Raman scattering data it is necessary to evaluate the rate of change (derivative) of a Raman signal with respect to altitude. Since derivatives are defined for continuous functions, they cannot be performed directly on the experimental data which are not continuous. The most popular technique to find the functional behavior of experimental data is the least-square fit. This procedure allows finding a polynomial function which better approximate the experimental data. The typical approach in the lidar community is to make an a priori assumption about the functional behavior of the data in order to calculate the derivative. It has been shown in previous work that the use of the chi-square technique to determine the most likely functional behavior of the data prior to actually calculating the derivative eliminates the need for making a priori assumptions. We note that the a priori choice of a model itself can lead to larger uncertainties as compared to the method that is validated here. In this manuscript, the chi-square technique that determines the most likely functional behavior is validated through numerical simulation and by application to a large body of Raman lidar measurements. In general, we show that the chi-square approach to evaluate aerosol extinction yields lower extinction uncertainty than the traditional technique. We also use the technique to study the feasibility of developing a general characterization of the extinction uncertainty that could permit the uncertainty in Raman lidar aerosol extinction measurements to be estimated accurately without the use of the chi-square technique.

Russo, Felicita↗