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Cheng, L.

Publications and source records attributed to Cheng, L..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Relativistic Exact Two-Component Theory in the Generalized Pseudospectral Representation

We present a formulation and implementation of exact two-component (X2C) relativistic theory in the generalized pseudospectral representation. When combined with the Hartree-Fock-Slater framework, this approach enables efficient and accurate treatments of scalar-relativistic and spin-orbit effects in atomic electronic structures without the computational overhead of four-component methods. Benchmark calculations across light and heavy elements demonstrate that the our X2C scheme yields substantially more accurate relativistic corrections to core-electron binding energies than perturbational Breit-Pauli treatments while converging more rapidly with respect to basis size. The method provides an improved computational framework for modeling ultrafast x-ray-induced processes in heavy-element systems.

Wang, Xubo↗
DOE OSTI2024

Anion Photoelectron Spectroscopy and Ab Initio Studies of the UF – Anion

A synergistic anion photoelectron spectroscopic and ab initio computational study of photodetachment of UF – is reported. The measurement determined a vertical detachment energy of 0.63(03) eV, which is consistent with a spinor-based relativistic coupled-cluster CCSD(T) value of 0.61 eV. The complex spectral features due to excited electronic states and vibrational progressions of UF are analyzed and assigned with the help of spin–orbit-coupled multireference perturbation theory and spinor-based relativistic coupled-cluster calculations. UF and UF – are confirmed to be dominated by ionic bonding. Furthermore, the usefulness of the spinor CCSD(T) approach is demonstrated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Properties of Cosmic Deuterons Measured by the Alpha Magnetic Spectrometer

Precision measurements by the Alpha Magnetic Spectrometer (AMS) on the International Space Station of the deuteron (𝐷) flux are presented. The measurements are based on 21 × 10 6 𝐷 nuclei in the rigidity range from 1.9 to 21 GV collected from May 2011 to April 2021. We observe that over the entire rigidity range the 𝐷 flux exhibits nearly identical time variations with the 𝑝, 3 He, and 4 He fluxes. Above 4.5 GV, the 𝐷/ 4 He flux ratio is time independent and its rigidity dependence is well described by a single power law ∝𝑅 Δ with Δ 𝐷/ 4 He = −0.108 ± 0.005. This is in contrast with the 3 He/ 4 He flux ratio for which we find Δ 3 He/ 4 He = −0.289 ± 0.003. Above ∼13 GV we find a nearly identical rigidity dependence of the 𝐷 and 𝑝 fluxes with a 𝐷/𝑝 flux ratio of 0.027 ± 0.001. These unexpected observations indicate that cosmic deuterons have a sizable primarylike component. With a method independent of cosmic ray propagation, we obtain the primary component of the 𝐷 flux equal to 9.4 ± 0.5% of the 4 He flux and the secondary component of the 𝐷 flux equal to 58 ± 5% of the 3 He flux.

cosmic ray acceleration↗
NASA NTRS2003

Managing configuration software of ground software applications with glueware

This paper reports on a simple, low-cost effort to streamline the configuration of the uplink software tools. Even though the existing ground system consisted of JPL and custom Cassini software rather than COTS, we chose a glueware approach--reintegrating with wrappers and bridges and adding minimal new functionality.

ground software glueware Cassini↗
NASA NTRS2000

BOREAS TE-12 SSA Shoot Geometry Data

The Boreal Ecosystem-Atmospheric Study (BOREAS) TE-12 (Terrestrial Ecology) team collected shoot geometry data in 1993 and 1994 from aspen, jack pine, and black spruce trees. Collections were made at the Southern Study Area Nipawin Fen Site (SSA FEN), Young Jack Pine (YJP), Old Jack Pine (OJP), Old Aspen (OA), Young Aspen (YA), Mixed Site (MIX), and Old Black Spruce (OBS) sites. A caliper was used to measure shoot and needle lengths and widths. A volume displacement procedure was used to measure the weight of the shoot or twig submerged in water. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Hall, Forrest G.↗
NASA NTRS1994

A Polarimetric Hyperspectral Imaging Sensor

This paper reports recent field test results of a polarimetric hyperspectral imaging prototype sensor using a noncollinear acousto-optic tunable filter as a wavelength sorter and a polarizing beam splitter. The objective of this work is to evaluate the AOTF-PHI technology for a variety of remote sensing applications.

spectral bandpass filter acousto-optic tunable fil↗
NASA NTRS1994

Analysis of AOTF Hyperspectral Imagery

This paper reports results from an analysis of polarimetric hyperspectral imagery collected using a prototype acousto-optic tunable filter (AOTF) instrument in an outdoor environment. Spectra, derivative spectra, and polarization spectra in the image cube form were studied. The issue concerns spectral and polarization signatures of vegetation, contributions due to aerosol, and man-made object detection. The result illustrates potentials of the technology for a variety of remote sensing applications.

acousto-optic↗
NASA NTRS1993

Production and optical constraints of ice tholin from charged particle irradiation of (1:6) C2H6/H2O at 77 K

Fifty separate irradiations of a 6:1 mixture of H2O/C2H6 ice conducted over a 5-month period have yielded sufficient tholin for the determination of its physical constants in the 0.06 to 40 micron range. While the imaginary part of the refractive index k was obtained by transmission measurements on thin-film samples and Kramers-Kronig analysis (KKA), the real part of the refractive index was obtained by KKA and ellipsometry; these data may prove useful in cometary and outer solar system spectrometric interpretation.

Khare, B. N.↗
NASA NTRS1986

Flat-plate solar array project. Volume 4: High-efficiency solar cells

The High Efficiency Solar Cell Task was assigned the objective of understanding and developing high efficiency solar cell devices that would meet the cost and performance goals of the Flat Plate Solar Array (FSA) Project. The need for research dealing with high efficiency devices was considered important because of the role efficiency plays in reducing price per watt of generated energy. The R&D efforts conducted during the 1982 to 1986 period are summarized to provide understanding and control of energy conversion losses associated with crystalline silicon solar cells. New levels of conversion efficiency were demonstrated. Major contributions were made both to the understanding and reduction of bulk and surface losses in solar cells. For example, oxides, nitrides, and polysilicon were all shown to be potentially useful surface passivants. Improvements in measurement techniques were made and Auger coefficients and spectral absorption data were obtained for unique types of silicon sheets. New modelling software was developed including a program to optimize a device design based on input characteristics of a cell.

Leipold, M.↗
NASA NTRS1985

Microgravity changes in heart structure and cyclic-AMP metabolism

The effects of microgravity on cardiac ultrastructure and cyclic AMP metabolism in tissues of rats flown on Spacelab 3 are reported. Light and electron microscope studies of cell structure, measurements of low and high Km phosphodiesterase activity, cyclic AMP-dependent protein kinase activity, and regulatory subunit compartmentation show significant deviations in flight animals when compared to ground controls. The results indicate that some changes have occurred in cellular responses associated with catecholamine receptor interactions and intracellular signal processing.

Philpott, D. E.↗
NASA NTRS1983

Prochloron research

The purpose was to prepare Prochloron photosynthetic membranes for the isolation of the two major chlorophyll-proteins, the P700-chlorophyll a-protein and the light-harvesting chlorophyll a/b-protein, using SDS-polyacrylamide gel electrophoresis. The prepared proteins (purified) were examined for their cross-reactivity to polyclonal antibodies prepared from higher plant proteins. In addition, material was prepared for electron microscopy, and isolation of the DNA for determination of its general complexity (COT analysis) and similarity to barley chloroplast DNA and Anabaena DNA by using restriction-endonuclease analysis. Kleinschmidt spreads of the DNA were in the electron microscope to identify and measure the extent and size of the circlar DNA.

Lewin, R. A.↗
NASA NTRS1983

Prochloron on synaptula

It is reported that, for the first time, Prochloron cells were found associated with an animal other than a colonial ascidian-namely, a synaptid holothurian, Snaptula lamperti. This occurance brings into question the supposedly obligate nature of the association of this problematic algae with didemnids and their allies.

Cheng, L.↗
NASA NTRS1983

Prochloron-ascidian symbioses: Photosynthetic potential and productivity

The chlorophyll content of didemnid asidians with symbiotic algae (Prochloron) from oligotropic tropical marine waters around Palau, Western Carolin Islands is discussed. Several species contain as much chlorophyll per unit dry weight as many herbaceous crop plants and more than do other symbiotic associations such as lichens, green Hydra, etc. Their chlorphyllA/B ratios (3-9) were generally much lighter than those of angiosperms (2-4). Where they abound, Prochloron - ascidian symbiosis could make a major contribution to the productivity, especially in localized areas of tropical marine waters characterized by low nutrient levels and high irradiance.

Lewin, R. A.↗
NASA NTRS1983

Diurnal rhythm in the cell-division frequency of prochloron (prochlorophyta) in nature

Frequencies of cell division stages in suspensions of Prochloron cells, expressed at regular intervals throughout a natural day-night cycle from several colonies of four species of host didemnid, are given. The proportion of dividing cells of Prochloron living symbiotically in colonies of a didemnid, Diplosoma virens, rises from about 4% during the night (20.00-04.00 hrs.) to about 13% in the morning (0,.00-12.00 hrs.), and then falls again in the afternoon. Similiar, though less pronounced, changes were observed among Prochloron cells in two other symbiotic didemnids, Lissoclinum patella and L. voeltzkowi.

Lewin, R. A.↗
NASA NTRS1983

Chlorophyll and carotenoid pigments of prochloron (prochlorophyta)

High-performance liquid chromatography (HPLC) with a gradient-elution technique was utilized to separate and quantify chlorophylls a and b as well as major carotenoid pigments present in freeze-dried preprations of prochloron-didemnid associations and in Prochloron cells separated from host colonies. Results confirm earlier spectrophotometric evidence for both chlorophylls a and b in this prokaryote. Chlorophyll a:b ratios range from 4.14 to 19.71; generally good agreement was found between ratios determined in isolated cell preprations and in symbiotic colonies (in hospite). These values are 1.5 to 5-fold higher than ratios determined in a variety of eukaryotic green plants. The carotenoids in Prochloron are quantitatively and qualitatively similar to those found in various freshwater and marine blue-green algae (cyanopbytes) from high-light environments. However, Prochloron differs from cyanophytes by the absence of myxoxanthophyll and related glycosidic carotenoids. It pigment characteristics are considered sufficiently different from those of cyanophytes to justify its assignment to a separate algal division.

Paerl, H. W.↗