Results for “LIE GROUP” — Page 9

NASA NTRS1990

Intergalactic HI in the NGC5018 group

The cold interstellar and intergalactic medium is in the small group of galaxies whose brightest member is the elliptical galaxy NGC5018. Researchers' attention was first drawn to this galaxy as possibly containing cold interstellar gas by the detection by the Infrared Astronomy Satellite (IRAS) of emission at lambda 60 microns and lambda 100 microns at an intensity of about 1 Jy (Knapp et al. 1989), which is relatively strong for an elliptical (Jura et al. 1987). These data showed that the temperature of the infrared emission is less than 30K and that its likely source is therefore interstellar dust. A preliminary search for neutral hydrogen (HI) emission from this galaxy using the Very Large Array (VLA) showed that there appears to be HI flowing between NGC5018 and the nearby Sc galaxy NGC5022 (Kim et al. 1988). Since NGC5018 has a well-developed system of optical shells (cf. Malin and Carter 1983; Schweizer 1987) this observation suggests that NGC5018 may be in the process of forming its shell system by the merger of a cold stellar system with the elliptical, as suggested by Quinn (1984). Researchers describe follow-up HI observations of improved sensitivity and spatial resolution, and confirm that HI is flowing between NCG5022 and NGC5018, and around NGC5018. The data show, however, that the HI bridge actually connects NGC5022 and another spiral in the group, MCG03-34-013, both spatially and in radial velocity, and that in doing so it flows through and around NGC5018, which lies between the spiral galaxies. This is shown by the total HI map, with the optical positions of the above three galaxies labelled.

Guhathakurta, P.↗

DOE OSTI2026

First-Principles Discovery of Novel LiInP 2 S 6 Polymorphs with Promising Optoelectronic Responses

Recent advances in two-dimensional (2D) van der Waals (vdW) metal thiophosphates have attracted considerable attention due to their promising ionic conductivity, optical characteristics, and tunable physical properties. Within this material family, LiInP 2 S 6 has emerged as an intriguing candidate, not only because of its sensitivity to air and moisture but also due to its suitable band gap within the UV−vis range, enabling potential optoelectronic and photocatalytic applications. In this study, through comprehensive first-principles investigations, we unveil two previously unreported polymorphs of LiInP 2 S 6 in the monoclinic C2/c and trigonal P3̅1c (in-gap) space groups, in addition to examining the experimentally synthesized P3̅1c (in-layer) phase. Our studies identify the C2/c structure as the ground state, lying 9 meV per unit cell lower in energy than the experimentally realized trigonal P3̅1c (in-layer) phase. Further, we systematically examine the elastic, mechanical, thermodynamical, dynamical, electronic, and optical properties of all three polymorphs, confirming their mechanical, thermal, and dynamical stability. Notably, the P3̅1c (in-gap) phase exhibits enhanced stiffness, while the calculated indirect band gaps and strong photon absorption in the UV−vis range (∼3 eV) highlight the potential of the studied LiInP 2 S 6 phases for iontronic devices and optoelectronic applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1972

The Policy Formation Process: A Conceptual Framework for Analysis

A conceptual framework for analysis which is intended to assist both the policy analyst and the policy researcher in their empirical investigations into policy phenomena is developed. It is meant to facilitate understanding of the policy formation process by focusing attention on the basic forces shaping the main features of policy formation as a dynamic social-political-organizational process. The primary contribution of the framework lies in its capability to suggest useful ways of looking at policy formation reality. It provides the analyst and the researcher with a group of indicators which suggest where to look and what to look for when attempting to analyze and understand the mix of forces which energize, maintain, and direct the operation of strategic level policy systems. The framework also highlights interconnections, linkage, and relational patterns between and among important variables. The framework offers an integrated set of conceptual tools which facilitate understanding of and research on the complex and dynamic set of variables which interact in any major strategic level policy formation process.

Fuchs, E. F.↗

NASA NTRS1991

Reluctant glass formers and their applications in lens design

Recently, a group of glasses has been investigated that have high refractive index and low dispersion. These glasses are known as reluctant glass formers and lie in the 'forbidden' region of the conventional glass map. Research is continuing to develop means and techniques to produce usable sizes and optical characteristics. Since these glasses have unusual optical properties, a study was performed to gain an understanding of the impact such glasses could have on optical design and to establish desired baseline optical properties as objectives for the material scientists. Several generic optical configurations were explored to determine if a meaningful improvement could be realized. Study results are presented and discussed to illustrate that a notable enhancement in optical performance is attainable.

Johnson, R. B.↗

NASA NTRS1994

The Fornax-Leo-Sculptor stream revisited

Lynden-Bell first demonstrated that the satellites of the Milky Way appear situated along two great 'streams' in the sky: the 'Magellanic stream' and the 'Fornax-Leo-Sculptor (FLS) stream.' Further exploration of the three-dimensional distribution of Galactic satellites reveals that the recently discovered Sextans and Phoenix dwarf spheroidal galaxies also lie near the plane defined by the FLS galaxies, and therefore strengthens the evidence in favor of the FLS stream. Moreover, a specific group of globular clusters -- those exhibiting the reddest horizontal branches (HBs) among those identified as 'young halo' by Zinn -- appear to populate the FLS stream. As previously demonstrated by Zinn, the spatial distribution of old halo globulars appears to be flattened toward the Galactic plane, and therefore the old halo clusters are typically anti-correlated to the nearly orthogonal FLS stream. A scenario is postulated wherein the Galactic satellites of the FLS stream and the red HB, young halo globular clusters share a common origin in the accretion of a formerly larger, parent satellite galaxy or Searle & Zinn 'fragment.'

Majewski, Steven R.↗

NASA NTRS2010

Sun, the Earth, and Near-Earth Space: A Guide to the Sun-Earth System

In a world of warmth and light and living things we soon forget that we are surrounded by a vast universe that is cold and dark and deadly dangerous, just beyond our door. On a starry night, when we look out into the darkness that lies around us, the view can be misleading in yet another way: for the brightness and sheer number of stars, and their chance groupings into familiar constellations, make them seem much nearer to each other, and to us, that in truth they are. And every one of them--each twinkling, like a diamond in the sky--is a white-hot sun, much like our own. The nearest stars in our own galaxy--the Milky Way-- are more than a million times further away from us than our star, the Sun. We could make a telephone call to the Moon and expect to wait but a few seconds between pieces of a conversation, or but a few hours in calling any planet in our solar system.

Sun↗

NASA NTRS1998

Preparation and Characterization of Fluorescent Derivatives of Lysozyme

Fluorescence is one of the most versatile and powerful tools for the study of macromolecules. However, its use in macromolecular crystal growth studies is hampered by the necessity of preparing fluorescent derivatives where the probe does not markedly affect the crystal packing. Alternatively, one can prepare derivatives of limited utility if it is known that they will not affect the specific goals of a given study. We have prepared a number of fluorescent derivatives of chicken egg white lysozyme, covalently attaching fluorescent probes to two different sites on the protein molecule. The first site is the side chain carboxyl group of ASP 101. Amine containing probes such as lucifer yellow, cascade blue, and 5- (2-aminoethyl) aminonapthalene-l-sulfonic acid (EDANS) have been attached using a carbodiimide coupling procedure. ASP 101 lies within the active site cleft, and it is believed that the probes are "buried" within that cleft. This is supported by the fact that all such derivatives have been found to crystallize, with the crystals being fluorescent. Tetragonal crystals of the lucifer yellow derivative have been found to diffract to at least 1.9 A resolution. X-ray diffraction data has been acquired and we are now working on the structure of this derivative. The second group of derivatives is to the N-terminal amine group. The derivatization reaction is performed by using a succinimidyl ester of the probe to be attached. Fluorescent probes such as pyrene acetic acid, 5-carboxyfluorescein, and Oregon green have been attached to this site. We have had little success in crystallizing these derivatives, probably because this site is part of the contact region between the 43 helix chains. However, these sites do not interfere with formation of the 43 helices and the derivatives are suitable for study of their formation in solution. The derivatives are being characterized by steady state and lifetime fluorescence methods, and the presentation will discuss these results.

Smith, Lori↗

DOE OSTI2024

Stealth dark matter spectrum using Laplacian Heaviside smearing and irreducible representations

We present nonperturbative lattice calculations in the quenched approximation of the low-lying meson and baryon spectrum of the SU(4) gauge theory with fundamental fermion constituents. This theory is one instance of stealth dark matter, a class of strongly coupled theories, where the lowest mass stable baryon is the dark matter candidate. This work constitutes the first milestone in the program to study stealth dark matter self-interactions. Here, we focus on reducing excited state contamination in the single-baryon channel by applying the Laplacian Heaviside method, as well as projecting our baryon operators onto the irreducible representations of the octahedral group. We compare our resulting spectrum to previous work involving Gaussian smeared nonprojected operators and find good agreement with reduced statistical uncertainties. We also present the spectrum of the low-lying odd-parity baryons for the first time.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS2000

Re-Os Systematics in Pallasites and in Group IIIAB High-Ni Iron Meteorites

New data on high Ni-pallasites and IIIAB irons show a large variation in the PGE contents. Samples from different classes of iron meteorites and pallasites lie on a single isochron.

Chen, J. H.↗

NASA NTRS1999

Model Experiments and Model Descriptions

The Second Workshop on Stratospheric Models and Measurements Workshop (M&M II) is the continuation of the effort previously started in the first Workshop (M&M I, Prather and Remsberg [1993]) held in 1992. As originally stated, the aim of M&M is to provide a foundation for establishing the credibility of stratospheric models used in environmental assessments of the ozone response to chlorofluorocarbons, aircraft emissions, and other climate-chemistry interactions. To accomplish this, a set of measurements of the present day atmosphere was selected. The intent was that successful simulations of the set of measurements should become the prerequisite for the acceptance of these models as having a reliable prediction for future ozone behavior. This section is divided into two: model experiment and model descriptions. In the model experiment, participant were given the charge to design a number of experiments that would use observations to test whether models are using the correct mechanisms to simulate the distributions of ozone and other trace gases in the atmosphere. The purpose is closely tied to the needs to reduce the uncertainties in the model predicted responses of stratospheric ozone to perturbations. The specifications for the experiments were sent out to the modeling community in June 1997. Twenty eight modeling groups responded to the requests for input. The first part of this section discusses the different modeling group, along with the experiments performed. Part two of this section, gives brief descriptions of each model as provided by the individual modeling groups.

Jackman, Charles H.↗

NASA NTRS1976

Lunar crater arcs

An analysis has been made of the tendency of large lunar craters to lie along circles. A catalog of the craters at least 50 km in diameter was prepared first, noting position, diameter, rim sharpness and completion, nature of underlying surface, and geological age. The subset of those craters 50-400 km in diameter was then used as input to computer programs which identified each 'family' of four or more craters of selected geological age lying on a circular arc. For comparison, families were also identified for randomized crater models in which the crater spatial density was matched to that on the moon, either overall or separately for mare and highland areas. The observed frequency of lunar arcuate families was statistically highly significantly greater than for the randomized models, for craters classified as either late-pre-Imbrian (Nectarian), middle pre-Imbrian, or early pre-Imbrian, as well as for a number of larger age-classes. The lunar families tend to center in specific areas of the moon; these lie in highlands rather than maria and are different for families of Nectarian craters than for pre-Nectarian. The origin of the arcuate crater groupings is not understood.

Jaffe, L. D.↗

NASA NTRS1986

The origin of dwarf galaxies, cold dark matter, and biased galaxy formation

A reexamination is conducted of the formation of dwarf, diffuse, metal-poor galaxies due to supernova-driven winds, in view of data on the systematic properties of dwarfs in the Local Group and Virgo Cluster. The critical condition for global gas loss as a result of the first burst of star formation is that the virial velocity lie below an approximately 100 km/sec critical value. This leads, as observed, to two distinct classes of galaxies, encompassing the diffuse dwarfs, which primarily originate from typical density perturbations, and the normal, brighter galaxies, including compact dwarfs, which can originate only from the highest density peaks. This furnishes a statistical biasing mechanism for the preferential formation of bright galaxies in denser regions, enhancing high surface brightness galaxies' clustering relative to the diffusive dwarfs.

Dekel, A.↗

NASA NTRS2001

Preparation and Preliminary Characterization of Crystallizing Fluorescent Derivatives of Chicken Egg White Lysozyme

Fluorescence is one of the most versatile and powerful tools for the study of macromolecules. While most proteins are intrinsically fluorescent, working at crystallization concentrations require the use of covalently prepared derivatives added as tracers. This approach requires derivatives that do not markedly affect the crystal packing. We have prepared fluorescent derivatives of chicken egg white lysozyme with probes bound to one of two different sites on the protein molecule. Lucifer yellow and 5-(2-aminoethyl)aminonapthalene-1-sulfonic acid (EDANS) have been attached to the side chain carboxyl of Asp(sup 101) using a carbodiimide coupling procedure. Asp(sup 101) lies within the active site cleft, and it is believed that the probes are "buried" within that cleft. Lucifer yellow and MANS probes with iodoacetamide reactive groups have been bound to His(sup 15), located on the "back side" of the molecule relative to the active site. All the derivatives fluoresce in the solution and the crystalline states. Fluorescence characterization has focused on determination of binding effects on the probe quantum yield, lifetime, absorption and emission spectra, and quenching by added solutes. Quenching studies show that, as postulated, the Asp(sup 101)-bound probes are partially sheltered from the bulk solution by their location within the active site cleft. Probes bound to His(sup 15) have quenching constants about equal to those for the free probes, indicating that this site is highly exposed to the bulk solution.

Sumida, John↗

NASA NTRS2001

Preparation and Preliminary Characterization of Crystallizing Fluorescent Derivatives of Chicken Egg White Lysozyme

Fluorescence is one of the most versatile and powerful tools for the study of macromolecules. While most proteins are intrinsically fluorescent, working at crystallization concentrations require the use of covalently prepared derivatives added as tracers. This approach requires derivatives that do not markedly affect the crystal packing. We have prepared fluorescent derivatives of chicken egg white lysozyme with probes bound to one of two different sites on the protein molecule. Lucifer yellow and 5-(2-aminoethyl)aminonapthalene-i-sulfonic acid (EDANS) have been attached to the side chain carboxyl of Asp(sup 101) using a carbodiimide coupling procedure. Asp(sup 101) lies within the active site cleft, and it is believed that the probes are 'buried' within that cleft. Lucifer yellow and MANS probes with iodoacetamide reactive five groups have been bound to His(sup 15), located on the 'back side' of the molecule relative to the active site. All the derivatives fluoresce in the solution and the crystalline states. Fluorescence characterization has focused on determination of binding effects on the probe quantum yield, lifetime, absorption and emission spectra, and quenching by added solutes. Quenching studies show that, as postulated, the Asp(sup 101)-bound probes are partially sheltered from the bulk solution by their location within the active site cleft. Probes bound to His(sup 15) have quenching constants about equal to those for the free probes, indicating that this site is highly exposed to the bulk solution.

Sumida, John P.↗

NASA NTRS2016

Africa's Megafans and Their Tectonic Setting

Megafans are a really extensive continental sediment bodies, fluvially derived, and fan-shaped in planform. Only those >80 km long were included in this study. Africa's megafans were mapped for purposes of both comprehensive geomorphic description and as a method of mapping by remote sensing large probable fluvial sediment bodies (we exclude sediment bodies deposited in well defined, modern floodplains and coastal deltas). Our criteria included a length dimension of >80 km and maximum width >40 km, partial cone morphology, and a radial drainage pattern. Visible and especially IR imagery were used to identify the features, combined with topographic SRTM data. We identified 99 megafans most of which are unstudied thus far. Their feeder rivers responsible for depositing megafan sediments rise on, and are consequent drainages oriented down the slopes of the swells that have dominated African landscapes since approximately 34 Ma (the high points in Africa's so-called basin-and-swell topography [1]). Most megafans (66%) have developed along these consequent rivers relatively near the swell cores, oriented radially away from the swells. The vast basins between the swells provide accommodation for megafan sediment wedges. Although clearly visible remotely, most megafans are inactive as a result of incision by the feeder river (which then no longer operates on the fan surface). Two tectonic settings control the location of Africa's megafans, 66% on swell flanks, and 33% related to rifts. (i) Swell flanks Most megafans are apexed relatively near the core of the parent swell, and are often clustered in groups: e.g., six on the west and north flanks of the Hoggar Swell (Algeria), seven on the north and south flanks of the Tibesti Swell (Libya-Chad borderlands), twelve on the west flank of the Ethiopian Swell, four on the east flank of the East African Swell (Kenya), Africa's largest, and eight around Angola's Bié Swell (western Zambia, northern Namibia). A cluster of possible fans lies on the western margin of the Congo Basin (Mayombe Swell), and on the coastal slopes of the Namibia Swell. Sheer size may have militated aginst the recognition of many megafans: the largest in the Sahara are the Teghahart (378 km, Hoggar Swell, Algeria), and the Wadi Albalata (340 km, Uweinat Swell, Egypt). In southern Africa the largest are the Cubango (320 km, Bié Swell, Angola/ Namibia), and the Limpopo (230 km, Mozambique). (ii) Rift zones (a) Steer's horns basins-wide depressions centered on rifts. The largest contiguous group (n=14) developed in a steer's-horns basin occupies the wide Muglad depression (200-350 km, South Sudan). Four rift-related megafans lie SE of Lake Chad (Chad). Nine megafans occupy the complex Anza Rift in Kenya/South Somalia. The Salamat megafan (Chad), is unusual because it oriented parallel with the linked Salamat, Doseo and Doba rift axes, and is consequently one of the longest in Africa (465 km). (b) Rift depressions sensu stricto. Most rifts are too narrow to provide a transverse dimension large enough to accommodate megafans. Although well-known, the Okavango Rift (NW Botswana, NE Namibia) is unique in Africa in hosting three megafans within identifiable faulted margins. The Nile megafan is Africa's largest (476 km) and comprises the vast Sudd wetland (South Sudan). An explanation for its remarkable size may be its location in a depression at the junction of two conducive tectonic zones, the East African Swell margin and the Muglad steer's-horns depression. Discharge of the River Nile, the largest in the region, has allowed the Nile megafan to outcompete neighboring megafans for space.

Wilkinson, M. J.↗

NASA NTRS1995

Galactic oscillator symmetry

Riemann ellipsoids model rotating galaxies when the galactic velocity field is a linear function of the Cartesian coordinates of the galactic masses. In nuclear physics, the kinetic energy in the linear velocity field approximation is known as the collective kinetic energy. But, the linear approximation neglects intrinsic degrees of freedom associated with nonlinear velocity fields. To remove this limitation, the theory of symplectic dynamical symmetry is developed for classical systems. A classical phase space for a self-gravitating symplectic system is a co-adjoint orbit of the noncompact group SP(3,R). The degenerate co-adjoint orbit is the 12 dimensional homogeneous space Sp(3,R)/U(3), where the maximal compact subgroup U(3) is the symmetry group of the harmonic oscillator. The Hamiltonian equations of motion on each orbit form a Lax system X = (X,F), where X and F are elements of the symplectic Lie algebra. The elements of the matrix X are the generators of the symplectic Lie algebra, viz., the one-body collective quadratic functions of the positions and momenta of the galactic masses. The matrix F is composed from the self-gravitating potential energy, the angular velocity, and the hydostatic pressure. Solutions to the hamiltonian dynamical system on Sp(3,R)/U(3) are given by symplectic isospectral deformations. The Casimirs of Sp(3,R), equal to the traces of powers of X, are conserved quantities.

Rosensteel, George↗

NASA NTRS2000

Preparation and Characterization of Fluorescent Derivatives of Chicken Egg White Lysozyme

Fluorescence is one of the most versatile and powerful tools for the study of macromolecules. While most proteins are intrinsically fluorescent, working at crystallization concentrations require the use of covalently prepared derivatives added as tracers. This approach requires derivatives that do not markedly affect the crystal packing. We have prepared a number of fluorescent derivatives of chicken egg white lysozyme with probes bound to one of two different sites on the protein molecule. Lucifer yellow, cascade blue, and 5-(2-aminoethyl)aminonapthalene-l-sulfonic acid (EDANS) have been attached to the side chain carboxyl of asp101 using a carbodiimide coupling procedure. asp101 lies within the active site cleft, and it is believed that the probes are at least partially "buried" within that cleft. Lucifer yellow and MANS probes with iodoacetamide reactive groups have been bound to hisl5, located on the "back side" of the molecule relative to the active site. The fluorescently labeled protein is readily purified from the starting material by cation exchange chromatography. All the derivatives fluoresce in both the solution and the crystalline states. Fluorescence characterization has focused on determining the bound probe quantum yields, lifetimes, absorption and emission spectra, and quenching by added solutes in comparison to the free probe. No appreciable changes are found in the lifetimes of any of the probes except for cascade blue, where Tau(sub free) = 3.52 ns vrs Tau(sub bound) = 2.8 ns. Spectral shifts are found in most cases. Particularly strong quenching upon binding is found in the case of the cascade blue derivative, likely due to probe interactions with the active site cleft. While none of the asp101 bound probes are well quenched by commonly employed solutes, such as potassium and sodium iodide, acrylamide, primuline, the chloride salts of manganese, cesium, and cobalt, trifluoroacetamide, trichloroethanol, and thallium iodide, in those cases where quenching is observed the bound probe is less efficiently quenched relative to the free probe. This indicates that the bound probes are less accessible to the bulk solution, an expected finding for attachment within the active site cleft. Attempts have been made to bind other molecules to these sites, with varying success. Interestingly, all three probes contain one or more sulfonate ((Ar-S03)-) groups. We have not been successful in binding analogous probes without sulfate groups such as pyrene, or with derivatized sulfonate groups such as dansyl type probes, analogous to MANS but where the sulfonate group is derivatized, Ar-S02-N2C2H7. None of the probes is rigidly bound to the protein, i.e., they all have a probe motion superimposed on that of the protein.

Sumida, John↗

DOE OSTI2026

Nuclear Structure and Decay Data for A=169 Isobars

Experimental data pertaining to all nuclei with mass number A=169 (Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt) have been evaluated. Level schemes from both radioactive decay and reaction studies are presented, along with associated tables of experimental data and adopted properties for levels and γ rays. The present evaluation for A=169 supersedes the 2008 evaluation, 2008Ba31, by C.M. Baglin. A few highlights of this evaluation: More extensive work on ε decay from 169W is needed and new experimental work will be required to resolve a discrepancy between the J π values deduced for a 180-keV level in 169Ta based on extensive band structure from (HI,xnγ) work (J π =1/2−) and TDPAD measurements (J=5/2). Low lying states of 169Os were studied via fine structure of 173Pt α decay in 2014ThZZ. The Eαs feeding the g.s. of 169Os in 2008Ba31 are separated well into two consistent groups to feed the g.s. and the newly proposed state at 34.84 keV. Based on the studies of 2014ThZZ and 2021Zh52, the g.s. spin-parity assignment of 169Os has been proposed to be (7/2−) from (5/2−). The 169Ir g.s. half-life and alpha emission branching reported in 2012Th13 from 173Au α decay measurements are preferred over the values in 2005Sc22. The reported half-life value in 2005Sc22 for 169Ir g.s. is discrepant and the research work was carried out in the same lab of 2012Th13.

Basunia, M Shamsuzzoha↗